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

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

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, (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

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

QM08 02/04/08--02/10/08 5 Data Set RHIC Run 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)

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, (2005)

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

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(stat) ± 0.05 (syst)

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.

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.

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

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

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, (2004)

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

QM08 02/04/08--02/10/08 15 Deuterons R cp Deuterons’ p T divided by 2 Proton spectra from: Phys. Rev C 69, (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

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

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

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:

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, (2005)

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

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

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