Charge Particle Multiplicity and Transverse Energy Measurements in AuAu collisions in PHENIX at RHIC

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Charge Particle Multiplicity and Transverse
Energy Measurements in Au-Au collisions in PHENIX
at RHIC
QM2002, July 18, 2002 A.Bazilevsky RIKEN BNL
Research Center for the PHENIX Collaboration
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Motivation

• Provides information regarding the dynamics of
  nucleus-nucleus collisions
• Initial conditions, energy density of the system
• Scaling with Ös
• Mechanism of particle production, soft vs hard
• Constrain theoretical predictions

Results presented vs ÖsNN and centrality
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PHENIX Setup, Year-2

• Charged Multiplicity
• Pad Chambers
• RPC1 2.5 m
• RPC3 5.0 m
• ?lt0.35, ???
• Transverse Energy
• Lead-Scintillator EMCal
• REMC 5.0 m
• ?lt0.38, ?? (5/8)?
• Trigger
• Beam-Beam Counters
• 3.0lthlt3.9, ?? 2?
• Zero-Degree Calorimeters
• h gt 6, Z18.25 m

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Charged Multiplicity Measurements
B0

• Count tracks on a statistical basis
• (no explicit track reconstruction)
• Combine all hits in PC3 with all hits in PC1.
• Project resulting lines onto a plane through the
  beam line.
• Count tracks within a given radius.
• Determine combinatorial background by event mixing

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Transverse Energy Measurements
EMCal absolute energy calibration MIP (min.
ioniz. part.) peak E/p matching peak for e? ?0
mass peak
Convention Ei Eitot-mN for baryons Ei
EitotmN for antibaryons Ei Eitot for others
EMCal is almost hadronic calorimeter EEMC
1.0? Etot for ?, ?0 EEMC 0.7? Etot for ??
?0???
ETEMC ? ET transformation ET 1.23?ETEMC
Inflow, losses Response to hadrons
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Corrections
Charged particle multiplicity Tracks outside
acceptance window 4 Inactive
regions 10 Double hit resolution hit
losses 15 (most central) background
subtraction 3.6 In-flight particles decay
0.2 Geometrical acceptance ?2.89 Transverse
energy Inactive regions 1
Inflow 24 Losses 18 Response (to
hadrons) 0.83 Geometrical acceptance ?4.18
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Improved Year-1 (?sNN 130 GeV) analysis

• Trigger
• Improved event selection
• Trigger efficiency definition in Year-1 data
  relative to Year-2 data for better comparison of
  ?sNN 130 GeV and 200 GeV results
• Transverse Energy
• New definition explicitly accounting for nucleon
  masses (4 increase)
• Correction based on measured particle ratios
  instead of HIJING
• Charged Particle Multiplicity
• In-flight decay correction based on measured
  particle ratios and pt instead of HIJING

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Centrality Selection
ZDC vs BBC
Define centrality classes ZDC vs BBC Extract
N participants Glauber model
ET
EZDC
b
QBBC
Nch
Nch
PHENIX preliminary
PHENIX preliminary
ET
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Centrality dependence
ET and Nch exhibit consistent behavior at
?sNN130 GeV and 200 GeV
PHENIX preliminary
Stat. errors Negligible Syst. errors Band
possible common tilt Bars total syst. error
PHENIX preliminary
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200 GeV / 130 GeV
For the most central collisions
PHENIX preliminary
PHENIX preliminary
Constant scaling within syst. errors
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ltETgt / ltNchgt
PHENIX preliminary
PHENIX preliminary
Independent from energy
Independent from centrality
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Nch at RHIC
Consistency of RHIC results PHENIX two layers
of PCs, 3m and 5m from the vertex in B0 STAR
full tracking in TPC in magnetic field PHOBOS
vertex detector and spectrometer BRAHMS silicon
detectors and scintillator arrays
PHENIX preliminary
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Centrality dependence vs ?sNN
PHENIX preliminary
Fit dX/d? ? Npart? CERES (?sNN8.7
GeV) dNch/d? ?1.09 WA98 (?sNN17.2
GeV) dNch/d? ?1.07?0.04 dET/d?
?1.08?0.06 PHENIX (?sNN130 GeV) dNch/d?
?1.20?0.05 dET/d? ?1.18?0.05 PHENIX (?sNN200
GeV) dNch/d? ?1.19?0.05 dET/d? ?1.19?0.05
PHENIX preliminary
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Comparison to theory
200 GeV
130 GeV
HIJING X.N.Wang and M.Gyulassy, PRL 86, 3498
(2001) Mini-jet S.Li and X.N.Wang
Phys.Lett.B52785-91 (2002) EKRT K.J.Eskola et
al, Nucl Phys. B570, 379 and Phys.Lett. B 497,
39 (2001) KLN D.Kharzeev and M. Nardi, Phys.Lett.
B503, 121 (2001) D.Kharzeev and E.Levin,
Phys.Lett. B523, 79 (2001)
PHENIX preliminary
PHENIX preliminary
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Energy Dependence

• Assumptions
• in Lab in C.M.
• Energy density (Bjorken)
• 2 most central at ?sNN200 GeV
• ? ? 5.5 GeV/fm3
• From AGS, SPS to RHIC
• Transverse energy and charged particle
  multiplicity densities per participant consistent
  with logarithmic behaviour

PHENIX preliminary
PHENIX preliminary
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Summary

• Centrality dependence of particle dNch /dh and
  dET /dh have been measured at ÖsNN 130 GeV and
  200 GeV in AuAu collisions
• ltdET gt/ltdNchgt is near independent of centrality
  and of ÖsNN
• The ratio R(200/130) consistent with constant
  scaling vs Np
• Both dNch /dh and dEt /dh per participant
  increase with centrality
• the increase is stronger than at SPS
• data well described by KLN and Mini-jet model
  predictions