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G. Jikia

Publications and source records attributed to G. Jikia.

17 recordsLinked to original sources
arXiv2004

Higgs Self-Coupling in gamma-gamma Collisions

To establish the Higgs mechanism experimentally, one has to determine the Higgs self-interaction potential responsible for the electroweak symmetry breaking. This requires a measurement of the trilinear and quadrilinear self-couplings of the Higgs particle, as predicted by the Standard Model (SM). We propose to measure the trilinear Higgs self-coupling in gamma-gamma collisions just above the kinematic threshold E_thr = 2M_H, where M_H is the Higgs mass. Our calculation reveals that the sensitivity of the cross-section sigma(gamma gamma -> HH) to the Higgs self-coupling is maximal near the 2M_H threshold for M_H = 115-150 GeV, and is larger than the sensitivities of sigma(e+e- -> ZHH) and sigma(e+e- -> nu nu HH) to this coupling for 2E_e < 700 GeV. We envisage to (a) study gamma gamma -> H by constructing an X-band e-e- linac and a terawatt laser system in order to produce Compton-scattered gamma-ray beams for a 160-GeV photon collider (2E_e = 200 GeV); (b) add a positron source and repeat all measurements done at LEP and SLC with much better precision; and (c) subsequently install 70-MeV/m rf cavities in order to study e+e- -> H+Z, e+e- -> tt and gamma gamma -> H+H at 2E_e = 350 GeV. The total length of the linac would be about 7 km.

hep-ph↗
arXiv2001

Gold-plated processes at photon colliders

We review the most important topics and objectives of the physics program of the gamma-gamma, gamma-electron collider (photon collider) option for an e+e- linear collider.

hep-ph↗
arXiv2001

Light Higgs Production at a Photon Collider

We present a preliminary study of the production of a light Higgs boson with a mass between 120 and 160 GeV in photon-photon collisions at a Compton collider. The event generator for the backgrounds to a Higgs signal due to bbbar and ccbar heavy quark pair production in polarized Gamma-Gamma collisions is based on a complete next-to-leading order (NLO) perturbative QCD calculation. For J_z=0 the large double-logarithmic corrections up to four loops are also included. It is shown that the two-photon width of the Higgs boson can be measured with high statistical accuracy of about 2-10% for integrated Gamma-Gamma luminosity in the hard part of the spectrum of 43 fb-1. From this result the total Higgs boson width can be derived in a model independent way.

hep-ex↗
arXiv2000

Three-Loop Leading Top Mass Contributions to the rho Parameter

We present analytical results for the leading contributions of the top quark to the electroweak rho parameter at order GF^3 Mt^6 and GF^2 Mt^4 alpha_s. The Higgs boson and the gauge bosons are taken to be massless in this limit. The correction of order GF^3 Mt^6 is found to be sizeable in comparison to the the leading two-loop GF^2 Mt^4 correction, however it is much smaller than the subleading GF^2 Mt^2 MZ^2 correction.

hep-ph↗
arXiv1999

Light Higgs production at the Compton Collider

We have studied the production of a light Higgs boson with a mass of 120 GeV in photon-photon collisions at a Compton collider. The event generator for the backgrounds to a Higgs signal due to bbbar and ccbar heavy quark pair production in polarized gamma-gamma collisions is based on a complete next-to-leading order (NLO) perturbative QCD calculation. For J_z=0 the large double-logarithmic corrections up to four loops are also included. It is shown that the two-photon width of the Higgs boson can be measured with high statistical accuracy of about 2 % for integrated gamma-gamma luminosity in the hard part of the spectrum of 40 fb**-1. As a result the total Higgs boson width can be calculated in a model independent way to an accuracy of about 14 %

hep-ph↗
arXiv1998

Two-loop large Higgs mass corrections to electroweak gauge boson quartic couplings

The two-loop corrections to the electroweak gauge bosons quartic couplings growing quadratically with the Higgs boson mass are calculated in the Standard Model in the limit of large Higgs mass. The corrections to WWWW, WWZZ and ZZZZ four-vertices are found to be an order of magnitude larger than the two-loop m_H^2 corrections to light fermion and triple gauge boson vertices. For a heavy Higgs boson with a mass around 1 TeV the corrections are at the several percent level and in principle could be observed experimentally.

hep-ph↗
arXiv1997

An Interaction Region for Gamma-Gamma and Gamma-Electron Collisions at TESLA/SBLC

Linear colliders offer unique opportunities to study gamma-gamma (gg), gamma-electron (ge) interactions. Using the laser backscattering method one can obtain gg, ge colliding beams with an energy and luminosity comparable to that in e+e- collisions. This work is a part of the Conceptual Design of TESLA/SBLC linear colliders describing a second interaction region for gg, ge collisions. We consider here possible physics in high energy gg, ge collisions, e -> g conversion, requirements to lasers, collision schemes, attainable luminosities, backgrounds, possible lasers, optics at the interaction region and other associated problems.

hep-ex↗
arXiv1997

Physics at the Photon Linear Collider

The physics prospects of the high energy Photon Linear Collider are reviewed, emphasizing its potential to study the symmetry breaking sector, including Higgs searches and precision anomalous W couplings measurements.

hep-ph↗
arXiv1996

Electroweak O(alpha) Corrections to W+W- Pair Production in Polarized gamma-gamma Collisions

Full O(alpha) electroweak corrections for gamma-gamma-> W+W- are calculated including virtual corrections, soft and hard real photon and Z-boson emission. The corrections are quite large ranging from -2.5% at 500 GeV to -18% at 2 TeV, |cosθ^\pm| < cos(10^\circ). Contributions from real photon and Z-boson emission are important at high energies where they partly cancel large negative contribution originating from virtual bosonic corrections. Precision measurements that intend to uncover physics beyond the standard model must necessarily make use of the full standard model predictions including O(alpha) corrections.

hep-ph↗
arXiv1996

Analytic evaluation of two-loop renormalization constants of enhanced electroweak strength in the Higgs sector of the Standard Model

We calculate renormalization constants Z_H, Z_w, the Higgs and W-boson mass and tadpole counterterms in the on-mass-shell renormalization scheme to two loops in the heavy-Higgs-boson limit m_H >> M_W. Explicit analytic formulae are presented for the two-loop integrals with masses, which are not known in the literature. As an application, the analytic expression for the two-loop leading correction to the fermionic Higgs boson width is obtained.

hep-ph↗
arXiv1995

Study of the Strongly Interacting Higgs Physics Model with Heavy Fermions

We study the effect of a possible fourth heavy generation of fermions on the Higgs sector of the standard model. We show, from the violation of elastic unitarity, that the scale of strong interactions is well below 1 TeV even with a Higgs mass as low as 500 GeV provided the fourth generation fermion mass is equal or larger than the Higgs mass. The diagonal Pade approximant method is then used to unitarize the partial wave amplitudes. It is found that, for the fourth generation fermion masses which are comparable to or larger than the Higgs mass, the Landau ghosts in the I=0 and I=2 channels of the reconstructed amplitudes move too close to the physical region to be accepted.

hep-ph↗
arXiv1993

Photon-Photon Scattering at the Photon Linear Collider

Photon-photon scattering at the Photon Linear Collider is considered. Explicit formulas for helicity amplitudes due to $W$ boson loops are presented. It is shown that photon-photon scattering should be easily observable at PLC and separation of the $W$ loop contribution (which dominates at high energies) will be possible at $e^+e^-$ c.m. energy of 500~GeV or higher.

hep-ph↗
arXiv1993

$γZ$ Pair Production at the Photon Linear Collider

$γγ\toγZ$ scattering at the Photon Linear Collider is considered. Explicit formulas for helicity amplitudes due to $W$ boson loops are presented. It is shown that the $Zγ$ pair production will be easily observable at PLC and separation of the $W$ loop contribution will be possible at $e^+e^-$ c.m. energy of 300~GeV or higher.

hep-ph↗