Vector Quarkonia at the LHC with Jethad: A High-Energy Viewpoint

Abstract

In this review, we discuss and extend the study of the inclusive production of vector quarkonia, J/ψ and Υ, emitted with large transverse momenta and rapidities at the LHC. We adopt the novel ZCW19+ determination of fragmentation functions 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 formation 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 collinear formalism is enhanced by the BFKL resummation of next-to-leading energy logarithms arising in the t-channel. We employ the method to analyze the behavior of the rapidity distributions for double-inclusive vector quarkonium and inclusive vector quarkonium plus jet emissions. We discover that the natural stability of the high-energy series, previously seen 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 present the important message that vector quarkonia at the LHC via 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.

Forward & Far-Forward Heavy Hadrons with Jethad: A High-Energy Viewpoint

“…These findings mark a significant advancement in our understanding of high-energy QCD processes and offer promising prospects for future precision studies in this area. Subsequent analyses on vector quarkonia [253,254,334,335], B c mesons [314,317], and X Qq Q q tetraquarks [318], confirmed that this remarkable feature, known as natural stability of the BFKL resummation [312], comes out as basic property connected to the inclusive emission of any given heavy-flavored particle.…”

“…All predictions presented in this review were generated using JETHAD, a hybrid code that consistently integrates both PYTHON-and FORTRAN-based modules. JETHAD is specifically designed for computing, managing, and processing physical distributions defined within various formalisms [249,252,254,319]. Numeric calculations of differential distributions were primarily performed using FORTRAN 2008 modular routines within JETHAD, while the built-in PYTHON 3.0 analyzer was utilized for final data analysis and interpretation.…”

“…Version v0.4.7 [253] introduced quarkonium-sensitive reactions from NRQCD leadingtwist fragmentation. Novel features in v0.5.0 [254] and v0.5.1 [317] encompass an enhanced system for MHOU-related studies, an expanded list of observables with a focus on singly-and doubly-differential transverse-momentum production rates [276,289,317], and support for matching procedures with collinear factorization [324][325][326][327]329]. The most significant update of v0.5.2 is symJETHAD, a MATHEMATICA plugin devoted to symbolical calculations for high-energy QCD and the proton structure.…”

“…In such cases, a high-energy factorization treatment is needed, and it is inherently provided by the BFKL formalism. Consequently, another form of hybrid high-energy and collinear factorization is established [248][249][250][251][252][253][254] (see Refs. [255][256][257][258][259][260][261] for a close-in-spirit formalism), wherein high-energy resummed partonic cross sections are derived directly from BFKL and subsequently convoluted with collinear PDFs.…”