共查询到20条相似文献,搜索用时 453 毫秒
1.
BEDANGADAS MOHANTY 《Pramana》2014,82(5):893-905
The transverse momentum spectra of the produced hadrons have been compared to a model, which is based on the assumption that a nucleus–nucleus collision is a superposition of isotropically decaying thermal sources at a given freeze-out temperature. The freeze-out temperature in nucleus–nucleus collisions is fixed from the inverse slope of the transverse momentum spectra of hadrons in nucleon–nucleon collision. The successive collisions in thessss nuclear reactions leads to gain in transverse momentum, as the nucleons propagate in the nucleus following a random walk pattern. The average transverse rapidity shift per collision is determined from the nucleon–nucleus collision data. Using this information, we obtain parameter-free result for the transverse momentum distribution of produced hadrons in nucleus–nucleus collisions. It is observed that such a model is able to explain the transverse mass spectra of the produced pions at SPS energies. However, it fails to satisfactorily explain the transverse mass spectra of kaons and protons. This indicates the presence of collective effect which cannot be accounted for, by the initial state collision broadening of transverse momentum of produced hadrons, the basis of random walk model. 相似文献
2.
Adler SS Afanasiev S Aidala C Ajitanand NN Akiba Y Alexander J Amirikas R Aphecetche L Aronson SH Averbeck R Awes TC Azmoun R Babintsev V Baldisseri A Barish KN Barnes PD Bassalleck B Bathe S Batsouli S Baublis V Bazilevsky A Belikov S Berdnikov Y Bhagavatula S Boissevain JG Borel H Borenstein S Brooks ML Brown DS Bruner N Bucher D Buesching H Bumazhnov V Bunce G Burward-Hoy JM Butsyk S Camard X Chai JS Chand P Chang WC Chernichenko S Chi CY Chiba J Chiu M Choi IJ Choi J Choudhury RK Chujo T 《Physical review letters》2004,92(5):051802
J/psi production has been measured in proton-proton collisions at square root of s=200 GeV over a wide rapidity and transverse momentum range by the PHENIX experiment at the Relativistic Heavy Ion Collider. Distributions of the rapidity and transverse momentum, along with measurements of the mean transverse momentum and total production cross section are presented and compared to available theoretical calculations. The total J/psi cross section is 4.0+/-0.6(stat)+/-0.6(syst)+/-0.4(abs) mu b. The mean transverse momentum is 1.80+/-0.23(stat)+/-0.16(syst) GeV/c. 相似文献
3.
T. Alber et al. 《The European Physical Journal C - Particles and Fields》1998,2(4):643-659
The transverse momentum and rapidity distributions of net protons and negatively charged hadrons have been measured for minimum
bias proton–nucleus and deuteron–gold interactions, as well as central oxygen–gold and sulphur–nucleus collisions at 200 GeV
per nucleon. The rapidity density of net protons at midrapidity in central nucleus–nucleus collisions increases both with
target mass for sulphur projectiles and with the projectile mass for a gold target. The
shape of the rapidity distributions of net protons forward of midrapidity for d+Au and central S+Au collisions is similar.
The average rapidity loss is larger than 2 units of rapidity for reactions with the gold target. The transverse momentum spectra
of net protons for all reactions can be described by a thermal distribution with ‘temperatures’ between MeV (p+S interactions) and MeV (central S+Au collisions). The multiplicity of negatively charged hadrons increases with the mass of the colliding system.
The shape of the transverse momentum spectra of negatively charged hadrons changes from minimum bias p+p and p+S interactions
to p+Au and central nucleus-nucleus collisions. The mean transverse momentum is almost constant in the vicinity of midrapidity
and shows little variation with the target and projectile masses. The average number of produced negatively charged hadrons
per participant baryon increases slightly from p+p, p+A to central S+S,Ag collisions.
Received: 28 October 1997 / Published online: 10 March 1998 相似文献
4.
Transverse momentum and transverse mass distributions of charged hadrons produced in Au--Au collisions at high energies 下载免费PDF全文
The transverse momentum distribution and the transverse mass distribution of charged hadrons produced in nucleus nucleus collisions at high energies are described by using a two-cylinder model. The results calculated by the model are compared and found to be in agreement with the experimental data of the STAR and E895 Collaborations, measured in A~Au collisions at the relativistic heavy ion collider (RHIC) and alternating-gradient synchrotron (AGS) energies, respectively. In the energy range concerned, the excitation degree of emission source close to the central axis of cylinders increases obviously with the collision centrality and incident energy increasing, but it does not show any obvious change with the increase of the (pseudo)rapidity in central collisions. The excitation degree of emission source close to the side-surface of cylinders does not show any obvious change with the collision centrality, the (pseudo)rapidity, and the incident energy increasing. 相似文献
5.
The transverse mass spectra of protons, pions, kaons, Lambda and Antilambda produced in cen- tral nucleus-nucleus collisions at high energies are described by using one-temperature and two-temperature emission pictures. The calculated results are compared and found to be in good agreement with the experimen- tal data of the E895, E866 and E917 Collaborations measured in central Au-Au collisions at the Alternating Gradient Synchrotron (AGS) energies and the NA49 Collaboration measured in central Pb-Pb collisions at the Super Proton Synchrotron (SPS) energies. It is demonstrated that the transverse mass distributions of protons, kaons, Lambda and Antilambda, except for Lambda hyperons produced in central Pb-Pb collisions at 158 A GeV, can be described by using the one-temperature emission picture, and for pions, we need to use the two-temperature emission picture. 相似文献
6.
This review examines data on strange particle production in Pb + Pb collisions obtained in heavy ion experiments at CERN SPS.
The yields of K, Λ, Ξ and Ω are considered, as well as their rapidity and transverse mass distributions, depending on the
centrality of Pb + Pb collisions at SPS energies. Experimental results are compared with predictions of the statistical nuclear
fireball and microscopic parton -string models. We discuss in detail the experimentally observed effect of strangeness enhancement
in nucleus-nucleus collisions as compared to nucleon-nuclear interactions and its interpretation within the framework of various
theoretical models. Also, we analyze the behavior of hyperon yields and nuclear modification factors in passing from SPS to
RHIC energies. 相似文献
7.
Anisotropic transverse flow is studied in Pb+Pb and Au+Au collisions at SPS and RHIC energies. The centrality and transverse momentum dependence at midrapidity of the elliptic flow coefficient v2 is calculated in the hydrodynamic and low density limits. Hydrodynamics is found to agree well with the RHIC data for semicentral collisions up to transverse momenta of 1–1.5 GeV/c, but it considerably overestimates the measured elliptic flow at SPS energies. The low density limit LDL is inconsistent with the measured magnitude of v2 at RHIC energies and with the shape of its pt-dependence at both RHIC and SPS energies. The success of the hydrodynamic model points to very rapid thermalization in Au+Au collisions at RHIC and provides a serious challenge for kinetic approaches based on classical scattering of on-shell particles. 相似文献
8.
Georg Wolschin 《Pramana》2003,60(5):1035-1038
Different from the early universe, heavy-ion collisions at very high energies do not reach statistical equilibrium, although
thermal models explain many of their features. To account for nonequilibrium strong-coupling effects, a Fokker-Planck equation
with time-dependent diffusion coefficient is proposed. A schematic model for rapidity distributions of participant baryons
is set up and solved analytically. The evolution from SIS via AGS and SPS to RHIC energies is discussed. Strong-coupling diffusion
produces double-peaked spectra in central collisions at the higher SPS momentum of 158 A.GeV/c and beyond. 相似文献
9.
I. Belikov 《Physics of Atomic Nuclei》2012,75(5):580-584
The results from first series of measurements performed by the ALICE experiment at the LHC are presented. These measurements include the charged-particle pseudorapidity densities, multiplicity distributions and transverse momentum spectra obtained by analyzing the data collected in 2009 and 2010 in proton-proton collisions at three different center-of-mass energies of 0.9, 2.36, and 7 TeV. The results are compared to previous proton-antiproton data and to model predictions. 相似文献
10.
《Physics letters. [Part B]》1987,199(1):30-33
The momentum of all charged mesons produced in 19 high energy, high multiplicity nucleus-nucleus collisions of cosmic rays in emulsion have been measured. The transverse momentum distribution differs qualitatively from proton-proton collisions at comparable energies. One possible interpretation is in terms of a transverse explosion with effective temperature T=78 MeV and transverse flow velocity υ=0.61c. 相似文献
11.
J. Barrette R. Bellwied P. Braun-Munzinger W. E. Cleland T. M. Cormier G. David J. Dee G. E. Diebold O. Dietzsch J. V. Germani S. Gilbert S. V. Greene J. R. Hall T. K. Hemmick N. Herrmann B. Hong K. Jayananda D. Kraus B. Shiva Kumar R. Lacasse D. Lissauer W. J. Llope T. W. Ludlam S. McCorkle R. Majka S. K. Mark J. T. Mitchell M. Muthuswamy E. O'Brien C. Pruneau M. N. Rao F. Rotondo J. Sandweiss N. C. daSilva U. Sonnadara J. Stachel H. Takai E. M. Takagui T. G. Throwe C. Winter G. Wang D. Wolfe C. L. Woody N. Xu Y. Zhang Z. Zhang C. Zou 《Zeitschrift fur Physik C Particles and Fields》1993,59(2):211-214
We have measured distributions in transverse momentum and rapidity of protons from interactions of 14.6 GeV/nucleon28Si projectiles with targets of Al and Pb. The transverse momentum spectra exhibit a thermal shape with a rapidity dependent temperature parameter. For very central or violent collisions the proton rapidity distributions exhibit the large rapidity shifts and (for Si+Al) a peak at midrapidity as required for full stopping. 相似文献
12.
Rene Bellwied 《Acta Physica Hungarica A》2002,15(3-4):437-444
We investigate the transverse polarization of A hyperons produced in 11.6 A GeV/c Au?Au collisions at the AGS. Experiment E896 yields results in two independent detector systems, a Silicon Drift Detector Array at midrapidity and a Distributed Drift Chamber at forward rapidity. In this article we focus on the mid-rapidity measurements. The results reveal a dependence of the polarization on the transverse momentum and Feynman-x of the A hyperons. The heavy-ion data are consistent with previous measurements in proton-proton and proton-nucleus collisions within statistical errors. 相似文献
13.
Adare A Afanasiev S Aidala C Ajitanand NN Akiba Y Al-Bataineh H Alexander J Al-Jamel A Aoki K Aphecetche L Armendariz R Aronson SH Asai J Atomssa ET Averbeck R Awes TC Azmoun B Babintsev V Baksay G Baksay L Baldisseri A Barish KN Barnes PD Bassalleck B Bathe S Batsouli S Baublis V Bauer F Bazilevsky A Belikov S Bennett R Berdnikov Y Bickley AA Bjorndal MT Boissevain JG Borel H Boyle K Brooks ML Brown DS Bucher D Buesching H Bumazhnov V Bunce G Burward-Hoy JM Butsyk S Campbell S Chai JS Chang BS 《Physical review letters》2007,98(23):232301
The PHENIX experiment at the BNL Relativistic Heavy Ion Collider (RHIC) has measured J/psi production for rapidities -2.2相似文献
14.
The rapidity densities at mid-rapidity and the transverse momentum distributions for strange hadrons produced in pp collisions are analyzed using the modified PACIAE model by considering the effect of inelastic (re)scattering processes s→gg and gg→s in parton (re)scattering. The calculated results of the transverse momentum spectra of the strangeness fitting with data measured by STAR and ALICE Collaborations can be improved, especially at large transverse momentum levels. This demonstrates that the effect of inelastic (re)scattering processes of s→gg and gg→s is not negligible at RHIC and LHC energy levels. 相似文献
15.
16.
New results on transverse mass spectra of neutral pions measured at central rapidity are presented for impact parameter selected
200 GeV S + S and S + Au collisions. The distributions cover more than 8 orders of magnitude in cross section over the range . Detailed comparisons to results from pp collisions are made. 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.
Received: 10 March 1998 / Revised version: 22 May 1998 / Published online: 12 August 1998 相似文献
17.
Edward K. Sarkisyan-Grinbaum 《Physics of Particles and Nuclei Letters》2011,8(9):875-880
We present measurements of charged particle production in proton-proton collisions at centre-of-mass energies of √s = 0.9, 2.36 and 7 TeV recorded with the ATLAS detector at the Large Hadron Collider. Events were collected using a single-arm
minimum bias trigger, charged tracks are measured with high precision in the inner tracking system. Minimum bias analysis
uses data samples at all three energies, while diffractive events are studied using a sample of events at √s = 7 TeV. To study diffractive interactions, the events that have hits on exactly one side of the ATLAS detector were selected.
The charged particle multiplicity, pseudorapidity and transverse momentum spectra are analyzed and compared to the predictions
by various Monte Carlo models. 相似文献
18.
I.G. Bearden H. Bøggild J. Boissevain P.H.L. Christiansen L. Conin J. Dodd B. Erazmus S. Esumi C.W. Fabjan D. Ferenc A. Franz J.J. Gaardhøje A.G. Hansen O. Hansen D. Hardtke H. van Hecke E.B. Holzer T.J. Humanic P. Hummel B.V. Jacak K. Kaimi M. Kaneta T. Kohama M. Kopytine M. Leltchouk A. Ljubičić Jr. B. Lörstad L. Martin A. Medvedev M. Murray H. Ohnishi G. Paić S.U. Pandey F. Piuz J. Pluta V. Polychronakos M. Potekhin G. Poulard D. Reichhold A. Sakaguchi J. Schmidt-Sørensen J. Simon-Gillo W. Sondheim T. Sugitate J.P. Sullivan Y. Sumi W.J. Willis K. Wolf N. Xu D.S. Zachary 《The European Physical Journal C - Particles and Fields》2002,23(2):237-247
Proton and deuteron production has been observed in S+S and S+Pb collisions at 200 AGeV and in Pb+Pb reactions at 158 AGeV at the CERN SPS accelerator. For Pb+Pb triton production was also measured. The p and d spectra as well as the p and t
spectra were observed in similar rapidity ranges and over similar ranges of transverse momenta per nucleon, making it possible
to interpret the cross sections of the composite particles in terms of coalescence mechanisms. Volumes of homogeneity were
extracted and compared to pion-pair HBT interferometry results. Special attention is given to the dependence on transverse
mass, centrality and rapidity.
Received: 23 July 2001 / Revised version: 16 November 2001 / Published online: 25 January 2002 相似文献
19.
The rapidity and transverse momentum dependence of the nuclear modification ratio for dilepton production at RHIC and LHC is presented, calculated in the color glass condensate (CGC) framework. The transverse momentum ratio is compared for two distinct dilepton mass values and a suppression of the Cronin peak is verified even for large mass. The nuclear modification ratio suppression in the dilepton rapidity spectra, as obtained experimentally for hadrons at RHIC, is verified for LHC energies at large transverse momentum, although not present at RHIC energies. The ratio between LHC and RHIC nuclear modification ratios is evaluated in the CGC, showing the large saturation effects at LHC compared with the RHIC results. These results consolidate the dilepton as a most suitable observable to investigate the QCD high density approaches. 相似文献
20.
The φ meson productions in Au+Au and/or Pb+Pb collisions at AGS, SPS,
RHIC, and LHC energies have been studied systematically with a hadron and
string cascade model LUCIAE. After considering the energy dependence of the
model parameter α in string fragmentation function and adjusting it
to the experimental data of charged multiplicity to a certain extent,
the model predictions for φ meson yield, rapidity, and
transverse mass distributions are compatible with the experimental data at
AGS, SPS and RHIC energies. A calculation for Pb+Pb collisions at LHC energy
is given as well. The obtained fractional variable in string fragmentation
function shows a saturation in energy dependence. It is discussed that the
saturation of fractional variable in string fragmentation function might be a
qualitative representation of the energy dependence of nuclear transparency. 相似文献