High-energy emissions of light mesons plus heavy flavor at the LHC and the Forward Physics Facility

Abstract

The study of the dynamics of strong interactions in the high-energy regime is a core line of frontier researches at the LHC as well as at new-generation colliding facilities. Here, the enhancement of energy logarithms due to diffractive semi-hard final states spoils the convergence of the perturbative series in the QCD running coupling, thus calling for an improvement of the pure collinear factorization that accounts for an all-order resummation of these large logarithmic contributions. Motivated by the recent discovery that inclusive emissions of heavy-flavored particles allow for clear signals of a stabilization of high-energy resummed differential distributions under higher-order corrections and scale variations, we provide novel predictions of rapidity and azimuthal-angle observables for the inclusive hadroproduction of a light meson (η or π ± ) in association with a heavy-flavored hadron (Λ c or b-flavored hadron). We calculate our observables in a hybrid high-energy and collinear factorization framework, where next-to-leading BFKL-resummed partonic cross sections are convoluted with collinear parton distributions and fragmentation functions. We consider kinematic ranges typically covered by acceptances of LHC detectors, and new ones coming from the combined tag of an ultra-forward particle at the future Forward Physics Facility (FPF) and of a central one at ATLAS via a tight timing-coincidence setup. By performing a detailed study on uncertainties associated to collinear inputs via a replica-driven analysis, as well as on ones intrinsically coming from the high-energy resummation, we highlight the challenges and the steps required to gauge the feasibility of precision studies of our processes.

The next-to-leading order Higgs impact factor in the infinite top-mass limit

“…This result is remarkable, since previous studies on light jets and hadrons [108,109,112] highlighted how higher-order contributions, noticeably large and with opposite sign with respect to LL terms, are the source of strong instabilities that have prevented any attempt at making precision studies of those processes so far. Soon later, an analogous stabilization pattern was observed also in NLL distributions sensitive to heavy-flavored emissions [117][118][119]122]. Second, differential cross sections in the Higgs transverse momentum turned out to be suitable observables whereby discriminating BFKL-driven predictions from fixed-order results, their mutual separation becoming more and more sizeable when the momentum increases.…”

“…Therefore, proton-initiated two-particle semi-hard processes can be described by the hands of a hybrid high-energy and collinear formalism, where the BFKL resummation determines the general structure of the high-energy cross section, and impact factors encode collinear inputs coming from PDFs. 1 A non-inclusive list of hadronic processes studied via the hybrid factorization and with full NLL accuracy includes: Mueller-Navelet jets [100], for which several phenomenological analyses were provided [76,[101][102][103][104][105][106][107][108][109][110][111][112] and compared with 7 TeV LHC data [113], then two-hadron [76,112,[114][115][116][117][118][119] and hadron-jet [112,[116][117][118][119][120][121][122] inclusive tags. NLL analyses on leptonic-initiated reactions were mainly focused on the exclusive electroproduction of light vector mesons [123,124] and on the light-by-light scattering [125][126][127].…”

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

“…The stabilization mechanism is encoded in the peculiar behavior of the heavy-hadron gluon FF, and it comes out as a general feature shared by all the heavyflavored species investigated so far, heavy-light hadrons [63,64], vector quarkonia [67], and now ( * ) mesons. We believe that the favorable statistics of our cross sections motivates further analyses on the high-energy spectrum of QCD via heavy flavor at the (high-luminosity) LHC [82,83] and in ultra-forward directions of rapidity, as the ones accessible at the forthcoming Forward Physics Facility (FPF) [84][85][86]. Our plan for future extensions of studies presented in this Letter is twofold.…”

Unveiling the proton structure via transverse-momentum-dependent gluon distributions

“…In the small-x and moderate-p T regime the unpolarized gluon TMD is connected with the BFKL unintegrated distribution [18][19][20], of which several recent studies have appeared so far [21][22][23][24][25][26][27][28]. Analyses on the dynamics of strong interactions at high energies via the BFKL approach were recently performed in [29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47].…”