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