arXiv subjects
Publications and source records attributed to Prasanta Das.
We make a fresh evaluation of contributions to (g-2) of the muon in the framework of a preonic model with coloured vectorlike leptons and heavy coloured Z bosons and discuss their implications in the light of the recent Brookhaven measurement. It is shown that the observed deviation can be explained within this framework with masses and couplings consistent with all constraints.
In this paper we study how the triviality bound on higgs mass in the context of the SM is modified by a light stabilized radion of the Goldberger-Wise variety. Our approach is inherently perturbative. Including the radion contribution to $\bt(ł)$ and $\bt(g_t)$ to one loop we evolve the higgs self coupling $ł$ from the cut off $Ł(=\vphi)$ down to the EW scale $μ_0 = v$. The triviality bound is obtained by requiring that $ł(Ł) = \sqrt{4 π}$ which is the perturbative limit. We also study the effect of small changes in the UVBC on the triviality bound both in the presence and absence of a light radion.
The paper is being withdrawn because of some theoretical inconsistencies.
In this paper we consider non-minimal couplings of the Standard Model fermions to the vector (trace) and axial vector (pseudo-trace) components of the torsion tensor. We then evaluate the contributions of these vector and axial vector components to the muon anomaly and use the recent precision measurement of the muon anomaly to derive constraints on the torsion parameters.
In this paper we calculate the $(g-2)_μ$ contribution due to a light stabilized radion using the radion couplings both to the kinetic energy and the mass term of the muon. We find that the $(g-2)_μ$ contribution due to radion diverges logarithmically with the cut off. We then show that the bound from precision EW data on radion phenomenology allows a sizable shift in the radion mediated muon anomaly that could be detected or tested with the present precision and certainly with the future precision for measuring muon anomaly.
In this paper we determine the contribution of a light stabilized radion to the weak isospin violating $ρ$ parameter by using an ultraviolet momentum cut off as the regulator. The LEP1 bound on $ρ^{new}$ is then used to derive constraints on the radion mass $\mphi$ and its vev $\vphi$. Finally by using the beta function of the higgs self coupling we have determined a lower bound on the higgs mass from the rho parameter constraints on $\mphi$ and $\vphi$. Our results show that for $\mphi <$ 600 GeV the rho parameter bound on $m_h$ is stronger than the present direct bound from LEPII.
In this brief report we show that tadpole diagrams due to KK modes of the graviton and radion do not contribute to the vectorial isospin breaking $ρ$ parameter. Our result is fairly general and it holds both for ADD and RS type scenarios. It shows that the difference between the results of different publications on this subject is not due to some of them not having considered tadpole diagrams in estimating the contribution to the $ρ$ parameter.
In this paper we determine how the beta function for the top Yukawa coupling to one loop is modified by a light stabilized radion in the Randall-Sundrum model. We then use this beta function together with β(λ) to deteremine lower bounds on the radion vev <ϕ> for different values of λ(m_z) and m_ϕ by demanding that both g_t(μ) and λ(μ) should remain perturbative from m_z up ot the cut off Λ. We find that the lower bounds on <ϕ> that follow from the condition λ(Λ)<\sqrt{4π} nearly agree with those that follow from g_t(Λ)<\sqrt{4π}. We have also determined the critical value of <ϕ> for different values of λ(m_z) and m_ϕ from the line of fixed points which is given by β(g_t)=0.
In this paper we determine how the beta funtion of the higgs self coupling λat one loop order is modified by a light stabilized radion in the Randall-Sundrum model. We then use the modified beta function to derive a lower bound on the radion vev <ϕ>, both for perturbative and non-perturbative values of λat the ultra violet cut off Λ. The lower bound on <ϕ> is obtained by demanding that the renormalized coupling λ(μ) at μ=100 GeV be consistent with the present experimental bound of 110 GeV on the higgs mass from LEP2 searches. We also show that if λ(Λ) is sufficiently small then an upper bound on <ϕ> can be determined by requiring that β(λ)be positive over the relevant momentum range.
Low energy string theory predicts the existence of an axion field which can lead to cosmic birefringence. We solve the electromagnetic wave equations in the presence of such an axion and a dilaton field in order to determine their effect on the polarization of light. We find that the presence of dilaton field leads to a nontrivial modification of the final result. We comment on the possibility of discovering such an effect by observations of radio wave polarizations from distant radio galaxies and quasars. We have also determined the limits on the string theory parameters that are imposed by the current polarization data from distant quasars and radio galaxies.
In models with large extra dimensions, where quantum gravity effects become strong at the TeV scale, the rho-parameter can receive large contributions from one-loop diagrams involving exchange of multiple graviton and dilaton states. These contributions are computed, taking into account cancellation of spurious infrared divergences, and the (finite) results for d = 5 and 6 are compared with current experimental data. It is shown that 5 large extra dimensions are incompatible with the data and d = 6 is severely constrained.
We study recent data on deep inelastic e^+ p scattering at HERA to constrain the parameters of a Randall-Sundrum-type scenario of quantum gravity with a small extra dimension and a non-factorable geometry.
We study the $SU(3)_L\otimes U(1)_X$ extension of the Standard model with a strong U(1) coupling. We argue that current experiments limit this coupling to be relatively large. The model is dynamically broken to the Standard $SU(2)_L \otimes U(1)$ model at the scale of a few TeV with all the extra gauge bosons and the exotic quarks acquiring masses much larger than the scale of electroweak symmetry breaking. Furthermore we find that the model leads to large dynamical mass of the top quark and hence also breaks the electroweak gauge symmetry. It therefore leads to large dynamical effects within the Standard model and can partially replace the Higgs interactions.