arXiv subjects
Publications and source records attributed to B. H. J. McKellar.
Within the framework of Standard Model, the exclusive decay mode $B\to πγγ$ is studied. Although the usual short distance contribution is small compared to the similar $B\to Kγγ$ mode, the process offers the possibility of studying the CP violation, a feature absent in the $B \to K$ counterpart.
Babu studied the neutrino spectrum obtained when one adds a charged singlet and a doubly charged singlet to the standard model particle spectrum. It was found that the neutrinos acquire a mass matrix at the two-loop level which contains one massless eigenstate. The mass matrix of Babu's model depends on an integral over the undetermined loop momenta. We present the exact calculation of this integral.
We report the results of the first computation related to the study of the spectator effects in the rare decay mode $B\to K γγ$ within the framework of Standard Model. It is found that the account of these effects results in the enhancement factor for the short-distance reducible contribution to the branching ratio.
In this paper we shall study the phenomenology of a doubly charged and neutral exchange black hole in an $(n+3)$ extra-dimensional scenario, where the black hole shall be treated a normal quantum field.
If the sterile neutrino mass matrix in an otherwise conventional see-saw model has a rank less than the number of flavors, it is possible to produce pseudo-Dirac neutrinos. For the rank 1 case, 3+2 scenarios devolve naturally, as we show by example. Additionally, we find that the lower rank see-saw suppresses some mass differences, so that small mass differences do not require that the individual masses of each neutrino must also be small.
In spherically symmetric, static spacetime, we show that only j=1/2 fermions can satisfy both Einstein's field equation and Dirac's equation. It is also shown that neutrinos are able to have effective masses and cluster in the galactic halo when they are coupled to a global monopole situated at the galactic core. Astronomical implications of the results are discussed.
An exact representation of the causal QED fermion Green's function, in an arbritrary external electromagnetic field, derived by Fried, Gabellini and McKellar, and which naturally allows for non-perturbative approximations, is here used to calculate non-perturbative approximations to the Green's function in the simple case of a constant external field. Schwinger's famous exact result is obtained as the limit as the order of the approximation approaches infinity.
The modifications induced in the standard weak-lensing formula if Newtonian gravity differs from inverse square law at large distances are studied. The possibility of putting bounds on the mass of gravitons from lensing data is explored. A bound on graviton mass, esitmated to be about 100 Mpc$^{-1}$ is obtained from analysis of some recent data on gravitational lensing.
We derive an improved lattice Hamiltonian for pure gauge theory, coupling arbitrarily distant links in the kinetic term. The level of improvement achieved is examined in variational calculations of the SU(2) specific heat in 2+1 dimensions.
The usual see-saw mechanism for the generation of light neutrino masses is based on the assumption that all of the flavours of right-handed (more properly, sterile) neutrinos are heavy. If the sterile Majorana mass matrix is singular, one or more of the sterile neutrinos will have zero mass before mixing with the active (left-handed) neutrinos and be light after that mixing is introduced. In particular, a rank 1 sterile mass matrix leads naturally to two pseudo-Dirac pairs, one very light active Majorana neutrino and one heavy sterile Majorana neutrino. For any pattern of Dirac masses, there exists a region of parameter space in which the two pseudo-Dirac pairs are nearly degenerate in mass. This, in turn, leads to large amplitude mixing of active states as well as mixing into sterile states.
Recent proposals to study the mass of the "electron" neutrino at a sensitivity of 0.3 eV can be used to place limits on the right handed and scalar charged currents at a level which improves on the present experimental limits. Indeed the neglect of the possibility of such interactions can lead to the inference of an incorrect value for the mass, as we illustrate.
The $O(v^2)$ relativistic correction for inelastic $J/ψ$ photoproduction, in which heavy quark pairs are in the dominant Fock state of the quarkonium, is studied in the framework of NRQCD factorization. An assessment of its significance, particularly in comparison to the color octet contributions, is made. It is found that the impact on the energy distribution is negative in certain regions of phase space. The predictions are compared with photoproduction data from DESY-HERA.
The interference of charge-changing interactions, weaker than the V-A Standard Model (SM) interaction and having a different Lorentz structure, with that SM interaction, can, in principle, produce effects near the end point of the Tritium beta decay spectrum which are of a different character from those produced by the purely kinematic effect of neutrino mass expected in the simplest extension of the SM. We show that the existence of more than one mass eigenstate can lead to interference effects at the end point that are stronger than those occurring over the entire spectrum. We discuss these effects both for the special case of Dirac neutrinos and the more general case of Majorana neutrinos and show that, for the present precision of the experiments, one formula should suffice to express the interference effects in all cases. Implications for "sterile" neutrinos are noted.
We identify a plausible scenario based on quark-lepton symmetry which correlates long baseline oscillations with maximal mixing to sterile neutrinos. The implication for the Sudbury Neutrino Observatory (SNO) is that the neutral current signal will be found to suffer the same suppression from the Standard Solar Model prediction as obtains for the charged current signal. Flavor mixing among active neutrinos is expected to occur on shorter baselines with smaller mixing amplitudes.
We note that off the quark mass shell the operators $(p_i+p_f)_μγ_5$ and $iσ_{μν}(p_i -p_f)^νγ_5$, both of which reduce to $-\vecσ\cdot\vec{E}$ in the non-relativistic limit, are no longer identical. In this paper we explore the effects of this difference in the contribution of these quark electric moments to hadronic electric moments.
The electric and magnetic dipole moments of the rho meson are calculated using the propagators and vertices derived from the QCD Dyson-Schwinger equations. Results obtained from using the Bethe-Salpeter amplitude studied by Chappell, Mitchell and Tandy, and Pichowsky and Lee, are compared. The rho meson EDM is generated through the inclusion of a quark electric dipole moment, which is left as a free variable. These results are compared to the perturbative results to obtain a measure of the effects of quark interactions and confinement. The two dipole moments are also calculated using the phenomenological MIT bag model to provide a further basis for comparison.
We study $J/Ψ$ production at photon-photon colliders, which can be realised with Compton scaterring of laser photons at $e^+e^-$ colliders. We find that the production rate through the color-octet channel is comparable to that through the color-singlet channel. Experimentally the two mechanisms can be studied separately because the processes have different signals.
We use improved lattice actions for glue, light quarks and heavy quarks for which we use lattice NRQCD to compute hadron masses. Our results are in good agreement with experiment, except for charmed hadrons. It seems that charmed quar ks are not well approximated as heavy quarks nor as light quarks.