1. 1 February 8, 2008 Sunil Dogra QM2008 Jaipur 1 Sunil M. Dogra University of Jammu, India (For the STAR collaboration)‏ Outline Motivation STAR Experiment Analysis Method Results Summary STAR’s measurement of correlation and fluctuations between photons and charged particles at forward rapidity at RHIC

2. 2 February 8, 2008 Sunil Dogra QM2008 Jaipur 2 Motivation  Inclusive photons provide the information of production of    Chiral symmetry restoration could be reflected via study of Photon- Charged particles Fluctuations.  Formation of Disoriented Chiral Condensates (DCC) generate fluctuations between photons and charged particles.  DCC formation is expected to provide information on the vacuum structure of strong interaction and chiral phase transition. Anti-CENTAURO event of JACEE 36 photons, 1 charged particle

3. 3 February 8, 2008 Sunil Dogra QM2008 Jaipur 3 STAR Experiment Nucl.Instrum.Meth.A499:624-632,2003  Coverage: 2.3< |  < 4.0  Event-by-event number of charged particles  Spatial distribution ( ,  ) ‏ and p T of charged particles Coverage: |  < 1.5 Nucl.Instrum.Meth A 499, 713 (2003)

4. 4 February 8, 2008 Sunil Dogra QM2008 Jaipur 4 Photon Multiplicity Detector  Two planes CPV+Preshower  Gas detector of hexagonal cells  Cell cross section : 1.0 cm 2  Cell depth : 0.8 cm  Gas used: Ar+CO 2 in 70:30  Total number of cells : 82,944  Area of the detector : 4.2 m 2  Distance from vertex : 540 cm  Coverage: -2.3 to -3.8 in  with full  Nucl. Instrum. Meth. A 499, 751 (2003)‏

5. 5 February 8, 2008 Sunil Dogra QM2008 Jaipur 5 Principle of Photon Multiplicity detector Photons passing through the converter initiate an electro-magnetic shower and produce large signal on several cells of the sensitive volume of the detector. Hadrons normally affect only one cell and produce a signal representing minimum ionizing particles.

6. 6 February 8, 2008 Sunil Dogra QM2008 Jaipur 6 This Analysis: clusters with N cells > 1 & Cluster ADC > 5*MIP (Purity ~ 67%)‏ Efficiency and Purity of Photon sample % Charged hadrons are rejected by using thresholds on strengths and number of cells on PMD clusters. Raising thresholds on cluster ADC increases purity of photon samples.

7. 7 February 8, 2008 Sunil Dogra QM2008 Jaipur 7 Data Samples AuAu (200GeV) : 1.8 M events CuCu (200 GeV) : 320 K Event cuts: Zvertex <30 cm Photon samples (PMD): cluster ADC > 5 MIP No of cells > 1 Charged tracks (FTPC): dca < 2 cm, nHits > 5, 0.1< p T <3.0 GeV/c

8. 8 February 8, 2008 Sunil Dogra QM2008 Jaipur 8 Cu+Cu 200 GeV Photons Charged Particles Minbias Distribution -----Top 10% Minbias Distribution -----Top 10% Number of Events Au+Au 200 GeV Photon and Charged Particle Multiplicities (Uncorrected)‏

9. 9 February 8, 2008 Sunil Dogra QM2008 Jaipur 9 Study of photon-charged particles fluctuations (Methods)‏    / Mean of ratio (measuring the width)‏   dynamics (measure of total correlated fluctuations)‏

10. 10 February 8, 2008 Sunil Dogra QM2008 Jaipur 10 Fluctuations in N   / N ch  2 /Mean) scaled by N part : almost constant with N part (approximate 1/N part scaling )‏....a+ 1/N part Error bars are Statistical part Measure of Fluctuations =  2 /Mean Error bars are Statistical

11. 11 February 8, 2008 Sunil Dogra QM2008 Jaipur 11 Photon – Charged Particle Fluctuations by dynamics dynamics = Robust variable (almost independent of detector efficiency): (confirmed by Monte Carlo Toy Model)‏ Zero for Poisson-ian fluctuation Charge fluctuations Photon fluctuationsCorrelated fluctuations C. Pruneau et al. Phys. Rev. C 66, 044904(2004)‏ Nystrand et at. Phys. Rev. C 68, 034902(2003)

12. 12 February 8, 2008 Sunil Dogra QM2008 Jaipur 12 Three Terms in dynamics Individual fluctuations are larger than correlation making dynamics positive

13. 13 February 8, 2008 Sunil Dogra QM2008 Jaipur 13 Different cuts on photon samples: 3 MIP 4 MIP 5 MIP 6 MIP Effect of purity and efficiency variation Independent of MIP cuts

14. 14 February 8, 2008 Sunil Dogra QM2008 Jaipur 14 dynamics similar at different  coverage (upstream material effect is small)‏ dynamics :Dependence of  Coverage

15. 15 February 8, 2008 Sunil Dogra QM2008 Jaipur 15 Observation: dynamics scaled by N part : almost constant at lower N part and increases at higher N part Scaling of dynamics with N part

16. 16 February 8, 2008 Sunil Dogra QM2008 Jaipur 16 p T dependence of fluctuations χ B. Mohanty, J Serreau Phys. Reports 414(2005) 263-358 DCC particles are soft Signals expected to increase for lower pt First time access to p T dependence of charged particles (absent in WA98)‏

17. 17 February 8, 2008 Sunil Dogra QM2008 Jaipur 17 No pT dependence on dynamics Small or No DCC signal? dynamics with p T cut of Charged Particles....a+ 1/N part Error bars are Statistical

18. 18 February 8, 2008 Sunil Dogra QM2008 Jaipur 18 Summary  Photon and Charged particle multiplicity correlations are studied for AuAu & CuCu at 200 GeV Collisions at forward rapidities.  Two Method used:   /Mean and dynamics    /Mean of N   /N ch shows approximate 1/N part scaling   dynamics is positive (individual fluctuations > than correlated term)‏   part  *  dynamics almost constant at lower N part and increase for higher N part  No pt dependence -> No abnormal correlations, induced by DCC  An analysis to determine sensitivity of dynamics for DCC is ongoing