120344310
Weak production and electroproduction of. delta. (1236) in a Zucker-model calculation
Zucker's model for weak production and electroproduction of ..delta..(1236) is reconsidered in the light of recent experimental data. We find that the disagreement between the predictions of the Zucker model and the experimental data can be significantly reduced by choosing a different form for ..omega.. exchange.
125314068
Supersymmetric effects in B(s) ---> l+ l- gamma decays
122154027
Relativistic oscillator in a Bethe-Salpeter model: Nonexistence of discrete bound states
We investigate the solutions of the covariant Bethe-Salpeter equation for bound states of a scalar quark-antiquark system with an effective confining kernel which in coordinate four-space behaves as ${R}^{2}$. Using a suitable set of new variables we separate the equation into one-dimensional equations and study the eigenvalue problem. We find that the covariant bound-state Bethe-Salpeter equation with the above kernel possesses only a continuous spectrum.
121960660
Neutral-current cross sections for double-pion production by neutrinos
We have derived expressions for the differential cross sections for two-pion production by the neutral current in a neutrino-induced hadron reaction. We assume a general V, A form of the neutral current with arbitrary admixture of isotopic scalar and vector parts and utilize the algebra of currents and the PCAC (partial conservation of the axial-vector current) hypothesis to obtain the amplitude for ..nu.. + N ..-->.. ..nu.. + N + ..pi.. + ..pi... Two different cases have been studied: (i) Both the outgoing pions are at threshold. (ii) They are produced via the formation of N*. The results are useful to examine the structure of the neutral current.
10367884
Comment on "New interaction for the enhancement of the Delta I=1/2 amplitude in weak decays"
118238640
HIGH-ORDER LOW-ENERGY THEOREMS FOR NUCLEON COMPTON SCATTERING.
The well-known zero- and first-order (in photon energy) low-energy theorems for nucleon Compton scattering have recently been derived by Abarbanel and Goldberger using only the physical helicity amplitudes for the process and exploiting their kinematical singularities and zeros. We use this approach to study higher-order terms in photon energy and find the result, not entirely new, that four of the six independent helicity amplitudes are determined in second order by the mass, charge, and magnetic moment of the nucleon. Therefore, these parameters together with two structure-dependent constants, which can be interpreted approximately as electric and magnetic polarizabilities, completely determine the Compton scattering to second order in energy. Similar simplifications occurring in the structure of higher-order terms in energy are also discussed. The kinematical singularity structure of helicity amplitudes is a manifestation of Lorentz invariance. We claim to have fully exploited the requirements of Lorentz invariance and therefore to have derived the complete set of low-energy theorems for this process.
119082570
Thermodynamics of Charged Kalb Ramond AdS black hole in presence of Gauss-Bonnet coupling
We study the role of the Gauss-Bonnet corrections to the gravity action on the charged AdS black hole in presence of rank 3 antisymmetric Kalb Ramond tensor field strength. Analyzing the branch singularity and the killing horizon, we explicitly derive various thermodynamic parameters and study their behaviour in presence of five dimensional Gauss-Bonnet coupling in AdS space-time. The possibility of a second order phase transition is explored in the light of AdS/CMT correspondence and various critical exponents associated with the discontinuities of the various thermodynamic parameters are determined. We further comment on the universality of the well known Rushbrooke Josephson scaling law and derive a relation between the degree of homogeneity appearing in various free energies and the critical exponents by homogeneous hypothesis test. By making use of the constraints appearing from Hawking temperature and Gauss-Bonnet extended gravity version of Kubo formula we introduce a bound on the five dimensional Gauss-Bonnet coupling and the viscosity entropy ratio in the four dimensional holographic Conformal Field Theory (CFT) dual. This yields a fractional deviation in viscosity entropy ratio from the result obtained from Einstein gravity.
118378176
Brane inflation in background supergravity
We propose a model of inflation in the framework of brane cosmology driven by background supergravity. Starting from bulk supergravity we construct the inflaton potential on the brane and employ it to investigate for the consequences to inflationary paradigm. To this end, we derive the expressions for the important parameters in brane inflation, which are somewhat different from their counterparts in standard cosmology, using the one loop radiative corrected potential. We further estimate the observable parameters and find them to fit well with recent observational data by confronting with WMAP7 using CAMB. We also analyze the typical energy scale of brane inflation with our model, which resonates well with present estimates from cosmology and standard model of particle physics.
119294991
Low & high scale MSSM inflation, gravitational waves and constraints from Planck
In this paper we will analyze generic predictions of an inflection-point model of inflation with Hubble-induced corrections and study them in light of the Planck data. Typically inflection-point models of inflation can be embedded within Minimal Supersymmetric Standard Model (MSSM) where inflation can occur below the Planck scale. The flexibility of the potential allows us to match the observed amplitude of the TT-power spectrum of the cosmic microwave background radiation with low and high multipoles, spectral tilt, and virtually mild running of the spectral tilt, which can put a bound on an upper limit on the tensor-to-scalar ratio, r ≤ 0.12. Since the inflaton within MSSM carries the Standard Model charges, therefore it is the minimal model of inflation beyond the Standard Model which can reheat the universe with the right thermal degrees of freedom without any dark-radiation.
119187831
Reheating and leptogenesis in a SUGRA inspired brane inflation
Abstract We have studied extensively phenomenological implications in a specific model of brane inflation driven by background supergravity (Choudhury and Pal, 2011) [1] , via thermal history of the universe and leptogenesis pertaining to the particle physics phenomenology of the early universe. Using the one loop corrected inflationary potential we have investigated for the analytical expression as well as the numerical estimation for brane reheating temperature for standard model particles. This results in some novel features of reheating from this type of inflation which have serious implications in the production of heavy Majorana neutrinos needed for leptogenesis through the reheating temperature. We have also derived the expressions for the gravitino abundance during reheating and radiation dominated era. We have further estimated different parameters at the epoch of phase transition and revealed their salient features. At the end we have explicitly given an estimate of the amount of CP violation through the effective CP phase which is related to baryon asymmetry as well as gravitino dark matter abundance.
119286198
A step toward exploring the features of Gravidilaton sector in Randall–Sundrum scenario via lightest Kaluza–Klein graviton mass
In this paper we study the role of the 5D Gauss–Bonnet corrections and two-loop higher genus contribution to the gravity action in type IIB string theory inspired low energy supergravity theory in the light of gravidilatonic interactions on the lightest Kaluza–Klein graviton mass spectrum. From the latest constraints on the lightest Kaluza–Klein graviton mass as obtained from the ATLAS dilepton search in 7 TeV proton–proton collision experiments, we have shown that due to the presence of Gauss–Bonnet and string loop corrections, the warping solution in an $$\mathbf{AdS_{5}}$$AdS5 bulk is quite distinct from the Randall–Sundrum scenario. We discuss the constraints on the model parameters to fit with the present ATLAS data.