158 research outputs found
Constraining nonstandard neutrino interactions with electrons
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)We update the phenomenological constraints of the nonstandard neutrino interactions (NSNI) with electrons including in the analysis, for the first time, data from LAMPF, Krasnoyarsk, and the latest Texono observations. We assume that NSNI modify the cross section of elastic scattering of (anti) neutrinos off electrons, using reactor and accelerator data, and the cross section of the electron-positron annihilation, using the four LEP experiments, in particular, new data from DELPHI. We find more restrictive allowed regions for the NSNI parameters: -0.11< epsilon(eR)(ee) < 0.05 and -0.02 < epsilon(eL)(ee) < 0.09 (90% C.L.). We also recalculate the parameters of tauonic flavor obtaining -0.35 < epsilon(eR)(tau tau) < 0.50 and -0.51 < epsilon(eL)(tau tau) < 0.34 (90% C.L.). Although more severe than the limits already present in the literature, our results indicate that NSNI are allowed by the present data as a subleading effect, and the standard electroweak model continues consistent with the experimental panorama at 90% C.L. Further improvement on this picture will deserve a lot of engagement of upcoming experiments.841Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Spanish Grants [FPA2008-00319, CSD2009-00064, PROMETEO/2009/091]EU network UNILHC [PITN-GA-2009-237920]Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Spanish Grants [FPA2008-00319, CSD2009-00064, PROMETEO/2009/091]EU network UNILHC [PITN-GA-2009-237920
Quantum dissipation and CP violation in MINOS
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)We use the open quantum systems framework to analyze the MINOS data and perform this analysis considering two different dissipative models. In the first model, the dissipative parameter describes the decoherence effect and in the second, the dissipative parameter describes other dissipative effects including decoherence. With the second model it is possible to study CP violation since we consider Majorana neutrinos. The analysis from the muon neutrino and antineutrino beam assigns different values to all the parameters of the models, but is consistent between them. Assuming that neutrinos are equivalent to antineutrinos, the global analysis presents a nonvanishing Majorana CP phase depending on the energetic parametrization of the dissipative parameter.895Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)FAPESP [2012/00857-6
Testing matter effects in propagation of atmospheric and long-baseline neutrinos
We quantify our current knowledge of the size and flavor structure of the
matter effects in the evolution of atmospheric and long-baseline neutrinos
based solely on the analysis of the corresponding neutrino data. To this aim we
generalize the matter potential of the Standard Model by rescaling its
strength, rotating it away from the e-e sector, and rephasing it with respect
to the vacuum term. This phenomenological parametrization can be easily
translated in terms of non-standard neutrino interactions in matter. We show
that in the most general case, the strength of the potential cannot be
determined solely by atmospheric and long-baseline data. However its flavor
composition is very much constrained and the present determination of the
neutrino masses and mixing is robust under its presence. We also present an
update of the constraints arising from this analysis in the particular case in
which no potential is present in the e-mu and e-tau sectors. Finally we
quantify to what degree in this scenario it is possible to alleviate the
tension between the oscillation results for neutrinos and antineutrinos in the
MINOS experiment and show the relevance of the high energy part of the spectrum
measured at MINOS.Comment: PDFLaTeX file using JHEP3 class, 25 pages, 7 figures included.
Accepted for publication in JHE
Non-standard interactions versus non-unitary lepton flavor mixing at a neutrino factory
The impact of heavy mediators on neutrino oscillations is typically described
by non-standard four-fermion interactions (NSIs) or non-unitarity (NU). We
focus on leptonic dimension-six effective operators which do not produce
charged lepton flavor violation. These operators lead to particular
correlations among neutrino production, propagation, and detection non-standard
effects. We point out that these NSIs and NU phenomenologically lead, in fact,
to very similar effects for a neutrino factory, for completely different
fundamental reasons. We discuss how the parameters and probabilities are
related in this case, and compare the sensitivities. We demonstrate that the
NSIs and NU can, in principle, be distinguished for large enough effects at the
example of non-standard effects in the --sector, which basically
corresponds to differentiating between scalars and fermions as heavy mediators
as leading order effect. However, we find that a near detector at superbeams
could provide very synergistic information, since the correlation between
source and matter NSIs is broken for hadronic neutrino production, while NU is
a fundamental effect present at any experiment.Comment: 32 pages, 5 figures. Final version published in JHEP. v3: Typo in Eq.
(27) correcte
Probing non-standard interactions at Daya Bay
In this article we consider the presence of neutrino non-standard interactions (NSI) in the production and detection processes of reactor antineutrinos at the Daya Bay experiment. We report for the first time, the new constraints on the flavor non-universal and flavor universal charged-current NSI parameters, estimated using the currently released 621 days of Daya Bay data. New limits are placed assuming that the new physics effects are just inverse of each other in the production and detection processes. With this special choice of the NSI parameters, we observe a shift in the oscillation amplitude without distorting the L/E pattern of the oscillation probability. This shift in the depth of the oscillation dip can be caused by the NSI parameters as well as by theta(13), making it quite difficult to disentangle the NSI effects from the standard oscillations. We explore the correlations between the NSI parameters and theta(13) that may lead to significant deviations in the reported value of the reactor mixing angle with the help of iso-probability surface plots. Finally, we present the limits on electron, muon/tau, and flavor universal (FU) NSI couplings with and without considering the uncertainty in the normalization of the total event rates. Assuming a perfect knowledge of the event rates normalization, we find strong upper bounds similar to 0.1% for the electron and FU cases improving the present limits by one order of magnitude. However, for a conservative error of 5% in the total normalization, these constraints are relaxed by almost one order of magnitude
Non-Standard Interactions at a Neutrino Factory: Correlations and CP violation
We explore the potential of several Neutrino Factory (NF) setups to
constrain, discover and measure new physics effects due to Non-Standard
Interactions (NSI) in propagation through Earth matter. We first study the
impact of NSI in the measurement of : we find that these could be
large due to strong correlations of with NSI parameters in the
golden channel, and the inclusion of a detector at the magic baseline is
crucial in order to reduce them as much as possible. We present, then, the
sensitivity of the considered NF setups to the NSI parameters, paying special
attention to correlations arising between them and the standard oscillation
parameters, when all NSI parameters are introduced at once. Off-diagonal NSI
parameters could be tested down to the level of , whereas the diagonal
combinations and
can be tested down to and
, respectively. The possibilities of observing CP violation in this
context are also explored, by presenting a first scan of the CP discovery
potential of the NF setups to the phases and
. We study separately the case where CP violation comes only from
non-standard sources, and the case where it is entangled with the standard
source, . In case turns out to be CP conserving, the
interesting possibility of observing CP violation for reasonably small values
of the NSI parameters emerges.Comment: Final note added. 38 pages, 11 figure
Non-Standard Neutrino Interactions at One Loop
Neutrino oscillation experiments are known to be sensitive to Non-Standard
Interactions (NSIs). We extend the NSI formalism to include one-loop effects.
We discuss universal effects induced by corrections to the tree level W
exchange, as well as non-universal effects that can arise from scalar charged
current interactions. We show how the parameters that can be extracted from the
experiments are obtained from various loop amplitudes, which include vertex
corrections, wave function renormalizations, mass corrections as well as box
diagrams. As an illustrative example, we discuss NSIs at one loop in the
Minimal Supersymmetric Standard Model (MSSM) with generic lepton flavor
violating sources in the soft sector. We argue that the size of one-loop NSIs
can be large enough to be probed in future neutrino oscillation experiments.Comment: 27 pages, 4 figure
Euclid preparation: X. The Euclid photometric-redshift challenge
Forthcoming large photometric surveys for cosmology require precise and accurate photometric redshift (photo-z) measurements for the success of
their main science objectives. However, to date, no method has been able to produce photo-zs at the required accuracy using only the broad-band
photometry that those surveys will provide. An assessment of the strengths and weaknesses of current methods is a crucial step in the eventual
development of an approach to meet this challenge. We report on the performance of 13 photometric redshift code single value redshift estimates
and redshift probability distributions (PDZs) on a common set of data, focusing particularly on the 0.2−2.6 redshift range that the Euclid mission
will probe. We designed a challenge using emulated Euclid data drawn from three photometric surveys of the COSMOS field. The data was
divided into two samples: one calibration sample for which photometry and redshifts were provided to the participants; and the validation sample,
containing only the photometry to ensure a blinded test of the methods. Participants were invited to provide a redshift single value estimate and
a PDZ for each source in the validation sample, along with a rejection flag that indicates the sources they consider unfit for use in cosmological
analyses. The performance of each method was assessed through a set of informative metrics, using cross-matched spectroscopic and highlyaccurate photometric redshifts as the ground truth. We show that the rejection criteria set by participants are efficient in removing strong outliers,
that is to say sources for which the photo-z deviates by more than 0.15(1 + z) from the spectroscopic-redshift (spec-z). We also show that, while
all methods are able to provide reliable single value estimates, several machine-learning methods do not manage to produce useful PDZs. We find
that no machine-learning method provides good results in the regions of galaxy color-space that are sparsely populated by spectroscopic-redshifts,
for example z > 1. However they generally perform better than template-fitting methods at low redshift (z < 0.7), indicating that template-fitting
methods do not use all of the information contained in the photometry. We introduce metrics that quantify both photo-z precision and completeness
of the samples (post-rejection), since both contribute to the final figure of merit of the science goals of the survey (e.g., cosmic shear from Euclid).
Template-fitting methods provide the best results in these metrics, but we show that a combination of template-fitting results and machine-learning
results with rejection criteria can outperform any individual method. On this basis, we argue that further work in identifying how to best select
between machine-learning and template-fitting approaches for each individual galaxy should be pursued as a priority
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