[Show abstract][Hide abstract] ABSTRACT: 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 $SU(2)\times U(1)$ doublet
and a new symmetry, namely a spontaneously broken $\mathbb{Z}_2$ or a softly
broken global $U(1)$. 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 $\mathbb{Z}_2$ 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 $T$ parameter. In particular, the
new charged and neutral scalars must have very similar masses.
[Show abstract][Hide abstract] ABSTRACT: In composite Higgs models the pseudo-Nambu-Goldstone Boson (pNGB) nature of
the Higgs field is an interesting alternative for explaning the smallness of
the electroweak scale with respect to the beyond the Standard Model scale. In
non-minimal models additional pNGB states are present and can be a Dark Matter
(DM) candidate, if there is an approximate symmetry suppressing their decay.
Here we assume that the low energy effective theory (for scales much below the
compositeness scale) corresponds to the Standard Model with a pNGB Higgs
doublet and a pNGB DM multiplet. We derive general effective DM Lagrangians for
several possible DM representations (under the SM gauge group), including the
singlet, doublet and triplet cases. Within this framework we discuss how the DM
observables (relic abundance, direct and indirect detection) constrain the
dimension-6 operators induced by the strong sector assuming that DM behaves as
a Weakly Interacting Particle (WIMP) and that the relic abundance is settled
through the freeze-out mechanism. We also apply our general results to two
specific cosets: $SO(6)/SO(5)$ and $SO(6)/SO(4) \times SO(2)$, which contain a
singlet and doublet DM candidate, respectively. In particular we show that if
compositeness is a solution to the little hierarchy problem, representations
larger than the triplet are strongly disfavored. Furthermore, we find that
composite models can have viable DM candidates with much smaller direct
detection cross-sections than their non-composite counterparts, making DM
detection much more challenging.
Journal of High Energy Physics 01/2015; 2015(6). DOI:10.1007/JHEP06(2015)154 · 6.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We discuss possible interpretations of the 37 high energy neutrino events
observed by the IceCube experiment in the South Pole. We examine the
possibility to explain the observed neutrino spectrum exclusively by the decays
of a heavy long-lived particle of mass in the PeV range. We compare this with
the standard scenario, namely, a single power-law spectrum related to neutrinos
produced by astrophysical sources and a viable hybrid situation where the
spectrum is a product of two components: a power-law and the long-lived
particle decays. We present a simple extension of the Standard Model that could
account for the heavy particle decays that are needed in order to explain the
data. We show that the current data equally supports all above scenarios and
try to evaluate the exposure needed in order to falsify them in the future.
Journal of High Energy Physics 11/2014; 2015(2). DOI:10.1007/JHEP02(2015)189 · 6.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We discuss the potential of a neutrino detector based on liquid
scintilator which could be constructed at the ANDES underground
laboratory for the observations of neutrinos coming from a galactic
supernova and decay of radioactive elements in the Earth interior.
[Show abstract][Hide abstract] ABSTRACT: These lecture notes are based on a course given at Institut de Physique
Th\'eorique of CEA/Saclay in January/February 2013.
[Show abstract][Hide abstract] ABSTRACT: 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.
Journal of High Energy Physics 07/2013; 2014(5). DOI:10.1007/JHEP05(2014)109 · 6.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In view of the advent of large-scale neutrino detectors such as IceCube, the
future Hyper-Kamiokande and the ones proposed for the Laguna project in Europe,
we re-examine the determination of the directional position of a Galactic
supernova by means of its neutrinos using the triangulation method. We study
the dependence of the pointing accuracy on the arrival time resolution of
supernova neutrinos at different detectors. For a failed supernova, we expect
better results due to the abrupt termination of the neutrino emission which
allows one to measure the arrival time with higher precision. We found that for
the time resolution of $\pm$ 2 (4) ms, the supernova can be located with a
precision of $\sim$ 5 (10)$^\circ$ on the declination and of $\sim$ 8
(15)$^\circ$ on the right ascension angle, if we combine the observations from
detectors at four different sites.
[Show abstract][Hide abstract] ABSTRACT: 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.
Journal of High Energy Physics 02/2013; 2013(6). DOI:10.1007/JHEP06(2013)097 · 6.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We analyse the interplay between the Higgs to diphoton rate and electroweak precision measurements constraints in extensions of the Standard Model with new uncolored charged fermions that do not mix with the ordinary ones. We also compute the pair production cross sections for the lightest fermion and compare them with current bounds.
Journal of High Energy Physics 11/2012; 2012(11). DOI:10.1007/JHEP11(2012)085 · 6.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We analyze the behavior of Higgs to diphoton rate and Higgs gluon-gluon
production cross section in minimal extensions of the Standard Model comprising
new colored vector-like fermions that do not mix with the ordinary ones. We
compare these information with constraints coming from electroweak precision
measurements. We compute pair production cross sections for the lightest
fermion and discuss the LHC bounds. Finally, we study the phenomenology of
possible quarkonium states composed by these new colored fermions.
Journal of High Energy Physics 09/2012; 2013(2). DOI:10.1007/JHEP02(2013)086 · 6.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We present an alternative explanation to the reactor antineutrino anomaly through neutrino oscillation induced by the presence of a large flat extra dimension with a size in the sub-micrometer range. We also show that the solution is consistent with the other existing oscillation data.
Journal of Physics Conference Series 07/2012; 375(4). DOI:10.1088/1742-6596/375/1/042047
[Show abstract][Hide abstract] ABSTRACT: We discuss the potential of a liquid scintillator neutrino detector of about 3 kilotons located in the proposed first deep underground laboratory in the Southern Hemisphere, ANDES, to measure geo-neutrinos and neutrinos from a stellar core-collapse.
Journal of Physics Conference Series 07/2012; 375(4). DOI:10.1088/1742-6596/375/1/042062
[Show abstract][Hide abstract] ABSTRACT: The construction of the Agua Negra tunnels that will link Argentina and Chile
under the Andes, the world longest mountain range, opens the possibility to
build the first deep underground labo- ratory in the Southern Hemisphere. This
laboratory has the acronym ANDES (Agua Negra Deep Experiment Site) and its
overburden could be as large as \sim 1.7 km of rock, or 4500 mwe, providing an
excellent low background environment to study physics of rare events like the
ones induced by neutrinos and/or dark matter. In this paper we investigate the
physics potential of a few kiloton size liquid scintillator detector, which
could be constructed in the ANDES laboratory as one of its possible scientific
programs. In particular, we evaluate the impact of such a detector for the
studies of geoneutrinos and galactic supernova neutrinos assuming a fiducial
volume of 3 kilotons as a reference size. We emphasize the complementary roles
of such a detector to the ones in the Northern Hemisphere neutrino facilities
through some advantages due to its geographical location.
[Show abstract][Hide abstract] ABSTRACT: We analyse the interplay between the Higgs to diphoton rate and electroweak
precision measurements contraints in extensions of the Standard Model with new
uncolored charged fermions that do not mix with the ordinary ones. We also
compute the pair production cross sections for the lightest fermion and compare
them with current bounds.
[Show abstract][Hide abstract] ABSTRACT: If the neutrino analogue of the Mössbauer effect, namely, recoiless emission and resonant capture of neutrinos is realized, one can study neutrino oscillations with much shorter baselines and smaller source/detector size when compared to conventional exper-iments. In this work, we discuss the potential of such a Mössbauer neutrino oscillation experiment to probe nonstandard neutrino properties coming from some new physics be-yond the standard model. We investigate four scenarios for such new physics that modify the standard oscillation pattern. We consider the existence of a light sterile neutrino that can mix with ¯ ν e , the existence of a Kaluza-Klein tower of sterile neutrinos that can mix with the flavor neutrinos in a model with large flat extra dimensions, neutrino oscillations with nonstandard quantum decoherence and mass varying neutrinos, and discuss to which extent one can constrain these scenarios. We also discuss the impact of such new physics on the determination of the standard oscillation parameters.
Journal of High Energy Physics 01/2012; 11(11). DOI:10.1007/JHEP11(2011)136 · 6.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In the framework of gauged flavour symmetries, new fermions in parity
symmetric representations of the standard model are generically needed for the
compensation of mixed anomalies. The key point is that their masses are also
protected by flavour symmetries and some of them are expected to lie way below
the flavour symmetry breaking scale(s), which has to occur many orders of
magnitude above the electroweak scale to be compatible with the available data
from flavour changing neutral currents and CP violation experiments. We argue
that, actually, some of these fermions would plausibly get masses within the
LHC range. If they are taken to be heavy quarks and leptons, in
(bi)-fundamental representations of the standard model symmetries, their
mixings with the light ones are strongly constrained to be very small by
electroweak precision data. The alternative chosen here is to exactly forbid
such mixings by breaking of flavour symmetries into an exact discrete symmetry,
the so-called proton-hexality, primarily suggested to avoid proton decay. As a
consequence of the large value needed for the flavour breaking scale, those
heavy particles are long-lived and rather appropriate for the current and
future searches at the LHC for quasi-stable hadrons and leptons. In fact, the
LHC experiments have already started to look for them.
Journal of High Energy Physics 12/2011; 2012(2). DOI:10.1007/JHEP02(2012)123 · 6.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The lepton mixing angle theta_13, the only unknown angle in the standard
three-flavor neutrino mixing scheme, is finally measured by the recent reactor
and accelerator neutrino experiments. We perform a combined analysis of the
data coming from T2K, MINOS, Double Chooz, Daya Bay and RENO experiments and
find sin^2 2theta_13 = 0.096 \pm 0.013 (\pm 0.040) at 1 sigma (3 sigma) CL and
that the hypothesis theta_13 = 0 is now rejected at a significance level of 7.7
sigma. We also discuss the near future expectation on the precision of the
theta_13 determination by using expected data from these ongoing experiments.
Journal of High Energy Physics 11/2011; 2012(5). DOI:10.1007/JHEP05(2012)023 · 6.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We consider a model where right-handed neutrinos propagate in a large
compactified extra dimension, engendering Kaluza-Klein (KK) modes, while the
standard model particles are restricted to the usual 4-dimensional brane. A
mass term mixes the KK modes with the standard left-handed neutrinos, opening
the possibility of change the 3 generation mixing pattern. We derive bounds on
the maximum size of the extra dimension from neutrino oscillation experiments.
We show that this model provides a possible explanation for the deficit of nu_e
in Ga solar neutrino calibration experiments and of the anti-nu_e in short
baseline reactor experiments.