Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userPhoton from the annihilation process with CGC in the $pA$ collision
361
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We discuss the photon production in the $pA$ collision in a framework of the color glass condensate (CGC) with expansion in terms of the proton color source $rho_p$. We work in a regime where the color density $rho_A$ of the nucleus is large enough to justify the CGC treatment, while soft gluons in the proton could be dominant over quark components but do not yet belong to the CGC regime, so that we can still expand the amplitude in powers of $rho_p$. The zeroth-order contribution to the photon production is known to appear from the Bremsstrahlung process and the first-order corrections consist of the Bremsstrahlung diagrams with pair produced quarks and the annihilation diagrams of quarks involving a gluon sourced by $rho_p$. Because the final states are different there is no interference between these two processes. In this work we elucidate calculation procedures in details focusing on the annihilation diagrams only. Using the McLerran-Venugopalan model for the color average we numerically calculate the photon production rate and discuss functional forms that fit the numerical results.
rate research
Read More
Quarkonium production mechanism in high multiplicity small collision systems has recently been pursued in the color-glass-condensate (CGC) effective theory combined with non-relativistic QCD (NRQCD) factorization, allowing to study initial state interactions. Quarkonium polarization, potentially measured in future experiments, would help elucidate the quarkonium production mechanism at high multiplicities. In this paper, we provide predictions on $J/psi$ polarization parameters in high multiplicity proton-proton ($pp$) and proton-nucleus ($pA$) collisions within the CGC+NRQCD framework. Theoretical predictions are given for $J/psi$ rapidity $2.5< y_{J/psi}<4$, charged-particle multiplicity pseudorapidity $|eta_{ch} | <1$ and energies $sqrt{S}=13mathrm{~TeV}$ for $pp$, $sqrt{S}=8.16mathrm{~TeV}$ for $pA$ collisions. Considering two leptonic frame choices (Collins - Soper and helicity) we find a weak polarization of $J/psi$ that additionally decreases with growing event activities. No significant system size dependence between $pp$ and $pA$ collisions is obtained - this could be a new constraint to initial state interactions in small collision systems.
We compute the inclusive differential cross section production of the pseudo-scalar meson eta in high-energy proton-proton (pp) and proton-nucleus (pA) collisions. We use an effective coupling between gluons and eta meson to derive a reduction formula that relates the eta production to a field-strength tensor correlator. For pA collisions we take into account saturation effects on the nucleus side by using the Color Glass Condensate formalism to evaluate this correlator. We derive new results for Wilson line - color charges correlators in the McLerran-Venugopalan model needed in the computation of eta production. The unintegrated parton distribution functions are used to characterize the gluon distribution inside protons. We show that in pp collisions, the cross section depends on the parametrization of unintegrated parton distribution functions and thus, it can be used to put constraints on these distributions. We also demonstrate that in pA collisions, the cross section is sensitive to saturation effects so it can be utilized to estimate the value of the saturation scale.
Annihilation of different dark matter (DM) candidates into Standard Model (SM) particles could be detected through their contribution to the gamma ray fluxes that are measured on the Earth. The magnitude of such contributions depends on the particular DM candidate, but certain imprints of produced photon spectra may be analyzed in a model-independent fashion. In this work we provide the fitting formulae for the photon spectra generated by WIMP annihilation into quarks, leptons and gauge bosons channels in a wide range of WIMP masses.
Events with tagged photons in the process of electron-positron annihilation into hadrons are considered. The initial state radiation is suggested to scan the hadronic cross section with the energy. QED radiative corrections are taken into account. The results for the total and exclusive cross sections are given in an analytic form. Some numerical estimates are presented.
We compute the $J/psi$ polarization observables $lambda_theta$, $lambda_phi$, $lambda_{thetaphi}$ in a Color Glass Condensate (CGC) + nonrelativistic QCQ (NRQCD) formalism that includes contributions from both color singlet and color octet intermediate states. Our results are compared to low $p_T$ data on $J/psi$ polarization from the LHCb and ALICE experiments on proton-proton collisions at center-of-mass energies of $sqrt{s}=7$ TeV and 8 TeV. Our CGC+NRQCD computation provides a better description of data for $p_T leq 15$ GeV relative to extant next-to-leading (NLO) calculations within the collinear factorization framework. These results suggest that higher order computations in the CGC+NRQCD framework have the potential to greatly improve the accuracy of extracted values of the NRQCD universal long distance matrix elements.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
