121251309
SOME QUARK--PARTON-MODEL INEQUALITIES FOR THE NEUTRON AND PROTON INELASTIC STRUCTURE FUNCTIONS.
119967965
Effect of a transverse momentum distribution in the parton model
The parton model for the inelastic lepton-nucleon scattering is generalized to include a realistic momentum distribution of the partons. In this formalism each parton is given a component of momentum which is orthogonal in a four-vector sense to the nucleon momentum. An approximation scheme is developed to take into account the effect of this orthogonal (transverse) momentum distribution of the partons. It is found to generate an additional scale-invariant contribution to the structure function $\ensuremath{\nu}{W}_{2}(\ensuremath{\nu}, {Q}^{2})$ as well as a non-scale-invariant contribution, as is expected. The scale-invariance-breaking term is found to be a power series in $\frac{{Q}^{2}}{{\ensuremath{\nu}}^{2}}$ and vanishes as $\ensuremath{\nu}$ or ${Q}^{2}$ goes to infinity for a fixed $\ensuremath{\omega}=\frac{2M\ensuremath{\nu}}{{Q}^{2}}$. The effect of the transverse momentum distribution is explicitly displayed and discussed for a few momentum distribution functions. The data on inelastic $e\ensuremath{-}p$ scattering are then analyzed for any significant deviations from scale invariance, and it is concluded that there is evidence for such deviations. On the assumption that the systematic errors in the data are small, we make some fits which display the dependence on ${Q}^{2}$. Finally, an attempt is made to fit the data with the formalism developed in the initial part of the paper. For this purpose use is made of a model for the partons, proposed previously by the authors to explain the data in the approximation that scale invariance is satisfied. Some comments are made on the properties of partons which are necessary to fit the data and on the present status of scale-invariance breaking.
120289082
NOTE ON THE MOST PROBABLE NUMBER OF PARTONS IN PARTON MODELS.
120089980
ELECTROMAGNETIC MASS DIFFERENCES.
Abstract In Cottingham's approach to electromagnetic masses ( δm ) one encounters the problem of unknown subtractions in the fixed mass dispersion relations for the virtual Compton scattering amplitude. We avoid this problem and express δm in terms of measurable quantities, assuming knowledge of light-cone singularities of the electro-magnetic current commutator.
16352408
Half lives and Rates for Electron Capture on Drip Line Nuclei and for Beta Decay with 65 < A <100
The half lives are calculated for the process of $\beta^\pm$ decay and electron capture for nuclei in mass range $\sim$ 65 - 100 relevant for the core of a massive star at late burning stage of steller evolution that leads to supernova explosion. The rates of electron capture process are also computed for nuclei relevant during presupernova stage of massive stars. These half lives and rates are calculated by expressing $\beta^\pm$ Gamow-Teller decay strengths in terms of smoothed bivariate strength densities. These strength densities are constructed in the framework of spectral averaging theory for two body nuclear Hamiltonian in a large nuclear shell model space. The method has a natural extension to weak interaction rates for r and rp-processes.
16847898
Mass and Scalar Cross-sections for Neutralino Dark Matter in Anomaly Mediated Supersymmetry Breaking Model
We consider the neutralino to be the lightest supersymmetric particle in the framework of the minimal anomaly mediated supersymmetry breaking (mAMSB) model. We have studied the variation of the neutralino mass with the supersymmetric parameters. Considering these neutralinos to be candidates for weakly interacting massive particles (WIMPs) or cold dark matter, we have calculated the neutralino nucleon scalar cross sections and compared them with the results of the DAMA-NaI neutralino direct detection search. From this study, we observe that the mAMSB model results cannot explain the allowed region in WIMP mass and WIMP–nucleon scalar cross-section space obtained from the annual modulation signature in the DAMA-NaI experiment.
2568474
Late-time acceleration in a slow-moving Galileon field
�� 2M2 � ;� � ;� respects the Galileon symmetry in curved spacetime. We carry out detailed investigations of the underlying dynamics of this Lagrangian with an Einstein-Hilbert term and a potential. We demonstrate that the model can give rise to a viable ghost-free late-time acceleration of the universe. Furthermore, we study the cosmological perturbation of the model and see that the model gives different big bang nucleosynthesis constraints at early times. We also carry out the observational analysis of the model and use observational data from growth, type Ia supernovae data, baryon acoustic oscillations, and the cosmic microwave background to constrain the parameters of the theory. From cosmological observations (1-4) it is evident that our Universe is currently undergoing an accelerated ex- pansion. The theoretical understanding of the nature of cosmic repulsion is a challenge for the cosmologist and the particle physicist today. A variety of approaches have been studied to address this problem, but to date there is still no definite answer. According to the standard ap- proach, the late-time acceleration can be accounted for by supplementing the energy-momentum tensor by an exotic fluid component with large negative pressure dubbed dark energy (5-12), which constitutes about three quarters of the total cosmic budget of the Universe (13). The simplest candidate for dark energy which is consistent with the observations is provided by a cosmological con- stant � . However, there are various serious theoretical problems associated to it, namely, the fine-tuning and the coincidence problems. An interesting alternative to a cosmological constant is provided by the scalar fields. The cosmological dynamics of a variety of scalar field models has been studied in the literature (7). Though these models do not address the cosmological constant problem, they can give late-time cosmic acceleration and can also provide a viable cosmo- logical dynamics at early epochs. Scalar field models with generic features like the trackers are capable of alleviating the fine-tuning and coincidence problems. At present, these scalar field models are absolutely consistent with the observations but, at the same time, a large number of these models are also permitted. One must therefore rely on future data which should allow one to narrow down the class of permissible scalar field dark energy models.
118595488
Generalizing thawing dark energy models: the standard vis-à-vis model independent diagnostics
We propose a two parameter generalization for the dark energy equation of state (EOS) wX for thawing dark energy models which includes PNGB, CPL and Algebraic thawing models as limiting cases and confront our model with the latest observational data namely SNe Ia, OHD, CMB, BOSS data. Our analysis reveals that the phantom type of thawing dark energy is favoured upto 2� confidence level. These results also show that thawing dark e nergy EOS is not unique from observational point of view. Though different thawing dark energy models are not distinguishable from each other from best-fit values (upto 2� C.L.s) of matter density parameter ( 0) and hubble parameter (H0) at present epoch, best-fit plots of linear growth of matter perturbation (f ) and average deceleration parameter (qav); the difference indeed reflects in best-fit variations of thawing dark energy EOS, model-independent geometrical diagnostics like the statefinder pair {r, s} and Om3 parameter. We are thus led to the conclusion that unlike the standard observables ( 0, H0, f , qav), the model-independent pa� � ,
43103867
A Texture of neutrino mass matrix in view of recent neutrino experimental results
In view of recent neutrino experimental results such as SNO, Super-Kamiokande (SK), CHOOZ and neutrinoless double beta decay $(\beta\beta_{0\nu})$, we consider a texture of neutrino mass matrix which contains three parameters in order to explain those neutrino experimental results. We have first fitted parameters in a model independent way with solar and atmospheric neutrino mass squared differences and solar neutrino mixing angle which satisfy LMA solution. The maximal value of atmospheric neutrino mixing angle comes out naturally in the present texture. Most interestingly, fitted parameters of the neutrino mass matrix considered here also marginally satisfy recent limit on effective Majorana neutrino mass obtained from neutrinoless double beta decay experiment. We further demonstrate an explicit model which gives rise to the texture investigated by considering an $SU(2)_L\times U(1)_Y$ gauge group with two extra real scalar singlets and discrete $Z_2\times Z_3$ symmetry. Majorana neutrino masses are generated through higher dimensional operators at the scale $M$. We have estimated the scales at which singlets get VEV's and M by comparing with the best fitted results obtained in the present work.