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Register a new user$eta_c$ production in photon - induced interactions at the LHC
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In this paper we investigate the $eta_c$ production by photon - photon and photon - hadron interactions in $pp$ and $pA$ collisions at the LHC energies. The inclusive and diffractive contributions for the $eta_c$ photoproduction are estimated using the nonrelativistic quantum chromodynamics (NRQCD) formalism. We estimate the rapidity and transverse momentum distributions for the $eta_c$ photoproduction in hadronic collisions at the LHC and present our estimate for the total cross sections at the Run 2 energies. A comparison with the predictions for the exclusive $eta_c$ photoproduction, which is a direct probe of the Odderon, also is presented.
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We analyse in detail the role of additional hadron-hadron interactions in elastic photon-initiated (PI) production at the LHC, both in $pp$ and heavy ion collisions. We first demonstrate that the source of difference between our predictions and other results in the literature for PI muon pair production is dominantly due to an unphysical cut that is imposed in these latter results on the dimuon-hadron impact parameter. We in addition show that this is experimentally disfavoured by the shape of the muon kinematic distributions measured by ATLAS in ultraperipheral PbPb collisions. We then consider the theoretical uncertainty due to the survival probability for no additional hadron-hadron interactions, and in particular the role this may play in the tendency for the predicted cross sections to lie somewhat above ATLAS data on PI muon pair production, in both $pp$ and PbPb collisions. This difference is relatively mild, at the $sim 10%$ level, and hence a very good control over the theory is clearly required. We show that this uncertainty is very small, and it is only by taking very extreme and rather unphysical variations in the modelling of the survival factor that this tension can be removed. This underlines the basic, rather model independent, point that a significant fraction of elastic PI scattering occurs for hadron-hadron impact parameters that are simply outside the range of QCD interactions, and hence this sets a lower bound on the survival factor in any physically reasonable approach. Finally, other possible origins for this discrepancy are discussed.
Experimental prospects for studying high-energy photon-photon and photon-proton interactions at the CERN Large Hadron Collider (LHC) are discussed. Cross sections are calculated for many electroweak and beyond the Standard Model processes. Selection strategies based on photon interaction tagging techniques are studied. Assuming a typical LHC multipurpose detector, various signals and their irreducible backgrounds are presented after applying acceptance cuts. Prospects are discussed for the Higgs boson search, detection of supersymmetric particles and of anomalous quartic gauge couplings, as well as for the top quark physics.
In this contribution, we study the inclusive and diffractive $eta_{c}$ photoproduction in $pp$ and $pPb$ ultra-peripheral collisions (UPCs) at the LHC Run 2 energies. The quarkonium production is studied using nonrelativistic quantum chromodynamics (NRQCD) formalism. We present predictions for rapidity and transverse momentum distributions for the $eta_c$ photoproduction and present our estimate for the total cross sections at the Run 2 energies.
Next-to-leading order predictions matched to parton showers are compared with recent ATLAS data on inclusive photon production and CMS data on associated photon and jet production in pp and pPb collisions at different centre-of-mass energies of the LHC. We find good agreement and, as expected, considerably reduced scale uncertainties compared to previous theoretical calculations. Predictions are made for the ratio of inclusive photons over decay photons $R_gamma$, an important quantity to evaluate the significance of additional photon sources, e.g. thermal radiation from a Quark-Gluon-Plasma, and for distributions in the parton momentum fraction in lead ions $x_{rm Pb}^{rm obs}$, that could be determined by ALICE, ATLAS, CMS and LHCb in ongoing analyses of photon+jet production in pPb collisions at $sqrt{s_{NN}}=5.02$ TeV. These data should have an important impact on the determination of nuclear effects such as shadowing at low $x$.
The exclusive two-photon production at the LHC of pairs of W and Z bosons provides a novel and unique test-ground for the electroweak gauge boson sector. In particular it offers, thanks to high gamma-gamma center-of-mass energies, large and direct sensitivity to the anomalous quartic gauge couplings otherwise very difficult to investigate at the LHC. An initial analysis has been performed assuming leptonic decays and generic acceptance cuts. Simulation of a simple counting experiment has shown for the integrated luminosity of 10 fb-1 at least four thousand times larger sensitivity to the genuine quartic couplings, a_0^W, a_0^Z, a_C^W and a_C^Z, than those obtained at LEP. The impact of the unitarity constraints on the estimated limits has been studied using the dipole form-factors. Finally, differential distributions of the decay leptons have been provided to illustrate the potential for further improvements of the sensitivities.
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