Nuclear structure at high excitation energies

The present paper deals with the investigation of hot GDR and quadrupole shapes of ^106,120Sn isotopes as a function of temperature and spin utilizing cranked quadrupole-quadrupole model interaction hamlitonian in the linear response theory and static path approximation to the grand canonical partition function.     

Particle-to-fission competition at high excitation energies

For application in statistical model evaporation codes, a model is presented which describes the experimental observation of multifold particle emission prior to fission, even from very fissile highly excited composite nuclei. This model is based upon the assumption that collective motion of many nucleons towards the scission point is slow compared to evaporation times for single nucleons. The relative times required for particle evaporation and collective motion towards the scission point are estimated, using as a first-order approximation, the frequencies of the lowest modes of particle vibration and low-frequency β-quadrupole vibration, respectively. Comparisons with data for the systems¹²C+¹⁸²W,⁴⁰Ar+¹⁵⁴Sm,¹⁹F+¹⁸¹Ta, and²⁰Ne+¹⁶⁵Ho show good agreement with the model calculations.     

Analysis of the π± p polarization data at high energies

The results of a phenomenological analysis are compared with the Regge model.     

A new possibility of identifying high-spin states at high excitation energies

A new method of identifying high-spin states at high excitation energies is presented.     

An analysis of charge multiplicity data at high energies

The mode and the median charged multiplicities are both found to exhibit a similar increasing linear dependence on ln Q for pp, π^±p and K^±p interactions in the interval 1 < ln Q < 3(Q = available c.m. energy in GeV). The values obtained are compared to the predictions of the Nova model and the Chew-Pignotti model.     

Thermodynamics at high energies

A new thermodynamics, applicable to cosmic ray showers and high-energy physics, is developed. Although all density expressions are unaltered, their global forms are modified due to the new dependence between the volume and the temperature. This occurs in bound systems where the number of particles, instead of being an increasing function of the temperature, is a decreasing one. That certain global expressions for the entropy turn out to be convex functions of the energy necessitates their reinterpretation as the reduction in entropy caused by the volume-temperature constraint. The continuous distribution for the production of hadrons with energies greater than a given amount is shown to correspond to the fact that discrete particle fluctuations follow Poisson's law.     

Intermittency regions at high energies

We investigate the non-statistical multiplicity fluctuations (intermittency) of hadrons produced in high-energy collisions. Within the framework of the two-mechanism model, we determine the limits of the intermittent regions. We observe that these regions decrease in extent with increasing total energy $\sqrt s$ . In addition, we determine the value of the exponent from the universal scaling law (discovered recently by R. Hwa et al.). The value of this exponent is close to corresponding experimental data.     

Nucleus-nucleus collisions at high energies

Nucleus-nucleus collisions are studied in the framework of an extended Glauber model in which terms higher than the first (optical limit) in the phase shift expansion are considered. These are the so-called eclipse correction terms. The inelastic cross sections and distributions with respect to both the number of interacting nucleons and protons are calculated for various nucleus-nucleus interactions. The results show satisfactory agreement with the available experimental data.     

Elastic pd-scattering at high energies

Elastic pd-scattering at large angles is considered in terms of a virtual pion exchange model. The theoretical results are compared with the experimental data at 1 GeV proton energy.     

Perturbative QCD at high energies

A partial review of QCD at high energies is given. Factorization and the use of the renormalization group equation are emphasized. Topics discussed are the parton model, cut vertices in covariant and axial gauges, μ-pair production, jets, form factors, x → 1 limit of structure fu nctions, wide angle elastic scattering and heavy quarkonium exclusive decays. A discussion of mass and infrared singularities and a discussion of Sudakov effects are also included.     

Nuclear levels in43Sc at low excitation energies

Properties of levels up to 3.5 MeV in⁴³Sc were studied using⁴⁰Ca (α, p)⁴³Sc and⁴⁰Ca(α, pγ)⁴³Sc reactions atE _α =12 MeV. Level energies, branching ratios, mean lifetimes, spins and mixing ratios were obtained for a number of levels. Relevant results are compared with many-particle shell-model predictions.     

Gamma-ray bursts at high and very high energies

Gamma-Ray Bursts (GRBs) are extra-galactic and extremely energetic transient emissions of gamma rays, which are thought to be associated with the death of massive stars or the merger of compact objects in binary systems. Their huge luminosities involve the presence of a newborn stellar-mass black hole emitting a relativistic collimated outflow, which accelerates particles and produces non-thermal emissions from the radio domain to the highest energies. In this article, I review recent progresses in the understanding of GRB jet physics above 100 MeV, based on Fermi observations of bright GRBs. I discuss the physical implications of these observations and their impact on GRB modeling, and I present some prospects for GRB observation at very high energies in the near future.     

Charm photo-and electroproduction at high energies

The differential and total cross sections for the photoproduction of vector D* mesons and for their production in deep-inelastic interactions at the HERA collider are estimated on the basis of a model motivated by perturbative calculations within QCD. The proposed model makes it possible to take into account higher twists in the meson transverse momentum at pT～m _c and to reproduce correctly the dominance of c-quark fragmentation for p _T m _c . The possibility of the hadronization of an octet c $\bar q$ state into a meson is considered, whereby good agreement with experimental data is obtained both for the case of D*-meson photoproduction and for the case of D*-meson formation in a deep-inelastic process.     

Neutral pion photoproduction at high energies

A Regge model with absorptive corrections is employed in a global analysis of the world data on the reactions p p and n n for photon energies from 3 to 18GeV. In this region resonance contributions are expected to be negligible so that the available experimental information on differential cross-sections and single and double polarization observables at - t 2 GeV²allows us to determine the reaction amplitude reliably. The model amplitude is then used to predict observables for photon energies below 3GeV. A detailed comparison with recent data from the CLAS and CB-ELSA Collaborations in that energy region is presented. Furthermore, the prospects for determining the radiative decay width via the Primakoff effect from the reaction p p are explored.     

Pomeron and odderon at high energies

One of the crucial questions which high energy elastic data ought to be able to answer is: is the odderon contribution really necessary? Using a model with mildly energy dependent form factors as input and performing full eikonalization before we compare with the data, the answer that we find from a careful examination of the various options is that the odderon is indeed necessary if: 1) we trust the ISRpp data to be precise enough that their comparison with the collider data onpc \(\bar p\) is meaningful, 2) we demandquantitative (i.e. not justqualitative) agreement between theory and experiment and 3) we account for the large |t| data.     

On charm production at high energies

A number of new huge neutrino telescopes have been built, are being built, and are planned to be built all over the world. With these setups, cosmic neutrinos of high energies can be studied experimentally. Atmospheric neutrinos represent the main backgrounds to such experiments—namely, the atmospheric neutrinos determine how large a setup should be to measure diffuse cosmic neutrino fluxes or what angular resolution of a setup should be in order that searches for pointlike neutrino sources in the sky be successful. The atmospheric-neutrino fluxes are calculated in the present study. At high energies, the atmospheric-neutrino fluxes consist mostly of neutrinos produced in the atmosphere through charmed-particle decays. Three sources of information about charm production are used: (1) data obtained in accelerator experiments, (2) data on cosmicray muons, and (3) predictions of the NLO and QGSM QCD models for the charm-production at energies not available at modern accelerators. The uncertainties in the calculated fluxes of atmospheric neutrinos from charmed-particle decays are estimated to be at a level of 3–5 orders of magnitude.