119175675
Study of transfer reaction channel in $^{12}$C + $^{27}$Al system
The 1p transfer channel in the $^{27}$Al($^{12}$C, $^{11}$B)$^{28}$Si reaction has been studied at E$_{lab}$ = 73, 81 and 85 MeV. The finite range distorted wave Born approximation calculations have been performed using phenomenological optical model potential to analyze the angular distributions for 3 transitions populating the 0.0, 1.78 and 4.62 MeV states of $^{28}$Si and 2 transitions populating the 2.12 and 4.44 MeV states of $^{11}$B via the $^{27}$Al($^{12}$C, $^{11}$B)$^{28}$Si reaction. The spectroscopic strengths as well as spectroscopic factors have been extracted for all the five states. The extracted strength values are compared with shell model calculations.
9833237
Measurement of the damping of the nuclear shell effect in the doubly magic 208Pb region.
The damping of the nuclear shell effect with excitation energy has been measured through an analysis of the neutron spectra following the triton transfer in the (7)Li induced reaction on (205)Tl. The measured neutron spectra demonstrate the expected large shell correction energy for the nuclei in the vicinity of doubly magic (208)Pb and a small value around (184)W. A quantitative extraction of the allowed values of the damping parameter γ, along with those for the asymptotic nuclear level density parameter ã, has been made for the first time.
14314222
A Large area plastic scintillator detector array for fast neutron measurements
Abstract A large area plastic scintillator detector array ( ∼ 1 × 1 m 2 ) has been set up for fast neutron spectroscopy at the BARC-TIFR Pelletron laboratory, Mumbai. The energy, time and position response has been measured for electrons using radioactive sources and for monoenergetic neutrons using the 7 Li ( p , n 1 ) 7 Be * ( 0.429 MeV ) reaction at proton energies between 6.3 and 19 MeV. A Monte Carlo simulation of the energy dependent efficiency of the array for neutron detection is in agreement with the 7 Li ( p , n 1 ) measurements. The array has been used to measure the neutron spectrum, in the energy range of 4–12 MeV, in the reaction C 12 + Nb 93 at E ( C 12 ) = 40 MeV . This is in reasonable agreement with a statistical model calculation.
121681055
Inhomogeneous and intrinsic damping of giant dipole resonance in hot rotating nuclei with A ~ 150
High-energy gamma rays in the range of ~4–28 MeV were measured in the reaction 28Si+124Sn at E(28Si) ~ 185 MeV in coincidence with low-energy gamma ray multiplicities and evaporation residues. The centroid energy and width of the giant dipole resonance were extracted for various multiplicity windows from the statistical model analysis. These extracted widths, along with those from an earlier measurement at E(28Si) ~ 149 MeV, show a discrepancy with the results of a calculation under the thermal shape fluctuation model which describes the inhomogeneous damping of the resonance. An empirical form of the temperature and angular momentum dependence of the width, describing the data at both the beam energies, has been derived. The present results suggest that the contributions from both the inhomogeneous damping and the intrinsic collisional damping processes should be included.
122105491
Charge-current commutator in the framework of analytic regularization
We calculate the charge-current commutator using analytic regularization and show that it is same as that obtained by dimensional regularization on the dimensionality shell.
120865802
High spin spectroscopy and shears mechanism in In 107
High spin states of $^{107}\mathrm{In}$ have been investigated using the reaction $^{94}\mathrm{Mo}$($^{16}\mathrm{O}$,$p2n$)$^{107}\mathrm{In}$ at a beam energy of $70$ MeV. A total of $62$ new $\ensuremath{\gamma}$ transitions have been placed in the level scheme and several $\ensuremath{\Delta}I=1$ sequences and one $\ensuremath{\Delta}I=2$ sequence have been found. Lifetime measurements using the Doppler-shift attenuation method (DSAM) have been carried out for band states of $\ensuremath{\Delta}I=1$ and $\ensuremath{\Delta}I=2$. A decreasing trend of $B(M1)$ strengths with increasing spin deduced for the $\ensuremath{\Delta}I=1$ band indicates the presence of a shears mechanism. The experimental data for this band are compared with the tilted axis cranking (TAC) calculations. The $\ensuremath{\Delta}I=2$ band has been found to be a deformed band with ${\ensuremath{\beta}}_{2}~0.2$.
116623275
Experimental study of nuclei in the vicinity of the 'island of inversion' through the fusion-evaporation reaction
We report the observation of high-spin states in nuclei in the vicinity of the 'island of inversion', populated via the {sup 18}O+{sup 18}O fusion reaction at an incident beam energy of 34 MeV. The fusion reaction mechanism circumvents the limitations of other reactions used so far to populate excited states in these nuclei. The level structures of {sup 33,34}P and {sup 33}S have been investigated and their level schemes were substantially extended. The intensities and branching ratios of the {gamma} transitions were measured. The observed {gamma} coincidence intensity anisotropy and polarization asymmetry were analyzed for a consistent assignment of the spins and parities of the nuclear levels. The 1876-keV transition in {sup 34}P that had an ambiguous multipolarity assignment has been confirmed to be a mixed transition. Truncated (1p-1h) shell model calculations within the 'sdpf' valence space were performed. These calculations reproduce the experimental excitation energies of {sup 34}P but fail to explain the observed mixing ratio for the 1876-keV transition.
7522699
Nonperturbative quantum dynamics of a new inflation model
We consider an O(N) model coupled self-consistently to gravity in the semiclassical approximation, where the field is subject to {open_quotes}new inflation{close_quotes} type initial conditions. We study the dynamics self-consistently and non-perturbatively with non-equilibrium field theory methods in the large N limit. We find that spinodal instabilities drive the growth of non-perturbatively large quantum fluctuations which shut off the inflationary growth of the scale factor. We find that a very specific combination of these large fluctuations plus the inflaton zero mode assemble into a new effective field. This new field behaves classically and it is the object which actually rolls down. We show how this reinterpretation saves the standard picture of how metric perturbations are generated during inflation and that the spinodal growth of fluctuations dominates the time dependence of the Bardeen variable for superhorizon modes during inflation. We compute the amplitude and index for the spectrum of scalar density and tensor perturbations and argue that in all models of this type the spinodal instabilities are responsible for a {open_quotes}red{close_quotes} spectrum of primordial scalar density perturbations. A criterion for the validity of these models is provided and contact with the reconstruction program is established validating some of the results within amore » non-perturbative framework. The decoherence aspects and the quantum to classical transition through inflation are studied in detail by following the full evolution of the density matrix and relating the classicality of cosmological perturbations to that of long-wavelength matter fluctuations. {copyright} {ital 1998} {ital The American Physical Society}« less
118028364
Effect of Symmetry Energy on Intermediate Mass Fragments Production
The science of nuclear physics deals with the properties of nuclear matter which makes up the massive centre of the atom. When two heavy nuclei collide at high energy, they create strongly interacting matter at energy densities far above that of normal nuclei. Depending upon the energy through which two nuclei collide different type of phenomena occurs. When energy of colliding nuclei is between 100-600 MeV/nucleon then multifragmentation take place. By studying the fragments (at final stage of reaction) we can seize the idea about initial condition and various other parameter which influence the reaction and vice-versa. The symmetry energy Esym (ρ) of nuclear matter characterizes how the energy rises as one move away from equal numbers of neutrons and protons. Both the magnitude and density dependence of Esym (ρ) are critical for understanding the structure of rare isotopes and the reaction mechanism of heavy ion collisions but also many interesting issues in astrophysics. The best estimate of the density dependence of the symmetry energy can be parameterized as[3]