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Rajpoot, Subhash

Publications and source records attributed to Rajpoot, Subhash.

10 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Multi-TeV flaring from blazars: Markarian 421 as a case study

The TeV blazar Markarian 421 underwent multi-TeV flaring during April 2004 and simultaneously observations in the X-ray and TeV energies were made. It was observed that the TeV outbursts had no counterparts in the lower energy range. One implication of this is that it might be an orphan flare. We show that Fermi-accelerated protons of energy ≤168 TeV can interact with the low energy tail of the background synchrotron self-Compton photons in the inner region of the blazar to produce the multi-TeV flare and our results fit very well with the observed spectrum. Based on our study, we predict that the blazars with a deep valley in between the end of the synchrotron spectrum and the beginning of the SSC spectrum are possible candidates for orphan flaring. Future possible candidates for this scenario are the HBLs Mrk 501 and PG 1553 + 113 objects.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Detection of ultra-high-energy neutrinos by IceCube: sterile neutrino scenario

The short-baseline neutrino oscillation experiments, the excess of radiation from the measurement of the cosmic microwave background radiation, the necessity of the nonbaryonic dark matter candidate, and the depletion of the neutrino flux in IceCube all seem to hint at new physics beyond the standard model. An economical way to address these issues is to invoke the existence of sterile neutrinos. We present simple extensions of the standard model with additionally three sterile neutrinos and discuss the corresponding PMNS like neutrino flavor mixing matrix. The noteworthy features of the sterile neutrino scenario advocated here are that the lightest one is almost degenerate with one of the active neutrinos, the second sterile has mass of order eV, and the heaviest one is in the keV range. In the present scenario, the short-baseline anomaly is explained through Δm 2 ~1eV 2 , the depletion of the muon neutrino flux in IceCube is explained through Δm 2 ~4.0×10 -16 eV 2 , and the dark matter problem is addressed through Δm 2 ~1keV 2 . Our proposed mixing matrix is also compatible with the observed neutrino oscillation data. We show that the high-energy muon and the tau neutrino fluxes from Gamma Ray Bursts can be depleted in IceCube by as much as 38 and 43 %, respectively. These substantial depletions in both muon and tau neutrino fluxes are due to their small but sizable mixing with the sterile neutrinos.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Stueckelberg mechanisms for tensor multiplets and compactification on AdS{sub 3}xS{sup 3}

We present Stueckelberg mechanisms for tensor multiplets coupled to supergravity in four dimensions (4D), six dimensions (6D), and three dimensions (3D). For N=1 supergravity in 4D, our field content is (e{sub {mu}}{sup m},{psi}{sub {mu}}), (B{sub {mu}{nu},{chi}},{phi}) and (A{sub {mu},{lambda}}), respectively, for the supergravity, tensor, and vector multiplets. In our Stueckelberg mechanism, the Abelian vector field A{sub {mu}} is absorbed into the longitudinal component of the tensor B{sub {mu}{nu}}, which becomes massive. The field strength F=dA of A is replaced by F{identical_to}F+mB, where m is a coupling constant with the dimension of mass. In 6D, we utilize the so-called dual version for N=2 supergravity, in order to avoid the obstruction caused by the Chern-Simons term F and A in the B-field strength G. Instead of the F and A-term in G, the 6D Lagrangian has a peculiar topological and cubic interaction term proportional to m{sup -1}F and F and F. In 3D, we also show that a similar mechanism works for N=1 supergravity. Interestingly, the basic structure is parallel to the 4D case, except that the originally nonpropagating field B starts propagating, after absorbing the A-field. We also show a possible compactification of 6D theory on AdS{sub 3}xS{sup 3}.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗