899 research outputs found
Short-Baseline Electron Neutrino Disappearance, Tritium Beta Decay and Neutrinoless Double-Beta Decay
We consider the interpretation of the MiniBooNE low-energy anomaly and the
Gallium radioactive source experiments anomaly in terms of short-baseline
electron neutrino disappearance in the framework of 3+1 four-neutrino mixing
schemes. The separate fits of MiniBooNE and Gallium data are highly compatible,
with close best-fit values of the effective oscillation parameters Delta m^2
and sin^2 2 theta. The combined fit gives Delta m^2 >~ 0.1 eV^2 and 0.11 <
sin^2 2 theta < 0.48 at 2 sigma. We consider also the data of the Bugey and
Chooz reactor antineutrino oscillation experiments and the limits on the
effective electron antineutrino mass in beta-decay obtained in the Mainz and
Troitsk Tritium experiments. The fit of the data of these experiments limits
the value of sin^2 2 theta below 0.10 at 2 sigma. Considering the tension
between the neutrino MiniBooNE and Gallium data and the antineutrino reactor
and Tritium data as a statistical fluctuation, we perform a combined fit which
gives Delta m^2 \simeq 2 eV and 0.01 < sin^2 2 theta < 0.13 at 2 sigma.
Assuming a hierarchy of masses m_1, m_2, m_3 << m_4, the predicted
contributions of m_4 to the effective neutrino masses in beta-decay and
neutrinoless double-beta-decay are, respectively, between about 0.06 and 0.49
and between about 0.003 and 0.07 eV at 2 sigma. We also consider the
possibility of reconciling the tension between the neutrino MiniBooNE and
Gallium data and the antineutrino reactor and Tritium data with different
mixings in the neutrino and antineutrino sectors. We find a 2.6 sigma
indication of a mixing angle asymmetry.Comment: 14 pages; final version published in Phys.Rev.D82:053005,201
Lepton Numbers in the framework of Neutrino Mixing
In this short review we discuss the notion of lepton numbers. The strong
evidence in favor of neutrino oscillations obtained recently in the
Super-Kamiokande atmospheric neutrino experiment and in solar neutrino
experiments imply that the law of conservation of family lepton numbers L_e,
L_mu and L_tau is strongly violated. We consider the states of flavor neutrinos
nu_e, nu_mu and nu_tau and we discuss the evolution of these states in space
and time in the case of non-conservation of family lepton numbers due to the
mixing of light neutrinos. We discuss and compare different flavor neutrino
discovery experiments. We stress that experiments on the search for
nu_mu->nu_tau and nu_e->nu_tau oscillations demonstrated that the flavor
neutrino nu_tau is a new type of neutrino, different from nu_e and nu_mu. In
the case of neutrino mixing, the lepton number (only one) is connected with the
nature of massive neutrinos. Such conserved lepton number exist if massive
neutrinos are Dirac particles. We review possibilities to check in future
experiments whether the conserved lepton number exists.Comment: 20 page
Baryon Asymmetry of the Universe without Boltzmann or Kadanoff-Baym
We present a formalism that allows the computation of the baryon asymmetry of
the universe from first principles of statistical physics and quantum field
theory that is applicable to certain types of beyond the Standard Model physics
(such as the neutrino Minimal Standard Model -- MSM) and does not require
the solution of Boltzmann or Kadanoff-Baym equations. The formalism works if a
thermal bath of Standard Model particles is very weakly coupled to a new sector
(sterile neutrinos in the MSM case) that is out-of-equilibrium. The key
point that allows a computation without kinetic equations is that the number of
sterile neutrinos produced during the relevant cosmological period remains
small. In such a case, it is possible to expand the formal solution of the von
Neumann equation perturbatively and obtain a master formula for the lepton
asymmetry expressed in terms of non-equilibrium Wightman functions. The master
formula neatly separates CP-violating contributions from finite temperature
correlation functions and satisfies all three Sakharov conditions. These
correlation functions can then be evaluated perturbatively; the validity of the
perturbative expansion depends on the parameters of the model considered. Here
we choose a toy model (containing only two active and two sterile neutrinos) to
illustrate the use of the formalism, but it could be applied to other models.Comment: 26 pages, 10 figure
Towards a unique formula for neutrino oscillations in vacuum
We show that all correct results obtained by applying quantum field theory to
neutrino oscillations can be understood in terms of a single oscillation
formula. In particular, the model proposed by Grimus and Stockinger is shown to
be a subcase of the model proposed by Giunti, Kim and Lee, while the new
oscillation formulas proposed by Ioannisian and Pilaftsis and by Shtanov are
disproved. We derive an oscillation formula without making any relativistic
assumption and taking into account the dispersion, so that the result is valid
for both neutrinos and mesons. This unification gives a stronger
phenomenological basis to the neutrino oscillation formula. We also prove that
the coherence length can be increased without bound by more accurate energy
measurements. Finally, we insist on the wave packet interpretation of the
quantum field treatments of oscillations.Comment: 30 pages, 1 figure; the proof that plane wave oscillations do no
exist is extended to stationary models; the influence of dispersion is
explained in more detail
Local demands on sterile neutrinos
In a model independent manner, we explore the local implications of a single
neutrino oscillation measurement which cannot be reconciled within a
three-neutrino theory. We examine this inconsistency for a single region of
baseline to neutrino energy . Assuming that sterile neutrinos account for
the anomaly, we find that the {\it local} demands of this datum can require the
addition to the theory of one to three sterile neutrinos. We examine the
constraints which can be used to determine when more than one neutrino would be
required. The results apply only to a given region of . The question of
the adequacy of the sterile neutrinos to satisfy a global analysis is not
addressed here. Finally, using the results of a 3+2 analysis, we indicate
values for unknown mixing matrix elements which would require two sterile
neutrinos due to local demands only.Comment: 11 pages, 1 figure, discussion adde
What can the SNO Neutral Current Rate teach us about the Solar Neutrino Anomaly
We investigate how the anticipated neutral current rate from will
sharpen our understanding of the solar neutrino anomaly. Quantitative analyses
are performed with representative values of this rate in the expected range of
. This would provide a signal for transition
into a state containing an active neutrino component. Assuming this state to be
purely active one can estimate both the neutrino flux and the
survival probability to a much higher precision than currently possible.
Finally the measured value of the rate will have profound implications for
the mass and mixing parameters of the solar neutrino oscillation solution.Comment: Brief discussion on the first NC result from SNO added; final version
to be published in the MPL
Group velocity of neutrino waves
We follow up on the analysis of Mecozzi and Bellini (arXiv:1110:1253v1) where
they showed, in principle, the possibility of superluminal propagation of
neutrinos, as indicated by the recent OPERA result. We refine the analysis by
introducing wave packets for the superposition of energy eigenstates and
discuss the implications of their results with realistic values for the mixing
and mass parameters in a full three neutrino mixing scenario. Our analysis
shows the possibility of superluminal propagation of neutrino flavour in a very
narrow range of neutrino parameter space. Simultaneously this reduces the
number of observable events drastically. Therefore, the OPERA result cannot be
explained in this frame-work.Comment: 10 pages revtex with 2 figures. Important changes have been made; in
particular, it has been revised to include a discussion on the nature of the
measurement and its impact on the resul
Gopi: compiling linear and static channels in go
PTDC/CCI-COM/32166/2017We identify two important features to enhance the design of communication protocols specified in the pi-calculus, that are linear and static channels, and present a compiler, named GoPi, that maps high level specifications into executable Go programs. Channels declared as linear are deadlock-free, while the scope of static channels, which are bound by a hide declaration, does not enlarge at runtime; this is enforced statically by means of type inference, while specifications do not include annotations. Well-behaved processes are transformed into Go code that supports non-deterministic synchronizations and race-freedom. We sketch two main examples involving protection against message forwarding, and forward secrecy, and discuss the features of the tool, and the generated code. We argue that GoPi can support academic activities involving process algebras and formal models, which range from the analysis and testing of concurrent processes for research purposes to teaching formal languages and concurrent systems.publishersversionpublishe
Search for Oscillation of the Electron-Capture Decay Probability of Pm
We have searched for time modulation of the electron capture decay
probability of Pm in an attempt to confirm a recent claim from a group
at the Gesellschaft f\"{u}r Schwerionenforschung (GSI). We produced Pm
via the Sn(Na, 5n)Pm reaction at the Berkeley 88-Inch
Cyclotron with a bombardment time short compared to the reported modulation
period. Isotope selection by the Berkeley Gas-filled Separator is followed by
implantation and a long period of monitoring the Nd K x-rays
from the daughter. The decay time spectrum of the x-rays is well-described by a
simple exponential and the measured half-life of 40.68(53) seconds is
consistent with the accepted value. We observed no oscillatory modulation at
the proposed frequency at a level 31 times smaller than that reported by
Litvinov {\it et al.} (Phys. Lett. B 664 (2008) 162; arXiv:0801.2079
[nucl-ex]). A literature search for previous experiments that might have been
sensitive to the reported modulation uncovered another example in Eu
electron-capture decay. A reanalysis of the published data shows no oscillatory
behavior.Comment: 12 pages (double-spaced), 6 figure
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