Observation of nuclear modifications in W-+/- boson production in pPb collisions at root s(NN)=8.16 TeV

Thumbnail Image
Journal Title
Journal ISSN
Volume Title

The production of ({W}^{±}) bosons is studied in proton-lead (pPb) collisions at a nucleon-nucleon centre-of-mass energy of (\sqrt{{s}{\mathrm{NN}}}=8.16\phantom{\rule{0.25em}{0ex}}\text{TeV}). Measurements are performed in the ({W}^{±}\to {\mu }^{±}{\nu }{\mu }) channel using a data sample corresponding to an integrated luminosity of (173.4±6.1\phantom{\rule{0.25em}{0ex}}{\text{nb}}^{-1}), collected by the CMS Collaboration at the LHC. The number of positively and negatively charged W bosons is determined separately in the muon pseudorapidity region in the laboratory frame (|{\eta }{\mathrm{lab}}^{\mu }|<2.4) and transverse momentum ({p}{T}^{\mu }>25\phantom{\rule{0.25em}{0ex}}\text{GeV}/c). The ({W}^{±}) boson differential cross sections, muon charge asymmetry, and the ratios of ({W}^{±}) boson yields for the proton-going over the Pb-going beam directions are reported as a function of the muon pseudorapidity in the nucleon-nucleon centre-of-mass frame. The measurements are compared to the predictions from theoretical calculations based on parton distribution functions (PDFs) at next-to-leading-order. The results favour PDF calculations that include nuclear modifications and provide constraints on the nuclear PDF global fits.

CMS, Heavy ions, Electroweak, W boson, pPb, nPDF, Astronomy & Astrophysics, Physics, Nuclear, Physics, Particles & Fields, Physics
Sirunyan, A. M., Tumasyan, A., Adam, W., Ambrogi, F., Asilar, E., Bergauer, T., Brandstetter, J., Dragicevic, M., Erö, J., Escalante Del Valle, A., Flechl, M., Frühwirth, R., Ghete, V. M., Hrubec, J., Jeitler, M., Krammer, N., Krätschmer, I., Liko, D., Madlener, T., … Woods, N. (2020). Observation of nuclear modifications in W± boson production in pPb collisions at sNN=8.16TeV. In Physics Letters B (Vol. 800, p. 135048). Elsevier BV. https://doi.org/10.1016/j.physletb.2019.135048