Measurement of theW→eνandZ/γ*→e+e−

Abstract

We report measurements of the charge-separated W +(−) → e +(−) + νe(νe) and Z/γ * → e + e − production cross sections at mid-rapidity in proton-proton collisions at √ s = 500 GeV. These results are based on 13.2 pb −1 of data recorded in 2009 by the STAR detector at RHIC. Production cross sections for W bosons that decay via the eν channel were measured to be σ(pp → W + X)·BR(W + → e + νe) = 117.3 ± 5.9(stat) ± 6.2(syst) ± 15.2(lumi) pb, and σ(pp → W − X)·BR(W − → e −ν e) = 43.3 ± 4.6(stat) ± 3.4(syst) ± 5.6(lumi) pb. For Z/γ * production, σ(pp → Z/γ * X)·BR(Z/γ * → e + e − ) = 7.7 ± 2.1(stat) +0.5 −0.9 (syst) ± 1.0(lumi) pb was measured for di-lepton invariant masses m e + e − between 70 and 110 GeV/c 2 . First measurements of the W cross section ratio, σ(pp → W + X)/σ(pp → W − X), at √ s = 500 GeV are also reported. Theoretical predictions, calculated using recent parton distribution functions, are found to agree with the measured cross sections.

Cross section and longitudinal single-spin asymmetry AL for forward W±→μ±ν production in polarized Adare1, Aidala2, Ajitanand3 et al. 2018Phys. Rev. DSelf Cite

“…Figure 8 shows the extracted total cross sections for inclusive W AE → μ AE production in p þ p collisions at a center-of-mass energy of 510 GeV. The cross sections are consistent within uncertainties with previous measurements at this energy from central W → e decay channels [12,23] and with the expected NLO predictions. The uncertainties TABLE II.…”

Measurement of charm production at central rapidity in proton-proton collisions at $ \sqrt {s} = 2.76\;{\text{TeV}} $

“…[42] and of the LHC data [13][14][15] shown in the figure is P v = 0.60 ± 0.01, and is represented by a solid yellow vertical band. Right: Energy dependence of the total nucleon-nucleon charm production cross section [14][15][16][46][47][48]. In case of proton-nucleus (pA) or deuteron-nucleus (dA) collisions, the measured cross sections have been scaled down by the number of binary nucleonnucleon collisions calculated in a Glauber model of the proton-nucleus or deuteron-nucleus collision geometry.…”

Measurement of Longitudinal Spin Asymmetries for Weak Boson Production in Polarized Proton-Proton Collisions at RHIC

“…The W ± → τ ± ν τ and Z/γ * → e + e − electroweak contributions were determined from Monte Carlo (MC) samples simulated using pythia 6.422 [27] with the Perugia 0 tune [28]. The generated events were passed through a geant [29] model of the STAR detector response, embedded in real STAR zero-bias triggered events [25], and reconstructed using the same selection criteria as the data. In the W ± → τ ± ν τ sample the tauola package was used for the polarized τ ± decay [30].…”

“…Background yields from QCD processes were estimated independently for each η e bin through two contributions described in Ref. [25], referred to as the second EEMC and data-driven QCD. These background contributions originate primarily from events thatmidrapidity satisfy the W ± selection criteria but contain jets escaping detection due to the missing calorimeter coverage for η < −1 and η > 2.…”