3,281 research outputs found
A No-Lose Theorem for Higgs Searches at a Future Linear Collider
Assuming perturbativity up to a high energy scale GeV, we
demonstrate that a future linear collider operating at
500 GeV with 500 fb per year (such as the recently
proposed TESLA facility) will detect a Higgs boson signal regardless of the
complexity of the Higgs sector and of how the Higgs bosons decay.Comment: 4 pages, LaTe
Calculable Upper Limit on the Mass of the Lightest Higgs Boson in Any Perturbatively Valid Supersymmetric Theory
We show that there is a calculable upper limit on the mass of the lightest
Higgs boson in any supersymmetric theory that remains perturbative up to a high
scale . There are no restrictions on the Higgs sector, or the gauge group or
particle content. We estimate the value of the upper limit to be m_{\hcirc} <
146 GeV for 100 GeV < < 145 GeV, from all effects except possibly
additional heavy fermions beyond top (which could increase the limit by 0-20
GeV if any existed); for > 145 GeV the limit decreases monotonically. We
expect to be able to decrease the value of the upper limit by at least a few
percent by very careful analysis of the conditions. It is not normal in models
for the actual mass to saturate the upper limit.Comment: 8 pages, UM-TH-92-24, Plain TeX. (One table available by fax on
request to [email protected]
Particle spectrum in the modified NMSSM in the strong Yukawa coupling limit
A theoretical analysis of solutions of renormalisation group equations in the
MSSM corresponding to the quasi-fixed point conditions shows that the mass of
the lightest Higgs boson in this case does not exceed . It
means that a substantial part of the parameter space of the MSSM is practically
excluded by existing experimental data from LEP II. In the NMSSM the upper
bound on the lightest Higgs boson mass reaches its maximum in the strong Yukawa
coupling regime, when Yukawa constants are considerably larger the gauge ones
on the Grand Unification scale. In this paper a particle spectrum in a simple
modification of NMSSM which leads to a self-consistent solution in the
considered region of the parameter space is studied. This model allows one to
get even for comparatively low values of . For an analysis of the Higgs boson spectrum and neutralino spectrum a
method for diagonalisation of mass matrices proposed formerly is used. The mass
of the lightest Higgs boson in this model does not exceed .Comment: 34 pages, 5 figures included, LaTeX 2
Possibility of spontaneous CP violation in the nonminimal supersymmetric standard model with two neutral Higgs singlets
A supersymmetric standard model with two Higgs doublets and two Higgs
singlets is investigated if it can accommodate the possibility of spontaneous
CP violation. Assuming the degeneracy of the scalar quark masses of the third
generation, we find that spontaneous CP violation in the Higgs sector is viable
in our model. In the case of spontaneous CP violation, the masses of the
lightest two neutral Higgs bosons are estimated to be 80 and 125 GeV for some
parameter values in our model, which, are consistent with LEP2 data.Comment: 18 pages, 3figure
Flavour physics constraints in the BMSSM
We study the implications of the presence of the two leading-order,
non-renormalizable operators in the Higgs sector of the MSSM to flavour physics
observables. We identify the constraints of flavour physics on the parameters
of the BMSSM when we: a) focus on a region of parameters for which electroweak
baryogenesis is feasible, b) use a CMSSM-like parametrization, and c) consider
the case of a generic NUHM-type model. We find significant differences as
compared to the standard MSSM case.Comment: 22 pages, 7 figure
Higgs Low-Energy Theorem (and its corrections) in Composite Models
The Higgs low-energy theorem gives a simple and elegant way to estimate the
couplings of the Higgs boson to massless gluons and photons induced by loops of
heavy particles. We extend this theorem to take into account possible nonlinear
Higgs interactions resulting from a strong dynamics at the origin of the
breaking of the electroweak symmetry. We show that, while it approximates with
an accuracy of order a few percents single Higgs production, it receives
corrections of order 50% for double Higgs production. A full one-loop
computation of the gg->hh cross section is explicitly performed in MCHM5, the
minimal composite Higgs model based on the SO(5)/SO(4) coset with the Standard
Model fermions embedded into the fundamental representation of SO(5). In
particular we take into account the contributions of all fermionic resonances,
which give sizeable (negative) corrections to the result obtained considering
only the Higgs nonlinearities. Constraints from electroweak precision and
flavor data on the top partners are analyzed in detail, as well as direct
searches at the LHC for these new fermions called to play a crucial role in the
electroweak symmetry breaking dynamics.Comment: 30 pages + appendices and references, 12 figures. v2: discussion of
flavor constraints improved; references added; electroweak fit updated,
results unchanged. Matches published versio
Measurements of the SUSY Higgs self-couplings and the reconstruction of the Higgs potential
We address the issue of the reconstruction of the scalar potential of a
two-Higgs doublet model having in mind that of the MSSM.
We first consider the general CP conserving dim-4 effective potential. To
fully reconstruct this potential, we show that even if all the Higgs masses and
their couplings to the standard model particles are measured one needs not only
to measure certain trilinear Higgs self-couplings but some of the quartic
couplings as well. We also advocate expressing the Higgs self couplings in the
mass basis. We show explicitly, that in the so-called decoupling limit, the
most easily accessible Higgs self-couplings are given in terms of the Higgs
mass while all other dependencies on the parameters of the general effective
potential are screened. This helps also easily explain how, in the
MSSM, the largest radiative corrections which affect these self couplings are
reabsorbed by using the corrected Higgs mass. We also extend our analysis to
higher order operators in the effective Higgs potential. While the above
screening properties do not hold, we argue that these effects must be small and
may not be measured considering the foreseen poor experimental precision in the
extraction of the SUSY Higgs self-couplings.Comment: 25 pages, 3 figure
Complementarity of the CERN Large Hadron Collider and the International Linear Collider
The next-generation high-energy facilities, the CERN Large Hadron Collider
(LHC) and the prospective International Linear Collider (ILC), are
expected to unravel new structures of matter and forces from the electroweak
scale to the TeV scale. In this report we review the complementary role of LHC
and ILC in drawing a comprehensive and high-precision picture of the mechanism
breaking the electroweak symmetries and generating mass, and the unification of
forces in the frame of supersymmetry.Comment: 14 pages, 17 figures, to be published in "Supersymmetry on the Eve of
the LHC", a special volume of European Physical Journal C, Particles and
Fields (EPJC) in memory of Julius Wes
Scrutinizing LSP Dark Matter at the LHC
We show that LHC experiments might well be able to determine all the
parameters required for a prediction of the present density of thermal LSP
relics from the Big Bang era. If the LSP is an almost pure bino we usually only
need to determine its mass and the mass of the SU(2) singlet sleptons. This
information can be obtained by reconstructing the cascade . The only requirement is that ,
which is true for most of the cosmologically interesting parameter space. If
the LSP has a significant higgsino component, its predicted thermal relic
density is smaller than for an equal--mass bino. We show that in this case
squark decays also produce significant numbers of and
. Reconstructing the corresponding decay cascades then
allows to determine the higgsino component of the LSP
Radiative Corrections to Neutralino and Chargino Masses in the Minimal Supersymmetric Model
We determine the neutralino and chargino masses in the MSSM at one-loop. We
perform a Feynman diagram calculation in the on-shell renormalization scheme,
including quark/squark and lepton/slepton loops. We find generically the
corrections are of order 6%. For a 20 GeV neutralino the corrections can be
larger than 20%. The corrections change the region of
parameter space which is ruled out by LEP data. We demonstrate that, e.g., for
a given and the lower limit on the parameter can shift
by 20 GeV.Comment: 11 pages, JHU-TIPAC-930030, PURD-TH-93-13, uses epsf.sty, 6 uuencoded
postscript figures, added one sentence and a referenc
- âŠ