45 research outputs found
Low-energy Phenomenology Of Scalarless Standard-Model Extensions With High-Energy Lorentz Violation
We consider renormalizable Standard-Model extensions that violate Lorentz
symmetry at high energies, but preserve CPT, and do not contain elementary
scalar fields. A Nambu--Jona-Lasinio mechanism gives masses to fermions and
gauge bosons, and generates composite Higgs fields at low energies. We study
the effective potential at the leading order of the large-N_{c} expansion,
prove that there exists a broken phase and study the phase space. In general,
the minimum may break invariance under boosts, rotations and CPT, but we give
evidence that there exists a Lorentz invariant phase. We study the spectrum of
composite bosons and the low-energy theory in the Lorentz phase. Our approach
predicts relations among the parameters of the low-energy theory. We find that
such relations are compatible with the experimental data, within theoretical
errors. We also study the mixing among generations, the emergence of the CKM
matrix and neutrino oscillations.Comment: 32 pages; v2: typos corrected, more references, some more comments -
PR
The Leptonic CP Phase from Muon Decay at Rest with Two Detectors
We propose a novel experimental setup for the determination of the leptonic
CP-violating phase delta using the decay at rest (DAR) of mu+ from a single
source located at distances of 10 and 30 km from two 20 kton organic liquid
scintillator detectors. The mu+ are created by bombarding a target with a 9 mA
beam of 800 MeV protons. With this proposal delta can be determined with a
precision of about 20 (15) degrees in 6 (12) years. In contrast with the
DAEdALUS project, only a single source is required and it runs with a duty
factor of 100 percent. Therefore 9 mA is the maximum instanteous current,
greatly reducing both the technological challenges and the costs.Comment: 5 pages, 11 figures, v3: matter effect included, error correcte
Showering Cosmogenic Muons in A Large Liquid Scintillator
We present the results of FLUKA simulations of the propagation of cosmogenic
muons in a 20 kton spherical liquid scintillator detector underneath 700 to 900
meters of rock. A showering muon is one which deposits at least 3 GeV in the
detector in addition to ionization energy. We find that 20 percent of muons are
showering and a further 10 percent of muon events are muon bundles of which
more than one muon enters the detector. In this range the showering and bundle
fractions are robust against changes in the depth and topography, thus the
total shower and bundle rate for a given experiment can be obtained by
combining our results with an estimate for the total muon flux. One consequence
is that a straightforward adaptation of the full detector showering muon cuts
used by KamLAND to JUNO or RENO 50 would yield a nearly vanishing detector
efficiency.Comment: 24 pages, 18 figures, v4: Improved precision of bundle rate
Measuring theta12 Despite an Uncertain Reactor Neutrino Spectrum
The recently discovered 5 MeV bump highlights that the uncertainty in the
reactor neutrino spectrum is far greater than some theoretical estimates.
Medium baseline reactor neutrino experiments will deliver by far the most
precise ever measurements of theta12. However, as a result of the bump, such a
determination of theta12 using the theoretical spectrum would yield a value of
sin^2(2theta12) which is more than 1% higher than the true value. We show that
by using recent measurements of the reactor neutrino spectrum the precision of
a measurement of theta12 at a medium baseline reactor neutrino experiment can
be improved appreciably. We estimate this precision as a function of the 9Li
spallation background veto efficiency and dead time.Comment: 8 pages, 2 eps figures, v3: Refs adde