Publications (23)36.77 Total impact
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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: 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: 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: Particle density fluctuations
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ABSTRACT: Event-by-event fluctuations in the multiplicities of charged particles and photons at SPS energies are discussed. Fluctuations are studied by controlling the centrality of the reaction and rapidity acceptance of the detectors. Results are also presented on the event-by-event study of correlations between the multiplicity of charged particles and photons to search for DCC-like signals.Nuclear Physics A. 715:339. -
Article: Localized charged-neutral fluctuations in 158A GeV Pb+Pb collisions
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ABSTRACT: Localized fluctuations in the multiplicity of charged particles and photons produced in central 158A GeV/c Pb+Pb collisions are studied. The charged versus neutral correlations in common η-φ phase space regions of varying azimuthal size are analyzed by two different methods. The analysis provides a model-independent demonstration of nonstatistical fluctuations in both charged particle and photon multiplicities in limited azimuthal regions. However, no correlated charge-neutral fluctuations are observed, contrary to expectations for the production of a disoriented chiral condensate. The result is not explained by the widely used VENUS model.Phys. Rev. C. 64(1). -
Article: Centrality and transverse momentum dependence of collective flow in 158 A GeV Pb+Pb collisions measured via inclusive photons
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ABSTRACT: Directed and elliptic flow of inclusive photons near mid-rapidity in 158 A GeV Pb + Pb collisions has been studied. The data have been obtained with the photon spectrometer LEDA of the WA98 experiment at the CERN SPS. The flow strength has been measured for various centralities as a function of pT and rapidity over 0.18<pT<1.5 GeV/c and 2.3<y<2.9. The angular anisotropy has been studied relative to an event plane obtained in the target fragmentation region that shows the elliptic flow to be in-plane. The elliptic flow has also been studied using two-particle correlations and shown to give similar results. A small directed flow component is observed. Both the directed and elliptic flow strengths increase with pT. The photon flow results are used to estimate the corresponding neutral pion flow.Nuclear Physics A. -
Article: Search for disoriented chiral condensates in 158 AGeV Pb+Pb collisions
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ABSTRACT: The restoration of chiral symmetry and its subsequent breaking through a phase transition has been predicted to create regions of Disoriented Chiral Condensates (DCC). This phenomenon has been predicted to cause anomalous fluctuations in the relative production of charged and neutral pions in high-energy hadronic and nuclear collisions. The WA98 experiment has been used to measure charged and photon multiplicities in the central region of 158 AGeV Pb+Pb collisions at the CERN SPS. In a sample of 212646 events, no clear DCC signal can be distinguished. Using a simple DCC model, we have set a 90% C.L. upper limit on the maximum DCC production allowed by the data.Physics Letters B. -
Article: Δ++ production in 158 A GeV 208Pb+208Pb interactions at the CERN SPS
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ABSTRACT: The Δ++-resonance production in central 158 A GeV 208Pb+208Pb collisions at the CERN SPS has been studied. The Δ++ production was estimated from the invariant mass spectrum of pπ+-pairs by subtracting a mixed event background. The measured Δ++ abundance is compared with the results from other experiments at lower energies, and with a model calculation assuming thermal and chemical equilibrium.Physics Letters B. -
Article: Photon and neutral meson production in 158 AGeV208Pb+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. -
Article: Present status and future of DCC analysis
[show abstract] [hide abstract]
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. -
Article: Elliptic emission of K+ and π+ in 158 A·GeV Pb + Pb collisions
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ABSTRACT: An event-by-event analysis of the azimuthal angular correlation with respect to the reaction plane has been carried out for K+ and π+ emission near mid-rapidity in 158 A·GeV Pb + Pb collisions. In semi-central collisions, K+ mesons are found to be preferentially emitted out of the reaction plane, while π+ mesons are emitted in the reaction plane. The results suggest that the kaon emission is influenced by in-medium potential effects in addition to collective flow effects.Physics Letters B. -
Article: Recent results on Pb+Pb collisions at 158 AGeV from the WA98 experiment at CERN
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ABSTRACT: We present recent results obtained with the WA98 experiment at CERN SPS. The experiment consists of large acceptance hadron and photon spectrometers which allow to study many aspects of heavy ion collisions. We use event-by-event measurements of charged and neutral particle multiplicity to establish the limit on the prodution of Disoriented Chiral Condensates. We use the Plastic Ball detector together with a set of tracking chambers to study collective flow. The tracking chambers together with the excellent particle identification allow us to study the production of Δ++. The high resolution photon calorimeter array allows us to study inclusive photon and π0 spectra and search for excess direct photons.Nuclear Physics A.
Top co-authors
Top Journals
- Physical Review Letters (4)
- Nuclear Physics A (2)
- Pramana (1)
- European Physical Journal C (1)
Institutions
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2000–2008
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Panjab University
Chandīgarh, Union Territory of Chandigarh, India
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2002–2006
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Joint Institute for Nuclear Research
Dubna, Moskovskaya, Russia
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1998
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INS HEA
Suresnes, Ile-de-France, France
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