474 research outputs found
Global analysis of muon decay measurements
We have performed a global analysis of muon decay measurements to establish
model-independent limits on the space-time structure of the muon decay matrix
element. We find limits on the scalar, vector and tensor coupling of right- and
left-handed muons to right- and left-handed electrons. The limits on those
terms that involve the decay of right-handed muons to left-handed electrons are
more restrictive than in previous global analyses, while the limits on the
other non-standard model interactions are comparable. The value of the Michel
parameter eta found in the global analysis is -0.0036 \pm 0.0069, slightly more
precise than the value found in a more restrictive analysis of a recent
measurement. This has implications for the Fermi coupling constant G_F.Comment: 5 pages, 3 table
A new experiment to search for the invisible decay of the orthopositronium
We propose an experiment to search for invisible decays of orthopositronium
(o-Ps) with a 90% confidence sensitivity in the branching ratio as low as
. Evidence for this decay mode would unambigously signal new physics:
either the existence of extra--dimensions or fractionally charged particles or
new light gauge bosons. The experimental approach and the detector components
of the proposed experiment are described.Comment: Based on a talk given at Workshop on Positronium Physics, Zurich,
Switzerland, 30-31 May 200
Measurement of the Michel Parameter xi" in Polarized Muon Decay and Implications on Exotic Couplings of the Leptonic Weak Interaction
The Michel parameter xi" has been determined from a measurement of the
longitudinal polarization of positrons emitted in the decay of polarized and
depolarized muons. The result, xi" = 0.981 +- 0.045stat +- 0.003syst, is
consistent with the Standard Model prediction of unity, and provides an order
of magnitude improvement in the relative precision of this parameter. This
value sets new constraints on exotic couplings beyond the dominant V-A
description of the leptonic weak interaction.Comment: 15 pages, 16 figures, 3 tables; submitted to Phys. Rev.
Differential Cross Section and Vector Polarization for the elastic scattering of 41 to 51 MeV Deuterons on Carbon
Differentieller Wirkungsquerschnitt fuer die elastische ³He + ⁴He-Streuung bei Energien von 28 bis 44 MeV im Schwerpunktsystem
Virtual and Soft Pair Corrections to Polarized Muon Decay Spectrum
Radiative corrections to the muon decay spectrum due to soft and virtual
electron--positron pairs are calculated.Comment: 10pp, 2 PS figs, details of calculations are adde
Decay of polarized muon at rest as a source of polarized neutrino beam
In this paper, we indicate the theoretical possibility of using the decay of
polarized muons at rest as a source of the transversely polarized electron
antineutrino beam. Such a beam can be used to probe new effects beyond standard
model. We mean here new tests concerning CP violation, Lorentz structure and
chirality structure of the charged current weak interactions. The main goal is
to show how the energy and angular distribution of the electron antineutrinos
in the muon rest frame depends on the transverse components of the antineutrino
beam polarization. Our analysis is model-independent and consistent with the
current upper limits on the non-standard couplings. The results are presented
in a limit of infinitesimally small mass for all particles produced in the
decay.Comment: elsart style, 11 pages, 2 eps figures, submitted do publicatio
An Improved Limit on Invisible Decays of Positronium
The results of a new search for positronium decays into invisible final
states are reported. Convincing detection of this decay mode would be a strong
evid ence for new physics beyond the Standard Model (SM): for example the
existence of extra--dimensions, of milli-charged particles, of new light gauge
bosons or of mirror particles. Mirror matter could be a relevant dark matter
candidate.
In this paper the setup and the results of a new experiment are presented. In
a collected sample of about orthopositronium decay
s, no evidence for invisible decays in an energy window [0,80] keV was found
and an upper limit on the branching ratio of orthopositronium \invdecay could
be set: \binvdecay<4.2\times 10^{-7} (90% C.L.)
Our results provide a limit on the photon mirror-photon mixing strength
(90% C.L.) and rule out particles lighter
than the electron mass with a fraction of the
electron charge. Furthermore, upper limits on the branching ratios for the
decay of parapositronium (90%
C.L.) and the direct annihilation (90% C.L.) could be set.Comment: 17 pages, 7 figures, added references, fixed limit on millicharged
particles and changed two plots accordingl
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