high-p t identified particle spectra in p+p collisions at 200 gev
DESCRIPTION
High-p T identified particle spectra in p+p collisions at 200 GeV. Outline: Motivation Analysis Preliminary results Future work & Summary. Yichun Xu (for the STAR collaboration). Motivation. - PowerPoint PPT PresentationTRANSCRIPT
High-pT identified particle spectra in p+p collisions at 200 GeV
Yichun Xu (for the STAR collaboration) Outline:
Motivation
Analysis
Preliminary results
Future work & Summary
Yichun Xu(USTC/BNL) 8/17/2008, Hot Quark, Colorado 2
MotivationExtend the identified hadron spectra study to higher pT range and test the applicability of pQCD in p+p collisions.
Baseline for study of color charge effect of parton energy loss in heavy ion collisions.Proton spectra in STAR is limited to 7GeV/c with current statistics from minimum bias p+p collisions.[1]
In Au+Au, it can be extended to 12GeV/c now. [2]
[1] Phys. Lett. B 637 (2006) 161 [2] Phys. Rev. Lett. 97 (2006) 152301
Yichun Xu(USTC/BNL) 8/17/2008, Hot Quark, Colorado 3
Experiment and Data set
Time Projection Chamber (TPC) Electro-Magnetic Calorimeter (EMC) Shower Maximum Detector (SMD)
Data set: EMC Triggers in run5 pp @ 200GeV Jet Patch trigger: ETtot>7.8 GeV
TPC Cuts:
pT>0.2 GeV/c, || < 0.5, Azimuthal
angle |∆φ|>π/2
∆φ
∆φ trigger
Yichun Xu(USTC/BNL) 8/17/2008, Hot Quark, Colorado 4
dE/dx re-calibration, why?
)/)/log(( BdxdEn XX
Where Bπ is the expected mean dE/dx of pion from Bichsel function of ionization energy loss in TPC.
STAR preliminary
STAR preliminary 4.0<pT<4.5GeV/c
w/ EMC cut
Yichun Xu(USTC/BNL) 8/17/2008, Hot Quark, Colorado 5
Raw Yield
Peak positions of charged particles are fixed by parameters from re-calibration.
STAR preliminary
= 0.87
STAR preliminary
Yichun Xu(USTC/BNL) 8/17/2008, Hot Quark, Colorado 6
Results (1)—pion spectra
PYTHIA (V6.205, MSEL=1) and GEANT are used to get trigger enhancement to correct spectra in triggered events.
STAR preliminarySTAR preliminary
Yichun Xu(USTC/BNL) 8/17/2008, Hot Quark, Colorado 7
Results (2)—proton spectra
AKK 2008 [1] is constrained by BRAHMS pbar/p ratio [2] (y=2.95, pT<5 GeV/c).
[1] arXiv:0803.2768 , [2] Phys. Rev. Lett. 98, 252001 (2007)
STAR preliminary
Simon, private communication
Our data will provide the best constraint on Fragmentation Functi
on!
Yichun Xu(USTC/BNL) 8/17/2008, Hot Quark, Colorado 8
Results(3)--Comparison with NLO
DSS, KKP and AKK2008 predict pionspectra very well, but PYTHIA under-predict pion production.
Only DSS can describe proton production.
STAR preliminary STAR preliminary
Yichun Xu(USTC/BNL) 8/17/2008, Hot Quark, Colorado 9
Results(4)--Ratios
PYTHIA describe all ratios very well, DSS over-predicts anti-proton, and AKK2008 over-predicts proton and under-predicts anti-proton.
Yichun Xu(USTC/BNL) 8/17/2008, Hot Quark, Colorado 10
Results(5)—compare with d+A, A+A
-/+ : isospin conservation
Pbar/p: are similar in three systems.
p(+-)/at intermediate pT: are consistent with coalescence prediction.
p (+-)/ at high pT: indicate more quark jet contribution to proton in p+p than in A+A.
Yichun Xu(USTC/BNL) 8/17/2008, Hot Quark, Colorado 11
Future work: EMC as hadron trigger detector
Given pT=5 GeV/c, ~5.6M HT1 triggered events are equivalent to
L(0.64 pb-1)*(30mb) * effTrg(3%)/effTrk(90%) ~ 0.6B events.
STAR preliminary
A factor of 100 enhancementSTAR preliminary
EMC module
Yichun Xu(USTC/BNL) 8/17/2008, Hot Quark, Colorado 12
Reconstruct KS with triggered pion
It can reach 10 GeV/c while it only arrive 5 GeV/c in minimum bias events .
Constrain K/ ratio and check hadron yields.
Good method to reconstruct resonance at high pT.
STAR preliminary
KS->
Yichun Xu(USTC/BNL) 8/17/2008, Hot Quark, Colorado 13
Summary
Extend pion and proton spectra to pT ~15 GeV/c.
-/+, pbar/p & p(pbar)/+(-) ratios are consistent with results from minimum-bias events within error.
DSS, KKP and AKK2008 describe pion yields very well, but only DSS predictions are consistent with proton production.
-/+ and pbar/p ratios are consistent with PYTHIA, which under-predicts the individual yields of + and -.
Decrease of pbar/p ratio indicates a significant quark jet contribution to baryon.
Yichun Xu(USTC/BNL) 8/17/2008, Hot Quark, Colorado 14
Thanks!
Yichun Xu(USTC/BNL) 8/17/2008, Hot Quark, Colorado 15
Backup
Yichun Xu(USTC/BNL) 8/17/2008, Hot Quark, Colorado 16
V0 (KS&) -- p&dE/dx
STAR preliminarySTAR preliminary
Ms(0.485,0.505)
M(1.112,1.118)
STAR preliminary
Yichun Xu(USTC/BNL) 8/17/2008, Hot Quark, Colorado 17
Re-calibration
STAR preliminary
2)(
xC
BAxf
Fit
function:No obvious color charge effect of parton energy loss in heavy ion collision.
Yichun Xu(USTC/BNL) 8/17/2008, Hot Quark, Colorado 18
NLO differences
KKP: e+e- data, no charge difference AKK: derived from KKP, including p,n,KS, etc. AKK2008: including STAR data, and constrained b
y including BRAHMS pbar/p ratio. DSS: e+e- data, including STAR data points.
EMC & SMD cuts: 0.3<p/E<1.5,n>=2,n>=2, |zdist|<2, |dist|<0.01
Yichun Xu(USTC/BNL) 8/17/2008, Hot Quark, Colorado 19
STAR preliminary
STAR preliminary