Hadron physics ALICE

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The international collaboration ALICE (“A Large Ion Collider Experiment”), of which the eponymous research group of the IP2I in Lyon is a member, aims to study nuclear matter in a state of extremely high temperature, where the deconfinement of hadrons (including protons and neutrons) into plasma of quarks and gluons takes place.

Matter is made up of atoms, themselves made up of electrons surrounding a nucleus of protons and neutrons, the latter being formed of quarks, linked by gluons. No quark or gluon has ever been observed in isolation: they appear to be permanently bonded together and confined in composite particles. At temperatures 100,000 times higher than those at the centre of the Sun, they deconform to form a plasma, which would have existed a few microseconds after the Big Bang. This plasma is predicted by the fundamental theory of strong interaction, Quantum Chromodynamics (QCD), and its study allows us to understand the ultimate organization of matter subject to strong interaction and the very first moments of the universe.

The LHC collides lead ions to recreate conditions similar to those immediately after the Big Bang and form this quark and gluon plasma. For this infinitely small study, a huge detector has been built at the LHC. It is capable of measuring the particles emitted by the plasma as it expands and cools.

Our group has been involved in this construction and in obtaining major results in this field of physics.

The activities of the ALICE group of the IP2I of Lyon are twofold:

Analysis of data collected in proton-proton, proton-nucleus and nucleus-nucleus collisions at the CERN LHC

The physics analyses of the ALICE experiment carried out in the Lyon groups cover a wide range of subjects, from the light quark sector u, d, s with the study of the forward production of low mass vector mesons \rho, \omega and \phi in the dimuonic decay channel, to the heavy quarks sector c and b, with the study of the production of the quarkonium states of the J/\psi and \Lambda families. This analytical work has already led to a number of remarkable results, notably through the study of collective phenomena characterizing the evolution of the J/\psi and \Lambda mesons, namely the appearance of kinematic correlations between the J/\psi meson and light hadrons in high multiplicity proton-Pb collisions, and the observation of elliptical flow of the \Upsilon(1S) meson compatible with zero in Pb-Pb collisions (behavior different from all the other particles studied).

Participation in the construction and operation of the forward vertex trajectograph, the Muon Forward Tracker

The group is also responsible for the construction and operation of the vertex forward trajectograph, the Muon Forward Tracker (MFT), one of the first applications in high energy physics of CMOS silicon pixel sensor technology. The MFT, which will be integrated into the ALICE detector starting with Run3 of the LHC (2021), is designed to enable precise measurement of the details of the vertex region for forward-produced particles, especially muons, whose different topologies and production processes can be studied.

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    1803 documents

    • M. Acciarri, O. Adriani, M. Aguilar-Benitez, S. Ahlen, B. Alpat, et al.. Measurement of Inclusive \omega and \eta' Production in Hadronic Z Decays. Physics Letters B, 1997, 393, pp.465-476. ⟨10.1016/S0370-2693(96)01683-8⟩. ⟨in2p3-00014307⟩
    • M. Bedjidian, F. Bellaiche, B. Cheynis, D. Contardo, O. Drapier, et al.. The NA50 segmented target and vertex recognition system. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1997, 398, pp.180-188. ⟨10.1016/S0168-9002(97)00748-1⟩. ⟨in2p3-00000223⟩
    • M C. Abreu, B. Alessandro, C. Alexa, J. Astruc, C. Baglin, et al.. J/\psi and Drell-Yan cross-sections in Pb-Pb interactions at 158 GeV/c per nucleon. Physics Letters B, 1997, 410, pp.327-336. ⟨10.1016/S0370-2693(97)00914-3⟩. ⟨in2p3-00007505⟩
    • M. Acciarri, O. Adriani, M. Aguilar-Benitez, S. Ahlen, B. Alpat, et al.. Study of the Weak Charged Hadronic Current in b Decays. Physics Letters B, 1997, 393, pp.477-486. ⟨10.1016/S0370-2693(96)01689-9⟩. ⟨in2p3-00000258⟩
    • M. Acciarri, O. Adriani, M. Aguilar-Benitez, S. Ahlen, B. Alpat, et al.. Measurement of D_{s}^{-} \to \tau^{-}\overline{\nu}_\tau and a New Limit for B^- \to \tau^{- }\overline{\nu}_\tau. Physics Letters B, 1997, 396, pp.327-337. ⟨10.1016/S0370-2693(97)00138-X⟩. ⟨in2p3-00000078⟩
    • M. Acciarri, O. Adriani, M. Aguilar-Benitez, S. Ahlen, J. Alcaraz, et al.. Single and multi-photon events with missing energy in e^+ e^- collisions at 161 GeV \sqrt{s} 172 GeV. Physics Letters B, 1997, 415, pp.299-310. ⟨in2p3-00000056⟩
    • G. Alexeev, E. Auffray, P. Baillon, D. Barney, G. Bassompierre, et al.. Studies of lead tungstate crystal matrices in high energy beams for the CMS electromagnetic calorimeter at the LHC. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1997, 385, pp.425-434. ⟨in2p3-00002417⟩
    • M. Acciarri, O. Adriani, M. Aguilar-Benitez, S. Ahlen, J. Alcaraz, et al.. Search for the Standard Model Higgs Boson in e^+ e^- Interactions at 161 \leq \sqrt{s} \leq 172 GeV. Physics Letters B, 1997, 411, pp.373-386. ⟨in2p3-00000057⟩
    • M. Acciarri, O. Adriani, M. Aguilar-Benitez, S. Ahlen, J. Alcaraz, et al.. Search for heavy neutral and charged leptons in e^+ e^- annihilation at \sqrt{s} = 161 GeV and \sqrt{s} = 172 GeV. Physics Letters B, 1997, 412, pp.189-200. ⟨in2p3-00000065⟩
    • M. Acciarri, O. Adriani, M. Aguilar-Benitez, S. Ahlen, J. Alcaraz, et al.. Neutral-Current Four-Fermion Production in e^+ e^- Interactions at 130 GeV \leq \sqrt{s} \leq 172 GeV. Physics Letters B, 1997, 413, pp.191-200. ⟨in2p3-00000207⟩

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