Azimuthal anisotropy of charged jet production in root s(NN)=2.76 TeV Pb-Pb collisions

We present measurements of the azimuthal dependence of charged jet production in central and semi-central root s(NN) = 2.76 TeV Pb-Pb collisions with respect to the second harmonic event plane, quantified as nu(ch)(2) (jet). Jet finding is performed employing the anti-k(T) algorithm with a resolution parameter R = 0.2 using charged tracks from the ALICE tracking system. The contribution of the azimuthal anisotropy of the underlying event is taken into account event-by-event. The remaining (statistical) region-to-region fluctuations are removed on an ensemble basis by unfolding the jet spectra for different event plane orientations independently. Significant non-zero nu(ch)(2) (jet) is observed in semi-central collisions (30-50% centrality) for 20 <p(T)(ch) (jet) <90 GeV/c. The azimuthal dependence of the charged jet production is similar to the dependence observed for jets comprising both charged and neutral fragments, and compatible with measurements of the nu(2) of single charged particles at high p(T). Good agreement between the data and predictions from JEWEL, an event generator simulating parton shower evolution in the presence of a dense QCD medium, is found in semi-central collisions. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).Peer reviewe

Forward-central two-particle correlations in p-Pb collisions at root s(NN)=5.02 TeV

Two-particle angular correlations between trigger particles in the forward pseudorapidity range (2.5 2GeV/c. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B. V.Peer reviewe

Event-shape engineering for inclusive spectra and elliptic flow in Pb-Pb collisions at root(NN)-N-S=2.76 TeV

Peer reviewe

Elliptic flow of muons from heavy-flavour hadron decays at forward rapidity in Pb-Pb collisions at root s(NN)=2.76TeV

The elliptic flow, v(2), of muons from heavy-flavour hadron decays at forward rapidity (2.5 <y <4) is measured in Pb-Pb collisions at root s(NN)= 2.76TeVwith the ALICE detector at the LHC. The scalar product, two- and four-particle Q cumulants and Lee-Yang zeros methods are used. The dependence of the v(2) of muons from heavy-flavour hadron decays on the collision centrality, in the range 0-40%, and on transverse momentum, p(T), is studied in the interval 3 <p(T)<10 GeV/c. A positive v(2) is observed with the scalar product and two-particle Q cumulants in semi-central collisions (10-20% and 20-40% centrality classes) for the p(T) interval from 3 to about 5GeV/c with a significance larger than 3 sigma, based on the combination of statistical and systematic uncertainties. The v(2) magnitude tends to decrease towards more central collisions and with increasing pT. It becomes compatible with zero in the interval 6 <p(T)<10 GeV/c. The results are compared to models describing the interaction of heavy quarks and open heavy-flavour hadrons with the high-density medium formed in high-energy heavy-ion collisions. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B.V.Peer reviewe

Centrality evolution of the charged-particle pseudorapidity density over a broad pseudorapidity range in Pb-Pb collisions at root s(NN)=2.76TeV

Peer reviewe

Pseudorapidity and transverse-momentum distributions of charged particles in proton-proton collisions at root s=13 TeV

The pseudorapidity (eta) and transverse-momentum (p(T)) distributions of charged particles produced in proton-proton collisions are measured at the centre-of-mass energy root s = 13 TeV. The pseudorapidity distribution in vertical bar eta vertical bar <1.8 is reported for inelastic events and for events with at least one charged particle in vertical bar eta vertical bar <1. The pseudorapidity density of charged particles produced in the pseudorapidity region vertical bar eta vertical bar <0.5 is 5.31 +/- 0.18 and 6.46 +/- 0.19 for the two event classes, respectively. The transverse-momentum distribution of charged particles is measured in the range 0.15 <p(T) <20 GeV/c and vertical bar eta vertical bar <0.8 for events with at least one charged particle in vertical bar eta vertical bar <1. The evolution of the transverse momentum spectra of charged particles is also investigated as a function of event multiplicity. The results are compared with calculations from PYTHIA and EPOS Monte Carlo generators. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).Peer reviewe

Etude de la production de photons isolés dans les collisions p-Pb à √ sNN = 5.02 TeV dans l'expérience ALICE au LHC

La chromodynamique quantique est la théorie associée à l’ interaction forte dans le modèle standard. Elle prédit le confinement des partons (quarks et gluons) à l’ intérieur des hadrons dans des conditions thermodynamiques standards. Lorsque des hautes densités d’énergie sont mises en jeu, un état de déconfinement de la matière hadronique, le plasma de Quarks et Gluons (PQG), est prédit par la théorie. Cet état aurait existé aux premiers instants de l’ Univers. L ’ expérience ALICE (A Large Ion Collider Experiment) au CERN-LHC est dédiée à l’ étude de la matière hadronique dans les collisions pp, p-Pb et dans les collisions Pb-Pb où la formation d’un PQG est attendue. Dans cette thèse, nous présentons l’étude des photons issus des interactions dures entre partons. Leur section efficace de production est calculable dans le cadre de la chromodynamique quantique perturbative. Une telle mesure effectuée dans les collisions p-Pb, permet d’ étudier les effets nucléaires froids. Expérimentalement, les photons prompts sont mesurés en utilisant la méthode de l’isolement. La mesure de la section efficace des photons isolés dans les collisions p-Pb à √ sNN = 5.02 TeV avec le calorimètre EMCal de l’ expérience ALICE est présentée. Les résultats sont consistants avec les calculs théoriques effectués. La comparaison avec la section efficace mesurée dans les collisions pp a été réalisée via la détermination du facteur de modification nucléaire, RpΑ. Ce dernier est compatible avec l’unité et n’indique aucune modification claire, due à des effets nucléaires, de la production de photons prompts dans les collisions p-Pb.Quantum ChromoDynamics is the theory associated to the strong interaction in the standard model. It predicts that partons (quarks and gluons) are confined into hadrons at standard thermodynamic conditions. A state of deconfined hadronic matter, the Quark-Gluon Plasma (QGP), is predicted for a high energy density and would have existed in the early state of the Universe. ALICE (A Large Ion Collider Experiment) at CERN-LHC (Large Hadron Collider) is dedicated to hadronic matter study in p-p, p-Pb (Pb-p) and in Pb-Pb collisions where QGP formation is expected. In this thesis, we will present the study of photons coming directly from parton-parton hard scatterings, the prompt photons. Their production cross-section is calculable in perturbative Quantum ChromoDynamics theory. Such a measurement in p-Pb collisions enables the study of cold nuclear matter effects whose knowledge is crucial to distinguish key signatures of the QGP from nuclear effects in Pb-Pb collisions. Experimentally, the prompt photon can be discriminated using the isolation analysis method. In this thesis, the measurement of the isolated photon cross-section in p- Pb collisions at √ sNN= 5.02 TeV with the EMCal calorimeter of the ALICE experiment, is presented. The results are consistent, within the uncertainties, with theoretical calculations. The comparison with the measured cross-section in p-p analysis is performed via the determination of the nuclear modification factor RpΑ. The last one is compatible with the unity and does not clearly indicate modification of the prompt photon production due to nuclear effects in p-Pb collisions

Etude de la production de photons isolés dans les collisions p-Pb à $ √(s_NN ) = 5.02TeV dans l'expérience ALICE au LHC

Quantum Chromo Dynamics is the theory associated to the strong interaction in the standard model. It predicts that partons (quarks and gluons) are confined into hadrons at standard thermodynamic conditions. A state of deconfined hadronic matter, the Quark-Gluon Plasma (QGP), is predicted for a high energy density and would have existed in the early state of the Universe. ALICE (A Large Ion Collider Experiment) at CERN-LHC (Large Hadron Collider) is dedicated to hadronic matter study in p-p, p-Pb (Pb-p) and in Pb-Pb collisions where QGP formation is expected.In this thesis, we will present the study of photons coming directly from parton-parton hard scatterings, the prompt photons. Their production cross-section is calculable in perturbative Quantum Chromo Dynamics theory. Such a measurement in p-Pb collisions enables the study of cold nuclear matter effects whose knowledge is crucial to distinguish key signatures of the QGP from nuclear effects in Pb-Pb collisions. Experimentally, the prompt photon can be discriminated using the isolation analysis method. In this thesis, the measurement of the isolated photon cross-section in p-Pb collisions at √(s_NN )= 5.02 TeV with the EMCal calorimeter of the ALICE experiment, is presented. The results are consistent, within the uncertainties, with theoretical calculations. The comparison with the measured cross-section in p-p analysis is performed via the determination of the nuclear modification factor.The last one is compatible with the unity and does not clearly indicate modification of the prompt photonproduction due to nuclear effects in p-Pb collisions.La chromodynamique quantique est la théorie associée à l’interaction forte dans le modèle standard. Elle prédit le confinement des partons (quarks et gluons) à l’intérieur des hadrons dans des conditions thermodynamiques standards. Lorsque des hautes densités d’énergie sont mises en jeu, un état de déconfinement de la matière hadronique, le plasma de Quarks et Gluons (PQG), est prédit par la théorie. Cet état aurait existé aux premiers instants de l’Univers. L ’expérience ALICE (A Large Ion Collider Experiment) au CERN-LHC est dédiée à l’étude de la matière hadronique dans les collisions pp, p-Pb et dans les collisions Pb-Pb où la formation d’un PQG est attendue.Dans cette thèse, nous présentons l’étude des photons issus des interactions dures entre partons. Leur section efficace de production est calculable dans le cadre de la chromodynamique quantique perturbative. Une telle mesure effectuée dans les collisions p-Pb, permet d’étudier les effets nucléaires froids. Expérimentalement, les photons prompts sont mesurés en utilisant la méthode de l’isolement. La mesure de la section efficace des photons isolés dans les collisions p-Pb à √(s_NN )= 5.02 TeV avec le calorimètre EMCal de l’expérience ALICE est présentée. Les résultats sont consistants avec les calculs théoriques effectués. La comparaison avec la section efficace mesurée dans les collisions pp a été réalisée via la détermination du facteur de modification nucléaire. Ce dernier est compatible avec l’unité et n’indique aucune modification claire, due à des effets nucléaires, de la production de photons prompts dans les collisions p-Pb

燒津鰹漁業に於ける船仲組織(上) - 本邦漁業に特異なる勞働組織の一例 -

We report on the measurement of freeze-out radii for pairs of identical-charge pions measured in Pb-Pb collisions at √sNN = 2.76 TeV as a function of collision centrality and the average transverse momentum of the pair kT. Three-dimensional sizes of the system (femtoscopic radii), as well as direction-averaged onedimensional radii are extracted. The radii decrease with kT, following a power-law behavior. This is qualitatively consistent with expectations from a collectively expanding system, produced in hydrodynamic calculations. The radii also scale linearly with _dNch/dη_1/3. This behavior is compared to world data on femtoscopic radii in heavy-ion collisions. While the dependence is qualitatively similar to results at smaller √sNN, a decrease in the ratio Rout/Rside is seen, which is in qualitative agreement with a specific prediction from hydrodynamic models: a change from inside-out to outside-in freeze-out configuration. The results provide further evidence for the production of a collective, strongly coupled system in heavy-ion collisions at the CERN Large Hadron Collider

生産增加と貨幣需要

We report on two-particle charge-dependent cor- relations in pp, p\u2013Pb, and Pb\u2013Pb collisions as a function of the pseudorapidity and azimuthal angle difference, \u3b7 and \u3c6 respectively. These correlations are studied using the balance function that probes the charge creation time and the develop- ment of collectivity in the produced system. The dependence of the balance function on the event multiplicity as well as on the trigger and associated particle transverse momentum ( pT ) in pp, p\u2013Pb, and Pb\u2013Pb collisions at 1asNN = 7, 5.02, and 2.76 TeV, respectively, are presented. In the low transverse momentum region, for 0.2 < pT < 2.0 GeV/c, the balance function becomes narrower in both \u3b7 and \u3c6 directions in all three systems for events with higher multiplicity. The experimental findings favor models that either incorporate some collective behavior (e.g. AMPT) or different mecha- nisms that lead to effects that resemble collective behavior (e.g. PYTHIA8 with color reconnection). For higher values of transverse momenta the balance function becomes even narrower but exhibits no multiplicity dependence, indicating that the observed narrowing with increasing multiplicity at low pT is a feature of bulk particle production