We evaluate the cross sections for the production of vector mesons in exclusive ultraperipheral proton–ion collisions at LHC. We find that the rates are high enough to study the energy and momentum ...transfer dependence of vector meson (ρ,ϕ, J/ψ, ϒ) photoproduction in γp scattering in a wide energy range. This would extend the measurements which were performed at HERA providing new information about interplay of soft and hard physics in diffraction. Also, we calculate the contributions to the vector meson yield due to production of vector mesons off nuclear target by photons emitted by proton. We find, that at least in the case of ϒ production it is feasible to observe simultaneously both these processes. Such measurements would increase the precision with which the A-dependence of exclusive onium production can be determined. This would also enable one to estimate the amount of nuclear shadowing of generalized gluon distributions at much smaller x than that is possible in AA collisions and to measure the cross sections for photoproduction processes in a significantly wider energy range than that achieved in experiments with fixed nuclear targets. We also present the cross section for vector meson production in pA collisions at RHIC. In addition, we consider production of vector mesons off protons with large rapidity gaps and large t. These processes probe small x dynamics of the elastic interaction of small dipoles at high energies and large but finite t, that is in the kinematics where DGLAP evolution is strongly suppressed. We estimate that this process could be studied at LHC up to W∼1 TeV with detectors which will be available at LHC.
We present predictions for the cross sections of the coherent and incoherent
$J/\psi$ photoproduction in ultra-peripheral collisions at RHIC and at the LHC
calculated for different classes of events ...depending on the presence of
neutrons emitted by colliding nuclei. Since strong nucleus-nucleus interactions
in UPCs are suppressed, it is usually assumed that neutrons at forward
rapidities originate mainly from the electromagnetic dissociation of colliding
nuclei caused by additional photon exchanges. This is a reasonable assumption
for the coherent photoproduction where the state of the target nucleus remains
intact. We consider additional sources of neutrons in the incoherent
quasielastic and nucleon dissociative $J/\psi$ photoproduction and show that
these processes significantly change probabilities of neutron emission compared
to calculations when only neutrons from electromagnetic dissociation of nuclei
are considered. Such studies should allow one to explore the dynamics of
nuclear shadowing in the incoherent $J/\psi$ photoproduction down to $x \sim
10^{-5}$.
Recently E-665 reported the first measurement of soft (En≤10 MeV) neutron production in deep inelastic scattering (DIS) off nuclei. We report the first theoretical analysis of the data. We find that ...the observed cross section can be quantitatively explained as due to the final state interactions (FSI) of low energy nucleons (EN∼ 200–400 MeV) produced in the elementary μN interactions. We argue that the data indicate strong a suppression of the FSI's of fast partons (hadrons) in DIS at high energies, and that studies of the soft neutron production would provide a new sensitive probe of the dynamics of FSI's in DIS both at fixed target energies and at the HERA eA collider.
In this Letter, we consider strong and electromagnetic (ultraperipheral) mechanisms in proton-nucleus coherent diffraction at the CERN Large Hadron Collider. We explicitly demonstrate the dominance ...of the latter and explain the CMS data on the forward rapidity gap distribution in \(pPb\) collisions at \(\sqrt{s_{NN}}=8.16\) TeV. In particular, we provide simple estimates, which give a good, semi-quantitative description of both magnitude and shape of the \(\Delta \eta^F\) distribution in the Pomeron-proton topology. We also make predictions for the proton-oxygen run.
Inclusive transverse momentum spectra of primary charged particles in Pb-Pb collisions at inline image have been measured by the ALICE Collaboration at the LHC. The data are presented for central and ...peripheral collisions, corresponding to 0-5% and 70-80% of the hadronic Pb-Pb cross section. The measured charged particle spectra in
The multiplicity and pseudorapidity distributions of inclusive photons have been measured at forward rapidities ( ) in proton-proton collisions at three center-of-mass energies, Formula omitted 0.9, ...2.76 and 7 TeV using the ALICE detector. It is observed that the increase in the average photon multiplicity as a function of beam energy is compatible with both a logarithmic and a power-law dependence. The relative increase in average photon multiplicity produced in inelastic pp collisions at 2.76 and 7 TeV center-of-mass energies with respect to 0.9 TeV are 37.2 Formula omitted 0.3 % (stat) 8.8 % (sys) and 61.2 Formula omitted 0.3 % (stat) 7.6 % (sys), respectively. The photon multiplicity distributions for all center-of-mass energies are well described by negative binomial distributions. The multiplicity distributions are also presented in terms of KNO variables. The results are compared to model predictions, which are found in general to underestimate the data at large photon multiplicities, in particular at the highest center-of-mass energy. Limiting fragmentation behavior of photons has been explored with the data, but is not observed in the measured pseudorapidity range.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image) The production of the strange and double-strange baryon resonances (..., ...) has been measured at mid-rapidity (... ...) ...in proton-proton collisions at ... ... 7 TeV with the ALICE detector at the LHC. Transverse momentum spectra for inelastic collisions are compared to QCD-inspired models, which in general underpredict the data. A search for the ... pentaquark, decaying in the ... channel, has been carried out but no evidence is seen.
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