636 research outputs found
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
Higgs Sector of the Minimal Left-Right Symmetric Model
We perform an exhaustive analysis of the most general Higgs sector of the
minimal left-right symmetric model (MLRM). We find that the CP properties of
the vacuum state are connected to the Higgs spectrum: if CP is broken
spontaneously, the MLRM does not approach the Standard Model in the limit of a
decoupling left-right symmetry breaking scale. Depending on the size of the CP
phases scenarios with extra non-decoupling flavor-violating doublet Higgses or
very light SU(2) triplet Higgses emerge, both of which are ruled out by
phenomenology. For zero CP phases the non-standard Higgses decouple only if a
very unnatural fine-tuning condition is fulfilled. We also discuss
generalizations to a non-minimal Higgs sector.Comment: brief discussion of non-minimal Higgs sectors added, journal versio
METing SUSY on the Z peak
Recently the ATLAS experiment announced a 3 excess at the Z-peak
consisting of 29 pairs of leptons together with two or more jets, GeV and GeV, to be compared with
expected lepton pairs in the Standard Model. No excess outside the Z-peak was
observed. By trying to explain this signal with SUSY we find that only
relatively light gluinos, TeV, together with a
heavy neutralino NLSP of GeV decaying
predominantly to Z-boson plus a light gravitino, such that nearly every gluino
produces at least one Z-boson in its decay chain, could reproduce the excess.
We construct an explicit general gauge mediation model able to reproduce the
observed signal overcoming all the experimental limits. Needless to say, more
sophisticated models could also reproduce the signal, however, any model would
have to exhibit the following features, light gluinos, or heavy particles with
a strong production cross-section, producing at least one Z-boson in its decay
chain. The implications of our findings for the Run II at LHC with the scaling
on the Z peak, as well as for the direct search of gluinos and other SUSY
particles, are pointed out.Comment: 24 pages, 17 figures, simulation improved, Checkmate analysis added,
new benchmark point included. Typos corrected, conclusions unchange
Neutrino oscillation probabilities through the looking glass
In this paper we review different expansions for neutrino oscillation
probabilities in matter in the context of long-baseline neutrino experiments.
We examine the accuracy and computational efficiency of different exact and
approximate expressions. We find that many of the expressions used in the
literature are not precise enough for the next generation of long-baseline
experiments, but several of them are while maintaining comparable simplicity.
The results of this paper can be used as guidance to both phenomenologists and
experimentalists when implementing the various oscillation expressions into
their analysis tools.Comment: 32 pages, 6 figure
Spontaneous CP violation and the B system
We investigate effects of spontaneous breakdown of CP in
systems in left-right symmetric models.
Assuming that the left-right contribution to the matrix
element can be at most equal to the standard model one we obtain a new
lower bound, M_H\gsim 12 TeV, on the flavour changing Higgs boson mass. Most
importantly, the convention independent parameter
which measures the amount of CP violation, can be enhanced by a
factor of four or more for and almost by two orders of magnitude for
systems when compared with the Standard Model predictions. Therefore,
interesting possibilities to observe indirect CP violation in the system
are open in the planned facilities.Comment: 19 pages, LATEX, 4 postscript figures include
Anatomy of Mixing-Induced CP Asymmetries in Left-Right-Symmetric Models with Spontaneous CP Violation
We investigate the pattern of CP violation in K, B_d and B_s mixing in a
symmetrical SU(2)_R x SU(2)_L x U(1) model with spontaneous CP violation. We
calculate the phases of the left and right quark mixing matrices beyond the
small phase approximation and perform a careful analysis of all relevant
restrictions on the model's parameters from Delta m_K, Delta m_B, epsilon,
epsilon'/epsilon and the CP asymmetry in B->J/psi K_S. We find that, with
current experimental data, the mass of the right-handed charged gauge boson,
M2, is restricted to be in the range 2.75 to 13 TeV and the mass of the
flavour-changing neutral Higgs boson, MH, in 10.2 to 14.6 TeV. This means in
particular that the decoupling limit M2, MH -> infinity is already excluded by
experiment. We also find that the model favours opposite signs of epsilon and
sin 2beta and is excluded if sin 2beta > 0.1.Comment: 33 pages Latex with 11 Postscript-Figures (included
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