10,117 research outputs found
Mass-degenerate Higgs bosons at 125 GeV in the Two-Higgs-Doublet Model
The analysis of the Higgs boson data by the ATLAS and CMS Collaborations
appears to exhibit an excess of h --> gamma\gamma events above the Standard
Model (SM) expectations; whereas no significant excess is observed in h --> ZZ*
--> {four lepton} events, albeit with large statistical uncertainty due to the
small data sample. These results (assuming they persist with further data)
could be explained by a pair of nearly mass-degenerate scalars, one of which is
a SM-like Higgs boson and the other is a scalar with suppressed couplings to
W+W- and ZZ. In the two Higgs doublet model, the observed \gamma\gamma and ZZ*
--> {four lepton} data can be reproduced by an approximately degenerate CP-even
(h) and CP-odd (A) Higgs boson for values of \sin(\beta-\alpha) near unity and
0.7 < \tan\beta < 1. An enhanced \gamma\gamma signal can also arise in cases
where m_h ~ m_H, m_H ~ m_A, or m_h ~ m_H ~ m_A. Since the ZZ* --> {four lepton}
signal derives primarily from a SM-like Higgs boson whereas the \gamma\gamma
signal receives contributions from two (or more) nearly mass-degenerate states,
one would expect a slightly different invariant mass peak in the ZZ* --> {four
lepton} and \gamma\gamma channels. The phenomenological consequences of such
models can be tested with additional Higgs data that will be collected at the
LHC in the near future.Comment: 18 pages, 19 pdf figures, v2: references added, v3&v4: added refs and
explanation
Relativistic Quantum Thermodynamics of Ideal Gases in 2 Dimensions
In this work we study the behavior of relativistic ideal Bose and Fermi gases
in two space dimensions. Making use of polylogarithm functions we derive a
closed and unified expression for their densities. It is shown that both type
of gases are essentially inequivalent, and only in the non-relativistic limit
the spinless and equal mass Bose and Fermi gases are equivalent as known in the
literature.Comment: 6 pages, 1 figur
Use of OTSC Device System for Closure of Fistulas in the Alimentary Tract – A Case Series
AbstractObjectiveWe report our experience – a case series with the Over the Scope Clip (OTSC), Bear claw, a novel and new tool for the endoscopic entrapment of tissue for closure of fistula and perforations.DesignSingle-center.SettingTertiary referral academic gastroenterology unit and center for advanced therapeutic endoscopy.Patient
Case I – referred for endoscopic treatment for the closure of gastrocutaneous fistula (GC).Case II – referred for endoscopic treatment for the closure of colo-vaginal fistula.Case III – referred for endoscopic treatment for the closure of GC fistula.InterventionThe OTSC system was mounted on the tip of the scope and passed down to the level of the fistula. The targeted site of the fistula was grasped with the tissue anchoring tripod and pulled into the cap with concomitant scope channel suction. Once the tissue was trapped in the cap, the Bear claw was deployed.Main outcome measurementsNA.ResultsAll patients recovered. No complication or recurrence noted. Case I showed successful results with closure of the fistula. Case II fistula was not closed due to the cavity beneath the fistula probably abscess formation – which prevented the healing of the fistula site despite of the closure with OTSC. Case III fistula did not close successfully due to the larger diameter of the fistula which was greater than 1 cm.ConclusionWith several new devices being introduced, it is difficult to judge the implementation of one tool over the others. This device has shown promising results for fistula closure if used knowing the limitation of the product
Frontostriatal Maturation Predicts Cognitive Control Failure to Appetitive Cues in Adolescents
Adolescent risk-taking is a public health issue that increases the odds of poor lifetime outcomes. One factor thought to influence adolescents' propensity for risk-taking is an enhanced sensitivity to appetitive cues, relative to an immature capacity to exert sufficient cognitive control. We tested this hypothesis by characterizing interactions among ventral striatal, dorsal striatal, and prefrontal cortical regions with varying appetitive load using fMRI scanning. Child, teen, and adult participants performed a go/no-go task with appetitive (happy faces) and neutral cues (calm faces). Impulse control to neutral cues showed linear improvement with age, whereas teens showed a nonlinear reduction in impulse control to appetitive cues. This performance decrement in teens was paralleled by enhanced activity in the ventral striatum. Prefrontal cortical recruitment correlated with overall accuracy and showed a linear response with age for no-go versus go trials. Connectivity analyses identified a ventral frontostriatal circuit including the inferior frontal gyrus and dorsal striatum during no-go versus go trials. Examining recruitment developmentally showed that teens had greater between-subject ventral-dorsal striatal coactivation relative to children and adults for happy no-go versus go trials. These findings implicate exaggerated ventral striatal representation of appetitive cues in adolescents relative to an intermediary cognitive control response. Connectivity and coactivity data suggest these systems communicate at the level of the dorsal striatum differentially across development. Biased responding in this system is one possible mechanism underlying heightened risk-taking during adolescence
Associated production of a light Higgs boson and a chargino pair in the MSSM at linear colliders
In the Minimal Supersymmetric Standard Model (MSSM), we study the light
Higgs-boson radiation off a light-chargino pair in the process e+e- -> h chi^+
chi^- at linear colliders with \sqs=500 GeV. We analyze cross sections in the
regions of the MSSM parameter space where the process can not 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's are allowed,
according to present experimental limits on the Higgs-boson, chargino and
sneutrino masses. We also show how a measurement of the process production rate
could provide a determination of the Higgs-boson couplings to charginos.Comment: 26 pages, 9 figures; figure misplacement fixed; to appear in
Eur.Phys.J.
Phonon Screening of Excitons in Semiconductors: Halide Perovskites and Beyond
The ab initio Bethe-Salpeter equation (BSE) approach, an established method
for the study of excitons in materials, is typically solved in a limit where
only static screening from electrons is captured. Here, we generalize this
framework to also include dynamical screening from phonons at lowest order in
the electron-phonon interaction. We apply this generalized BSE approach to a
series of inorganic lead halide perovskites, CsPbX3, with X = Cl, Br, and I. We
find that inclusion of screening from phonons significantly reduces the
computed exciton binding energies of these systems. By deriving a simple
expression for phonon screening effects, we reveal general trends for the
importance of phonon screening effects in semiconductors and insulators, based
on a hydrogenic exciton model. We demonstrate that the magnitude of the phonon
screening correction in isotropic materials can be reliably predicted using
four material specific parameters: the reduced effective mass, the static and
optical dielectric constants, and the phonon frequency of the most strongly
coupled LO phonon mode. This framework helps to elucidate the importance of
phonon screening and its relation to excitonic properties in a broad class of
semiconductors
Production of neutral scalar Higgs bosons at colliders
We study the production of neutral scalar (CP even) Higgs bosons in the
process by including supersymmetric corrections to the
dominant -channel photon exchange amplitude. In addition to the standard
model and fermion loops, there are substantial contributions from
chargino loops. For some cases, these contributions can exceed those of the
's and ordinary fermions. The cross sections in this channel are generally
one or two orders of magnitude larger than those in the related channel
.Comment: 12 pages RevTeX, 5 postscript figures included, uses epsf.st
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