510 research outputs found
Nitrophily in relation to nitrification
This article does not have an abstract
Relic density of wino-like dark matter in the MSSM
The relic density of TeV-scale wino-like neutralino dark matter in the MSSM
is subject to potentially large corrections as a result of the Sommerfeld
effect. A recently developed framework enables us to calculate the
Sommerfeld-enhanced relic density in general MSSM scenarios, properly treating
mixed states and multiple co-annihilating channels as well as including
off-diagonal contributions. Using this framework, including on-shell one-loop
mass splittings and running couplings and taking into account the latest
experimental constraints, we perform a thorough study of the regions of
parameter space surrounding the well known pure-wino scenario: namely the
effect of sfermion masses being non-decoupled and of allowing non-negligible
Higgsino or bino components in the lightest neutralino. We further perform an
investigation into the effect of thermal corrections and show that these can
safely be neglected. The results reveal a number of phenomenologically
interesting but so far unexplored regions where the Sommerfeld effect is
sizeable. We find, in particular, that the relic density can agree with
experiment for dominantly wino neutralino dark matter with masses ranging from
1.7 to beyond 4 TeV. In light of these results the bounds from Indirect
Detection on wino-like dark matter should be revisited.Comment: 49 pages, 15 figure
Neutralino Decays in the Complex MSSM at One-Loop: a Comparison of On-Shell Renormalization Schemes
We evaluate two-body decay modes of neutralinos in the Minimal Supersymmetric
Standard Model with complex parameters (cMSSM). Assuming heavy scalar quarks we
take into account all two-body decay channels involving charginos, neutralinos,
(scalar) leptons, Higgs bosons and Standard Model gauge bosons. The evaluation
of the decay widths is based on a full one-loop calculation including hard and
soft QED radiation. Of particular phenomenological interest are decays
involving the Lightest Supersymmetric Particle (LSP), i.e. the lightest
neutralino, or a neutral or charged Higgs boson. For the chargino/neutralino
sector we employ two different renormalization schemes, which differ in the
treatment of the complex phases. In the numerical analysis we concentrate on
the decay of the heaviest neutralino and show the results in the two different
schemes. The higher-order corrections of the heaviest neutralino decay widths
involving the LSP can easily reach a level of about 10-15%, while the
corrections to the decays to Higgs bosons are up to 20-30%, translating into
corrections of similar size in the respective branching ratios. The difference
between the two schemes, indicating the size of unknown two-loop corrections,
is less than order(0.1%). These corrections are important for the correct
interpretation of LSP and Higgs production at the LHC and at a future linear
e+e- collider. The results will be implemented into the Fortran code FeynHiggs.Comment: 49 pages, 27 figures, typos corrected. arXiv admin note: substantial
text overlap with arXiv:1112.0760, arXiv:1111.7289, arXiv:1204.400
Macroscopic Quantum Tunnelling in Rotating Bose-Einstein Condensates
In this paper we investigate the macroscopic quantum tunnelling and the phase
coherence property of the rotating Bose-Einstein condensates in both static and
dynamic cases by using the mean field theory.Comment: 10 pages, 1 figure, submitted to Phys.Rev.
Quantized Orbits and Resonant Transport
A tight binding representation of the kicked Harper model is used to obtain
an integrable semiclassical Hamiltonian consisting of degenerate "quantized"
orbits. New orbits appear when renormalized Harper parameters cross integer
multiples of . Commensurability relations between the orbit frequencies
are shown to correlate with the emergence of accelerator modes in the classical
phase space of the original kicked problem. The signature of this resonant
transport is seen in both classical and quantum behavior. An important feature
of our analysis is the emergence of a natural scaling relating classical and
quantum couplings which is necessary for establishing correspondence.Comment: REVTEX document - 8 pages + 3 postscript figures. Submitted to
Phys.Rev.Let
Time-dependent tunneling of Bose-Einstein condensates
The influence of atomic interactions on time-dependent tunneling processes of
Bose-Einstein condensates is investigated. In a variety of contexts the
relevant condensate dynamics can be described by a Landau-Zener equation
modified by the appearance of nonlinear contributions. Based on this equation
it is discussed how the interactions modify the tunneling probability. In
particular, it is shown that for certain parameter values, due to a nonlinear
hysteresis effect, complete adiabatic population transfer is impossible however
slowly the resonance is crossed. The results also indicate that the
interactions can cause significant increase as well as decrease of tunneling
probabilities which should be observable in currently feasible experiments.Comment: 8 pages, 5 figure
Two-Body Random Ensembles: From Nuclear Spectra to Random Polynomials
The two-body random ensemble (TBRE) for a many-body bosonic theory is mapped
to a problem of random polynomials on the unit interval. In this way one can
understand the predominance of 0+ ground states, and analytic expressions can
be derived for distributions of lowest eigenvalues, energy gaps, density of
states and so forth. Recently studied nuclear spectroscopic properties are
addressed.Comment: 8 pages, 4 figures. To appear in Physical Review Letter
Complete Anatomy of B -> K*ll and its angular distribution
We present a complete and optimal set of observables for the exclusive 4-body
B meson decay B -> K*(->K pi) l+l- in the low dilepton mass region, that
contains a maximal number of clean observables. This basis of observables is
built in a systematic way. We show that all the previously defined observables
and any observable that one can construct, can be expressed as a function of
this basis. This set of observables contains all the information that can be
extracted from the angular distribution in the cleanest possible way. We
provide explicit expressions for the full and the uniangular distributions in
terms of this basis. The conclusions presented here can be easily extended to
the large-q^2 region. We study the sensitivity of the observables to
right-handed currents and scalars. Finally, we present for the first time all
the symmetries of the full distribution including massive terms and scalar
contributions.Comment: 37 pages, 12 Figures. Corrected typo in Eqs. (29) and (44). Results
and conclusions unchange
Bayesian Fit of Exclusive Decays: The Standard Model Operator Basis
We perform a model-independent fit of the short-distance couplings
within the Standard Model set of and operators. Our analysis of , and decays is the first to harness the full
power of the Bayesian approach: all major sources of theory uncertainty
explicitly enter as nuisance parameters. Exploiting the latest measurements,
the fit reveals a flipped-sign solution in addition to a Standard-Model-like
solution for the couplings . Each solution contains about half of the
posterior probability, and both have nearly equal goodness of fit. The Standard
Model prediction is close to the best-fit point. No New Physics contributions
are necessary to describe the current data. Benefitting from the improved
posterior knowledge of the nuisance parameters, we predict ranges for currently
unmeasured, optimized observables in the angular distributions of .Comment: 42 pages, 8 figures; v2: Using new lattice input for f_Bs,
considering Bs-mixing effects in BR[B_s->ll]. Main results and conclusion
unchanged, matches journal versio
Damped Bloch oscillations of cold atoms in optical lattices
The paper studies Bloch oscillations of cold neutral atoms in the optical
lattice. The effect of spontaneous emission on the dynamics of the system is
analyzed both analytically and numerically. The spontaneous emission is shown
to cause (i) the decay of Bloch oscillations with the decrement given by the
rate of spontaneous emission and (ii) the diffusive spreading of the atoms with
a diffusion coefficient depending on {\em both} the rate of spontaneous
emission and the Bloch frequency.Comment: 10 pages, 8 figure
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