1. Results from PHENIX on deuteron and anti- deuteron production in Au+Au collisions at RHIC Joakim Nystrand University of Bergen for the PHENIX Collaboration The Relativistic Heavy Ion Collider (RHIC) The PHENIX Experiment Results on deuterons and anti-deuterons

2. Joakim Nystrand, University of Bergen DIS04, High Tatras, Slovakia 14-18 April The Relativistic Heavy Ion Collider (RHIC) Collider for heavy nuclei and (polarized) protons at Brookhaven National Laboratory. Au+Au@  s = 200 A GeV p+p@  s = 500 A GeV (200 GeV so far) 1.3 km

3. Joakim Nystrand, University of Bergen DIS04, High Tatras, Slovakia 14-18 April First run in June 2000: Au+Au @  s = 130 A GeV Second run July 2001 - Jan. 2002: Au+Au @ 200 A GeV p+p @ 200 GeV Third Run Jan. 2003 – May 2003: d+Au @ 200 A GeV p+p @ 200 GeV Fourth Run Jan. 2004 –  May 2004: Au+Au @ 200 A GeV Au+Au @ 63 A GeV (short) p+p @ 200 GeV System and energies studied so far  This presentation

4. Joakim Nystrand, University of Bergen DIS04, High Tatras, Slovakia 14-18 April The goal of relativistic heavy-ion collisions is to study hot and dense nuclear matter The nuclear phase diagram

5. Joakim Nystrand, University of Bergen DIS04, High Tatras, Slovakia 14-18 April Can A+A collisions be understood from parton+parton or nucleon-nucleon interactions? Medium effects present in heavy systems (Au+Au) only, not in light (d+Au). Not entirely, a dense medium is created in the collisions. The produced particle lose energy as they traverse it.

6. Joakim Nystrand, University of Bergen DIS04, High Tatras, Slovakia 14-18 April What are the characteristics of dense nuclear matter? – How can we probe them?

7. Joakim Nystrand, University of Bergen DIS04, High Tatras, Slovakia 14-18 April Characteristics of dense nuclear matter Energy loss, dE/dx - suppression of high-p T hadrons - azimuthal jet correlations (  Wolf Holtzmann, Wednesday) Pressure - Collective flow, radial and elliptical Thermal properties (temperature, chemical potential) - Particle spectra, particle ratios; p T <1-2 GeV/c System size - Intensity Interferometry, Hanbury-Brown Twiss (HBT) Interferometry - Production of Nuclei and anti-nuclei (coalescence) Production of Nuclei and anti-nuclei (coalescence)

8. Joakim Nystrand, University of Bergen DIS04, High Tatras, Slovakia 14-18 April The PHENIX detector 2 Central Tracking arms 2 Muon arms Beam-beam counters Zero-degree calorimeters (not seen) The PHENIX Detector

9. Joakim Nystrand, University of Bergen DIS04, High Tatras, Slovakia 14-18 April Charged particle tracking: Drift chamber Pad chambers (MWPC) Particle ID: Time-of-flight (hadrons) Ring Imaging Cherenkov (electrons) EMCal ( ,  0  ) Time Expansion Chamber Acceptance: |  | < 0.35 – mid-rapidity  = 2  90 

10. Joakim Nystrand, University of Bergen DIS04, High Tatras, Slovakia 14-18 April Example of a central Au+Au event at  s nn =200 GeV

11. Joakim Nystrand, University of Bergen DIS04, High Tatras, Slovakia 14-18 April Charged-particle Identification Central arm detectors: Drift Chamber, Pad Chambers (2 layers), Time-of-Flight. Combining the momentum information (from the deflection in the magnetic field) with the flight-time (from ToF):

12. Joakim Nystrand, University of Bergen DIS04, High Tatras, Slovakia 14-18 April The yield is extracted by fitting the m 2 spectrum to a function for the signal (gaussian) + background (1/x or e -x ) Anti-deuteron m 2 spectra

13. Joakim Nystrand, University of Bergen DIS04, High Tatras, Slovakia 14-18 April The central region is nearly net-baryon free at RHIC The d/d ratio is consistent with (p/p) 2. __ p/p  0.74 _ Statistics: 20 · 10 6 events (Au+Au, min.bias)  500 d and  1000 d reconstructed _

14. Joakim Nystrand, University of Bergen DIS04, High Tatras, Slovakia 14-18 April Correction for acceptance and efficiency  normalized d and d p T spectra: The spectra have been fit to an exp. function in m T,  exp( -m T /T) This gives T(d) = 519  27 MeV and T(d) = 512  32 MeV (min.bias). _ deuteronsanti-deuterons

15. Joakim Nystrand, University of Bergen DIS04, High Tatras, Slovakia 14-18 April How are nuclei and anti-nuclei formed in ultra- relativistic heavy-ion interactions? 1. Fragmentation of the incoming nuclei. Dominating mechanism at low energy and/or at large rapidities (fragmentation region). No anti- nuclei. 2. Coalescence of nucleons/anti-nucleons. Dominating mechanism at mid-rapidity in ultra- relativistic collisions. Only mechanism for production of anti-nuclei.

16. Coalescence A deuteron will be formed when a proton and a neutron are within a certain distance in momentum and configuration space. where p d =2p p and B 2 is the coalescence parameter, B 2  1/V. Assuming that n and p have similar d 3 N/dp 3 This leads to: Imagine a number of neutrons and protons enclosed in a volume V: The proton yield must be corrected for weak decays

17. The reality is more complicated… B 2 depends on p T  not a direct measure of the volume Possible explanation: Radial flow. deuteronsanti-deuterons At p T = 1.5 GeV/c, central collisions B 2  R RMS = 7.7  0.2 fm (d) and 8.0  0.2 fm (d) _

18. Joakim Nystrand, University of Bergen DIS04, High Tatras, Slovakia 14-18 April Conclusions Deuteron/anti-deuteron spectra at mid-rapidity probe the late stages of relativistic heavy ion collisions. Provide a measure of the source size and amount of collective, radial expansion. PHENIX has good statistics for deuterons/ anti-deuterons in the p T range 1  p T  4 GeV/c. Statistics can be expected to increase by at least a factor of 10 from Run 4 (this year).