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Register a new userRole of quarks in hadroproduction in high energy collisions
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Qualitative model for hadroproduction in high energy collisions considering two components (thermal and hard) to hadroproduction is proposed. Inclusive pseudorapidity distributions, $dsigma/deta$, and transverse momentum spectra, $d^2sigma/(deta dp_T^2)$, measured by different collaborations are considered in terms of this model. The shapes of the pseudorapidity distributions agree with that one can expect from the qualitative picture introduced. Finally, the differences between charged particle spectra produced in inclusive and diffractive events are discussed and the absence of the thermal component in the latter is observed.
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Quarkonium production in proton-proton collision is interesting in profiling the partons inside the nucleon. Recently, the impact of double parton scatterings (DPSs) was suggested by experimental data of associated quarkonium production (J/psi+Z, J/psi+W, and J/psi+J/psi) at the LHC and Tevatron, in addition to single parton scatterings (SPSs). In this proceedings contribution, we review the extraction of the effective parameter of the DPS through the evaluation of the SPS contributions under quark-hadron duality.
We present a complete description of top quark pair production in association with a hard photon in the dilepton channel. Our calculation is accurate to NLO in QCD. It is based on matrix elements for $e^+ u_e mu^-bar{ u}_mu b bar{b}gamma$ production and includes all resonant and non-resonant diagrams, interferences, and off-shell effects of the top quarks and the $W$ gauge bosons. This calculation constitutes the first full computation for top quark pair production with a final state photon in hadronic collisions at NLO in QCD. Numerical results for total and differential cross sections are presented for the LHC at a centre-of-mass energy of $sqrt{s}=13$ TeV. For a few observables relevant for new physics searches, beyond some kinematic bounds, we observe shape distortions of more than $100%$. In addition, we confirm that the size of the top quark off-shell effects for the total cross section is consistent with the expected uncertainties of the narrow width approximation. Results presented here are not only relevant for beyond the Standard Model physics searches but also important for precise measurements of the top-quark fiducial cross sections and top-quark properties at the LHC.
We study double prompt $J/psi$ hadroproduction within the nonrelativistic-QCD factorization formalism adopting the parton Reggeization approach to treat initial-state radiation in a gauge invariant and infrared-safe way. We present first predictions for the cross section distributions in the transverse momenta of the subleading $J/psi$ meson and the $J/psi$ pair. Already at leading order in $alpha_s$, these predictions as well as those for the total cross section and its distributions in the invariant mass $m_{psipsi}$ and the rapidity separation $|Y|$ of the $J/psi$ pair nicely agree with recent ATLAS and CMS measurements, except for the large-$m_{psipsi}$ and large-$|Y|$ regions, where the predictions substantially undershoot the data. In the latter regions, BFKL resummation is shown to enhance the cross sections by up to a factor of two and so to improve the description of the data.
The high-energy behaviour of the total cross section for highly virtual photons, as predicted by the BFKL equation at next-to-leading order (NLO) in QCD, is presented. The NLO BFKL predictions, improved by the BLM optimal scale setting, are in excellent agreement with recent OPAL and L3 data at CERN LEP2.
This volume is a collection of contributions for the 7-week program Probing Nucleons and Nuclei in High Energy Collisions that was held at the Institute for Nuclear Theory in Seattle, WA, USA, from October 1 until November 16, 2018. The program was dedicated to the physics of the Electron Ion Collider (EIC), the worlds first polarized electron-nucleon (ep) and electron-nucleus (eA) collider to be constructed in the USA. These proceedings are organized by chapters, corresponding to the weeks of the program: Week I, Generalized parton distributions; Week II, Transverse spin and TMDs; Week III, Longitudinal spin; Week IV, Symposium week; Weeks V & VI, eA collisions; Week VII, pA and AA collisions. We hope these proceedings will be useful to readers as a compilation of EIC-related science at the end of the second decade of the XXI century.
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