Electron to selectron pair conversion in a SUSY bubble

In the standard model, energy release in dense stars is severely restricted by the Pauli exclusion principle. However, if, in regions of space of high fermion degeneracy, there is a phase transition to a state of exact supersymmetry (SUSY), fermion to sfermion pair conversion followed by radiative transitions to the Bose ground state could lead to a highly collimated gamma ray burst. We calculate the cross section for electron to selectron pair conversion in a SUSY bubble and construct a monte carlo for the resulting sfermion amplification by stimulated emission.Comment: 13 pages, 4 figures, published version with "with jet production by Bose enhancement" added to titl

Polarization Effects in Chargino Production at High Energy γγ\gamma\gamma Colliders

We investigate the chargino production process $\gamma\gamma\rightarrow\tilde{W}^{+}\tilde{W}^{-}$ at high energy $\gamma\gamma$ colliders in the framework of the minimal supersymmetric standard model (MSSM). Here the high energy $\gamma$ beams are obtained by the backward Compton scattering of the laser flush by the electron in the basic linear TeV $ee$ colliders. We consider the polarization of the laser photons as well as the electron beams. Appropriate beam polarization could be effective to enhance the cross section and for us to extract the signal from the dominant background $\gamma\gamma\rightarrow{W}^{+}{W}^{-}$.Comment: 7 pages, latex , 3 figures are available upon reques

Who violates expectations when? How firms’ growth and dividend reputations affect investors’ reactions to acquisitions

Research summary: We investigate the role of a firm’s dividend and growth reputations in shaping investors’ interpretations of acquisitions as a negative or positive expectation violation. While our findings reveal that both an acquiring firm’s dividend and growth reputations trigger positive investor reactions, they also show that investors react negatively to an acquisition of a target firm with a strong growth reputation when the acquiring firm has a strong dividend reputation. We also find that investors are inclined to give managers “the benefit of the doubt” to the extent that an acquiring firm strategically frames an acquisition announcement in such a way that it provides assurance to investors that the acquisition is meant to exceed investors’ expectations about shareholder value creation. Managerial summary: We study why investors respond to some acquisitions positively and others negatively. We find that the way acquiring and target firms have created shareholder value in the past, and the information conveyed in the acquisition announcements are important determinants of investors’ differential reactions to acquisitions. Our findings show that while investors generally react positively to acquisitions by firms known for creating value either through dividends or growth, their reactions become negative when a firm known for value creation through dividends acquires a target known for value creation through growth. We further find that managers can favorably influence investor reactions by making it salient in the acquisition announcement how the acquisition is intended to exceed investors’ value creation expectations from the acquiring firm

Sfermion Pair Production in Polarized and Unpolarized γγ\gamma\gamma Collisions

We calculate total and differential cross sections for the production of sfermion pairs in photon-photon collisions, including contributions from resolved photons and arbitrary photon polarization. Sfermion production in photon collisions depends only on the sfermion mass and charge. It is thus independent of the details of the SUSY breaking mechanism, but highly sensitive to the sfermion charge. We compare the total cross sections for bremsstrahlung, beamstrahlung, and laser backscattering photons to those in $e^+e^-$ annihilation. We find that the total cross section at a polarized photon collider is larger than the $e^+e^-$ annihilation cross section up to the kinematic limit of the photon collider.Comment: 19 pages, Latex, 18 (e)ps-figure

Dijet resonances, widths and all that

The search for heavy resonances in the dijet channel is part of the on-going physics programme, both at the Tevatron and at the LHC. Lower limits have been placed on the masses of dijet resonances predicted in a wide variety of models. However, across experiments, the search strategy assumes that the effect of the new particles is well-approximated by on-shell production and subsequent decay into a pair of jets. We examine the impact of off-shell effects on such searches, particularly for strongly interacting resonances.Comment: Version published in JHE

CP Violation in the Top-Quark Pair Production at a Next Linear Collider

We provide a detailed, model-independent, study for CP violation effects due to the T-odd top-quark electric dipole moment (EDM) and weak dipole moment (WDM) in the top-quark pair production via $e^+e^-$ and two-photon annihilation at a next $e^+e^-$ linear collider (NLC). There are two methods in detecting CP violation effects in these processes. One method makes use of measurements of various spin correlations in the final decay products of the produced top-quark pair, while the other is to measure various CP-odd polarization asymmetry effects of the initial states. In the $e^+e^-$ case only the first method can be used, and in the $\gamma\gamma$ case both methods can be employed. We provide a complete classification of angular correlations of the $t$ and $\bar{t}$ decay products under CP and CP\tilde{T} which greatly faciliate CP tests in the $e^+e^-$ mode. Concentrating on the second method with the Compton back-scattered high-energetic laser light off the electron or positron beam in the two-photon mode, we construct two CP-odd and CP\tilde{T}-even initial polarization configurations and apply them to investigating CP-violating effects due to the top-quark EDM. With a typical set of experimental parameters at the NLC, we compare the 1-\sigma sensitivities to the top-quark EDM and WDM in the $e^+e^-$ mode and the two-photon mode. Some model expectation values of the T-odd parameters are compared with the results.Comment: 45 pages(LaTeX), 10 eps figures, uses epsfig.st

A study of single sneutrino production in association with fermion pairs at polarised photon colliders

We investigate single sneutrino production in the context of R-parity-violating Supersymmetry at future $\gamma\gamma$ linear colliders. The sneutrino is produced in association with fermion pairs and it is shown that its decays into two further fermions will lead to a clean signal. We also discuss possible backgrounds and the effects of beam polarisation.Comment: 31 pages, LaTeX, 10 postscript figures. Title has been modified. Two new figures and one appendix added. Detailed SM background estimations were made. A new reference added. Version to appear in PR

Verifiable Model of Neutrino Masses from Large Extra Dimensions

We propose a new scenario of neutrino masses with a Higgs triplet $(\xi^{++},\xi^+,\xi^0)$ in a theory of large extra dimensions. Lepton number violation in a distant brane acts as the source of a very small trilinear coupling of $\xi$ to the standard Higgs doublet in our brane. Small realistic Majorana neutrino masses are \underline{naturally} obtained with the fundamental scale $M_* \sim {\cal O}(1)$ TeV, foretelling the possible discovery of $\xi$ (m_\xi\lsim M_*) at future colliders. Decays of $\xi^{++}$ into same-sign dileptons are fixed by the neutrino mass matrix. Observation of $\mu-e$ conversion in nuclei is predicted.Comment: A comment on Tevatron reach and two references added. Discussion and conclusions unchange

Signal and Backgrounds for Leptoquarks at the LHC

We study the potentiality of the CERN Large Hadron Collider (LHC) to unravel the existence of first generation scalar leptoquarks. Working with the most general $SU(2)_L \otimes U(1)_Y$ invariant leptoquark interactions, we analyze in detail the signals and backgrounds that lead to a final state containing a pair $e^+e^-$ and jets. Our results indicate that a machine like the LHC will be able to discover leptoquarks with masses up to 2--3 TeV depending on their couplings.Comment: 37 pages, revtex, uses epsfig.sty (included), 15 figures (included