Cross Section and Parity-Violating Spin Asymmetries of W± Boson Production in Polarized p + p Collisions at √s = 500 GeV

PHENIX Collaboration

Homma Kensuke

Iwanaga Y.

Kijima K. M.

Nakamiya Y.

Nihashi M.

Ouchida M.

Shigaki Kenta

Sugitate Toru

Torii H.

Tsuchimoto Y.

Watanabe K.

Physical Review Letters

Large parity-violating longitudinal single-spin asymmetries A^<e+>_<L> = 0.86^<+0.30>_<-0.14> and A^<e->_<L> = 0.88^<+0.12>_<-0.71> are observed for inclusive high transverse momentum electrons and positrons in polarized p + p collisions at a center-of-mass energy of √s = 500 GeV with the PHENIX detector at RHIC. These e± come mainly　from the decay of W± and Z0 bosons, and their asymmetries directly demonstrate parity violation in the couplings of the W± to the light quarks. The observed electron and positron yields were used to estimate W± boson production cross sections for the e± channels of ð(pp → W+X) × BR(W+ → e+ve) = 144.1 ± 21.2(stat)^<+3.4>_<-10.3>(syst) ± 21.6(norm) pb, and ð(pp → W-X) × BR(W- → e-v^^-e) = 31.7 ± 12.1(stat)^<+10.1>_<-8.2>(syst) ± 4.8(norm) pb.

Physics [ 420 ]

eng

American Physical Society

Copyright (c) 2011 American Physical Society

[ISSN] 0031-9007

[NCID] AA00773679

[DOI] 10.1103/PhysRevLett.106.062001