BEAM-ENERGY DEPENDENCE FOR MULTIPLICITY FLUCTUATION

1. BEAM-ENERGY DEPENDENCE FOR MULTIPLICITY FLUCTUATION (FROM RHIC TO LHC) MAITREYEE MUKHERJEE,VECC

2. MOTIVATION: • To study fluctuation in charged particles for heavy-ion collisions. • To study relative fluctuation in charged particles as a • function of centrality. • To study beam-energy dependence of charged multiplicity • fluctuation (from RHIC to LHC.) • To study the same thing using real data and see whether • we get any enhanced fluctuation.

3. To study the centrality dependence of charged particle multiplicity fluctuations, at first the distribution for Npart,i.e, the number of nucleons participating in the collision, has been Plotted. Here the result has been shown for Au+Au collision at 7.7 GeV. Now, Npart is directly proportional to many quantities that are experimentally observed, such as number of produced charged particles,i.e,Nch.Here the correlation plot between these two quantities has been shown for Au+Au collision at 7.7GeV. So, centrality selection from Npart is quite justified

4. The whole analysis has been done for central region, • i.e, -0.5<η<0.5 and pt<2.0 GeV. • Centrality Selection has been done using integral from minimum bias • distribution of Npart. • Minimum bias distributions for Nch using the above cuts have been • shown for all the beam-energies(from RHIC to LHC) in the next slide.

6. For a particular centrality bin, Nch distribution is a gaussian. The plot shown here is for Au+Au collision at 200GeV for 8-10% cs. The distribution is fitted to gaussian. Relative fluctuation of charged multiplicity is given by, where σ is the rms and N is the mean of the gaussian distribution. In WA98 experiment,the centrality dependence of charged particle multiplicity fluctuations had been found to agree reasonably well with those obtained from participant model,where, N: particle multiplicity ni: no of particles produced by i-thparticipant,within the acceptance of the detector.

7. We determine fluctuation here for narrow bins in centrality (~2% cs bins ) such that fluctuations in Npart is unity. The plots here has been shown from WA98 Expt results. Now,if all such gaussian distributions are plotted together for a particular energy,we get back the minimum bias distribution. In next slide,this is shown by plotting gaussian distributions for 2-4%,12-14%,30-32% and 60-62% cs for each energy.

9. Now, the distributions for mean, sigma and relative fluctuation of charged particle multiplicities have been shown here as a function of %cs , for each energy.

14. BEAM-ENERGY DEPENDENCE OF Wch FOR PARTICULAR CENTRALITY BINS

15. FUTURE PLANS : To study event-by-event multiplicity fluctuation in charged particles using real data. I will analyze LHC11h AOD115 data for Pb+Pb at 2.76TeV.

16. THANK YOU

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