Fission fragment angular distributions in 16O+181Ta

Time of flight and energy of fission fragments were measured using pulsed beam. Fission fragment mass and energy integrated angular distributions were extracted. Fission fragment anisotropy was explained in the framework of saddle point model.     

Analysis of π-mode Stopband in an Asymmetric Millimeter-Wave Helical Slow-Wave Structure

A simple closed form formula for the estimation of π-mode stopband in an azimuthally asymmetric helical slow-wave structure (SWS) was developed following coupled-mode analysis of multiple reflections of the degenerate space-harmonic modes from the support rod discontinuities. The method incorporates the effects of circuit loss, and accrues the accuracy of 3D electromagnetic analysis by allowing the use of dispersion characteristics obtainable from any standard electromagnetic modeling. The formula is simple and amenable to easy computation, even using a scientific calculator, and without resorting to exhaustive and time-intensive numerical computation, and at the same time, without sacrificing the accuracy in results. The analysis was benchmarked against published results and excellent agreement observed. The analysis was further used for demonstrating the stopband phenomenon for a typical millimeter-wave helical slow-wave structure. Compared to low frequency structures, the stopband phenomenon for a millimeter-wave structure was found to be more pronounced, and an interesting inference was drawn as to how asymmetry induced stopband might be made to advantage in combating π-mode instabilities in a millimeter-wave traveling-wave tube.     

Effective Hamiltonians and Phase Diagrams for Tight-Binding Models

We present rigorous results for several variants of the Hubbard model in the strong-coupling regime. We establish a mathematically controlled perturbation expansion which shows how previously proposed effective interactions are, in fact, leading-order terms of well-defined (volume-independent) unitarily equivalent interactions. In addition, in the very asymmetric (Falicov–Kimball) regime, we are able to apply recently developed phase-diagram technology (quantum Pirogov–Sinai theory) to conclude that the zero-temperature phase diagrams obtained for the leading classical part remain valid, except for thin excluded regions and small deformations, for the full-fledged quantum interaction at zero or low temperature. Moreover, the phase diagram is stable against addition of arbitrary, but sufficiently small further quantum terms that do not break the ground-state symmetries. This generalizes and unifies a number of previous results on the subject; in particular, published results on the zero-temperature phase diagram of the Falikov–Kimball model (with and without magnetic flux) are extended to small temperatures and/or small ionic hopping. We give explicit expressions for the first few orders, in the hopping amplitude, of equivalent interactions, and we describe the resulting phase diagram. Our approach yields algorithms to compute equivalent interactions to arbitrarily high order in the hopping amplitude.     

Slow rotation of a sphere with source at its centre in a viscous fluid

In this note, the problem of a sphere carrying a fluid source at its centre and rotating with slow uniform angular velocity about a diameter is studied. The analysis reveals that only the azimuthal component of velocity exists and is seen that the effect of the source is to decrease it. Also, the couple on the sphere is found to decrease on account of the source.     

Inclusive and exclusive measurements in the projectile breakup of 7Li

The inclusive and exclusive measurements were carried out for ⁷Li projectile breakup on ²⁷Al target at 48 MeV. In the inclusive data we have observed a broad peak around the beam velocity for alphas and tritons. The exclusive data for alpha-triton coincidences show good agreement with the post-form DWBA theory of breakup reactions.     

Quasielastic reactions around the coulomb barrier in 16O+118Sn

Measurement of elastic and quasielastic reaction cross sections were done in ¹⁶O + ¹¹⁸Sn system at two different energies above the barrier. Attempts are being made to understand the results in the framework of coupled reaction channel model.     

Working group report: Collider and flavour physics

The activities of the working group took place under two broad subgroups: Collider Physics subgroup and Flavour Physics subgroup. Reports on some of the projects undertaken are included. Also, some of the leading discussions organized by the working group are summarized.