464 research outputs found
Reactor Anti-Neutrino Oscillations and Gadolinium Loaded Super-Kamiokande Detector
We explore the potential of measuring the solar neutrino oscillation
parameters in the proposed gadolinium loaded Super-Kamiokande (SK-Gd) detector.
Gadolinium dissolved in water can detect neutrons much more efficiently than
pure water. This imparts the detector the ability to observe electron type
antineutrinos, transforming Super-Kamiokande into a huge reactor antineutrino
detector with an event rate approximately 43 times higher than that observed in
KamLAND. We simulate the reactor antineutrino data expected in this high
statistics detector. We use these prospective data to study the precision with
which the solar neutrino oscillation parameters, and
, can be determined i) with the SK-Gd detector, and ii)
by combining the SK-Gd data with the global data on solar neutrino
oscillations. For comparison and completeness the allowed regions of and , expected to be obtained from the data
of the solar neutrino and KamLAND experiments, are also presented.Comment: Includes Addendum with a brief discussion of the implications of the
766.3 kTy KamLAND spectrum data on the sensitivity of the SK-Gd experiment;
two new figures added in the Addendum; typos in Table 1 correcte
Revisiting Leptogenesis in a SUSY SU(5) x T' Model of Flavour
We investigate the generation of the baryon asymmetry of the Universe within
a SUSY SU(5) x T' model of flavour, which gives rise to realistic masses and
mixing patterns for quarks and leptons. The model employs the see-saw mechanism
for generation of the light neutrino masses and the baryon asymmetry is
produced via leptogenesis. We perform detailed calculations of both the CP
violating lepton asymmetries, originating from the decays of the heavy Majorana
neutrinos operative in the see-saw mechanism, and of the efficiency factors
which account for the lepton asymmetry wash-out processes in the Early
Universe. The latter are calculated by solving numerically the system of
Boltzmann equations describing the generation and the evolution of the lepton
asymmetries. The baryon asymmetry in the model considered is proportional to
the J_{CP} factor, which determines the magnitude of CP violation effects in
the oscillations of flavour neutrinos. The leptogenesis scale can be
sufficiently low, allowing to avoid the potential gravitino problem.Comment: 14 pages, 1 figure; published versio
Precision measurement of solar neutrino oscillation parameters by a long-baseline reactor neutrino experiment in Europe
We consider the determination of the solar neutrino oscillation parameters
and by studying oscillations of reactor
anti-neutrinos emitted by nuclear power plants (located mainly in France) with
a detector installed in the Frejus underground laboratory. The performances of
a water Cerenkov detector of 147 kt fiducial mass doped with 0.1% of Gadolinium
(MEMPHYS-Gd) and of a 50 kt scale liquid scintillator detector (LENA) are
compared. In both cases 3 uncertainties below 3% on
and of about 20% on can be obtained after one year of data
taking. The Gadolinium doped Super-Kamiokande detector (SK-Gd) in Japan can
reach a similar precision if the SK/MEMPHYS fiducial mass ratio of 1 to 7 is
compensated by a longer SK-Gd data taking time. Several years of reactor
neutrino data collected by MEMPHYS-Gd or LENA would allow a determination of
and with uncertainties of approximately
1% and 10% at 3, respectively. These accuracies are comparable to those
that can be reached in the measurement of the atmospheric neutrino oscillation
parameters and in long-baseline superbeam
experiments.Comment: 16 pages, 6 figure
Towards Complete Neutrino Mixing Matrix and CP-Violation
The compelling experimental evidences for oscillations of solar, atmospheric
and reactor neutrinos imply the existence of 3-neutrino mixing in vacuum. We
review the phenomenology of 3-neutrino mixing, and the current data on the
3-neutrino mixing parameters. The opened questions and the main goals of future
research in the field of neutrino mixing and oscillations are outlined. A
phenomenological approach for understanding the pattern of neutrino mixing as
an interplay between the mixing, arising from the charged lepton sector, and
bimaximal mixing, arising from a neutrino Majorana mass matrix, is considered
with emphasis on the CP-violating case. We comment also on planned future steps
in the experimental studies of neutrino mixing.Comment: Somewhat extended version (including additional comments, references
and figure) of the invited plenary talk given at the XXIst International
Conference on Neutrino Physics and Astrophysics, June 14-19, 2004, Paris,
France; 10 pages, 4 figure
Three-Neutrino Oscillations of Atmospheric Neutrinos, theta13, Neutrino Mass Hierarchy and Iron Magnetized Detectors
We derive predictions for the Nadir angle (theta_n) dependence of the ratio
Nmu-/Nmu+ of the rates of the mu- and mu+ multi-GeV events, and for the mu- -
mu+ event rate asymmetry, A_{mu-mu+}=[Nmu- - Nmu+]/[Nmu- + Nmu+], in
iron-magnetized calorimeter detectors (MINOS, INO) in the case of 3-neutrino
oscillations of the atmospheric nu_mu and antinu_mu, driven by one neutrino
mass squared difference, |Delta m^2_{31}| >> Delta m^2_{21}. The asymmetry
A_{mu- mu+} (the ratio Nmu-/Nmu+) is shown to be particularly sensitive to the
Earth matter effects in the atmospheric neutrino oscillations, and thus to the
values of sin^2(theta13) and sin^2(theta23), theta13 and theta23 being the
neutrino mixing angles limited by the CHOOZ and Palo Verde experiments and that
responsible for the dominant atmospheric nu_mu -> nu_tau (antinu_mu ->
antinu_tau) oscillations. It is also very sensitive to the type of neutrino
mass spectrum which can be with normal (Delta m^2_{31}>0) or with inverted
(Delta m^2_{31} 0.50, sin^2(2
theta13)>0.06 and Delta m^2_{31}=(2-3) 10^{-3} eV^2, the Earth matter effects
produce a relative difference between the integrated asymmetries barA_{mu- mu+}
and barA^{2nu}_{mu- mu+}$ in the mantle (cos(theta_n)=0.30-0.84) and core
(cos(theta_n)=0.84-1.0) bins, which is bigger in absolute value than ~15%, can
reach the values of (30-35)%, and thus can be sufficiently large to be
observable. The sign of the indicated asymmetry difference is anticorrelated
with the sign of Delta m^2_{31}. An observation of the Earth matter effects in
the Nadir angle distribution of the asymmetry A_{mu- mu+} (ratio Nmu-/Nmu+)
would clearly indicate that sin^2(2 theta13)>0.06 and sin^2(theta23)>0.50, and
would lead to the determination of the sign of Delta m^2_{31}.Comment: 27 pages, 9 figure
Pseudogap formation of four-layer BaRuO and its electrodynamic response changes
We investiaged the optical properties of four-layer BaRuO, which shows
a fermi-liquid-like behavior at low temperature. Its optical conductivity
spectra clearly displayed the formation of a pseudogap and the development of a
coherent peak with decreasing temperature. Temperature-dependences of the
density and the scattering rate of the coherent component were
also derived. As the temperature decreases, both and decrease for
four-layer BaRuO. These electrodynamic responses were compared with those
of nine-layer BaRuO, which also shows a pseudogap formation but has an
insulator-like state at low temperature. It was found that the relative rates
of change of both and determine either metallic or insulator-like
responses in the ruthenates. The optical properties of the four-layer ruthenate
were also compared with those of other pseudogap systems, such as high
cuprates and heavy electron systems.Comment: 7 figures. submitted to Phys. Rev.
Constraints on neutrino oscillation parameters from the SNO salt phase data
The physics implications of the just published salt phase data from the SNO
experiment are examined. The effect of these data on the allowed ranges of the
solar neutrino oscillation parameters, \Delta_m^2_{21} and
, are studied in the cases of two- and three- neutrino
mixing. In the latter case we derive an upper limit on the angle .
Constraints on the solar transitions into a mixture of active and
sterile neutrinos are also presented. Finally, we give predictions for the
day-night asymmetry in the SNO experiment, for the event rate in the BOREXINO
and LowNu experiments, and discuss briefly the constraints on the solar
neutrino oscillation parameters which can be obtained with prospective KamLAND
data.Comment: Version to appear in PL
Observables in Neutrino Mass Spectroscopy Using Atoms
The process of collective de-excitation of atoms in a metastable level into emission mode of a single photon plus a neutrino pair, called radiative emission of neutrino pair (RENP), is sensitive to the absolute neutrino mass scale, to the neutrino mass hierarchy and to the nature (Dirac or Majorana) of massive neutrinos. We investigate how the indicated neutrino mass and mixing observables can be determined from the measurement of the corresponding continuous photon spectrum taking the example of a transition between specific levels of the Yb atom. The possibility of determining the nature of massive neutrinos and, if neutrinos are Majorana fermions, of obtaining information about the Majorana phases in the neutrino mixing matrix, is analyzed in the cases of normal hierarchical, inverted hierarchical and quasi-degenerate types of neutrino mass spectrum. We find, in particular, that the sensitivity to the nature of massive neutrinos depends critically on the atomic level energy difference relevant in the RENP. \ua9 2013 Elsevier B.V
The Daya Bay and T2K results on sin22\u3b813 and non-standard neutrino interactions
We show that the relatively large best fit value of sin^22\u3b813=0.14(0.17) measured in the T2K experiment for fixed values of i) the Dirac CP violation phase \u3b4=0, and ii) the atmospheric neutrino mixing parameters \u3b8(23)=\u3c0/4, |\u394m^2(32)|=2.4
710^{ 123} eV^2, can be reconciled with the Daya Bay result sin^22\u3b8(13)=0.090\ub10.009 if the effects of non-standard neutrino interactions (NSI) in the relevant \u3bd\uafe\u2192\u3bd\uafe and \u3bd\u3bc\u2192\u3bde oscillation probabilities are taken into account. \ua9 2014 The Authors
Neutral top-pion and lepton flavor violating processes
In the context of topcolor-assisted techicolor(TC2) models, we study the
contributions of the neutral top-pion to the lepton flavor
violating(LFV) processes and .
We find that the present experimental bound on gives severe
constraints on the free parameters of models. Taking into account these
constraints, we consider the processes generated by
top-pion exchange at the tree-level and the one loop level, and obtain
, , in most of
the parameter space.Comment: latex files,16 pages, 6 figures. Submitted to Phys. Rev.
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