9,870 research outputs found
Neutrino Mass Matrix Textures: A Data-driven Approach
We analyze the neutrino mass matrix entries and their correlations in a
probabilistic fashion, constructing probability distribution functions using
the latest results from neutrino oscillation fits. Two cases are considered:
the standard three neutrino scenario as well as the inclusion of a new sterile
neutrino that potentially explains the reactor and gallium anomalies. We
discuss the current limits and future perspectives on the mass matrix elements
that can be useful for model building.Comment: 25 pages, 18 figure
Flavor Gauge Models Below the Fermi Scale
The mass and weak interaction eigenstates for the quarks of the third
generation are very well aligned, an empirical fact for which the Standard
Model offers no explanation. We explore the possibility that this alignment is
due to an additional gauge symmetry in the third generation. Specifically, we
construct and analyze an explicit, renormalizable model with a gauge boson,
, corresponding to the symmetry of the third family. Having a
relatively light (in the MeV to multi-GeV range), flavor-nonuniversal gauge
boson results in a variety of constraints from different sources. By
systematically analyzing 20 different constraints, we identify the most
sensitive probes: kaon, , and Upsilon decays, mixing,
atomic parity violation, and neutrino scattering and oscillations. For the new
gauge coupling in the range the model is shown to
be consistent with the data. Possible ways of testing the model in physics,
top and decays, direct collider production and neutrino oscillation
experiments, where one can observe nonstandard matter effects, are outlined.
The choice of leptons to carry the new force is ambiguous, resulting in
additional phenomenological implications, such as non-universality in
semileptonic bottom decays. The proposed framework provides interesting
connections between neutrino oscillations, flavor and collider physics.Comment: 44 pages, 7 figures, 3 tables; B physics constraints and references
added, conclusions unchange
What can we learn about the lepton CP phase in the next 10 years?
We discuss how the lepton CP phase can be constrained by accelerator and
reactor measurements in an era without dedicated experiments for CP violation
search. To characterize globally the sensitivity to the CP phase \delta_{CP},
we introduce a new measure, the CP exclusion fraction, which quantifies what
fraction of the \delta_{CP} space can be excluded at a given input values of
\theta_{23} and \delta_{CP}. Using the measure we study the CP sensitivity
which may be possessed by the accelerator experiments T2K and NOvA. We show
that, if the mass hierarchy is known, T2K and NOvA alone may exclude,
respectively, about 50%-60% and 40%-50% of the \delta_{CP} space at 90% CL by
10 years running, provided that a considerable fraction of beam time is devoted
to the antineutrino run. The synergy between T2K and NOvA is remarkable,
leading to the determination of the mass hierarchy through CP sensitivity at
the same CL.Comment: Analyses and plots improved, conclusions unchanged, 23 pages, 8
figures, 1 tabl
On the renormalization of the electroweak chiral Lagrangian with a Higgs
We consider the scalar sector of the effective non-linear electroweak
Lagrangian with a light "Higgs" particle, up to four derivatives in the chiral
expansion. The complete off-shell renormalization procedure is implemented,
including one loop corrections stemming from the leading two-derivative terms,
for finite Higgs mass. This determines the complete set of independent chiral
invariant scalar counterterms required for consistency; these include bosonic
operators often disregarded. Furthermore, new counterterms involving the Higgs
particle which are apparently chiral non-invariant are identified in the
perturbative analysis. A novel general parametrization of the pseudoescalar
field redefinitions is proposed, which reduces to the various usual ones for
specific values of its parameter; the non-local field redefinitions reabsorbing
all chiral non-invariant counterterms are then explicitly determined. The
physical results translate into renormalization group equations which may be
useful when comparing future Higgs data at different energies
On the Viability of Minimal Neutrinophilic Two-Higgs-Doublet Models
We study the constraints that electroweak precision data can impose, after
the discovery of the Higgs boson by the LHC, on neutrinophilic
two-Higgs-doublet models which comprise one extra doublet
and a new symmetry, namely a spontaneously broken or a softly
broken global . In these models the extra Higgs doublet, via its very
small vacuum expectation value, is the sole responsible for neutrino masses. We
find that the model with a symmetry is basically ruled out by
electroweak precision data, even if the model is slightly extended to include
extra right-handed neutrinos, due to the presence of a very light scalar. While
the other model is still perfectly viable, the parameter space is considerably
constrained by current data, specially by the parameter. In particular, the
new charged and neutral scalars must have very similar masses.Comment: 22 pages, 3 figures, references and comments added, conclusions
unchanged, matches version to appear in JHE
Vector Meson Production in Ultraperipheral Heavy Ion Collisions
The ultraperipheral heavy ion collisions (UPC's) are an important alternative
to study the QCD dynamics until the next generation of
colliders become reality. Due to the coherent action of all the protons in the
nucleus, the electromagnetic field is very strong and the resulting flux of
equivalent photons is large, which allows to study two-photon as well as
photonuclear interactions at high energies. In this paper we present a brief
review of the vector meson production in UPC's at high energies using the QCD
color dipole approach to describe their photonuclear production and the
perturbative QCD Pomeron (BFKL dynamics) to describe the double meson
production in photon-photon process. Predictions for rates and integrated cross
sections are presented for energies of RHIC and LHC.Comment: 16 pages, 1 figure. Version to be published in Journal of Physics G:
Nuclear and Particle Physic
Decay of metastable phases in a model for the catalytic oxidation of CO
We study by kinetic Monte Carlo simulations the dynamic behavior of a
Ziff-Gulari-Barshad model with CO desorption for the reaction CO + O
CO on a catalytic surface. Finite-size scaling analysis of the fluctuations
and the fourth-order order-parameter cumulant show that below a critical CO
desorption rate, the model exhibits a nonequilibrium first-order phase
transition between low and high CO coverage phases. We calculate several points
on the coexistence curve. We also measure the metastable lifetimes associated
with the transition from the low CO coverage phase to the high CO coverage
phase, and {\it vice versa}. Our results indicate that the transition process
follows a mechanism very similar to the decay of metastable phases associated
with {\it equilibrium} first-order phase transitions and can be described by
the classic Kolmogorov-Johnson-Mehl-Avrami theory of phase transformation by
nucleation and growth. In the present case, the desorption parameter plays the
role of temperature, and the distance to the coexistence curve plays the role
of an external field or supersaturation. We identify two distinct regimes,
depending on whether the system is far from or close to the coexistence curve,
in which the statistical properties and the system-size dependence of the
lifetimes are different, corresponding to multidroplet or single-droplet decay,
respectively. The crossover between the two regimes approaches the coexistence
curve logarithmically with system size, analogous to the behavior of the
crossover between multidroplet and single-droplet metastable decay near an
equilibrium first-order phase transition.Comment: 27 pages, 22 figures, accepted by Physical Review
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