BFKL phenomenology: resummation of high-energy logs in semi-hard processes at LHC

A study of differential cross sections and azimuthal observables for semi-hard processes at LHC energies, including BFKL resummation effects, is presented. Particular attention has been paid to the behaviour of the azimuthal correlation momenta, when a couple of forward/backward jets or identified hadrons is produced in the final state with a large rapidity separation. Three- and four- jet production has been also considered, the main focus lying on the definition of new, generalized azimuthal observables, whose dependence on the transverse momenta and the rapidities of the central jet(s) can be considered as a distinct signal of the onset of BFKL dynamics.Comment: 6 pages, 7 figures, Talk given at the 5th Young Researchers Workshop "Physics Challenges in the LHC Era", Frascati, May 9 and 12, 201

Vector quarkonia at the LHC with JETHAD: A high-energy viewpoint

In this review we discuss and extend the study of the inclusive production of vector quarkonia, $J/\psi$ and $\Upsilon$, emitted with large transverse momenta and rapidities at the LHC. We adopt the novel ZCW19$^+$ determination to depict the quarkonium production mechanism at the next-to-leading level of perturbative QCD. This approach is based on the nonrelativistic QCD formalism well adapted to describe the production of a quarkonium state from the collinear fragmentation of a gluon or a constituent heavy quark at the lowest energy scale. We rely upon the NLL/NLO$^+$ hybrid high-energy and collinear factorization for differential cross sections, where the standard collinear formalism is enhanced by the BFKL resummation of next-to-leading energy logarithms arising in the $t$-channel. We employ the JETHAD method to analyze the behavior of rapidity distributions for double inclusive vector-quarkonium and inclusive vector-quarkonium plus jet emissions. We discovered that the natural stability of the high-energy series, previously observed in observables sensitive to the emission of hadrons with heavy flavor detected in the rapidity acceptance of LHC barrel calorimeters, becomes even more manifest when these particles are tagged in forward regions covered by endcaps. Our findings brace the important message that vector quarkonia at the LHC via the hybrid factorization offer a unique chance to perform precision studies of high-energy QCD, as well as an intriguing opportunity to shed light on the quarkonium production puzzle.Comment: 42 pages, 8 figures, 526 references. Invited review articl

Stabilizing BFKL via heavy-flavor and NRQCD fragmentation

We bring evidence that the recently discovered property of natural stability of the high-energy resummation is directly connected to the fragmentation mechanism of heavy hadrons. As a phenomenological support, we provide predictions for differential distributions sensitive to heavy-hadron tags, calculated at the next-to-leading logarithmic level of the hybrid high-energy/collinear factorization (NLL/NLO), as implemented in the JETHAD multimodular code. We show that the stabilizing mechanism is encoded in gluon channels of both heavy-flavor collinear fragmentation functions extracted from data and the ones evolved from a non-relativistic QCD input.Comment: 6 pages, 1 figure. Presented at Diffraction and Low-x 2022, 24-30 September 202

Hunting BFKL in semi-hard reactions at the LHC

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. $\kappa$-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 JETHAD, a numerical tool recently developed, suited for the computation of inclusive semi-hard reactions is provided.Comment: 47 pages, 18 figures, 1 table; corrected a misprint in Eq. (17); updated keywords and added a missing $\alpha_s^3$ term at the third line of Section 2.2; updated reference

Unraveling the unintegrated gluon distribution in the proton via ρ\rho-meson leptoproduction

Sufficiently inclusive processes, like the deep inelastic scattering (DIS), are described in terms of scale-dependent parton distributions, which correspond to the density of partons with a given longitudinal momentum fraction, integrated over the parton transverse momentum. For less inclusive processes, one needs to consider densities unintegrated over the transverse momentum. This work focuses on the unintegrated gluon distribution (UGD), describing the probability that a gluon can be emitted by a colliding proton, with definite longitudinal fraction and transverse momentum. Through the leptoproduction of the $\rho$-meson at HERA, existent models for the UGD will be investigated and compared with experimental data.Comment: 12 pages, 5 figures; version published in Nuovo Cim.

The high-energy spectrum of QCD from inclusive emissions of charmed BB-mesons

We investigate the high-energy behavior of strong interactions through a study on the inclusive hadroproduction of charmed $B$-mesons ($B_c$ or $B_c^*$ states) accompanied by non-charmed $b$-hadron or light-flavored jet emissions at LHC energies and kinematic configurations. By making use of the hybrid high-energy and collinear factorization, where the standard fixed-order description based on collinear parton densities and fragmentation functions is enhanced via the Balitsky-Fadin-Kuraev-Lipatov (BFKL) resummation of energy logarithms, we perform a full next-to-leading order analysis of distributions differential in rapidities and azimuthal angles calculated by the hands of the JETHAD multi-modular working package. The large observed transverse momenta justify the use of non-relativistic QCD next-to-leading order fragmentation functions to describe the heavy-flavored meson production mechanism. We come out with the conclusion that the study of this process can be included in forthcoming analyses at the (high-luminosity) LHC as a tool to access the QCD dynamics at high energies and to explore possible common ground between different resummation approaches.Comment: 10 pages, 4 figures, 90 references, version published in Phys. Lett.

A journey into the proton structure: Progresses and challenges

Unraveling the inner dynamics of gluons and quarks inside nucleons is a primary target of studies at new-generation colliding machines. Finding an answer to fundamental problems of Quantum ChromoDynamics, such as the origin of nucleon mass and spin, strongly depends on our ability of reconstructing the 3D motion of partons inside the parent hadrons. We present progresses and challenges in the extraction of TMD parton densities, with particular attention to the ones describing polarization states of gluons, which still represent an largely unexplored field. Then, we highlight connections with corresponding parton densities in the high-energy limit, the so-called unintegrated gluon distributions or UGDs and, more in general, to recent developments in high-energy physics.Comment: 10 pages, 2 figures, version published in Univers

3D tomography of the nucleon: transverse-momentum-dependent gluon distributions

We perform explorative analyses of the 3D gluon content of the proton via a study of (un)polarized twist-2 gluon TMDs, calculated in a spectator model for the parent nucleon. Our approach encodes a flexible parametrization for the spectator-mass density, suited to describe both moderate and small-$x$ effects. All these prospective developments are relevant in the investigation of the gluon dynamics inside nucleons and nuclei, which constitutes one of the major goals of new-generation colliding machines, as the EIC, the HL-LHC and NICA.Comment: 5 pages, 1 figure, 106th National Congress of the Italian Physical Society (SIF), contribution selected by the Scientific Committee for Best Communications, paper submitted to Nuovo Cim.

Collective Phenomena in pppp and epep Scattering

Bjorken scaling violation in deep inelastic electron-proton scattering (DIS) is related to the rise of hadronic cross sections by using the additive quark model. Of special interest is the connection between saturation in the low-$x$ behavior of the DIS structure functions (SF) and possible slow-down of the $pp$ cross section rise due to saturation effects. We also identify saturation effects in the DIS SF with phase transition that can be described by the Van der Waals equation of state.Comment: 4 pages, 1 figure; presented by L. Jenkovszky at "Diffraction 2016", International Workshop on Diffraction in High-Energy Physics, Acireale (Catania, Sicily), Sept. 2-8, 2016; to be published in the conference proceedings by AI