Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userExclusive J/{psi} production in ultraperipheral collisions at the LHC: constrains on the gluon distributions in the proton and nuclei
156
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Using the framework of collinear factorization in perturbative QCD (pQCD), we analyze the recent data of the LHCb and ALICE collaborations on exclusive photoproduction of J/{psi} in ultraperipheral pp and AA collisions, respectively. We demonstrate that the simultaneous analysis of the proton and Pb data allows us to reduce the ambiguity of the pQCD description of the $gamma p to J/psi p$ and $gamma A to J/psi p$ cross sections and, hence, to place additional constraints on the gluon distributions in the nucleon and nuclei at small x. We also make predictions for the cross section of coherent exclusive photoproduction of J/{psi} in nucleus-nucleus ultraperipheral collisions accompanied by the electromagnetic excitation of nuclei and the subsequent neutron emission.
rate research
Read More
In this paper we perform a systematic study of the exclusive dilepton production by $gamma gamma$ interactions in $PbPb$ collisions at the LHC Run 2 energies considering different levels of precision for the treatment of the absorptive corrections and for the nuclear form factor. The rapidity and invariant mass distributions are estimated taking into account the experimental cutoffs and a comparison with the recent ALICE and ATLAS data for the $e^+ e^-$ and $mu^+ mu^-$ production is presented.
In this letter we complement previous studies on exclusive vector meson photoproduction in hadronic collisions presenting a comprehensive analysis of the $t$ - spectrum measured in exclusive $rho$ and $J/Psi$ photoproduction in $pA$ collisions at the LHC. We compute the differential cross sections considering two phenomenological models for the gluon saturation effects and present predictions for $pPb$ and $pCa$ collisions. Moreover, we compare our predictions with the recent preliminary CMS data for the exclusive $rho$ photoproduction. We demonstrate that the gluon saturation models are able to describe the CMS data at small - $t$. On the other hand, the models underestimate the few data point at large -- $t$. Our results indicate that future measurements of the large -- $t$ region can be useful to probe the presence or absence of a dip in the $t$ -- spectrum and discriminate between the different approaches to the gluon saturation effects.
We compute the leading order (LO) $qgto q gamma$ and next-to-leading order (NLO) $ggto q{bar q} gamma$ contributions to inclusive photon production in proton-proton (p+p) collisions at the LHC. These channels provide the dominant contribution at LO and NLO for photon transverse momenta $k_{gammaperp}$ corresponding to momentum fractions of $xleq 0.01$ in the colliding protons. Our computations, performed in the dilute-dense framework of the Color Glass Condensate effective field theory (CGC EFT), show that the NLO contribution dominates at small-$x$ because it is sensitive to $k_perp$-dependent unintegrated gluon distributions in both of the protons. We predict a maximal $10%$ modification of the cross section at low $k_{gammaperp}$ as a direct consequence of the violation of $k_perp$-factorization. The coherence effects responsible for this modification are enhanced in nuclei and can be identified from inclusive photon measurements in proton-nucleus collisions. We provide numerical results for the isolated inclusive photon cross section for $k_{gammaperp}leq 20$ GeV in p+p collisions that can be tested in the future at the LHC.
We study inclusive heavy quarkonium production with definite polarizations in polarized proton-proton collisions using the non-relativistic QCD color-octet mechanism. We present results for rapidity distributions of cross sections and spin asymmetries for the production of J/psi and psi with specific polarizations in polarized p-p collisions at sqrt s = 200 GeV and 500 GeV at the RHIC within the PHENIX detector acceptance range.
Based on accurate calculations of the flux of equivalent photons of the proton and heavy nuclei and the pQCD framework for the gluon distribution in the proton and nuclei, we analyze the rapidity and momentum transfer distributions of coherent $J/psi$ photoproduction in ultraperipheral proton-Pb collisions at the LHC. We demonstrate that unlike the case of proton-proton UPCs marred by certain theoretical uncertainties and experimental limitations, after a cut excluding the region of small momentum transfers, ultraperipheral proton-Pb collisions offer a clean way to study the gluon distribution in the proton down to $x approx 10^{-5}$. Our analysis of the momentum transfer distributions shows that an interplay of $J/psi$ production by low-energy photons on the nucleus and by high-energy photons on the proton in proton-Pb UPCs can result in some excess of events at small $p_t$ in a definite region of the rapidity y.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
