120722929
Constraint on the universal function in electroproduction
We show that analyticity and asymptotic behavior impose a severe contraint on the scale-invariant function widely suggested for the behavior of νW 2 (q 2 ν) as q 2 →∞. If the asymptotic behavior of the off-mass-shell Compton scattering amplitude is dominated by the usual (nonfixed) Regge trajectories, then our constraint is violated by the experimental candidates for the νW 2 curve. On the other hand, the introduction of a fixed pole corresponding to the one used by Damashek and Gilman alters the constraint, which is then consistant with the 18° data.
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.
125314068
Supersymmetric effects in B(s) ---> l+ l- gamma decays
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.
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.
118476324
Inflamagnetogenesis redux: Unzipping sub-Planckian inflation via various cosmoparticle probes
Abstract In this paper I introduce a precise constraint on primordial magnetogenesis, for a generic class of single-field inflationary model followed by small field excursion below the Planck scale. I also establish a connection between the magnetic field at the present epoch and primordial gravity waves (r) via non-vanishing CP asymmetry parameter ( ϵ CP ), which triggers the leptogenesis scenario. Finally, I explore various hidden cosmophenomenological features of theoretical CMB B-mode polarization spectra, which can be treated as a significant probe to put further stringent constraint on low and high scale small field inflationary models after releasing the Planck B-mode polarization data.
197509411
Large non-Gaussianities from DBI Galileon and resolution of sensitivity problem
We have studied primordial non-Gaussian features through bispectrum and trispectrum analysis from a model of potential driven DBI Galileon inflation originating from background supergravity and Gauss-Bonnet terms.We have explicitly shown the violation of the widely accepted Maldacena theorem and standard Suyama-Yamaguchi relation in squeezed limit configuration which leads to the resolution of the well-known sensitivity problem between the non-Gaussian parameters ($f_{NL},\tau_{NL},g_{NL}$) and tensor to scalar ratio($r$). Our analysis thus overcomes a generic drawback of the wide class of DBI inflationary models which was, of late, facing tension from observational ground.Hence large primordial non-Gaussianities can be obtained even from single field DBI Galileon and hence these class of models can be directly confronted with the forthcoming results of PLANCK.
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.
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.
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.