Hunting BFKL in semi-hard reactions at the LHC

Abstract

The agreement between calculations inspired by the resummation of energy logarithms, known as BFKL approach, and experimental data in the semi-hard sector of QCD has become manifest after a wealthy series of phenomenological analyses. However, the contingency that the same data could be concurrently portrayed at the hand of fixed-order, DGLAP-based calculations, has been pointed out recently, but not yet punctually addressed. Taking advantage of the richness of configurations gained by combining the acceptances of CMS and CASTOR detectors, we give results in the full next-to-leading logarithmic approximation of cross sections, azimuthal correlations and azimuthal distributions for three distinct semi-hard processes, each of them featuring a peculiar final-state exclusiveness. Then, making use of disjoint intervals for the transverse momenta of the emitted objects, i.e. $$\kappa $$ κ -windows, we clearly highlight how high-energy resummed and fixed-order driven predictions for semi-hard sensitive observables can be decisively discriminated in the kinematic ranges typical of current and forthcoming analyses at the LHC. The scale-optimization issue is also introduced and explored, while the uncertainty coming from the use of different PDF and FF set is deservedly handled. Finally, a brief overview of , a numerical tool recently developed, suited for the computation of inclusive semi-hard reactions is provided.

Phenomenology of the hadronic structure at small-$x$

“…Uncertainty bands represent the effect of varying a 2 (µ 0 = 1 GeV) between 0.0 and 0.6. Numerical results were obtained through the Leptonic-Exclusive-Amplitudes (LExA) super-module of the JETHAD interface [56]. Figures from [105].…”

“…The first class of processes that serves as probe channels of the BFKL dynamics is represented by the inclusive semi-hard emission [54] of two particles with high transverse momenta and well separated in rapidity (see Refs. [55,56] for an overview of recent applications). Here the established factorization is hybrid.…”

The Forward Physics Facility: Sites, Experiments, and Physics Potential

“…A possible first sign of the onset of BFKL dynamics at LHC energies emerged in the Mueller-Navelet dijet channel [235], where NLA BFKL predictions [236,237] and CMS data [238] were compared among each other for azimuthal-angle distributions at 7 TeV, with a satisfactory level of agreement. Quite recently, it was shown how certain kinematic configurations probed in the production of jets [239,240] and identified hadron final states [241,242] might allow for a clear discrimination between BFKL-driven predictions and the standard collinear factorization ones, when data will be available. As discussed in the following, we expect that measurements at the FPF will also help to discriminate between these two approaches.…”

Towards leading-twist $T$-odd TMD gluon distributions

“…Recent studies were done on the BFKL unintegrated gluon distribution, which is the small-x and large-p T counterpart of the unpolarized gluon TMD [18][19][20][21][22][23] and, more in general, on the dynamics of strong interactions at high energies [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40]. A connection between the high-energy and the TMD factorization was highlighted in Refs.…”