arXiv subjects

U. Sarkar

Publications and source records attributed to U. Sarkar.

29 records · Page 2Linked to original sources

arXiv2000

Effects of quantum space time foam in the neutrino sector

We discuss violations of CPT and quantum mechanics due to interactions of neutrinos with space-time quantum foam. Neutrinoless double beta decay and oscillations of neutrinos from astrophysical sources (supernovae, active galactic nuclei) are analysed. It is found that the propagation distance is the crucial quantity entering any bounds on EHNS parameters. Thus, while the bounds from neutrinoless double beta decay are not significant, the data of the supernova 1987a imply a bound being several orders of magnitude more stringent than the ones known from the literature. Even more stringent limits may be obtained from the investigation of neutrino oscillations from active galactic nuclei sources, which have an impressive potential for the search of quantum foam interactions in the neutrino sector.

hep-ph↗

arXiv2000

Neutrino Majorana Mass and Baryon Number of the Universe below the Electroweak Symmetry breaking Scale

If the neutrino is Majorana type and the electroweak phase transition is second or weak first order, neutrino-induced interactions together with sphaleron transitions have the potential to erase a previously generated baryon asymmetry of the universe. Taking correctly into account the evolution of the vacuum expectation of the Higgs field the effective light neutrino masses are constrained to be lighter than order 10 MeV, while the effective heavy masses are constrained to be heavier than order 10^7 GeV.

hep-ph↗

arXiv2000

Comment on ``Closing the neutrinoless double beta decay window into VEP and/or VLI''

The constraints from the non-observation of neutrinoless double beta decay on the violations of Lorentz invariance (VLI) or violations of the equivalence principle (VEP) have recently been re-examined (hep-ph/9904298) and it was claimed that the constraints are not valid. In this reply we point out that this statement is not correct and prove that the arguments given are wrong.

hep-ph↗

arXiv2000

New exotics in the double beta decay contributions zoo

We discuss the potential of neutrinoless double beta decay for testing Lorentz invariance and the weak equivalence principle as well as contributions from dilaton exchange gravity in the neutrino sector. While neutrino oscillation bounds constrain the region of large mixing of the weak and gravitational eigenstates, we obtain new constraints on violations of Lorentz invariance and the equivalence principle from neutrinoless double beta decay, applying even in the case of no mixing. Double beta decay thus probes a totally unconstrained region in the parameter space.

hep-ph↗

arXiv2000

Effects of New Gravitational Interactions on Neutrinoless Double Beta Decay

It has recently been proposed that violations of Lorentz invariance or violations of the equivalence principle can be constrained from the non-observation of neutrinoless double beta decay. We generalize this analysis to all possible new gravitational interactions and discuss briefly the constraints for different cases.

hep-ph↗

arXiv1998

Test of Special Relativity and Equivalence Principle from Neutrinoless Double Beta Decay

We generalize the formalism for testing Lorentz invariance and the equivalence principle in the neutrino sector. While neutrino oscillation bounds constrain the region of large mixing of the the weak and gravitational eigenstates, we obtain new constraints on violations of Lorentz invariance and the equivalence principle from neutrinoless double beta decay. These bounds apply even in the case of no mixing and thus probe a totally unconstrained region in the parameter space.

hep-ph↗

arXiv1998

Test of Special Relativity and Equivalence principle from K Physics

A violation of Local Lorentz Invariance (VLI) and hence the special theory of relativity or a violation of equivalence principle (VEP) in the Kaon system can, in principle, induce oscillations between $K^0$ and $\bar{K}^0$. We construct a general formulation in which simultaneous pairwise diagonalization of mass, momemtum, weak or gravitational eigenstates is not assumed. %and the maximum attainable %velocities of the velocity eigenstates are different. We discuss this problem in a general way and point out that, as expected, the VEP and VLI contributions are indistinguishable. We then insist on the fact that VEP or VLI can occur even when CPT is conserved. A possible CP violation of the superweak type induced by VEP or VLI is introduced and discussed. We show that the general VEP mechanism (or the VLI mechanism, but not both simultaneously), with or without conserved CPT, could be clearly tested experimentally through the energy dependence of the $K_L-K_S$ mass difference and of $η_{+-}$, $η_{00}$, $δ$. Constraints imposed by present experiments are calculated.

hep-ph↗

arXiv1997

Test of Special Relativity from K Physics

A breakdown of the Local Lorentz Invariance and hence the special theory of relativity in the Kaon system can, in principle, induce oscillations between the $K^0$ and $\bar{K}^0$ states. We construct a general formulation in which simultaneous pairwise diagonalization of mass, momentum and weak eigenstates is not assumed and the maximum attainable speeds of the momentum eigenstates are different. This mechanism permits Local Lorentz Invariance violation in a manner that may or may not violate CPT. In the $CPT-$conserving case, we show that violation of special relativity could be clearly tested experimentally via the energy dependence of the $K_L-K_S$ mass difference and we discuss constraints imposed by present experiments. In the CPT-violating case the $K^0$--$\bar{K}^0$ system also allows the possiblity of testing different Lorentz properties of matter and antimatter.

hep-ph↗

arXiv1996

Test of the Equivalence Principle from K Physics

A violation of the equivalence principle (VEP) in the Kaon system can, in principle, induce oscillations between $K^\circ$ and $\overline{K^\circ}$ in a manner that need not violate CPT conservation. We show that such a CPT-conserved VEP mechanism could be clearly tested experimentally through the energy dependence of the $K_L-K_S$ mass difference and discuss constraints imposed by present experiments.

hep-ph↗

arXiv1995

Test of the Equivalence Principle from Neutrino Oscillation Experiments

We consider the hypothesis that neutrino oscillation data can be explained if the gravitational couplings of (massless or degenerate mass) neutrinos are flavour non--diagonal, in violation of the equivalence principle. We analyze the various neutrino oscillation laboratory experimental data including the recent LSND observations to constrain the relevant parameter space. We find that there is no allowed region of parameter space which can explain the existing data, implying that the LSND result cannot be explained by oscillations of degenerate-mass neutrinos due to equivalence principle violations.

hep-ph↗

arXiv1993

Non-perturbative unification in the light of LEP results

We consider an alternative to conventional GUTs originally proposed by Maiani, Parisi and Petronzio, where owing to the existence of extra fermion generations at some intermediate scale, the gauge couplings become large at high energies. We first comment on how the non- supersymmetric version of this scenario is ruled out; we then consider the two-loop evolution of the couplings in the supersymmetric extension of this scenario, and check whether such a scenario is feasible in the light of the precies values of couplings now available from LEP.

hep-ph↗