1,137 research outputs found

### Neutrino Physics

The Standard Model has been incredibly successful in predicting the outcome
of almost all the experiments done up so far. In it, neutrinos are mass-less.
However, in recent years we have accumulated evidence pointing to tiny masses
for the neutrinos (as compared to the charged leptons). These masses allow
neutrinos to change their flavour and oscillate. In these lectures I review the
properties of neutrinos in and beyond the Standard Model.Comment: 19 pages, contribution to the 2012 European School of High-Energy
Physics, La Pommeraye, Anjou, France, 06-19 Jun 2012, edited by C. Grojean
and M. Mulders. arXiv admin note: text overlap with arXiv:hep-ph/0506165 by
other author

### Neutrinos: Fast & Curious

The Standard Model has been effective way beyond expectations in foreseeing
the result of almost all the experimental tests done up so far. In it,
neutrinos are massless. Nonetheless, in recent years we have collected solid
proofs indicating little but non zero masses for the neutrinos (when contrasted
with those of the charged leptons). These masses permit neutrinos to change
their flavor and oscillate, indeed a unique treat. In these lectures, I discuss
the properties and the amazing potential of neutrinos in and beyond the
Standard Model.Comment: 22 pages, contribution to the 2016 European School of High-Energy
Physics, Skeikampen, Norway , 15 - 28 June 2016, to appear as a CERN Yellow
Report. arXiv admin note: substantial text overlap with arXiv:1504.0703

### On the Effective Mass of the Electron Neutrino in Beta Decay

In the presence of mixing between massive neutrino states, the distortion of
the electron spectrum in beta decay is, in general, a function of several
masses and mixing angles. For $3\nu$-schemes which describe the solar and
atmospheric neutrino data, this distortion can be described by a single
effective mass, under certain conditions. In the literature, two different
definitions for the effective mass have been suggested. We show that for
quasi-degenerate mass schemes (with an overall mass scale $m$ and splitting
$\Delta m^2$) the two definitions coincide up to $(\Delta m^2)^2/m^4$
corrections. We consider the impact of different effective masses on the
integral energy spectrum. We show that the spectrum with a single mass can be
used also to fit the data in the case of $4\nu$-schemes motivated, in
particular, by the LSND results. In this case the accuracy of the mass
determination turns out to be better than $(10 - 15)%$.Comment: 15 pages, Version to appear in Phys. Lett.

### Neutrinos that violate CPT, and the experiments that love them

Recently we proposed a framework for explaining the observed evidence for
neutrino oscillations without enlarging the neutrino sector, by introducing CPT
violating Dirac masses for the neutrinos. In this paper we continue the
exploration of the phenomenology of CPT violation in the neutrino sector. We
show that our CPT violating model fits the existing SuperKamiokande data at
least as well as the standard atmospheric neutrino oscillation models. We
discuss the challenge of measuring CP violation in a neutrino sector that also
violates CPT. We point out that the proposed off-axis extension of MINOS looks
especially promising in this regard. Finally, we describe a method to compute
CPT violating neutrino effects by mocking them up with analog matter effects.Comment: 17 pages, 3 eps figure

### Quintessence, inflation and baryogenesis from a single pseudo-Nambu-Goldstone boson

We exhibit a model in which a single pseudo-Nambu-Goldstone boson explains
dark energy, inflation and baryogenesis. The model predicts correlated signals
in future collider experiments, WIMP searches, proton decay experiments, dark
energy probes, and the PLANCK satellite CMB measurements.Comment: 16 pages, 3 color figure

### Tau neutrinos from muon storage rings

Charged tau leptons emerging in a long baseline experiment with a muon
storage ring and a far-away detector will positively establish neutrino
oscillations. We study the conversion of $\nu_\mu$ ($\bar{\nu}_\mu$) and of
$\bar{\nu}_e$ ($\nu_e$) to $\nu_\tau$ or $\bar{\nu}_\tau$ for neutrinos from a
20 GeV muon storage ring, within the strong mixing scheme and on the basis of
the squared mass differences which are compatible with all reported neutrino
anomalies, including the LSND data. In contrast to other solutions which ignore
the Los Alamos anomaly, we find charged tau production rates which should be
measurable in a realistic set up. As a consequence, determining the complete
mass spectrum of neutrinos as well as all three mixing angles seems within
reach. Matter effects are discussed thoroughly but are found to be small in
this situation.Comment: 11 pages, 5 postscript figures (eps

### Distributed Deterministic Edge Coloring using Bounded Neighborhood Independence

We study the {edge-coloring} problem in the message-passing model of
distributed computing. This is one of the most fundamental and well-studied
problems in this area. Currently, the best-known deterministic algorithms for
(2Delta -1)-edge-coloring requires O(Delta) + log-star n time \cite{PR01},
where Delta is the maximum degree of the input graph. Also, recent results of
\cite{BE10} for vertex-coloring imply that one can get an
O(Delta)-edge-coloring in O(Delta^{epsilon} \cdot \log n) time, and an
O(Delta^{1 + epsilon})-edge-coloring in O(log Delta log n) time, for an
arbitrarily small constant epsilon > 0.
In this paper we devise a drastically faster deterministic edge-coloring
algorithm. Specifically, our algorithm computes an O(Delta)-edge-coloring in
O(Delta^{epsilon}) + log-star n time, and an O(Delta^{1 +
epsilon})-edge-coloring in O(log Delta) + log-star n time. This result improves
the previous state-of-the-art {exponentially} in a wide range of Delta,
specifically, for 2^{Omega(\log-star n)} \leq Delta \leq polylog(n). In
addition, for small values of Delta our deterministic algorithm outperforms all
the existing {randomized} algorithms for this problem.
On our way to these results we study the {vertex-coloring} problem on the
family of graphs with bounded {neighborhood independence}. This is a large
family, which strictly includes line graphs of r-hypergraphs for any r = O(1),
and graphs of bounded growth. We devise a very fast deterministic algorithm for
vertex-coloring graphs with bounded neighborhood independence. This algorithm
directly gives rise to our edge-coloring algorithms, which apply to {general}
graphs.
Our main technical contribution is a subroutine that computes an
O(Delta/p)-defective p-vertex coloring of graphs with bounded neighborhood
independence in O(p^2) + \log-star n time, for a parameter p, 1 \leq p \leq
Delta

### MINOS and CPT-violating neutrinos

We review the status of CPT violation in the neutrino sector. Apart from
LSND, current data favors three flavors of light stable neutrinos and
antineutrinos, with both halves of the spectrum having one smaller mass
splitting and one larger mass splitting. Oscillation data for the smaller
splitting is consistent with CPT. For the larger splitting, current data favor
an antineutrino mass-squared splitting that is an order of magnitude larger
than the corresponding neutrino splitting, with the corresponding mixing angle
less-than-maximal. This CPT-violating spectrum is driven by recent results from
MINOS, but is consistent with other experiments if we ignore LSND. We describe
an analysis technique which, together with MINOS running optimized for muon
antineutrinos, should be able to conclusively confirm the CPT-violating
spectrum proposed here, with as little as three times the current data set. If
confirmed, the CPT-violating neutrino mass-squared difference would be an order
of magnitude less than the current most-stringent upper bound on CPT violation
for quarks and charged leptons.Comment: 18 pages, title change, version to appear in Physical Review

- …