Results from PHENIX on deuteron and anti- deuteron production in Au+Au collisions at RHIC Joakim Nystrand University of Bergen for the PHENIX Collaboration.

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



• 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



The goal of relativistic heavy-ion collisions is to study hot and dense nuclear matter

The nuclear phase diagram



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.



What are the characteristics of dense nuclear matter?– How can we probe them?



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)



The PHENIX detector2 CentralTracking arms

2 Muon arms

Beam-beam counters

Zero-degree calorimeters(not seen)

The PHENIX Detector



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



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



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):



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



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

_



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



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)

_



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).

Results from PHENIX on deuteron and anti- deuteron production in Au+Au collisions at RHIC Joakim Nystrand University of Bergen for the PHENIX Collaboration.

Documents

gev au au

gev slide

university of bergen

high tatras

au collisions

gev p p

heavy systems au au

central au au event