1,961 research outputs found
The LMA Solution from Bimaximal Lepton Mixing at the GUT Scale by Renormalization Group Running
We show that in see-saw models with bimaximal lepton mixing at the GUT scale
and with zero CP phases, the solar mixing angle theta_{12} generically evolves
towards sizably smaller values due to Renormalization Group effects, whereas
the evolution of theta_{13} and theta_{23} is comparatively small. The
currently favored LMA solution of the solar neutrino problem can thus be
obtained in a natural way from bimaximal mixing at the GUT scale. We present
numerical examples for the evolution of the leptonic mixing angles in the
Standard Model and the MSSM, in which the current best-fit values of the LMA
mixing angles are produced. These include a case where the mass eigenstates
corresponding to the solar mass squared difference have opposite CP parity.Comment: 14 pages, 10 figures; references and a subsection containing an
example with odd CP parities added; results and conclusions unchange
The Prediction value
We introduce the prediction value (PV) as a measure of players' informational
importance in probabilistic TU games. The latter combine a standard TU game and
a probability distribution over the set of coalitions. Player 's prediction
value equals the difference between the conditional expectations of when
cooperates or not. We characterize the prediction value as a special member
of the class of (extended) values which satisfy anonymity, linearity and a
consistency property. Every -player binomial semivalue coincides with the PV
for a particular family of probability distributions over coalitions. The PV
can thus be regarded as a power index in specific cases. Conversely, some
semivalues -- including the Banzhaf but not the Shapley value -- can be
interpreted in terms of informational importance.Comment: 26 pages, 2 table
Coherent scattering and macroscopic coherence: Implications for neutrino, dark matter and axion detection
We study the question of whether coherent neutrino scattering can occur on
macroscopic scales, leading to a significant increase of the detection cross
section. We concentrate on radiative neutrino scattering on atomic electrons
(or on free electrons in a conductor). Such processes can be coherent provided
that the net electron recoil momentum, i.e. the momentum transfer from the
neutrino minus the momentum of the emitted photon, is sufficiently small. The
radiative processes is an attractive possibility as the energy of the emitted
photons can be as large as the momentum transfer to the electron system and
therefore the problem of detecting extremely low energy recoils can be avoided.
The requirement of macroscopic coherence severely constrains the phase space
available for the scattered particle and the emitted photon. We show that in
the case of the scattering mediated by the usual weak neutral current and
charged current interactions this leads to a strong suppression of the
elementary cross sections and therefore the requirement of macroscopic
coherence results in a reduction rather than an increase of the total detection
cross section. However, for the scattering mediated by neutrino
magnetic or electric dipole moments coherence effects can actually increase the
detection rates. Effects of macroscopic coherence can also allow detection of
neutrinos in 100 eV -- a few keV energy range, which is currently not
accessible to the experiment. A similar coherent enhancement mechanism can work
for relativistic particles in the dark sector, but not for the conventionally
considered non-relativistic dark matter.Comment: LaTeX, 31 page, 2 figures. v2: a section on coherent axion detection
and an appendix added; title modifie
Revisiting Neutrino Self-Interaction Constraints from and decays
Given the elusive nature of neutrinos, their self-interaction is particularly
difficult to probe. Nevertheless, upper limits on the strength of such an
interaction can be set by using data from terrestrial experiments. In this work
we focus on additional contributions to the invisible decay width of boson
as well as the leptonic decay width in the presence of a neutrino
coupling to a relatively light scalar. For invisible decays we derive a
complete set of constraints by considering both three-body bremsstrahlung as
well as the loop correction to two-body decays. While the latter is usually
regarded to give rather weak limits we find that through the interference with
the Standard Model diagram it actually yields a competitive constraint. As far
as leptonic decays of are concerned, we derive a first limit on neutrino
self-interactions that is valid across the whole mass range of a light scalar
mediator. Our bounds on the neutrino self-interaction are leading for MeV and interactions that prefer . Bounds on such
-philic scalar are particularly relevant in light of the recently proposed
alleviation of the Hubble tension in the presence of such couplings.Comment: 17 pages, 7 figures, calculations related to IR divergence added, PRD
published versio
Production and Properties of the Liquid Scintillators used in the Stereo Reactor Neutrino Experiment
The electron antineutrino spectrum in the Stereo reactor experiment (ILL
Grenoble) is measured via the inverse beta decay signals in an organic liquid
scintillator. The six target cells of the Stereo detector are filled with about
1800 litres of Gd-loaded liquid scintillator optimised for the requirements of
the experiment. These target cells are surrounded by similar cells containing
liquid scintillator without the Gd-loading. The development and characteristics
of these scintillators are reported. In particular, the transparency, light
production and pulse shape discrimination capabilities of the organic liquids
are discussed.Comment: 10 pages, 4 figure
Neutrino Mass Operator Renormalization in Two Higgs Doublet Models and the MSSM
In a recent re-analysis of the Standard Model (SM) beta-function for the
effective neutrino mass operator, we found that the previous results were not
entirely correct. Therefore, we consider the analogous dimension five operators
in a class of Two Higgs Doublet Models (2HDM's) and the Minimal Supersymmetric
Standard Model (MSSM). Deriving the renormalization group equations for these
effective operators, we confirm the existing result in the case of the MSSM.
Some of our 2HDM results are new, while others differ from earlier
calculations. This leads to modifications in the renormalization group
evolution of leptonic mixing angles and CP phases in the 2HDM's.Comment: 8 pages, 18 eps figure
Dynamical Electroweak Symmetry Breaking by a Neutrino Condensate
We show that the electroweak symmetry can be broken in a natural and
phenomenologically acceptable way by a neutrino condensate. Therefore, we
assume as particle content only the chiral fermions and gauge bosons of the
Standard Model and in addition right-handed neutrinos. A fundamental Higgs
field is absent. We assume instead that new interactions exist that can
effectively be described as four-fermion interactions and that can become
critical in the neutrino sector. We discuss in detail the coupled
Dirac-Majorana gap equations which lead to a neutrino condensate, electroweak
symmetry breaking and via the dynamical see-saw mechanism to small neutrino
masses. We show that the effective Lagrangian is that of the Standard Model
with massive neutrinos and with a composite Higgs particle. The mass
predictions are consistent with data.Comment: 18 pages, 8 figures; minor clarifications; version to appear in Nucl.
Phys.
"Meet the farmer" : Kleinbauern, Regionalentwicklung und der neue globale Agrarmarkt
Lebensmittelkrisen wie BSE, Schweinepest, Vogelgrippe und der »Gammelfleischskandal« haben das Vertrauen der Verbraucher in den Agrarmarkt erschüttert. Deshalb verwenden Produzenten und Einzelhändler heute mehr Anstrengungen als jemals zuvor darauf, der verunsichernden Anonymität der global organisierten Produktion durch die Herstellung sozialer Nähe entgegenzuwirken. So suggerieren Herkunftszertifi kate für Regionalprodukte sowie eine schnell steigende Zahl von Hygiene-, Sozial- und Umweltstandards Verlässlichkeit aufgrund von geringen räumlichen Distanzen und unabhängiger Kontrolle, während Initiativen wie »Caretrace: Meet the Farmer« dadurch Vertrauen schaffen sollen, dass sich der Konsument im Internet über den individuellen Produzenten informieren kann. Doch die Folgen dieser Umbrüche für Produktionsweisen und Anbauregionen sind bislang nur wenig bekannt
Neutrino Mass Operator Renormalization Revisited
We re-derive the renormalization group equation for the effective coupling of
the dimension five operator which corresponds to a Majorana mass matrix for the
Standard Model neutrinos. We find a result which differs somewhat from earlier
calculations, leading to modifications in the evolution of leptonic mixing
angles and CP phases. We also present a general method for calculating
beta-functions from counterterms in MS-like renormalization schemes, which
works for tensorial quantities.Comment: 9 pages, 2 figures, references update
Pseudoscalar Mediators: A WIMP model at the Neutrino Floor
Due to its highly suppressed cross section (fermionic) dark matter
interacting with the Standard Model via pseudoscalar mediators is expected to
be essentially unobservable in direct detection experiments. We consider both a
simplified model and a more realistic model based on an extended two Higgs
doublet model and compute the leading one-loop contribution to the effective
dark matter- nucleon interaction. This higher order correction dominates the
scattering rate completely and can naturally, i.e. for couplings of order one,
lead to a direct detection cross section in the vicinity of the neutrino floor.
Taking the observed relic density and constraints from low-energy observables
into account we analyze the direct detection prospects in detail and find
regions of parameter space that are within reach of upcoming direct detection
experiments such as XENONnT, LZ, and DARWIN.Comment: 29 pages, 8 figure
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