2,034 research outputs found
Neutrinoless Double Beta Decay and CP Violation
We study the relation between the Majorana neutrino mass matrices and the
neutrinoless double beta decay when CP is not conserved. We give an explicit
form of the decay rate in terms of a rephasing invariant quantity and
demonstrate that in the presence of CP violation it is impossible to have
vanishing neutrinoless double beta decay in the case of two neutrino
generations (or when the third generation leptons do not mix with other leptons
and hence decouple).Comment: 9 pages, UTPT-93-1
Muonium-antimuonium conversion in models with heavy neutrinos
We study muonium-antimuonium conversion and mu+ e- to mu- e+ scattering
within two different lepton-flavor-violating models with heavy neutrinos: model
I is a typical seesaw that violates lepton number as well as flavor; model II
has a neutrino mass texture where lepton number is conserved. We look for the
largest possible amplitudes of these processes that are consistent with current
bounds. We find that model I has very limited chance of providing an observable
signal, except if a finely tuned condition in parameter space occurs. Model II,
on the other hand, requires no fine tuning and could cause larger effects.
However, the maximum amplitude provided by this model is still two orders of
magnitude below the sensitivity of current experiments: one predicts an
effective coupling G_MM up to 10^{-4}G_F for heavy neutrino masses near 10 TeV.
We have also clarified some discrepancies in previous literature on this
subject.Comment: 16 pages, 4 figures, reference adde
Neutrino wave function and oscillation suppression
We consider a thought experiment, in which a neutrino is produced by an
electron on a nucleus in a crystal. The wave function of the oscillating
neutrino is calculated assuming that the electron is described by a wave
packet. If the electron is relativistic and the spatial size of its wave packet
is much larger than the size of the crystal cell, then the wave packet of the
produced neutrino has essentially the same size as the wave packet of the
electron. We investigate the suppression of neutrino oscillations at large
distances caused by two mechanisms: 1) spatial separation of wave packets
corresponding to different neutrino masses; 2) neutrino energy dispersion for
given neutrino mass eigenstates. We resolve contributions of these two
mechanisms.Comment: 7 page
Multisensory causal inference in the brain
At any given moment, our brain processes multiple inputs from its different sensory modalities (vision, hearing, touch, etc.). In deciphering this array of sensory information, the brain has to solve two problems: (1) which of the inputs originate from the same object and should be integrated and (2) for the sensations originating from the same object, how best to integrate them. Recent behavioural studies suggest that the human brain solves these problems using optimal probabilistic inference, known as Bayesian causal inference. However, how and where the underlying computations are carried out in the brain have remained unknown. By combining neuroimaging-based decoding techniques and computational modelling of behavioural data, a new study now sheds light on how multisensory causal inference maps onto specific brain areas. The results suggest that the complexity of neural computations increases along the visual hierarchy and link specific components of the causal inference process with specific visual and parietal regions
Exploring CP Violation with B_d -> D K_s Decays
We (re)examine CP violation in the decays B_d -> D K_s, where D represents
D^0, D(bar), or one of their excited states. The quantity can be extracted from the time-dependent rates for and , where the decays to
. If one considers a non-CP-eigenstate hadronic final state to
which both D(bar) and D^0 can decay (e.g. ), then one can obtain two
of the angles of the unitarity triangle from measurements of the time-dependent
rates for and .
There are no penguin contributions to these decays, so all measurements are
theoretically clean.Comment: 15 pages, LaTeX, no figure
Remarks upon the mass oscillation formulas
The standard formula for mass oscillations is often based upon the
approximation and the hypotheses that neutrinos have been
produced with a definite momentum or, alternatively, with definite energy
. This represents an inconsistent scenario and gives an unjustified
reduction by a factor of two in the mass oscillation formulas. Such an
ambiguity has been a matter of speculations and mistakes in discussing flavour
oscillations. We present a series of results and show how the problem of the
factor two in the oscillation length is not a consequence of gedanken
experiments, i.e. oscillations in time. The common velocity scenario yields the
maximum simplicity.Comment: 9 pages, AMS-Te
Probing the Atmospheres of Planets Orbiting Microlensed Stars via Polarization Variability
We present a new method to identify and probe planetary companions of stars
in the Galactic Bulge and Magellanic Clouds using gravitational microlensing.
While spectroscopic studies of these planets is well beyond current
observational techniques, monitoring polarization fluctuations during high
magnification events induced by binary microlensing events will probe the
composition of the planetary atmospheres, an observation which otherwise is
currently unattainable even for nearby planetary systems.Comment: 7 pages, 2 figures. To appear in Astrophysical Journal Letter
Determining the Quark Mixing Matrix From CP-Violating Asymmetries
If the Standard Model explanation of CP violation is correct, then
measurements of CP-violating asymmetries in meson decays can in principle
determine the entire quark mixing matrix.Comment: 8 pages (plain TeX), 1 figure (postscript file appended), DAPNIA/SPP
94-06, NSF-PT-94-2, UdeM-LPN-TH-94-18
A determination of H_0 with the CLASS gravitational lens B1608+656: II. Mass models and the Hubble constant from lensing
EDITED FROM PAPER: We present mass models of the four-image gravitational
lens system B1608+656. A mass model for the lens galaxies has been determined
that reproduces the image positions, two out of three flux-density ratios and
the model time delays.
Using the time delays determined by Fassnacht et al. (1999a), we find that
the best isothermal mass model gives H_0=59^{+7}_{-6} km/s/Mpc for Omega_m=1
and Omega_l=0.0, or H_0=(65-63)^{+7}_{-6} km/s/Mpc for Omega_m=0.3 and Omega_l
= 0.0-0.7 (95.4% statistical confidence). A systematic error of +/-15 km/s/Mpc
is estimated.
This cosmological determination of H_0 agrees well with determinations from
three other gravitational lens systems (i.e. B0218+357, Q0957+561 and
PKS1830-211), SNe Ia, the S-Z effect and local determinations. The current
agreement on H_0 from four out of five gravitational lens systems (i)
emphasizes the reliability of its determination from isolated gravitational
lens systems and (ii) suggests that a close-to-isothermal mass profile can
describe disk galaxies, ellipticals and central cluster ellipticals.
The average of H_0 from B0218+357, Q0957+561, B1608+656 and PKS1830-211,
gives H_0(GL)=69 +/-7 km/s/Mpc for a flat universe with Omega_m=1 or H_0(GL)=74
+/-8 km/s/Mpc for Omega_m=0.3 and Omega_l=0.0-0.7. When including PG1115+080,
these values decrease to 64 +/-11 km/s/Mpc and 68 +/-13 km/s/Mpc (2-sigma
errors), respectively.Comment: Accepted for publication in ApJ. 34 pages, 4 figure
Getting beta-alpha without penguins
Oscillation effects in B0 -> Ks D0 and related processes are considered to
determine delta=beta-alpha+pi. We suggest that D0 decays to CP eigenstates used
in concert with inclusive D0 decays provide a powerful method for determining
delta cleanly i.e. without any complication from penguin processes. The CP
asymmetry is expected to be <=40% for D0 decays to non-CP eigenstates and <=80%
for decays to CP eigenstates. This method can lead to a fairly accurate
determination of delta with O(10^8-10^9) B-mesons.Comment: 4 pages 1 figure; Version 2: minor changes; references added; Some
changes in response to Referee Comment
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