A joint Fermi-GBM and Swift-BAT analysis of gravitational-wave candidates from the third gravitational-wave observing run

We present Fermi Gamma-ray Burst Monitor (Fermi-GBM) and Swift Burst Alert Telescope (Swift-BAT) searches for gamma-ray/X-ray counterparts to gravitational-wave (GW) candidate events identified during the third observing run of the Advanced LIGO and Advanced Virgo detectors. Using Fermi-GBM onboard triggers and subthreshold gamma-ray burst (GRB) candidates found in the Fermi-GBM ground analyses, the Targeted Search and the Untargeted Search, we investigate whether there are any coincident GRBs associated with the GWs. We also search the Swift-BAT rate data around the GW times to determine whether a GRB counterpart is present. No counterparts are found. Using both the Fermi-GBM Targeted Search and the Swift-BAT search, we calculate flux upper limits and present joint upper limits on the gamma-ray luminosity of each GW. Given these limits, we constrain theoretical models for the emission of gamma rays from binary black hole mergers

Radiative corrections for associated ZH production at future e"+e"- colliders

SIGLEAvailable from TIB Hannover: RA 2999(91-128) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Dependence of electroweak parameters on the definition of the top-quark mass

Electroweak parameters depend on the renormalization scheme (and scale) used to define the top-quark mass. We analyze this dependence in O(#alpha##alpha#_s) by comparing the evaluations in the on-shell and MS schemes. In the case of the W-boson mass predicted from #DELTA#r, we find that the two evaluations differ by not more than 4 MeV when the mass renormalization scale is identified with the top-quark mass. We study also the scale dependence of the MS result. These variations indicate the magnitude of unknown higher-order effects and contribute to the theoretical error of the predictions. (orig.)Available from TIB Hannover: RA 2999(94-036) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Theoretical aspects of standard-model Higgs-boson physics at a future e"+e"-linear collider

The Higgs boson is the missing link of the Standard Model of elementary particle physics. We review its decay properties and production mechanisms at a future e"+e"- linear collider and its e"-e"-, e"#+-##gamma#, and #gamma##gamma# modes, with special emphasis on the influence of quantum corrections. We also discuss how its quantum numbers and couplings can be extracted from the study of appropriate final states. (orig.)Available from TIB Hannover: RA 2999(01-203) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Two loop O(#alpha#_sG_Fm_t"2) corrections to the fermionic decay rates of the standard-model Higgs boson

Low- and intermediate mass Higgs bosons decay preferably into fermion pairs. The one-loop electroweak corrections to the respective decay rates are dominated by a flavour-independent term of O(G_Fm_t"2). We calculate the two-loop gluon correction to this term. It turns out that this correction screens the leading high-m_t behaviour of the one-loop result by roughly 10%. We also present the two-loop QCD correction to the contribution induced by a pair of fourth-generation quarks with arbitrary masses. As expected, the inclusion of the QCD correction considerably reduces the renormalization-scheme dependence of the prediction. (orig.)Available from TIB Hannover: RA 2999(94-083) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Theoretical problems of Higgs-boson physics at the next linear collider

We discuss some theoretical aspects of standard-model (SM) Higgs-boson (H) phenomenology at the next e"+e"- linear collider (NLC) with 300 GeV<or#approx##sq root#s<or#approx#500 GeV. The topics include radiative corrections to H production and decay; the study of the major signals and backgrounds including acceptance cuts, bremsstrahlung, and beamstrahlung; the determination of mass, spin, parity, and charge conjugation of H; and the H discovery limit at #sq root#s=500 GeV. (orig.)Available from TIB Hannover: RA 2999(93-088) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Higgs phenomenology at one loop in the standard model

We present a synopsis of Higgs-boson phenomenology at one loop in the standard model. Two-loop effects are reported on as far as present knowledge goes. The phenomena are classified according to the number of external particles participating in the interaction. The relevant classes correspond to two-, three-, four-, and five-point functions. Two-point functions are the source of indirect evidence for the Higgs boson; three-point functions control its two-body decays and its production through fusion processes at hadron and photon colliders; four-point functions trigger its three-body decays and its associated production with another particle that balances the quantum numbers or serves as a signal; five-point functions mediate Higgs-boson four-body decays and production from intermediate-boson fusion at hadron, ep, and e"+e"- colliders. Of course, the study of quantum corrections to these processes is interesting in its own right, since it provides a deeper insight into the completely untested Higgs sector of the electroweak theory. However, in some cases the effects are very significant and their neglect leads to rather inadequate predictions, e.g., in the case of the H #-># b anti b decay or the gluon-fusion mechanism. The purpose of this article is to deliver a broad review of the quantum effects related to the Higgs boson, to highlight their phenomenological relevance, to list the most important formulae for quick reference, and to generate a rich bibliography, so that the interested reader can find the source of the results. We shall illustrate the effects in numerous figures and investigate various limiting cases, e.g., light or heavy virtual fermions, a heavy Higgs boson, etc. For the reader's convenience, we shall collect the relevant two-, three-, and four-point loop integrals as well as the boson vacuum polarizations and fermion self-energies in a number of appendices. (orig.)SIGLEAvailable from TIB Hannover: RA 2999(93-069) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany)DEGerman

Effective mass scale of new physics in the absence of the Higgs boson

We consider a hypothetical scenario in which the Higgs boson is absent, and attempt to constrain the effective mass scale M_N_P of the new physics that would take its place. Characterizing M_N_P in the simplest manner, we estimate this parameter using recent measurements of sin"2 #theta#_e_f_f"l"e"p"t and M_W. The two determinations of M_N_P are in good agreement and turn out to be close to current estimates for M_H in the standard model (SM). As a by-product, we introduce a basic electroweak correction #DELTA#r_e_f_f and point out that the M_W measurement has become competitive with that of sin"2 #theta#_e_f_f"l"e"p"t in the SM estimates of M_H. (orig.)14 refs.Available from TIB Hannover: RA 2999(99-085) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Prompt J/#psi# production in charged-current deep-inelastic scattering

We calculate the cross section of J/#psi# inclusive production in lepton-nucleon deep-inelastic scattering via the weak charged current within the factorization formalism of nonrelativistic quantum chromodynamics. The hadronic system produced in association with the J/#psi# meson can be of light-quark origin or contain charm. We take into account both direct production and feed-down from directly-produced heavier charmonia. We provide the cross sections of all contributing partonic subprocesses in analytic form. We present theoretical predictions for the J/#psi# transverse-momentum and rapidity distributions, which can be measured in current neutrino-nucleon scattering experiments at CERN and Fermilab, and possibly at the future electron-proton collider THERA at DESY. We find the cross section to be at the edge of observability at DESY HERA. (orig.)Available from TIB Hannover: RA 2999(03-107) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman