Tagged: CERN ALICE Toggle Comment Threads | Keyboard Shortcuts

  • richardmitnick 10:48 am on March 31, 2015 Permalink | Reply
    Tags: , CERN ALICE, , ,   

    From ALICE at CERN: “Interview with Savas Dimopoulos” 

    CERN New Masthead

    CERN ALICE Icon HUGE

    24 March 2015
    Panos Charitos

    1
    Savas Dimopoulos

    Savas Dimopoulos, professor at Stanford University, is searching for answers to some of the most profound mysteries of nature. In this interview we discuss the recent findings of the LHC and his expectations from future HEP experiments, the quest for “truth” that drives our scientific endeavours, as well as the relation between science and art.

    P.C. Why did you decide to become a physicist?

    S.D. What attracted me to physics and mathematics was the truth of the statements made in these disciplines. This dates back to my childhood. I was born in Constantinople, and my family moved to Athens when I was twelve. It was a time of great turmoil and I witnessed political tensions, people on the left and on the right were expressing opposing arguments that both seemed reasonable to me.

    I decided to go into a discipline that seeks the absolute truth: a truth that does not depend on the eloquence of the speaker. That limited my choices to mathematics and physics. I finally decided to study physics, as I had doubts about the certainty of truth in mathematics; in physics, in addition to mathematical proofs, the experiments add an extra layer of certainty that brings us closer to the truth.

    I was enamoured of the fact that through physics we can explain all phenomena from very few principles, as nature turns out to be exceedingly simple in principles and exceedingly complex in phenomena. The laws of nature can be written down on a single piece of paper and explain everything that we have seen so far in the universe. This is the magic of theory: it compactifies facts and reduces them to a handful of principles from which everything can be derived.

    P.C. You referred to the balance between experiment and theory, but it somehow seems that you were more intrigued by the latter. What attracted you to what is now called theoretical physics?

    S.D. In the beginning, I had not decided whether I was going to be a theorist or an experimentalist. I went to a high-school without laboratories in Greece. The first time I had the chance to work in a laboratory was as a student at the university. That’s when I realised that I lacked the talent to be an experimentalist and felt that I was better in theory.

    At the time, I thought that the truth of mathematics exists only in our human brains, whereas physics is independent of human existence and therefore the ultimate discipline for the search for the absolute and most important truths. Plato believed that mathematical reality in some sense exists in the so-called platonic world of ideas, where objects on earth have their idealized counterparts. A sphere, for example, is never perfect in real life but in the platonic world, which we call mathematics, perfectly round spheres exist. As mathematical entities are not necessarily realized in nature, I felt uncomfortable as a child to just focus on mathematics. However, I think that it is an amazing language. The rules are well defined and once you pose the right question anybody can follow the steps to find the correct answer, even computers.

    P.C. Do you think that, besides experiments, mathematics is also another way to control our theories?

    S.D. You are absolutely right. Mathematics is crucial for controlling the truth because it is not a random game. You start with a few axioms, and, as long as they are self-consistent, you can produce theorems and derive truths that follow from them. In that sense, mathematics is very important to theoreticians, as mathematical consistency is a huge constraint on our theoretical ideas.

    P.C. What is the situation today in theoretical physics, following the recent results of the LHC?

    S.D. We are now standing at a crossroads, with one path leading to naturalness and the other to the multiverse or something else. It is very exciting, we are testing if the idea of naturalness can be applied to the hierarchy problem – which is the disparity between the weak and gravitational forces. In the next several years, the LHC will be the epicentre of excitement, because it is testing such a fundamental principle and such a dichotomy in physics.

    In the light of these data, physicists react in different ways. As I often emphasize in my recent talks, the state of beyond Standard Model physics after the LHC8 can be compared to headless chickens running in all possible directions.

    4
    Standard Model of Particle Physics. The diagram shows the elementary particles of the Standard Model (the Higgs boson, the three generations of quarks and leptons, and the gauge bosons), including their names, masses, spins, charges, chiralities, and interactions with the strong, weak and electromagnetic forces. It also depicts the crucial role of the Higgs boson in electroweak symmetry breaking, and shows how the properties of the various particles differ in the (high-energy) symmetric phase (top) and the (low-energy) broken-symmetry phase (bottom)

    What is more interesting, headless chickens can live for up to two years; that is also the timescale which we need to get more results from the second run of the LHC. This run will indicate the research that we will pursue in the coming decades.

    2
    Mixed reactions should not frighten us, as they characterize every scientific revolution.

    P.C. Why do you believe there is so much enthusiasm for the search of supersymmetry at the LHC?

    Supersymmetry standard model
    Standard Model of Supersymmetry

    S.D. People are enthusiastic about the possibility of discovering supersymmetry for a number of reasons. In the early 1990s, LEP measured the strengths of the strong and weak electromagnetic interactions and discovered that supersymmetric grand unification is favoured over the non-supersymmetric one. That was a great source of excitement, and theorists looked forward to discovering the super-partners at LEP, LEP 2, or at the LHC. However, no hint of supersymmetry was found after the first collisions at the LHC8 energies.

    CERN LEP
    CERN/LEP

    This story reminds me one of Sherlock Holmes’ stories where he points out “the curious incident of the dog in the night-time”, the incident being that the dog did nothing. In the same way, the absence of supersymmetry at the energies explored so far at the LHC can teach us many things. Supersymmetry is one of the rare ideas that is so important, that even its absence is worth knowing about.

    In addition to that, there is also a sociological aspect to the popularity of supersymmetry: it is an easy theory to work with, and, as a result, it can be tested experimentally in great detail, unlike other alternatives to the hierarchy problem.

    Because of these reasons, the search for supersymmetry is the [?]primary aim of the LHC. In the next years we should have a better idea of the path chosen by nature and we may be talking with enthusiasm about the discovery of the first supersymmetric particle. In the best case scenario, though, our theories will be proven wrong, and we will discover something unanticipated, something truly revolutionary as was the case with quantum mechanics.

    P.C. How did it feel to have your prediction of unification of couplings confirmed by experiment?

    S.D. Having your theory confirmed by experiment feels like a present that you didn’t deserve. When we do science on a day-to-day basis, it’s sort of like a puzzle – this very intricate game with strict rules. It’s like nature is a giant puzzle and mathematics is the language of nature. When a mathematical theory is verified by experiment, you feel awe. It somehow becomes real. You get amazed when you realize that all these games you have been playing are not just games but actually describe nature.

    P.C. Do you think LHC will have the last word or will we also need to design new experiments?

    S.D. There are two directions that we should pursue vigorously. One is to continue with colliders, and go to much higher energy. The other is to design new experiments, as there are some great theoretical ideas that cannot be tested in colliders. For example, some very weakly interacting new particles such as the axion can only be discovered in low energy, tabletop, small-scale experiments.

    There can be forces that are too weak to be discovered in colliders but can nevertheless be observed by testing gravity-like forces in small scale. For example, one can look for deviations from Newton’s law at short distances. In addition to the theoretical importance, many fields (i.e. condensed matter physics, atomic physics, quantum information) have made great progress in precision studies, and these new techniques are begging to be used for fundamental discoveries. They also have the sociological advantage of shorter timescales, typically less than five years, compared to those between two consecutive colliders, which can be decades.

    Another interesting point is that you can roughly separate physics to two periods. Before WWII a number of techniques were used to explore the truth, and the job of theoreticians was both to come up with theoretical ideas and to design experiments to test them. Enrico Fermi and Felix Bloch, for example, did not just do theory; they came up with experiments and, in some cases, even conducted them themselves. After the War, fundamental physics started focusing increasingly on the high energy frontier. This has been a golden road, as the recent discovery of the Higgs shows. Nevertheless, in the long timescale between consecutive colliders, it will be exciting to look for new physics using low energy experiments.

    P.C. Do you think that we still learn something, even when our theories are proven wrong? Is this another step bringing us closer to truth?

    S.D. Absolutely. Truth is both discovering new things and proving that some preconceptions, speculations, or theories are wrong. For example, the idea of the aether seemed plausible at a time, as it was logical to assume that electromagnetic waves need a medium, but it was disproved by the Michelson–Morley experiment. In this case, it was the non-discovery of something that created the big earthquake that led to relativity. Knowing what is false can be as important as knowing what is true.

    3

    P.C. What drives people to formulate new theories and models?

    S.D. One obvious reason is the inconsistency of an existing theory with data. The Standard Model has survived every laboratory test so far and in some cases the validity of its predictions has been tested to 12 decimal precision. It nevertheless fails to explain roughly 95% of our Cosmos. It does not explain Dark Matter or what the origin of Dark Energy is. For the latter, the SM prediction is at least 60 orders of magnitude larger than what we observe it to be. In addition to all this, we eventually run into theoretical problems once we extrapolate the theory to high energies.

    The other motivations are beauty and economy. In the context of physics, the idea of beauty has a relatively precise meaning: it involves symmetry, i.e. the idea that one object appears the same from different perspectives. Economy refers to economy of structure, particles, and parameters. Ideally, there are as few “moving parts” postulated into the theory as possible. In that sense, it is hard to believe that the Standard Model, despite being an amazing theory, is fundamental, because it has over twenty parameters and tens of particles. There must be a more economic version.

    A philosophical, more reflective reason for doing theory is our love of patterns. We are pattern junkies. In our effort to find harmony and conceptually beautiful ways to understand everything at the deepest possible level we do science or create art. Neither of them directly enhances or contributes to our survival probability, but the least important things for our survival are the very things that make us human. For me, art and science are equally important; after a hard day of research I listen to music and find these patterns very relaxing because they are beautiful, and also because I don’t have to actively scrutinise them.

    P.C. Is it possible that at some point we will have answered all the fundamental questions and the scientific endeavours will come to an end?

    S.D. Humans tend to be quite dismissive of the things they learn. There is a famous saying: “Yesterday’s sensation, today’s calibration, tomorrow’s background”. We get bored, and want to move immediately to the next level. For many decades, if not centuries, we have been trying to find a model that explains all the interactions to any conceivable energy that we have experimented with so far. We came up with the Standard Model that may describe almost all known phenomena, but now we want to effectively build a meta-theory that explains the theory itself. However, I am sure that even if we find this meta-theory, we will still come up with more questions. That’s what makes us, as humans, a progressive species: we get excited, we investigate, we discover, and then we get bored and want to get excited again by moving to the next questions.

    P.C. Do you think that the social context is still in favour of researching particle physics and fundamental questions?

    S.D. I think that the public is very interested in fundamental physics. Physics enrollment at universities like Stanford has been going steadily up for the last 15 years at undergraduate and graduate level, despite the fact that there are more competing disciplines, such as biology and information technology. I have also received a lot of positive feedback from the movie Particle Fever.

    However, when the producer approached me ten years ago and told me that he wanted to make a movie about particle physics, I said: “That sounds boring. Who cares about particle physics? You are wasting your time”. “It’s not about particle physics,” he replied, “it’s about particle physicists”. I said: “This is even worse. They are the plainest people on the planet”. I was proven blatantly wrong. And it’s not just Particle Fever. This year there are several movies about science: Gravity, Interstellar, the Imitation Game that is about Alan Turing, and The Theory of Everything about Steven Hawking.

    I think that part of the reason why many more young people don’t go into physics in general and particle physics in particular is that we are not very good at communicating the sense of excitement or even the practical importance of our discoveries to the public. If more effort is put in that direction, it will do wonders to attract bright young people.

    Outreach is a little easier for astrophysicists and cosmologists, because people can lift their eyes to the sky and see what they talk about. Our job, however, is to explain that big entities consist of small parts, which, in a sense, are more fundamental.

    In my experience, two books that I read when I was twelve played a big role in my choosing to be a physicist. One was by Einstein and Infeld and the other was a biography of Einstein by Philipp Frank.

    P.C. Maybe this is the right time to ask you, as a teacher now, what’s your main advice to your students?

    S.D. Enjoy yourself and work on the biggest problems that you can tackle.

    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

    LHC

    CERN LHC New
    CERN LHC Grand Tunnel

    LHC particles

    Quantum Diaries

     
  • richardmitnick 4:44 am on February 20, 2015 Permalink | Reply
    Tags: , CERN ALICE,   

    From CERN ALICE: “ALICE contributes to NASA’s Orion mission” 

    CERN New Masthead

    CERN ALICE Icon HUGE

    16 February 2015
    Panos Charitos

    On Friday, 5 December, NASA’s new Orion spaceship, a capsule built to take humans farther into space than ever before, made its first test flight.

    NASA Orion Spacecraft
    Orion

    The flight marked the first time, since Apollo 17 was launched to the moon in 1972, that a spacecraft built for humans traveled out of low-Earth orbit. Behind the Orion mission there is a flavour of High Energy physics, following in the tradition of synergies between the two fields. More specifically, following the previous success of the Timepix project on the Inernational Space Station (ISS), CERN scientists worked closely with their colleagues at NASA to integrate Timepix into the Orion spaceship.

    CERN TimePix
    TimePix

    Pivotal for this effort was Lawrence Pinsky, who started his career in heavy-ion physics at the NA48 and later NA49 fixed target experiments, before joining the ALICE collaboration. Later, he became involved with NASA’s APOLLO programme, where he was mainly responsible for heavy particle dosimetry. He worked as a postdoc at NASA’s space programme from 1977 to 1990. At that time, he became interested in the simulation of cosmic rays events with the use of GEANT3. His colleagues were also trying to do the same simulations of heavy particles coming from cosmic rays with FLUKA and he joined them. They developed the first Monte Carlo code to simulate transport phenomena of heavy cosmic rays.

    In 2006, when NASA invited him to give a series of lectures, he met Michael Campbell. Strangely, even though they worked in neighbouring buildings, they never had the chance to interact before and realize the possibility of using some of the technologies developed at CERN in space programmes. Michael showed MEDIPIX2 to Pinsky, who immediately realized its potential and demonstrated the chip to his colleagues in Houston.

    CERN MediPix
    MediPix

    During a workshop held by NASA, they advertised it to experts in space radiation and monitoring from all over the world. Various other projects were presented during the workshop, but it was MEDIPIX2 that had the most advantages and outclassed the rest. For the non-experts, the Medipix2 ASIC is a high spatial, high contrast resolving CMOS pixel read-out chip working in single photon counting mode. It can be combined with different semiconductor sensors which convert the X-rays directly into detectable electric signals. This represents a new solution for various X-ray and gamma-ray imaging applications.

    NASA and Huston joined MEDIPIX2 in 2007 and worked actively in the development of the new chip. In 2010, during the Workshop on Radiation Monitoring for the International Space Station – an annual meeting to discuss the scientific definition of an adequate radiation monitoring package and its use by the scientific community on the International Space Station (ISS) – a sequence of lectures on MEDIPIX took place. As the funding necessary for the project to continue was approved, more institutes joined the MEDIPIX2 collaboration that later developed the Timepix chip. The chip was finally installed on ISS in October, and started collecting data and sending them to physicists for analysis.

    1
    Image of the Timepix USB system in operation on the International Space Station (Image Courtesy of NASA).

    The ISS Timepix detectors gather data to characterize the radiation field as a function of time, taking precise measurements of the spectrum of charge and velocity of particles present inside the spacecraft. These Timepix units are compact USB powered devices, based on Medipix technology and controlled via Flight Software that is deployed on existing ISS Computers. Configuration settings can be modified and uploaded from the ground to adjust data-taking parameters on orbit, and minimal crew time is required for deployment and operation. The flight software displays total dose and dose rate based on LET information compiled from individual particle tracks. In addition, full measurement data is saved and downlinked for further analysis.

    2
    Larry Pinsky and undergraduate physics major Christina Stegemoeller, who worked with the group, display the Timepix detector.

    Timepix technology could improve or replace older devices by helping scientists analyse the particles and energy spectrum and then calculate the risks of exposure to heavy-ion radiation. This first trip was an opportunity to gain experience on the use of detectors in space, contributing to the development of the next generation of Timepix.

    During the test flight, mission controllers extensively checked Orion’s systems. The capsule orbited Earth twice, with its second orbit taking it about 5,793 kilometres away from the planet’s surface — 14 times farther than the orbit of the International Space Station.

    NASA scientists were particularly interested in seeing how the spacecraft behaves during important events, such as separations, once in space. Moreover, they also used the approximately 1,200 sensors aboard Orion to monitor the way the capsule’s computers and other technology behave in the harsh space environment. Orion flew through belts of radiation twice (on the way out, and again on the way back to Earth), allowing scientists to see how the spacecraft’s computers behave in a high-radiation environment.

    NASA has plans for another uncrewed mission in 2017 or 2018, which will be the first flight of Orion with the Space Launch System, a mega rocket, still in development. And in 2021, astronauts will travel with Orion and SLS for the first time to test some of the technologies needed for a trip to Mars. This test flight was just the beginning for Orion.

    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

    LHC

    CERN LHC New

    LHC particles

    Quantum Diaries

     
  • richardmitnick 5:45 pm on August 8, 2014 Permalink | Reply
    Tags: , CERN ALICE, , ,   

    Fromk ALICE at CERN: “Inauguration of the new ALICE Run Control Centre” 

    CERN New Masthead

    CERN ALICE Icon HUGE

    12 July 2014
    Federico Ronchetti

    The new ALICE Run Control Centre was inaugurated on the occasion of the collaboration dinner organized at Point 2 during the recent ALICE week. Eight months of restructuring works have reshaped the internal space arrangement of the working areas and fully refurbished all the services such as air conditioning and networking. Almost one hundred collaborators participating to the ALICE week dinner had the chance to enter the ARC for the first time and to get a live experience of the new environment.

    center
    The new ALICE Run Control Centre was inaugurated during the collaboration dinner organized at Point 2.

    In fact the ARC is already being used by several detector groups to carry on the first standalone tests since all the ALICE online systems underwent major improvements in terms of hardware and software requiring now a very intense phase of integration and commissioning. At the same time the ARC was recently used to manage one of the LHC dry runs, in which the machine activity is simulated in order to verify that all the interface systems with the experiment do respond correctly.

    room
    All the ALICE online systems underwent major improvements and the new ARC is getting ready for the second run of the LHC.

    I was personally very happy that our collaborators who signed up for the ALICE dinner could experience the ARC already in an operational phase in addition to appreciating the new ergonomic and neat style. I was also very happy that all the celebration preparation was somewhat kept hidden from me and during a short toast I was “given” as a gift a nice wall handler to hold the beam line technical drawings and that a very stylish and colourful banner with the “Alice Run Control Center” stamp on it appeared from nowhere.

    folks

    I really would like to thank all my colleagues who have helped me in the design of the ARC – Roberto Divià , Gilda Scioli and Ombretta Pinazza and those who followed all the construction and installation phases as Arturo Tauro and once again Roberto Divià. We and the collaboration wanted the ARC so that each of us could contribute to the data taking in the best way, having an efficient and comfortable environment in which for sure we will all spend many hours for the years to come.

    entry
    The entrance to the new ARC; where the journey of discovery begins.

    See the full article here.

    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

    LHC

    CERN LHC New

    LHC particles

    Quantum Diaries

    ScienceSprings relies on technology from

    MAINGEAR computers

    Lenovo
    Lenovo

    Dell
    Dell

     
  • richardmitnick 3:44 am on June 12, 2014 Permalink | Reply
    Tags: , CERN ALICE, , ,   

    From CERN/ALICE: “New PMTs for the ALICE V0-C detector” 

    CERN New Masthead

    CERN ALICE Icon HUGE

    27 May 2014
    Panos Charitos

    During the 2011 proton-proton run it was observed that the efficiency of the PMTs used in the V0 detectors had started to deteriorate. Gerardo Corral says: “At that time time we still had to take data and we could make no intervention but we continued monitoring the performance of the PMTs. Based on a series of measurements, it was clear in 2012 that the effect was probably due to radiation and ageing effects. Our colleagues from the University of Lyon had the chance to remove a number of PMTs from the C side of the V0 detector and make some more detailed testing and measurements.” He continues: “They took out 6 PMTs out of the 32 that are used in the C side and confirmed that their performance was reduced. We knew that we had to deal with this problem and the LS1 was the perfect opportunity”. For the A side of V0 things were more difficult as this side of the detector lies closer to the region of the beam pipe and one had to be very careful to avoid damaging the pipe.”

    The new PMTs arrived near the end of 2013 and were calibrated to be ready for installation. Gerardo explains that this is not just a replacement but also an upgrade as the new PMTs can operate at lower voltage. Reducing the high voltage means that one is also reducing the after-pulse signal which was one of the problems that V0 faced from the first runs. With the replacement of the PMTs the team is able to tackle these two issues: “We have PMTs with better gain that also work with lower voltage and thus reduce the after-pulse effect”.

    team
    Installing the new ALICE PMTs: Solangel Rojas Torres, Ildefonso Leon Monzon, Gerardo Herrera Corral, Arturo Tauro, Werner Riegler, Pieter Ijzermans and Elisa Laudi.

    The installation of the new PMTs took place during the second week of April. All the PMTs on the A side have been replaced and soon the team will start working on replacing the PMTs on the C side of V0. Gerardo explains: “The A side is much more complicated, though it lies 3.3 m from the IP it is still in the beam-pipe. We had to move the V0-A 30 cm away on the region where a very delicate beryllium pipe sits. It was a very slow process during which we took a lot of precautions”. Gerardo Herrera Corral with Ildefonso Leon Monzon and a PhD student Solangel Rojas Torres worked closely with members of the ALICE Technical Management team, namely Werner Riegler, Arturo Tauro, Corrado Gargiulo, Pieter Ijzermans and Elisa Laudi.

    The installation has been very successful since we had no accidents or other causes of delay. The PMTs have now been tested and a very good signal has been measured in all of them.
    PMTs in V0

    The V0 detector is a disk with 42 cm diameter and 2.5 cm thick. It is segmented in 32 cells with each cell linked to readout with optical fibres. When a charged particle crosses the plastic light is produced by scintillation. The fibres take out the light and shift the wavelength from blue to the green part of the spectrum. So green light arrives to the PMTs since their photocathode is more sensitive to these wavelengths. Through photoelectric effect electrons are emitted from the photo-cathode and travel through an elecromagnetic field; they hit a series of dynodes, amplifying the number of electrons and in that way the signal is strengthened.

    team 2

    V0 is very important for ALICE as it provides level – zero triggering. The new PMTs will give better efficiency but also allow reducing the after-pulsing signal. When you hit the window you have a pulse of electrons coming from the dynodes and a few nanoseconds later you have a second pulse that is not authentic but is created in the PMTs due to the ionization of the gas. The vacuum in the PMTs is not perfect; the gas atoms are ionized by the electrons and go to the opposite direction as they have positive charge, they hit again producing more electrons and give a second pulse. This is very bad for triggering as these signals are fake triggers that we have to suppress. With the new PMTs the after-pulse probability is ten times lower and V0 will be better equipped to play its triggering role in the forthcoming run in 2015.

    See the full article here.

    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

    LHC

    CERN LHC New

    LHC particles

    Quantum Diaries


    ScienceSprings is powered by MAINGEAR computers

     
  • richardmitnick 8:56 am on May 22, 2014 Permalink | Reply
    Tags: , CERN ALICE, , ,   

    From CERN ALICE: “ALICE in Quark Matter 2014” 

    CERN New Masthead
    CERN

    CERN ALICE Icon HUGE

    ALICE

    29 April 2014
    Panos Charitos

    The Quark Matter 2014 conference is the twenty-fourth edition of the most prestigious series of international meetings in the field of ultrarelativistic heavy-ion collisions. The meetings bring together theorists and experimentalists committed to understanding the fundamental properties of strongly interacting matter at extreme energy densities. The conditions reached in head-on nuclear collisions at the highest currently available energies correspond to those in primordial matter a few tens of microseconds after the Big Bang. Thus, this type of laboratory research improves our understanding of the early phase of the Universe.

    The first Quark Matter conference took place in 1980 in Darmstadt. Since then, the meetings of this series have been organized approximately every 1.5 years. The recent instances were in Jaipur, India (2008), Knoxville, USA (2009), Annecy, France (2011), and Washington DC, USA (2012). The current meeting brings the conference to Darmstadt again, a place with a long-standing tradition of heavy-ion research and is jointly organized by GSI Helmholtzzentrum für Schwerionenforschung GmbH, Technische Universität Darmstadt, and Universität Heidelberg.

    The scientific programme of Quark Matter 2014 includes numerous topics such as QCD at high temperature and densities, Jets, Open Heavy Flavour and Quarkonia and Electromagnetic Probes. Moreover, the collective dynamics appearing in QGP system and the relations with other strongly coupled systems will be covered along with issues related to correlations and fluctuations and the hadron chemistry. Last but not least, the newest theoretical developments will be discussed during the conference as well as the plans for future experimental facilities and developments in the instrumentation.

    ALICE presents a wealth of scientific results in the upcoming conference with 31 parallel talks and one plenary talk. In addition, in the special poster session ALICE participates with 90 posters reflecting the experiment’s rich scientific programme. The efficient operation of the ALICE detector and the hard work of the ALICE physics working groups were essential ingredients in getting all these results. In the last few weeks, physicists have been very busy with a series of preview and approval sessions during which all the results are scrutinized and the experiment’s last findings are discussed. Last but not least it is worth mentioning that more than one third of the participants in QM2014 are members of the ALICE Collaboration echoing the importance of ALICE studies in the field of ultrarelativistic heavy-ion collisions.

    darm
    Quark Matter 2014 will be hosted in Darmstadium convention center, named in honor of the chemical element with atomic number 110 that was discovered in Darmstadt in 1994.

    The organizers also welcome students’ active participation, which they think is essential for a good conference. Financial support will be provided for a limited number of applicants while a series of introductory lectures will be offered during the Student Day on Sunday, May 18, 2014. More than 300 students have already registered for the event that will be held in GSI and ALICE juniors are encouraged to participate.

    We are looking forward to Quark Matter 2014 and finding out more about the latest developments in our field as the LHC is preparing for the next run at 13 TeV.

    See the full article here.

    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

    LHC

    CERN LHC New

    LHC particles

    Quantum Diaries


    ScienceSprings is powered by MAINGEAR computers

     
  • richardmitnick 1:30 pm on May 8, 2014 Permalink | Reply
    Tags: , CERN ALICE, , , ,   

    From ALICE Matters at CERN: “ALICE T0 detector” 

    CERN New Masthead

    CERN ALICE Icon HUGE
    ALICE

    29 April 2014
    Tatyana Karavicheva [tatiana@inr.ru]

    The T0 detector was designed and built and is operated by a Finnish-Russian team. The members come from two institutes in Finland (University of Jyväskylä and Helsinki Institute of Physics) and three in Russia (Institute for Nuclear Research RAS, Moscow Engineering Physics Institute, Russian Research Centre Kurchatov Institute).

    The current T0 detector consists of two arrays of Cherenkov counters (T0C and T0A) positioned at the opposite sides of the Interaction Point at distances of -70 cm and 370 cm. Each array has 12 cylindrical counters equipped with a quartz radiator and a photomultiplier tube.

    to
    Since its installation during Easter of 2007 T0-C remains inaccessible, hidden under the layers of FMD and ITS detectors and services. Standing from left to right: A.Bogdanov, A.Reshetin, A.Kurepin, and F.Guber.

    Small but important

    T0 is primarily a trigger and timing detector but it also played a crucial role during the high luminosity part of Run 1. Being the first of the ALICE detectors to be turned on, T0 provided a direct feedback to the LHC team enabling them to tune and monitor the collision rate at Point 2. This valuable service allowed the first beams for ALICE to be delivered on time.

    array
    T0-A array after installation in January 2008.

    The fastest got even faster

    During Run 1 T0 was delivering the trigger signals to the CTP just 625 ns after the collision time; being one the fastest of the ALICE detectors. Trigger consolidation for Run 2 requires reduction of that latency to below 425 ns. To achieve such a drastic cut T0 had to relocate the entire electronics from the racks O18-19 to the racks close to the CTP (C33-34) and reroute and shorten the cables. This Herculean task has already been completed and the T0 team is now recommissioning the detector.

    three
    Smiling faces next to the relocated T0 electronics. From left to right: D.Serebryakov, A.Reshetin, T.Karavicheva, and W.H.Trzaska.

    FIT for the future

    The ALICE upgrade for Run 3 is a challenge for all the system. To face that challenge T0, V0 and FMD teams have joined forces and resources to design, build and operate Fast Interaction Trigger (FIT). FIT will provide the functionality of both the T0 and V0 maintaining excellent timing and trigger properties together with the desired centrality and event plane resolution. It will consist of the Cherenkov radiators (T0+) and scintillators (V0+). Both will use common fast electronics, digitization, and readout as outlined in the Chapter 10 of the Readout & Trigger System TDR:

    http://cds.cern.ch/record/1603472

    integ
    Proposed integration of FIT and FMT. T0+ units are shown as rectangular boxes around the beam tube. (Drawing by Corrado Gargiulo.)

    See the full article here.

    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

    LHC

    CERN LHC New

    LHC particles

    Quantum Diaries


    ScienceSprings is powered by MAINGEAR computers

     
  • richardmitnick 12:17 pm on April 22, 2014 Permalink | Reply
    Tags: , CERN ALICE, , ,   

    From ALICE at CERN: “LHC: the world’s largest photon collider” 

    CERN New Masthead

    CERN ALICE Icon HUGE

    28 March 2014
    Joakim Nystrand and Daniel Tapia Takaki

    The CERN Large Hadron Collider (LHC) has worked fantastically well in the past few years, going beyond all expectations. It started its physics programme in 2009 colliding protons at 900 GeV, and then reaching into the Tera electron-volt range supplanting the Fermilab Tevatron accelerator as the most powerful hadron-hadron collider. The LHC was also designed to collide heavy-ions, with the idea of exploring a new energy domain beyond that of RHIC at the Brookhaven National Laboratory. In 2010 this task was completed when the LHC collided lead (Pb) beams at 2.76 TeV, an energy which is more than an order of magnitude larger than that at RHIC.

    lhc

    Although the LHC was not primarily designed to study photon-hadron and photon-photon collisions, they occur in both pp and heavy-ion collisions. The beam energies at the LHC are high enough to make the LHC the most energetic photon source ever built. The protons and ions which are accelerated by the LHC themselves carry an electromagnetic field, which can be viewed as a source of photons. That is, a photon generated by one of these hadrons can interact with another photon (or with a hadron) producing all kinds of particles. Such physics processes are called photon-induced reactions, as they are driven by the interacting photon.

    The appearance of these events stands in sharp contrast to central heavy-ion collisions, where the overlap between the incoming ions is the largest, and thousands of particles are produced. The relevant collisions typically occur at impact parameters of several tens (or even hundreds) of femtometres – cases when the incoming ions barely overlap, and well beyond the range of the strong force.

    jj
    J/ψ candidate in an ultra-peripheral Pb-Pb collision. A dimuon pair in otherwise an empty detector.

    It is worth pointing out that photon-induced processes have by far the largest cross sections in Pb-Pb collisions at the LHC. The total cross section for breaking up one of the nuclei through a photonuclear process is over 200 barns. In most of these reactions the nucleus just breaks up without any particle production. However, the cross section for having at least one photoproduced charged particle inside the main ALICE tracker device (the Time Projection Chamber) acceptance is still substantial, about 4 b. But both these numbers are dwarfed by the total cross section for producing an e+e- pair from an interaction between two photons. This cross section is about 3 million times larger than that for normal hadronic pp collisions.

    A photonuclear interaction that has attracted a lot of interest is exclusive vector meson production. That is, a reaction where only a vector meson is produced in the final state, and nothing else. The large cross section of this process is understood from what is known as Vector Meson Dominance. This means that the photon may fluctuate into a quark-anti-quark pair and, since the photon has spin 1 and negative parity, the fluctuation will most likely be to a Vector Meson. The J/ψ vector meson is one of the particles that is particularly interesting for the heavy-ion community.

    Previously, the HERA experiments at DESY, namely, H1 and ZEUS, studied systematically the photo-production of J/ψ and were able to reach 300 GeV in the centre-of-mass of the photon-proton collision. The proton contains a large number of gluons each carrying a very small fraction of the proton momentum.

    The interaction between hadrons and gluons is governed by the theory of strong interactions called Quantum Chromo-Dynamics (QCD), although there is not yet any known method to predict the gluon density inside a nucleon or a nucleus. Having a good understanding of the proton gluon density is essential for many physics analysis processes sensitive to the strong interaction that governs the interaction between hadrons and gluons.

    There are some theoretical and phenomenological constraints on how the gluon density should behave at high energy but there is not an overall agreement as to what happens when we reach very high energies such as those produced at the LHC. There are several theoretical ideas that can describe what could happen at the LHC photon-hadron energies. Gluon saturation is one of these ideas. J/ψ photoproduction is thought to be sensitive to this in a way that this effect can be easily factorized from other possible mechanics. Nobody knows at what energy gluon saturation phenomena might start to show up in a way that we can distinguish it, but certainly the 1 TeV energy scale is worth studying.

    So far, ALICE has studied photon-photon, photon-lead and photon-proton interactions. At the LHC we are not only reaching the highest energies when colliding photons, but also exploring new kinematic regions that have never been explored before. Some of these photons are indeed very energetic, allowing us to produce collisions at 1 Teraelectronvolt for the first time.

    The ALICE collaboration has recently taken advantage of this effect in a study of coherent photoproduction of J/ψ mesons in Pb-Pb interactions. The J/ψ is detected through its dimuon decay in the muon arm of the ALICE detector [1,2], which also provides the trigger for these events, or in its dielectron or dimuon decay in the central barrel [3]. At the rapidities (y around 3) studied in the muon arm, J/ψ photoproduction is sensitive mainly to the gluon distribution at values of Bjorken-x of about 10–2, whereas at mid-rapidity on probes x ≈ 10 -3. The result from ALICE is that the data favour models that include strong modifications to the nuclear gluon distribution, known as nuclear shadowing.

    During the first running period of the LHC there have been quite a few results on photon-induced collisions. Results with heavy-ion beams have so far come only from ALICE. LHCb has, however, accumulated an impressive statistics of about 100,000 exclusively produced J/ψs in p-p collisions, and CMS have published papers on two-photon interactions in p-p collisions, including a study of W+W- production. In the future, one can expect higher luminosities and thereby probe rarer final states. There are in addition to exclusive vector meson production several things one can look for. These include two-photon production of rare final states, for example γγ→ K0K0, light-by-light scattering, γγ →γγ, and various inclusive photonuclear processes, for example γ +A → jet +X.

    See the full article here.

    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

    LHC

    CERN LHC New

    LHC particles

    Quantum Diaries


    ScienceSprings is powered by MAINGEAR computers

     
  • richardmitnick 6:27 am on April 1, 2014 Permalink | Reply
    Tags: , CERN ALICE, , ,   

    From ALICE Matters at CERN- “LHC: the world’s largest photon collider” 

    CERN New Masthead

    CERN ALICE MATTERS

    CERN ALICE Icon HUGE

    28 March 2014
    Joakim Nystrand and Daniel Tapia Takaki

    The CERN Large Hadron Collider (LHC) has worked fantastically well in the past few years, going beyond all expectations. It started its physics programme in 2009 colliding protons at 900 GeV, and then reaching into the Tera electron-volt range supplanting the Fermilab Tevatron accelerator as the most powerful hadron-hadron collider. The LHC was also designed to collide heavy-ions, with the idea of exploring a new energy domain beyond that of RHIC at the Brookhaven National Laboratory . In 2010 this task was completed when the LHC collided lead (Pb) beams at 2.76 TeV, an energy which is more than an order of magnitude larger than that at RHIC.

    Fermilab Tevatron
    Tevatron at Fermilab

    Brookhaven RHIC
    RHIC at Brookhaven

    LHC Grand Tunnel
    Grand Tunnel of the LHC at CERN

    CERN ALICE Detector
    ALICE

    Although the LHC was not primarily designed to study photon-hadron and photon-photon collisions, they occur in both pp and heavy-ion collisions. The beam energies at the LHC are high enough to make the LHC the most energetic photon source ever built. The protons and ions which are accelerated by the LHC themselves carry an electromagnetic field, which can be viewed as a source of photons. That is, a photon generated by one of these hadrons can interact with another photon (or with a hadron) producing all kinds of particles. Such physics processes are called photon-induced reactions, as they are driven by the interacting photon.

    The appearance of these events stands in sharp contrast to central heavy-ion collisions, where the overlap between the incoming ions is the largest, and thousands of particles are produced. The relevant collisions typically occur at impact parameters of several tens (or even hundreds) of femtometres – cases when the incoming ions barely overlap, and well beyond the range of the strong force.

    pair
    J/ψ candidate in an ultra-peripheral Pb-Pb collision. A dimuon pair in otherwise an empty detector.

    It is worth pointing out that photon-induced processes have by far the largest cross sections in Pb-Pb collisions at the LHC. The total cross section for breaking up one of the nuclei through a photonuclear process is over 200 barns. In most of these reactions the nucleus just breaks up without any particle production. However, the cross section for having at least one photoproduced charged particle inside the main ALICE tracker device (the Time Projection Chamber) acceptance is still substantial, about 4 b. But both these numbers are dwarfed by the total cross section for producing an e+e- pair from an interaction between two photons. This cross section is about 3 million times larger than that for normal hadronic pp collisions.

    A photonuclear interaction that has attracted a lot of interest is exclusive vector meson production. That is, a reaction where only a vector meson is produced in the final state, and nothing else. The large cross section of this process is understood from what is known as Vector Meson Dominance. This means that the photon may fluctuate into a quark-anti-quark pair and, since the photon has spin 1 and negative parity, the fluctuation will most likely be to a Vector Meson. The J/ψ vector meson is one of the particles that is particularly interesting for the heavy-ion community.

    Previously, the HERA experiments at DESY, namely, H1 and ZEUS, studied systematically the photo-production of J/ψ and were able to reach 300 GeV in the centre-of-mass of the photon-proton collision. The proton contains a large number of gluons each carrying a very small fraction of the proton momentum.

    The interaction between hadrons and gluons is governed by the theory of strong interactions called Quantum Chromo-Dynamics (QCD), although there is not yet any known method to predict the gluon density inside a nucleon or a nucleus. Having a good understanding of the proton gluon density is essential for many physics analysis processes sensitive to the strong interaction that governs the interaction between hadrons and gluons.

    There are some theoretical and phenomenological constraints on how the gluon density should behave at high energy but there is not an overall agreement as to what happens when we reach very high energies such as those produced at the LHC. There are several theoretical ideas that can describe what could happen at the LHC photon-hadron energies. Gluon saturation is one of these ideas. J/ψ photoproduction is thought to be sensitive to this in a way that this effect can be easily factorized from other possible mechanics. Nobody knows at what energy gluon saturation phenomena might start to show up in a way that we can distinguish it, but certainly the 1 TeV energy scale is worth studying.

    So far, ALICE has studied photon-photon, photon-lead and photon-proton interactions. At the LHC we are not only reaching the highest energies when colliding photons, but also exploring new kinematic regions that have never been explored before. Some of these photons are indeed very energetic, allowing us to produce collisions at 1 Teraelectronvolt for the first time.

    The ALICE collaboration has recently taken advantage of this effect in a study of coherent photoproduction of J/ψ mesons in Pb-Pb interactions. The J/ψ is detected through its dimuon decay in the muon arm of the ALICE detector, which also provides the trigger for these events, or in its dielectron or dimuon decay in the central barrel. At the rapidities (y around 3) studied in the muon arm, J/ψ photoproduction is sensitive mainly to the gluon distribution at values of Bjorken-x of about 10–2, whereas at mid-rapidity on probes x ≈ 10 -3. The result from ALICE is that the data favour models that include strong modifications to the nuclear gluon distribution, known as nuclear shadowing.

    During the first running period of the LHC there have been quite a few results on photon-induced collisions. Results with heavy-ion beams have so far come only from ALICE. LHCb has, however, accumulated an impressive statistics of about 100,000 exclusively produced J/ψs in p-p collisions, and CMS have published papers on two-photon interactions in p-p collisions, including a study of W+W- production. In the future, one can expect higher luminosities and thereby probe rarer final states. There are in addition to exclusive vector meson production several things one can look for. These include two-photon production of rare final states, for example gg→ K0K0, light-by-light scattering, gg →gg, and various inclusive photonuclear processes, for example g +A → jet +X.

    See the full article, with notes, here.
    See ALICE MATTERS here.

    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

    LHC

    CERN LHC New

    LHC particles

    Quantum Diaries


    ScienceSprings is powered by MAINGEAR computers

     
  • richardmitnick 7:20 am on August 10, 2013 Permalink | Reply
    Tags: , , , , CERN ALICE, , , ,   

    From CERN: “The amazing world of smashed protons and lead ions” 

    CERN New Masthead

    In the CERN Bulletin
    Issue No. 33-35/2013 – Monday 12 August 2013
    Antonella Del Rosso

    alice

    “When a single proton (p) is smashed against a lead ion (Pb), unexpected events may occur: in the most violent p-Pb collisions, correlations of particles exhibit similar features as in lead-lead collisions where quark-gluon plasma is formed. This and other amazing results were presented by the ALICE experiment at the SQM2013 conference held in Birmingham from 21 to 27 July.

    event
    Event display from the proton-lead run, in January 2013. This event was generated by the High Level Trigger (HLT) of the ALICE experiment.

    Jet quenching is one of the most powerful signatures of quark-gluon plasma (QGP) formed in high-energy lead-lead collisions. QGP is expected to exist only in specific conditions involving extremely hot temperatures and a very high particle concentration. These conditions are not expected to apply in the case of less ‘dense’ particle collisions such as proton-lead collisions. ‘When we observe the results of these collisions in ALICE, we do not see a strong particle-jet suppression; however, when studying the most violent p-Pb collisions we observe signatures in particle production characteristic of a hydrodynamic nature,’ explains Mateusz Ploskon from the ALICE collaboration. ‘Indeed, some of the properties of the correlations of particles produced in proton-lead collisions resemble those associated with the formation of QGP in lead-lead collisions.’

    More data is needed to resolve the conundrum but in the meantime the physics community is excited as the phenomena observed in proton-lead collisions could have strong implications for our understanding of the QCD – the theory that describes the interactions of strongly interacting subatomic particles. ‘The p-lead data already provide an extremely useful baseline for the collisions of heavy ions; however, we need more time and more data to understand the intriguing observations from proton-lead collisions – it remains to be seen whether we learn something new about hadronic and nuclear collisions at high energies, and whether these observations have any unexpected implications for our understanding of QGP based on lead-lead collisions,’ says Mateusz.”

    See the full article here.

    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

    LHC

    CERN LHC New

    LHC particles

    Quantum Diaries


    ScienceSprings is powered by MAINGEAR computers

     
  • richardmitnick 10:29 am on July 31, 2013 Permalink | Reply
    Tags: , , , CERN ALICE, , , ,   

    From CERN: “ALICE through a gamma-ray looking glass” 

    CERN New Masthead

    31 July 2013
    Christine Sutton

    “The ALICE experiment at CERN specializes in heavy-ion collisions at the LHC, which can produce thousands of particles. In analysing this maelstrom, the researchers need to know exactly how material is distributed in the detector – and it turns out that the LHC’s simpler proton–proton collisions can help.

    layers
    A gamma-ray view of the layers of the ALICE detector. (Image: ALICE)

    Gamma-rays produced in the proton–proton collisions, mainly from the decays of neutral pions, convert into pairs of electrons and positrons as they fly through matter in the detector. The origin of these pairs can be accurately detected, providing a precise 3D image that includes even the inaccessible innermost parts of the experiment. The process is almost exactly the same as in 1895 when Wilhelm Röntgen produced an X-ray image of his wife’s hand – the inner parts of the body could be seen for the first time without surgery. The main difference lies in the energy of the radiation – ten times greater for the gamma rays in ALICE than for Röntgen’s X-rays. Importantly for the ALICE experiment, it allows the team to check crucial simulations.”

    See the full article here.

    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

    LHC

    CERN LHC New

    LHC particles

    Quantum Diaries


    ScienceSprings is powered by MAINGEAR computers

     
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
Follow

Get every new post delivered to your Inbox.

Join 462 other followers

%d bloggers like this: