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.
124703371
FEL ACTIVITIES IN INDIA
We are building a Compact Ultrafast TErahertz FreeElectron Laser (CUTE-FEL), designed to lase from 50 – 100 μm. The FEL will be driven by a 10-15 MeV electron beam from a Plane-Wave Transformer (PWT) linac. The undulator is a 5 cm period, 2.5 m long PPM planar undulator. We present details of the FEL design and the present status of activities. We also present very preliminary plans for a short-wavelength SASE FEL in India.
210000596
ANGULAR DISTRIBUTIONS IN PREEQUILIBRIUM REACTIONS
120804867
Resonance spectroscopy of $sup 30$Si nucleus in the excitation energy range 14.27 to 15.02 MeV
Absolute differential cross sections for the elastic scattering of $alpha$ particles from $sup 26$Mg have been measured as a function of bombarding energy between 4.18 and 5.14 MeV at angles corresponding to the c.m. angles 90degree, 125degree, 141degree, and 167degree. The data have been analyzed using the multilevel multichannel expression of R matrix theory modified to replace the background hard sphere phase shifts by complex optical model phase shifts. These phase shifts have been obtained by fitting the averaged cross section with the optical model. This modification has resulted in reasonably good fits to excitation functions both in magnitude and shape. Twelve levels in the compound nucleus $sup 30$Si have been identified and their spins, parities, and widths have been determined. The possibility of the 0$sup +$ levels being fragmented components of a quartet parent state has been discussed. (AIP)
122218899
A new macroscopic-microscopic description of the double-humped fission barriers
The new mass relation based on the generalised Hugenholtz-Van Hove theorem has been used to obtain a relation for the fission barriers of three nuclei. This relation has been found satisfactory to describe the data. Further a general expression has been given describing satisfactorily the inner barrier height, the second minimum and the second barrier height for all actinides with an rms deviation of 0.32, 0.32 and 0.33 MeV respectively. The estimated shell energies agree reasonably well with those of Brack et al. In addition the barriers for thorium isotopes have been described well.
122432461
Background phase shift in R-matrix theory
It has been shown recently by Cugnon in his generalized version of the R- matrix theory that the hard sphere phase shift used in the standard R-matrix theory is arbitrary and can be replaced, in general, by any other phase shift. In the present paper similar results have been derived in a straightforward manner, within the framework of the standard R-matrix theory, from the usual division of R matrix into a background matrix R$sub 0$ plus a matrix R' containing pole terms and further constraining R$sub 0$ to be a diagonal matrix. Thus Cugnon's theory and the standard R-matrix theory lead to algebraically equivalent results. An expression for the renormalization factor for the reduced width has also been given in terms of the new phase shift and the hard sphere phase shift. (AIP)
10011120
Bc spectroscopy in a quantum-chromodynamic potential model.
We have investigated {ital B}{sub {ital c}} spectroscopy with the use of a quantum-chromodynamic potential model which was recently used by us for the light-heavy quarkonia. We give our predictions for the energy levels and the {ital E}1 transition widths. We also find, rather surprisingly, that although {ital B}{sub {ital c}} is not a light-heavy system, the heavy quark effective theory with the inclusion of the {ital m}{sub {ital b}}{sup -}{sup 1} and {ital m}{sub {ital b}}{sup -}{sup 1}ln{ital m}{sub {ital b}} corrections is as successful for {ital B}{sub {ital c}} as it is for {ital B} and {ital B}{sub {ital s}}. {copyright} {ital 1995 The American Physical Society.}
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.
40514876
Hadronic correlation functions in the QCD plasma phase.
We present results for static hadronic correlation functions in the high-temperature phase of QCD with four flavors of dynamical quarks. We confirm chiral-symmetry restoration through the degeneracies of the spectrum of screening lengths. We also find that the screening lengths for the {rho} and {ital N} channels at {ital T}{approx gt}1.2{ital T}{sub {ital c}} are close to that in a free quark gas.
7265145
Quark mixing and CP violation.
In view of the experimental indications that the top-quark mass may exceed the upper bound predicted by the Fritzsch ansatz for the quark mass matrices, we follow a phenomenological approach to find a modified form of the mass matrices to deal with quark mixing and {ital CP} violation in electroweak interactions. The essential feature of our mass matrices is that the diagonal elements corresponding to the light quarks {ital u}, {ital d}, and {ital s} are vanishingly small, while those corresponding to the heavy quarks {ital c}, {ital b}, and {ital t} are approximately equal to the observed values of their masses. By comparing our theoretical results for the Kobayashi-Maskawa mixing matrix elements with the experimental data, we obtain for the top-quark mass and the {ital CP}-violating phase the values {ital m}{sub {ital t}}{sup phys}{le}170 GeV and 91{degree}{le}{delta}{le}105{degree}.
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 .