1,256 research outputs found
Producing cereal seeds for organic agriculture
This tool is a data sheet that can be used by French farmers who produce or want to produce cereal seeds in organic conditions.
It provides advice starting from the contract signing to the seed drying, going through the specificities of the crop, the sowing, specific pests and their management, and the harvest
Light dark matter in the NMSSM: upper bounds on direct detection cross sections
In the Next-to-Minimal Supersymmetric Standard Model, a bino-like LSP can be
as light as a few GeV and satisfy WMAP constraints on the dark matter relic
density in the presence of a light CP-odd Higgs scalar. We study upper bounds
on the direct detection cross sections for such a light LSP in the mass range
2-20 GeV in the NMSSM, respecting all constraints from B-physics and LEP. The
OPAL constraints on e^+ e^- -> \chi^0_1 \chi^0_i (i > 1) play an important role
and are discussed in some detail. The resulting upper bounds on the
spin-independent and spin-dependent nucleon cross sections are ~ 10^{-42}
cm^{-2} and ~ 4\times 10^{-40} cm^{-2}, respectively. Hence the upper bound on
the spin-independent cross section is below the DAMA and CoGeNT regions, but
could be compatible with the two events observed by CDMS-II.Comment: 17 pages, 3 figure
Forward-backward Asymmetry and Branching Ratio of B \rar K_1 \ell^+ \ell^- Transition in Supersymmetric Models
The mass eigen states and are mixture of the strange
members of two axial-vector SU(3) octet, and .
Taking into account this mixture, the forward-backward asymmetry and branching
ratio of B \rar K_1(1270,1400) \ell^+ \ell^- transitions are studied in the
framework of different supersymmetric models. It is found that the results have
considerable deviation from the standard model predictions. Any measurement of
these physical observables and their comparison with the results obtained in
this paper can give useful information about the nature of interactions beyond
the standard model.Comment: 14 pages, 4 figure
Minimal lepton flavor violating realizations of minimal seesaw models
We study the implications of the global U(1)R symmetry present in minimal
lepton flavor violating implementations of the seesaw mechanism for neutrino
masses. In the context of minimal type I seesaw scenarios with a slightly
broken U(1)R, we show that, depending on the R-charge assignments, two classes
of generic models can be identified. Models where the right-handed neutrino
masses and the lepton number breaking scale are decoupled, and models where the
parameters that slightly break the U(1)R induce a suppression in the light
neutrino mass matrix. We show that within the first class of models,
contributions of right-handed neutrinos to charged lepton flavor violating
processes are severely suppressed. Within the second class of models we study
the charged lepton flavor violating phenomenology in detail, focusing on mu to
e gamma, mu to 3e and mu to e conversion in nuclei. We show that sizable
contributions to these processes are naturally obtained for right-handed
neutrino masses at the TeV scale. We then discuss the interplay with the
effects of the right-handed neutrino interactions on primordial B - L
asymmetries, finding that sizable right-handed neutrino contributions to
charged lepton flavor violating processes are incompatible with the requirement
of generating (or even preserving preexisting) B - L asymmetries consistent
with the observed baryon asymmetry of the Universe.Comment: 21 pages, 4 figures; version 2: Discussion on possible generic models
extended, typos corrected, references added. Version matches publication in
JHE
Interplay of LFV and slepton mass splittings at the LHC as a probe of the SUSY seesaw
We study the impact of a type-I SUSY seesaw concerning lepton flavour
violation (LFV) both at low-energies and at the LHC. The study of the di-lepton
invariant mass distribution at the LHC allows to reconstruct some of the masses
of the different sparticles involved in a decay chain. In particular, the
combination with other observables renders feasible the reconstruction of the
masses of the intermediate sleptons involved in decays. Slepton mass splittings can be either
interpreted as a signal of non-universality in the SUSY soft breaking-terms
(signalling a deviation from constrained scenarios as the cMSSM) or as being
due to the violation of lepton flavour. In the latter case, in addition to
these high-energy processes, one expects further low-energy manifestations of
LFV such as radiative and three-body lepton decays. Under the assumption of a
type-I seesaw as the source of neutrino masses and mixings, all these LFV
observables are related. Working in the framework of the cMSSM extended by
three right-handed neutrino superfields, we conduct a systematic analysis
addressing the simultaneous implications of the SUSY seesaw for both high- and
low-energy lepton flavour violation. We discuss how the confrontation of
slepton mass splittings as observed at the LHC and low-energy LFV observables
may provide important information about the underlying mechanism of LFV.Comment: 50 pages, 42 eps Figures, typos correcte
Flavour physics from an approximate U(2)^3 symmetry
The quark sector of the Standard Model exhibits an approximate U(2)^3 flavour
symmetry. This symmetry, broken in specific directions dictated by minimality,
can explain the success of the Cabibbo-Kobayashi-Maskawa picture of flavour
mixing and CP violation, confirmed by the data so far, while allowing for
observable deviations from it, as expected in most models of ElectroWeak
Symmetry Breaking. Building on previous work in the specific context of
supersymmetry, we analyze the expected effects and we quantify the current
bounds in a general Effective Field Theory framework. As a further relevant
example we then show how the U(2)^3 symmetry and its breaking can be
implemented in a generic composite Higgs model and we make a first analysis of
its peculiar consequences. We also discuss how some partial extension of U(2)^3
to the lepton sector can arise, both in general and in composite Higgs models.
An optimistic though conceivable interpretation of the considerations developed
in this paper gives reasons to think that new physics searches in the flavour
sector may be about to explore an interesting realm of phenomena.Comment: 29 pages, 5 figure
Model-independent constraints on new physics in b --> s transitions
We provide a comprehensive model-independent analysis of rare decays
involving the b --> s transition to put constraints on dimension-six Delta(F)=1
effective operators. The constraints are derived from all the available
up-to-date experimental data from the B-factories, CDF and LHCb. The
implications and future prospects for observables in b --> s l+l- and b --> s
nu nu transitions in view of improved measurements are also investigated. The
present work updates and generalises previous studies providing, at the same
time, a useful tool to test the flavour structure of any theory beyond the SM.Comment: 1+39 pages, 12 figures, 3 tables. v2: minor modifications, typos
corrected, references added, version to be published in JHE
Background Light in Potential Sites for the ANTARES Undersea Neutrino Telescope
The ANTARES collaboration has performed a series of {\em in situ}
measurements to study the background light for a planned undersea neutrino
telescope. Such background can be caused by K decays or by biological
activity. We report on measurements at two sites in the Mediterranean Sea at
depths of 2400~m and 2700~m, respectively. Three photomultiplier tubes were
used to measure single counting rates and coincidence rates for pairs of tubes
at various distances. The background rate is seen to consist of three
components: a constant rate due to K decays, a continuum rate that
varies on a time scale of several hours simultaneously over distances up to at
least 40~m, and random bursts a few seconds long that are only correlated in
time over distances of the order of a meter. A trigger requiring coincidences
between nearby photomultiplier tubes should reduce the trigger rate for a
neutrino telescope to a manageable level with only a small loss in efficiency.Comment: 18 pages, 8 figures, accepted for publication in Astroparticle
Physic
Charged-Higgs phenomenology in the Aligned two-Higgs-doublet model
The alignment in flavour space of the Yukawa matrices of a general
two-Higgs-doublet model results in the absence of tree-level flavour-changing
neutral currents. In addition to the usual fermion masses and mixings, the
aligned Yukawa structure only contains three complex parameters, which are
potential new sources of CP violation. For particular values of these three
parameters all known specific implementations of the model based on discrete
Z_2 symmetries are recovered. One of the most distinctive features of the
two-Higgs-doublet model is the presence of a charged scalar. In this work, we
discuss its main phenomenological consequences in flavour-changing processes at
low energies and derive the corresponding constraints on the parameters of the
aligned two-Higgs-doublet model.Comment: 46 pages, 19 figures. Version accepted for publication in JHEP.
References added. Discussion slightly extended. Conclusions unchange
Flavour physics constraints in the BMSSM
We study the implications of the presence of the two leading-order,
non-renormalizable operators in the Higgs sector of the MSSM to flavour physics
observables. We identify the constraints of flavour physics on the parameters
of the BMSSM when we: a) focus on a region of parameters for which electroweak
baryogenesis is feasible, b) use a CMSSM-like parametrization, and c) consider
the case of a generic NUHM-type model. We find significant differences as
compared to the standard MSSM case.Comment: 22 pages, 7 figure
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