arXiv subjects

Kumar Rao

Publications and source records attributed to Kumar Rao.

24 records · Page 2Linked to original sources

arXiv2006

Probing CP-violating contact interactions in e+e- --> HZ with polarized beams

We examine very general four-point interactions arising due to new physics contributing to the Higgs production process e+e- --> HZ. We write all possible forms for these interactions consistent with Lorentz invariance. We allow the possibility of CP violation. Contributions to the process from anomalous ZZH and gammaZH interactions studied earlier arise as a special case of our four-point amplitude. Expressions for polar and azimuthal angular distributions of Z arising from the interference of the four-point contribution with the standard-model contribution in the presence of longitudinal and transverse beam polarization are obtained. An interesting CP-odd and T-odd contribution is found to be present only when both electron and positron beams are transversely polarized. Such a contribution is absent when only anomalous ZZH and gammaZH interactions are considered. We show how angular asymmetries can be used to constrain CP-odd interactions at a linear collider operating at a centre-of-mass energy of 500 GeV with transverse beam polarization.

hep-ph↗

arXiv2004

Searching for signals of minimal length in extra dimensional models using dilepton production at hadron colliders

Theories of quantum gravity suggest the existence of a minimal length scale. It is interesting to speculate what the consequences of the existence of such a length scale would be for models of large extra dimensions, in particular, the ADD model. When ADD model is conflated with the minimal length scale scenario, processes involving virtual exhange of gravitons cease to be ulraviolent divergent. We study the production of dileptons at hadron colliders as an example of a process mediated by virtual gravitons. We find that the bounds we derive on the effective string scale are significantly different (in fact, less stringent) from those derived in the conventional ADD model, both at the upgraded Tevatron and the Large Hadron Collider.

hep-ph↗

arXiv2002

Finite Temperature Induced Fermion Number for Quarks in a Chiral Field

We compute the finite temperature correction to the induced fermion number for fermions coupled to a static SU(2) chiral background, using the derivative expansion technique. At zero temperature the induced fermion number is topological, being the winding number of the chiral background. At finite temperature however, higher order terms in the derivative expansion give nontopological corrections to the winding number. We use this result to show that the standard cancellation of the fractional parts of the fermion number inside and outside the bag in an SU(2) x SU(2) hybrid chiral bag model of the nucleon does not occur at nonzero temperature.

hep-th↗

arXiv2002

Finite Temperature Induced Fermion Number In The Nonlinear sigma Model In (2+1) Dimensions

We compute the finite temperature induced fermion number for fermions coupled to a static nonlinear sigma model background in (2+1) dimensions, in the derivative expansion limit. While the zero temperature induced fermion number is well known to be topological (it is the winding number of the background), at finite temperature there is a temperature dependent correction that is nontopological -- this finite T correction is sensitive to the detailed shape of the background. At low temperature we resum the derivative expansion to all orders, and we consider explicit forms of the background as a CP^1 instanton or as a baby skyrmion.

hep-th↗

arXiv2001

Thermal Fluctuations of Induced Fermion Number

We analyze the phemomenon of induced fermion number at finite temperature. At finite temperature, the induced fermion number $ $ is a thermal expectation value, and we compute the finite temperature fluctuations, $(ΔN)^2= - ^2$. While the zero temperature induced fermion number is topological and is a sharp observable, the finite temperature induced fermion number is generically nontopological, and is not a sharp observable. The fluctuations are due to the mixing of states inherent in any finite temperature expectation value. We analyze in detail two different cases in 1+1 dimensional field theory: fermions in a kink background, and fermions in a chiral sigma model background. At zero temperature the induced fermion numbers for these two cases are very similar, but at finite temperature they are very different. The sigma model case is generic and the induced fermion number is nontopological, but the kink case is special and the fermion number is topological, even at finite temperature. There is a simple physical interpretation of all these results in terms of the spectrum of the fermions in the relevant background, and many of the results generalize to higher dimensional models.

hep-th↗

arXiv1999

Lam'e Instantons

We perform a precise analytic test of the instanton approximation by comparing the exact band spectrum of the periodic Lamé potential to the tight-binding, instanton and WKB approximations. The instanton result gives the correct leading behavior in the semiclassical limit, while the tight-binding approximation does even better. WKB is off by an overall factor of $\sqrt{e/π}$.

hep-th↗