14 research outputs found
Constraining Supersymmetry
We review constraints on the minimal supersymmetric extension of the Standard
Model (MSSM) coming from direct searches at accelerators such as LEP, indirect
measurements such as b -> s gamma decay and the anomalous magnetic moment of
the muon. The recently corrected sign of pole light-by-light scattering
contributions to the latter is taken into account. We combine these constraints
with those due to the cosmological density of stable supersymmetric relic
particles. The possible indications on the supersymmetric mass scale provided
by fine-tuning arguments are reviewed critically. We discuss briefly the
prospects for future accelerator searches for supersymmetry.Comment: 21 LaTeX pages, 9 eps figures, Invited Contribution to the New
Journal of Physics Focus Issue on Supersymmetr
Direct Detection of Dark Matter in Supersymmetric Models
We evaluate neutralino-nucleon scattering rates in several well-motivated
supersymmetric models, and compare against constraints on the neutralino relic
density, BF( b\to s\gamma ) as well as the muon anomalous magnetic moment a_\mu
. In the mSUGRA model, the indirect constraints favor the hyperbolic
branch/focus point (HB/FP) region of parameter space, and in fact this region
is just where neutralino-nucleon scattering rates are high enough to be
detected in direct dark matter search experiments! In Yukawa unified SUSY
SO(10) models with scalar mass non-universality, the relic density of
neutralinos is almost always above experimental bounds, while the corresponding
direct detection rates are below experimental levels. Conversely, in five
dimensional SO(10) models where gauge symmetry breaking is the result of
compactification of the extra dimension, and supersymmetry breaking is
communicated via gaugino mediation, the relic density is quite low, while
direct detection rates can be substantial.Comment: 25 page latex file including 18 EPS figures; revised version with
references added and cross sections rescaled; figures changed. A copy of the
paper with better resolution figures can be found at
http://www.hep.fsu.edu/~belyaev/projects/directz1
Finite Unified Theories and the Higgs boson
All-loop Finite Unified Theories (FUTs) are very interesting N = 1
supersymmetric Grand Unified Theories (GUTs) realising an old field theory
dream, and moreover have a remarkable predictive power due to the required
reduction of couplings. Based on this theoretical framework phenomenologically
consistent FUTs have been constructed. Here we review two FUT models based on
the SU(5) gauge group, which can be seen as special, restricted and thus very
predictive versions of the MSSM. We show that from the requirement of correct
prediction of quark masses and other experimental constraints a light
Higgs-boson mass in the range M_h ~ 121 - 126 GeV is predicted, in striking
agreement with recent experimental results from ATLAS and CMS. The model
furthermore naturally predicts a relatively heavy spectrum with colored
supersymmetric particles above ~ 1.5 TeV in agreement with the non-observation
of those particles at the LHC.Comment: 13 pages, 5 figures. Proceedings devoted to the Scientific and Human
Legacy of Julius Wess, initiated by the JW2011 Workshop, August 27 - 28,
2011, Donji Milanovac, Serbi
Measurements of the branching fractions for decays at Belle II
This paper reports a study of decays using
fb of data collected during 2019--2020 by the Belle II experiment at the
SuperKEKB asymmetric-energy collider, corresponding to events. We find , ,
, and signal events in the decay modes , ,
, and , respectively. The uncertainties quoted for the
signal yield are statistical only. We report the branching fractions of these
decays: where the first
uncertainty is statistical, and the second is systematic. The results are
consistent with world-average values
The reactions π π → π π and γ γ → π π in χ PT with an isosinglet scalar resonance
The lowest-lying resonance in the QCD spectrum is the isoscalar
meson, also known as the . We augment SU(2) chiral
perturbation theory (PT) by including the meson as an additional
explicit degree of freedom, as proposed by Soto, Talavera, and Tarr\'us and
others. In this effective field theory, denoted PT, the
meson's well-established mass and decay width are not sufficient to properly
renormalize its self energy. At another low-energy constant
appears in the dressed -meson propagator; we adjust it so that the
isoscalar pion-pion scattering length is also reproduced. We compare the
resulting amplitudes for the and
reactions to data from threshold through the
energies at which the -meson resonance affects observables. The
leading-order (LO) amplitude reproduces the -meson pole
position, the isoscalar scattering lengths and scattering
and data up to GeV.
It also yields a amplitude that obeys the Ward
identity. The value obtained for the polarizability is, however, only
slightly larger than that obtained in standard PT.Comment: 17 pages, 7 figures. This version, which will be published in
European Physical Journal A, contains clarification and more explanation of
several points, as well as additional reference
Search for B⁺→K⁺ν Decays Using an Inclusive Tagging Method at Belle II
A search for the flavor-changing neutral-current decay B→Kν is performed at the Belle II experiment at the SuperKEKB asymmetric energy electron-positron collider. The data sample corresponds to an integrated luminosity of 63 fb collected at the Υ(4S) resonance and a sample of 9 fb collected at an energy 60 MeV below the resonance. Because the measurable decay signature involves only a single charged kaon, a novel measurement approach is used that exploits not only the properties of the B→K+ν¯ν decay, but also the inclusive properties of the other B meson in the Υ(4S)→B event, to suppress the background from other B meson decays and light-quark pair production. This inclusive tagging approach offers a higher signal efficiency compared to previous searches. No significant signal is observed. An upper limit on the branching fraction of B→Kν of 4.1×10 is set at the 90% confidence level