Upload
mara-summerhill
View
214
Download
0
Tags:
Embed Size (px)
Citation preview
Pawan Kumar Netrakanti QGP-MEET 2006, VECC, February 2006
1
Identified hadron spectra at large transverse momentum in p+p and d+Au collisions at
sNN=200 GeV
Pawan Kumar Netrakanti,VECC, Kolkata (For STAR Collaboration)
Pawan Kumar Netrakanti QGP-MEET 2006, VECC, February 2006
2
Motivation Method of analysis Results from p+p collisions Results from d+Au collisions Summary
Outline
STAR preliminarySTAR preliminary
STAR preliminarySTAR preliminary
Pawan Kumar Netrakanti QGP-MEET 2006, VECC, February 2006
3
Motivation
Understanding Nuclear effects in d+Au collisions
Test predictions (certain aspects) of pQCD
High pT PID in TPC
Pawan Kumar Netrakanti QGP-MEET 2006, VECC, February 2006
4
Method of analysis
Intrinsic timing resolution: 85 ps Coverage : -1.0 < < 0.0 and in low pT particle identification ( < 2.5 GeV/c) in this study
Hadron identification: STAR Collaboration, nucl-ex/0309012
High pT : Extend particle identification in TPC by exploiting the relativistic rise in ionization energy loss.
Log10(p)
Log
10(d
E/d
x)
Momentum: GeV/cdE/dx of K,p) separation: 2
10~
3 p
High pT Time Projection Chamber (TPC)
Low pT Time of Flight (TOF)
Coverage: |andsymmetric
Pawan Kumar Netrakanti QGP-MEET 2006, VECC, February 2006
5
Transverse Momentum Spectra
STAR preliminarySTAR preliminary
Power-law : ( A/(1 + pT/p0)n)
Levy : (B/(1+(mT-m0)/nT)n)Power-law function ~ pQCD inspiredLevy ~ exponential + power-law
Power law type behavior for p+p and d+Au collisions at high pT
Pawan Kumar Netrakanti QGP-MEET 2006, VECC, February 2006
6
Comparison to NLO pQCD
NLO pQCD with AKK FF relatively better than KKP for the p+pbar data
AKK differ from KKP, in the way the light flavor FF are obtained
NLO pQCD with Kretzer FF inconsistent with data
NLO pQCD with KKP FF inconsistent with the p+pbar data
Kretzer differ from KKP, in the gluon to fragmentation
Pawan Kumar Netrakanti QGP-MEET 2006, VECC, February 2006
7
p+p collisions and phenomenological model
Phenomenological EPOS Model are consistent with pion data, even at low pT.
Phenomenological EPOS Model are consistent with p + pbar data, even at low pT.
Interesting to observe that two different models (pQCD and EPOS) do a reasonable job in p+p collisionsK. Werner, F. Liu and T. Pierog, hep-
ph/0506232
Pawan Kumar Netrakanti QGP-MEET 2006, VECC, February 2006
8
Scaling in particle production
e+ and e- does not have a parton distribution function.There will be a (sNN )2 multiplied to cross-section in e+e- collisions. For p+p collisions n ~ 6.5 for , p
(pbar)
Pawan Kumar Netrakanti QGP-MEET 2006, VECC, February 2006
9
d+Au collisions and models
•NLO pQCD calculations with KKP and AKK FF and EPOS are consistent with pion data at high pT (> 4 GeV/c)•pQCD calculations with Kretzer FF under predicts pion data• NLO pQCD calculations with only AKK fragmentation function consistent with the p+pbar data
Parton distribution functions : L. Frankfurt, et al., Phys. Rev. D 71 (2005) 054001
D. De Florian and R. Sassot, PRD 69 (2004) 074028
STAR Preliminary
Pawan Kumar Netrakanti QGP-MEET 2006, VECC, February 2006
10
Nuclear Modification Factor : d+Au collisions
RdAu for > 1, Cronin effect Absence of high pT suppression in particle production RdAu (p + pbar) > RdAu () Similar dependence has been observed at lower energies. Phys. Rev D 19 (1979) 764
Qualitative agreement with recombination model for dAu collisions. Phys.Rev.Lett.93 (2004) 082302
STAR preliminarySTAR preliminary
STAR preliminarySTAR preliminary
evt 2AB AB T
AB 2AB pp T
1 N d N /dydpR
T d /dydp
Phys. Rev. Lett. 91 (2003) 072304
Pawan Kumar Netrakanti QGP-MEET 2006, VECC, February 2006
11
Particle Ratios – p+p collisions
-/+ ~ 1 and pbar/p ~ 0.8 PYTHIA predicts a more prominent pT dependence
p/+ and pbar/ - increases with pT ~ 2 GeV/c and then decreases to ~ 0.2 p/+ agrees with lower energy results. pbar/ - shows a distinct energy dependence
Pawan Kumar Netrakanti QGP-MEET 2006, VECC, February 2006
12
Particle Ratios – d+Au collisions
STAR preliminarySTAR preliminary -/+ ~ 1- independent of pT
pbar/p decreases with pT
p/+ and pbar/- increases with pT up to 2 GeV/c and then decreases.
Pawan Kumar Netrakanti QGP-MEET 2006, VECC, February 2006
13
Highlight and Summary
NLO pQCD describes the p+pbar spectrum for the first time in p+p collisions
These results show the importance of the significant improvement of FF for baryons from the light-flavor separated measurements in e+e- collisions (OPAL)
The observed xT scaling of ,p(pbar) at high pT also show dominance of hard processes related to PDF and FF Provide solid reference for effects of jet quenching and recombination in Nucleus-Nucleus collisions
Details of these results can be found at: arXive: nucl-ex/0601033
Pawan Kumar Netrakanti QGP-MEET 2006, VECC, February 2006
14
The STARSTAR CollaborationU.S. Labs:
Argonne, Lawrence Berkeley, and Brookhaven National Labs
U.S. Universities: UC Berkeley, UC Davis, UCLA, Caltech, Carnegie Mellon, Creighton, Indiana, Kent State, MIT, MSU, CCNY, Ohio State, Penn State, Purdue, Rice, Texas A&M, UT Austin, Washington, Wayne State, Valparaiso, Yale
Brazil: Universidade de Sao Paolo
China: IHEP - Beijing, IPP - Wuhan, USTC,Tsinghua, SINAP, IMP Lanzhou
Croatia: Zagreb University
Czech Republic: Nuclear Physics Institute
England:University of Birmingham
France: Institut de Recherches Subatomiques Strasbourg, SUBATECH - Nantes
Germany: Max Planck Institute – Munich University of Frankfurt
India:Bhubaneswar, Jammu, IIT-Mumbai, Panjab, Rajasthan, VECC, Kolkata
Netherlands:NIKHEF/Utrecht
Poland:Warsaw University of Technology
Russia: MEPHI – Moscow, LPP/LHE JINR – Dubna, IHEP – Protvino
South Korea:Pusan National University
Switzerland:University of Bern
STARSTAR
Pawan Kumar Netrakanti QGP-MEET 2006, VECC, February 2006
15
Scaling of particle production
mT scaling observed for1 < mT < 2 GeV/c2
STAR preliminarySTAR preliminary
At high pT : no scalingMass effect
Or baryon-meson effect