3,470 research outputs found
A little more Gauge Mediation and the light Higgs mass
We consider minimal models of gauge mediated supersymmetry breaking with an
extra factor in addition to the Standard Model gauge group. A
charged, Standard Model singlet is assumed to be present which allows for an
additional NMSSM like coupling, . The U(1) is assumed to be
flavour universal. Anomaly cancellation in the MSSM sector requires additional
coloured degrees of freedom. The field can get a large vacuum expectation
value along with consistent electroweak symmetry breaking. It is shown that the
lightest CP even Higgs boson can attain mass of the order of 125 GeV.Comment: 29 pages, 7 Figures; v2: updated references 30 pages, minor wordings
modified, to appear in Nucl. Phys.
Neutrino Mass Constraints on R violation and HERA anomaly
R parity violating trilinear couplings of the minimal
supersymmetric standard model (MSSM) are constrained from the limit on the
electron neutrino mass. Strong limits on these couplings follow from the
earlier neglected contribution due to sneutrino vacuum expectation values. The
limits on most of the couplings derived here are stronger than
the existing ones for a wide range in parameters of MSSM. These limits strongly
constrain the interpretation of recent HERA results in scattering in
terms of production of squarks through violating couplings. In particular,
the interpretation in terms of production off strange quark as
suggested recently is not viable for wide ranges in MSSM parameters.Comment: 15 pages with 5 figures, minor typos corrected and a new reference
adde
Gravitational rescue of minimal gauge mediation
Gravity mediation supersymmetry breaking become comparable to gauge mediated
supersymmetry breaking contributions when messenger masses are close to the GUT
scale. By suitably tuning the gravity contributions one can then modify the
soft supersymmetry breaking sector to generate a large stop mixing parameter
and a light higgs mass of 125 GeV. In this kind of hybrid models, however the
nice features of gauge mediation like flavour conservation etc, are lost. To
preserve the nice features, gravitational contributions should become important
for lighter messenger masses and should be important only for certain fields.
This is possible when the hidden sector contains multiple (at least two)
spurions with hierarchical vaccum expectation values. In this case, the
gravitational contribtutions can be organised to be `just right'. We present a
complete model with two spurion hidden sector where the gravitational
contribution is from a warped flavour model in a Randall-Sundrum setting. Along
the way, we present simple expressions to handle renormalisation group
equations when supersymmetry is broken by two different sectors at two
different scales.Comment: 24 Pages, 3 figures, Detailed discussions on flavour violation
included, added figure and references, Matches published versio
Anatomy of Higgs mass in Supersymmetric Inverse Seesaw Models
We compute the one loop corrections to the CP even Higgs mass matrix in the
supersymmetric inverse seesaw model to single out the different cases where the
radiative corrections from the neutrino sector could become important. It is
found that there could be a significant enhancement in the Higgs mass even for
Dirac neutrino masses of (30) GeV if the left-handed sneutrino
soft mass is comparable or larger than the right-handed neutrino mass. In the
case where right-handed neutrino masses are significantly larger than the
supersymmety breaking scale, the corrections can utmost account to an upward
shift of 3 GeV. For very heavy multi TeV sneutrinos, the corrections replicate
the stop corrections at 1-loop. We further show that general gauge mediation
with inverse seesaw model naturally accommodates a 125 GeV Higgs with TeV scale
stops.Comment: 18 pages, 6 figure
Proximity-induced supercurrent through topological insulator based nanowires for quantum computation studies
Proximity induced superconducting energy gap in the surface states of
topological insulators has been predicted to host the much wanted Majorana
fermions for fault tolerant quantum computation. Recent theoretically proposed
architectures for topological quantum computation via Majoranas are based on
large networks of Kitaevs one dimensional quantum wires, which pose a huge
experimental challenge in terms of scalability of the current single nanowire
based devices. Here, we address this problem by realizing robust
superconductivity in junctions of fabricated topological insulator Bi2Se3
nanowires proximity coupled to conventional s wave superconducting W
electrodes. Milling technique possesses great potential in fabrication of any
desired shapes and structures at nanoscale level, and therefore can be
effectively utilized to scale up the existing single nanowire based design into
nanowire based network architectures. We demonstrate the dominant role of
ballistic topological surface states in propagating the long range proximity
induced superconducting order with high IcRN product in long Bi2Se3 junctions.
Large upper critical magnetic fields exceeding the Chandrasekhar Clogston limit
suggests the existence of robust superconducting order with spin triplet cooper
pairing. An unconventional inverse dependence of IcRN product on the width of
the nanowire junction was also observed.Comment: 12 page
Quantum-limited amplification and parametric instability in the reversed dissipation regime of cavity optomechanics
Cavity optomechanical phenomena, such as cooling, amplification or
optomechanically induced transparency, emerge due to a strong imbalance in the
dissipation rates of the parametrically coupled electromagnetic and mechanical
resonators. Here we analyze the reversed dissipation regime where the
mechanical energy relaxation rate exceeds the energy decay rate of the
electromagnetic cavity. We demonstrate that this regime allows for
mechanically-induced amplification (or cooling) of the electromagnetic mode.
Gain, bandwidth, and added noise of this electromagnetic amplifier are derived
and compared to amplification in the normal dissipation regime. In addition, we
analyze the parametric instability, i.e. optomechanical Brillouin lasing, and
contrast it to conventional optomechanical phonon lasing. Finally, we propose
an experimental scheme that realizes the reversed dissipation regime using
parametric coupling and optomechanical cooling with a second electromagnetic
mode enabling quantum-limited amplification. Recent advances in high-Q
superconducting microwave resonators make the reversed dissipation regime
experimentally realizable.Comment: 5+3 pages, 5 figures, 1 tabl
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