Recent results from PHENIX at RHIC Joakim Nystrand Lund University / University of Bergen The PHENIX...

Recent results from PHENIX at RHIC

Joakim NystrandLund University / University of Bergen

• The PHENIX experiment• Charged particle multiplicity • pT spectra of hadrons at mid-rapidity• Fluctuations (charged particle and pT) • J/e+e–, +–

10th Nordic Meeting on Nuclear Physics,Oslo, May 12-16, 2003.

J. Nystrand, Lund/Bergen10th Nordic Meeting on Nuclear Physics, Oslo, May 12-16, 2003.

What is PHENIX?

PHENIX = Pioneering High Energy Nuclear Interaction eXperimentA large, multi-purpose nuclear physics experiment at the Relativistic Heavy-IonCollider (RHIC)


A world-wide collaboration of 500 physicists from 51 Institutions in 12 countries

The PHENIX collaboration


The PHENIX detector2 CentralTracking arms

2 Muon arms

Beam-beam counters

Zero-degree calorimeters(not seen)


Charged particle tracking: • Drift chamber • Pad chambers (MWPC)

Particle ID: • Time-of-flight (hadrons)• Ring Imaging Cherenkov(electrons)• EMCal (, 0)• Time Expansion Chamber


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


Muon tracking and identificationSouth arm installed for Run2 (01-02) Au+Au, p+pNorth arm installed for Run3 (ongoing) d+Au, p+p

3 Tracking stations - cathode stripchambers

5 Id planes - Iarocci (streamer) tubes + 90 cm steel


Centrality DefinitionCentrality impact parameter

Two measures:

Np : Number of participating nucleons

Ncoll : Number of binary (nucleon-nucleon) collisions


Centrality Determinartion


• Combine the hits in PC1 and PC3. • The result is a sum of true combinations (from real tracks) and combinatorial background. • Determine the combinatorial background by event mixing

MultiplicityHow many particles are produced (at mid-rapidity)? How does the multiplicity scale with centrality, Np or Ncoll?

B=0Experimental Method


Multiplicity per 2 participants

HIJINGX.N.Wang and M.Gyulassy, PRL 86, 3498 (2001)

EKRTK.J.Eskola et al, Nucl Phys. B570, 379 andPhys.Lett. B 497, 39 (2001)

K. Adcox et al. (PHENIX Collaboration), Phys. Rev. Lett. 86(2001)3500


200 GeV130 GeV HIJINGX.N.Wang and M.Gyulassy, PRL 86, 3498 (2001)

Mini-jetS.Li and X.W.Wang Phys.Lett.B527:85-91 (2002)

EKRTK.J.Eskola et al, Nucl Phys. B570, 379 andPhys.Lett. B 497, 39 (2001)

KLND.Kharzeev and M. Nardi, Phys.Lett. B503, 121 (2001)D.Kharzeev and E.Levin, Phys.Lett. B523, 79 (2001)

PHENIX preliminary

Multiplicity at s=200 GeV


PHENIX preliminary

200GeV/130GeV

Stronger increase in Hijing than in datafor central collisions

Multiplicity ratio (200/130) GeV


Variation with snn

To guide the eye

)ln(5.0

1sBA

dy

dN

Nch

p


Hadron Identification with ToF

Combining the momentum informationwith the flight-time:

,K separation pT < 2 GeV/c

p,K separation pT < 4 GeV/c


0 – 5 % 5 -10 %10- 15 %15 – 20 %20 – 30 %30 – 40 %40 – 50 %50 – 60 %60 – 70 %70 – 80 %80 – 93 %

Au+Au at s = 200 GeV PHENIX preliminary

Spectra, spectra, spectra…

Centrality


deuterons and anti-deuterons

A

p

pp

d

dd dp

NdEB

dp

NdE

3

3

23

3

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

)/exp(2

2

efftttevt

d TmAdydmmN

Nd

Yield approximately exp. in mT.


0 Identification with EmCal

Background subtracted

Original spectrum


K. Adcox et al. (PHENIX Collaboration) Phys. Rev. Lett. 88(2002)022301

Suppressed 0 yield at high pT

A remarkable observation:

Yield above pT 2 GeV/c scales with Ncoll in peri-pheral collisions but is suppressed in central collisions!


dydpdN

dydpNdNpR

Tppinelppcoll

TAAEVTTAA

//

/)/1()(

02

02

The ratio RAA

Quantify the deviation from binaryscaling through RAA:

Au+Au 200 GeVS.S. Adler et al. (PHENIX Collaboration)nucl-ex/0304022, submitted to PRL.

p+p 200 GeVS.S. Adler et al. (PHENIX Collaboration)hep-ex/0304038, submitted to PRL.


How do protons scale?proton yield/<binary collisions> for different centralities


proton/pion ratio

p/ 1 for pT > 2 GeV/c


|| 0.35, 0.3 pT 2.0 GeV/c, =/2

Event-by-event fluctuations

Study fluctuations in Q=n+ – n– and Event-by-event <pT>


v(Q) as a function of collision centrality

A small deviation from stochastic emission observed at 130 GeVK. Adcox et al. (PHENIX) PRL 89(2002)082301 No dramatic change at 200 GeV - the upward shift of 0.01 units can be explained by harder track quality cuts leading to a reduced acceptance.

|| 0.35, =/2, 0.3 pT 2.0 GeV/c


Tp

Tp )(Var

random

randomdatapT

F

NrandomTpF

* AuAu 200 GeVPreliminary

o AuAu 130 GeV PHENIX PRC 66(2002)024901

Maximum for semi-central collisions.

FpT related to T:

PHENIX Preliminary

Fp

T (%

)Event-by-event fluctuations


J/ +– , e+e–

Run 2: Central tracking arm(e+e–) + North muon arm (+–)


(pp->J/) = 3.8 + 0.6 (stat) + 1.3 (sys) b

Results pp J/ + X


MagnetMagnetMuon IdentifiersMuon Identifiers

MuonMuon12.5°12.5°

35°35° 35°35°

10.5°10.5°

Run 3 (d+Au, p+p): Both muon arms + Central arm

South: –2.21< <–1.15Central: –0.35< <0.35North: 1.15 < <2.39

x

sMy cc

cc

/ln

4.9 · 10-2 < x2 < 1.7 · 10-1

1.1 · 10-2 < x2 < 2.2 · 10-2

1.7 · 10-3 < x2 < 4.9 · 10-3

cc mainly produced through gluon-gluon fusion

North Central South


J/ in North arm, xAu 10-3

J/ in Central arm, xAu 10-2

J/ in South arm, xAu 10-1

S AuNd

J/ production in d+Au will be sensitive to shadowing in the Au-nucleus:

Shadowing

Eskola, Kolhinen, Vogt Nucl.Phys. A696 (2001) 729-746


First look at data from d+Au

Minv Minv

NorthSouth

Note: N/S not normalized to the same number of events


Conclusions

• Nearly logarithmic increase in multiplicity per

participant with s AGS SPS RHIC

• yield suppressed at high pT

• proton yield not suppressed at high pT (binary scaling)

• J/ measured with muon and central arms

• J/ seen in d+Au data. Important baseline for AuAu;

shadowing in Au.

A lot of new exciting data (only a fraction was shown in this talk)

Recent results from PHENIX at RHIC Joakim Nystrand Lund University / University of Bergen The PHENIX...

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