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  • richardmitnick 12:16 pm on August 12, 2017 Permalink | Reply
    Tags: ALPIDE chip, , CERN ALICE, Desk cosmic ray detector, , , The ALPIDE chip is a CMOS monolithic active pixel sensor   

    From ALICE at CERN: “A desk cosmic ray detector for schools using the ALPIDE chip” 

    CERN
    CERN New Masthead

    11 August 2017
    Virginia Greco

    An educational and outreach project conceived by the ALICE ITS team is now moving forward rapidly thanks to Matthew Aquilina, who has joined the collaboration as a summer student, and his supervisors Magnus Mager and Felix Reidt.

    1
    Magnus Mager (left) and Matthew Aquilina (right). In the center, a prototype of compact cosmic ray detector based on the ALPIDE chip. [Credits: Virginia Greco]

    Would you like to have your own cheap and compact cosmic ray detector, sitting right on your desk? It sounds much like a nerdy fantasy, but indeed such a device can be realized and become a very useful educational and outreach tool.

    This was the idea inspiring the ALICE ITS team at CERN, who decided to use the pixel sensor chip (ALPIDE) to build a small and easy-to-operate cosmic ray detector. The project is now taking off thanks to the involvement of Matthew Aquilina – a summer student from Malta who joined the group at the end of June – and his supervisors Magnus Mager and Felix Reidt.

    The ALPIDE chip is a CMOS monolithic active pixel sensor being developed for the upgrade of the ITS of the ALICE experiment and characterized by very high detection efficiency.

    Some spare ALPIDE chips could be diverted to this pedagogical project, in which they are used to detect muons and electrons from cosmic rays. By making a stack of up to four chips, connected one-to-one, it is possible to reconstruct the trajectory of a particle crossing them. Considering an average rate of one cosmic ray per square centimeter per minute, with its active area of 1.4cm x 3cm, the ALPIDE chip registers a hit every few seconds. Because of the acceptance limitation in terms of solid angle due to the setup, the reconstruction rate is around 1 cosmic ray track per minute.

    “The ALPIDE chip is very good for this application since it has very low noise,” explains Magnus. “In addition, it has a multiple-event buffer that allow acquiring new data while we are reading out the previous, so essentially it is dead-time free.”

    2
    In order to target educational and outreach activities, a dedicated, cost-effective, and easy to use readout system was devised. It was decided to interface the chip to an Arduino microprocessor board, which is largely used for being very versatile and easy to program.

    The setup of the compact cosmic ray detector, thus, includes an Arduino card and up to four boards hosting each an ALPIDE chip, one on top of the other. “Programming the Arduino microprocessor to communicate with the chips turned out to be fairly easy,” Magnus comments, “but we still needed an interface to allow people having no specific technical expertise to operate the system.”

    Here is when Matthew came in. His main task, in fact, is to develop a user-friendly interface to control the system, with the aim to make it ‘plug and play’. He is employing the Unity platform, which is free software meant for developing 3D games but can also be used to make interfaces with 3D objects and operation menus. In this specific case, the user will be able to see on the screen the four detector planes, the pixel detectors on them and, when a cosmic ray crosses their active area, the corresponding hit in each plane. The work is still in progress but is moving forward rapidly.

    “When I started, first of all I had to study the Arduino-ALPIDE communication protocol, which meant going through the 110-page ALPIDE manual,” Matthew explains; “during the second week, I interfaced the microprocessor with Unity and then I started developing the user-friendly interface”. Indeed, he was chosen by Magnus and his colleagues among many candidates for his previous experience with the Unity software, which he had gained by developing a 3D game with it.

    A potential future development for the project is to allow data saving in exportable file formats to be read by other programs, so that some data analysis – such as angular distribution of the cosmic rays, day/night dependence and season dependence – could be performed.

    Once the user-friendly interface is done, it will be time to ‘advertise’ the project and make the system available to teachers and students. Some channels to take into consideration are the CERN teacher programmes and the CERN S’Cool Lab. “This device can be useful both for computer science and physics classes,” adds Magnus, “because students can learn about cosmic rays and detectors as well as how to program Arduino to communicate with a custom chip.”

    It can also be used for outreach purposes in some special event, such as the CERN open days.

    Matthew, on his side, is already profiting of this project, since he is enhancing his programming skills and is learning about physics and electronics. At the fourth year of his undergraduate engineering course at the University of Malta, Matthew applied to the CERN summer student programme attracted by the perspective of spending some time at CERN and because he was willing to have an experience outside his country.

    “I think I will continue my studies enrolling in a Master’s and a PhD programme, but I am not sure about the topic yet,” he declares. “Actually, at high-school I studied mainly chemistry and biology, then at the University I switched to engineering. I think I will continue with something that incorporates programming and electronics, such as robotics”.

    See the full article here .

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  • richardmitnick 2:18 pm on July 3, 2017 Permalink | Reply
    Tags: A new Fast Interaction Trigger (FIT) system, , ALICE detector upgrades enter production phase, ALICE will be able to further investigate the properties of Quark-Gluon Plasma in pp p-Pb and Pb-Pb collisions, ALPIDE pixel chips will guarantee higher granularity and reduced material budget, CERN ALICE, Introduction of a Muon Forward Tracker (MFT), Replacement of the Inner Traking System (ITS), Run 3 of LHC after the two-year long shut down (LS2) that will start at the end of 2018, Upgrade of the Time Projection Chamber (TPC)   

    From ALICE at the LHC at CERN: “ALICE detector upgrades enter production phase” 

    CERN
    CERN New Masthead

    16 June 2017
    Virginia Greco

    The activities for the upgrade of the ALICE detector and instrumentation proceed on schedule. Validated the prototypes, now the components have to be produced, assembled and tested in order to be ready for installation during the next 2-year long shut down of LHC (2019-2020).

    1
    Scheme of the upgrade of the ALICE detector. [From Zhongbao Yin’s talk at the LHCP2017 Conference]

    While the extended end-of-year shutdown has concluded and the LHC has been switched on again, the activities for the upgrade of the ALICE detector have entered a new phase. The prototypes of the various new components have been tested and validated, so that now production can start.

    This major upgrade will increase the performance of the detector in order to fully exploit the higher interaction rate of about 50 kHz that is expected in Run 3 of LHC, after the two-year long shut down (LS2) that will start at the end of 2018.

    The upgraded ALICE detector will be able to cope with the increased readout rate and will provide better vertex resolution and tracking efficiency at low pT. At the same time, it will preserve its excellent particle identification properties.

    The upgrade programme foresees the replacement of the Inner Traking System (ITS) associated to a new beam pipe with a smaller diameter, the introduction of a Muon Forward Tracker (MFT), the upgrade of the Time Projection Chamber (TPC), and the substitution of the V0 and T0 detectors with a new Fast Interaction Trigger (FIT) system. The readout electronics has also been partially redesigned, together with the Central Trigger Processor (CTP) and the DAQ and Offline Data systems.

    The new ITS will be a 7-layer barrel structure made of carbon fiber and equipped with dedicated silicon pixel sensors (ALPIDE), replacing the previous 6-layer detector that used strip, drift and pixel sensors. Being smaller (approximately 30 um x 30 um), thinner (50 um on the inner barrel and 100 um on the outer) and monolithic (sensor and readout chip are integrated in the same silicon structure), the ALPIDE pixel chips will guarantee higher granularity and reduced material budget. As a result, the track position resolution at the primary vertex will be improved by a factor of 3 with respect to the present detector.

    The ALPIDE chip is employed as well in the Muon Forward Tracker (MFT), which is a new vertex detector for muons; combined with the existing Muon Spectrometer, it will allow precise identification of secondary vertices and better mass resolution. Composed of 5 disks of silicon pixel detectors, it will be placed between the central barrel detector and the hadron absorber of the Muon Spectrometer.

    The upgrade of the TPC involves replacing the multi-wire chambers, which limit the event readout rate to 3.5 kHz, with quadruple-GEM chambers designed to minimize ion back-flow and to allow continuous, untriggered readout. New front-end electronics will be also needed. The new TPC will be able to operate at 50 kHz preserving its current performance in terms of tracking, momentum resolution and particle identification.

    The FIT will be dedicated to forward trigger and to the measurement of a number of parameters, including luminosity, collision time, as well as multiplicity and centrality of heavy ion collisions. This new detector, which will replace the existing V0 and T0, will consist of two arrays of Cherenkov radiators, equipped with micro-channel plate detectors and photomultipliers, and of a single, large-size scintillator ring. The FIT will provide larger acceptance and finer segmentation than the present two, without compromising the time resolution.

    As a consequence of the increased luminosity and interaction rate of LHC, a significantly larger amount of data will have to be processed and selected. Thus, a new Central Trigger Processor and a powerful data processing system integrating some online and offline functionalities have been designed as well.

    With this upgraded detector and instrumentation, ALICE will be able to further investigate the properties of Quark-Gluon Plasma in pp, p-Pb and Pb-Pb collisions. In particular, the goal for next runs is to perform high-precision measurements that will shed light on thermodynamics, evolution and flow of the QGP, as well as on parton interactions with the medium.

    See the full article here .

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  • richardmitnick 2:18 pm on June 18, 2017 Permalink | Reply
    Tags: , , CERN ALICE, First collisions of 2017 in ALICE: ready to go, , , ,   

    From ALICE: “First collisions of 2017 in ALICE: ready to go” 

    CERN
    CERN New Masthead

    16 June 2017
    Virginia Greco

    1
    No image caption or credit

    After the long winter shut-down, on May 23 the first proton-proton collisions with stable beams of 2017 were delivered by LHC and detected by the four experiments. The ALICE detector was fully operative and took great snapshots of these collisions (as the event display in the picture).

    The accelerator is now in the intensity ramp-up phase: it started injecting only few bunches and is gradually increasing the number in subsequent fills. It is expected to reach the nominal working conditions towards the beginning of July.

    In reality, the very first collisions were delivered a week before the official date, but they were not in optimal conditions, since the beams were not stable. During this phase, which is called ‘quiet beam’, the experts of LHC perform tests and make adjustments to the various components of the accelerator.

    ALICE used the quiet beam collisions to perform some performance tests, in particular on the forward detectors (AD, V0) and the Electro-Magnetic Calorimeter (EMCAL), but only a minor part of the whole apparatus was switched on. This is because the quiet beam is not totally safe for the instrumentation: when the experts of LHC change the settings of the machine and make adjustments, there is the risk of beam losses hitting directly the detectors, and thus damaging them. In particular, the parts that need to stay off are those closest to the beam line, such as parts of the inner tracking system and the gas detectors.

    When collisions with stable beams were delivered, ALICE started its data-taking programme. The LHC ramp-up plan started with three circulating bunches per beam, and moved on to about 12, 75, 300, 600.

    Even if at the beginning the collision rate was very low, a number of operations could be performed, such as a trigger alignment scan for the pixel detector and a high-voltage scan for the V0 and AD sub-detectors to find the optimal work voltage.

    In order to have precise information on the alignment of the central barrel detectors, data were taken with different polarities of the dipole and the solenoid (specifically, minus-minus, plus-plus and no magnetic fields). This information will be used to reconstruct the data that will be collected along the whole year.

    Following the requirements of some physics group, run of data taking at low rate – with the whole detector on – were also performed, as well as at high interaction rate (150kHz, the nominal one) with the Time Projection Chamber (TPC). This was particularly important, since during the shut-down the gas mixture filling the TPC was changed from Ar-CO2 to Ne- CO2-N2. In this test, the detector showed high performance, as expected.

    Finally, during the 300-bunches fill ALICE took data with a reduced (halved) magnetic field of the solenoid, since these conditions are recommended to study the low mass di-muon spectrum.

    “The restart has been great,” comments Grazia Luparello, run coordinator of ALICE, “in just a few fills of the accelerator we managed to perform all the tests and the special data taking included in our programme; we are satisfied and ready to go for physics”.

    See the full article here .

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  • richardmitnick 1:10 pm on May 19, 2017 Permalink | Reply
    Tags: , CERN ALICE, , Installing new equipment in preparation for the LHC Run 3 upgrade., ,   

    From ALICE: “Installing new equipment in preparation for the LHC Run 3 upgrade.” 

    CERN
    CERN New Masthead

    Installing new equipment in preparation for the LHC Run 3 upgrade.

    1

    The big cube on the back (the one with the door at the corner carrying the “blue man” sticker) is the clean room where ALICE detectors are assembled in dust-free environment. All the material that enters in that room has to be cleaned beforehand and people going inside it must wear protective clothing (to avoid bringing dust into the room).

    The boxes in front of the room, including the Air Conditioning unit that was installed yesterday, provide the services that are needed in the Clean Room.

    For reference, the AC unit is up to ISO 8 standard (https://www.mssl.ucl.ac.uk/…/clean…/cr_standards.html…).

    The Clean Room will be used to assemble the new Time Projection Chamber (TPC) which will be installed inside the L3 magnet during Long Shutdown 2 (mid 2018 – end 2019).

    See the full article here .

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  • richardmitnick 2:25 pm on April 24, 2017 Permalink | Reply
    Tags: , CERN ALICE, , , ,   

    From Symmetry: “A tiny droplet of the early universe?” 

    Symmetry Mag

    Symmetry

    04/24/17
    Sarah Charley

    Particles seen by the ALICE experiment hint at the formation of quark-gluon plasma during proton-proton collisions. [ALREADY COVERED WITH AN ARTICLE FROM CERN HERE.]

    1
    Mona Schweizer, CERN

    About 13.8 billion years ago, the universe was a hot, thick soup of quarks and gluons—the fundamental components that eventually combined into protons, neutrons and other hadrons.

    Scientists can produce this primitive particle soup, called the quark-gluon plasma, in collisions between heavy ions. But for the first time physicists on an experiment at the Large Hadron Collider have observed particle evidence of its creation in collisions between protons as well.

    The LHC collides protons during the majority of its run time. This new result, published in Nature Physics by the ALICE collaboration, challenges long-held notions about the nature of those proton-proton collisions and about possible phenomena that were previously missed.

    “Many people think that protons are too light to produce this extremely hot and dense plasma,” says Livio Bianchi, a postdoc at the University of Houston who worked on this analysis. “But these new results are making us question this assumption.”

    Scientists at the LHC and at the US Department of Energy’s Brookhaven National Laboratory’s Relativistic Heavy Ion Collider, or RHIC, have previously created quark-gluon plasma in gold-gold and lead-lead collisions.

    BNL RHIC Campus

    BNL/RHIC Star

    BNL RHIC PHENIX

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    CERN LHC Tunnel


    CERN LHC

    In the quark gluon plasma, mid-sized quarks—such as strange quarks—freely roam and eventually bond into bigger, composite particles (similar to the way quartz crystals grow within molten granite rocks as they slowly cool). These hadrons are ejected as the plasma fizzles out and serve as a telltale signature of their soupy origin. ALICE researchers noticed numerous proton-proton collisions emitting strange hadrons at an elevated rate.

    “In proton collisions that produced many particles, we saw more hadrons containing strange quarks than predicted,” says Rene Bellwied, a professor at the University of Houston. “And interestingly, we saw an even bigger gap between the predicted number and our experimental results when we examined particles containing two or three strange quarks.”

    From a theoretical perspective, a proliferation of strange hadrons is not enough to definitively confirm the existence of quark-gluon plasma. Rather, it could be the result of some other unknown processes occurring at the subatomic scale.

    “This measurement is of great interest to quark-gluon-plasma researchers who wonder how a possible QGP signature can arise in proton-proton collisions,” says Urs Wiedemann, a theorist at CERN. “But it is also of great interest for high energy physicists who have never encountered such a phenomenon in proton-proton collisions.”

    Earlier research at the LHC found that the spatial orientation of particles produced during some proton-proton collisions mirrored the patterns created during heavy-ion collisions, suggesting that maybe these two types of collisions have more in common than originally predicted. Scientists working on the ALICE experiment will need to explore multiple characteristics of these strange proton-proton collisions before they can confirm if they are really seeing a miniscule droplet of the early universe.

    “Quark-gluon plasma is a liquid, so we also need to look at the hydrodynamic features,” Bianchi says. “The composition of the escaping particles is not enough on its own.”

    This finding comes from data collected the first run of the LHC between 2009 and 2013. More research over the next few years will help scientists determine whether the LHC can really make quark-gluon plasma in proton-proton collisions.

    “We are very excited about this discovery,” says Federico Antinori, spokesperson of the ALICE collaboration. “We are again learning a lot about this extreme state of matter. Being able to isolate the quark-gluon-plasma-like phenomena in a smaller and simpler system, such as the collision between two protons, opens up an entirely new dimension for the study of the properties of the primordial state that our universe emerged from.”

    Other experiments, such as those using RHIC, will provide more information about the observable traits and experimental characteristics of quark-gluon plasmas at lower energies, enabling researchers to gain a more complete picture of the characteristics of this primordial particle soup.

    “The field makes far more progress by sharing techniques and comparing results than we would be able to with one facility alone,” says James Dunlop, a researcher at RHIC. “We look forward to seeing further discoveries from our colleagues in ALICE.”

    See the full article here .

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    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 1:25 pm on April 24, 2017 Permalink | Reply
    Tags: , CERN ALICE, , New ALICE results show novel phenomena in proton collisions, , , , Strange quark   

    From ALICE at CERN: “New ALICE results show novel phenomena in proton collisions” 

    CERN
    CERN New Masthead

    CERN ALICE Icon HUGE

    24 Apr 2017.
    Harriet Kim Jarlett

    1
    As the number of particles produced in proton collisions (the blue lines) increase, the more of these so-called strange hadrons are measured (as shown by the orange to red squares in the graph) (Image: ALICE/CERN)

    In a paper published today in Nature Physics , the ALICE collaboration reports that proton collisions sometimes present similar patterns to those observed in the collisions of heavy nuclei. This behaviour was spotted through observation of so-called strange hadrons in certain proton collisions in which a large number of particles are created. Strange hadrons are well-known particles with names such as Kaon, Lambda, Xi and Omega, all containing at least one so-called strange quark. The observed ‘enhanced production of strange particles’ is a familiar feature of quark-gluon plasma, a very hot and dense state of matter that existed just a few millionths of a second after the Big Bang, and is commonly created in collisions of heavy nuclei. But it is the first time ever that such a phenomenon is unambiguously observed in the rare proton collisions in which many particles are created. This result is likely to challenge existing theoretical models that do not predict an increase of strange particles in these events.

    “We are very excited about this discovery,” said Federico Antinori, Spokesperson of the ALICE collaboration. “We are again learning a lot about this primordial state of matter. Being able to isolate the quark-gluon-plasma-like phenomena in a smaller and simpler system, such as the collision between two protons, opens up an entirely new dimension for the study of the properties of the fundamental state that our universe emerged from.”

    The study of the quark-gluon plasma provides a way to investigate the properties of strong interaction, one of the four known fundamental forces, while enhanced strangeness production is a manifestation of this state of matter. The quark-gluon plasma is produced at sufficiently high temperature and energy density, when ordinary matter undergoes a transition to a phase in which quarks and gluons become ‘free’ and are thus no longer confined within hadrons. These conditions can be obtained at the Large Hadron Collider by colliding heavy nuclei at high energy. Strange quarks are heavier than the quarks composing normal matter, and typically harder to produce. But this changes in presence of the high energy density of the quark-gluon plasma, which rebalances the creation of strange quarks relative to non-strange ones. This phenomenon may now have been observed within proton collisions as well.

    In particular, the new results show that the production rate of these strange hadrons increases with the ‘multiplicity’ – the number of particles produced in a given collision – faster than that of other particles generated in the same collision. While the structure of the proton does not include strange quarks, data also show that the higher the number of strange quarks contained in the induced hadron, the stronger is the increase of its production rate. No dependence on the collision energy or the mass of the generated particles is observed, demonstrating that the observed phenomenon is related to the strange quark content of the particles produced. Strangeness production is in practice determined by counting the number of strange particles produced in a given collision, and calculating the ratio of strange to non-strange particles.

    Enhanced strangeness production had been suggested as a possible consequence of quark-gluon plasma formation since the early eighties, and discovered in collisions of nuclei in the nineties by experiments at CERN’s Super Proton Synchrotron.

    CERN Super Proton Synchrotron

    Another possible consequence of the quark gluon plasma formation is a spatial correlation of the final state particles, causing a distinct preferential alignment with the shape of a ridge. Following its detection in heavy-nuclei collisions, the ridge has also been seen in high-multiplicity proton collisions at the Large Hadron Collider, giving the first indication that proton collisions could present heavy-nuclei-like properties. Studying these processes more precisely will be key to better understand the microscopic mechanisms of the quark-gluon plasma and the collective behaviour of particles in small systems.

    The ALICE experiment has been designed to study collisions of heavy nuclei. It also studies proton-proton collisions, which primarily provide reference data for the heavy-nuclei collisions. The reported measurements have been performed with 7 TeV proton collision data from LHC run 1.

    See the full article here .

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  • richardmitnick 2:30 pm on February 14, 2017 Permalink | Reply
    Tags: , , CERN ALICE, ,   

    From CERN ALICE: “QGP: 17 years after the public announcement…” 

    CERN
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    CERN ALICE Icon HUGE

    31 January 2017
    Virginia Greco

    Interview with Luciano Maiani, DG of CERN from 1999 to 2003, who gave the announcement talk of the discovery of QGP at the SPS.

    CERN  Super Proton Synchrotron
    CERN Super Proton Synchrotron

    3
    About 25 years after its first theoretical prediction, the new state of matter called quark-gluon plasma (QGP) was observed at CERN’s SPS. The public announcement was made on the 10th of February 2000 by Luciano Maiani, Director General of CERN back then. At the event organized by ALICE to celebrate the 30-year anniversary of the first heavy-ion collisions at the SPS, Maiani gave his account of this piece of history of physics.

    We had an interview with him after the seminar.

    After one year of mandate as DG of CERN you had the honour and the responsibility to announce that evidence of the existence of QGP had been found at the SPS. How did you live these happenings?

    At that time I was not an expert in heavy ion physics, because I hadn’t worked in the field. Nevertheless, I was aware of the phase transition issue and of the two existing visions about what happens to nuclear matter at very high temperature. On one side there was the theory that matter would break down into a gas of quarks and gluons (and temperature could be freely increased), on the other side the model of Hagedorn about the existence of an upper limit of the temperature reachable, which could be estimated from the hadron spectrum to be 170-180 MeV.

    With the development of QCD it was possible to combine these two models. In particular, in 1975 Nicola Cabibbo and Giorgio Parisi suggested that the Hagedorn limit temperature is just the critical temperature of a phase transition from a gas of hadrons, made of confined quarks, to a gas of deconfined quarks and gluons (the QGP). These works had convinced the experts in the field.

    When the moment came to decide whether to make a public announcement about what the SPS had found, I discussed with many of the people involved, such as Claude Detraz, who was Director for Fixed Target and Future Programmes during my mandate, Reinhard Stock and Hans Specht. After examining the data and collecting opinions, I concluded that we had convincing signals that what we were observing was indeed the quark-gluon plasma.

    But the public announcement was cautious, wasn’t it? Was there still some doubt?

    I think that the announcement was quite clear. I have the text of it with me, it reads: “The data provide evidence for colour deconfinement in the early collision stage and for a collective explosion of the collision fireball in its late stages. The new state of matter exhibits many of the characteristic features of the theoretically predicted Quark-Gluon Plasma.” The key word is “evidence”, not discovery, and the evidence was there, indeed.

    In the talk I gave at that time I also described the concept of quark deconfinement using an analogy with the snow on the Jura Mountain, which I particularly like. We can consider a quark as a skier: when the temperature is not very low, on the mountain there are only patches of snow in which the skier can move. When the temperature decreases and the snow increases, the skier can move along bigger and bigger spaces, up to a point where he or she can freely sweep long distances. The same can be said for a quark confined in a hadron (the patch), which becomes free when temperature increases.

    Of course at that moment the idea still popular was that we were dealing with a phase transition to a gaseous state in which quarks and gluons would be asymptotically free. Later RHIC showed that the situation is more complicated and that this new state is much more like a liquid with very low viscosity rather than like a gas.

    The announcement came just a few months before the start of the programme of RHIC. Were there some polemics about this “timing”?

    3
    The Solenoidal Tracker at the Relativistic Heavy Ion Collider (RHIC)

    We were almost at the conclusion of a long and accurate experimental programme at the SPS, so making a summing up was needed. In addition, as I said, we thought there were the elements for a public announcement. And this has been proved right by later experiments.

    Somebody thought that it would make RHIC, which was going to enter in operation, appear useless. But that was not the case, since much more was left to study. Indeed in the same announcement talk I said: “the higher energies of RHIC and LHC are needed to complete the picture and provide a full characterization of the Quark-Gluon Plasma”.

    In your opinion, what is the future of this branch of research?

    Well, there are still many open problems, things that need to be studied further.

    It is very important to explore the properties of this new state of matter and the connected phenomena, to get a more precise physical picture of the new state.

    Personally, I think that there is also another possible line of research in this field: to study the production of those exotic hadronic resonances that are not included in the scheme of baryons and mesons (i.e. three quarks or quark-antiquark structures). These resonances have been observed in CMS and LHCb in pp collisions, and it would be interesting to study how they are produced in heavy-ion collisions. It could give us indications about what these objects are, tell us if they are molecules made of colourless hadrons or new states which are configurations of quarks and antiquarks (different from mesons) that include subcomponents connected by colour bounds.

    ALICE could provide an important contribution to this research. It is not easy to observe such exotic states in heavy-ion collisions but I think it is worth trying.

    4
    No image caption. No image credit.

    An iconic view of the universe
    Inflationary Universe. NASA/WMAP
    Inflationary Universe. NASA/WMAP

    See the full article here .

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  • richardmitnick 11:57 am on December 16, 2016 Permalink | Reply
    Tags: , CERN ALICE, , , , , Reinhard Stock   

    From CERN ALICE: “The entry of heavy-ion physics in the high-energy sanctuary” 

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    06 December 2016
    Reinhard Stock

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    Reinhard Stock
    After the welcome address, the first who came on stage at the 30 Years of Heavy Ions celebration at CERN was Reinhard Stock, who told the story of the birth of heavy-ion physics and of its “entry in the high-energy sanctuary”, i.e. CERN.

    At that time – the late 1970’s and early 1980’s – Stock was working on the Streamer Chamber experiment, set at the Laurence Berkley National Laboratory (LBNL) in US, in which high energy heavy-ion reactions were studied and collision events were analyzed by eye on scan-tables (“It took two or three hours to analyze just an event!” Stock commented). In 1980 the Bevatron accelerator at LBNL had been upgraded to work with heavy-ion injection from the the SuperHILAC linear accelerator, and the complex of the two had been called Bevalac.

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    Inside the Bevatron. Credit: Lawrence Berkeley National Lab.

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    Inside the Super HILAC
    Super HILAC (Super Heavy Ion Linear Accelerator) was one of the first particle accelerators that could accelerate heavier elements to “atom-smashing” speeds. The device was built in 1972 and played a significant role in four decades of scientific research at Lawrence Berkeley National Laboratory. In addition to being the launchpad for a variety of major experiments, the Super HILAC was crucial in the discovery of five superheavy elements. In this photo, Lawrence Berkeley National Laboratory’s Bob Stevenson and Frank Grobelch are sitting inside the Super HILAC’s poststripper. The maze of piping behind them is meant to circulate cooling water through the accelerator. | Photo courtesy of Lawrence Berkeley National Laboratory. https://energy.gov.

    Under the direction of Hermann Grunder, it was the first universal facility to study relativistic collisions of light or heavy nuclei. Its research programme was oriented to studying the Nuclear Matter Equation of State, which – according to Stock – was “the holy grail of Bevalac’s physics” and was of key importance to understand the structure of neutron stars and supernova dynamics.

    At the beginning of the 1980’s the idea rose to to search for the plasma state of QCD with heavy-ion collisions at the higher CERN energies, so a group of researchers in nuclear and heavy-ion physics (mainly of GSI and LBL, but also of Heidelberg, Marburg and Warsaw) in 1982 wrote a proposal and submitted it to the CERN Proton-Synchrotron Committee, principally under initiative of Bock, Stock and Gutbrod from GSI, and Pugh and Poskanzer from LBNL.

    When and how was heavy-ion physics born?

    The transition from the goal of the nuclear (or hadronic) matter Equation of State to the investigation of deconfined QCD matter with high-energy heavy-ion collisions happened when physicists, both in the environment of the Bevalac experiments and among particle physics groups at CERN and BNL, began to address the question of whether a deconfined (colour conducting plasma) QCD state might be created in very high energy collisions of nuclei. In this situation our 1982 proposal to CERN, which included construction of heavy-ion injection instrumentation at the Proton Synchrotron (PS), set a lot of things rolling.

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    Proton Synchrotron. CERN

    Why did you and your colleagues decide to write this proposal? Why going to CERN?

    The idea to investigate a deconfined state of QCD in very high energy collisions was somehow irresistible to us. The Quark-Gluon Plasma (QGP) state had been postulated theoretically to arise from the newly discovered so-called asymptotic freedom limit of a system of quarks and gluons. This QGP is a much more elementary state than that of the matter we are made of and plays an important role in the early evolution of the Universe because such a state has apparently dominated the attosecond to microsecond era of the Big Bang expansion. Of course, in the early 1980’s the properties of the QGP were not yet known. It has turned out to be fundamental quantum liquid with unexpected properties, very far away indeed from QCD asymptotic freedom. This is the key result of the research we are talking about here.

    Although the idea was already there since the late 1970’s, iit took time to set up the EOS Bevalac experiments, at a more modest energy, and gain experience with the new physics, as well as instrumentation of substantial cost (including providing for funding) novel to the Nuclear Physics community. Most importantly, it soon turned out that even the maximal Bevalac energy did not suffice to create the QCD deconfinement energy. So it was natural to turn to CERN where about tenfold higher center of mass energy was available.

    The proposal was for an experiment at the PS, but it actually ended up at the SPS…

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    The Super Proton Synchrotron. CERN

    Yes and that was a terribly fortunate development of the events. My colleague from MPI Munich, Volker Eckardt, had ignited my interest in QCD deconfinement by suggesting that there was a heritage of potentially useful instrumentation and infrastructure, from former SPS experiments NA5 and NA24, that could be adaptable to QGP research. But these experiments were located in the North extraction area of the SPS. There was a modern Streamer Chamber, as well as a host of calorimetry, plus beam line and other structures, fully intact. Actually it was this prospect that had prompted the 1982 proposal, but we were outsiders to CERN and did not dare to propose an SPS experiment, with much more weightful implication to CERN’s programme, so the experiment called for two PS experiments, one based on the LBL Streamer Chamber experiences, the other on an extended scheme of the GSI – LBL Plastic Ball experiment.

    But the historically most shaking element of our proposal was that GSI and LBL offered to procure a pre-installed and tested new injector complex for heavy ions, consisting of a Gellert-Grenoble ECR ion source bought by GSI, and an LBL-built RFQ preaccelerator. This latter facility proved irresistible to CERN as it invited the idea that other groups at CERN, coming from particle physics background, could also articulate their intentions to participate in QCD plasma research. The combined impact of our interest in inheriting the NA5/24 setup in the North SPS extraction hall and the push of the (North area based) former experiments now preparing for QCD matter physics finally convinced R.Klapisch (then CERN research director) to initiate the launch of a full-fledged SPS programme. In retrospect this was an overwhelmingly constructive development because the CERN SPS nuclear collision research facility provided for the first, crucial inroad into QCD matter physics.

    Oddly enough, though, your proposal was never formally approved, was it?

    It is true, indeed. But from the above you see that this, our initial proposal for PS experiments, was swiftly “washed away” by a complex set of ideas and decision-making at CERN, which also entailed a formal CERN-GSI-LBL agreement to build the new heavy ion injector system. As a personal note – as my talk was about entering the CERN sanctuary from the outside Nuclear Physics community – I included the recollection that the initial young physicists proposing this research to CERN, notably H. Gutbrod and myself, were obviously mostly regarded as “catalysts” in this development, somehow “idiots utiles” for the major good, as was the object of CERN internal deliberations. Indeed we were never received in committee hearings about our planned experiments. However, putting this aside, of course the transformations of our initial proposal were then well taken care of in the ensuing discussion of the resulting SPS experiment programme, and our experiments ended up as NA35 and WA80. As I said, NA35 was the result of MPI Munich joining and providing all the invaluable instrumentation in the North hall, without which I do not know how we would have managed to set up NA35 (if based on Nuclear Physics funding only).

    Following these events, a first generation of experiments was installed at CERN’s SPS and measurements were performed with beams of fully stripped oxygen first and sulphur later. Stock was the leader of the NA35 experiment.

    The second act of this story began with another proposal, dated 1986. In this case the idea was to study lead collisions in the SPS and the proposal went through all the formalities up to reaching approval. It was decided that the upgrade of the infrastructure would be paid with “in kind” contribution by CERN and other eight European agencies.

    Thus, a second generation of experiments was established at the SPS. The follow-up of NA35 was NA49, in which streamer chambers were replaced by Time Projection Chambers (TPC), based on a more recent technology. In addition, an automatic system to analyze the data was developed, since the eye scanning method could not cope with the increased number of collisions.

    How do you feel, now that we are celebrating 30 years of heavy ions, being one of the beginners of this kind of physics?

    I think that intellectually it was a very interesting voyage. At SPS we have learnt a lot both about QCD and about detector technology. Great things came also from RHIC, which has been the world leader in this field in particular in the period from 2000 to 2005.

    BNL RHIC Campus
    BNL/RHIC
    BNL/RHIC

    Then LHC followed in the footsteps of RHIC. At first, remarkably, the QCD matter research was a shared initiative of the two – hitherto essentially separately marching – communities of nuclear and particle physicists. A landmark accomplishment of the open horizon of CERN research! LHC brought a transition from qualitative to quantitative results, much closer to the fundamental goals of determining the transport coefficients of quark matter. And, thus, radiating a sharp stimulus to our theoretical colleagues.

    What can we expect from the next lead-ion runs at LHC?

    First of all, more statistics to have higher confidence levels for already performed measurements. Then, hopefully, something new that could trigger a different theoretical view. It could be something like a generalization of matter under the government of QCD, or going back earlier in time in the reconstruction of the development of matter after the Big Bang, or finding a more fundamental theory of which QCD is some sort of low energy limit. These are our hopes, beyond accumulating more statistics. There is actually a need for a new theoretical paradigm.

    See the full article here .

    Please help promote STEM in your local schools.

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    Meet CERN in a variety of places:

    Cern Courier

    THE FOUR MAJOR PROJECT COLLABORATIONS

    Meet CERN in a variety of places:

    Cern Courier

    THE FOUR MAJOR PROJECT COLLABORATIONS
    ATLAS
    CERN/ATLAS detector

    ALICE
    CERN ALICE New

    CMS
    CERN/CMS Detector

    LHCb

    CERN/LHCb

    LHC

    CERN/LHC Map
    CERN LHC Grand Tunnel

    CERN LHC particles

    Quantum Diaries
    Quantum Diaries

     
  • richardmitnick 4:25 pm on December 6, 2016 Permalink | Reply
    Tags: 2016: an exceptional year for the LHC, , , CERN ALICE, , , ,   

    From CERN: “2016: an exceptional year for the LHC” 

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    CERN

    6 Dec 2016
    Corinne Pralavorio

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    This proton-lead ion collision in the ATLAS detector produced a top quark – the heaviest quark – and its antiquark (Image: ATLAS)

    It’s the particles’ last lap of the ring. On 5 December 2016, protons and lead ions circulated in the Large Hadron Collider (LHC) for the last time. At exactly 6.02am, the experiments recorded their last collisions (also known as ‘events’).

    When the machines are turned off, the LHC operators take stock, and the resulting figures are astonishing.

    The number of collisions recorded by ATLAS and CMS during the proton run from April to the end of October was 60% higher than anticipated. Overall, all of the LHC experiments observed more than 6.5 million billion (6.5 x 1015) collisions, at an energy of 13 TeV. That equates to more data than had been collected in the previous three runs combined.

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    One of the first proton-lead ion collisions at 8.16 TeV recorded by the ALICE experiment. (Image: ALICE/CERN)

    In technical terms, the integrated luminosity received by ATLAS and CMS reached 40 inverse femtobarns (fb−1), compared with the 25fb−1 originally planned. Luminosity, which measures the number of potential collisions in a given time, is a crucial indicator of an accelerator’s performance.

    “One of the key factors contributing to this success was the remarkable availability of the LHC and its injectors,” explains Mike Lamont, who leads the team that operates the accelerators. The LHC’s overall availability in 2016 was just shy of 50%, which means the accelerator was in ‘collision mode’ 50% of the time: a very impressive achievement for the operators. “It’s the result of an ongoing programme of work over the last few years to consolidate and upgrade the machines and procedures,” Lamont continues.

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    An event recorded by the CMS experiment during the LHC’s proton-lead ion run for which no fewer than 449 particles tracks were reconstructed. (Image: CMS/CERN)

    For the last four weeks, the machine has turned to a different type of collision, where lead ions have been colliding with protons. “This is a new and complex operating mode, but the excellent functioning of the accelerators and the competence of the teams involved has allowed us to surpass our performance expectations,” says John Jowett, who is in charge of heavy-ion runs.

    With the machine running at an energy of 8.16 TeV, a record for this assymetric type of collision, the experiments have recorded more than 380 billion collisions. The machine achieved a peak luminosity over seven times higher than initially expected, as well as exceptional beam lifetimes. The performance is even more remarkable considering that colliding protons with lead ions, which have a mass 206 times greater and a charge 82 times higher, requires numerous painstaking adjustments to the machine.

    The physicists are now analysing the enormous amounts of data that have been collected, in preparation for presenting their results at the winter conferences.

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    A proton-lead ion collision recorded by the LHCb experiment in the last few days of the LHC’s 2016 run. (Image: LHCb)

    Meanwhile, CERN’s accelerators will take a long break, called the Extended Year End Technical Stop (EYETS) until the end of March 2017. But, while the accelerators might be on holiday, the technical teams certainly aren’t. The winter stop is an opportunity to carry out maintenance on these extremely complex machines, which are made up of thousands of components. The annual stop for the LHC is being extended by two months in 2017 to allow more major renovation work on the accelerator complex and its 35 kilometres of machines to take place. Particles will return to the LHC in spring 2017.

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    The integrated luminosity of the LHC with proton-proton collisions in 2016 compared to previous years. Luminosity is a measure of a collider’s efficiency and is proportional to the number of collisions. The integrated luminosity achieved by the LHC in 2016 far surpassed expectations and is double that achieved at a lower energy in 2012. (Image : CERN)

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Meet CERN in a variety of places:

    Cern Courier

    THE FOUR MAJOR PROJECT COLLABORATIONS

    ATLAS
    CERN ATLAS New

    ALICE
    CERN ALICE New

    CMS
    CERN CMS New

    LHCb
    CERN LHCb New II

    LHC

    CERN LHC Map
    CERN LHC Grand Tunnel

    CERN LHC particles

    Quantum Diaries

     
  • richardmitnick 5:09 pm on November 14, 2016 Permalink | Reply
    Tags: , CERN ALICE, , ,   

    From Alice at CERN: “Proton-lead collision at 5.02 TeV as seen by ALICE” 

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    1
    ALICE-EVENTDISPLAY-2016-011-1

    One of the first proton-lead events at 5.02 TeV as seen by ALICE in November 2016. The event comes from fill 5506 with 189 colliding bunches at an interaction rate of 17 kHz.

    Date: 11-11-2016

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Meet CERN in a variety of places:

    Cern Courier

    THE FOUR MAJOR PROJECT COLLABORATIONS
    ATLAS
    CERN/ATLAS detector

    ALICE
    CERN ALICE New

    CMS
    CERN/CMS Detector

    LHCb

    CERN/LHCb

    LHC

    CERN/LHC Map
    CERN LHC Grand Tunnel

    CERN LHC particles

    Quantum Diaries

     
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