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Event structure and double helicity asymmetry in jet production from polarized p+ p collisions at sqrt [s]= 200 GeV

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Please use this identifier to cite or link to this item: http://hdl.handle.net/1928/20564

Event structure and double helicity asymmetry in jet production from polarized p+ p collisions at sqrt [s]= 200 GeV

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Title: Event structure and double helicity asymmetry in jet production from polarized p+ p collisions at sqrt [s]= 200 GeV
Author: Fields, Douglas E.; PHENIX Collaboration; Barnes, P. D.; Boissevain, J. G.; Brooks, M. L.; Butsyk, S.; Constantin, P.; Kunde, G. J.; Lee, D. M.; Leitch, M. J.; Liu, M. X.; McGaughey, P. L.; Norman, B. E.; Palounek, A. P. T.; Purwar, A. K.; Sondheim, W. E.; Van Hecke, H.W.; Bassalleck, B.; Haegemann, C.; Hobbs, R.; Malik, M. D.; Rak, J.; Thomas, T. L.; Younus, I.; Al-Bataineh, H.; Armendariz, R.; Kyle, G. S.; Papavassiliou, V.; Pate, S. F.; Stepanov, M.; Wang, X. R.
Abstract: We report on the event structure and double helicity asymmetry (ALL) of jet production in longitudinally polarized p+p collisions at √s=200  GeV. Photons and charged particles were measured by the PHENIX experiment at midrapidity |η|<0.35 with the requirement of a high-momentum (>2  GeV/c) photon in the event. Event structure, such as multiplicity, pT density and thrust in the PHENIX acceptance, were measured and compared with the results from the pythia event generator and the geant detector simulation. The shape of jets and the underlying event were well reproduced at this collision energy. For the measurement of jet ALL, photons and charged particles were clustered with a seed-cone algorithm to obtain the cluster pT sum (pTreco). The effect of detector response and the underlying events on pTreco was evaluated with the simulation. The production rate of reconstructed jets is satisfactorily reproduced with the next-to-leading-order and perturbative quantum chromodynamics jet production cross section. For 4<pTreco<12  GeV/c with an average beam polarization of ⟨P⟩=49% we measured ALL=-0.0014±0.0037stat at the lowest pTreco bin (4–5  GeV/c) and -0.0181±0.0282stat at the highest pTreco bin (10–12  GeV/c) with a beam polarization scale error of 9.4% and a pT scale error of 10%. Jets in the measured pTreco range arise primarily from hard-scattered gluons with momentum fraction 0.02<x<0.3 according to pythia. The measured ALL is compared with predictions that assume various ΔG(x) distributions based on the Gluck-Reya-Stratmann-Vogelsang parameterization. The present result imposes the limit -1.1<∫0.020.3dxΔG(x,μ2=1  GeV2)<0.4 at 95% confidence level or ∫0.020.3dxΔG(x,μ2=1  GeV2)<0.5 at 99% confidence level.
Date: 2011-06-21
Publisher: American Physical Society
Citation: Physical Review D, 84(1): 1-18
Description: http://prd.aps.org/pdf/PRD/v84/i1/e012006
URI: http://hdl.handle.net/1928/20564


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