Inclusive Jet and Dijet Production in Polarized Proton-Proton Collisions at 200 GeV at RHIC

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1 Inclusive Jet and Dijet Production in Polarized Proton-Proton Collisions at 2 GeV at RHIC Measurement of Inclusive Jet Cross Section MIT Tai Sakuma for the collaboration Introduction and Jet measurement - comparison Inclusive Jet Cross Section Dijet Measurement Summary

2 Introduction Jet cross sections in hadron collisions are fundamental test of QCD factorization and pqcd. σ = i,j dx dx 2 f i (x,q 2 )f j (x 2,Q 2 )ˆσ(cos θ ) Jet cross sections provide us with a theoretical interpretation of the spin asymmetry in polarized proton collisions, A LL = σ++ σ + σ ++ + σ + = i,j i,j dx dx dx 2 f i (x,q 2 ) f j (x 2,Q 2 )â LLˆσ(cos θ ) dx 2 f i (x,q 2 )f j (x 2,Q 2 )ˆσ(cos θ ) allowing us to extract polarized gluon distribution from A LL. g(x, Q 2 )=g + (x, Q 2 ) g (x, Q 2 ) Polarized gluon distribution can address the spin puzzle. G = g(x)dx 2 = 2 Σ+ G + L q + L g

3 Introduction In DIS, parton-level kinematics can be always determined x = Q2 2Mν In pp, not unless two outgoing partons are measured x = p T s ( e η 3 + e η 4 ) x 2 = p T s (e η 3 +e η 4 ) can be estimated from dijets

4 Introduction Jets at Three Levels Theory (pqcd) Parton Level " " () Hadron Level # # $# " $ $ " " $ " # K s $ " " $ # $ $ " Detector Level and theory are corrected to hadron level using simulation and then compared.

5 RHIC as a polarized proton-proton collider Run s [GeV] Ldt[pb ] a Polarization b Run % Run % Run % Run % Run % % Run % Run % % a Delivered luminosity at b Average polarization PHOBOS PHENIX 8 2 BRAHMS 2 Siberian Snakes 4 RHIC 6 Yellow Blue OPPIS AGS Booster Partial Snake AtR LINAC AGS 2m Tai Sakuma

6 Detector =- = BE = a full-azimuth calorimeter Blue BBC Yellow a full-azimuth tracking device TPC West East well suited for jet measurement Tai Sakuma

7 Parameters of the Analysis 5.4 pb -, pp 2 GeV, RHIC Run-6 BJP Trigger (8.3 GeV < E T in Δη x Δϕ=x) JP 7 JP JP 6 JP JP 8 JP 2 JP JP 9 Phase Space - Inclusive Jets - Dijets.8 <η<.8 max(p T ) >. GeV min(p T ) > 7. GeV.8 <η<.8 η 3 η 4 <. ϕ > 2. Jet Patches JP 5 JP JP 4 JP 3 Jet Definition - Charged tracks in TPC z 29 Tai Sakuma - Energy deposits in BE towers - Mid-point cone (R=.7) Dijet Definition - Two-leading p T jets Cross Sections - Inclusive Jets d 2 σ 2πdp T dη = Ldt - Dijets d 3 σ = dm jj dη 3 dη 4 Ldt 2π p T η C J M jj η 3 η 4 C J

8 - Comparison of Inclusive Jets Correction factors are determined with samples which well reproduce data < pt < GeV < pt < GeV < pt < GeV ( - ) / - Run p T [GeV] Jet Profile (r) < pt < 7.3 GeV r/r from Jet Axis 7.3 < pt < 26.9 GeV : Pythia Geant < pt < GeV 2.3 < pt < 26.9 GeV 7.3 < pt < 2.3 GeV.44 < pt < 7.3 GeV pt [GeV].8 <η< Neutral Energy Ratio R T

9 - NLO pqcd comparison of Inclusive Jet Cross Section d 2 / 2dp T d [pb/gev] d 2 2dp T d Inclusive Jet Cross Section 2 GeV Cone Radius = < <.8 Ldt = 5.39 pb ( - Theory) / Theory Run-6 -theory Comparison of Inclusive Jet Cross Section 2 GeV Cone Radius = < <.8 Systematic Uncertainty Theoretical Uncertainty Ldt = 5.39 pb p T [GeV] Run-6 Systematic Uncertainty. Theory NLO pqcd + CTEQ6M..5 Pileup Timebin Luminosity JES..5 Had. and UE. Corrections p T [GeV] Systematic Uncertainty p T [GeV] are well described by NLO pqcd plus hadronization and underlying event corrections.

10 - Comparison of Dijets are well described by 5 4 Dijet Yield < M < 36 GeV 36 < M < 53.6 GeV 53.6 < M < 84.5 GeV max(p T ) >. GeV min(p T ) > 7. GeV.8 <η<.8 η 3 η 4 <. ϕ > < M < 68.5 GeV Dijet Yield 3 2 Run-6 ( - ) / M jj [GeV] < M < 36 GeV 36 < M < 53.6 GeV 53.6 < M < 84.5 GeV 84.5 < M < 68.5 GeV ( - ) / - 5 Dijet Yield ( - ) / M jj [GeV] : Pythia Geant

11 Summary Inclusive jet cross section in GeV in the mid-rapidity region is measured with 5.4 pb - of RHIC Run-6 data collected with the detector. The results are in agreement with NLO pqcd. The results are in consistent with our previous results with smaller acceptance and cone size. The results lend confidence that the inclusive jet A LL can be interpreted in the framework of the QCD factorization with NLO pqcd. The dijet production is well described by. The dijet cross section will facilitate an interpretation of dijet A LL.