Bipin R. Desai

Three-Neutrino Mass Matrices with Two Texture Zeros

Out of the 15 3 × 3 neutrino mass matrices with two texture zeros, seven are compatible with the neutrino oscillation data. While two of them correspond to hierarchical neutrino masses and 1 to an inverted hierarchy, the remaining four correspond to degenerate masses. Moreover only the first three of the seven mass matrices are compatible with the maximal mixing angle of atmospheric neutrino and hence favored by data. We give compact expressions for mass matrices in terms of mass eigenvalues and study phenomenological implications for the seven cases. Similarity of the textures of the neutrino, charged-lepton mass matrices with those of quark mass matrices is also discussed.

Neutrino condensate as origin of dark energy

We propose a new solution to the origin of dark energy. We suggest that it was created dynamically from the condensate of a singlet neutrino at a late epoch of the early Universe through its effective self-interaction. This singlet neutrino is also the Dirac partner of one of the three observed neutrinos, hence dark energy is related to neutrino mass. The onset of this condensate formation in the early Universe is also related to matter density and offers an explanation of the coincidence problem of why dark energy (70%) and total matter (30%) are comparable at the present time. We demonstrate this idea in a model of neutrino mass with (right-handed) singlet neutrinos and a singlet scalar.

Quark mass matrices with four and five texture zeros, and the CKM matrix, in terms of mass eigenvalues

Using the triangular matrix techniques of Kuo, Mansour, and Wu and Chiu, Kuo, and Wu for the four and five texture zero cases, with vanishing (11) diagonal elements for U and D matrices, it is shown, from the general eigenvalue equations and hierarchy conditions, that the quark mass matrices and the Cabibbo-Kobayashi-Maskawa (CKM) matrix can be expressed (except for the phases) entirely in terms of quark masses. The matrix structures are then quite simple and transparent. We confirm their results for the five texture zero case but find, upon closer examination of all the CKM elements which our results provide, that six of their nine patterns for the four texture zero case are not compatible with experiments. In total, only one five texture zero and three four texture zero patterns are allowed.

A model for central charm production inpp collision

AbstractThe major part of central charm production inpp collision is proposed to arise from a charm

A lowP T parton fragmentation model with diffractive resonance production: Thepp→(π±,K±)+X inclusive reactions

(D\bar D)

Possibility that the Pomeron-Reggeon cut contains the Regge pole

component in the hadronization of the scattered quark. We use the charm hadronization model previously developed to explain the like sign dimuon events in neutrino scattering. Thus we have a parameter free prediction for the central charm crosssection relative to thepp total cross-section. The predicted cross-section agrees with data in magnitude as well as in its energy, Feynmanx andpT dependence.

An SO(10) GUT With See-Saw Masses For All Fermions

In this work we study an SO(10) GUT model with minimum Higgs representations belonging only to the 210 and 16 dimensional representations of SO(10). We add a singlet fermion S in addition to the usual 16 dimensional representation containing quarks and leptons. There are no Higgs bi-doublets and so charged fermion masses come from one-loop corrections. Consequently all the fermion masses, Dirac and Majorana, are of the see-saw type. We minimize the Higgs potential and show how the left-right symmetry is broken in our model where it is assumed that a D-parity odd Higgs field gets a vacuum expectation value at the grand unification scale. From the renormalization group equations we infer that in our model unification happens at 1015 GeV and left-right symmetry can be extended up to some values just above 1011 GeV. The Yukawa sector of our model is completely different from most of the standard grand unified theories and we explicitly show how the Yukawa sector will look like in the different phases and briefly comment on the running of the top quark mass. We end with a brief analysis of lepton number asymmetry generated from the interactions in our model. ∗ kaushik@prl.res.in † crdas@imsc.res.in ‡ bipin.desai@ucr.edu, bipin@earthlink.net § graj@imsc.res.in ¶ utpal@prl.res.in 1

pN-Spectrum for heavy quark decays

It is shown that carefully measured momemtum distributions in the inclusive reactionspp→C+X,C=π+, π−,K+,K− can be quantitatively understood in a parton fragmentation approach provided both diquark fragmentation as well as diffractive resonance production and decay are taken into a account.