https://doi.org/10.1140/epjc/s10052-017-5369-5
Regular Article - Theoretical Physics
Associated production of Z bosons and b-jets at the LHC in the combined
+ collinear QCD factorization approach
1
P.N. Lebedev Physics Institute, 119991, Moscow, Russia
2
Deutsches Elektronen-Synchrotron, Notkestrasse 85, Hamburg, Germany
3
Skobeltsyn Institute of Nuclear Physics, Moscow State University, 119991, Moscow, Russia
4
Joint Institute for Nuclear Research, 141980, Dubna, Moscow Region, Russia
* e-mail: lipatov@theory.sinp.msu.ru
Received:
30
August
2017
Accepted:
3
November
2017
Published online:
16
November
2017
We consider the production of Z bosons associated with beauty quarks at the LHC using a combined + collinear QCD factorization approach, which interpolates between small x and large x physics. Our consideration is based on the off-shell gluon–gluon fusion subprocess
at the leading order
(where the Z boson further decays into a lepton pair), calculated in the
-factorization approach, and several subleading
and
subprocesses involving quark–antiquark and quark–gluon interactions, taken into account in conventional (collinear) QCD factorization. The contributions from double parton scattering are discussed as well. The transverse momentum dependent (or unintegrated) gluon densities in a proton are derived from Catani–Ciafaloni–Fiorani–Marchesini (CCFM) evolution equation. We achieve reasonably good agreement with the latest data taken by CMS and ATLAS Collaborations. The comparison of our results with next-to-leading-order pQCD predictions, obtained in the collinear QCD factorization, is presented. We discuss the uncertainties of our calculations and demonstrate the importance of subleading quark-involving contributions in describing the LHC data in the whole kinematic region.
© The Author(s), 2017