Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userLeading twist nuclear shadowing phenomena in hard processes with nuclei
138
0
0.0
(
0
)
Authors
L. Frankfurt
Ask ChatGPT about the research
No Arabic abstract
We present and discuss the theory and phenomenology of the leading twist theory of nuclear shadowing which is based on the combination of the generalization of the Gribov-Glauber theory, QCD factorization theorems, and the HERA QCD analysis of diffraction in lepton-proton deep inelastic scattering (DIS). We apply this technique for the analysis of a wide range of hard processes with nuclei---inclusive DIS on deuterons, medium-range and heavy nuclei, coherent and incoherent diffractive DIS with nuclei, and hard diffraction in proton-nucleus scattering---and make predictions for the effect of nuclear shadowing in the corresponding sea quark and gluon parton distributions. We also analyze the role of the leading twist nuclear shadowing in generalized parton distributions in nuclei and in certain characteristics of final states in nuclear DIS. We discuss the limits of applicability of the leading twist approximation for small x scattering off nuclei and the onset of the black disk regime and methods of detecting it. It will be possible to check many of our predictions in the near future in the studies of the ultraperipheral collisions at the Large Hadron Collider (LHC). Further checks will be possible in pA collisions at the LHC and forward hadron production at the Relativistic Heavy Ion Collider (RHIC). Detailed tests will be possible at an Electron-Ion Collider (EIC) in the USA and at the Large Hadron-Electron Collider (LHeC) at CERN.
rate research
Read More
The understanding of the pion structure as described in terms of transverse-momentum dependent parton distribution functions (TMDs) is of importance for the interpretation of currently ongoing Drell-Yan experiments with pion beams. In this work we discuss the description of pion TMDs beyond leading twist in a pion model formulated in the light-front constituent framework. For comparison, we also review and derive new results for pion TMDs in the bag and spectator models.
Absorptive corrections, known to suppress proton-neutron transitions with large fractional momentum $zto1$ in pp collisions, become dramatically strong on a nuclear target, and push the partial cross sections of leading neutron production to the very periphery of the nucleus. The mechanism of $pi$-$a_1$ interference, which successfully explains the observed single-spin asymmetry in polarized $ppto nX$, is extended to collisions of polarized protons with nuclei. Corrected for nuclear effects, it explains the observed single-spin azimuthal asymmetry of neutrons, produced in inelastic events, where the nucleus violently breaks up. The single-spin asymmetry is found to be negative and nearly $A$-independent.
We argue that with an increase of the collision energy, elastic photoproduction of $rho$ mesons on nuclei becomes affected by the significant cross section of photon inelastic diffraction into large masses, which results in the sizable inelastic nuclear shadowing correction to $sigma_{gamma A to rho A}$ and the reduced effective $rho$-nucleon cross section. We take these effects into account by combining the vector meson dominance model, which we upgrade to include the contribution of high-mass fluctuations of the photon according to QCD constraints, and the Gribov-Glauber approximation for nuclear shadowing, where the inelastic nuclear shadowing is included by means of cross section fluctuations. The resulting approach allows us to successfully describe the data on elastic $rho$ photoproduction on nuclei in heavy ion UPCs in the $7 {rm GeV} < W_{gamma p} < 46$ GeV energy range and to predict the value of the cross section of coherent $rho$ photoproduction in Pb-Pb UPCs at $sqrt{s_{NN}}=5.02$ TeV in Run 2 at the LHC, $dsigma_{Pb Pb to rho Pb Pb} (y=0)/dy= 560 pm 25$ mb.
Half-life estimates for neutrinoless double beta decay depend on particle physics models for lepton flavor violation, as well as on nuclear physics models for the structure and transitions of candidate nuclei. Different models considered in the literature can be contrasted - via prospective data - with a standard scenario characterized by light Majorana neutrino exchange and by the quasiparticle random phase approximation, for which the theoretical covariance matrix has been recently estimated. We show that, assuming future half-life data in four promising nuclei (Ge-76, Se-82, Te-130, and Xe-136), the standard scenario can be distinguished from a few nonstandard physics models, while being compatible with alternative state-of-the-art nuclear calculations (at 95% C.L.). Future signals in different nuclei may thus help to discriminate at least some decay mechanisms, without being spoiled by current nuclear uncertainties. Prospects for possible improvements are also discussed.
We study the relevance of experimental data on heavy-flavor [$D^0$, $J/psi$, $Brightarrow J/psi$ and $Upsilon(1S)$ mesons] production in proton-lead collisions at the LHC to improve our knowledge of the gluon-momentum distribution inside heavy nuclei. We observe that the nuclear effects encoded in both most recent global fits of nuclear parton densities at next-to-leading order (nCTEQ15 and EPPS16) provide a good overall description of the LHC data. We interpret this as a hint that these are the dominant ones. In turn, we perform a Bayesian-reweighting analysis for each particle data sample which shows that each of the existing heavy-quark(onium) data set clearly points --with a minimal statistical significance of 7 $sigma$-- to a shadowed gluon distribution at small $x$ in the lead. Moreover, our analysis corroborates the existence of gluon antishadowing. Overall, the inclusion of such heavy-flavor data in a global fit would significantly reduce the uncertainty on the gluon density down to $xsimeq 7times 10^{-6}$ --where no other data exist-- while keeping an agreement with the other data of the global fits. Our study accounts for the factorization-scale uncertainties which dominate for the charm(onium) sector.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
