Dijet azimuthal decorrelations at the LHC in the parton Reggeization approach

Abstract

We study inclusive dijet azimuthal decorrelations in proton-proton collisions at the CERN LHC invoking the hypothesis of parton Reggeization in t−channel exchanges at high energies. In the parton Reggeization approach, the main contribution to the azimuthal angle difference between the two most energetic jets is due to the Reggeon-Reggeon-particle-particle scattering, when the fusion of two Reggeized gluons into a pair of Yang-Mills gluons dominates. Using a high-energy factorization scheme with the Kimber-Martin-Ryskin unintegrated parton distribution functions and the Fadin-Lipatov effective vertices we obtain good agreement of our calculations with recent measurements by the ATLAS and CMS Collaborations at the CERN LHC.

Charm quark and meson production in association with single-jet at the LHC

“…The off-shell matrix elements are known only in the LO and only for limited types of QCD 2 → 2 processes (see e.g. heavy quarks [21], dijet [19], Drell-Yan [22]). Some first steps to calculate NLO corrections in the k T -factorization framework have been done only very recently for diphoton production [23,24].…”

“…We shall use the leading-order (LO) collinear approach as well as the k T -factorization approach. The latter approach was successfully used both for cc production [9] and for inclusive jet [18], dijet [19] and even four-jet production very recently [13]. In our practical exploration we shall use an unique tool -A Very Handy LIBrary (AVHLIB) 1 [20] prepared for calculating multileg processes, up to four-particle final states within both collinear and k T -factorization frameworks.…”

New single- and double-parton scattering mechanisms for double charmed meson production

“…The useful analytical formulae for |M RR→g | 2 , |M RR→gg | 2 and |M RR→cc | 2 squared amplitudes used in the calculations here can be found in Refs. [8,13]. We use the LO Kimber-Martin-Ryskin (KMR) unPDFs, generated from the LO set of a up-to-date MMHT2014 collinear PDFs fitted also to the LHC data.…”

Multi-Regge kinematics and azimuthal angle observables for inclusive four-jet production

“…4 k 1,2 - tributions are already contained in the calculations here discussed, in particular, for the ratios R M N L P Q R . It will be very important to compare against the BFKL Monte Carlo code BFKLex [36][37][38][39][40][41][42] as well as to calculate the same quantities with other, more conventional, approaches [43][44][45] in order to gauge if they differ from our results. This includes those analysis where the four-jet predictions stem from two independent gluon ladders [46,47].…”