arXiv subjects
Publications and source records attributed to K. J. Abraham.
We analyze the Lipkin Model using effective operator techniques. We present both analytical and numerical results for effective Hamiltonians. The accuracy of the cluster approximation is investigated.
We analyse the one dimensional quartic oscillator using the effective operator methodology of Lee and Suzuki. We reproduce known results for low lying energy eigenvalues.
We examine the possibility of observing exotic top quark decays via $R$-Parity violating SUSY interactions in $e^+e^-$ collisions at $\sqrt{s = 500 GeV$. We present cross-sections for $t\bar t$ production followed by the subsequent decay of either the $t$ or $\overline{t}$ via the $R$-Parity violating interaction while the other undergoes the SM decay. We discuss kinematic cuts that allow the exotic SUSY decays to be detected over standard model backgrounds. Discovery limits for $R$-Parity violating couplings in the top sector are presented assuming an integrated luminosity of $100 fb^{-1}$.
We examine the possibility of observing exotic top quark decays via R-violating SUSY interactions at the Fermilab Tevatron and CERN LHC. We present cross-sections for $t\bar t$ production followed by the subsequent decay of either $t$ or $\bar t$ via the R-violating interaction while the other undergoes the SM decay. With suitable kinematic cuts, we find that the exotic decays can possibly be detected over standard model backgrounds at the future runs of the Tevatron and LHC, but not at Run 1 of the Tevatron due to limited statistics. Discovery limits for R-Violating couplings in the top sector are presented.
In this paper we demonstrate that multi-modal Probability Distribution Functions (PDFs) may be efficiently sampled using an algorithm originally developed for numerical integrations by Monte-Carlo methods. This algorithm can be used to generate an input PDF which can be used as an independence sampler in a Metropolis-Hastings chain to sample otherwise troublesome distributions.Some examples in one two and five dimensions are worked out.
We point out that the so--called 'radiative return' events at LEP2 are suited to the study of nonstandard physics, particularly if the vector bosons are emitted into the central detector region. An effective vertex is constructed which contains the most general gauge invariant eeZGamma interaction and its phenomenological consequences are examined. Low Energy Constraints on the effective vertex are discussed as well.
We study NLO QCD corrections as relevant to hadronic W decay in W pair production at a future 500 GeV electron-positron linac, with particular emphasis on the determination of triple gauge boson vertices. We find that hard gluon bremstrahlung may mimic signatures of anomalous triple gauge boson vertices in certain distributions. The size of these effects can strongly depend on the polarisation of the initial electron positron beams.
We investigate the potential of a high-energy $γγ$ collider to detect an anomalous $\bar t q γ$ coupling from observation of the reaction $γγ\to t\bar q$, $\bar t q$, where $q=c$ or $u$. We find that with $b$-tagging and suitable kinematic cuts this process should be observable if the anomalous coupling $κ/Λ$ is no less than about 0.05/TeV, where $Λ$ is the scale of new physics associated with the anomalous interaction. This improves upon the bound possible from observation of top decays at the Tevatron.
In order to observe a signal of possible CP violation in top-quark couplings, we study top-quark production and decay under the conditions of the Tevatron upgrade. Transverse energy asymmetries sensitive to CP violation are defined. Applying the recently proposed optimal method, we calculate the statistical significance for the direct observation of CP violation in the production and subsequent decay of top quarks.
We study the possibility that the production and decay of light stop squarks at Tevatron can mimic top events. We show that this scenario is very unlikely to explain the anomalously high top production cross sections recently reported by the CDF collaboration.
One loop QCD corrections to hadronic W decay are calculated for arbitrary W polarizations . The results are applied to W pair production and decay at LEP200. We focus on the corrections to angular distributions with particular emphasis on azimuthal distributions and correlations. The relevance of our results to the experimental determination of possible nonstandard triple gauge bosons interactions is discussed.
We investigate the sensitivity of single photon plus missing energy cross-sections at future $e^{+}e^{-}$ linacs to non-standard $WWγ$ couplings. We show that even with conservative estimates of systematic errors there is still considerable sensitivity to anomalous couplings. Analytic expressions for helicity amplitudes are presented.