particle production in au+au collisions at 9.2gev
DESCRIPTION
Particle Production in Au+Au Collisions at 9.2GeV. http://drupal.star.bnl.gov/STAR/starnotes/public/sn0493. Jiayun Chen (for Collaboration) Institute of Particle Physics, CCNU, Wuhan, 430079, P.R.China Brookhaven National Lab, Upton, NY,11973, USA. Outline. Motivation - PowerPoint PPT PresentationTRANSCRIPT
Particle Production in Au+Au
Collisions at 9.2GeV
Jiayun Chen
(for Collaboration)
Institute of Particle Physics, CCNU, Wuhan, 430079, P.R.China
Brookhaven National Lab, Upton, NY,11973, USA
http://drupal.star.bnl.gov/STAR/starnotes/public/sn0493
Jiayun Chen for STAR -CPOD2009 2
Outline
• Motivation
• STAR preliminary 9.2 GeV results Particle identification in TPC Charged multiplicity Azimuthal anisotropy PID spectra and ratios : energy, centrality Charged pion interferometry
• Summary and outlook
Lessons from 200GeV
• Strong high pT suppression in hadron production.
• Number of Constituent Quark scaling in v2 measurements
Indicate the existence of sQGP.
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Phys. Rev. Lett. 91, 072304 (2003)
Phys. Rev. Lett. 92, 052302 (2004)Phys. Rev. C 72, 014904 (2005)Phys. Rev. Lett. 95, 122301(2005)Phys. Rev. Lett. 92, 112301(2004)
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MotivationQCD theory predicts:• Low B & High T :Cross-over• High B & Low T:1st order transition• Mid B & Mid T :Critical Point
Plan : Access to phase diagram• T and B vary with √sNN
Signatures Locating the phase boundaries Locating the critical point
Aim of this talk is to discuss the results from successful data taking in STAR with Au+Au collisions at 9.2 GeV. Demonstrate our readiness for the future Beam Energy Scan program at RHIC.
NSAC 2007 Long-range Plan
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STAR Detector
2.5<|η|<4.0
|η|<1.5
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Collisions @ 9.2 GeV STAR TPC display: Au+Au at 9.2GeV
1. ~ 3000 good events collected at ~ 0.6 Hz in year 2008
2. Data taking period lasted for < 5 hr.3. In the future, ToF will further
enhance the PID
Non-central Central
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Collider Acceptance
Fix
ed
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Charged Multiplicity Collision Centrality Selection
Track selection for various analysis
•With more events STAR will map out centrality (system-size) in detail.•Changes in fluctuations with system-size can indicate the presence of a 1st order phase transition.
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1cos , tan ( )ynx
pv n
p
This is believed to be due to pressure gradients in the dense medium which lead to collective motion.Directed flow (v1) at forward rapidities describes the “side-splash”, the foremost early collective motion of the system;Elliptic flow (v2) demonstrated the development of collectivityProvide insights into the EOS.
Coordinate-SpaceAnisotropy
Momentum-SpaceAnisotropy
interactions
pressure gradient pressure gradient collective flow collective flow
Azimuthal Anisotropy
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Directed Flow v1
two methods to analyze the data‘standard’ event plane method - v1{FTPC,EP1} - v1{BBC,EP1}
mixed event plane method -v1{EP1,EP2}
1 2
1 1 21 2
1 1 2 2
cos 2{ , }
cos( 2 ) Re ( )
FTPC TPC
FTPC FTPC TPC TPCv EP EP
s
1 1 1 1{ } cos( ) / Re ( )v EP s
Results from two methods are consistent.
STAR PreliminarySTAR Preliminary
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Directed Flow v1
• At mid-rapidity, all the results have comparable values. At forward rapidity, the trend of v1 from low energy is different from high energies. This is due to early longitudinal collision dynamics.
• V1 values lie on a common trend. STAR : PRL 92 (2004) 062301 PRL101 ( 2008 ) 252301NA49: PRC68(2003)034903
STAR Preliminary
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Elliptic Flow
• STAR and NA49 results seem to be consistent.• STAR 9.2GeV v2 nicely fits into the observed trends.
NA49 : PRC 68 (2003) 034903AGS : PLB 474 (2000) 27STAR : PRC 77 (2008) 054901 : PRC 75 (2007) 054906, PRC 72 (2005) 014904PHOBOS : PRC 72 (2005) 051901 : PRL 98 (2007) 242302 PHENIX : PRL 98 (2007) 162301
STAR Preliminary STAR Preliminary
Lokesh Kumar QM2009, SQM2008
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pT Spectra
The slope of the identified hadron spectra follow the order <k<p
These spectra can be further characterized by looking at the dN/dy and <pT> or <mT>
We measure within our pT acceptance~ 82 % of total produced~ 47 % of total K produced~ 75 % of total p producedSTAR Preliminary
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Yield &<mT> vs. Energy
Yield and <mT> beam energy dependence are consistent with the published data
Assuming a thermo-dynamic system : T ~ <mT> - m
entropy ~ dN/dy log(√sNN)
NA49 : PRC 66 (2002) 054902, PRC 77 (2008) 024903 PRC 73 (2006) 044910STAR : PRC 79 (2009) 034909, arXiv: 0903.4702E802(AGS) : PRC 58 (1998) 3523, PRC 60 (1999) 044904 E877(AGS) : PRC 62 (2000) 024901 E895(AGS) : PRC 68 (2003) 054903
STAR Preliminary
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Particle Ratios vs. centrality K-/K+ & K-/- are lower in 9.2
GeV compared to that in 200 and 62.4 GeV;
K+/ + in 9.2 GeV is comparable to that in 200 and 62.4 GeV
--K+ production is dominated by associated production in low energy.
p/ in 9.2 GeV is larger compared to 200 and 62.4 GeV
-- shows large baryon stopping at low energy;
Ratios seem to be almost independent of collision centrality for all energies studied.
STAR : PRC 79 (2009) 034909
p
K K
STAR Preliminary
STAR Preliminary
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Particle Ratio vs. Energy
NA49 : PRC 66 (2002) 054902, PRC 77 (2008) 024903, PRC 73 (2006) 044910
E802(AGS) : PRC 58 (1998) 3523, PRC 60 (1999) 044904, PRC 62 (2000) 024901,
PRC 68 (2003) 054903
p/p
K/K+
K/_
STAR Preliminary
STAR : PRC 79 (2009) 034909, arXiv: 0903.4702
STAR preliminary
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Pion Interferometry
Source parameters :
Centrality : 0 - 60%Error bars for Au+Au 9.2 GeV are statistical Systematic errors expected to be < 10 % for all radii KT=[0.15,0.25](GeV/c)
-
All are consistent with the previously observed trends
STAR : PRC 71 (2005) 044906, PRL 87 (2001) 082301PHENIX : PRL 88 (2002) 192302, PRL 93(2004) 152302
E802 : PRC 66 (2002) 054906CERES : NPA 714 (2003) 124 E895 :PRL 84 (2000 ) 2798PHOBOS : PRC 73 (2006) 031901
NA44 : PRC 58 (1998) 1656 E866 : NPA 661 (1999) 439NA49 : PRC 77 (2008) 064908WA97 : JPG 27 (2001) 2325
Rout(fm) Rside(fm)
5.05±0.96 3.52±0.56
Rlong(fm)
3.25±0.86 0.355±0.083
D. Das for STAR Collaboration WWND 09
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Summary
Azimuthal Anisotropy (v1 and v2) results are similar to those obtained at SPS from collisions at similar energies
Identified particle spectra obtained from Au+Au collisions at 9.2 GeV. Centrality and beam energy dependence of the hadron yields and ratios studied.
In central collisions anti-proton to proton ratio ~ 0.01 shows significant baryon stopping in these collisions
In central collisions K-/K+ ~ 0.4 shows associated production for K+
p/ ratio is higher and K-/- is lower at 9.2 GeV compared to 200 GeV at all collision centralities studied
Pion interferometry results follow the established beam energy trends
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STAR BES Program
Key measurements:
(1) PID hadron spectra, ratios, v2 … (2) Fluctuations: - Net-p Kurtosis - K/ - <pT>, <N> …
See Daniel Cebra’s talk ” STAR plans for the RHIC low energy run”
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• The results from the lowest beam energy collisions at RHIC demonstrate STAR experiment’s readiness to collect high quality data for the proposed Critical Point Search Program.
• Large and uniform acceptance for all beam energies in a collider set up, excellent particle identification (TPC+TOF) and higher statistics will lead to significant advance in the Critical Point search: Differential analyses of pT and number correlations for identified particles
-- vs and to identify the source and nature of observed non-statistical fluctuations System-size dependence of fluctuations (1st order phase transition?) Charge separation of K/ and P/ fluctuations Higher moments of net-charge and net-proton distributions Azimuthal HBT
Critical Point Search Program will allow us to explore the QCD phase diagram.
Outlook