Nuclear effects in massive lepton pair production

Precise measurements of nuclear effects in the production of massive lepton pairs from heavy targets by pion and proton beams would extend knowledge of the nuclear dependence of antiquark and quark structure functions of nucleons into important intervals of the fractional longitudinal momentum variable x_Bj not easily accessible in deep inelastic scattering. Isolating nuclear dependence is also essential before definite conclusions can be drawn on the behavior of the pion structure function and on the magnitude and kinematic variation of the perturbative QCD K-factor obtained from heavy target data.     

Quantum chromodynamic rescattering effects off nuclear targets

We discuss hard scattering processes off nuclear targets. Important multiple scattering corrections to massive dilepton production are evaluated.     

Nuclear effects in lepton-pair production in hadron-nucleus collisions

The results of experimental investigations of Drell-Yan dimuon production in pBe and pW collisions at an energy of 800 GeV on a fixed target are analyzed. The ratios of the inclusive differential cross sections for lepton-pair production are calculated. It is shown that allowance for the effect of multiple soft rescattering of a projectile-hadron quark inside the target nucleus improves agreement between theoretical and experimental results.     

Photon radiation and dilepton production induced by rescattering in strong interacting medium

Using the opacity expansion technique we investigate the photon radiation and dilepton production induced by multiple rescattering as an energetic parton jet passing through the strong interacting medium. The real photon radiation and dilepton invariant-mass spectra of the bremsstrahlung contribution from an energetic quark jet are presented. The leading contribution of total energy loss by photon emission in the medium of a high energetic quark jet is found to be proportional to the jet energy and has a linear dependence on the thickness of the nuclear target. The rescattering contribution to the dilepton production is important only when the pair has a small invariant mass and the jet has relatively low energy. The contribution fraction of the dilepton induced by rescattering in medium is found to be nearly a constant when the ratio of the jet energy to Debye screening mass E/μ is large.     

Target rescattering corrections to heavy flavour production off nuclei in the projectile fragmentation region

It is shown that at high energies secondary interactions of a produced particle with the nuclear target lead to shadowing, which is described by essentially the same formulas that follow from the low energy picture based on sequential interactions with target nucleons. No finite formation time effects can be seen.     

Nuclear effects on open charm production in p+A reactions

We calculate and resum the nuclear enhanced power corrections from the final state partonic scattering in nuclear matter to open charm production and correlations. In p+A reactions, we find that single and double inclusive D mesons can be suppressed as much as the neutral pions from the dynamical high twist shadowing. Effects of initial state energy loss in p+A collisions are also investigated and may lead to significantly weaker transverse momentum dependence of the nuclear suppression.     

Modified dihadron fragmentation functions in hot and nuclear matter

Medium modification of dihadron fragmentation functions due to gluon bremsstrahlung induced by multiple partonic scattering is studied in both deep-inelastic scattering (DIS) off large nuclei and high-energy heavy-ion collisions within the same framework of twist expansion. The modification for dihadrons is found to closely follow that for single hadrons, leading to a weak nuclear suppression of their ratios in DIS experiments. A mild enhancement of the near-side correlation of two high transverse momentum hadrons with increasing centrality is found in heavy-ion collisions due to trigger bias and the rise in parton energy loss with centrality. Successful comparisons between theory and experiment for multihadron observables in both confining and deconfined media offer comprehensive evidence for partonic energy loss as the mechanism of jet modification in dense matter.     

Approximation of jet axis in rapidity separated dihadron correlations

The PHENIX experiment has observed particle production asymmetries in transversely polarized proton collisons. This talk presents a novel approach for separating the final-state and initial-state components of the observed asymmetries using the existing PHENIX detector.     

Nuclear effects in multiparticle production in 800 GeV and 400 GeV proton-nucleus interactions

We study nuclear effects in multiparticle production in proton-emulsion nuclei interactions at 800 GeV and 400 GeV. The observed pseudorapidity distributions are compared with the predictions of a simple quark model. The predicted dependence of the ratio of the normalised multiplicity distribution of the produced shower particles in hadron-nucleus (hA) to hadron-hadron (hh) interactions on the mean number of inelastic collisions in the central region is in good agreement with the experimental data.     

Molecular dynamics driven by ultrashort laser pulses: Interference effects due to rescattering

A time-dependent Schrödinger equation is integrated numerically to investigate the dynamics of a model molecular system driven by a high-intensity ultrashort laser pulse. Two-dimensional photoelectron momentum distributions are analyzed. Highly nonmonotonic electron angular distributions are obtained that cannot be explained by diffraction in the double-well potential of a molecular ion. The nonmonotonicity is also demonstrated for atomic ionization and is attributed to the interference that occurs between components of an electron wave packet after its rescattering from the parent ion. An analytical model explaining the observed effects is developed.     

Photoproduction and rescattering of polarized hyperons in deuterium

Excited states of hadrons are essential for understanding confinement and non-perturbative QCD. Constituent quark models are successful in describing the first excited nucleon (N ^*) states in each partial wave, but predict more states than have been observed experimentally. Diquark correlations have been suggested as one explanation for these “missing” states. Recent advances in both theory (coupled-channels calculations) and experiment (high-statistics polarization measurements) offer new tools for resolving this question. The g13 experiment at Jefferson Lab, completed in June 2007, forms an important part of this effort. It used linearly and circularly polarized photons and a deuteron target to study N ^* states produced on the neutron, primarily through their decays into kaons and hyperons. The self-analyzing property of the Λ is ideally suited for this purpose. The general nature and exceptional size of the data set will, however, produce a wide range of results, including opening a new window on the study of hyperon-nucleon interactions through rescattering processes.     

Drell-Yan production of massive muon pairs

Cross-sections for Drell-Yan production of massive muon pairs by incident π^±, K^±, p and $\text{p}$ on an isoscalar, nuclear target are calculated.     

Nuclear effects in neutrino induced coherent pion production at K2K and MiniBooNE

The coherent pion production induced by neutrinos in nuclei is studied using a delta hole model in the local density approximation taking into account the renormalization of Delta properties in a nuclear medium. The pion absorption effects are included in an eikonal approximation. These effects give a large reduction in the total cross section. The numerical results for the total cross section are found to be consistent with recent experimental results from the K2K and MiniBooNE Collaborations and other older experiments in the intermediate energy region.     

Investigation of the rescattering effect in D decay

With two-body unitarity equations, we demonstrate the relation between the data of Dalitz analysis of a D⁺ → K^-π⁺π⁺ decay experiment and that of Kπ scattering, and point out that there might be some underestimated ambiguity in the existing data sets, if the I=1/2 component of the Kπ system is dominant in this decay process. It is suggested that the unitarity constraints should be built in to deal with the raw data to obtain an improved result from the Dalitz analysis.     

System-size scan of dihadron azimuthal correlations in ultra-relativistic heavy ion collisions

System-size dependence of dihadron azimuthal correlations in ultra-relativistic heavy ion collision is simulated by a multi-phase transport model. The structure of correlation functions and yields of associated particles show clear participant path-length dependences in collision systems with a partonic phase. The splitting parameter and root-mean-square width of away-side correlation functions increase with collision system size from ¹⁴N + ¹⁴N to ¹⁹⁷Au + ¹⁹⁷Au collisions. The double-peak structure of away-side correlation functions can only be formed in sufficient “large” collision systems under partonic phase. The contrast between the results with partonic phase and with hadron gas could suggest some hints to study onset of confinement.     

Nuclear effects in atomic transitions

Atomic electrons are sensitive to the properties of the nucleus they are bound to, such as nuclear mass, charge distribution, spin, magnetisation distribution, or even excited level scheme. These nuclear parameters are reflected in the atomic transition energies. A very precise determination of atomic spectra may thus reveal information about the nucleus, otherwise hardly accessible via nuclear physics experiments. This work reviews theoretical and experimental aspects of the nuclear effects that can be identified in atomic structure data. An introduction to the theory of isotope shifts and hyperfine splitting of atomic spectra is given, together with an overview of the typical experimental techniques used in high-precision atomic spectroscopy. More exotic effects at the borderline between atomic and nuclear physics, such as parity violation in atomic transitions due to the weak interaction, or nuclear polarisation and nuclear excitation by electron capture, are also addressed.     

Nuclear quantum effects in water

A path-integral Car-Parrinello molecular dynamics simulation of liquid water and ice is performed. It is found that the inclusion of nuclear quantum effects systematically improves the agreement of first-principles simulations of liquid water with experiment. In addition, the proton momentum distribution is computed utilizing a recently developed open path-integral molecular dynamics methodology. It is shown that these results are in good agreement with experimental data.