1. Source Dynamics from Deuteron and Anti-deuteron Measurements in 200 GeV Au+Au Collisions Hugo E Valle Vanderbilt University (For the PHENIX Collaboration) Quark Matter 2008, Jaipur India

2. QM08 02/04/08--02/10/08 2 Outline Motivation Deuteron Identification and the Time of Flight Detector Spectra and Ratios Coalescence Parameter (B 2 ) and Source Radius R CP Conclusion

3. QM08 02/04/08--02/10/08 3 Physics Motivation Why are deuterons interesting? -Low p T : -Spectral shapes change with mass due to radial flow - Information on source size complementary to HBT measurements PHENIX: Phys. Rev. C 72, 014903 (2005) Au+Au collisions at  s NN = 200 GeV -Intermediate-High p T : –Baryon-Meson difference in suppression –Possibly due to quark recombination –Study the coalescence of baryons with deuteron R cp

4. QM08 02/04/08--02/10/08 4 TOF.W New MRPC TOF in West arm for Run 7 ~75 ps resolution Coverage | η |<0.35 Δφ = 22° Drift Chamber (DC) and Pad Chamber 1 (PC1)- for momentum Pad Chamber (PC3) outer tracking Time of Flight (TOFW) for timing

5. QM08 02/04/08--02/10/08 5 Data Set RHIC Run 7 200 GeV Au+Au Collisions Analyzed 1.9 billion events (half of available data) Tracks reconstructed using TOF.W, and central tracking chambers. High quality Drift Chamber tracks 2.0  TOF.W and PC3 spatial matching cuts in azimuth and z (beam-axis)

6. QM08 02/04/08--02/10/08 6 Deuteron & Anti-deueron Extraction Fitted a Gaussian + background function (e -x ), to obtain yield. pTpT pTpT m2m2 Large data sample analyzed in centrality classes: 0-10% 10-20% 20-40% 40-60% 60-92% Extend both p T range and centrality selection from previous measurements Ref Phys. Rev. Lett. 94, 122302 (2005)

7. QM08 02/04/08--02/10/08 7 Deuteron and anti-deuteron Spectra MC Correction Factors: Acceptance MRPC (TOF.W) Efficiency Tracking Efficiency Survival Probability Tracks Cuts

8. QM08 02/04/08--02/10/08 8 Anti-deuteron/Deuterons Ratio ratio vs p T No p T. and no centrality dependence ( within errors ) Consistent with (pbar/p) 2 ratio 0.73 ± 0.01 0.46 ± 0.01(stat) ± 0.05 (syst)

9. QM08 02/04/08--02/10/08 9 Radial Flow in Hadron m T Spectra Slope of spectra for deuterons at 0-10% is smaller due to Radial Flow Consistent with other particles in peripheral collisions.

10. QM08 02/04/08--02/10/08 10 Coalescence Parameter B 2 Defined as: with p d = 2p p The coalescence factor B 2, characterizes the coalescence probability, depends on the fireball size.

11. QM08 02/04/08--02/10/08 11 Coalescence Parameter B 2 increases from central to peripheral collisions B 2 rises with p T

12. QM08 02/04/08--02/10/08 12 B 2 and System Volume Significant change in B 2 from 14.5 to 60 N part 1/B 2 vs N part shows a consistent linear rise

13. QM08 02/04/08--02/10/08 13 Centrality dependence of Source size Shows linear increase as the cubic root of the number of participants (N part ). Consistent with HBT radii for pions. Phys.Rev.Lett.93, 152302 (2004)

14. QM08 02/04/08--02/10/08 14 Energy Dependence of B 2 Parameter Comparison of B 2 parameter for deuterons and anti-deuterons (p T =1.3 GeV) with other experiments at different values of sqrt(s) Seems consistent between SPS and RHIC AGSSPSRHIC

15. QM08 02/04/08--02/10/08 15 Deuterons R cp Deuterons’ p T divided by 2 Proton spectra from: Phys. Rev C 69, 034909 (2004) Rcp for deuteron affected by two factors: Centrality dependence of B 2 Scaling of production yields for protons and neutrons Rcp of neutrons is consistent with that of protons

16. QM08 02/04/08--02/10/08 16 Conclusions Measured (Anti-)Deuteron spectra for Run7 Expanded the range of our previous measurement both at low and at high p T Detailed study as a function of centrality m T spectra are consistent with radial flow Extracted coalescence parameter (B 2 ) and source radius at freeze-out as a function of p T and N part Source radius decreases with p T Source radius increases linearly with N part 1/3 consistent with expanding source B 2 measurement indicates that the freeze-out conditions are similar at SPS and RHIC energies. R cp for (Anti-)Deuterons reveals that neutron production is similar to that of protons

17. QM08 02/04/08--02/10/08 17 BACKUP

18. QM08 02/04/08--02/10/08 18 R cp for neutrons Since R cp for deuterons reaches 2.7, the neutron yield has to increase faster than N part from central to peripheral collisions. Assuming it increases as N coll we get:

19. QM08 02/04/08--02/10/08 19 Raw (Anti-)Deuteron Spectra Large data sample analyzed in centrality classes: 0-10% 10-20% 20-40% 40-60% 60-92% Extend both p T range and centrality selection from previous measurements Ref Phys. Rev. Lett. 94, 122302 (2005)

20. QM08 02/04/08--02/10/08 20 PHENIX acceptance for different particles

21. QM08 02/04/08--02/10/08 21 Survival Probability

22. QM08 02/04/08--02/10/08 22 Implications for It has been shown p T shape of Since scaled yields (or B 2 ) are equal within errors, it is suggestive: pbar/p = 0.73 ± 0.01