1,831 research outputs found
Flavored Axions
Precision flavor experiments can look for the QCD axion complementarily to
usual searches with axion helio- and haloscopes, allowing to test PQ breaking
scales as high as . Such searches are sensitive to
flavor-violating axion couplings, which are generic and potentially sizable
whenever SM fermions carry flavor non-universal PQ charges. A particularly
predictive scenario is obtained when PQ is identified with the simplest FN
flavor symmetry, so that all flavor-violating axion couplings are related to
Yukawa hierarchies, up to coefficients.Comment: 8 pages, 1 figure, Contribution to the proceedings of the Corfu
Summer Institute 201
Lepton Flavor Non-Universality in B-meson Decays from a U(2) Flavor Model
We address the recent anomalies in semi-leptonic -meson decays using a
model of fermion masses based on the flavor symmetry. The new
contributions to transitions arise due to a tree-level
exchange of a vector boson gauging a subgroup of the flavor
symmetry. They are controlled by a single parameter and are approximately
aligned to the Standard Model prediction, with constructive interference in the
-channel and destructive interference in the -channel. The current
experimental data on semi-leptonic -meson decays can be very well reproduced
without violating existing constraints from flavor violation in the quark and
lepton sectors. Our model will be tested by new measurements of transitions and also by future electroweak precision tests, direct
searches, and - conversion in nuclei.Comment: 23 pages, 2 figures, references added, matches published versio
Lepton Flavor Violation in Flavored Gauge Mediation
We study the anatomy and phenomenology of Lepton Flavor Violation (LFV) in
the context of Flavored Gauge Mediation (FGM). Within FGM, the messenger sector
couples directly to the MSSM matter fields with couplings controlled by the
same dynamics that explains the hierarchies in the SM Yukawas. Although the
pattern of flavor violation depends on the particular underlying flavor model,
FGM provides a built-in flavor suppression similar to wave function
renormalization or SUSY Partial Compositeness. Moreover, in contrast to these
models, there is an additional suppression of left-right (LR) flavor
transitions by third-generation Yukawas that in particular provides an extra
protection against flavor-blind phases. We exploit the consequences of this
setup for lepton flavor phenomenology, assuming that the new couplings are
controlled by simple U(1) flavor models that have been proposed to accommodate
large neutrino mixing angles. Remarkably, it turns out that in the context of
FGM these models can pass the impressive constraints from LFV processes and
leptonic EDMs even for light superpartners, therefore offering the possibility
of resolving the longstanding muon g-2 anomaly.Comment: 32 pages, 7 figure
An Algorithm for Computing Screened Coulomb Scattering in Geant4
An algorithm has been developed for the Geant4 Monte-Carlo package for the
efficient computation of screened Coulomb interatomic scattering. It explicitly
integrates the classical equations of motion for scattering events, resulting
in precise tracking of both the projectile and the recoil target nucleus. The
algorithm permits the user to plug in an arbitrary screening function, such as
Lens-Jensen screening, which is good for backscattering calculations, or
Ziegler-Biersack-Littmark screening, which is good for nuclear straggling and
implantation problems. This will allow many of the applications of the TRIM and
SRIM codes to be extended into the much more general Geant4 framework where
nuclear and other effects can be included.Comment: 19 pages, 6 figures; corrected to rerferee comments, typo in equation
5 fixe
Inducing the mu and the B mu Term by the Radion and the 5d Chern-Simons Term
In 5-dimensional models with gauge-Higgs unification, the F-term vacuum
expectation value of the radion provides, in close analogy to the
Giudice-Masiero mechanism, a natural source for the mu and B mu term. Both the
leading order gauge theory lagrangian and the supersymmetric Chern-Simons term
contain couplings to the radion superfield which can be used for this purpose.
We analyse the basic features of this mechanism for mu term generation and
provide an explicit example, based on a variation of the SU(6) gauge-Higgs
unification model of Burdman and Nomura. This construction contains all the
relevant features used in our generic analysis. More generally, we expect our
mechanism to be relevant to many of the recently discussed orbifold GUT models
derived from heterotic string theory. This provides an interesting way of
testing high-scale physics via Higgs mass patterns accessible at the LHC.Comment: 23 pages, LaTeX, 1 figure, concrete model significantly improved,
references adde
Faint Light from Dark Matter: Classifying and Constraining Dark Matter-Photon Effective Operators
Even if Dark Matter (DM) is neutral under electromagnetism, it can still
interact with the Standard Model (SM) via photon exchange from
higher-dimensional operators. Here we classify the general effective operators
coupling DM to photons, distinguishing between Dirac/Majorana fermion and
complex/real scalar DM. We provide model-independent constraints on these
operators from direct and indirect detection. We also constrain various
DM-lepton operators, which induce DM-photon interactions via RG running or
which typically arise in sensible UV-completions. This provides a simple way to
quickly assess constraints on any DM model that interacts mainly via photon
exchange or couples to SM leptons.Comment: 32 pages + appendices, 9 + 1 figures, 2 + 1 tables. v2: some
clarifications and references added; conclusions unchanged; version published
in JHE
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