120204081
Statistical model analysis of fission fragment angular distributions for the system 16 O+ 181 Ta
Fission fragment angular distributions have been measured for the fusion of ${}^{16}\mathrm{O}$ with deformed ${}^{181}\mathrm{Ta}$ target, in the energy range 90 MeV to 110 MeV. Combining with the existing data of evaporation residue and fission cross sections in the literature, the fusion cross sections have been determined in the range $1.1l~{E/V}_{B}l~1.6.$ Detailed statistical model analysis of the entire data set has been performed and it has been shown that fission fragment anisotropies calculated are in good agreement with the experimental data. Even at the lowest energy studied, ${(E=1.1V}_{B})$ as there is good agreement between the data and the calculation, it can be concluded that the quasifission effect is negligible at this energy.
6716809
Performance of an Axial Gas Ionization Detector
An axial gas ionization chamber has been fabricated for use as a DeltaE detector in heavy ion induced nuclear reactions. Different operating parameters such as gas type, pressure, anode voltage, and anode structures have been optimized. The transparency of the anode structure is observed to play an important role in improving the energy resolution of the detector
120752932
Elastic scattering and fusion cross sections for Be7,Li7+Al27 systems
Quasi-elastic-scattering and transfer reaction cross-section measurements were made for the {sup 7}Be+{sup 27}Al system at E{sub lab}=17, 19, and 21 MeV in the angular range {theta}{sub c.m.}=12 deg. An optical model (OM) analysis of the quasi-elastic scattering data was carried out. The fusion cross sections were derived at these energies by subtraction of the integrated transfer cross sections from the reaction cross sections obtained from the fits to quasi-elastic-scattering data. These fusion cross sections were found to be consistent with those obtained from the coupled-channels calculations. Elastic scattering and fusion cross sections were measured for the {sup 7}Li+{sup 27}Al system at E{sub lab}=10, 13, 16, 19, and 24 MeV. For elastic scattering the angular coverages were in the {theta}{sub lab}=12 deg. - 72 deg. range and for fusion the {alpha}-evaporation spectra from the compound nucleus were measured in the angular range {theta}{sub lab}=52 deg. - 132 deg. (142 deg. at 10 MeV). The elastic-scattering angular distributions were subjected to OM analysis. The {alpha}-evaporation spectra were reproduced with the statistical model calculations, and the fusion cross sections were extracted from them. The fusion cross sections were also extracted by subtraction of the integrated inelastic-scattering cross sections from the reaction cross sectionsmore » obtained from the OM fits to the elastic-scattering data, and these fusion data were found to be consistent. The CCDEF calculations describe these data quite well. A comparison of the fusion data for the {sup 7}Be+{sup 27}Al and {sup 7}Li+{sup 27}Al systems shows a similar and consistent behavior.« less
121131613
Effect of higher order couplings in the barrier distribution of 12 C + 142 Nd extracted from quasielastic excitation functions
To explore the effects of higher order coupling on the barrier distribution, we have measured the quasielastic excitation function for 12 C+ 142 Nd around the nominal Coulomb barrier from 44 to 58 MeV in steps of 1 MeV. Theoretical coupled channel calculations with one and two phonon states were performed using the code ECIS94. The analysis showed that the second order coupling effects explained the barrier distribution profile and excitation function more appropriately than the first order couplings.
118531090
Holographic non-Fermi liquid in a background magnetic field
We study the effects of a nonzero magnetic field on a class of 2+1 dimensional non-Fermi liquids, recently found in [Hong Liu, John McGreevy, and David Vegh, arXiv:0903.2477.] by considering properties of a Fermionic probe in an extremal AdS{sup 4} black hole background. Introducing a similar fermionic probe in a dyonic AdS{sup 4} black hole geometry, we find that the effect of a magnetic field could be incorporated in a rescaling of the probe fermion's charge. From this simple fact, we observe interesting effects like gradual disappearance of the Fermi surface and quasiparticle peaks at large magnetic fields and changes in other properties of the system. We also find Landau level like structures and oscillatory phenomena similar to the de-Haas-van Alphen effect.
5278859
R -charged AdS 5 black holes and large N unitary matrix models
Using the anti-de Sitter (AdS)/conformal field theories correspondence, we establish a correspondence between the intricate thermal phases of $R$-charged ${\mathrm{AdS}}_{5}$ black holes and the $R$-charge sector of the $N=4$ gauge theory, in the large $N$ limit. Integrating out all fields in the gauge theory, except the thermal Polyakov line, leads to an effective unitary matrix model. In the canonical ensemble, a logarithmic term is generated in the nonzero charge sector of the matrix model. This term is important for discussing various supergravity properties like (i) the nonexistence of a thermal AdS phase as a solution, (ii) the existence of a point of cusp catastrophe in the phase diagram, and (iii) the matching of saddle points and the critical exponents of supergravity and those of the effective matrix model. Our study is restricted to a unitary matrix model where the action depends only on $\mathrm{Tr}U\text{ }\mathrm{Tr}{U}^{\ifmmode\dagger\else\textdagger\fi{}}$.
119256345
The many phases of holographic superfluids
We investigate holographic superfluids in AdSd+1 with d =3, 4 in the nonbackreacted approximation for various masses of the scalar field. In d =3 the phase structure is universal for all the masses that we consider: the critical temperature decreases as the superfluid velocity increases, and as it is cranked high enough, the order of the phase transition changes from second to first. Surprisingly, in d = 4 we find that the phase structure is more intricate. For sufficiently high mass, there is always a second order phase transition to the normal phase, no matter how high the superfluid velocity. For some parameters, as we lower the temperature, this transition happens before a first order transition to a new super conducting phase. Across this first order transition, the gap in the transverse conductivity jumps from almost zero to about half its maximum value. We also introduce a double scaling limit where we can study the phase transitions(semi-)analytically in the large velocity limit. The results corroborate and complement our numerical results. In d =4, this approach has the virtue of being fully analytically tractable.
119203538
Competing holographic orders
We model competition between different macroscopic orders in an holographic context. The orders we considered are a superconducting order, modeled by a charged scalar field, and a magnetic order modeled by a neutral scalar field. We also discuss the case of two competing scalars coupled to a single gauge field.In all cases discussed here the phases tend to compete, rather than enhance each other. The condensation of one scalar hinders any further instabilities, unless we have a sufficiently strong repulsive interactions between the bulk scalars. We provide both analytic arguments and numerical demonstration of this fact.Based on the cases discussed here, we conjecture that holographic orders tend to compete for attractive bulk interactions, including gravity, and to cooperate, or be mutually enhancing, for repulsive bulk interactions between the corresponding order parameters.