856 research outputs found
A New Parametrization of the Seesaw Mechanism and Applications in Supersymmetric Models
We present a new parametrization of the minimal seesaw model, expressing the
heavy-singlet neutrino Dirac Yukawa couplings and Majorana
masses in terms of effective light-neutrino observables and an
auxiliary Hermitian matrix In the minimal supersymmetric version of the
seesaw model, the latter can be related directly to other low-energy
observables, including processes that violate charged lepton flavour and CP.
This parametrization enables one to respect the stringent constraints on
muon-number violation while studying the possible ranges for other observables
by scanning over the allowed parameter space of the model. Conversely, if any
of the lepton-flavour-violating process is observed, this measurement can be
used directly to constrain and As applications, we
study flavour-violating decays and the electric dipole moments of
leptons in the minimal supersymmetric seesaw model.Comment: Important references adde
Composite Quarks and Leptons from Dynamical Supersymmetry Breaking without Messengers
We present new theories of dynamical SUSY breaking in which the strong
interactions that break SUSY also give rise to composite quarks and leptons
with naturally small Yukawa couplings. In these models, SUSY breaking is
communicated directly to the composite fields without ``messenger''
interactions. The compositeness scale can be anywhere between 10 TeV and the
Planck scale. These models can naturally solve the supersymmetric flavor
problem, and generically predict sfermion mass unification independent from
gauge unification.Comment: 27 pages, LaTeX; Clarified flavor symmetry of strong interactions;
corrected overestimate of FCNC's; conclusions strengthene
T-Violation in Decay And Supersymmetry
Measurement of the transverse muon polarization in the decay will be attempted for the first time at the
ongoing KEK E246 experiment and also at a proposed BNL experiment. We provide a
general analysis of how is sensitive to the physical
-violating phases in new physics induced four-Fermi interactions, and then
we calculate the dominant contributions to from squark family
mixings in generic supersymmetric models. Estimates of the upper bounds on
are also given. It is found that a supersymmetry-induced
right-handed quark current from boson exchange gives an upper limit on
as large as a few per cent, whereas with
charged-Higgs-exchange induced pseudoscalar interaction, is no
larger than a few tenths of a per cent. Possible correlations between the muon
polarization measurements in and decays are discussed, and distinctive patterns of
this correlation from squark family-mixings and from the three-Higgs-doublet
model are noted.Comment: Revtex, 29 pages including 4 epsf figure
Composite Higgs Sketch
The coupling of a composite Higgs to the standard model fields can deviate
substantially from the standard model values. In this case perturbative
unitarity might break down before the scale of compositeness is reached, which
would suggest that additional composites should lie well below this scale. In
this paper we account for the presence of an additional spin 1 custodial
triplet of rhos. We examine the implications of requiring perturbative
unitarity up to the compositeness scale and find that one has to be close to
saturating certain unitarity sum rules involving the Higgs and the rho
couplings. Given these restrictions on the parameter space we investigate the
main phenomenological consequences of the spin 1 triplet. We find that they can
substantially enhance the Higgs di-photon rate at the LHC even with a reduced
Higgs coupling to gauge bosons. The main existing LHC bounds arise from
di-boson searches, especially in the experimentally clean channel where the
charged rhos decay to a W-boson and a Z, which then decay leptonically. We find
that a large range of interesting parameter space with 700 GeV < m(rho) < 2 TeV
is currently experimentally viable.Comment: 37 pages, 12 figures; v4: sum rule corrected, conclusions unchange
Global Analysis of the Higgs Candidate with Mass ~ 125 GeV
We analyze the properties of the Higgs candidate with mass ~ 125 GeV
discovered by the CMS and ATLAS Collaborations, constraining the possible
deviations of its couplings from those of a Standard Model Higgs boson. The
CMS, ATLAS and Tevatron data are compatible with Standard Model couplings to
massive gauge bosons and fermions, and disfavour several types of composite
Higgs models unless their couplings resemble those in the Standard Model. We
show that the couplings of the Higgs candidate are consistent with a linear
dependence on particle masses, scaled by the electroweak scale ~ 246 GeV, the
power law and the mass scale both having uncertainties ~ 20%.Comment: 22 pages, 9 figures, v2 incorporates experimental data released
during July 2012 and corrected (and improved) treatment of mass dependence of
coupling
Improved Single Sector Supersymmetry Breaking
Building on recent work by N. Arkani-Hamed and the present authors, we
construct realistic models that break supersymmetry dynamically and give rise
to composite quarks and leptons, all in a single strongly-coupled sector. The
most important improvement compared to earlier models is that the
second-generation composite states correspond to dimension-2 "meson" operators
in the ultraviolet. This leads to a higher scale for flavor physics, and gives
a completely natural suppression of flavor-changing neutral currents. We also
construct models in which the hierarchy of Yukawa couplings is explained by the
dimensionality of composite states. These models provide an interesting and
viable alternative to gravity- and gauge-mediated models. The generic
signatures are unification of scalar masses with different quantum numbers at
the compositeness scale, and lighter gaugino, Higgsino, and third-generation
squark and slepton masses. We also analyze large classes of models that give
rise to both compositeness and supersymmetry breaking, based on gauge theories
with confining, fixed-point, or free-magnetic dynamics.Comment: 34 pages, LaTeX2
Is Large Lepton Mixing Excluded?
The original \bnum -(or -) energy spectrum from the
gravitational collapse of a star has a larger average energy than the spectrum
for \bnue since the opacity of \bnue exeeds that of \bnum (or ).
Flavor neutrino conversion, \bnue \bnum, induced by lepton
mixing results in partial permutation of the original \bnue and \bnum spectra.
An upper bound on the permutation factor, (99 CL) is derived
using the data from SN1987A and the different models of the neutrino burst. The
relation between the permutation factor and the vacuum mixing angle is
established, which leads to the upper bound on this angle. The excluded region,
, covers the regions of large mixing angle
solutions of the solar neutrino problem: ``just-so" and, partly, MSW, as well
as part of region of oscillation space which could be
responsible for the atmospheric muon neutrino deficit. These limits are
sensitive to the predicted neutrino spectrum and can be strengthened as
supernova models improve.Comment: 20 pages, TeX file. For hardcopy with figures contact
[email protected]. Institute for Advanced Study number AST 93/1
Stellar Spin-Orbit Misalignment in a Multiplanet System
Stars hosting hot Jupiters are often observed to have high obliquities,
whereas stars with multiple co-planar planets have been seen to have low
obliquities. This has been interpreted as evidence that hot-Jupiter formation
is linked to dynamical disruption, as opposed to planet migration through a
protoplanetary disk. We used asteroseismology to measure a large obliquity for
Kepler-56, a red giant star hosting two transiting co-planar planets. These
observations show that spin-orbit misalignments are not confined to hot-Jupiter
systems. Misalignments in a broader class of systems had been predicted as a
consequence of torques from wide-orbiting companions, and indeed
radial-velocity measurements revealed a third companion in a wide orbit in the
Kepler-56 system.Comment: Accepted for publication in Science, published online on October 17
2013; PDF includes main article and supplementary materials (65 pages, 27
figures, 7 tables); v2: small correction to author lis
Gauge Singlet Scalars as Cold Dark Matter
In light of recent interest in minimal extensions of the Standard Model and
gauge singlet scalar cold dark matter, we provide an arXiv preprint of the
paper, published as Phys.Rev. D50 (1994) 3637, which presented the first
detailed analysis of gauge singlet scalar cold dark matter.Comment: 37 pages, 11 figures, LaTe
Dynamic Assessment of Baroreflex Control of Heart Rate During Induction of Propofol Anesthesia Using a Point Process Method
In this article, we present a point process method to assess dynamic baroreflex sensitivity (BRS) by estimating the baroreflex gain as focal component of a simplified closed-loop model of the cardiovascular system. Specifically, an inverse Gaussian probability distribution is used to model the heartbeat interval, whereas the instantaneous mean is identified by linear and bilinear bivariate regressions on both the previous RâR intervals (RR) and blood pressure (BP) beat-to-beat measures. The instantaneous baroreflex gain is estimated as the feedback branch of the loop with a point-process filter, while the RRBP feedforward transfer function representing heart contractility and vasculature effects is simultaneously estimated by a recursive least-squares filter. These two closed-loop gains provide a direct assessment of baroreflex control of heart rate (HR). In addition, the dynamic coherence, cross bispectrum, and their power ratio can also be estimated. All statistical indices provide a valuable quantitative assessment of the interaction between heartbeat dynamics and hemodynamics. To illustrate the application, we have applied the proposed point process model to experimental recordings from 11 healthy subjects in order to monitor cardiovascular regulation under propofol anesthesia. We present quantitative results during transient periods, as well as statistical analyses on steady-state epochs before and after propofol administration. Our findings validate the ability of the algorithm to provide a reliable and fast-tracking assessment of BRS, and show a clear overall reduction in baroreflex gain from the baseline period to the start of propofol anesthesia, confirming that instantaneous evaluation of arterial baroreflex control of HR may yield important implications in clinical practice, particularly during anesthesia and in postoperative care.National Institutes of Health (U.S.) (Grant R01-HL084502)National Institutes of Health (U.S.) (Grant K25-NS05758)National Institutes of Health (U.S.) (Grant DP2- OD006454)National Institutes of Health (U.S.) (Grant T32NS048005)National Institutes of Health (U.S.) (Grant T32NS048005)National Institutes of Health (U.S.) (Grant R01-DA015644)Massachusetts General Hospital (Clinical Research Center, UL1 Grant RR025758
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