Table of contents

We conduct a review of experimental results on ultra-high energy cosmic rays (UHECRs) including measurements of the features of the spectrum, the composition of the primary particle flux and the search for anisotropy in event arrival direction. We find that while there is a general consensus on the features in the spectrum—the Second Knee, the Ankle and (to a lesser extent) the GZK Cutoff—there is little consensus on the composition of the primaries that accompany these features. This lack of consensus on the composition makes interpretation of the agreed upon features problematic. There is also little direct evidence about potential sources of UHECRs, as early reports of arrival-direction anisotropies have not been confirmed in independent measurements.

We reconsider parity violation experiments in atomic hydrogen and deuterium in the light of existing tests of the Electroweak interactions, and assess whether new experiments, using improved experimental techniques, could make useful contributions to testing the Standard Model (SM). We find that, if parity experiments in hydrogen can be done, they remain highly desirable because there is negligible atomic-physics uncertainty, and low-energy tests of weak neutral current interactions are needed to probe for new physics beyond the SM. Of particular interest would be a measurement of the nuclear spin independent coupling C_1D for the deuteron at a combined error (theory + experiment) of 0.3%. This would provide a factor of 3 improvement to the precision on sin²θ_W at very low momentum transfer provided by heavy atom atomic parity violation (APV) experiments. Also, experiments in H and D could provide precise measurements of three other electron–nucleon, weak–neutral–current coupling constants: C_1p, C_2p and C_2D, which have not been accurately determined to date. Analysis of a generic APV experiment in deuterium indicates that a 0.3% measurement of C_1D requires development of a slow (77 K) metastable beam of ≈5 × 10¹⁴ D(2S) s⁻¹ per hyperfine component. The advent of UV radiation from free electron laser (FEL) technology could allow production of such a beam.

We investigate in this paper the impact of some up-to-date hadronic interaction models on the calculation of the atmospheric muon flux. Calculations are carried out with the air shower simulation code CORSIKA in combination with the hadronic interaction models FLUKA and UrQMD below 80 GeV/nucleon and NEXUS elsewhere. We also examine the atmospheric effects using two different parametrizations of the US standard atmosphere. The cosmic ray spectra of protons and α particles, the only primary particles considered here, are taken according to the force field model which describes properly solar modulation. Numerical results are compared with the BESS-2001 experimental data.

Correlated trial wavefunctions built as the product of a correlation factor times a model wavefunction are obtained for the ²⁰Ne, ²⁴Mg, ²⁸Si, ³²S, ³⁶Ar and ⁴⁰Ca nuclei. The correlation factor includes both central Jastrow and linear state dependent correlations. For ²⁰Ne, ²⁴Mg and ²⁸Si we have considered two different approaches, one based on the SU(3) deformed model and the other on a multi-cluster model, while for ³²S, ³⁶Ar and ⁴⁰Ca only the first model has been considered. A systematic analysis of the competition between the different correlation mechanisms included in the trial wavefunction on the ground state and binding energies of some members of its rotational band is carried out. One- and two-body radial densities have also been obtained. All the calculations have been performed by means of the variational Monte Carlo method.

Wakes created by a parton moving through a static and infinitely extended quark–gluon plasma are considered. In contrast to former investigations, collisions within the quark–gluon plasma are taken into account using a transport theoretical approach (Boltzmann equation) with a Bhatnagar–Gross–Krook collision term. Within this model, it is shown that the wake structure changes significantly compared to the collisionless case.

We extend recent studies of the effects of quark–gluon vertex dressing upon the solutions of the Dyson–Schwinger equation for the quark propagator. A momentum delta function is used to represent the dominant infrared strength of the effective gluon propagator so that the resulting integral equations become algebraic. The quark–gluon vertex is constructed from the complete set of diagrams involving only two-point gluon lines. The additional diagrams, including those with crossed gluon lines, are shown to make an important contribution to the DSE solutions for the quark propagator, because of their large color factors and the rapid growth in their number.

This paper deals with fixed target AGS and SPS data of beam energies 14.5 and 200 A GeV respectively. A detailed study on chaos in the nuclear fragmentation process of ²⁸Si–AgBr interactions at 14.5 A GeV and ³²S–AgBr interactions at 200 A GeV has been performed using a new parameter, the entropy index. The analysis provides new data on the evidence of the erratic behavior of the target fragments signifying chaotic target fragmentation and also quantify the measure for chaos in high and ultra-high energy heavy-ion interactions. Further, it is also observed that the target fragmentation process becomes less chaotic with the increase of average multiplicities of the final states.

The isospin effect and isoscaling behavior in projectile fragmentation have been systematically investigated by a modified statistical abrasion–ablation (SAA) model. The normalized peak differences and reduced isoscaling parameters are found to decrease with (Z_proj − Z)/Z_proj or the excitation energy per nucleon and have no significant dependence on the size of reaction systems. Assuming a Fermi-gas behavior, the excitation energy dependence of the symmetry energy coefficients is tentatively extracted from α and β which looks consistent with the experimental data. It is pointed out that the reduced isoscaling parameters can be used as an observable to study excitation extent of system and asymmetric nuclear equation of state in heavy ion collisions.

In this paper, we calculate the scalar form-factors f_ππ(Q²) and f_KK(Q²) in the framework of the light-cone QCD sum rules approach. The numerical value of f_ππ(Q²) changes quickly with the variation of Q² near zero momentum transfer, while f_KK(Q²) has a rather good behavior at small momentum transfer. The value f_KK(0) = 2.21^+0.35_−0.19 GeV is compatible with the result from the leading order chiral perturbation theory. At large momentum transfer with Q² > 6 GeV², the form-factor f_ππ(Q²) takes up the asymptotic behavior approximately, while f_KK(Q²) decreases more quickly than .

Both BaBar and Belle have found evidence for a non-zero width difference in the D⁰– system. Although there is no direct experimental evidence for CP-violation in D mixing (yet), we show that the width difference y ∼ ΔΓ is sensitive to the CP-odd phase in D mixing, which, if significantly different from zero, would be an unambiguous signal of new physics.

Coulomb excitation is a standard method used to extract quadrupole excitation strengths of even–even nuclei. In typical analyzes the reaction is assumed to be one step, Coulomb only, and is treated within a semi-classical model. In this work, fully quantal coupled-channel calculations are performed for three test cases in order to determine the importance of multi-step effects, nuclear contributions, feeding from other states and corrections to the semi-classical approximation. We study the excitation of ³⁰S, ⁵⁸Ni and ⁷⁸Kr on ¹⁹⁷Au at ≈50 A MeV. We find that nuclear effects may contribute more than 10% and that feeding contributions can be larger than 15%. These corrections do not alter significantly the published B(E2) values; however, an additional theoretical error of up to 13% should be added to the experimental uncertainty if the semi-classical model is used. This theoretical error is reduced to less than 7% when performing a quantal coupled-channel analysis.

Implicit regularization (IR) has been shown as a useful momentum space tool for perturbative calculations in dimension-specific theories, such as chiral gauge, topological and supersymmetric quantum field theoretical models at one-loop level. In this paper, we aim at generalizing systematically IR to be applicable beyond one-loop order. We use a scalar field theory as an example and pave the way for the extension to quantum field theories which are richer from the symmetry content viewpoint. Particularly, we show that a natural (minimal) renormalization scheme emerges, in which the infinities displayed in terms of integrals in one internal momentum are subtracted, whereas infrared and ultraviolet modes do not mix and therefore leave no room for ambiguities. A systematic cancellation of the infrared divergences at any loop order takes place between the ultraviolet finite and divergent parts of the amplitude for non-exceptional momenta leaving, as a by-product, a renormalization group scale.