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