p t spectra of identified hadrons measured with the phenix experiment at rhic
DESCRIPTION
P t Spectra of Identified Hadrons Measured with the PHENIX experiment at RHIC. The detector Hadron identification Corrections to raw distributions M t and P t distributions - minimum bias and as a function of centrality T eff and < p t > versus N part. - PowerPoint PPT PresentationTRANSCRIPT
1/17/01 Julia Velkovska , QM2001
Pt Spectra of Identified Hadrons Measured with the PHENIX experiment at RHIC
Pt Spectra of Identified Hadrons Measured with the PHENIX experiment at RHIC
• The detector
• Hadron identification
• Corrections to raw distributions
• Mt and Pt distributions - minimum bias and as a function of centrality
• Teff and < pt > versus Npart
Julia Velkovska, SUNY at Stony Brook, for the PHENIX collaboration
1/17/01 Julia Velkovska , QM2001
The PHENIX detectorThe PHENIX detector
Hadron identification– drift chamber (DC)
– Pad chamber 1 (PC1)
– Time-of-flight (TOF)
– Beam-beam counters (BBC)
1/17/01 Julia Velkovska , QM2001
PHENIX acceptancePHENIX acceptance
• Trackingdeg
• Time-of-flightdeg
-.4 -.2 0 .2 .4 y
1/17/01 Julia Velkovska , QM2001
Hadron Identification Hadron Identification
• Tracking system: drift chamber , Pad chamber
– momentum measurement
– path length to TOF detector
• Timing system
– beam-beam counters - start time
– Time-of-flight counters - stop time
1/17/01 Julia Velkovska , QM2001
• PID bands defined in
mass2 vs momentum space
ms=0.60.1 mrad
• K cut off at 1.6 GeV/c cut off at 2.2 GeV/c
• protons - up to 5 GeV/c
Particle Id CutsParticle Id Cuts
t = 1205 ps, =2.80.2 mrad,
2222
1
22
2
24
21
224
21
22 41442 pmp
K
c
p
mm
Kpm
Ktms
m
1/17/01 Julia Velkovska , QM2001
Correctionsbased on single particle Monte Carlo
Correctionsbased on single particle Monte Carlo
K
p
Overall scale
•acceptance
•dead areas
•tracking efficiency
Momentum resolution
decays
acceptance Multiplicity dependence- small:
studied by track embedding
into real events
1/17/01 Julia Velkovska , QM2001
Minimum Bias mt distributionsMinimum Bias mt distributions
1/17/01 Julia Velkovska , QM2001
Minimum Bias mt distributionsMinimum Bias mt distributions
Fit ranges in pt :
pions:0.3 < pt < 1.0(GeV/c)
kaons:0.6 < pt < 1.0 (GeV/c)
protons:0.8 < pt < 2.2 (GeV/c)
0.8 < pt < 3 (GeV/c)
anti-protons:0.8 < pt < 2.2 (GeV/c)
1/17/01 Julia Velkovska , QM2001
• negativepions215 +/- 3 +/-
15 MeV
kaons 225 +/- 15 +/- 20 MeV
antiprotons 300 +/- 10 +/- 20 MeV
• positivepions 210 +/- 3 +/- 15 MeV
kaons 220 +/- 15 +/- 20 MeV
protons 320 +/- 10 +/- 20 MeV
• Teff = Tfo + m0 <T>2
Particle inverse slopes in minimum bias eventsParticle inverse slopes in minimum bias events
1/17/01 Julia Velkovska , QM2001
Freeze-out T and flow velocityFreeze-out T and flow velocity
• RHIC Au+Au
– Tfo= 186 +/- 18 MeV
– <t > = 0.36 +/- 0.05
• SPS Pb+Pb
– Tfo = 149 +/- 22 MeV
– <t > = 0.39 +/- 0.04
1/17/01 Julia Velkovska , QM2001
Centrality SelectionCentrality Selection
• Centrality selection based on the correlation between beam-beam counters and ZDC counters
• Number of tracks/event with these selections
1/17/01 Julia Velkovska , QM2001
Pion mt-distributions as a function of centralityPion mt-distributions as a function of centrality
1/17/01 Julia Velkovska , QM2001
Inverse slope versus Npart Inverse slope versus Npart
0 100 200 300 400 0 100 200 300 400
1/17/01 Julia Velkovska , QM2001
• PHENIX 15% CENTRAL+ 212 +/-5 +/- 15 MeV
p 332 +/-10 +/- 20 MeV
• protons at SPS <(NA44+NA49)> 290 +/- 10 MeV
Flow at RHIC and SPS in central eventsFlow at RHIC and SPS in central events
1/17/01 Julia Velkovska , QM2001
Comparison to theory : hydro + cascadeComparison to theory : hydro + cascade
Derek Teaney
• Proton slopes are sensitive to the EOS
• The PHENIX measurement has discriminatory power against various model assumptions
1/17/01 Julia Velkovska , QM2001
Transverse momentum distributions in minimum bias events
Transverse momentum distributions in minimum bias events
• Large proton and anti-proton yield at high pt
• Sort in centrality classes
• In the entire pt range fit:
power law function to exponential - K and p
• extract <pt> from the fit
1/17/01 Julia Velkovska , QM2001
Mean pt versus number of participantsMean pt versus number of participants
• Pionssteep rise and plateau
• Protons gradual rise and
higher <pt>
1/17/01 Julia Velkovska , QM2001
ConclusionsConclusions
• Measured , K, p up to 2.2/1.6/3.5 GeV/c in pt
• Pion spectra nearly independent of Npart beyond the very peripheral collisions
• Kaon inverse slopes are rather similar to those of pions
• Protons/anti-protons inverse slopes rising with Npart
• Proton inverse slopes higher than at SPS.
• High pt hadron yields dominated by protons/anti-protons
1/17/01 Julia Velkovska , QM2001
Charged hadron spectraCharged hadron spectra
• After normalizing the - yield to 0 yield - sum all identified negative hadron spectra
• Compare to non-identified h-
spectra - very good agreement observed
• Significant contribution of anti-protons above
pt = 2 GeV/c