3,158 research outputs found
Higgs Boson Decays to Neutralinos in Low-Scale Gauge Mediation
We study the decays of a standard model-like MSSM Higgs boson to pairs of
neutralinos, each of which subsequently decays promptly to a photon and a
gravitino. Such decays can arise in supersymmetric scenarios where
supersymmetry breaking is mediated to us by gauge interactions with a
relatively light gauge messenger sector (M_{mess} < 100 TeV). This process
gives rise to a collider signal consisting of a pair of photons and missing
energy. In the present work we investigate the bounds on this scenario within
the minimal supersymmetric standard model from existing collider data. We also
study the prospects for discovering the Higgs boson through this decay mode
with upcoming data from the Tevatron and the LHC.Comment: 18 pages, 5 figures, added references and discussion of neutralino
couplings, same as journal versio
Holomorphic selection rules, the origin of the mu term, and thermal inflation
When an abelian gauge theory with integer charges is spontaneously broken by
the expectation value of a charge Q field, there remains a Z_Q discrete
symmetry. In a supersymmetric theory, holomorphy adds additional constraints on
the operators that can appear in the effective superpotential. As a result,
operators with the same mass dimension but opposite sign charges can have very
different coupling strengths. In the present work we characterize the operator
hierarchies in the effective theory due to holomorphy, and show that there
exist simple relationships between the size of an operator and its mass
dimension and charge. Using such holomorphy-induced operator hierarchies, we
construct a simple model with a naturally small supersymmetric mu term. This
model also provides a concrete realization of late-time thermal inflation,
which has the ability to solve the gravitino and moduli problems of weak-scale
supersymmetry.Comment: 18 pages, 1 figur
An ultra-bright atom laser
We present a novel, ultra-bright atom-laser and ultra-cold thermal atom beam.
Using rf-radiation we strongly couple the magnetic hyperfine levels of 87Rb
atoms in a magnetically trapped Bose-Einstein condensate. At low rf-frequencies
gravity opens a small hole in the trapping potenital and a well collimated,
extremely bright atom laser emerges from just below the condensate. As opposed
to traditional atom lasers based on weak coupling, this technique allows us to
outcouple atoms at an arbitrarily large rate. We demonstrate an increase in
flux per atom in the BEC by a factor of sixteen compared to the brightest
quasi-continuous atom laser. Furthermore, we produce by two orders of magnitude
the coldest thermal atom beam to date (200 nK).Comment: 20 pages, 9 figures, supplementary material online at
http://www.bec.g
Single shot measurement of a silicon single electron transistor
We have fabricated a custom cryogenic Complementary Metal-Oxide-Semiconductor
(CMOS) integrated circuit that has a higher measurement bandwidth compared with
conventional room temperature electronics. This allowed implementing single
shot operations and observe the real-time evolution of the current of a
phosphorous-doped silicon single electron transistor that was irradiated with a
microwave pulse. Relaxation times up to 90 us are observed, suggesting the
presence of well isolated electron excitations within the device. It is
expected that these are associated with long decoherence time and the device
may be suitable for quantum information processing
Ultrasound Measurement of Local Deformation in the Human Free Achilles Tendon Produced by Dynamic Muscle-Induced Loading: A Systematic Review.
Achilles tendinopathy is the most prevalent lower limb tendinopathy, yet it remains poorly understood, with mismatches between observed structure and reported function. Recent studies have hypothesised that Achilles tendon (AT) healthy function is associated with variable deformation across the tendon width during use, focusing on quantifying sub-tendon deformation. Here, the aim of this work was to synthesise recent advances exploring human free AT tissue-level deformation during use. Following PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, PubMed, Embase, Scopus and Web of Science were systematically searched. Study quality and risk of bias were assessed. Thirteen articles were retained, yielding data on free AT deformation patterns. Seven were categorised as high-quality and six as medium-quality studies. Evidence consistently reports that healthy and young tendons deform non-uniformly, with the deeper layer displacing 18%-80% more than the superficial layer. Non-uniformity decreased by 12%-85% with increasing age and by 42%-91% in the presence of injury. There is limited evidence of large effect that AT deformation patterns during dynamic loading are non-uniform and may act as a biomarker of tendon health, risk of injury and rehabilitation impact. Better considered participant recruitment and improved measurement procedures would particularly improve study quality, to explore links between tendon structure, function, aging and disease in distinct populations
Cosmic Strings from Supersymmetric Flat Directions
Flat directions are a generic feature of the scalar potential in
supersymmetric gauge field theories. They can arise, for example, from D-terms
associated with an extra abelian gauge symmetry. Even when supersymmetry is
broken softly, there often remain directions in the scalar field space along
which the potential is almost flat. Upon breaking a gauge symmetry along one of
these almost flat directions, cosmic strings may form. Relative to the standard
cosmic string picture based on the abelian Higgs model, these flat-direction
cosmic strings have the extreme Type-I properties of a thin gauge core
surrounded by a much wider scalar field profile. We perform a comprehensive
study of the microscopic, macroscopic, and observational characteristics of
this class of strings. We find many differences from the standard string
scenario, including stable higher winding mode strings, the dynamical formation
of higher mode strings from lower ones, and a resultant multi-tension scaling
string network in the early universe. These strings are only moderately
constrained by current observations, and their gravitational wave signatures
may be detectable at future gravity wave detectors. Furthermore, there is the
interesting but speculative prospect that the decays of cosmic string loops in
the early universe could be a source of ultra-high energy cosmic rays or
non-thermal dark matter. We also compare the observational signatures of
flat-direction cosmic strings with those of ordinary cosmic strings as well as
(p,q) cosmic strings motivated by superstring theory.Comment: 58 pages, 16 figures, v2. accepted to PRD, added comments about
baryogenesis and boosted decay products from cusp annihilatio
Enhanced Production of Neutron-Rich Rare Isotopes in Peripheral Collisions at Fermi Energies
A large enhancement in the production of neutron-rich projectile residues is
observed in the reactions of a 25 MeV/nucleon 86Kr beam with the neutron rich
124Sn and 64Ni targets relative to the predictions of the EPAX parametrization
of high-energy fragmentation, as well as relative to the reaction with the less
neutron-rich 112Sn target. The data demonstrate the significant effect of the
target neutron-to-proton ratio (N/Z) in peripheral collisions at Fermi
energies. A hybrid model based on a deep-inelastic transfer code (DIT) followed
by a statistical de-excitation code appears to account for part of the observed
large cross sections. The DIT simulation indicates that the production of the
neutron-rich nuclides in these reactions is associated with peripheral nucleon
exchange. In such peripheral encounters, the neutron skins of the neutron-rich
124Sn and 64Ni target nuclei may play an important role. From a practical
viewpoint, such reactions between massive neutron-rich nuclei offer a novel and
attractive synthetic avenue to access extremely neutron-rich rare isotopes
towards the neutron-drip line.Comment: 4 pages, 3 figures, submitted to Phys. Rev. Let
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