共查询到20条相似文献,搜索用时 15 毫秒
1.
Perturbative unitarization from non-linear effects is thought to deplete the gluon density for transverse momenta below the saturation scale. Such effects also modify the distribution of gluons produced in heavy-ion collisions in transverse impact parameter space. I discuss some of the consequences for the initial conditions for hydrodynamic models of heavy-ion collisions and for hard “tomographic” probes. Also, I stress the importance of realistic modelling of the fluctuations of the valence sources for the small-x fields in the impact parameter plane. Such models can now be combined with solutions of running–coupling Balitsky–Kovchegov evolution to obtain controlled predictions for initial conditions at the LHC. 相似文献
2.
We analyze elliptic flow from SIS to RHIC energies systematically in a realistic dynamical cascade model. We compare our results
with the recent data from STAR and PHOBOS collaborations on elliptic flow of charged particles at midrapidity in Au+ Au collisions
at RHIC. In the analysis of elliptic flow at RHIC energy, we find a good fitting with data at 1.5 times a scaling factor to
our model, which characterizes that the model is required to have extra pressure generated from the subsequent parton scattering
after the initial minijet production. In energy dependence of elliptic flow, we notice re-hardening nature at RHIC energies.
Both these two observations would probably imply the possible formation of quark-gluon plasma. 相似文献
3.
4.
The current status of our understanding of dilepton production in ultra-relativistic heavyion collisions is discussed with
special emphasis on signals from the (approach towards) chirally restored and deconfined phases. In particular, recent results
of the CERN-SPS low-energy runs are compared to model predictions and interpreted. Prospects for RHIC experiments are given. 相似文献
5.
Xin-Nian Wang 《Physics Reports》1997,280(5-6):287-371
A pQCD-based model for parton production and equilibration in ultrarelativistic heavy-ion collisions is reviewed. The model combines pQCD processes including initial and final state radiations together with string phenomenology for nonperturbative soft processes. Nuclear effects on the initial parton production, such as multiple parton scattering and nuclear shadowing of parton distribution functions are considered. Comparisons with existing data are made and further tests of the model to constrain model parameters are proposed. With the obtained space-time history of the parton production, evolution of the minijet gas toward a fully equilibrated parton plasma is studied. Direct probes of the early parton dynamics, such as pre-equilibrium photon and dilepton production, open charm production, J/ψ suppression and jet quenching are also reviewed. 相似文献
6.
7.
We review theory of the leading-twist nuclear shadowing, and describe phenomenon of post-selection suppression of leading parton spectrum (effective fractional energy losses) in the proximity of the black disk regime. We argue that 2→2 mechanism dominates in the inclusive leading pion production in d-Au collisions and explain that the post-selection naturally explains both the magnitude of the suppression of the forward pion production in d-Au collisions and the pattern of the forward–central correlations. At the same time this pattern of correlations rules out 2→1 mechanism as the main source of the inclusive leading pion yield. It is demonstrated that the mechanism of the double-parton interactions gives an important contribution to the production of two leading pions in pp scattering opening a new way to study correlations of leading quarks in the nucleon. The same mechanism is enhanced in dAu→π0π0+X collisions and explains the dominance of Δφ independent component and suppression of the away side peak. 相似文献
8.
《Pramana》2003,60(5):1067-1072
The CERES/NA45 experiment at the CERN SPS has previously measurede
+
e
- pair production in 160 A.GeV Pb-Au collisions. In the mass regionm > 02 GeV/c2, an enhancement of 2.7±04(stat.)±0.5(syst.) compared to the expectation from known hadronic decay sources was observed. In
the 40 A.GeV data taken in 1999, an enhancement is again found; a preliminary analysis gives an even larger value of 50 ±13(stat.).
The results are compared to theoretical model calculations based on π+π- annihilation with a modified ρ-propagator; they may be related to chiral symmetry restoration. 相似文献
9.
We analyze the spectra of pions and protons in heavy-ion collisions at relativistic energies from 2 A GeV to 65+65 A GeV by
using a jet-implemented hadron-string cascade model. In this energy region, hadron transverse mass spectra first show softening
until SPS energies, and re-hardening may emerge at RHIC energies. Since hadronic matter is expected to show only softening
at higher energy densities, this re-hardening of spectra can be interpreted as a good signature of the quark-gluon plasma
formation 相似文献
10.
Jean-Yves Ollitrault 《Pramana》2006,67(5):899-914
I review recent results from the heavy-ion programme at the Brookhaven Relativistic Heavy Ion Collider and their interpretation. 相似文献
11.
We investigate the lepton pair production with the Drell-Yan process in relativistic heavy ion collisions by computing the double differential cross section dσ/dM2dy and dσ/dM2dxF at the next-to-leading order in p+Au and Au+Au collisions with √sNN =200 GeV at RHIC. The resulting nuclear modification factors RpAu and RAuAu show strong sensitivity to the cold nuclear matter (CNM) effects and could probe the CNM effects at a very wide region of the longitudinal momentum fraction x. The variation of R with the invariant mass M, the rapidity y and the Feynman variable xF is shown and we find that the nuclear modification factor for the double differential cross section could be smaller than 0.4 in some kinematic regions of high-energy nucleus-nucleus reactions at RHIC. 相似文献
12.
《Nuclear Physics A》1997,624(4):738-754
Hadrons emitted by the pre-surface layer of a quark-gluon plasma (QGP) before the phase transition into a hadronic gas are considered as possible sources of direct information about QGP. It is shown that if QGP is created in ultrarelativistic heavy-ion collisions, then these hadrons strongly contribute at soft pt at SpS energy and dominate up to an order of magnitude at LHC energy. 相似文献
13.
Mariusz Michalec Wojciech Florkowski Wojciech Broniowski 《Physics letters. [Part B]》2001,520(3-4):213-216
By means of a simple rescaling, modifications of hadron masses and widths are incorporated into the thermal analysis of particle ratios in ultrarelativistic heavy-ion collisions. We find that moderate, up to 20%, changes of hadron masses do not spoil the quality of the fits, which remain as good as those obtained without modifications. Larger changes are not likely. The fits with the modified masses yield modified values of the optimal temperature and baryon chemical potential. In particular, with decreasing masses of all hadrons (except for pseudo-Goldstone bosons) the fitted values of the temperature and the baryon chemical potential are lowered, with the change approximately proportional to the scaling of masses. In addition, we find that the broadening of the hadron widths by less than a factor of two practically does not affect the fits. 相似文献
14.
T. F. Hoang 《Zeitschrift fur Physik C Particles and Fields》1994,61(2):341-345
The characteristic features of pseudorapidity distributions of hadron production are investigated in terms of a geometrical parameterh≡(dn/dη)0/Φ, Φ being the phase space covered by the η distribution. It is found thath is about the same for the heavy-ion (HI) andpp collisions at the same energy, the same for π andK production and behaves ash~E cm ?1/3 . This similarity property yieldsK ?/π?=0.041±0.004 andK +/K ?=4.5±0.6 for HI collisions at 14.6 GeV/A in agreement with BNL experiments. 相似文献
15.
It is proposed that soft particle production in hadronic collisions is dominated by multiple gluon exchanges between partons from the colliding hadrons, followed by radiation of hadronic clusters from the coloured partons distributed uniformly in rapidity. This explains naturally two dominant features of the data: (a) the linear increase of rapidity spectra in the regions of limiting fragmentation and, (b) the proportionality between the increasing width of the limiting fragmentation region and the height of the central plateau. 相似文献
16.
A. B. Kaidalov 《Physics of Atomic Nuclei》2010,73(4):689-702
Nuclear shadowing effects for quarks and gluons are calculated using information on diffractive deep inelastic scattering
on a nucleon. Role of these effects in interactions of hadrons and nuclei with nuclei at high energies is investigated. A
decrease in particle densities for heavy-ion collisions in comparison with the Glauber model is predicted and nuclear modification
factors are calculated. Distributions of gluons in nuclei are used to predict suppression of heavy quarkonia. The parameter-free
calculation of J/ψ in DAu and AuAu collisions is in a good agreement with recent RHIC data. Predictions for heavy quarkonia suppression in heavy-ion
collisions at LHC are formulated. 相似文献
17.
Strong electromagnetic fields produced in the non-central heavy-ion collisions can induce vector meson photoproduction. In this paper, we study the photoproduction J/ψ and φ mesons in the relativistic heavy-ion collision from ultra-peripheral nuclear collisions to peripheral hadronic heavy ion collisions. And then include both initial hadronic production and thermal production in quark-gluon plasma (QGP). We find, for the charm anti-charm bound state J/ψ, the photoproduced J/ψs are mainly in the very low momentum region and clearly exceed the hadronic production. However, considering the thermal production of strange quark anti-quark pairs in QGP produced in relativistic heavy-ion collisions, the photoproduced φ is usually smaller than the thermal production and only evident at very peripheral collisions as even their photoproduction is much larger than J/ψ. 相似文献
18.
Charged-particle multiplicity at mid-rapidity in Au-Au collisions at relativistic heavy-ion collider
The particle density at mid-rapidity is an essential global variable for the characterization of nuclear collisions at ultra-relativistic
energies. It provides information about the initial conditions and energy density reached in these collisions. The pseudorapidity
densities of charged particles at mid-rapidity in AuAu collisions at √s
NN = 130 and 200 GeV at RHIC (relativistic heavy ion collider) have been measured with the PHENIX detector. The measurements
were performed using sets of wire-chambers with pad readout in the two central PHENIX tracking arms. Each arm covers one quarter
of the azimuth in the pseudorapidity interval |η| < 035. Data is presented and compared with results from proton-proton collisions
and nucleus-nucleus collisions at lower energies. Extrapolations to LHC energies are discussed. 相似文献
19.
Vector bosons become accessible experimental probes in heavy-ion collisions at the LHC. The capabilities of the LHC experiments
to perform their measurement are outlined. The focus is given to their utility to study the possible formation and properties
of the Quark Gluon Plasma (QGP) in the most central heavy-ion collisions. Their own sensitivity (if any) to the QGP is discussed.
Their interest as references to observe multiple QGP sensitive probes is justified. 相似文献
20.
R. Averbeck 《Progress in Particle and Nuclear Physics》2009,62(2):318-322
The current status of charm and bottom production measurements at RHIC is summarized. Heavy-flavor data from p+p collisions at provide a crucial testing ground for perturbative QCD calculations and serve as a baseline for measurements in nucleus-nucleus collisions. Due to their large mass heavy quarks are produced in hard parton scattering processes in the earliest phase of a nucleus-nucleus collisions such that they can be used to probe the hot and dense medium that is formed in the course of Au+Au collisions at RHIC. 相似文献