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Register a new userQCD resummation effects in forward $J/psi$ and very backward jet inclusive production at the LHC
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We propose and study the inclusive production of a forward $J/psi$ and a very backward jet at the LHC as an observable to reveal high-energy resummation effects `a la BFKL. Our different predictions are based on the various existing mechanisms to describe the production of the $J/psi$, namely, NRQCD singlet and octet contributions, and the color evaporation model.
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In the spirit of Mueller-Navelet dijet production, we propose and study the inclusive production of a forward $J/psi$ and a very backward jet at the LHC as an observable to reveal high-energy resummation effects `a la BFKL. We obtain several predictions, which are based on the various mechanisms discussed in the literature to describe the production of the $J/psi$, namely, NRQCD singlet and octet contributions, and the color evaporation model.
We provide a description of the transverse momentum spectrum of single inclusive forward jets produced at the LHC, at the center-of-mass energies of 7 and 13 TeV, using the high energy factorization (HEF) framework. We subsequently study double inclusive forward jet production and, in particular, we calculate contributions to azimuthal angle distributions coming from double parton scattering. We also compare our results for double inclusive jet production to those obtained with the Pythia Monte Carlo generator. This comparison confirms that the HEF resummation acts like an initial state parton shower. It also points towards the need to include final state radiation effects in the HEF formalism.
We study $J/psi$ and $eta_c$ inclusive production in $Upsilon$ decay within the framework of nonrelativistic-QCD (NRQCD) factorization. In the latter case, for which no experimental data exist so far, we also include the $h_c$ feed-down contribution. We calculate the short distance coefficients completely through $mathcal{O}(alpha_s^5)$. The NRQCD predictions for the branching fraction $mathcal{B}(Upsilonto J/psi+X)$ via direct production, evaluated with different sets of long-distance matrix elements (LDMEs), all agree with the experimental data in a reasonable range of renormalization scale. Using $eta_c$ and $h_c$ LDMEs obtained from $J/psi$ and $chi_c$ ones via heavy-quark spin symmetry, we find that the bulk of $mathcal{B}(Upsilontoeta_c+X)$ via prompt production arises from the $cbar{c}({}^3!S_1^{[8]})$ Fock state. The experimental study of this decay process would, therefore, provide a particularly clean probe of the color octet mechanism of heavy-quarkonium production.
We study infrared contributions to semihard parton-parton interactions by considering an effective charge whose finite infrared behavior is constrained by a dynamical mass scale. Using an eikonal QCD-based model in order to connect this semihard parton-level dynamics to the hadron-hadron scattering, we obtain predictions for the proton-proton ($pp$) and antiproton-proton ($bar{p}p$) total cross sections, $sigma_{tot}^{pp,bar{p}p}$, and the ratios of the real to imaginary part of the forward scattering amplitude, $rho^{pp,bar{p}p}$. We discuss the theoretical aspects of this formalism and consider the phenomenological implications of a class of energy-dependent form factors in the high-energy behavior of the forward amplitude. We introduce integral dispersion relations specially tailored to relate the real and imaginary parts of eikonals with energy-dependent form factors. Our results, obtained using a group of updated sets of parton distribution functions (PDFs), are consistent with the recent data from the TOTEM, AUGER and Telescope Array experiments.
The associated production of J/psi + gamma at the LHC is studied within the NRQCD framework. The signal we focus on is the production of a J/psi and an isolated photon produced back-to-back, with their transverse momenta balanced. It is shown that even for very large values of transverse momentum (pT of the order of 50 GeV) the dominant contribution to this process is not fragmentation. This is because of the fact that fragmentation-type contributions to the cross-section come from only a q q(bar) initial state, which is suppressed at the LHC. We identify gg-initiated diagrams higher-order in alpha(s) which do have fragmentation-type vertices. We find, however, that the contribution of these diagrams is negligibly small.
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