On relation between Parton Branching Approach and CCFM evolution

Abstract

We consider the associated production of electroweak gauge bosons and charm or beauty quark jets at the LHC using the $k_T$-factorization framework. We apply the transverse momentum dependent (TMD) parton distributions in a proton obtained from the Parton Branching (PB) method as well as from the Catani-Ciafaloni-Fiorani-Marchesini (CCFM) evolution equation. For the PB approach, our prescription merges the standard leading order $\mathcal{O}(\alpha {\alpha }_s)$ $k_T$-factorization calculations with several tree-level next-to-leading order $\mathcal{O}(\alpha {\alpha }_s^2)$ off-shell production amplitudes. For the CCFM scenario, our consideration is based on the $\mathcal{O}(\alpha {\alpha }_s^2)$ off-shell gluon-gluon fusion subprocess $g^{\ast }{g}^{\ast }\to Z/W+Q\bar{Q}$ and some subleading $\mathcal{O}(\alpha {\alpha }_s^2)$ subprocesses involving quark interactions, taken into account in conventional (collinear) QCD factorization. We find that the $W+c$ and $Z+b$ cross sections, calculated within the PB and CCFM-based schemes with the proper choice of leading and next-to-leading subprocesses, are in good agreement with each other, thus establishing a correspondence between these two scenarios. A comparison with the latest LHC experimental data is given and the necessity for the proper off-shell treatment of the production amplitudes in determination of the parameters of the TMD parton density is demonstrated.

15 pages, 8 figures

References in corpus (10)

• Parton distributions in the LHC era: MMHT 2014 PDFs
• MCFM for the Tevatron and the LHC
• The CCFM Monte Carlo generator CASCADE 2.2.0
• Measurement of differential production cross-sections for a $Z$ boson in association with $b$-jets in 7 TeV proton-proton collisions with the ATLAS detector
• The CCFM uPDF evolution uPDFevolv
• Forward-Central Jet Correlations at the Large Hadron Collider
• BCFW recursion for off-shell gluons
• Hadroproduction of electroweak gauge boson plus jets and TMD parton density functions
• Production of electroweak gauge bosons in off-shell gluon-gluon fusion
• Associated production of $Z$ bosons and $b$-jets at the LHC in the combined $k_T$ + collinear QCD factorization approach