Results from PHENIX on deuteron and anti-deuteron production in Au+Au collisions at RHIC

Joakim NystrandUniversity of Bergen

for the PHENIX Collaboration

• The Relativistic Heavy Ion Collider (RHIC)• The PHENIX Experiment• Results on deuterons and anti-deuterons

Joakim Nystrand, University of Bergen

DIS04, High Tatras, Slovakia 14-18 April

The Relativistic Heavy Ion Collider (RHIC)

Collider for heavy nuclei and (polarized) protonsat Brookhaven National Laboratory.

Au+Au @ s = 200 A GeVp+p @ s = 500 A GeV (200 GeV so far)

1.3 km

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 GeVAu+Au @ 63 A GeV (short)p+p @ 200 GeV

System and energies studied so far

This presentation

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

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.

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?

Joakim Nystrand, University of Bergen

DIS04, High Tatras, Slovakia 14-18 April

Characteristics of dense nuclear matter • Energy loss, dE/dx

- suppression of high-pT hadrons- azimuthal jet correlations ( Wolf Holtzmann, Wednesday)

• Pressure- Collective flow, radial and elliptical

• Thermal properties (temperature, chemical potential)- Particle spectra, particle ratios; pT<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)

Joakim Nystrand, University of Bergen

DIS04, High Tatras, Slovakia 14-18 April

The PHENIX detector2 CentralTracking arms

2 Muon arms

Beam-beam counters

Zero-degree calorimeters(not seen)

The PHENIX Detector

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

Joakim Nystrand, University of Bergen

DIS04, High Tatras, Slovakia 14-18 April

Example of a central Au+Au event at snn =200 GeV

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 magneticfield) with the flight-time (from ToF):

Joakim Nystrand, University of Bergen

DIS04, High Tatras, Slovakia 14-18 April

The yield is extracted by fitting the m2 spectrum to a function for the signal (gaussian) + background (1/x or e-x)

Anti-deuteron m2 spectra

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 · 106 events (Au+Au, min.bias) 500 d and 1000 d reconstructed

_

Joakim Nystrand, University of Bergen

DIS04, High Tatras, Slovakia 14-18 April

Correction for acceptance and efficiency normalized d and d pT spectra:

The spectra have been fit to an exp. function in mT, exp( -mT/T)This gives T(d) = 51927 MeV and T(d) = 51232 MeV (min.bias).

_

deuterons anti-deuterons

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.

2

3

3

23

3

p

pp

d

dd dp

NdEB

dp

NdE

Coalescence

A deuteron will be formed when a proton and a neutron are within a certain distance in momentum and configuration space.

where pd=2pp and B2 is the coalescence parameter, B2 1/V. Assuming that n and p have similar d3N/dp3

This leads to:

Imagine a number of neutrons and protons enclosed in a volume V:

The proton yield must be corrected for weak decays

The reality is more complicated…B2 depends on pT not a direct measure of the volume

Possible explanation: Radial flow.

deuterons anti-deuterons

At pT = 1.5 GeV/c , central collisionsB2 RRMS = 7.70.2 fm (d) and 8.00.2 fm (d)

_

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 pT range 1pT4 GeV/c.

• Statistics can be expected to increase by at least a

factor of 10 from Run 4 (this year).