118480430
Note on excited leptons
The bound-state problem in Glashow-Salam-Weinberg theory and a composite model has been investigated.
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.
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.
10367884
Comment on "New interaction for the enhancement of the Delta I=1/2 amplitude in weak decays"
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.
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.
56054159
An accurate bound on tensor-to-scalar ratio and the scale of inflation
Abstract In this paper we provide an accurate bound on primordial gravitational waves, i.e. tensor-to-scalar ratio ( r ) for a general class of single-field models of inflation where inflation occurs always below the Planck scale, and the field displacement during inflation remains sub-Planckian. If inflation has to make connection with the real particle physics framework then it must be explained within an effective field theory description where it can be trustable below the UV cut-off of the scale of gravity. We provide an analytical estimation and estimate the largest possible r , i.e. r ⩽ 0.12 , for the field displacement less than the Planck cut-off.
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.
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.
118404858
Brane inflation: A field theory approach 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. We have studied extensively reheating phenomenology, which explains the thermal history of the universe and leptogenesis through the production of thermal gravitino pertaining to the particle physics phenomenology of the early universe.