1,721,031 research outputs found
Associated production of a light Higgs boson and a chargino pair in the MSSM at linear colliders
Full text linkIn the minimal supersymmetric standard model (MSSM), we study the light Higgs boson radiation off a light-chargino pair in the process e+e−h1+1− at linear colliders with s=500Gev GeV. We analyze cross sections in the regions of the MSSM parameter space where the process e+e−h1+1− cannot proceed via on-shell production and subsequent decay of either heavier charginos or the pseudoscalar Higgs boson A. Cross sections up to a few fb are allowed, according to present experimental limits on the Higgs boson, chargino and sneutrino masses. We also show how a measurement of the e+e−h1+1− production rate could provide a determination of the Higgs boson couplings to charginos
A radiatively improved fermiophobic Higgs boson scenario
No full textThe naive fermiophobic scenario is unstable under radiative corrections, due to the chiral-symmetry breaking induced by fermion mass terms. In a recent study, the problem of including the radiative corrections has been tackled via an effective field theory approach. The renormalized Yukawa couplings are assumed to vanish at a high energy scale , and their values at the electroweak scale are computed via modified Renormalization Group Equations. We show that, in case a fermiophobic Higgs scenario shows up at the LHC, a linear collider program will be needed to accurately measure the radiative Yukawa structure, and consequently constrain the Lambda scale
Standard Model Processes at LEP2
No full textWe present the results obtained by the Standard Model Process group in the CERN Workshop "Physics at LEP2" (1994/95)
Z gamma H vertex effects in Higgs-boson production at future e gamma linear colliders
No full textOne-loop production of a Higgs boson in e gamma collisions at future accelerators is studied via the process e gamma-->eH, for intermediate Higgs-boson masses. Exact cross sections, including the possibility of longitudinally polarized initial beams, are presented. Confirming previous estimates made in the Weizsacker-Williams approximation, they an found to be more than 2 orders of magnitude larger than the cross sections for the crossed process e(+)e(-)-->H gamma, in the energy range root s=(0.5-2) TeV. We show that, not only does e gamma-->eH have a similar potential as the gamma gamma-->H process for testing the one-loop gamma gamma H vertex, but, by requiring a final electron tagged at a large angle in e gamma-eH, the He production provides an excellent way of testing the Z gamma H vertex, too. Kinematical distributions for the e gamma-->eH-->e() process with a tagged final electron are analyzed, and strategies for controlling the main irreducible background are found. Initial-state-radiation effects are checked to be within a few percent
Virtual graviton exchanges at the Z pole in large extra dimensions
No full textIn the framework of quantum gravity propagating in large extra dimensions, the effects of virtual Kaluza-Klein gravitons on the imaginary part of the amplitude of the process e(+)e(-) --> f (f) over bar are analyzed at the Z pole. Notably, the interference of the almost-continuous spectrum of the KK gravitons with the standard model resonant amplitude is finite and predictable in terms of the fundamental D-dimensional Planck scale M-D. We find that, while the virtual-graviton effect on total cross sections vanishes at tree-level, both angular and polarization asymmetries are modified by terms whose relative effect is at most of order 10(-4) for M-D > 1 TeV. Possible shifts in M-Z, due to the changes in Breit-Wigner line shape are also discussed. (C) 2002 Elsevier Science B.V. All rights reserved
Effective Yukawa couplings and flavor-changing Higgs boson decays at linear colliders
No full textWe analyze the advantages of a linear-collider program for testing a recent theoretical proposal where the Higgs-boson Yukawa couplings are radiatively generated, keeping unchanged the standard-model mechanism for electroweak-gauge-symmetry breaking. Fermion masses arise at a large energy scale through an unknown mechanism, and the standard model at the electroweak scale is regarded as an effective field theory. In this scenario, Higgs boson decays into photons and electroweak gauge-boson pairs are considerably enhanced for a light Higgs boson, which makes a signal observation at the LHC straightforward. On the other hand, the clean environment of a linear collider is required to directly probe the radiative fermionic sector of the Higgs boson couplings. Also, we show that the flavor-changing Higgs-boson decays are dramatically enhanced with respect to the standard model. In particular, we find a measurable branching ratio in the range (10^{-4}-10^{-3}) for the decay H\to bs for a Higgs boson lighter than 140 GeV, depending on the high-energy scale where Yukawa couplings vanish. We present a detailed analysis of the Higgs boson production cross sections at linear colliders for interesting decay signatures, as well as branching-ratio correlations for different flavor-conserving/nonconserving fermionic decays
Gravitational decays of heavy particles in large extra dimensions
No full textIn the framework of quantum gravity propagating in large extra dimensions, we analyze the inclusive radiative emission of Kaluza-Klein spin-2 gravitons in the two-fermions decays of massive gauge bosons, heavy quarks, Higgs bosons, and in the two-massive gauge bosons decay of Higgs bosons. We provide analytical expressions for the square modulus of amplitudes summed over polarizations, and numerical results for the widths and branching ratios. The corresponding decays in the , top quark, and Higgs boson sectors of the standard model are analyzed in the light of present and future experiments.In the framework of quantum gravity propagating in large extra dimensions, we analyze the inclusive radiative emission of Kaluza-Klein spin-2 gravitons in the two-fermions decays of massive gauge bosons, heavy quarks, Higgs bosons, and in the two-massive gauge bosons decay of Higgs bosons. We provide analytical expressions for the square modulus of amplitudes summed over polarizations, and numerical results for the widths and branching ratios. The corresponding decays in the Z, top quark, and Higgs boson sectors of the standard model are analyzed in the light of present and future experiments.In the framework of quantum gravity propagating in large extra dimensions, we analyze the inclusive radiative emission of Kaluza–Klein spin-2 gravitons in the two-fermions decays of massive gauge bosons, heavy quarks, Higgs bosons, and in the two-massive gauge bosons decay of Higgs bosons. We provide analytical expressions for the square modulus of amplitudes summed over polarizations, and numerical results for the widths and branching ratios. The corresponding decays in the Z , top quark, and Higgs boson sectors of the standard model are analyzed in the light of present and future experiments
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