QCD analysis of the ATLAS and CMS W± and Z cross-section measurements and implications for the strange sea density

Abstract

In the present paper, the ATLAS inclusive W AE and Z boson production data are analyzed together with the CMS inclusive W AE and Z boson production data to investigate any possible tensions between the data sets and to determine the strange sea fraction, within the framework of a parton distribution function fit at next-to next-to-leading order in perturbative QCD.

Strange quark suppression from a simultaneous Monte Carlo analysis of parton distributions and fragmentation functions

“…The light quark PDFs are similar to other parametrizations [26,[77][78][79][80], as these are constrained mainly by the same DIS data sets [20,[37][38][39][40]. However, a significant difference exists for thed −ū asymmetry in the CSKK fit [27], which uses only HERA and LHC results and excludes the fixedtarget DY data [21,22]. The latter force a positive asymmetry peaking at x 0.1, in contrast to the negatived−ū driven by the HERA data.…”

“…The possible tension between the ATLAS and CMS measurements was investigated in a recent dedicated analysis by Cooper-Sarkar and Wichmann (CSKK) [27], who performed an NNLO fit to the ATLAS and CMS inclusive W ± and Z production data at √ s = 7 and 8 TeV, along with the combined HERA cross sections, using a K-factor approach. Their analysis found no significant tension between the HERA, ATLAS and CMS data, and supported an unsuppressed strange PDF at low x.…”

“…We explored this scenario by parametrizing s(x) ands(x) separately, but found that none of the SIDIS or other data sets showed clear preference for any significant s−s asymmetry within the current uncertainties. Future high-precision SIDIS data from the Jefferson Lab 12 GeV program or from the planned Electron-Ion Collider may allow more stringent determinations of the s ands PDFs, as would inclusion of W + charm production data from the LHC [86,87], with better knowledge of c-quark jet fragmentation and hadronization [27].…”

New results on parton densities of nucleons and nuclei

“…Other groups have studied the LHC data sensitive to strangeness in independent analyses. ATLAS and CMS data on Drell-Yan and W production seem to be compatible with each other when analysed with identical PDF parameterisations [35]. The ABM group…”

nCTEQ PDFs and the strange PDF at LHC - Vector boson production in heavy ion collisions

“…Fixed-target neutrino-nucleon DIS production of dimuons (νN → µ + µ − X) provided important constraints on s(x); however, as these neutrino experiments were performed on heavy targets, the nuclear corrections must be considered. 1 Proton-proton (pp) production of W and Z bosons at the LHC also provides insight on s(x); however, preliminary results show some tension between the various measurement channels [5].…”