Results from STAR and status of the FTPC

Results from STARand status of the FTPC

María J. Mora Corral

Project Review 2002 MPI

M.J. Mora Corral Project Review MPI München, 16/Dec/2002

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Forward TPC group• Permanent Physicists

– V. Eckardt, P. Seyboth• Computing

– J. Seyboth, M. Vidal• Postdocs

– M. Oldenburg (1/2003), M.J. Mora Corral• Ph.D. Students

– J. Putschke, F. Simon• Diploma Student

– P. MaierbeckLots of help from MPI technical and computing support


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Outline

• Heavy ion collisions at RHIC• The STAR experiment• Highlights from STAR

– Particle ratios– Anisotropic flow– Suppression at high pT

• Forward TPC from MPI-München• Summary and outlook


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How does matter look at high density and temperature?

High Density QCD Matter inLaboratory Determine its properties

QCD Prediction: Phase Transitions Deconfinement to QGP Chiral symmetry restoration

Relevance to other research areas? Quark-hadron phase transitionin early Universe Cores of dense stars High density QCD


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The Relativistic Heavy Ion Collider

STARPHENIX

PHOBOS BRAHMS

RHIC

Design Performance Au + Au p + pMax snn 200 GeV 500 GeVL [cm-2 s -1 ] 2 x 1026 1.4 x 1031

Interaction rates 1.4 x 103 s -1 6 x 105 s -1

Ions: A = 1 ~ 200, pp, pA, AA, AB

two superconducting rings3.83 km in circumference


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Time of Flight Patch

The STAR experimentSTAR uses the world’s largest Time Projection Chamber

Trigger Barrel +

Ring Imaging Cerenkov

Zero Degree Calorimeter

1st year detectors (2000)Au+Au @ 130 AGeV

EMCal Barrel +

Forward Time Projection Chamber

2nd year detectors(2001-2002)Au+Au and p+p @ 200 AGeV

Silicon Vertex Tracker +Silicon Strip Detector

Photon Multiplicity Detector

3rd year detectors(2003)d+Au and p+p @ 200 AGeV

End Cap EMC


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a STAR event …One of the first Au+Au events at CM energy of 200 AGeV

• Efficient tracking and momentum measurement• Particle identification: dE/dx invariant mass topologicalp, p-bar, +, -, K+, K- , -bar-bar-bar…


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p-bar/p ratios

YpbarYp

Ypair

Ypair YTr0.8

YpairYTr

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• Pair-production increases with collision energy.

• Mid-rapidity region is not yet baryon-free!

• Pair-production is larger than baryon transport.

• 80% of protons from pair production.

______

STAR preliminary

Early Universe p-bar/p ratio


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Particle ratios

• STAR excels in particle yields study! (and good agreement between different experiments ).

• Evidence for thermal equilibrium at high temperature and density.• RHIC increasing s: same temperature, decreasing baryon density.


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Azimuthal anisotropy (flow)

STAR Preliminary 130GeV

Fourier analysis

1+2v1cos(lab-plane)+2v2cos2(lab-plane)+…

Non-central collisions: spatially asymmetric initial state

lab-plane

Anisotropic flow

Final state azimuthal momentum asymmetry

Interactions


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STAR Preliminary 130GeV

Elliptic flow

• At moderate pT the elliptic flow is well described by hydro models, even for different particles.

• At high pT the trend can be reproduced including hard scattering with an energy loss.

PRL 86, 402 (2001) & nucl-ex/0107003


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High pT particles and suppression• Jets and mini-jets at s = 200GeV

– 30-50 % of particle production– High pt leading particles– Azimuthal back-to-back correlations

• Extend into perturbative regime– Calculations reliable (?)

• Scattered partons propagate through matter &radiate energy (dE/dx ~ x) in colored medium – Interaction of parton with partonic matter– Suppression of high pt particles: “jet quenching”– Suppression of back-to-back correlations– Creation of event-plane correlations

hadrons

q

q

hadronsleadingparticle

leading particle

schematic view of jet production

QGP

Vacuum


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High pT particle suppression

Evidence for hadron suppression at high pt

Partonic interaction with matter? dE/dx?

Preliminary

• Scale Au-Au data by the number of binary collisions

• Compare to UA1pp reference data measured at 200 GeV


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The forward TPC

• 2 FTPCs with 1.20 m length. • Rinner = 7.73 cm, Router = 30.05cm.• Covering || region 2.5-4.0.• 10 padrows in the beam direction with 6

azimuthal sectors each.• Efield radial, 240-1400V/cm, beam.• B field =0.5 T, || beam.• Gas mixture 50%Ar 50%CO2.

• Extend STAR charged particle acceptance into region 2.5 < || < 4.0.

• Study charged particle and net proton (h+-h-) spectra.

• Anisotropic flow.• Ks

0 and production.• Fluctuations of <pT>.• DCC search.

Bfield

Efield


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The forward TPC: What is new?PROBLEM: Region with high particle multiplicity achieve high two track separation

SOLUTION: Apply a radial electric field ( magnetic field)

COMPLICATIONS: Drift velocity not constant. Drift path curved due to ExB deflection.

vD(r) and D(r) need to be known with high accuracyWe use MAGBOLTZ calculations

Very sensitive

to calibration

co n st)()(v

co n st)(vv1

rFBrqFBE

rr

E

D

DD

l e )L o r e n t z a n g(

)(

r)(v

)(

L

D

0

00

r

r

LD

r

r

r

rD

d rrr

rd r

d trT


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From signals to tracksCharge signals (pad, time)

Cluster finder +Cluster unfolding

Hits (pad, time)

Magboltz drift maps

Space points (r,)

Track finder

Track (space point collection from same

particle)

Vertex extrapolation

Laser tracks+Drift Vel. Monitor


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Example: Charge step sensitivity

Sector numberR

adiu

s st e

p (c

m)

Drift time

Charge-step (maximum drift time of the electrons) shows a hardware sector wise structure

azimuthal dependence cluster position!

Sensitive to small (200 m) inaccuracy in detector geometry which leads to 2mm fluctuation!!

200m shift


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FTPC raw multiplicity vs TPC,CTB

no quality cuts applied on FTPC tracks (primaries & secondaries)

Good correlation between FTPCand TPC, CTB multiplicity.

FTPC multiplicity

TPC

mul

tiplic

ity

FTPC multiplicity

CTB

mul

tiplic

ity


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Raw charged particle spectra

pt [GeV]

1/N

even

t*dN

/dp t

1/

Nev

ent*d

N/d

Efficiency and acceptance calculations have startedto extract corrected charged particle spectra !

pT distribution distribution


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FTPC event plane correlations

• Elliptic flow (v2) visible in the FTPCs

• Directed flow (v1) signal is very small

firstharmonic

secondharmonicV1= V2=

FTPCEast/FTPCWestFTPCEast/FTPCWest

FTPCt/TPC

v2


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FTPC elliptic flow

• Not final results• Elliptic flow decreases with pseudorapidity?


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Summary and outlook• Exciting new results from STAR year II

– Net baryons have continued to decrease with increasing energy, although there’s still some stopping/baryon transport to ycm.

– Hadronic particle yields reveal a statistical behaviour.– Suppression of particles and azimuthal correlations at high pT

indicate parton energy loss in the medium.

• First year with the FTPC– 90K minBias, 1.6M central Au+Au events and 15M p+p events

collected.– Radial drift and ExB effects make calibrations challenging.– Spectra and anisotropic flow studies in progress.

• Plans for next Run (January-May 2003)– 10 weeks d+Au and 3 weeks polarized p+p collisions.– Improved laser and DV calibrations.

• Continuation of data taking in 2003-2004


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Efficiencies

• First approach to efficiencies with simulations.

• For final efficiencies we need to embed a simulated particle into real event.

Results from STAR and status of the FTPC

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