arXiv subjects

Ali Abbasabadi

Publications and source records attributed to Ali Abbasabadi.

9 recordsLinked to original sources

arXiv2006

Higgs boson decay into Z bosons and a photon

We have performed a one-loop calculation of the width of the rare decay H -> Z Z γin the standard model for Higgs boson masses 190 GeV \leq m_H \leq 250 GeV. We find that the most dominant helicity combinations for the Z bosons and the photon is when one of the Z bosons is longitudinally polarized and the other Z boson and the photon have the same helicity. A comparison of the decay width Γ(H->Z Z γ) to those of H->γγand H->γZ shows that the ratios of the decay widths are Γ(H->Z Z γ) / Γ(H->γγ) ~ Γ(H->Z Z γ) / Γ(H->γZ) ~ 10^{-7}.

hep-ph↗

arXiv2004

A note on the rare decay of a Higgs boson into photons and a $Z$ boson

We have calculated the width of the rare decay $H\toγγZ$ at one-loop level in the standard model for Higgs boson masses in the range $115 {\rm GeV} \leq m_H \leq 160 {\rm GeV}$ . 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 $Γ(H\to γγZ)$ to those of $H\toγγ$ and $H\toγZ$ shows that, for the Higgs boson mass of $m_H \sim 135 \rm{GeV}$, the ratios of the decay widths are $Γ(H\toγγZ) / Γ(H\toγγ) \sim Γ(H\toγγZ) / Γ(H\toγZ) \sim 10^{-5}-10^{-6}$.

hep-ph↗

arXiv2003

Optical activity of neutrinos and antineutrinos

Using the one-loop helicity amplitudes for low-energy $νγ\toνγ$ and $\barνγ\to\barνγ$ scattering in the standard model with massless neutrinos, we study the optical activity of a sea of neutrinos and antineutrinos. In particular, we estimate the values of the index of refraction and rotary power of this medium in the absence of dispersion.

hep-ph↗

arXiv2001

Photons, neutrinos and optical activity

We compute the one-loop helicity amplitudes for low-energy $νγ\toνγ$ scattering and its crossed channels in the standard model with massless neutrinos. In the center of mass, with $\sqrt{s} = 2ω\ll 2m_e$, the cross sections for these $2\to 2$ channels grow roughly as $ω^6$. The scattered photons in the elastic channel are circularly polarized and the net value of the polarization is non-zero. We also present a discussion of the optical activity of a sea of neutrinos and estimate the values of its index of refraction and rotary power.

hep-ph↗

arXiv2000

High energy photon-neutrino elastic scattering

The one-loop helicity amplitudes for the elastic scattering process $γν\toγν$ in the Standard Model are computed at high center of mass energies. A general decomposition of the amplitudes is utilized to investigate the validity of some of the key features of our results. In the center of mass, where $\sqrt{s} = 2ω$, the cross section grows roughly as $ω^6$ to near the threshold for $W$-boson production, $\sqrt{s} = m_W$. Although suppressed at low energies, we find that the elastic cross section exceeds the cross section for $γν\toγγν$ when $\sqrt{s}>13 $ GeV. We demonstrate that the scattered photons are circularly polarized and the net value of the polarization is non-zero. Astrophysical implications of high energy photon-neutrino scattering are discussed.

hep-ph↗

arXiv2000

Higgs boson decay to mu mubar gamma

The Higgs boson decay, H -> mu mubar gamma, is studied in the Standard Model at the tree and one-loop levels. It is shown that for Higgs boson masses above 110 GeV, the contribution to the radiative width from the one-loop level exceeds the contribution from the tree level, and for Higgs boson masses above 140 GeV, it even exceeds the contribution from the tree level decay H -> mu mubar. We also show that the contributions to the radiative decay width from the interference terms between the tree and one-loop diagrams are negligible.

hep-ph↗

arXiv1998

High energy photon-neutrino interactions

A general decomposition of the amplitudes for the $2\to 2$ processes $γν\toγν$ and $γγ\toν\barν$ is obtained using gauge invariance and Bose symmetry. The restrictions implied by this decomposition are investigated for the reaction $γγ\toν\barν$ by computing the one-loop helicity amplitudes in the standard model. In the center of mass, where $\sqrt{s} = 2ω$, the cross section grows roughly as $ω^6$ up to the threshold for $W$-boson production, $\sqrt{s} = 2m_W$. Astrophysical implications of very high energy photon-neutrino interactions are discussed.

hep-ph↗

arXiv1996

Radiative Higgs Boson Decays H -> f fbar gamma

Higgs boson radiative decays of the form $H\rightarrow f\bar{f}γ$ 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 $e\bar{e}$ invariant mass distributions for $H\rightarrow e\bar{e}γ$, which illustrate the importance of the photon pole contribution and the effects of the box diagrams.

hep-ph↗

arXiv1995

Higgs-photon associated production at $e\bar{e}$ colliders

We present complete analytical expressions for the amplitudes of the process $e\bar{e}\rightarrow Hγ$. The calculation is performed using nonlinear gauges, which significantly simplifies both the actual analytical calculation and the check of its gauge invariance. After comparing our results with a previous numerical calculation, we extend the range of Higgs masses and center of mass energies to those appropriate to LEP 200 and a future linear collider.

hep-ph↗