Rho0 production and possible modification in Au+Au and p+p collisions at square root [sNN] = 200 GeV

We report results on rho(770)(0)-->pi(+)pi(-) production at midrapidity in p+p and peripheral Au+Au collisions at sqrt[s(NN)]=200 GeV. This is the first direct measurement of rho(770)(0)-->pi(+)pi(-) in heavy-ion collisions. The measured rho(0) peak in the invariant mass distribution is shifted by approximately 40 MeV/c(2) in minimum bias p+p interactions and approximately 70 MeV/c(2) in peripheral Au+Au collisions. The rho(0) mass shift is dependent on transverse momentum and multiplicity. The modification of the rho(0) meson mass, width, and shape due to phase space and dynamical effects are discussed.     

String and parton percolation

A brief review to string and parton percolation is presented. After a short introduction, the main consequences of percolation of color sources on the following observables in A-A collisions: suppression, saturation of the multiplicity, dependence on the centrality of the transverse momentum fluctuations, Cronin effect and transverse momentum distributions, strength of the two and three body Bose-Einstein correlations and forward-backward multiplicity correlations, are presented. The behavior of all of them can be naturally explained by the clustering of color sources and the dependence of the fluctuations of the number of these clusters on the density.Arrival of the final proofs: 21 March 2005PACS: 25.75.-q, 12.38.Mh, 24.85. + p     

Fluctuations and correlations in STAR

The study of correlations and fluctuations can provide evidence for the production of the quark-gluon plasma (QGP) in relativistic heavy-ion collisions. Various theories predict that the production of a QGP phase in relativistic heavy-ion collisions could produce significant event-by-event correlations and fluctuations in transverse momentum, multiplicity, etc. Some of the recent results using STAR at RHIC will be presented along with results from other experiments at RHIC. The focus is on forward-backward multiplicity correlations, balance function, charge and transverse-momentum fluctuations, and correlations.     

Fluctuations and transverse momentum distributions in the color clustering approach

We present our results on transverse momentum fluctuations, multiplicity fluctuations and transverse momentum distributions for baryons and mesons in the framework of the clustering of color sources. We determine under what conditions the initial state configurations can lead to color connection, and more specifically, if variations of the initial state can lead to a transition from disconnected to connected color clusters, modifying the number of effective sources. We find that beyond a critical point, one has a condensate, containing interacting and hence color-connected sources. This point thus specifies the onset of color deconfinement. We show that the transverse momentum and multiplicity distributions are related to each other in a defined way. We obtain a non-monotonic dependence of the p _T and multiplicity fluctuations with the number of participants. We present our results for the fluctuations and the transverse momentum distributions at RHIC energies compared to the existing experimental data and our predictions for LHC energies.     

Methods to study event-by-event fluctuations in the NA61/SHINE experiment at the CERN SPS

Theoretical calculations locate the critical point (CP) of strongly interacting matter at energies accessible at the CERN SPS. Event-by-event transverse momentum and multiplicity fluctuations are considered as one of the most important tools to search for the CP. Pilot studies of the energy dependence and the system size dependence of both p _T and multiplicity fluctuations were performed by the NA49 experiment. The NA61/SHINE ion program is a continuation of these efforts. After briefly recalling the essential NA49 results on fluctuations we will discuss the technical methods (removing Non-Target interactions) which we plan to apply for future transverse momentum and multiplicity fluctuation analyses.     

New results from fluctuation analysis in NA49 at the CERN SPS

The exploration of the phase diagram of strongly interacting matter, particularly the study of the phase transition from hadronic to partonic matter and the search for a hypothetical critical endpoint of the first order transition line, is one of the most challenging tasks in present heavy ion physics. New results on chemical (particle ratio), transverse momentum, multiplicity and azimuthal angle fluctuations are presented. We also discuss their connection to the onset of deconfinement and to the critical endpoint.     

Global variables and identified hadrons in the PHENIX experiment

PHENIX measurements related to global variables and identified hadrons are discussed. These include two-pion correlations, elliptic flow, and dN/dη. Measurements of event-by-event fluctuations in mean transverse momentum, mean transverse energy, and net charge are presented for particles within the PHENIX acceptance. The centrality dependence of these measurements is also discussed.     

Measurement of nonrandom event-by-event fluctuations of average transverse momentum in square root of (sNN)=200 GeV Au+Au and p+p collisions

Event-by-event fluctuations of the average transverse momentum of produced particles near midrapidity have been measured by the PHENIX Collaboration in square root of (sNN)=200 GeV Au+Au, and p+p collisions at the Relativistic Heavy Ion Collider. The fluctuations are observed to be in excess of the expectation for statistically independent particle emission for all centralities. The excess fluctuations exhibit a dependence on both the centrality of the collision and on the pT range over which the average is calculated. Both the centrality and pT dependence can be well reproduced by a simulation of random particle production with the addition of contributions from hard-scattering processes.     

Scaling behaviour and correlations in the string fusion model for heavy ion collisions

The KNO scaling, the scaling of multiplicities, the behaviour of fluctuations in the transverse momentum as a function of the multiplicity and the long range correlations in nucleus-nucleus collisions are studied by a Monte Carlo code based on the string fusion model. It is shown that the fusion of strings produces a strong reduction of the long range correlations at high multiplicities, which could be detected experimentally. On the contrary the KNO scaling, the scaling of multiplicities and the behaviour of fluctuations in the transverse momentum are not modified when string fusion is included.On leave of absence from the Department of High Energy Physics, University of St. Petersburg, 198904 St. Petersburg, Russia     

Fluctuations and correlations in the string clustering approach

The fluctuations due to the clustering of color sources can explain the behaviour of the scaled multiplicity variance and transverse momentum fluctuations with centrality. They also predict a nonmonotonic behaviour with centrality for the multiplicity associated to high-p_T events. The clustering of color sources gives rise to an increase in the long-range correlations with centrality as well as to a supression at high centrality with respect to superposition models.     

Inclusive production of charged pions in p+p collisions at 158 GeV/c beam momentum

New results on the production of charged pions in p+p interactions are presented. The data come from a sample of 4.8 million inelastic events obtained with the NA49 detector at the CERN SPS at 158 GeV/c beam momentum. Pions are identified by energy loss measurement in a large TPC tracking system which covers a major fraction of the production phase space. Inclusive invariant cross sections are given on a grid of nearly 300 bins per charge over intervals from 0 to 2 GeV/c in transverse momentum and from 0 to 0.85 in Feynman x. The results are compared to existing data in overlapping energy ranges. Arrival of the final proofs: 8 December 2005     

Event-by-event fluctuations in relativistic nuclear collisions within microscopic transport approach — HSD

In this poster a review of fluctuations within a transport model approach has been presented. The scaled variances of multiplicity fluctuations in nucleus-nucleus collisions at SPS and RHIC energies within the HSD transport model have been studied. The HSD results are compared with the proton-proton data and with predictions of the hadron-resonance gas statistical model. New measurements in a wide range of energies with the large acceptance are necessary. The preliminary data of the PHENIX Collaboration for the scaled variances of the charged hadron multiplicity fluctuations measured in Au+Au at 200 GeV have been analyzed within the model of independent sources. The scanning of the energy and atomic number for the multiplicity fluctuations at the SPS energy range has been also presented.     

Scaling properties of fluctuation results from the PHENIX experiment at RHIC

The PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC) has made measurements of event-by-event fluctuations in the charged-particle multiplicity as a function of collision energy, centrality, collision species, and transverse momentum in several heavy-ion collision systems. It is observed that the fluctuations in terms of σ ²/μ ² exhibit a universal power law scaling as a function of N_participants that is independent of the transverse momentum range of the measurement.     

Multifragmentation of Gold nuclei in the interactions with photoemulsion nuclei at 10.7 GeV/nucleon

Recent results from the EMU-01/12 collaboration are presented for 10.7 GeV/nucleon gold nuclei interactions in emulsion. The distributions of “bound” charge (Z _bound , Z _b3 ), multiplicity distributions, fragment correlations and fluctuations are discussed. The data are compared to similar results obtained on the ALADIN setup at 600 MeV/nucleon. It is shown that multifragmentation of gold nuclei at high and intermediate energies has common features. It is also obtained that the IMFs have reduced multiplicity at high energies. The data are analyzed within the scope of the statistical model of multifragmentation. This model requires the following predetermined model ingredients: mass, charge and excitation energy of nuclear residuals. The simple estimation method of these characteristics is proposed in the framework of the Glauber approach. It is shown that the multifragmentation model reproduces qualitatively the present data. A dramatic discrepancy between the predicted and experimental yield of two charged fragments is found. The evolution of transverse momentum of fragments as a function of Z _bound is presented. It is shown that the model greatly underpredicts the transverse momentum of fragments. It is interpreted as evidence of a strong radial flow of spectator fragments.     

Transverse momentum and total cross section of e(+)e(-) pairs in the Z-boson region from p&pmacr; collisions at sqrt

The transverse momentum and total cross section of e(+)e(-) pairs in the Z-boson region of 66相似文献   

Comparison of the Hard and Soft Processes in High Energy Hadron-Hadron Colisions

Using the“con ealgorithm”in QCD to identify jet,the hard and soft processes in high energy hadroncic olisions are analysed indetail.A Monte Carlo simulation event sample is produced by PYTHIA.The resultant pseudorapidity distribution of jets has a plateau in the central region.The particle and transverse energy density in jets decreases exponentially with the increase of the distance from particles to jet axis.Through comparisons,we find the event average transverse momentum or maximum transverse momentum is positively correlated with multiplicity for the whole event sample,and negatively correlated with multiplicity for jet event subsample.Two ratio variables well describe the hardness of jet events,and they are positively correlated with the event average transverse momentum and negatively correlated with multiplicity,which confirms the event average transverse momentum is a better characteristic quantity to describe the hardness of jet events than multiplicity.     

Inclusive particle spectra in p(π+)n interactions at 195 GeV/c

We present results on single-particle inclusive distributions in p(π⁺)n reactions from a Fermilab experiment using the hybrid 30″ bubble chamber and PWC facility. Distributions in rapidity, y, Feynman x and p²_T for π⁺ and π^? are presented and compared with other experiments. The effects of different targets and projectiles (neutrons, protons and pions) on the distributions are demonstrated and discussed in terms of projectile and target fragmentation. The average transverse momentum 〈P_T〉 is studied as a function of x, y and multiplicity.     

On the moment-order dependence of intermittency in hadron-hadron collisions

The dependences of intermittency degree on moment-order, multiplicity and transverse momentum are discussed. The different dependences of intermittency degree on moment order at different energies are utilized to show that the dependences of intermittency degree on multiplicity are in opposite directions in low and high energy regimes. It is argued that these different trends imply that intermittency degree depends on other more basic quantity, such as transverse momentum.