Ali Abbasabadi

High energy photon-neutrino interactions

A general decomposition of the amplitudes for the 2 {r_arrow} 2 processes {gamma}{nu} {r_arrow} {gamma}{nu} and {gamma}{gamma} {r_arrow} {nu}{bar {nu}} is obtained using gauge invariance and Bose symmetry. The restrictions implied by this decomposition are investigated for the reaction {gamma}{gamma} {r_arrow} {nu}{bar {nu}} by computing the one-loop helicity amplitudes in the standard model. In the center of mass, where {radical}s = 2{omega}, the cross section grows roughly as {omega}{sup 6} up to the threshold for W-boson production, {radical}s = 2m{sub W}. Astrophysical implications of very high energy photon-neutrino interactions are discussed.

Higgs-photon associated production at hadron colliders

We present cross sections for the reactions p{bar p}{r_arrow}H{gamma} and pp{r_arrow}H{gamma} arising from the subprocess q{bar q}{r_arrow}H{gamma}. The calculation includes the complete one-loop contribution from all light quarks as well as the tree contributions from the light quarks and c and b quarks. These are the main sources of Higgs-photon associated production at hadron colliders. At Fermilab Tevatron energies, the cross section is typically between 0.1thinspfb and 1.0thinspfb for 80thinspGeV{le}m{sub H}{le}160thinspGeV, while at CERN LHC energies it exceeds about 2.0thinspfb over the same range of m{sub H}. While substantial, these cross sections are not large enough to produce a signal which is discernable above the backgrounds from q{bar q}{r_arrow}b{bar b}{gamma} and gg{r_arrow}b{bar b}{gamma}. {copyright} {ital 1998} {ital The American Physical Society}

Radiative Higgs boson decays H → f f ¯ γ

Higgs boson radiative decays of the form

Note on the rare decay of a Higgs boson into photons and a Z boson

H\rightarrow f\bar{f}\gamma

High energy photon-neutrino elastic scattering

are calculated in the Standard Model using the complete one-loop expressions for the decay amplitudes. Contributions to the radiative width from leptons and light quarks are given. We also present

Higgs boson decay to μμ̄γ

e\bar{e}

Higgs boson decay into Z bosons and a photon

invariant mass distributions for

Radiative Higgs Boson Decays H -> f fbar gamma

H\rightarrow e\bar{e}\gamma

Optical activity of neutrinos and antineutrinos

, which illustrate the importance of the photon pole contribution and the effects of the box diagrams.

Photons, neutrinos, and the optical activity

We have calculated the width of the rare decay H{yields}{gamma}{gamma}Z at one-loop level in the standard model for Higgs boson masses in the range 115 GeV{<=}m{sub H}{<=}160 GeV . For this range of Higgs boson masses we find that Z boson is predominantly longitudinally polarized, and the photons have the same helicity. A comparison of the decay width {gamma}(H{yields}{gamma}{gamma}Z) to those of H{yields}{gamma}{gamma} and H{yields}{gamma}Z shows that, for the Higgs boson mass of m{sub H}{approx}135 GeV, the ratios of the decay widths are {gamma}(H{yields}{gamma}{gamma}Z)/{gamma}(H{yields}{gamma}{gamma}){approx}{gamma}(H{yields}{gamma}{gamma}Z)/{gamma}(H{yields}{gamma}Z){approx}10{sup -5}-10{sup -6}.