84 research outputs found
The one-loop renormalization of the MSSM Higgs sector and its application to the neutral scalar Higgs masses
The structure of the Higgs sector in the minimal supersymmetric standard
model is reviewed at the one-loop level. An on-shell renormalization scheme of
the MSSM Higgs sector is presented in detail together with the complete list of
formulae for the neutral Higgs masses at the one-loop level. The results of a
complete one- loop calculation for the mass spectrum of the neutral MSSM Higgs
bosons and the quality of simpler Born-like approximations are discussed for
sfermion and gaugino masses in the range of the electroweak scale.Comment: 32 pages, report KA-THEP-5-199
The Higgs Boson Mass as a Probe of the Minimal Supersymmetric Standard Model
Recently, the LEP collaborations have reported a lower bound on a Standard
Model-like Higgs boson of order 89 GeV. We discuss the implications of this
bound for the minimal supersymmetric extension of the Standard Model (MSSM). In
particular, we show that the lower bound on , which can be obtained
from the presently allowed Higgs boson mass value, becomes stronger than the
one set by the requirement of perturbative consistency of the theory up to
scales of order (associated with the infrared fixed-point solution of
the top quark Yukawa coupling) in a large fraction of the allowed parameter
space. The potentiality of future LEP2 searches to further probe the MSSM
parameter space is also discussed.Comment: 15 pages, 5 figures, LateX, psfi
Power law enhancement of neutrino mixing angles in extra dimensions
We study the renormalization of the -type Majorana neutrino mass
operator in a scenario where there is a compactified extra dimension and the
fields involved correspond to only the standard model particles and their
Kaluza-Klein excitations. We observe that in a two flavour scenario, where one
of the neutrinos is necessarily , it is indeed possible to generate a
large mixing at 100 GeV starting from a very small mixing near the
ultra-violet cutoff 30 TeV. {\em En passant}, we also derive the Higgs
mass upper and lower limits from perturbative unitarity and stability of the
potential, respectively.Comment: Latex, 6 pages, one pslatex figure; v2: clarifying remarks added,
minor typos corrected, references updated, version to appear in Phys. Rev.
Improved full one-loop corrections to A^0 -> \sf_1 \sf_2 and \sf_2 -> \sf_1 A^0
We calculate the full electroweak one-loop corrections to the decay of the
CP-odd Higgs boson A^0 into scalar fermions in the minimal supersymmetric
extension of the Standard Model. For this purpose many parameters of the MSSM
have to be properly renormalized in the on-shell renormalization scheme. We
have also included the SUSY-QCD corrections. For the decay into bottom squarks
and tau sleptons, especially for large \tan\b, the corrections can be very
large making the perturbation expansion unreliable. We solve this problem by an
appropriate definition of the tree-level coupling in terms of running fermion
masses and running trilinear couplings A_f. We also discuss the decay of heavy
scalar fermions into light scalar fermions and A^0. We find that the
corrections can be sizeable and therefore cannot be neglected.Comment: 42 pages, 20 figures (23 eps-files
Running of Gauge Couplings in AdS5 via Deconstruction
Running of gauge couplings on a slice of AdS5 is examined using the
deconstruction set-up. Logarithmic running instead of (linear) power law is
justified when the cutoff is lower than the curvature scale. Most of
interesting features in warped gauge theory including the localization of
Kaluza-Klein modes, the widening of higher Kaluza-Klein spectrum spacing are
well captured within the framework of the deconstruction.Comment: 20 pages, 3 figures, revtex, refereces added and typos corrected; the
version published in JHE
B_{s,d} -> l^+ l^- and K_L -> l^+ l^- in SUSY models with non-minimal sources of flavour mixing
We present a general analysis of B_{s,d}-> l^+ l^- and K_L -> l^+ l^- decays
in supersymmetric models with non-minimal sources of flavour mixing. In spite
of the existing constraints on off-diagonal squark mass terms, these modes
could still receive sizeable corrections, mainly because of Higgs-mediated
FCNCs arising at large tan(beta). The severe limits on scenarios with large
tan(beta) and non-negligible {tilde d}^i_{R(L)}-{d-tilde}^j_{R(L)} mixing
imposed by the present experimental bounds on these modes and Delta B=2
observables are discussed in detail. In particular, we show that scalar-current
contributions to K_L -> l^+ l^- and B-{bar B} mixing set non-trivial
constraints on the possibility that B_s -> l^+ l^- and B_d -> l^+ l^- receive
large corrections.Comment: 18 pages, 4 figures (v2: minor changes, published version
Constraints on the Charged Higgs Sector from the Tevatron Collider Data on Top Quark Decay
The top quark data in the lepton plus channel offers a viable probe
for the charged Higgs boson signal. We analyse the recent Tevatron collider
data in this channel to obtain a significant limit on the mass in the
large region.Comment: 8 pages, LaTeX file; 2 figures included (PS files
High scale mixing unification and large neutrino mixing angles
Starting with the hypothesis that quark and lepton mixings are identical at
or near the GUT scale, we show that the large solar and atmospheric neutrino
mixing angles together with the small reactor angle can be understood
purely as a result of renormalization group evolution. The only requirements
are that the three neutrinos must be quasi degenerate in mass and have same CP
parity. It predicts that the common Majorana mass for the neutrinos must be
larger than 0.1 eV making the idea testable in the currently planned or ongoing
experiments searching for neutrinoless-double-beta decay.Comment: 10 pages, eight figure, two tables; new material added; results
remain unchange
The Higgs Boson Production Cross Section as a Precision Observable?
We investigate what can be learned at a linear collider about the sector of
electroweak symmetry breaking from a precise measurement of the Higgs boson
production cross section through the process e+e- -> hZ. We focus on deviations
from the Standard Model arising in its minimal supersymmetric extension. The
analysis is performed within two realistic future scenarios, taking into
account all prospective experimental errors on supersymmetric particle masses
as well as uncertainties from unknown higher order corrections. We find that
information on tan beta and M_A could be obtained from a cross section
measurement with a precision of 0.5 - 1 %. Alternatively, information could be
obtained on the gaugino mass parameters M_2 and mu if they are relatively
small, M_2, mu approximately 200 GeV.Comment: 13 pages, 3 figures. Discussion on experimental errors enlarged,
references added and updated. Version to appear in Phys. Rev.
Radiative Corrections to Neutrino Mixing and CP Violation in the Minimal Seesaw Model with Leptogenesis
Radiative corrections to neutrino mixing and CP violation are analyzed in the
minimal seesaw model with two heavy right-handed neutrinos. We find that
textures of the effective Majorana neutrino mass matrix are essentially stable
against renormalization effects. Taking account of the
Frampton-Glashow-Yanagida ansatz for the Dirac neutrino Yukawa coupling matrix,
we calculate the running effects of light neutrino masses, lepton flavor mixing
angles and CP-violating phases for both (normal mass hierarchy) and
(inverted mass hierarchy) cases in the standard model and in its
minimal supersymmetric extension. Very instructive predictions for the
cosmological baryon number asymmetry via thermal leptogenesis are also given
with the help of low-energy neutrino mixing quantities.Comment: 21 pages, 6 figures; more references adde
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