21268625
Search for signals from Cygnus X-3 at energies above 50 TeV.
Upper limits for the time-averaged flux of air showers from the direction of Cygnus X-3 during the calendar period 2 April 1986 to 3 May 1987 are found to be 1.5 x 10/sup -13/ cm/sup -2/ sec/sup -1/ for all events, and 7.6 x 10/sup -14/ cm/sup -2/ sec/sup -1/ for events with no observed muons in a 44-m/sup 2/ muon detector. These are integral fluxes above 50 TeV on the assumption of an E/sup -1/ primary spectrum. A possible observation of a short-term signal from Cygnus X-3, with an anomalous muon content, phase correlated with the 4.8-h orbital period, with an integral flux above 50 TeV of (8.2 +- 2.0) x 10/sup -13/ cm/sup -2/ sec/sup -1/ is also reported.
33623649
Simple relationships in the eikonal model of the energy flow in ultrarelativistic heavy ion collisions.
The eikonal model has been formulated in terms of the participant and spectator probabilities. It has been used to relate the number of collisions, the numbers of participants from both the projectile and the target, and the energy in the zero degree detector. It is found by comparison with the recent data that the transverse energy or the charged particle multiplicity is directly proportional to the total number of participant nucleons rather than to the number of collisions.
2504344
Coulomb-modified Glauber model description of heavy-ion reaction cross sections.
A simple closed-form analytic expression for the heavy-ion reaction cross section, involving nuclear densities of colliding ions and the nucleon-nucleon cross section, has been obtained within the framework of the Glauber model modified for the Coulomb field effect. Reaction cross sections for a large number of heavy-ion systems have been predicted reasonably well over an energy range beginning with the Coulomb barrier to a few GeV/nucleon.
7081152
Trajectory modifications in the Glauber model for heavy ions.
Expressions are presented for the modification due to the nuclear potential apart from the Coulomb potential both for the eikonal and the noneikonal trajectories. Calculations for heavy ion total reaction cross sections are performed using these expressions. Results are given for several systems. It is found that the expression used by Cha leads to unrealistic values for the distance of closest approach at small impact parameters at low energies and therefore lead to inaccurate values of the total reaction cross section. The exactly calculated distance of closest approach leads to improved results both for the eikonal and the noneikonal trajectories.
37920331
Systematics in the volume integrals of the imaginary part of the light ion optical potentials.
A systematic analysis of the imaginary part of the light projectile (A/sub p/ = 1--6) phenomenological optical potentials has been carried out. As a result of this analysis a global formula has been found which describes successfully the volume integrals of the imaginary potential in terms of the projectile energy in the range 0--50 MeV/nucleon and the target and the projectile mass numbers.
39485818
Nucleus-nucleus potential from fusion and elastic scattering.
An analytical expression for the calculation of the nucleus-nucleus potential has been derived from an empirical formula which describes the fusion excitation function. The nucleus-nucleus potentials calculated for the projectiles /sup 6/Li, /sup 9/Be, and /sup 12/C in the interaction region --3--6.5 fm by the above procedure agree remarkably well with the real part of the respective optical potentials determined from the analysis of elastic scattering data which exhibit the ''rainbow'' phenomenon.
43411058
Semirelativistic potential model for heavy quarkonia.
The c-italicc-bar, b-italicb-bar, and t-italic t-italic-bar spectra are investigated with the use of a semirelativistic potential model described in an earlier paper. Results for the energy levels, leptonic widths, and E-italic1 transition widths are compared with the experimental data for c-italicc-bar and b-italicb-bar and predicted for t-italic t-italic-bar. We also find that the quark-antiquark interaction can best be described by a quasistatic rather than a momentum-dependent potential, and propose a theoretical justification for this surprising conclusion.
8554087
An episode of ultrahigh energy radiation from the gamma -ray source Geminga: GRAPES I observations at Ooty during 1984-1987.
A study of showers arriving from the direction of the γ-ray source Geminga (1E0630 + 178) has shown evidence for emission of ultrahigh energy radiation during the one week interval October 10-16, 1986. 83 showers were observed in the source bin as against an expected background of 44.1. The probability of observing this excess based on Monte Carlo simulations is less than 10 −4 . The flux observed during this period (1.00±0.24)×10 −11 cm −2 s −1 at energies ≥10 14 eV corresponds to a time-averaged luminosity of 6×10 32 erg s −1
27966894
Fermions obstruct dimensional reduction in hot QCD
We have studied, for the first time, screening masses obtained from glueball-like correlators in quantum chromodynamics with four light dynamical flavors of quarks in the temperature range 1. 5T(c)</=T</=3T(c), where T(c) is the temperature at which the chiral transition occurs. We have also studied pionlike and sigmalike screening masses and found that they are degenerate in the entire range of T. These obstruct perturbative dimensional reduction since the lowest glueball screening mass is heavier than them. Extrapolation of our results suggests that this obstruction may affect the entire range of temperature expected to be reached even at the Large Hadron Collider.
6552264
Nonsingular potential model for heavy quarkonia.
A nonsingular potential model for heavy quarkonia is described which does not require recourse to an illegitimate perturbative treatment for the investigation of quarkonium spectra. Our overall results for the energy levels, the leptonic widths, and the E1 transition widths are in very good agreement with the experimental data for bb-bar and they are reasonably good for cc-bar. We also find that the confining part of the quarkonium potential is scalar-vector exchange rather than the currently favored scalar exchange.
12293063
Detection of ultrahigh-energy radiation from Scorpius X-1: Ooty observations during 1984-1987.
A detailed study of showers arriving from the direction of Scorpius X-1 has shown strong evidence for emission of ultrahigh-energy radiation from Scorpius X-1 during the period 4 March-2 May 1986. 178 showers were observed in the source bin againat an expected background of 122.9. The chance probability for observing this excess has been estimated from simulations to be less than 10 -3 . The flux observed during this period was (6.4±1.6)×10 -12 cm -2 s -1 at energies >2.5×10 14 eV, corresponding to a luminosity of 2×10 35 ergs s -1 .