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ABSTRACT: Models, where neutrino mass originates from physics at the TeV scale and
which are potentially testable at the LHC, need additional suppression
mechanisms to describe the smallness of neutrino masses. We consider models in
which neutrino mass is generated from the d=7 operator $L L H_u H_u H_d H_u$ in
the context of SU(5) SUSY-GUTs, where the d=5 Weinberg operator can be
forbidden by a discrete symmetry. That is, we identify the embeddings in GUT
multiplets and their consequences for phenomenology and renormalization group
evolution. We use a specific example to exemplify the challenges. In this case,
additional heavy d-quarks are predicted, which are constrained by cosmology, in
particular, by big bang nucleosynthesis and direct searches for heavy nuclei.
We show that in the NMSSM extension of the model, the discrete symmetry needs
to be softly broken, and this soft-breaking can also be the origin of
deviations from tri-bimaximal mixings. Finally we demonstrate that our example
is the only tree level decomposition which is consistent with perturbativity up
to the GUT scale and neutrino mass generation by a leading d=7 contribution.
01/2013;
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ABSTRACT: We discuss the systematic decomposition of the dimension nine neutrinoless
double beta decay operator, focusing on mechanisms with potentially small
contributions to neutrino mass, while being accessible at the LHC. We first
provide a (d=9 tree-level) complete list of diagrams for neutrinoless double
beta decay. From this list one can easily recover all previously discussed
contributions to the neutrinoless double beta decay process, such as the
celebrated mass mechanism or "exotics", such as contributions from left-right
symmetric models, R-parity violating supersymmetry and leptoquarks. More
interestingly, however, we identify a number of new possibilities which have
not been discussed in the literature previously. Contact to earlier works based
on a general Lorentz-invariant parametrisation of the neutrinoless double beta
decay rate is made, which allows, in principle, to derive limits on all
possible contributions. We furthermore discuss possible signals at the LHC for
mediators leading to the short-range part of the amplitude with one specific
example. The study of such contributions would gain particular importance if
there were a tension between different measurements of neutrino mass such as
coming from neutrinoless double beta decay and cosmology or single beta decay.
12/2012;
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ABSTRACT: We study the physics potential of future long-baseline neutrino oscillation
experiments at large $\theta_{13}$, focusing especially on systematic
uncertainties. We discuss superbeams, \bbeams, and neutrino factories, and for
the first time compare these experiments on an equal footing with respect to
systematic errors. We explicitly simulate near detectors for all experiments,
we use the same implementation of systematic uncertainties for all experiments,
and we fully correlate the uncertainties among detectors, oscillation channels,
and beam polarizations as appropriate. As our primary performance indicator, we
use the achievable precision in the measurement of the CP violating phase
$\deltacp$. We find that a neutrino factory is the only instrument that can
measure $\deltacp$ with a precision similar to that of its quark sector
counterpart. All neutrino beams operating at peak energies $\gtrsim 2$ GeV are
quite robust with respect to systematic uncertainties, whereas especially
\bbeams and \thk suffer from large cross section uncertainties in the
quasi-elastic regime, combined with their inability to measure the appearance
signal cross sections at the near detector. A noteworthy exception is the
combination of a $\gamma=100$ \bbeam with an \spl-based superbeam, in which all
relevant cross sections can be measured in a self-consistent way. This provides
a performance, second only to the neutrino factory. For other superbeam
experiments such as \lbno and the setups studied in the context of the \lbne
reconfiguration effort, statistics turns out to be the bottleneck. In almost
all cases, the near detector is not critical to control systematics since the
combined fit of appearance and disappearance data already constrains the impact
of systematics to be small provided that the three active flavor oscillation
framework is valid.
09/2012;
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ABSTRACT: We demonstrate how the measurements of the Higgs-fermion and Higgs-gauge
boson couplings can be interpreted in terms of physics beyond the Standard
Model in a model-independent way. That is, we describe deviations from the
Standard Model by effective $d=6$ operators made of Higgs fields and gauge
fields, under the hypothesis that the new physics may show up in the Higgs
sector only and the effective operators are generated at tree level. While the
effective operator coefficients are independent in general, the completion of
the theory at high energies will lead to specific correlations which will be
recovered between Higgs-fermion and Higgs-gauge boson couplings. We demonstrate
that the current measurement of these couplings in terms of tree-level new
physics requires several new mediators with specific relationships among
different couplings. New insights in the effective theory and mediator spaces
can be expected for improved measurements from the inclusive $H \rightarrow
\tau \tau$ and the exclusive vector boson fusion-dominated $H \rightarrow
\gamma \gamma$ search channels, as well as the measurement of the Higgs
self-couplings, including higher order couplings which do not exist in the
Standard Model.
07/2012;
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ABSTRACT: We perform a systematic study of the $d=5$ Weinberg operator at the one-loop
level. We identify three different categories of neutrino mass generation: (1)
finite irreducible diagrams; (2) finite extensions of the usual seesaw
mechanisms at one-loop and (3) divergent loop realizations of the seesaws. All
radiative one-loop neutrino mass models must fall into one of these classes.
Case (1) gives the leading contribution to neutrino mass naturally and a
classic example of this class is the Zee model. We demonstrate that in order to
prevent that a tree level contribution dominates in case (2), Majorana fermions
running in the loop and an additional $\mathbb{Z}_2$ symmetry are needed for a
genuinely leading one-loop contribution. In the type-II loop extensions, the
lepton number violating coupling will be generated at one loop, whereas the
type-I/III extensions can be interpreted as loop-induced inverse or linear
seesaw mechanisms. For the divergent diagrams in category (3), the tree level
contribution cannot be avoided and is in fact needed as counter term to absorb
the divergence.
04/2012;
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ABSTRACT: There are recent considerations to increase the photomultiplier density in
the IceCube detector array beyond that of DeepCore, which will lead to a lower
detection threshold and a huge fiducial mass for the neutrino detection. This
initiative is known as "Phased IceCube Next Generation Upgrade" (PINGU). We
discuss the possibility to send a neutrino beam from one of the major
accelerator laboratories in the Northern hemisphere to such a detector. Such an
experiment would be unique in the sense that it would be the only neutrino beam
where the baseline crosses the Earth's core. We study the detector requirements
for a beta beam, a neutrino factory beam, and a superbeam, where we consider
both the cases of small theta_13 and large theta_13, as suggested by the recent
T2K and Double Chooz results. We illustrate that a flavor-clean beta beam best
suits the requirements of such a detector, in particular, that PINGU may
replace a magic baseline detector for small values of theta_13 -- even in the
absence of any energy resolution capability. For large theta_13, however, a
single-baseline beta beam experiment cannot compete if it is constrained by the
CERN-SPS. For a neutrino factory, because of the missing charge identification
possibility in the detector, a very good energy resolution is required. If this
can be achieved, especially a low energy neutrino factory, which does not
suffer from the tau contamination, may be an interesting option for large
theta_13. For the superbeam, where we use the LBNE beam as a reference,
electron neutrino flavor identification and statistics are two of the main
limitations. Finally, we demonstrate that, at least in principle, neutrino
factory and superbeam can measure the density of the Earth's core to the
sub-percent level for sin^2 2theta_13 larger than 0.01.
10/2011;
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ABSTRACT: We discuss neutrino masses from higher than d=5 effective operators in a
supersymmetric framework, where we explicitly demonstrate which operators could
be the leading contribution to neutrino mass in the MSSM and NMSSM. As an
example, we focus on the d=7 operator L L H_u H_u H_d H_u, for which we
systematically derive all tree-level decompositions. We argue that many of
these lead to a linear or inverse see-saw scenario with two extra neutral
fermions, where the lepton number violating term is naturally suppressed by a
heavy mass scale when the extra mediators are integrated out. We choose one
example, for which we discuss possible implementations of the neutrino flavor
structure. In addition, we show that the heavy mediators, in this case SU(2)
doublet fermions, may indeed be observable at the LHC, since they can be
produced by Drell-Yan processes and lead to displaced vertices when they decay.
However, the direct observation of lepton number violating processes is on the
edge at LHC.
09/2011;
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AIP Conf.Proc. 01/2011; 1382:97-99.
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ABSTRACT: We perform the baseline and energy optimization of the Neutrino Factory
including the latest simulation results on the magnetized iron detector (MIND).
We also consider the impact of tau decays, generated by nu_mu to nu_tau or nu_e
to nu_tau appearance, on the mass hierarchy, CP violation, and theta_{13}
discovery reaches, which we find to be negligible for the considered detector.
For the baseline-energy optimization for small theta_{13}, we qualitatively
recover the results with earlier simulations of the MIND detector. We find
optimal baselines of about 2500 km to 5000 km for the CP violation measurement,
where now values of E_mu as low as about 12 GeV may be possible. However, for
large theta_{13}, we demonstrate that the lower threshold and the backgrounds
reconstructed at lower energies allow in fact for muon energies as low as 5 GeV
at considerably shorter baselines, such as FNAL-Homestake. This implies that
with the latest MIND analysis, low- and high-energy versions of the Neutrino
Factory are just two different versions of the same experiment optimized for
different parts of the parameter space. Apart from a green-field study of the
updated detector performance, we discuss specific implementations for the
two-baseline Neutrino Factory, where the considered detector sites are taken to
be currently discussed underground laboratories. We find that reasonable setups
can be found for the Neutrino Factory source in Asia, Europe, and North
America, and that a triangular-shaped storage ring is possible in all cases
based on geometrical arguments only.
12/2010;
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ABSTRACT: We study perturbations of exactly tri-bimaximal neutrino mixings under the
assumption that they are coming solely from the charged lepton mass matrix.
This may be plausible in scenarios where the mass generation mechanisms of
neutrinos and charged leptons/quarks have a different origin. As a working
hypothesis, we assume mass textures which may be generated by the
Froggatt-Nielsen mechanism for the charged lepton and quark sectors, which
generically leads to strong hierarchies, whereas the neutrino sector is exactly
tri-bimaximal with a mild (normal) hierarchy. We find that in this approach,
deviations from maximal atmospheric mixing can be introduced without affecting
theta_13 and theta_12, whereas a deviation of theta_13 or theta_12 from its
tri-bimaximal value will inevitably lead to a similar-sized deviation of the
other parameter. Therefore, the already very precise knowledge of theta_12
points towards small sin^2(2 theta_13) <= 0.01. The magnitude of this deviation
can be controlled by the specific form of the charged lepton texture.
12/2010;
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Rodrigo Alonso,
Stefan Antusch,
Mattias Blennow,
Pilar Coloma,
Andre de Gouvea,
Enrique Fernandez-Martinez,
Belen Gavela,
Concha Gonzalez-Garcia,
Sergio Hortner,
Marco Laveder, [......],
Toshihiko Ota,
Sergio Palomares-Ruiz,
Adam Para,
Stephen J. Parke,
Nuria Rius,
Thomas Schwetz-Mangold,
F J P Soler,
Michel Sorel,
Osamu Yasuda, Walter Winter
[show abstract]
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ABSTRACT: Recent developments on tau detection technologies and the construction of high intensity neutrino beams open the possibility of a high precision search for non-standard {\mu} - {\tau} flavour transition with neutrinos at short distances. The MINSIS - Main Injector Non-Standard Interaction Search- is a proposal under discussion to realize such precision measurement. This document contains the proceedings of the workshop which took place on 10-11 December 2009 in Madrid to discuss both the physics reach as well as the experimental requirements for this proposal. Comment: Proceedings of the MINSIS Workshop, Dec 10-11, 2009 in Madrid. 15 pages latex
09/2010;
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ABSTRACT: We discuss the effects of one additional sterile neutrino at the Neutrino Factory. Compared to earlier analyses, which have been motivated by LSND results, we do not impose any constraint on the additional mass squared splitting. This means that the additional mass eigenstate could, with small mixings, be located among the known ones, as it is suggested by the recent analysis of cosmological data. We use a self-consistent framework at the Neutrino Factory without any constraints on the new parameters. We demonstrate for a combined short and long baseline setup that near detectors can provide the expected sensitivity at the LSND-motivated \Delta m_{41}^2-range, while some sensitivity can also be obtained in the region of the atmospheric mass splitting from the long baselines. We point out that limits on such very light sterile neutrinos may also be obtained from a re-analysis of atmospheric and solar neutrino oscillation data, as well as from supernova neutrino observations. In the second part of the analysis, we compare our sensitivity with the existing literature using additional assumptions, such as |\Delta m_{41}^2| \gg |\Delta m_{31}^2| leading to averaging of the fast oscillations in the far detectors. We demonstrate that while the Neutrino Factory has excellent sensitivity compared to existing studies using similar assumptions, one has to be very careful interpreting these results for a combined short and long baseline setup where oscillations could occur in the near detectors. We also test the impact of additional \nu_\tau detectors at the short and long baselines, and we do not find a substantial improvement of the sensitivities. Comment: 23 pages with 8 figures and 1 table included. More references added
07/2010;
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ABSTRACT: 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 $\mu$-$\tau$-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.
Journal of High Energy Physics 04/2010; 2010(4):041. · 5.83 Impact Factor
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ABSTRACT: We discuss neutrino oscillation physics with a neutrino factory in stages, including the possibility of upgrading the muon energy within the same program. We point out that a detector designed for the low energy neutrino factory may be used off-axis in a high energy neutrino factory beam. We include the re-optimization of the experiment depending on the value of theta_13 found. As upgrade options, we consider muon energy, additional baselines, a detector mass upgrade, an off-axis detector, and the platinum (muon to electron neutrino) channels. In addition, we test the impact of Daya Bay data on the optimization. We find that for large theta_13 (theta_13 discovered by the next generation of experiments), a low energy neutrino factory might be the most plausible minimal version to test the unknown parameters. However, if a higher muon energy is needed for new physics searches, a high energy version including an off-axis detector may be an interesting alternative. For small theta_13 (theta_13 not discovered by the next generation), a plausible program could start with a low energy neutrino factory, followed by energy upgrade, and then baseline or detector mass upgrade, depending on the outcome of the earlier phases. Comment: 23 pages, 10 (color) figures. Minor clarifications and changes. Final version to appear in PRD
11/2009;
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ABSTRACT: The geometric effects of the beam in near detectors at a neutrino factory are discussed. The refined systematics treatment, including cross section errors, flux errors and background uncertainties, is compared with the IDS-NF one. Different near detector setups are included. We also probe their effects both at the measurements of standard neutrino oscillation parameters and constraints of the non-standard neutrino interaction. Comment: Based on the talk JT gave at NuFact09, Fermilab and IIT, Chicago, July 20-25, 2009. More references added
09/2009;
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ABSTRACT: We discuss short-baseline and very-short-baseline electron neutrino disappearance at a neutrino factory. We take into account geometric effects, such as from averaging over the decay straights, and the uncertainties of the cross sections. We follow an approach similar to reactor experiments with two detectors: we use two sets of near detectors at different distances to cancel systematics. We demonstrate that such a setup is very robust with respect to systematics, and can have excellent sensitivities to the effective mixing angle and squared-mass splitting. In addition, we allow for CPT invariance violation, which can be tested (depending on the parameters) up to a 0.1% level. Comment: 21 pages. Final version published in Phys. Rev. D80 (2009) 073005
07/2009;
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ABSTRACT: We discuss the generation of small neutrino masses from effective operators higher than dimension five, which open new possibilities for low scale see-saw mechanisms. In order to forbid the radiative generation of neutrino mass by lower dimensional operators, extra fields are required, which are charged under a new symmetry. We discuss this mechanism in the framework of a two Higgs doublet model. We demonstrate that the tree level generation of neutrino mass from higher dimensional operators often leads to inverse see-saw scenarios in which small lepton number violating terms are naturally suppressed by the new physics scale. Furthermore, we systematically discuss tree level generalizations of the standard see-saw scenarios from higher dimensional operators. Finally, we point out that higher dimensional operators can also be generated at the loop level. In this case, we obtain the TeV scale as new physics scale even with order one couplings. Comment: 22 pages, 3 figures, 2 tables. Some references added
Journal of High Energy Physics 07/2009; · 5.83 Impact Factor
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ABSTRACT: We compare the physics potential of the upcoming neutrino oscillation experiments Daya Bay, Double Chooz, NOvA, RENO, and T2K based on their anticipated nominal luminosities and schedules. After discussing the sensitivity to theta_{13} and the leading atmospheric parameters, we demonstrate that leptonic CP violation will hardly be measurable without upgrades of the T2K and NOvA proton drivers, even if theta_{13} is large. In the presence of the proton drivers, the fast track to hints for CP violation requires communication between the T2K and NOvA collaborations in terms of a mutual synchronization of their neutrino-antineutrino run plans. Even in that case, upgrades will only discover CP violation in a relatively small part of the parameter space at the 3 sigma confidence level, while 90% confidence level hints will most likely be obtained. Therefore, we conclude that a new facility will be required if the goal is to obtain a significant result with high probability. Comment: 27 pages, 12 figures
07/2009;
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ABSTRACT: We discuss the impact of near detectors at a neutrino factory both on standard oscillation and non-standard interaction measurements. Our systematics treatment includes cross section errors, flux errors, and background uncertainties, and our near detector fluxes include the geometry of the neutrino source and the detector. Instead of a specific detector concept, we introduce qualitatively different classes of near detectors with different characteristics, such as near detectors catching the whole neutrino flux (near detector limit) versus near detectors observing a spectrum similar to that of the far detector (far detector limit). We include the low energy neutrino factory in the discussion. We illustrate for which measurements near detectors are required, discuss how many are needed, and what the role of the flux monitoring is. For instance, we demonstrate that near detectors are mandatory for the leading atmospheric parameter measurements if the neutrino factory has only one baseline, whereas systematical errors partially cancel if the neutrino factory complex includes the magic baseline. Finally, near detectors with nu_tau detection are shown to be useful for non-standard interactions. Comment: 32 pages, 13 figures, 4 tables. Minor changes, clarifications added. Version to appear in Phys. Rev. D
03/2009;
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ABSTRACT: We study the optimization of a neutrino factory with respect to nonstandard neutral current neutrino interactions, and compare the results to those obtained without nonstandard interactions. We discuss the muon energy, baselines, and oscillation channels as degrees of freedom. Our conclusions are based on both analytical calculations and on a full numerical simulation of the neutrino factory setup proposed by the international design study (IDS-NF). We consider all possible nonstandard parameters, and include their complex phases. We identify the impact of the different parameters on the golden, silver, and disappearance channels. We come to the conclusion that, even in the presence of nonstandard interactions, the performance of the neutrino factory hardly profits from a silver channel detector, unless the muon energy is significantly increased compared to the IDS-NF setup. Apart from the dispensable silver channel detector, we demonstrate that the IDS-NF setup is close to optimal even if nonstandard interactions are considered. We find that one very long baseline is a key component in the search for nonstandard interactions, in particular, for |ϵμτm| and |ϵττm|.
Phys. Rev. D. 09/2008; 78(5).
