[Brahms-l] Fwd: New PHENIX paper on ALL of jet production

FYI

Flemming Videbaek
videbaek @ bnl.gov
Brookhaven National Lab
Physics Department
Bldg 510D
Upton, NY 11973


> From: Barbara Jacak <jacak_at_skipper.physics.sunysb.edu>
> Date: September 20, 2010 2:56:04 PM EDT
> To: Nu Xu <NXu_at_lbl.gov>, Wit Busza <busza_at_mit.edu>, "Videbaek,  
> Flemming" <videbaek_at_bnl.gov>, "Vigdor, Steven" <vigdor_at_bnl.gov>
> Subject: New PHENIX paper on ALL of jet production
>
> Dear Nu, Wit, Flemming and Steve,
>
> I am happy to announce that in one week's time, the
> PHENIX Collaboration will submit a paper to Phys.Rev.
> D. on the topic indicated in the subject line. Please
> find the title and abstract below.
>
> best regards,
> Barbara
>
> -----------------------------------------------------
> Title:
> Event Structure and Double Helicity Asymmetry in Jet Production from
> Polarized p + p Collisions at sqrt(s) = 200 GeV
>
> Abstract:
> We report on the event structure and double helicity asymmetry (ALL)
> of jet production in longitudinally polarized proton-proton  
> collisions at
> sqrt(s) = 200 GeV. Collision data were accumulated using the PHENIX
> detector in 2005. Photons and charged particles were measured at
> mid-rapidity |eta| < 0.35 with the requirement of a high-momentum
> (> 2 GeV/c) photon in the event.
>
> The event structure, such as multiplicity, pT density and thrust in  
> the
> PHENIX acceptance, were measured and compared with simulation results.
> For simulations the PYTHIA event generator and the GEANT detector
> simulation package were employed. 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 sum of pT of the
> particles in a cluster (pT_reco). The effect of detector response  
> and the
> underlying events on pT_reco was evaluated with the simulation. The
> production rate of reconstructed jets was measured and satisfactorily
> reproduced by the calculation, which is based on an NLO pQCD jet
> production cross section and the simulation. The ALL was measured at
> 4 < pT_reco < 12 GeV/c with an average beam polarization of <P> = 49%,
> and is -0.0014 ± 0.0037(stat.) at the lowest pT_reco bin (4-5 GeV/c)  
> and
> -0.0181±0.0282 (stat.) at the highest pT_reco bin (10-12 GeV/c) with  
> a
> beam polarization scale error of 9.4% and a pT scale error of 10%.
> Reconstructed jets in the measured pT_reco range are mainly produced
> from hard-scattered gluons with a momentum fraction of 0.02 < x < 0.3
> according to the PYTHIA simulation. The measured ALL is compared with
> predictions that assume various \DeltaG(x) distributions based on the
> GRSV parameterization. The present result imposes the limit
> -1.1 < Integral_0.02 ^ 0.3 dx\Delta G(x, μ^2 = 1 GeV^2 ) < 0.4 as 95%
> confidence interval or
> Integral_0.02 ^ 0.3 dx\Delta G(x, μ^2 = 1 GeV^2 )  < 0.5 as 99%
> confidence interval.



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