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1.
A significant asymmetry in baryon/antibaryon yields in the central region of high energy collisions is observed when the initial state has nonzero baryon charge. This asymmetry is connected with the possibility of baryon charge diffusion in rapidity space. Such a diffusion should decrease the baryon charge in the fragmentation region and translate into the corresponding decrease of the multiplicity of leading baryons. As a result, a new mechanism for Feynman scaling violation in the fragmentation region is obtained. Another numerically more significant reason for the Feynman scaling violation comes from the fact that the average number of cut Pomerons increases with initial energy. We present the quantitative predictions of the Quark-Gluon String Model for the Feynman scaling violation at LHC energies and at even higher energies that can be important for cosmic ray physics. 相似文献
2.
A new geometrical scaling method with a gluon saturation rapidity limit is proposed to study the gluon saturation feature of the central rapidity region of relativistic nuclear collisions. The net-baryon number is essentially transported by valence quarks that probe the saturation regime in the target by multiple scattering. We take advantage of the gluon saturation model with geometric scaling of the rapidity limit to investigate net baryon distributions, nuclear stopping power and gluon saturation features in the SPS and RHIC energy regions. Predictions for net-baryon rapidity distributions, mean rapidity loss and gluon saturation feature in central Pb+Pb collisions at the LHC are made in this paper. 相似文献
3.
C. Merino C. Pajares Yu. M. Shabelski 《The European Physical Journal C - Particles and Fields》2011,71(5):1652
We consider the first LHC data for pp collisions in the framework of Regge theory. The integral cross sections and inclusive densities of secondaries are determined
by the Pomeron exchange, and we present the corresponding predictions for them. The first measurements of inclusive densities
in the midrapidity region are in agreement with these predictions. The contribution of the baryon-number transfer due to String
Junction diffusion in the rapidity space is at the origin of the differences in the inclusive spectra of particle and antiparticle
in the central region, and this effect could be significant at LHC energies. We discuss the first data of ALICE and LHCb collaborations
on the baryon/antibaryon asymmetry at LHC. 相似文献
4.
Taking the conservation of baryon number into account in a non-uniform flow model, the rapidity distribution of the net protons at the LHC is predicted. The energy dependence of the rapidity distribution, baryon stopping and collective flow from BNL/AGS to CERN/LHC are systematically investigated. 相似文献
5.
It is shown that slow valence quark in the wave function of high energy proton can fragment into a baryon if the fast diquark-spectator is destroyed, i.e. is turned from the antitriplet to the sextet colour state. We estimated the cross section of the baryon number flow to the central rapidity region using the perturbative QCD. It depends on the rapidity gap Δy as exp (-Δy/2) and nicely agrees with the data at ISR energies, There exists also an intriguing possibility to transfer baryon number by means of gluonic exchanges only. This contribution does not depend on rapidity at all and becomes sizable in TeV energy region. We propose also new mechanisms for baryonantibaryon production from vacuum, transfer of polarization over large rapidity intervals, and nuclear stopping power. 相似文献
6.
B. Kämpfer O. P. Pavlenko M. I. Gorenstein A. Peshier G. Soff 《Zeitschrift für Physik A Hadrons and Nuclei》1995,353(1):71-77
The influence of a non-vanishing baryon charge on the rapidity distribution of dileptons produced in ultrarelativistic heavy-ion collisions is studied. We employ a frozen motion model with scaling invariant expansion of the hadronizing quark-gluon plasma as well as a realistic rapidity distribution of secondary particles (i.e., pions and baryons) expected for RHIC energies. We demonstrate a sizeable suppression of the thermal dilepton yield at large rapidities due to the finite baryon density. This affects the most favorable rapidity window for using dileptons for the diagnostic of the quark-gluon plasma and the early temperature distribution of the hot reaction zone. To discriminate the thermal dileptons from Drell-Yan background we propose to utilize the dilepton yield scaled suitably by the pion multiplicity as function of rapidity. 相似文献
7.
Strong chromofields generated at early stages of ultrarelativistic nuclear collisions may explain not only creation of the
quark-gluon plasma but also collective deceleration of net baryons. This is demonstrated by solving classical equations of
motion for baryonic slabs under the action of a time-dependent chromofield. We have studied sensitivity of the slab trajectories
and their final rapidities to the initial strength and decay time of the chromofield, as well as to the back reaction of the
produced plasma. By proper choice of the initial chromofield energy density we can reproduce significant baryon stopping,
an average rapidity loss of about two units, observed for Au + Au collisions at RHIC. Using a Bjorken-like hydrodynamical
model with the particle production source, we also study the evolution of partonic plasma produced as the result of the chromofield
decay. Due to the delayed formation and expansion of plasma its maximum energy density is significantly lower than the initial
energy density of the chromofield. It is shown that the fluctuations of the chromofield due to the stochastic distribution
of color charges help to populate the midrapidity region in the net-baryon distribution. To fit the midrapidity data we need
the chromofields with initial energy densities in the range of 30 to 60 GeV/fm3. Predictions of baryon stopping for Pb + Pb collisions at LHC energies are made. 相似文献
8.
G.H. Arakelyan C. Merino C. Pajares Y.M. Shabelski 《The European Physical Journal C - Particles and Fields》2008,54(4):577-581
We consider the phenomenological implications of the assumption that baryons are systems of three quarks connected through
a gluon string junction. The transfer of baryon number in rapidity space due to the string junction propagation is considered
in detail. At high energies this process leads to a significant effect on the net baryon production in hN collisions at midrapidities.
The numerical results for midrapidity inclusive densities of different secondaries in the framework of the quark–gluon string
model are in reasonable agreement with the experimental data. One universal value, λ≃0.25, for the strangeness suppression
parameter correctly describes the yield ratios of Λ/p, Ξ/Λ, and Ω/Ξ. The predictions for pp collisions at LHC energies are
also presented.
PACS 25.75.Dw 相似文献
9.
The transverse-energy flow generated by minijets in hadron and nuclear collisions into a given rapidity window in the central
region is calculated in the next-to-leading-order (NLO) in QCD at RHIC and LHC energies. The NLO transverse-energy production
in pp collision cross sections is larger than that in the leading-order (LO) ones by the factors of and at RHIC and LHC energies, respectively. These results were then used to calculate the transverse-energy spectrum in nuclear
collisions in a Glauber geometrical model. We show that accounting for NLO corrections in the elementary pp collisions leads
to a substantial broadening of the distribution for the nuclear ones, while its form remains practically unchanged.
Received: 11 May 1999 / Published online: 22 October 1999 相似文献
10.
A. Giovannini R. Ugoccioni 《The European Physical Journal C - Particles and Fields》2004,36(3):309-313
The study of possible new physics signals in global event properties in pp collisions in the TeV energy domain is extended from full phase-space to rapidity intervals experimentally accessible at LHC. The elbow structure in the total multiplicity distribution predicted in full phase-space is clearly present also in restricted rapidity intervals, leading to very strong charged particle correlations. It is also found that energy densities comparable to those reached in heavy ion collisions at RHIC could be attained in pp collisions at LHC.Received: 3 March 2004, Published online: 23 July 2004 相似文献
11.
We present lattice QCD results along the freezeout curve of heavy-ion collisions. The variance, skew and kurtosis of the event distribution of baryon number are studied through Padé resummations. We predict smooth behaviour of three ratios of these quantities at current RHIC and future LHC energies. Deviations from this at lower energies signal the presence of a nearby critical point. 相似文献
12.
We survey the utility of net baryon number fluctuations in a rapidity interval as a probe of baryon production in nuclear collisions. 相似文献
13.
Universal scaling of kinetic freeze-out parameters across different collision systems at LHC energies 下载免费PDF全文
In this study, we perform Tsallis Blast-Wave analysis on the transverse momentum spectra of identified hadrons produced in a wide range of collision systems at the Large Hadron Collider (LHC) including pp, pPb, XeXe, and PbPb collisions. The kinetic freeze-out properties varying with event multiplicity are investigated across these systems. We find that the extracted kinetic freeze-out temperature, radial flow velocity, and non-extensive parameter exhibit a universal scaling behavior for these systems with very different geometric sizes, especially when the independent baryon Tsallis non-extensive parameter is considered. This universality may indicate the existence of a unified partonic evolution stage in different collision systems at the LHC energies. 相似文献
14.
In this paper, the gluon distribution is extracted from the KLR-AdS/CFT saturation model and used to investigate net-baryon and net-kaon rapidity distributions in ultrarelativistic heavy-ion collisions. With the same parameters of the saturation model fitting to HERA data and an χ2 analysis of the overall constant C, the theoretical results are in good agreement with RHIC data in Au+Au collisions at √s=0.2 TeV. Then, we present the predictive results for net-baryon rapidity distributions in central Pb+Pb collisions at LHC energies of √s=2.76, 3.94, and 5.52 TeV, and give the corresponding values of d N/d y for net-baryon at y=0. 相似文献
15.
We provide predictions for the J/ψ coherent production in the peripheral heavy ion collisions at LHC and RHIC using the leading twist model of nuclear shadowing based on the QCD factorization theorem for diffraction and the HERA hard diffraction data. We demonstrate that for LHC kinematics this model leads to a bump-shape distribution in rapidity which is suppressed overall as compared to the expectations of the color transparency regime by a factor 6. This is a significantly larger suppression than that expected within the impact parameter eikonal model. Thus we show that the interaction of spatially small wave package for which the total cross section of interaction with nucleons is small is still strongly shadowed by nuclear medium in high energy processes. 相似文献
16.
We investigate the cold nuclear matter(CNM) effects on isolated prompt photon and isolated prompt photon associated jet productions in nuclear collisions at the NLO accuracy by using the EPS09 NLO nuclear parton distribution functions and their error sets.Nuclear modification factors of isolated prompt photon and isolated prompt photon+jet productions due to CNM effects in p+A and A+A reactions at the RHIC and the LHC are provided with varying rapidity and transverse momentum of the final state photon.It is shown that the CNM effects on isolated prompt photon and photon+jet are modest,which give a small enhancement at low pT region and a more obvious suppression at large pT at central rapidity.At forward rapidity a pronounced suppression of γ as well as γ+jet is always observed. 相似文献
17.
Recent ALICE data for the multiplicity distributions in the central rapidity bins at LHC energies are compared with the results from two default versions of the PYTHIA 8 generator. We find that, contrary to the earlier versions of PYTHIA, the model overestimates the increase of average multiplicity with energy. Tuning two of the model parameters one obtains reasonable agreement with data. The dependence of the normalized moments of the distribution on the rapidity bin width and on energy is also qualitatively correct. 相似文献
18.
The maximum baryon and energy densities reached in the fragmentation regions of nuclear collisions are estimated with a new hydrodynamical model. Unlike previous models where recoil is included as a source term for the baryon current, in our model the baryon current is strictly conserved. The parameters of the model are furthermore adjusted to take into account the large baryon rapidity shifts observed recently in p + A → p + X. The implications for the production of high baryon density quark-gluon plasmas are discussed. 相似文献
19.
We present a model for hadron production in the proton fragmentation region in pp collisions at the CERN Large Hadron Collider which accounts for the first time for effects of very strong small x gluon fields. Average transverse momenta acquired by the valence quarks exceed 1 GeV/c for central collisions and result in the suppression of leading baryon production and an additional energy flow to smaller rapidities. A strong dependence on the impact parameter will allow one to investigate the propagation of leading partons through gluon fields of a strength comparable to the ones encountered in heavy ion collisions at the LHC and in cosmic-ray-air interactions at highest energies. 相似文献
20.
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