Single-spin asymmetries inWboson production at next-to-leading order

Abstract

We present an analytic next-to-leading order QCD calculation of the partonic cross sections for single-inclusive lepton production in hadronic collisions, when the lepton originates from the decay of an intermediate electroweak boson and is produced at high transverse momentum. In particular, we consider the case of incoming longitudinally polarized protons for which parity-violating single-spin asymmetries arise that are exploited in the W boson program at RHIC to constrain the proton's helicity parton distributions. Our calculation enables a very fast and efficient numerical computation of the relevant spin asymmetries at RHIC, which is an important ingredient for the inclusion of RHIC data in a global analysis of nucleon helicity structure. We confirm the validity of our calculation by comparing with an existing code that treats the next-to-leading order cross sections entirely numerically by Monte-Carlo integration techniques. We also provide new comparisons of the present RHIC data with results for some of the sets of polarized parton distributions available in the literature.

Effect of sea quarks on the single-spin asymmetries ALW± in polarized pp collisions at RHIC

“…There are also some theoretical studies on A W ± L based on available extractions or parametrizations of quark helicity distributions [33][34][35][36]. The predictions of A W ± L [15-21, 37, 38] are given, and it is found that the higher order QCD corrections are small [39][40][41][42]. Especially in Ref.…”

“…Especially in Ref. [42], the analytic expressions for the spin-dependent asymmetries at next-to-leading order are given and the calculated results with sea quark helicity distributions from different groups are compared with the experimental data [30]. It is found that the data prefer a rather sizable positive valued ∆ū.…”

Measurement of the longitudinal spin asymmetries for weak boson production in proton-proton collisions at s=510 GeV

“…The observed positron and electron pseudorapidities, η e , are related to y W and to the decay angle of the positron and electron in the W rest frame [19]. Higher-order corrections to A L (η e ) are known [20][21][22] and have been incorporated into the aforementioned global analyses.…”

Measurement of parity-violating spin asymmetries inW±production at midrapidity in longitudinally polarizedp+pAdare1, Makek2, Zou3 2016Phys. Rev. D372300View full textAdd to dashboardCite

“…These results are shown in Fig. 2 with two theoretical calculations: (CHE) [21] for the NNPDFpol1.1 [14] and a recent calculation [31] using the DSSV 14 PDF sets [32]. While the DSSV 14 curve was obtained from a global fit of DIS and SIDIS data (including recent COMPASS results [15,16]), the NNPDFpol1.1 uncertainty band contains the 2012 STAR [11] result for flavor separation in addition to DIS data.…”

“…To calculate the 2013 positive and negative η bin asymmetries a generalized form for these equations was used. The green line and shaded region shows a theoretical calculation using CHE [21] with the NNPDFpol1.1 PDF sets [14], while the dashed magenta line shows the DSSV14 calculation [31].…”