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  • richardmitnick 7:13 pm on November 24, 2014 Permalink | Reply
    Tags: , , , , IceCube Experiment,   

    From IceCube: Video on Neutrinos Parts 1 and 3 Previously Missing 

    icecube
    IceCube South Pole Neutrino Observatory

    The good folks at http://icecube.wisc.edu/ pointed me to these missing videos. You previously saw only Part 2

    Part 1
    Solar Neutrinos: Verifying how the Sun shines has led to the discovery of neutrino flavor conversion and that neutrinos are massive.

    Part 3
    Neutrinoless double beta decay experiment in the Canfranc Underground Laboratory.
    The search for a property of the neutrino that might explain why matter defeated antimatter.

    Watch, enjoy, learn.

    See the full article here.

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    ICECUBE neutrino detector
    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.

     
  • richardmitnick 3:12 pm on November 21, 2014 Permalink | Reply
    Tags: , , , , IceCube Experiment,   

    From IceCube: “Neutrino, measuring the unexpected” 

    icecube
    IceCube South Pole Neutrino Observatory

    Francis Halzen, IceCube Principal Investigator, explains the search for high-energy neutrinos in this three party story of neutrinos. Produced by IFIC, Directed by Javier Diez. [Sorry, I cannot come up with Parts 1 and 3. But this video stands on its own merit.]

    Watch, enjoy. learn.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    ICECUBE neutrino detector
    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.

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  • richardmitnick 9:05 pm on November 17, 2014 Permalink | Reply
    Tags: , IceCube Experiment,   

    From IceCube: “A new polar season for IceCube” 

    icecube
    IceCube South Pole Neutrino Observatory

    17 Nov 2014
    Silvia Bravo

    After a long winter, South Pole inhabitants are getting used to the sunlight again. Up north, a bunch of IceCubers are getting ready for their Antarctic adventure. For some of them, it’s all about the excitement of a first trip to Antarctica. For some others, it’s an almost annual appointment that makes their job a special one.

    Erik Beiser and Stephan Richter, the new 2014-15 IceCube winterovers, stepped onto South Pole ice on November 6 with the first flight of the season. They are there to stay for a year: first enjoying the hectic months of the austral summer at the Admundsen-Scott South Pole Station, and then becoming two of the solitary souls in the darkness of the austral winter.

    4
    Four IceCube winterovers: from left to right, Erik and Stephan (2014-2015), Dag and Ian (2013-2014). Image: Ralf Auer. IceCube/NSF.

    Now it’s time to finish their training. The incoming winterovers have learned about the IceCube data taking systems in Madison and also about other South Pole systems in Denver. Their expertise is further solidified on-ice through their interactions with the outgoing winterovers, Dag Larsen and Ian Rees.

    Other activities during this season include the maintenance and updates of the computing and power units in the IceCube Lab (ICL). “This year, new power distribution units will allow IceCube winterovers to monitor some of our custom-built readout systems, the so-called DOMHubs, from the station without requiring them to walk out to the laboratory,” says Ralf Auer, who is the system administrator for the South Pole data center. The walk to the ICL is about 1 km long, a short scenic route when the weather is nice that can feel like a long nightmare with wind and temperature approaching -100 F.

    path
    The path to the ICL in October 2014. Image: Dag Larsen. IceCube/NSF

    “The remote-controlled units will help to reduce detector downtime and start data taking faster after a system crash,” explains Auer. Ian and Dag, now leaving the Pole, have set a new record for IceCube uptime, at 99.5% on average during the last year. The new system might help Erik and Stephan, the brand new winterovers, to improve this register.

    Moreover, the disk array storage deployed last year has proven to be stable and reliable and will grow to become the main on-site IceCube data storage system, replacing the old magnetic tapes.

    Also new for this season are planned IceTop measurements to better understand how the accumulated snow might be affecting the performance of the detector. About 20-25 cm of snow accumulates on top of each IceTop tank every year, with snow heights up to 2.5 m measured these days. “Initially, we thought that we could keep snow level limited, but currently snow management is too expensive at the Pole. As the accumulated snow grows, we want to improve our understanding of its impact on what IceTop measures,“ explains Sam De Ridder, a graduate student at University of Ghent, who will be traveling to Antarctica in early January.

    IceTop was designed to detect the showers of particles created by the interaction of cosmic rays with the atmosphere. However, due to the accumulated snow, IceTop is becoming more and more sensitive to muons compared to the electromagnetic part of the air shower. A good knowledge of the muon signal in the shower is very important for measurements of the cosmic ray composition but also for using IceTop as a veto for neutrino searches in IceCube.

    For this reason, several measurements of the muon signal around the tanks will be performed during this season, as well as more detailed measurements of the snow density. “We are pretty confident that with these measurements we can improve the handling of the snow in IceTop and gain more knowledge for the future IceCube surface extensions,” adds De Ridder.

    pl
    The arrival of an LC-130 is a sign that the summer activities are ongoing. Image: IceCube/NSF

    Even with the IceTop measurements and some further activities, this is not a busy season for IceCube. “It will be a light workload for Cubers at the Pole this year, probably the least amount of activity for IceCube since the 2002/2003 season. Our population is down to 16 compared to 100 during peak construction. We are shipping only 3800 pounds of cargo, and we used to have about 25,000 pounds for each IceCube string,” says Jim Haugen, who is responsible for IceCube’s South Pole planning and logistics.

    Researchers from US, Germany, Belgium and Korea will make sure that everything is ready for another year of data-taking. “I am excited for the 10 IceCube first-timers who will be working at Pole this year. It’s always thrilling to arrive at Pole, but nothing beats that first time when the Herc glides to a stop and the loadmaster opens the door flooding the plane with very cold air prior to leaving the plane,” adds Haugen.

    Among the fortunate Antarctic travelers, Armando Caussade of Puerto Rico is the NSF/PolarTREC teacher who will participate in some of the IceCube activities and engage more Hispanic students in astrophysics research. Follow his journal here.

    See the full article here.

    Please help promote STEM in your local schools.

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    ICECUBE neutrino detector
    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.

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  • richardmitnick 4:45 pm on November 13, 2014 Permalink | Reply
    Tags: , , DM-Ice, IceCube Experiment, WIPAC   

    From IceCube: “DM-Ice collaborators discuss dark matter search” 

    icecube
    IceCube South Pole Neutrino Observatory

    Deep in the ice at the South Pole, the IceCube Neutrino Observatory sits and waits for high-energy particles to pass in its midst. However, another detector, DM-Ice, is situated among IceCube’s strings, partnering with its technology for a different purpose: the search for dark matter. Currently, the only detector to make a strong claim to have seen a dark matter signal is DAMA, at the Gran Sasso National Laboratory in Italy. DM-Ice aims to carry out a definitive test of DAMA’s claim.

    DM-Ice at IceCube
    DM-Ice

    DAMA at Gran Sasso
    DAMA II at Gran Sasso
    DAMA at Gran Sasso

    Among the established WIPAC community are two enthusiastic physicists who can reveal some of the mystery behind the search for dark matter. Reina Maruyama of Yale University has been the principal investigator of DM-Ice since its inception in 2010, during her time as a WIPAC researcher. Among her team of collaborators is Matt Kauer, a postdoc at WIPAC, who is currently working to advance the development of the detector to its full scale.

    two
    Matt Kauer and Reina Maruyama at WIPAC during a meeting of the DM-Ice Collaboration.

    Q: Can you explain to us what dark matter is?

    Matt (M): Dark matter makes up approximately 27% of all matter and energy in our universe right now. But, in fact, no one really knows what this matter is, where it comes from, or what it interacts with. There are a handful of theories explaining what dark matter could be, but we have yet to confirm its origin and nature.

    Reina (R): From the luminosity of stars, we can infer their mass. From measuring the speed of rotation of stars, we can also infer their mass and the mass of objects that they rotate around. The second measurement gives us masses much higher than the first, which leads us to believe that there must be much more mass out there than we can see. We call this dark matter. There are other observations that point toward the existence of this invisible mass, like seeing light from distant stars bent around invisible objects. The question is, what is this matter. One of our favorite hypotheses is the so-called WIMP (Weakly interacting massive particles) model. If the dark matter we see out there is made of WIMPs, we might be able to see their interaction with ordinary matter, even if this happens very occasionally.

    dm
    DM-Ice detector and dark matter modulation explained. Graphic: Jamie Yang/WIPAC.

    Q: What is the goal of DM-Ice?

    R: DM-Ice really started with a request from the dark matter community. For the last 15 years, the DAMA collaboration has claimed that they have observed dark matter. Their signature is coming from an annual modulation in the number of observed dark matter induced interactions in the DAMA detector, due to the orbit of the Earth around the Sun. The flux of dark matter from the galactic halo on Earth should be higher in early June, when the rotational speed of our planet is added to that of the Sun with respect to the galaxy. In early December, when these two velocities are in the opposite directions, the dark matter signature should be smaller. Since DAMA announced these results, there have been ongoing discussions in the community about whether what DAMA is seeing is really a dark matter signature or just some background fluctuation.

    M: DAMA is located in Italy, under the Gran Sasso Mountain, while DM-Ice is buried in the Antarctic ice at the South Pole. From our location, we have a reversed phase of environmental backgrounds with respect to the Northern Hemisphere while the dark matter signature is the same in both hemispheres. Thus, seeing an annual modulation with DM-Ice that’s consistent with DAMA’s dark matter signature would be a smoking-gun confirmation.

    R: Right. DAMA’s results have been out there for a very long time, and there are many concerns that the dark matter community has expressed about them. Although the DAMA collaboration has tried to address every concern that people have raised, the truth is that there are many things that can vary annually. We’re trying to look for a very, very small signal, and there are many possibilities that could mimic the signature that DAMA sees.

    Q: A deployment at the South Pole is never a simple task. What’s the story behind DM-Ice?

    R: The idea came when IceCube was being deployed, back in 2009. Having a detector in the Southern Hemisphere is a great choice, since it allows a cross check of systematics. Francis Halzen (the IceCube PI) and I talked a lot about it, and finally I agreed to at least take a look and assess if it was feasible. I first thought it was the craziest idea, but then I went to the Pole for work related to IceCube and saw what it’s like to work there. And I saw how fantastic this team was, and I came back thinking that this was actually possible. And that’s what we did; we put together a prototype for DM-Ice, starting from scratch.

    M: Quickly obtaining NaI crystals for the detector seemed challenging, but there was an elegant solution. The NAIAD experiment was an old dark matter experiment from the early 2000’s in the Boulby mine in the U.K. The experiment had been decommissioned but the crystals were still in storage at the mine, so we talked with them, and they shipped us two of their crystals for DM-Ice. Those are the crystals now taking data at the South Pole.

    Q: And all this happened very fast, didn’t it?

    R: Yes. DM-Ice was designed and built in nine months and we deployed the prototype during the next polar season at the end of 2010, the final IceCube construction season. The result of this intense year of work is what’s operating at the South Pole now.

    M: It’s pretty amazing. The teams at PSL (Physical Sciences Laboratory), WIPAC, and in general the IceCube community, made this possible. They supported us with the design and manufacturing of the material components and electronics. The logistics of getting an experimental apparatus to the South Pole requires a lot of coordination. We work with IceCube and WIPAC to maintain the data acquisition electronics at the South Pole.

    Q: When we read about DM-Ice we learn that it’s a sodium iodide detector. How exactly does a sodium iodide detector work?

    R: Sodium iodide detectors have existed for the last 50 or more years. This crystal is transparent, dense and has low backgrounds, all of which are important properties when you are trying to look for interactions of yet-to-be-observed particles that very rarely interact. And when they do interact, they could look like interactions induced by well-known particles.

    The detection principle is quite simple. We measure dark matter interactions by recording the recoil of target nuclei scattered by a WIMP. When the sodium iodide nuclei get a kick from scattered WIMPs, they would essentially excite electrons in the detector. As the electrons decay back down to their ground state they emit light. Then we collect that light using photomultiplier tubes (PMTs), just like in IceCube, and depending on how many photons come out, it could tell us the energy of that interaction.

    Q: What is the difference between a dark matter reaction and just another particle reaction?

    M: The amplitude and shape of the interaction are the relevant parameters. With a typical dark matter interaction in DM-Ice, we expect on the order of 100 to 200 photons to be emitted during the nuclear relaxation. This translates to a very small energy range we’re interested in. The shape of the signal, or the time-scale over which the photons are emitted, also provides information about the type of particle interaction being observed.

    R: Detecting this collision with a very distinct energy signature would be an indication of dark matter, but on top of that, if we can observe the annual modulation we have mentioned, with the correct phase and correct rate, then we have an additional signature for dark matter.

    mr
    Maruyama at South Pole for DM-Ice deployment. Image: DM-Ice Collaboration.

    Q: So, what is the detector’s current status as of 2014?

    M: DM-Ice 17 is taking data right now in the ice at the South Pole, mainly as a proof of concept for a full-scale deployment in the ice. We now have 17.5 kilograms of target material from the crystals we inherited from NAIAD, but these crystals are a little too high in internal backgrounds for a competitive analysis. We are currently collaborating with vendors to develop much cleaner crystals for use in the full-scale detector.

    R: As Matt says, our prototype is too small and too high in background to really be able to test DAMA, but we have proved that we can deploy and operate a dark matter detector at the Pole. The challenge is now to build the full-scale detector, which would be sensitive enough to see what DAMA sees. We have good teams at Yale, WIPAC, and other places in the U.S., Canada, and the U.K. contributing to our efforts.

    M: Here at WIPAC, the DM-Ice team consists of six people, contributing through different analysis and R&D projects geared toward the full-scale 250kg detector. We are, for example, working with two prototype crystals that we have underground at FNAL in Chicago and measuring the potassium backgrounds in those crystals.

    Q: What is the near future for DM-Ice?

    R: Our job is to be ready when IceCube is ready to drill again at the Pole, hopefully deploying the planned detector extensions. When IceCube drills again, we will have improved DM-Ice detectors that can go in the ice as well. In the meantime, we will run a similar sort of DM-Ice detector in the Northern Hemisphere. It would be a test to reproduce what DAMA found with an independent detector. However, we might just find the same result that DAMA did, without really learning much more about its origin.

    The original idea was to put this detector at the South Pole because it is really the ultimate test. If we see the same signature as DAMA, it would be very difficult to attribute it to the seasons. If we don’t see the same annual modulation that DAMA sees, then the scenario of it being dark matter can be ruled out, even if we don’t know the origin of that signal. Basically, we would be able to confirm or rule out DAMA’s claims of a dark matter observation.

    Q: Can you tell us more about what we can learn from a northern detector?

    R: There are different scenarios that could come from a northern deployment. You see no annual modulation, or you see the same signature as DAMA. If the signature is there, we might be able to test some background hypotheses to figure out what is there aside from dark matter. But we might also end up with a dark matter-only possible scenario, as DAMA did. I think we still have to bring this detector to some other location to verify that the dark matter signature phase stays the same everywhere on Earth to confirm that it’s due to dark matter. In summary, we might learn a few things from a northern run or we might not, but if we go straight to the Southern Hemisphere, then it’s one shot and we would have a definitive answer.

    Q: Will WIPAC be an important partner for a northern detector as well?

    M: Oh yes! WIPAC and our collaborators at the PSL, also at UW–Madison, contribute far beyond the South Pole expertise and logistics.

    R: I would say that’s what is unique about WIPAC and the University of Wisconsin—the existence of a scientific institution coupled with a very good technical and university-oriented engineering center. Being able to build big things at a university is rare, and I think that’s why IceCube was successful and why the DM-Ice demonstrator was possible. Yale also has similar capabilities, and together there is great intellectual and technical support behind DM-Ice.

    The team of collaborators working alongside Maruyama and Kauer include distinguished WIPAC physicists Francis Halzen and Albrecht Karle, and engineers Perry Sandstrom and Jeff Cherwinka, as well as students Antonia Hubbard, Walter Pettus, Bethany Reilly, and Zack Pierpoint from the UW–Madison and Yale communities.

    See the full article here.

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    ICECUBE neutrino detector
    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.

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  • richardmitnick 3:39 pm on October 28, 2014 Permalink | Reply
    Tags: , IceCube Experiment,   

    From ICECUBE: “Atmospheric neutrino oscillations measured with three years of IceCube data” 

    icecube
    IceCube South Pole Neutrino Observatory

    28 Oct 2014
    Silvia Bravo

    The IceCube Neutrino Observatory at the South Pole continues to contribute new ways to tackle some of the big questions in astrophysics and neutrino physics research. Results on extraterrestrial neutrinos, cosmic-ray anisotropy, dark matter searches and now neutrino oscillations have proven IceCube to be a powerful tool for exploring the unknown universe using high-energy particles produced in Nature.

    Last year, an initial measurement of the neutrino oscillation parameters was a hint that IceCube could become an important detector for studying neutrino oscillations. Today, the IceCube Collaboration has submitted new results to Physical Review Letters that present an improved measurement of the oscillation parameters, via atmospheric muon neutrino disappearance, which is compatible and comparable in precision to those of dedicated oscillation experiments such as MINOS, T2K or Super-Kamiokande.

    graph
    90 % confidence contours of the result in comparison with the ones of the most sensitive experiments. To the sides of the figure, the log-likelihood profiles for individual oscillation parameters are given. Normal mass hierarchy is assumed. Image: IceCube Collaboration

    Super-Kamiokande was the first experiment to claim the discovery of neutrino oscillations in 1998 from observing a deficit of atmospheric muon neutrino interactions in its detector.

    In contrast to the man-made, water-filled vessel of Super-Kamiokande, IceCube uses a natural target material, the glacier ice at the South Pole. This has the advantage of a much larger observation volume and therefore a larger number of events at shorter time scales. A disadvantage is that the optical properties of ice are more complex. The corresponding uncertainties are taken into account in the systematical errors of the IceCube result.

    “Today, both Super-Kamiokande and IceCube use the same “beam,” which is atmospheric neutrinos, but at different energies. And we reach a similar precision for the determination of the measurable oscillation parameters,” says Juan Pablo Yanez, a postdoctoral researcher at DESY and corresponding author of this paper. “But as IceCube keeps taking data and we keep improving our analyses, we might see important improvements in our collaboration results soon,” adds Yanez.

    IceCube records over one hundred thousand atmospheric neutrinos every year, most of them muon neutrinos produced by the interaction of cosmic rays with the atmosphere. DeepCore, a subdetector of the Antarctic neutrino observatory, allows the detection of neutrinos with energies down to 10 GeV.

    According to our understanding of neutrino oscillations, in which neutrinos can change their type on their trip through matter and space, IceCube should see fewer muon neutrinos at energies around 25 GeV and that reach IceCube after crossing the entire Earth. The reason for these missing muon neutrinos is that many oscillate into other flavors that are not seen by the detector or not selected in this analysis.

    IceCube researchers selected muon neutrino candidates with energies between a few GeV and around 50 GeV and coming from the Northern Hemisphere from data taken between May 2011 and April 2014. About 5,200 events were found, much below the 7,000 expected in the non-oscillations scenario.

    The parameters that best describe the IceCube data, and (normal mass hierarchy assumed), show uncertainties still larger than but already comparable to the neutrino-accelerator experiments. Stay tuned for further news about neutrino oscillations in IceCube!

    + Info “Determining neutrino oscillation parameters from atmospheric muon neutrino disappearance with three years of IceCube DeepCore data,” IceCube Collaboration: M.G. Aartsen et al. Submitted to Physical Review Letters, arXiv.org:1410.7227

    See the full article here.

    ICECUBE neutrino detector
    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.

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  • richardmitnick 8:00 pm on September 17, 2014 Permalink | Reply
    Tags: , , , , IceCube Experiment   

    From IceCube: “An improved measurement of the atmospheric neutrino flux in IceCube “ 

    icecube
    IceCube South Pole Neutrino Observatory

    17 Sep 2014
    Silvia Bravo

    Cosmic neutrinos in IceCube are the vogue these days, but atmospheric neutrinos are the popular ones if we look at the number of hits in the detector. Those neutrinos, created by the interaction of cosmic rays in the Earth’s atmosphere, are the main background in searches for astrophysical neutrinos.

    The IceCube Collaboration has submitted a paper today to the European Physical Journal C describing a new analysis scheme for the measurement of the atmospheric neutrino spectrum with the IceCube detector. The analysis was performed using data from May 2009 to May 2010, when the detector was running with a configuration of 59 of the final 86 strings.

    The spectrum was measured introducing a novel unfolding technique in the energy range from 100 GeV to 1 PeV, extending previous results of AMANDA by almost an order of magnitude. The new analysis also uses an improved selection, with results that showed a reduced atmospheric muon background contamination of 5 to 6 orders of magnitude and an 8% increase in the signal efficiency.

    The unfolded atmospheric neutrino spectrum agrees with both previous experimental results and the current theoretical models. The new method reduces the impact of the systematic uncertainties on the measured flux, but at high energies they are still too large to allow for conclusive results about a prompt and/or an astrophysical component of the overall flux.

    graph
    Comparison of the unfolding result obtained using IceCube in the 59-string configuration to previous experiments. Theoretical models are shown for comparison. Image: IceCube Collaboration.

    The analysis scheme presented in this paper introduces a machine learning algorithm for the final event selection that uses 25 event variables to distinguish between atmospheric muon tracks and tracks produced by neutrino-induced muons.

    “IceCube is a great detector for measuring atmospheric
    muon neutrinos. Those are, in fact, the vast majority of the neutrinos we detect. And by using tools and algorithms from data mining we can detect even more,” explains Tim Ruhe, a researcher at TU Dortmund University, in Germany.

    For every neutrino detected by IceCube, about a million atmospheric muons are observed. A common way to look for neutrinos in this huge muon background consists of selecting only upgoing muon tracks, since muons created by the interaction of cosmic rays with the atmosphere will be absorbed by the Earth when approaching IceCube from below. Thus, if the event reconstruction and selection were perfect, the remaining muon tracks would have been created by the interaction of a neutrino with the ice in or around the IceCube detector.

    However, previous to this analysis, the muon background rejection in IceCube was only 99.9% efficient because about 1,000 originally downgoing muons per every neutrino seen by IceCube were falsely reconstructed as upgoing tracks. With the new selection algorithm, IceCube researchers were able to reject 99.9999% of the incoming background events.

    + Info “Development of a General Analysis and Unfolding Scheme and its Application to Measure the Energy Spectrum of Atmospheric Neutrinos with IceCube,” IceCube Collaboration: M.G. Aartsen et al. Submitted to The European Physical Journal C, arXiv.org:1409.4535

    See the full article here.

    ICECUBE neutrino detector

    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.

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  • richardmitnick 1:30 pm on April 30, 2014 Permalink | Reply
    Tags: , , IceCube Experiment,   

    From Symmetry: “Possible expansion for South Pole detector” 

    Symmetry

    April 30, 2014
    Kathryn Jepsen

    Physicists hope to seek out the source of cosmic neutrinos by expanding the IceCube neutrino detector to 10 times its current size.
    ICECUBE neutrino detector
    IceCube Neutrino Detector at South Pole

    The detectors of the IceCube experiment have so far caught about 100 cosmic neutrinos, dozens of which came from outside our galaxy.

    The exact provenance of these particle cosmonauts is a mystery. That’s one reason IceCube scientists would like to expand their experiment, which covers a cubic kilometer of ice at the South Pole, to a volume 10 times as large.

    University of Wisconsin physicist Francis Halzen and colleagues made the case for the expansion at a workshop in Virginia on April 24.

    It’s as if the IceCube experiment is a giant digital camera, Halzen says, and every neutrino spotted is a pixel. “The more you have, the clearer the picture gets,” he says. “To see several neutrinos come from the same source, you are likely to need well above one thousand.”

    The sources of IceCube’s first 100 neutrinos could be exploding stars in distant galaxies. Or they could come from some other process, like the decay of dark matter particles in our galactic halo.

    “I can tell you what would be most exciting: if they came from something we haven’t seen before,” Halzen says.

    An expanded IceCube experiment could also include a bonus, smaller experiment called PINGU, which would detect lower-energy neutrinos to allow scientists to study their properties.

    Neutrinos are elementary particles that very rarely interact with other matter. To catch a thousand of them, IceCube scientists would need to run their current experiment for a decade, Halzen says.

    The IceCube experiment consists of more than 5000 detectors about the size and shape of a basketball, strung on 86 lines and lowered into holes in the ice. When a neutrino interacts with the ice, it releases a particle such as a muon. The small shockwave that follows the particle as it travels through the ice emits blue light in the form of Cherenkov radiation. The detectors catch this light.

    It turns out, the ice is even clearer than previously thought. The IceCube detectors built 15 years ago are located 125 meters apart from one another. If the scientists add new detectors, they’ll be able to double the spacing, which means they will be able to drastically expand the array without drastically increasing the number of detectors.

    “We can do this for about the same amount of money we spent on the original array,” Halzen says.

    The physicists would like to upgrade their hot-water ice drill, originally designed and built for IceCube at University of Wisconsin, and add 120 new strings of detectors, installing about 20 at a time over six years.

    See the full article here.

    Symmetry is a joint Fermilab/SLAC publication.



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  • richardmitnick 4:39 pm on November 8, 2013 Permalink | Reply
    Tags: , , , , IceCube Experiment, ,   

    From Symmetry: “Ultra-high-energy neutrinos” 

    November 08, 2013

    Scientists on the IceCube experiment discovered two extraterrestrial neutrinos with energies higher than any neutrino anyone had detected before.

    Kelen Tuttle

    Physicists on the IceCube experiment were in for a jolt. In processing data taken by their strings of more than 5000 light-sensitive detectors suspended under Antarctic ice, they discovered two particles called neutrinos with 1000 times more energy than the ones that regularly zip through IceCube’s detectors. They are the highest-energy neutrinos ever observed.

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    Courtesy of IceCube collaboration

    Nearly all of the neutrinos that IceCube sees are produced in Earth’s atmosphere. These atmospheric neutrinos tend to have energies somewhere between 1 and 10—and occasionally as high as 100—trillion electronvolts. The two unusual neutrinos appear to have come from far out in space and carried an impressive 1000 trillion electronvolts of energy. Each one lit up hundreds of IceCube’s detectors.

    “These two neutrinos were discovered in an analysis that was optimized to see something else entirely—so they were quite the surprise,” says Kurt Woschnagg, an IceCube collaborator from the University of California, Berkeley.

    Since these were the most exciting particles IceCube had ever observed, collaborators spent much time talking and writing about them.

    “These events were originally named with long strings of numbers,” says graduate student Jakob van Santen. “But that was confusing—people would accidentally mix them up by transposing numbers.”

    So van Santen named them Bert and Ernie, after the Sesame Street characters that their event displays somewhat resembled. He named Bert because it came from a more horizontal direction, whereas Ernie was more vertical and slightly larger, sort of like the heads of each Muppet.

    “Unfortunately my memory of Sesame Street was a bit too dim, as was pointed out to me some time later: Bert is the one with the elongated head, and Ernie is the wide one,” van Santen says. “By that time it was too late; the names had stuck.”

    Through careful analysis of Bert and Ernie, the collaboration confirmed that they had seen extremely high-energy neutrinos produced not in the Earth’s atmosphere, but somewhere beyond. Because neutrinos interact rarely with matter, these neutrinos may serve as messengers, carrying clear information about the most powerful cosmic events, including gamma-ray bursts, black holes and the formation of stars. The collaboration is now refining and expanding their analysis to learn more about these two zingers while also hunting for additional high-energy extraterrestrial neutrinos. Where there’s a Bert and an Ernie, there may also be a Mr. Snuffleupagus and an Oscar the Grouch.

    See the full article here.

    Symmetry is a joint Fermilab/SLAC publication.



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