Tagged: physicsworld.com Toggle Comment Threads | Keyboard Shortcuts

  • richardmitnick 2:22 pm on November 19, 2021 Permalink | Reply
    Tags: "Universal photonic quantum processor sets new size record", , , physicsworld.com   

    From physicsworld.com : “Universal photonic quantum processor sets new size record” 

    From physicsworld.com

    19 Nov 2021
    Soroush Khademi

    1
    Click and reconnect: Researchers reconfiguring the photonic quantum processor using a personal computer. Courtesy: QuiX Quantum.

    Scientists from QuiX Quantum and the adaptive quantum optics group at The University of Twente [ Universiteit Twente] (NL) have built the largest universal photonic quantum processor to date. The processor works by applying adjustable phase shifts to the optical signals going through its 12 modes and then merging the signals in adjustable proportions. The precision of its fabrication allows single photons to interfere as they propagate, making the processor capable of quantum operations – albeit not yet at a level that could outperform classical machines.

    The new device takes in 12 input optical signals, processes them and outputs the result optically, all at the standard telecommunication wavelength. The device’s photonic configuration – that is, the phase shifts and the proportions of each signal being merged – determines the nature of the processing task, and users can reconfigure this by connecting it to an ordinary personal computer. In this way, the device can be programmed to perform any processing task realizable by a specific set of optical merging and phase shifting steps.

    The photonic processor and its delicate engineering

    To implement these steps, the device uses a series of optical components known as tuneable phase shifters and tuneable beam mergers. The latter consists of two beam mergers that combine pairs of input beams in equal proportions, plus a tuneable phase shifter. The key to making the system reconfigurable is thus to have full control over the phase shifters within the processor’s photonic circuit, where each of the phase shifters is a heater that induces a very well-tuned and specific change in the effective path length of the passing optical signals via a phenomenon known as the thermo-optic effect.

    By satisfying a list of technical demands for the 12 modes, from high-quality microfabrication of the photonic waveguides (optical paths) to providing fast mechanisms for stabilising the temperature of the photonic circuit, the team set a record for the number of on-chip modes with a programmable configuration that can process quantum optical inputs (such as single-photon ones). In other words, the probability of losing a single photon inside the processor is low, and furthermore, identical single photons injected to different inputs of the processor do not appear different at the output. These results have been published in Materials for Quantum Technology.

    Characterizing the processor

    To quantify the processor’s reconfigurability, the team changed the processor’s configuration and tested it using laser light (providing classical inputs) and photodetectors. By comparing the configuration obtained in this test with the desired one, they found the “amplitude fidelity” – a measure of similarity between different configurations – was about 93 percent, stretching to 98 percent for some target configurations.

    3
    Well connected: A close-up of the processor’s core, including the photonic chip at its heart. Courtesy: QuiX Quantum.

    The researchers also evaluated the processor’s optical loss with the same input-output setup. They found that this was as low as 17 percent on average, although a significant amount of additional loss occurs at the input and output connectors. Finally, they characterized the processor’s ability to preserve the identical nature of single photons. The team did this by injecting two identical single photons simultaneously and observing a phenomenon known as Hong–Ou–Mandel interference at the single-photon detectors connected to the outputs. They found that the on-chip interference has the same visibility as the off-chip interference of the two injected single photons – meaning that single photons at the chip’s output are as identical as they were at the input.

    Next steps

    Although this processor could, in principle, form the core of an efficient universal optical quantum computer, fabricating the other equipment needed for such a computer would be far more technically demanding. Nevertheless, there is one known computational problem for which a processor of this nature can outperform classical computers (a situation known as “quantum supremacy” or “quantum primacy”) without fancier equipment. This problem is known as boson sampling and it involves predicting the output of the processor itself in a special scenario.

    To understand how boson sampling works, consider what happens if we inject some identical single photons into the processor. The photons propagate through the processor and appear at the outputs where they are detected by single-photon detectors. But which detectors will find a photon? This question is inherently impossible to answer. Even if the input and the configuration is exactly the same, different detectors will be activated at the output each time we run the experiment. Nonetheless, if we run the experiment many times, we can prepare statistical samples implying the probability of different detection events. The interesting point here, from a computational point of view, is that for a big enough number of modes, classical computers cannot efficiently prepare these statistical samples (or calculate the probability distribution function for the detection events).

    In 2020, researchers led by Jian-Wei Pan and Chao-Yang Lu of The University of Science and Technology of China [电子科技大学](CN) demonstrated quantum advantage for a similar problem using their own photonic device. The USTC team’s device differs from the processor described in this study in one critical respect, however. “The authors of the 2020 paper use a static device for their proof-of-principle experiment,” explains Jelmer Renema, a physicist at QuiX Quantum and the University of Twente. “We build on that result and realize full reconfigurability.”

    Renema goes on to explain that while the system he and his colleagues developed can run boson sampling experiments, “quantum supremacy doesn’t arise with 12 modes”. Nevertheless, he and other members of the research group, which is led by Pepijn Pinkse, are developing the processor. “We are working on improving the specifications of the system like reducing the optical loss, and furthermore, on increasing the number of modes. We expect to unveil a processor with 50 modes in 2022,” Renema tells Physics World.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    http://www.stemedcoalition.org/”>Stem Education Coalition

    physicsworld is a publication of the Institute of Physics. The Institute of Physics is a leading scientific society. We are a charitable organisation with a worldwide membership of more than 50,000, working together to advance physics education, research and application.

    We engage with policymakers and the general public to develop awareness and understanding of the value of physics and, through IOP Publishing, we are world leaders in professional scientific communications.

     
  • richardmitnick 2:40 pm on November 14, 2021 Permalink | Reply
    Tags: "Laser-free trapping of heavy molecules opens an alternative route to new physics", , , , , physicsworld.com   

    From physicsworld.com : “Laser-free trapping of heavy molecules opens an alternative route to new physics” 

    From physicsworld.com

    14 Nov 2021
    Martijn Boerkamp

    1
    Gotcha: A cartoon illustrating how molecules of strontium fluoride are slowed and trapped within a Stark decelerator, then interrogated by a laser beam. Courtesy: Jasmeet Jassal and Parul Aggarwal.

    The quest for physics outside the Standard Model often takes place at major accelerator facilities like CERN’s Large Hadron Collider or huge underground detectors for neutrinos, dark matter and other exotic particles. Researchers in the Netherlands have now opened an alternative front in this quest by developing a new laboratory-scale technique for trapping heavy neutral molecules. Such molecules are considered ideal candidates for detecting beyond-the-Standard-Model asymmetries in the electron’s electric dipole moment (eEDM), but previous methods were not capable of confining them. The technique therefore gives physicists a fresh set of tools for finding new physics.

    Standard methods used in eEDM searches involve performing high-precision spectroscopy on atoms or molecules that are first slowed and then trapped with lasers or electric fields for the duration of the measurement. The problem is that finding new physics may require trapping molecules that are too heavy to be confined with lasers. Electric fields, for their part, can only trap heavy ions, rather than neutral atoms or molecules.

    It’s a trap!

    A new method can now be added to this list thanks to researchers at The University of Groningen [Rijksuniversiteit Groningen] (NL), who developed it in collaboration with colleagues at The Free University of Amsterdam [Vrije Universiteit Amsterdam] (NL) and Nikhef-National Institute for Subatomic Physics(NL), the Dutch particle physics institute. The researchers begin by creating molecules of strontium fluoride (SrF) via a chemical reaction that takes place inside a cryogenic gas at a temperature of around 20 K. These molecules have initial velocities of 190 m/s, compared to around 500 m/s at room temperature.

    The molecules then enter a 4.5-metre-long device called a Stark decelerator in which alternating electric fields act to slow and then stop them. The SrF molecules remain trapped for 50 ms, after which the researchers analyse them using a separate laser-induced fluorescence detection system. Such measurements reveal fundamental properties of the electron, including the eEDM, that can then be checked for any asymmetry.

    The heavier the better

    These SrF molecules are around three times heavier than other molecules previously trapped using similar techniques, notes Steven Hoekstra, a physicist at Groningen and lead investigator on the research. “Our next step is to trap even heavier molecules, such as barium fluoride (BaF), which is one-and-a-half times heavier than SrF,” he says. “This type of molecule is even better for measurements on the electron dipole. Basically, the heavier [the molecule], the better these measurements will become.”

    Trapping heavy molecules has other applications beyond eEDM measurements. One example might be to study collisions between molecules at low energies, under conditions similar to those found in space. Measurements on slowly moving molecules could also yield deeper insights into the quantum nature of their interactions. At high enough densities, the molecules’ so-called dipole-dipole interaction, which depends on their orientation relative to each other, makes a big difference in how they interact. These types of measurements offer opportunities that are not possible with stationary atoms, which do not interact in this way.

    Complex and chiral

    As a next step, Hoekstra says that he and his colleagues plan to increase the sensitivity of their measurement setup by upping the intensity of their molecular beam. “We are also thinking of trapping more complex molecules, such as BaOH, or BaOCH3,” he tells Physics World. “Additionally, we could use our technique to study asymmetries within chiral molecules: those that have a left and right-handed version.”

    Ben Sauer, a physicist at Imperial College London (UK) who was not involved in the current study, describes the result as the culmination of about 20 years of research on molecule deceleration. He predicts that it will have a big impact on precision measurements of the eEDM, where the resolution of the measurement is directly proportional to the time available to interrogate the molecules. As for wider applications, Sauer says: “I can see it being applied to some special cases. I think the limit is that there is a lot more interest in light molecules than heavy ones, since most of chemistry takes place at the top of the periodic table. But it is really good for physics investigations.”

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    http://www.stemedcoalition.org/”>Stem Education Coalition

    physicsworld is a publication of the Institute of Physics. The Institute of Physics is a leading scientific society. We are a charitable organisation with a worldwide membership of more than 50,000, working together to advance physics education, research and application.

    We engage with policymakers and the general public to develop awareness and understanding of the value of physics and, through IOP Publishing, we are world leaders in professional scientific communications.

     
  • richardmitnick 5:06 pm on February 11, 2021 Permalink | Reply
    Tags: "Dark-matter detector result is consistent with previous hint of exotic particles", , , LUX-ZEPLIN detector, , PandaX-II particle detector, physicsworld.com, The events reported in 2020 involved electron rather than nuclear recoils., , XENON1T Dark Matter experiment   

    From physicsworld.com: “Dark-matter detector result is consistent with previous hint of exotic particles” 

    From physicsworld.com

    09 Feb 2021
    Edwin Cartlidge

    PandaX II Dark Matter experiment at Jin-ping Underground Laboratory (CJPL) in Sichuan, China.

    New data from the PandaX-II particle detector in China leave open the possibility that the XENON1T experiment in Italy has found evidence of new physics.

    XENON1T at Gran Sasso LABORATORI NAZIONALI del GRAN SASSO, located in the Abruzzo region of central Italy.

    In June 2020 researchers working on XENON1T announced the detection of around 50 events above background levels and concluded that hypothetical solar axions or very magnetic neutrinos might be responsible. The new results from PandaX-II are consistent with these hypotheses but further work will be needed to settle the issue.

    XENONIT was built to hunt for a type of dark matter known as weakly interacting massive particles (WIMPs). Housed under a mountain at Italy’s Gran Sasso National Laboratory, it contained 3.5 tonne of liquid xenon and operated between 2016-2018. Like other experiments of its type, it was designed to pick up the tiny flashes of light generated when WIMPs in the “halo” of dark matter thought to envelop the Milky Way collide with xenon nuclei.

    The events reported in 2020 involved electron, rather than nuclear, recoils. Elena Aprile of Columbia University in the US and colleagues reported 53±15 such recoils at low energy that they could not tie to other identifiable sources of background (these events themselves being considered noise in the search for WIMPs). Careful not to claim any discovery, they instead laid out several possible explanations for the observation.

    Two novelties

    These explanations included two novelties associated with particles arriving from the Sun – either hypothetical particles known as axions (postulated originally to fix a problem with the strong nuclear force) or neutrinos with a greater magnetic moment than previously observed. Another possibility, they said, was “bosonic dark matter”, which would be absorbed, rather than scattered, by the xenon nuclei and cause electrons to be emitted.

    However, as Aprile and colleagues pointed out, the events could also have had a more mundane explanation – the beta decay of tritium nuclei. This would come about when the few neutrons liberated from surrounding rock by cosmic rays create tritium by splitting xenon nuclei. Unlike other background processes, this remains a nuisance since its extent is not possible to estimate reliably.

    Aprile and colleagues calculated that the tritium could account for the excess events with a statistical significance of 3.2σ – compared to 3.4σ, 3.2σ and 3.0σ for solar axions, neutrino magnetism and bosonic dark matter, respectively.

    Dimmer white dwarfs

    Despite their cautious presentation, these results caught the attention of both the public and fellow physicists. For example, theorists put forward several ways to overcome one obvious sticking point with the Sun-based hypotheses – that the flux of the particles involved would make white dwarf stars dimmer than they appear.

    In the latest work, Jianglai Liu of Shanghai Jiao Tong University (CN) and colleagues did an independent experimental check on the XENON1T results using the PandaX-II detector in the China Jinping Underground Laboratory in Sichuan, south-western China. Although PandaX-II contains just over half a tonne of xenon, the researchers ran their experiment for longer and acquired nearly half the data as their XENON1T counterparts.

    The Chinese group had the advantage of being able to better characterize their background spectra, thanks to direct measurement or calibration. In part, this was done by twice injecting methane with one of its hydrogen atoms replaced by tritium into the target. With the two injections carried out three years apart, they say they were able to measure the energy spectrum of the tritium contamination within the experiment.

    By in effect subtracting the background spectra of tritium, krypton and radon, the researchers were able to quantify any signals from putative solar axions or a high neutrino magnetic moment – the two theoretical possibilities that Liu says the group used as a “benchmark” in their work. As they report in Chinese Physics Letters, they found that the remaining electron recoils were in fact consistent with the excess events seen by XENON1T. However, they could not fully endorse the earlier result given, they say, that their data were also consistent with a “background-only hypothesis”.

    Detector upgrades

    To try and establish whether some new physical process really has been observed, the Chinese researchers are increasing their detector mass to 6 tonne – meaning a sensitive target of 4 tonne – while lowering background rates. The upgraded detector is called PandaX-4T and should start taking data this year. Also coming online are an upgraded 8.3 tonne “XENONnT” as well as the 10 tonne LUX-ZEPLIN detector currently being installed in the Sanford Underground Research Facility in South Dakota, US.

    SURF-Sanford Underground Research Facility, Lead, South Dakota, USA.


    LUX-ZEPLIN LBNL xenon detector at SURF. Credit: Matt Kapust.

    According to Liu, the new measurements should yield a verdict soon. “A year of low background data taking from PandaX-4T would be able to offer a definitive answer to the XENON1T excess,” he says, although he adds that it remains to be seen just how low they can make the background.

    One group already has an explanation for the XENON1T excess [Physical Review D] – and it does not rely on exotic new physics. Matthew Szydagis, Cecilia Levy and colleagues at the State University of New York at Albany used what is known as the noble element simulation technique to model background interactions within the Gran Sasso detector and found that around 30 decays of the isotope argon-37 would generate the observed excess.

    Levy says that their hypothesis could be investigated by carrying out a thorough calibration of the XENON detector, adding that her group does not know where the argon might come from. Beyond that, she agrees that the observed excess should be scrutinized by the new round of larger experiments. “If it is due to a new particle, it should predictably scale with the more massive detectors,” she says, “and a signal should be clear.”

    Levy says that their hypothesis could be investigated by carrying out a thorough calibration of the XENON detector, adding that her group does not know where the argon might come from. Beyond that, she agrees that the observed excess should be scrutinized by the new round of larger experiments. “If it is due to a new particle, it should predictably scale with the more massive detectors,” she says, “and a signal should be clear.”

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.


    Stem Education Coalition

    PhysicsWorld is a publication of the Institute of Physics. The Institute of Physics is a leading scientific society. We are a charitable organisation with a worldwide membership of more than 50,000, working together to advance physics education, research and application.

    We engage with policymakers and the general public to develop awareness and understanding of the value of physics and, through IOP Publishing, we are world leaders in professional scientific communications.
    IOP Institute of Physics

     
  • richardmitnick 10:56 pm on February 1, 2021 Permalink | Reply
    Tags: "Tiny particles produce huge photon avalanches", , Avalanching nanoparticles might be used to create an optical imaging system with a resolution of just 70 nm., “Perfect photostability”, , , Concentration quenching, , , , Photon avalanching, physicsworld.com, Upconversion   

    From physicsworld.com: “Tiny particles produce huge photon avalanches” 

    From physicsworld.com

    21 Jan 2021 [Just now in social media.]
    Isabelle Dumé

    1
    The chain-reaction process that underlies photon avalanching. Credit: Mikołaj Łukaszewicz/Polish Academy of Sciences.

    Researchers in the US, Poland and Korea have observed photon avalanching – a chain-reaction-like process in which the absorption of a single photon triggers the emission of many – in tiny crystals just 25–30 nm in diameter. This highly nonlinear phenomenon had previously only been seen in bulk materials, and team leader James Schuck says that replicating it in nanoparticles could lead to “revolutionary new applications” in imaging, sensing and light detection.

    Photon avalanching involves a process known as upconversion, whereby the energy of the emitted photons is higher than the energy of the photons that triggered the avalanche. Materials based on lanthanides (chemical elements with atomic numbers between 57 and 71) can support this process in part because their internal atomic structure enables them to store energy for long periods of time. Even so, achieving photon avalanching in lanthanide (Ln) systems is difficult because high concentrations of Ln ions are needed to keep the avalanche going, and the relatively large volume of material required has previously restricted applications.

    Add more lanthanide

    In the latest work, Schuck and colleagues at Columbia University, together with collaborators at Lawrence Berkeley National Laboratory, the Polish Academy of Sciences and Sungkyunkwan University, observed photon avalanching in Ln nanocrystals after exciting them with a laser at near-infrared wavelengths of either 1064 or 1450 nm. The crystals are based on sodium yttrium fluoride (NaYF4) in which 8% of the yttrium ions have been replaced with thulium. This doping fraction is much higher than the 0.2–1% typically found in previous work on photon avalanching.

    Schuck and colleagues found that in their best-performing devices, the intensity of the upconverted emission from their doped nanocrystals scales with the 26th power of the intensity of the exciting lasers – meaning that a 10% change in incident light produces more than a 1000% change in emitted light. This extreme nonlinearity far exceeds previously reported responses for Ln crystals and is not possible in other nonlinear optical materials.

    And that’s not all. Co-team leader Arthur Bednarkiewicz tells Physics World that an effect that occurs due to a phenomenon called concentration quenching, and that is usually detrimental in upconverting lanthanide-based luminescent materials, appears in this material as a positive chain reaction, similar to optical gain. It thus enables photon avalanching.

    Unprecedented nonlinear response

    According to the researchers, the unprecedented nonlinear response they observed means that avalanching nanoparticles might be used to create an optical imaging system with a resolution of just 70 nm. This would be well below the diffraction limit, which dictates that features smaller than about half the wavelength of the illuminating light cannot be resolved.

    “In such an application, the particles would effectively be employed as luminescent probes and the technique could work using a simple scanning confocal microscope,” says Changhwan Lee, the study’s lead author and a member of Schuck’s group.

    Bednarkiewicz adds that the “perfect photostability” of the photon avalanching nanoparticles gives them an advantage over alternative probe particles such as organic dyes or fluorescent proteins. Whereas the fluorescence from these other materials tends to fade away under prolonged illumination, Bednarkiewicz says that emissions from the nanoparticles “can last almost infinitely and may enable long-term sub-diffraction observations.”

    The nanoparticles do have some drawbacks. At 25 nm in diameter, they are larger than the 3 mm organic fluorophores routinely employed in biological sensing applications. Their surface also needs to be functionalized (that is, it needs to have certain chemical groups incorporated to promote desired reactions) before they can sense specific biological molecules. A further drawback is that the nanoparticles emit just a single colour of light, and the avalanching process has a relatively long onset time (from tens to hundreds of milliseconds). However, Schuck and colleagues say that – as with any new technology – further optimization is possible, and some of these drawbacks may be overcome in later work.

    For now, the researchers are focusing on ways to use the nonlinear behaviour they have observed for biological and environmental sensing – for example, to detect pathogens such as viruses, bacteria and fungi in biological fluids, blood or tissue. Other possible uses might include sensing changes in temperature, pressure and humidity.

    Bednarkiewicz adds that the photon avalanching nanoparticles may also find applications more broadly, in areas ranging from mid infrared photon detection and nanolasers to optical neuromorphic computing and optogenetics. “Our present and past studies will certainly be of interest to the scientific luminescence community since they redefine the fundamental concepts and requirements for achieving photon avalanching at the nanoscale,” he says.

    The research is detailed in Nature.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.


    Stem Education Coalition

    PhysicsWorld is a publication of the Institute of Physics. The Institute of Physics is a leading scientific society. We are a charitable organisation with a worldwide membership of more than 50,000, working together to advance physics education, research and application.

    We engage with policymakers and the general public to develop awareness and understanding of the value of physics and, through IOP Publishing, we are world leaders in professional scientific communications.
    IOP Institute of Physics

     
  • richardmitnick 10:07 am on January 29, 2021 Permalink | Reply
    Tags: "Cosmic-ray detector might have spotted nuggets of dark matter", An adaptation of the idea of strange matter put forward by Edward Witten in 1984., , , “Axion quark nuggets”, , , Hypothetical bundles of antiquarks (or quarks) wrapped inside axions that would reveal their presence when passing through dense regions of the universe such as stars and planets., , physicsworld.com, The Pauli exclusion principle puts forward dense stable entities known as "stranglets".   

    From physicsworld.com: “Cosmic-ray detector might have spotted nuggets of dark matter” 

    From physicsworld.com

    21 Jan 2021
    Edwin Cartlidge

    A series of mysterious events recorded by a cosmic-ray observatory a decade ago could be the signature of an unusual form of dark matter called “axion quark nuggets” – according to Ariel Zhitnitsky of the University of British Columbia in Canada. These nuggets are hypothetical bundles of antiquarks (or quarks) wrapped inside a layer of axions that would only reveal their presence when passing through dense regions of the universe such as stars and planets.

    Middle Drum facility of the Telescope Array Observatory in Utah USA.

    Zhitnitsky proposed axion quark nuggets in 2003 to explain a property of dark matter that otherwise requires artificial tuning of certain physical parameters – the fact that the densities of dark matter and visible matter in the universe are very nearly the same, when they could in principle be completely different.

    Axion quark nuggets are an adaptation of the idea of strange matter, put forward by Edward Witten in 1984. Particles containing up, down and strange quarks are usually unstable and decay rapidly, but the Pauli exclusion principle leaves open the possibility that a large enough number of such quarks could create dense stable entities known as stranglets – since more of the quarks would occupy lower energy states than is the case in normal matter containing only up and down quarks.

    Encased in axions

    Zhitnitsky built on this by encasing these particles with a layer of axions. Axions are hypothetical particles postulated in the late 1970s to ensure that neutrons could be described in terms of the strong force without breaking charge-parity (CP) symmetry. Later, axions became a candidate for Dark Matter. In the case of axion quark nuggets, they would enclose dark matter made up of quarks rather than forming the dark matter themselves.

    The idea is that the universe would contain equal quantities of matter and antimatter at all times. Early on in cosmic history, CP-violating axions would have led to the creation of more nuggets containing antiquarks than those containing quarks. Conversely, there would have been more quarks available for nucleosynthesis than there were antiquarks. The net result would be a visible universe dominated by quark matter while most of the mass inside nuggets – the dark matter – would consist of antiquarks.

    With the density of nuclear matter, these nuggets could have macroscopic masses — perhaps about 10 g — while measuring less than a thousandth of a millimetre across. They would interact extremely weakly with other matter and in the rarified environment of deep space would remain almost entirely inert. Only in the presence of more dense matter, such as at the centre of galaxies or in planetary atmospheres, could they reveal their presence.

    Anomalous bursts

    According to Zhitnitsky, the Telescope Array in Utah, US, might have seen such interactions.

    Telescope Array project is an international collaboration involving research and educational institutions in Japan, The United States, Russia, South Korea, and Belgium. The experiment is designed to observe air showers induced by ultra-high-energy cosmic ray using a combination of ground array and air-fluorescence techniques. It is located in the high desert in Millard County, Utah, United States, at about 1,400 meters (4,600 ft) above sea level.

    The observatory, run by an international collaboration, uses hundreds of scintillation detectors spread out over nearly 700 km2 to detect the air showers produced when very high-energy cosmic rays interact with nuclei in the Earth’s atmosphere. However, a small part of the data collected by the array between 2008 and 2013 appears anomalous.

    In 2017, the collaboration reported having observed what it described as 10 short bursts of detections that looked different to normal cosmic-ray air showers. It calculated that there was less than a one in 10,000 chance that these bursts, involving the recording of at least three microsecond-long air shower events within a millisecond, could have been due to the random coincidence of individual air showers. What is more, all of those events took place during thunderstorms – the bursts being strongly correlated with lightning strikes in both time and space.

    In a paper accepted for publication in Journal of Physics G, Zhitnitsky explains that these events can be very naturally explained by axion quark nuggets. He says that some of the antiquarks inside nuggets streaming in from outer space would annihilate with atmospheric quarks, generating a range of particles including positrons. He argues that is only when the nuggets pass through the strong electric fields beneath thunderclouds that these positrons would be liberated in sufficient quantities and then accelerated to the high energies that allow them to travel several kilometres through the atmosphere and into the detectors on the ground.

    As to why the nuggets lead to clusters of detections, he says that the thunderclouds’ electric fields fluctuate continuously. In other words, a nugget must pass through a region of the field aligned with the detector array to yield detectable positrons. From other regions there will be no signal.

    Lower-altitude origins

    In his paper, Zhitnitsky lists several other characteristics of the bursts that he claims point to their being generated by axion quark nuggets. These include the fact that the bursts originate at much lower altitudes than conventional cosmic-ray showers. In addition, he says, the measured energies of the individual events are five to six orders of magnitude higher than would be expected from their rates – given that more energetic cosmic rays tend to be rarer.

    Beyond the anomalies seen by the Telescope Array, Zhitnitsky argues that a range of other astrophysical and experimental data also point to this type of nugget. These include a very pronounced, but much debated seasonal variation in events recorded by the DAMA/LIBRA detector in the Gran Sasso National Laboratory in Italy – which he reckons could be due (indirectly) to the nuggets rather than weakly interacting massive particles.

    DAMA LIBRA Dark Matter Experiment, 1.5 km beneath Italy’s Gran Sasso mountain located in the Abruzzo region of central Italy.

    Establishing whether these particles really are responsible for the strange-looking air showers should be relatively straight forward, he reckons. For one thing, he says, tens of kilometres of optical fibre could be used to try and pick up the acoustic and seismic signals that would accompany any incoming nuggets. Another tell-tale sign would be a very short radio pulse with a frequency of up to a few hundred megahertz that would be generated alongside the accelerated positrons.

    Others, however, doubt that the Telescope Array has seen axion quark nuggets. Pace VanDevender, who leads the MQN Collaboration also investigating quark-nugget dark matter, reckons that the positrons would be annihilated long before they could reach the detectors on the ground – estimating their range in the atmosphere to be about 1 mm rather than several kilometers. He thinks that seismic detectors could potentially pick up a signal from nuggets reaching Earth but cautions that event rates “will need to be carefully calculated” before setting up an array of such sensors.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.


    Stem Education Coalition

    PhysicsWorld is a publication of the Institute of Physics. The Institute of Physics is a leading scientific society. We are a charitable organisation with a worldwide membership of more than 50,000, working together to advance physics education, research and application.

    We engage with policymakers and the general public to develop awareness and understanding of the value of physics and, through IOP Publishing, we are world leaders in professional scientific communications.
    IOP Institute of Physics

     
  • richardmitnick 1:14 pm on January 8, 2021 Permalink | Reply
    Tags: "Radio telescopes could give us a new view of gravitational waves", ARCADE2 was a balloon experiment flown over Texas., , , , , physicsworld.com, , The EDGES radio telescope sheds light on primordial gravitational waves.   

    From physicsworld.com: “Radio telescopes could give us a new view of gravitational waves” 

    From physicsworld.com

    05 Jan 2021
    Edwin Cartlidge

    EDGES telescope in a radio quiet zone at the Murchison Radio-astronomy Observatory in Western Australia.


    Cosmic time machine: the EDGES radio telescope sheds light on primordial gravitational waves. Credit:Suzyj/CC BY-SA 4.0.

    The cosmic microwave background (CMB) is a rich source of information about the early universe, and now physicists in Switzerland and Germany reckon it could also serve as a detector of high-frequency gravitational waves, which are ripples in space–time.

    CMB per ESA/Planck.

    Indeed, the researchers have used pre-existing radio observations of the CMB to calculate new upper limits on the size of high-frequency primordial gravitational waves.

    The best developed technique for detecting gravitational waves, and the one used to discover them in 2015, relies on interferometry. In LIGO and other observatories, laser beams are deflected between mirrors at the ends of long (several kilometres) evacuated pipes and then interfere with one another.

    When a gravitational wave travels through the Earth it causes tiny changes in the distance between the mirrors, which is observed as changes in how the light interferes.

    The size of interferometers like LIGO makes them most sensitive to gravitational waves within a certain frequency band – from about 10 Hz to 10 kHz – meaning that much of the gravitational-wave spectrum remains unexplored. While the planned space-based LISA observatory will target lower frequencies in the millihertz range to detect waves from supermassive black holes, observations at megahertz, gigahertz or even higher frequencies could provide a window on exotic phenomena in the very young, hot universe.

    Gravity is talking. Lisa will listen. Dialogos of Eide.


    ESA/NASA eLISA space based, the future of gravitational wave research.

    Detecting these high frequencies could also provide new insights into the fundamental constituents of nature, by allowing tests of the Standard Model of particle physics at energies beyond the most powerful particle colliders.

    Standard Model of Particle Physics via http://www.plus.maths.org .

    The Gertsenshtein effect

    To observe these higher frequencies, physicists have investigated a range of alternative approaches. This latest effort relies on the Gertsenshtein effect, which involves gravitational waves converting into electromagnetic waves (or vice versa) in the presence of a magnetic field.

    While other researchers have looked for this effect in the results of pre-existing terrestrial experiments, Valerie Domcke at the CERN laboratory in Geneva and Camilo Garcia Cely at DESY in Hamburg have come up with a way for detecting the effect at cosmic scales. The idea is to scrutinize the spectrum of the all-pervasive CMB, which was produced about 400,000 years after the Big Bang when electrons combined with protons to form neutral hydrogen. Whereas today’s leading cosmological model tells us that this spectrum should be that of a black body, significant cosmic conversion of gravitational to electromagnetic radiation at megahertz to gigahertz frequencies would instead raise the intensity of the CMB’s low frequency “tail”.

    The researchers specifically looked for distortions in the CMB spectrum generated before the first stars formed and hydrogen started reionizing, some 150 million years or so after the universe came into being. During these “dark ages” there were few free electrons to scatter photons, so the probability of oscillations occurring between gravitational and electromagnetic waves was higher than it would otherwise have been.

    EDGES and ARCADE2

    To set new limits on the size of gravitational waves at high frequencies, Domcke and Garcia Cely analysed data from two radio telescopes designed to peer far back in time. One, EDGES [above], consists of two dipole antennas and a dish located in the desert of Western Australia. The other, ARCADE2, was a balloon experiment flown over Texas.

    2
    Absolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission (ARCADE) is a program which utilizes high-altitude balloon instrument package intended to measure the heating of the universe by the first stars and galaxies after the big bang and search for the signal of relic decay or annihilation. In July 2006 a strong residual radio source was found using the radiometer, approximately six times what is predicted by theory. This phenomenon is known as “space roar” and remains an unsolved problem in astrophysics.

    The researchers found they could indeed use the data to set new limits, although they did have to make an assumption about the strength of cosmic magnetic fields. With the fields set low, their results were less stringent than those from putative terrestrial oscillations – the maximum amplitudes at 78 MHz (EDGES) and 3-30 GHz (ARCADE2) coming in at one part in 10^12 and 10^14 respectively. But with the fields set high, those limits dropped to one part in 10^21 and 10^24 respectively, the latter being seven orders of magnitude lower than limits imposed by the most sensitive laboratory experiment.

    Domcke and Garcia Cely argue that their new approach to gravitational-wave detection could improve substantially as radio telescopes become more sensitive – particularly as scientists develop new facilities to measure the 21 cm line in neutral hydrogen, which is central to studies of reionization. More sensitive telescopes would set tighter limits on primordial gravitational waves or could even reveal their existence. They say that this radiation could in principle be produced by sources such as merging light black holes or from clouds of dark matter around spinning black holes.

    They add that excess photons with frequencies below 10 GHz have been observed by both EDGES and ARCADE2. However, they point out that this excess would imply that gravitational waves have far more energy than that inferred from other cosmological observations. As a result, they say that astrophysical sources, “are a more likely explanation for the excess radiation observed”.

    A paper describing the work has been accepted for publication in Physical Review Letters.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.


    Stem Education Coalition

    PhysicsWorld is a publication of the Institute of Physics. The Institute of Physics is a leading scientific society. We are a charitable organisation with a worldwide membership of more than 50,000, working together to advance physics education, research and application.

    We engage with policymakers and the general public to develop awareness and understanding of the value of physics and, through IOP Publishing, we are world leaders in professional scientific communications.
    IOP Institute of Physics

     
  • richardmitnick 9:40 am on September 25, 2020 Permalink | Reply
    Tags: , Ice­Cube made history in 2013 when it reported intercepting the first extra­galactic neutrinos., , P-ONE will consist of seven groups of 10 detector strings creat­ing an instrument volume of about 3 km3., , physicsworld.com, The new facility will be located at a depth of about 2.6 km in the Cas­cadia Basin some 200 km from the coast of British Columbia., ,   

    From physicsworld.com: “Astronomers plan huge neutrino observatory in the Pacific Ocean” 

    From physicsworld.com

    18 Sep 2020
    Edwin Cartlidge

    1
    Ocean bound: P-ONE will consist of seven groups of 10 detector strings, creating an instrument larger than the existing IceCube experiment (pictured). (Courtesy: IceCube Collaboration/NSF.)

    Astrophysicists in Germany and North America have published plans to build the world’s larg­est neutrino telescope on the sea floor off the coast of Canada.

    The Pacific Ocean Neutrino Experiment (P-ONE) is designed to snare very-high-energy neutrinos generated by extreme events from beyond our galaxy.

    Neutrino telescopes observe the Čerenkov radiation that is emitted when neutrinos passing through the Earth interact very occasionally with atomic nuclei resulting in the production of fast-moving secondary particles. Being uncharged and exceptionally inert, neutrinos can penetrate gas and dust as they travel through the universe, allowing astronomers in principle to identify the exceptionally energetic phenomena that generate them. Photons from such events, in contrast, are absorbed on their journey.

    The world’s largest neutrino tele­scope, known as IceCube, consists of dozens of strings of photomultiplier tubes suspended in holes drilled deep into the ice at the South Pole.

    U Wisconsin IceCube neutrino observatory

    U Wisconsin ICECUBE neutrino detector at the South Pole.

    IceCube employs more than 5000 detectors lowered on 86 strings into almost 100 holes in the Antarctic ice NSF B. Gudbjartsson, IceCube Collaboration.

    Lunar Icecube.

    IceCube DeepCore annotated .

    IceCube neutrino detector interior.

    IceCube employs more than 5000 detectors lowered on 86 strings into almost 100 holes in the Antarctic ice NSF B. Gudbjartsson, IceCube Collaboration.

    Lunar Icecube.

    IceCube DeepCore annotated.

    IceCube PINGU annotated.

    DM-Ice II at IceCube annotated.

    IceCube Gen-2 DeepCore PINGU annotated.

    DM-Ice II at IceCube annotated.

    Covering a volume of 1 km3, Ice­Cube made history in 2013 when it reported intercepting the first extra­galactic neutrinos. Four years later it then recorded an event that could be tied to a very distant, bright galactic nucleus known as a blazar, thanks to concurrent gamma-ray observations.

    According to P-ONE head, Elisa Resconi at the University of Munich, IceCube’s 2017 result strictly speak­ing only constitutes “evidence” for the blazar source. To really claim a discovery and pinpoint the origin of other cosmic neutrinos, she argues, requires the construction of addi­tional neutrino observatories as well as the extension of IceCube. “We are now on the verge of opening up neutrino astronomy,” she says, “but if we base this process on just one telescope it could take a really long time, perhaps decades.”

    Heading underwater

    P-ONE will consist of seven groups of 10 detector strings creat­ing an instrument volume of about 3 km3. Being larger than IceCube, it will detect rarer, higher-energy neutrinos, and will be most sensi­tive at a few tens rather than a hand­ful of teraelectronvolts. It will also observe a different part of the sky, mainly capturing neutrinos from the southern hemisphere rather than the north. But there will be some over­lap between the two, says Resconi, potentially allowing independent observations of the same event.

    The new facility will be located at a depth of about 2.6 km in the Cas­cadia Basin, some 200 km from the coast of British Columbia. As such, it will take advantage of pre-existing infrastructure – an 800 km-long loop of fibre-optic cable operated by the University of Victoria’s Ocean Net­works Canada that supplies power and ferries data to and from existing sea-floor instruments.

    Having already confirmed that this site has the necessary optical prop­erties by sending down two initial strings of light emitters and sensors in 2018, the P-ONE collaboration are now planning to deploy a steel cable with addi­tional detectors to investigate the site – including spectrometers, lidars and a muon detector. The plan then, says Resconi, is to install the first part of the observatory – a ring containing seven 1 km-long strings – around the end of 2023. And if that succeeds, the researchers will then apply for the bulk of the $50–100m needed to complete the project, with personnel costs adding roughly $100m more.

    Resconi hopes that the full obser­vatory will be installed and taking data by the end of the decade. But she describes this timeline as “very ambitious”. In addition to delays caused by the ongoing COVID- 19 pandemic, she says it will be a challenge to ensure that the detec­tors work as planned – given the huge pressures and the presence of salt and sea creatures, which together make the seabed such a harsh environment.

    Indeed, scientists had already planned on operating a cubic-kilome­tre scale neutrino telescope known as KM3NeT on the floor of the Mediter­ranean Sea back in 2014, which was delayed to 2020.

    KM3NeT Digital Optical Module (DOM) in the laboratory .www.km3net.org.

    Artist’s expression of the KM3NeT neutrino telescope.

    According to col­laboration member Feifei Huang, just two of the 230 strings due to be installed off the coast of southern Italy are so far in place, while another site in French waters currently has six out of a planned 115 strings running – with completion not foreseen until 2026 and 2024 respectively.

    Resconi says that part of the problem with that project is a lack of specialist personnel, with the physicists essentially doing everything themselves – for example, their self-built junction boxes, which connect cables on the sea floor, having failed. She hopes that the experience acquired by Ocean Networks Canada will mean a similar fate can be avoided for P-ONE. With 30 or 40 people dedicated to laying cables in the ocean, she says that her team “can focus on the physics”.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.


    Stem Education Coalition

    PhysicsWorld is a publication of the Institute of Physics. The Institute of Physics is a leading scientific society. We are a charitable organisation with a worldwide membership of more than 50,000, working together to advance physics education, research and application.

    We engage with policymakers and the general public to develop awareness and understanding of the value of physics and, through IOP Publishing, we are world leaders in professional scientific communications.
    IOP Institute of Physics

     
  • richardmitnick 12:50 pm on May 8, 2020 Permalink | Reply
    Tags: Atomic comagnetometer, , , , , , physicsworld.com   

    From physicsworld.com: “Ultracold atomic comagnetometer joins the search for dark matter” 

    From physicsworld.com

    05 May 2020
    Hamish Johnston

    1
    In a spin: illustration of a Bose–Einstein condensate of rubidium atoms in two different quantum states. (Courtesy: ICFO/ P Gomez and M Mitchell)

    A new atomic comagnetometer that could be used to detect hypothetical dark matter particles called axions has been created by physicists in Spain. The sensor uses two different quantum states of ultracold rubidium atoms to cancel out the effect of ambient magnetic fields, allowing physicists to focus on exotic spin-dependent interactions that may involve axions.

    Dark matter is a mysterious substance that appears to account for about 85% of the matter in the universe – the other 15% being normal matter such as atoms and molecules. While myriad astrophysical observations point to the existence of dark matter, physicists have very little understanding of its precise nature.

    Some dark matter could comprise hypothetical particles called axions, which were first proposed in the 1970s to solve a problem in quantum chromodynamics. If dark matter axions do exist, they could mediate exotic interactions between quantum-mechanical spins – in analogy to how photons mediate conventional magnetic interactions between spins.

    Two detectors

    These exotic interactions would be weak, but in principle they could be measured using an atomic comagnetometer, which comprises two different magnetic-field detectors that are in the same place. The device is set so that the effects of ambient magnetic fields in the two detectors can be cancelled out. So, a residual signal in the comagnetometer could be the result of an exotic interaction between atomic spins within the detector itself.

    The new comagnetometer was created at the Institute of Photonic Sciences in Barcelona by Pau Gomez, Ferran Martin, Chiara Mazzinghi, Daniel Benedicto Orenes, Silvana Palacios and Morgan Mitchell. The two different detectors are rubidium-87 atoms that are in two different spin states that respond in different ways to magnetic fields.

    Near absolute zero

    The atoms are in a gas that is chilled to near absolute zero to create a Bose-Einstein condensate (BEC). In this state the atoms are relatively immune to being jostled about by thermal interactions. This means that for several seconds the spins can respond in a coherent way to spin interactions. The BEC is also very small – just 10 microns in diameter – which boosts its performance as a comagnetometer and means that short-range axion interactions can be probed.

    The response of the spins to a magnetic field is measured by firing a polarized of a beam of light at the BEC and measuring how its polarization is rotated. By comparing measurements on the two different spin states, the effect of ambient magnetic fields can be removed, allowing the team to look for any exotic interactions that are affecting the spins.

    Although no evidence of axions has been found by the device so far, the team has shown that the comagnetometer is highly immune to noise from ambient magnetic fields. They say that it could be run at a sensitivity on par with other types of comagnetometers that are currently looking for axions. The device has already been used to measure conventional spin interactions between the ultracold atoms and the team says that other potential applications include spin amplification, which could be used to study quantum fluctuations.

    The comagnetometer is described in Physical Review Letters.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.


    Stem Education Coalition

    PhysicsWorld is a publication of the Institute of Physics. The Institute of Physics is a leading scientific society. We are a charitable organisation with a worldwide membership of more than 50,000, working together to advance physics education, research and application.

    We engage with policymakers and the general public to develop awareness and understanding of the value of physics and, through IOP Publishing, we are world leaders in professional scientific communications.
    IOP Institute of Physics

     
  • richardmitnick 3:24 pm on April 27, 2020 Permalink | Reply
    Tags: "High pressure experiment sheds light on Earth’s outer core", physicsworld.com, , SPring-8 synchrotron   

    From physicsworld.com: “High pressure experiment sheds light on Earth’s outer core” 

    From physicsworld.com

    27 Apr 2020
    Sam Jarman

    1
    Under pressure: X-ray scattering at high pressure and temperature provides new insights into the composition of the Earth’s outer core. (Courtesy: Shutterstock/Johan-Swanepoel)

    Extreme conditions close to those found within the Earth’s outer core have been created in the lab by planetary scientists in Japan. Researchers led by Yasuhiro Kuwayama at the University of Tokyo created the temperatures and pressures needed for their experiment using a highly specialized diamond anvil. Their discoveries could lead to a better understanding of the composition and behaviour of the Earth’s outer core, and perhaps even the interiors of other planets.

    The Earth’s core begins about 3000 km below the surface and much of what we know about it comes from looking at seismic waves from earthquakes that have travelled through the centre of the Earth. The core’s properties have also been studied by doing computer simulations and experiments that subject materials to extreme temperatures and pressures. Research has revealed that the centre of our planet is separated into a solid inner core composed mainly of an iron-nickel alloy and an outer core dominated by liquid iron.

    Now, Kuwayama’s team has increased our knowledge of the outer core using a diamond anvil, which exploits diamond’s almost unparalleled hardness to subject samples to extremely high pressures and temperatures. In their study, they compressed a liquid iron sample to pressures of up to 116 GPa and heated it to of 4350 K. While 4350 K is believed to be a typical temperature within the outer core, 116 GPa is slightly lower than the pressure expected at the top of the outer core.

    Sustained pressure

    An important feature of this latest research is that this extreme pressure and temperature can be maintained indefinitely – at least in principle. This is unlike previous studies in which extreme conditions were only sustained for a few microseconds. The team squeezed a tiny liquid droplet of liquid iron to 116 GPa and then heated it to 4350 K using an infrared laser. Then the team probed their sample’s properties in detail, primarily by doing X-ray scattering experiments at RIKEN’S Spring-8 synchrotron in Hyōgo prefecture.


    SPring-8 synchrotron, located in Hyōgo Prefecture, Japan

    After combining their observations with existing data, Kuwayama and colleagues compared the measured thermodynamic properties of their high-pressure, high-temperature liquid iron to what is known about Earth’s outer core. They found that the Earth’s outer core must be around 7.5% less dense than the liquid iron, suggesting that it must contain a high abundance of lighter elements that have yet to be identified. The team also found that material in the outer core must flow around 4% more easily than liquid iron, although both materials display a similar resistance to compression.

    Kuwayama’s team says that its work offers important new insights into the physical properties of Earth’s core. Their work could also inform future studies of other planetary cores – which even within the solar system, encompass a rich variety of compositions, structures, and relative sizes. As Kuwayama concludes, “we were pleasantly surprised by how effective this approach was and hope it can lead to a greater understanding of the world beneath our feet”.

    The research is described in Physical Review Letters.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.


    Stem Education Coalition

    PhysicsWorld is a publication of the Institute of Physics. The Institute of Physics is a leading scientific society. We are a charitable organisation with a worldwide membership of more than 50,000, working together to advance physics education, research and application.

    We engage with policymakers and the general public to develop awareness and understanding of the value of physics and, through IOP Publishing, we are world leaders in professional scientific communications.
    IOP Institute of Physics

     
  • richardmitnick 8:49 am on February 28, 2020 Permalink | Reply
    Tags: "IceCube identifies four galaxies as likely sources of cosmic rays", , , , , From U Wisconsin IceCube Collaboration, , physicsworld.com   

    From U Wisconsin IceCube Collaboration via physicsworld.com: “IceCube identifies four galaxies as likely sources of cosmic rays” 

    U Wisconsin ICECUBE neutrino detector at the South Pole

    From U Wisconsin IceCube Collaboration

    via

    physicsworld.com

    26 Feb 2020
    Sam Jarman

    A huge observatory at the South Pole has identified four galaxies as likely sources of cosmic rays. Rather than detecting cosmic rays, the team analysed a decade’s worth of data gathered by the IceCube Neutrino Observatory to pinpoint the sources, which are expected to also emit huge numbers of neutrinos. The team says that this is the best-ever identification of cosmic ray sources.

    Cosmic rays are high-energy charged particles that originate outside the solar system.

    Cosmic rays produced by high-energy astrophysics sources (ASPERA collaboration – AStroParticle ERAnet)

    They are thought to be created by violent astrophysical processes capable of accelerating particles to near the speed of light. However, working-out exactly where cosmic rays come from has proven very difficult because their trajectories are deflected by the magnetic fields permeating interstellar space. Cosmic neutrinos offer a solution because they should be produced in the same places as cosmic rays but are not deflected by magnetic fields.

    IceCube comprises of strings of photomultiplier tubes that are suspended within a cubic kilometre of ice at the South Pole [see images below]. Occasionally a muon neutrino will collide with an atom in the ice, creating a muon that will then emit Cherenkov light as it travels through the ice. This light is detected by the photomultipliers and the signal can be used to work-out where the neutrino came from.

    Atmospheric background

    Locating neutrino sources in the cosmos is not easy because the IceCube detector is swamped by signals from muons and muon neutrinos created by cosmic ray collisions with the atmosphere. These create a large and diffuse background signal and the challenge is to pick-out point sources of cosmic neutrinos within this background.

    The IceCube team used a new data-analysis technique that could process all full-sky observations made between April 2008 and July 2018 – something that was not possible before for software-related reasons. The quasar-like galaxy NGC 1068 emerged as a particularly likely source of cosmic ray neutrinos, standing out of the background with a 2.9σ statistical significance. When combined with three other galaxies that were identified, the four sources collectively stand above the background at a statistical significance of 3.3σ.

    Although this remains well short of the 5σ that is normally considered a discovery, the IceCube analysis is strongest evidence that these four galaxies are cosmic-ray emitters. The researchers now hope that their results will motivate further studies of these sources by looking for more neutrinos as well as gamma rays and X-rays – which are also associated with cosmic-ray sources.

    The study is described in Physical Review Letters.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    PhysicsWorld is a publication of the Institute of Physics. The Institute of Physics is a leading scientific society. We are a charitable organisation with a worldwide membership of more than 50,000, working together to advance physics education, research and application.

    We engage with policymakers and the general public to develop awareness and understanding of the value of physics and, through IOP Publishing, we are world leaders in professional scientific communications.
    IOP Institute of Physics

    IceCube is a particle detector at the South Pole that records the interactions of a nearly massless sub-atomic particle called the neutrino. IceCube searches for neutrinos from the most violent astrophysical sources: events like exploding stars, gamma ray bursts, and cataclysmic phenomena involving black holes and neutron stars. The IceCube telescope is a powerful tool to search for dark matter, and could reveal the new physical processes associated with the enigmatic origin of the highest energy particles in nature. In addition, exploring the background of neutrinos produced in the atmosphere, IceCube studies the neutrinos themselves; their energies far exceed those produced by accelerator beams. IceCube is the world’s largest neutrino detector, encompassing a cubic kilometer of ice.

    IceCube employs more than 5000 detectors lowered on 86 strings into almost 100 holes in the Antarctic ice NSF B. Gudbjartsson, IceCube Collaboration

    Lunar Icecube

    IceCube DeepCore annotated

    IceCube PINGU annotated


    DM-Ice II at IceCube annotated

     
c
Compose new post
j
Next post/Next comment
k
Previous post/Previous comment
r
Reply
e
Edit
o
Show/Hide comments
t
Go to top
l
Go to login
h
Show/Hide help
shift + esc
Cancel
%d bloggers like this: