Download presentation
Presentation is loading. Please wait.
1
Jets at RHIC Jiangyong Jia jjia@skipper.physics.sunysb.edu
2
Outline n Jet and it’s importance in RHIC u Jets and hard scattering u soft vs hard u pQCD approach F pp F pA F AA n Angular correlation u some examples u Phenix experiment u my angular correlation study u outlook n Summary
3
Relativistic Heavy-Ion Collider (RHIC) n Goal u Searching for the quark gluon plasma(QGP) u exploring the physics of this new state of matter. n Jet quenching as probe Au Au at
4
Jet quenching: a QGP signature n What is a Jet ? n QCD energy loss in deconfined dense matter n Theory prediction dE/dx = 2-4GeV/fm n QGP suppresses high pt particles and angular correlations b a c d
5
Ref, K.Geiger
6
Jet and hard scattering at n Jet production rate (K.J.Eskola,hep-ph/9610365 ) n Hard scattering contribution to particle production is important( )
7
d /p T dp T string model hydrodynamic model pQCD (Hijing,PCM) pTpT soft Semi-hard hard 1GeV5GeV soft process vs hard process Jet
8
Soft/hard boundary? n At SPS ( ) u Hydrodynamic models. u pQCD(X.N.Wang, hep-ph/9804357 ) u at SPS : both works. u Small jet cross-section, measure only to n At RHIC ( ) u increase, larger jet cross-section,measure to high pt ( ). u Angular correlation
9
Hydrodynamic Model for SPS Plot created by Jane Burward Hoy
10
pQCD calculation X.N.Wang,nucl-th/9812021
11
Jet production (X.N.Wang,nucl-th/9812021) n pQCD approach Schematic representation of a high-pt reaction factorized into parton distribution function (f), parton fragmetation function D and a hard-scattering subprocess parton-parton collision convolution Cross-section n Cross-section
12
pp--Initial Kt n Need to take into account intrinsic pt of partons u Uncertainty principle u high order pQCD process(initial state radiation,etc) n modify parton distribution function u where
13
pA-- Modification of hard scattering n Assume only one hard parton- parton collision. n Enhancement of high Pt spectra (Cronin effect ) u decrease with 1/p t 2 and A (b) is number of scattering assume hard sphere distribution 2 is the soft Kt kick, it has following form n Modification of nuclear structure function (Shadowing) u assume parton distribution:
14
Cronin and Shadowing in pA R pAu p + Au
15
AA--Jet quenching n If we have QGP, multiple interactions of parton with the medium lead to loss of energy. n Time scale ( h 1/p 0 0.1fm/c, p 0 2GeV/c, s 1/ QCD 1 fm/c) High pt parton collisions happen in the earliest stage of collision. Then they suffer energy loss in the medium. n Hijing Assume (model dependent): u constant energy loss u incoherent multiple scattering.
16
R AA (PT)
17
Angular correlation At RHIC n Back-to-Back correlation: u QGP F (Di-)Jets suppression F enhanced acoplanarity. n Study the centrality (impact parameter) dependence u From peripheral to central n Some examples
18
CCOR At ISR pp forwardbackward Ref, M.J.Tannenbaum
19
X.N.Wang,Phys.Rep.280,287(1997).
20
Phenix Detector n Good Charged particle tracking u high pt resolution, u high interaction rate, L=10 26~27 cm 2 /s (read out 50Hz ) n Phenix detector acceptance u default acceptance: F Pt 0.2 GeV/c; F 70 < <110 or | |<0.35 F -33.75 < <56.25 , 123.75 < <213.75 u 1/2*sin( /2) = 17 of 4 u acceptance in azimuthal leads to an intrinsic jet shape Phenix acceptance : http://skipper.physics.sunysb.edu:80/talks/jjia
21
DC (degree) (degree) -90 270 0180 0.35 110 -0.35 70 90 Detector LayoutDetector Acceptance EMCal TEC RICH
23
Studies of pp collisions at n Pythia Generator u 100000 pp events at u min jet pt = 20GeV/c. n Analysis scheme (as CCOR): u study distributions: F back to back correlation of jets ( w/o acceptance) F modification with a HIC background (RQMD) one Pythia event(two jets) mixed with one RQMD event F effect of Phenix acceptance.
24
Leading Pt>2.0
25
1<Pt<2 4<Pt<53<Pt<4 2<Pt<3
30
Outlook n RQMD (Hadrons + Strings) use other models as background (Hijing, Strings + Minijets) n Determine methods to correct for and acceptance of Phenix(limited acceptance) u event by event acceptance correction u investigate the fiducial region( , ,pt) n Study angular correlation function: n Rate estimate(1/2000) n when we have the data…. u Study angular correlation as a function of centrality. Fiducial region Detector acceptance
31
Summary n Large pt partons or Jets are good probes of the dense matter in ultra- relativistic heavy-ion collisions. n In RHIC, can use pQCD based models to calculate high pt spectra. u Need to combine soft and hard processes together. n Study back to back jets angular correlation u if QGP is generated, angular correlation will be affected by jet quenching u Phenix detector have limited acceptance, we can: F increase pt and use the fiducial region F learn how to correct for and acceptance. n We will further our study on jet angular correlation and look for jet quenching as a probe of QGP formation at RHIC.
32
References n K.J.Eskola,hep-ph/9601365. u Give the parton production rate. n Also K.J.Eskola,K.Kajantie,and J.Lindfors Nucl.Phys.B323,37(1989) u it calculate the parton production rate, saying: F for RHIC, U + U, have 290 partons Pt>2GeV, and 75 partons Pt>3GeV. F For hard Et,SPS 5%, RHIC 50%, Tevatron 80%. n X.N.Wang,nucl-th/9812021. u Base of this talk. n X.N.Wang,Phys.Rep.280,287(1997). u Base of this talk. n J.F.Owens,Rev.Mod.Phys. 59, 465 (1987). u Gives the jet cross section formula. n X.N.Wang,hep-ph/9804357. u Calculate the jet quenching under simple assumption. n M.Arneodo,Phys.Rep.240,301(1994) u shadowing effect. n K.Geiger. Ultra-Relativistic nuclear collisions in a QCD based space-time description: the parton cascade model u a very good article delving into the history of AA collision, comparing with Hijing, and have a lot of interesting graph. n Nucl.Phys.B480 406. u Having UA1 Jet cross section measurement
35
PP pA AA Single Inclusive cross section
36
1<Pt<2 4<Pt<5 3<Pt<4 2<Pt<3
Similar presentations
© 2024 SlidePlayer.com Inc.
All rights reserved.