Publications (30)40.17 Total impact
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Dataset: ALICE LHC 1748-0221 3 08 S08002
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Article: Multiplicity distributions and charged-neutral fluctuations
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ABSTRACT: Results from the multiplicity distributions of inclusive photons and charged particles, scaling of particle multiplicities, event-by-event multiplicity fluctuations, and charged-neutral fluctuations in 158A GeV Pb+Pb collisions are presented and discussed. A scaling of charged particle multiplicity as N part 1.07±0.05 and photos as N part 1.12±0.03 have been observed, indicating violation of naive wounded nucleon model. The analysis of localized charged-neutral fluctuation indicates a model-independent demonstration of non-statistical fluctuations in both charged particles and photons in limited azimuthal regions. However, no correlated charged-neutral fluctuations are observed.Pramana 04/2012; 57(2):285-300. · 0.57 Impact Factor -
Article: The ALICE experiment at the CERN LHC
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ABSTRACT: ALICE (A Large Ion Collider Experiment) is a general-purpose, heavy-ion detector at the CERN LHC which focuses on QCD, the strong-interaction sector of the Standard Model. It is designed to address the physics of strongly interacting matter and the quark-gluon plasma at extreme values of energy density and temperature in nucleus-nucleus collisions. Besides running with Pb ions, the physics programme includes collisions with lighter ions, lower energy running and dedicated proton-nucleus runs. ALICE will also take data with proton beams at the top LHC energy to collect reference data for the heavy-ion programme and to address several QCD topics for which ALICE is complementary to the other LHC detectors. The ALICE detector has been built by a collaboration including currently over 1000 physicists and engineers from 105 Institutes in 30 countries. Its overall dimensions are 16 × 16 × 26 m3 with a total weight of approximately 10 000 t. The experiment consists of 18 different detector systems each with its own specific technology choice and design constraints, driven both by the physics requirements and the experimental conditions expected at LHC. The most stringent design constraint is to cope with the extreme particle multiplicity anticipated in central Pb-Pb collisions. The different subsystems were optimized to provide high-momentum resolution as well as excellent Particle Identification (PID) over a broad range in momentum, up to the highest multiplicities predicted for LHC. This will allow for comprehensive studies of hadrons, electrons, muons, and photons produced in the collision of heavy nuclei. Most detector systems are scheduled to be installed and ready for data taking by mid-2008 when the LHC is scheduled to start operation, with the exception of parts of the Photon Spectrometer (PHOS), Transition Radiation Detector (TRD) and Electro Magnetic Calorimeter (EMCal). These detectors will be completed for the high-luminosity ion run expected in 2010. This paper describes in detail the detector components as installed for the first data taking in the summer of 2008.Journal of Instrumentation 08/2008; 3(08):S08002. · 1.87 Impact Factor -
Article: The ALICE experiment at the CERN LHC
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ABSTRACT: ALICE (A Large Ion Collider Experiment) is a general-purpose, heavy-ion detector at the CERN LHC which focuses on QCD, the strong-interaction sector of the Standard Model. It is designed to address the physics of strongly interacting matter and the quark-gluon plasma at extreme values of energy density and temperature in nucleus-nucleus collisions. Besides running with Pb ions, the physics programme includes collisions with lighter ions, lower energy running and dedicated proton-nucleus runs. ALICE will also take data with proton beams at the top LHC energy to collect reference data for the heavy-ion programme and to address several QCD topics for which ALICE is complementary to the other LHC detectors. The ALICE detector has been built by a collaboration including currently over 1000 physicists and engineers from 105 Institutes in 30 countries. Its overall dimensions are 16 × 16 × 26 m3 with a total weight of approximately 10 000 t. The experiment consists of 18 different detector systems each with its own specific technology choice and design constraints, driven both by the physics requirements and the experimental conditions expected at LHC. The most stringent design constraint is to cope with the extreme particle multiplicity anticipated in central Pb-Pb collisions. The different subsystems were optimized to provide high-momentum resolution as well as excellent Particle Identification (PID) over a broad range in momentum, up to the highest multiplicities predicted for LHC. This will allow for comprehensive studies of hadrons, electrons, muons, and photons produced in the collision of heavy nuclei. Most detector systems are scheduled to be installed and ready for data taking by mid-2008 when the LHC is scheduled to start operation, with the exception of parts of the Photon Spectrometer (PHOS), Transition Radiation Detector (TRD) and Electro Magnetic Calorimeter (EMCal). These detectors will be completed for the high-luminosity ion run expected in 2010. This paper describes in detail the detector components as installed for the first data taking in the summer of 2008.Journal of Instrumentation. 07/2008; 3:8002. -
Article: Suppression of high-p{T} neutral pion production in central Pb+Pb collisions at sqrt[S{NN}]=17.3 GeV relative to p+C and p+Pb collisions.
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ABSTRACT: Neutral pion transverse momentum spectra were measured in p+C and p+Pb collisions at sqrt[S{NN}]=17.4 GeV at midrapidity (2.3 less than or approximately equal eta{lab} less than or approximately equal 3.0) over the range 0.7 less than or approximately equal p{T} less than or approximately equal 3.5 GeV/c. The spectra are compared to pi{0} spectra measured in Pb+Pb collisions at sqrt[S{NN}]=17.3 GeV in the same experiment. For a wide range of Pb+Pb centralities (N{part} less than or approximately equal 300), the yield of pi{0}'s with p{T} greater than or approximately equal 2 GeV/c is larger than or consistent with the p+C or p+Pb yields scaled with the number of nucleon-nucleon collisions (N{coll}), while for central Pb+Pb collisions with N{part}greater than or approximately equal 350, the pi{0} yield is suppressed.Physical Review Letters 06/2008; 100(24):242301. · 7.37 Impact Factor -
Article: Pion freeze-out time in Pb+Pb collisions at 158 AGeV/c studied via π-/π+ and K-/K+ ratios
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ABSTRACT: The effect of the final state Coulomb interaction on particles produced in Pb+Pb collisions at 158 AGeV/c has been investigated in the WA98 experiment through the study of the π-/π+ and K-/K+ ratios measured as a function of mT-m0. While the ratio for kaons shows no significant mT dependence, the π-/π+ ratio is enhanced at small mT-m0 values with an enhancement that increases with centrality. A silicon pad detector located near the target is used to estimate the contribution of hyperon decays to the π-/π+ ratio. The comparison of results with predictions of the RQMD model in which the Coulomb interaction has been incorporated allows to place constraints on the time of the pion freeze-out.European Physical Journal C 10/2006; 48(2):343-352. · 3.63 Impact Factor -
Article: Interferometry of direct photons in central 208Pb + 208Pb collisions at 158A GeV.
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ABSTRACT: Two-particle correlations of direct photons were measured in central 208Pb+208Pb collisions at 158A GeV. The invariant interferometric radii were extracted for 100<K(T)<300 MeV/c and compared to radii extracted from charged pion correlations. The yield of soft direct photons, K(T)<300 MeV/c, was extracted from the correlation strength and compared to theoretical calculations.Physical Review Letters 07/2004; 93(2):022301. · 7.37 Impact Factor -
Article: Centrality dependence of charged-neutral particle fluctuations in 158A GeV 208Pb+208Pb collisions
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ABSTRACT: Results on the study of localized fluctuations in the multiplicity of charged particles and photons produced in 158AGeV/c Pb+Pb collisions are presented for varying centralities. The charged versus neutral particle multiplicity correlations in common phase space regions of varying azimuthal sizes are analyzed by two different methods. Various types of mixed events are constructed to probe fluctuations arising from different sources. The measured results are compared to those from simulations and from mixed events. The comparison indicates the presence of nonstatistical fluctuations in both the charged particle and photon multiplicities in limited azimuthal regions. However, no correlated charged-neutral fluctuations, a possible signature of formation of disoriented chiral condensates, are observed. An upper limit on the production of disoriented chiral condensates is set.Phys. Rev. C. 04/2003; 67(4). -
Article: One-, two-, and three-particle distributions from 158AGeV/c central Pb+Pb collisions
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ABSTRACT: Several hadronic observables have been studied in central 158A GeV Pb+Pb collisions using data measured by the WA98 experiment at CERN: single π- and K- production, as well as two- and three-pion interferometry. The Wiedemann-Heinz hydrodynamical model has been fitted to the pion spectrum, giving an estimate of the temperature and transverse flow velocity. Bose-Einstein correlations between two identified π- have been analyzed as a function of kT, using two different parametrizations. The results indicate that the source does not have a strictly boost invariant expansion or spend time in a long-lived intermediate phase. A comparison between data and a hydrodynamical based simulation shows very good agreement for the radii parameters as a function of kT. The pion phase-space density at freeze-out has been measured, and agrees well with the Tomás̆ik-Heinz model. A large pion chemical potential close to the condensation limit of mπ seems to be excluded. The three-pion Bose-Einstein interferometry shows a substantial contribution of the genuine three-pion correlation, but not quite as large as expected for a fully chaotic and symmetric source.Phys. Rev. C. 01/2003; 67(1). -
Article: Event-by-event fluctuations in particle multiplicities and transverse energy produced in 158A GeV Pb+Pb collisions
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ABSTRACT: Event-by-event fluctuations in the multiplicities of charged particles and photons, and the total transverse energy in 158A GeV Pb+Pb collisions are studied for a wide range of centralities. For narrow centrality bins the multiplicity and transverse energy distributions are found to be near perfect Gaussians. The effect of detector acceptance on the multiplicity fluctuations has been studied and demonstrated to follow statistical considerations. The centrality dependence of the charged particle multiplicity fluctuations in the measured data has been found to agree reasonably well with those obtained from a participant model. However, for photons the multiplicity fluctuations have been found to be lower compared to those obtained from a participant model. The multiplicity and transverse energy fluctuations have also been compared to those obtained from the VENUS event generator.Phys. Rev. C. 05/2002; 65(5). -
Article: Three-pion interferometry results from central Pb+Pb collisions at 158A GeV/c.
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ABSTRACT: Three-particle correlations have been measured for identified pi(-) from central 158A GeV Pb+Pb collisions by the WA98 experiment at CERN. A substantial contribution of the genuine three-body correlation has been found as expected for a mainly chaotic and symmetric source.Physical Review Letters 11/2000; 85(14):2895-9. · 7.37 Impact Factor -
Article: Observation of direct photons in central 158a gev {sup}208{/sup}Pb+ {sup}208{/sup}Pb collisions
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ABSTRACT: No abstract prepared.Physical Review Letters 06/2000; 85. · 7.37 Impact Factor -
Article: Present status and future of DCC analysis
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ABSTRACT: Disoriented Chiral Condensates (DCC) have been predicted to form in high energy heavy ion collisions where the approximate chiral symmetry of QCD has been restored. This leads to large imbalances in the production of charged to neutral pions. Sophisticated analysis methods are being developed to disentangle DCC events out of the large background of events with conventionally produced particles. We present a short review of current analysis methods and future prospects.Nuclear Physics A 07/1998; 638:249-260. · 1.54 Impact Factor -
Article: Azimuthal anisotropy in S + Au reactions at 200 A GeV
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ABSTRACT: Azimuthal correlations of photons produced at mid-rapidity in 200 A GeV S + Au collisions have been studied using a preshower photon multiplicity detector in the WA93 experiment. The Fourier expansion method has been employd to estimate the event plane via the anisotropy of the event as a function of centrality. The event plane correlation technique has been used to determine the true event anisotropy, beyond the anisotropy which arises due to finite multiplicity. The VENUS event generator with rescattering and proper simulation of the detector response can explain only a portion of the observed anisotropy. The residual anisotropy is found to be of the order of 5% for semi-central collisions. This suggests that directed collective flow of the produced particles is present at SPS energies.Physics Letters B - PHYS LETT B. 01/1997; 403(3):390-396. -
Article: Photon and Neutral Meson Production in 158 AGeV 208Pb+Pb Collisions
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ABSTRACT: First results from the WA98 experiment on 33 TeV 208Pb ion reactions with various targets measured at the CERN SPS are presented. Data on transverse energy production and particle multiplicity are discussed. Special emphasis is laid on photon and neutral meson production.Nuclear Physics A 01/1996; 610:200-212. · 1.54 Impact Factor -
Article: Comparison of π0 and η spectra from S + Au collisions at 200 GeV/c
Nuclear Physics A 12/1993; 566:355-358. · 1.54 Impact Factor -
Article: ALICE: Physics Performance Report, volume I
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Article: Transverse momentum distributions of neutral pions from nuclear collisions at 200 AGeV
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ABSTRACT: New results on transverse mass spectra of neutral pions measured at central rapidity are presented for impact parameter selected 200 AGeV S + S and S + Au collisions. The spectra from all systems show a clear power-law like shape with similar curvature. Collisions of S + Au exhibit a larger mean transverse momentum than pp increasing with centrality. Predictions of string models and by hydrodynamic approaches including collective expansion and decays of short lived resonances are compared to the data and the implications are discussed. -
Article: Elliptic emission of K+ in 158A GeV Pb+Pb collisions
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ABSTRACT: We have studied the azimuthal angle distributions of identified charged particles near mid-rapidity region in semi-central Pb+Pb collisions at SPS energies. Our preliminary results show that π+ mesons and protons seem to be emitted in the reaction plane, while out-of-plane for K+ mesons. This phenomenon might be explained by the existence of another possible effect such as in-medium potential as well as the collective motion.Nuclear Physics A. -
Article: Collective flow in 158AGeV Pb+Pb collisions
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ABSTRACT: Anisotropic transverse flow has been studied with a magnetic spectrometer at midrapidity and the Plastic Ball detector at target rapidity in the WA98 experiment. Our preliminary results show the existence of directed and elliptic flow in semi-central Pb+Pb collisions. The magnitude of the directed flow is found to be significantly smaller than those observed at the AGS energies.Nuclear Physics A.
Top co-authors
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Institutions
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2002–2012
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Kurchatov Institute
Moscow, Moscow, Russia
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2000–2008
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Panjab University
Chandīgarh, Union Territory of Chandigarh, India
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1998
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INS HEA
Suresnes, Ile-de-France, France
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