Event structure and double helicity asymmetry in jet production from polarized p+p collisions at (sq rt) s = 200 GeV

Journal Article · Mon Aug 01 04:00:00 EDT 2011 · Physical Review. D, Particles, Fields, Gravitation and Cosmology

DOI:https://doi.org/10.1103/PhysRevD.84.012006· OSTI ID:1034034

Adare, A

We report on the event structure and double helicity asymmetry (A{sub LL}) of jet production in longitudinally polarized p+p collisions at {radical}s = 200 GeV. Photons and charged particles were measured by the PHENIX experiment at midrapidity |{eta}| < 0.35 with the requirement of a high-momentum (> 2 GeV/c) photon in the event. Event structure, such as multiplicity, p{sub T} 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 p{sub T} sum (p{sub T}{sup reco}). The effect of detector response and the underlying events on p{sub T}{sup reco} 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 < p{sub T}{sup reco} < 12 GeV/c with an average beam polarization of <P> = 49% we measured A{sub LL} = -0.0014 {+-} 0.0037{sup stat} at the lowest p{sub T}{sup reco} bin (4-5 GeV/c) and -0.0181 {+-} 0.0282{sup stat} at the highest p{sub T}{sup reco} bin (10-12 GeV/c) with a beam polarization scale error of 9.4% and a p{sub T} scale error of 10%. Jets in the measured p{sub T}{sup reco} range arise primarily from hard-scattered gluons with momentum fraction 0.02 < x < 0.3 according to pythia. The measured A{sub LL} is compared with predictions that assume various {Delta}G(x) distributions based on the Gluck-Reya-Stratmann-Vogelsang parameterization. The present result imposes the limit -1.1 < {integral}{sub 0.02}{sup 0.3}dx{Delta}G(x,{mu}{sup 2} = 1 GeV{sup 2}) < 0.4 at 95% confidence level or {integral}{sub 0.02}{sup 0.3}dx{Delta}G(x,{mu}2 = 1 GeV{sup 2}) < 0.5 at 99% confidence level.

• Research Organization: Brookhaven National Laboratory (BNL) Relativistic Heavy Ion Collider
• Sponsoring Organization: DOE - OFFICE OF SCIENCE
• DOE Contract Number: AC02-98CH10886
• OSTI ID: 1034034
• Report Number(s): BNL--96165-2011-JA; KB0201021
• Journal Information: Physical Review. D, Particles, Fields, Gravitation and Cosmology, Journal Name: Physical Review. D, Particles, Fields, Gravitation and Cosmology Journal Issue: 1 Vol. 84; ISSN 1550-7998
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ALGORITHMS
ASYMMETRY
CHARGED PARTICLES
CROSS SECTIONS
GLUONS
HELICITY
MULTIPLICITY
PHOTONS
POLARIZATION
PRODUCTION
QUANTUM CHROMODYNAMICS
SHAPE
SIMULATION
relativistic heavy ion collider