48 research outputs found
The decays within the standard model
We study the reactions within the
minimal standard model. We use isospin symmetry to relate the matrix elements
to the form factors measured in . We argue that these modes are
short distance dominated and can be used for precise determinations of the CKM
parameters and . Depending on the value of the CKM angles we find
branching ratios in the following ranges: ; ; . We also discuss a possible -odd
observable.Comment: 10 pages, LaTeX, 2 Postscript figures. Title and abstract have been
revised to better reflect the content of the paper. This is the final version
as publishe
Signatures of heavy Majorana neutrinos and HERA's isolated lepton events
The graph of neutrinoless double beta decay is applied to HERA and
generalized to final states with any two charged leptons. Considered is the
case in which one of the two escapes typical identification criteria and the
case when a produced tau decays hadronically. Both possibilities give one
isolated lepton with high transverse momentum, hadronic activity and an
imbalance in transverse momentum. We examine the kinematical properties of
these events and compare them with the high p_T isolated leptons reported by
the H1 collaboration. Their positive charged muon events can be explained by
the ``double beta'' process and we discuss possibilities for the precise
determination which original final state produced the single isolated lepton.
To confirm our hypothesis one should search in the data for high pseudorapidity
and/or low p_T leptons or for additional separated jets.Comment: 19 pages with 14 figures, minor change
Search for the decay in the momentum region
We have searched for the decay in the kinematic
region with pion momentum below the peak. One event was
observed, consistent with the background estimate of . This
implies an upper limit on
(90% C.L.), consistent with the recently measured branching ratio of
, obtained using the standard model
spectrum and the kinematic region above the peak. The
same data were used to search for , where is a weakly
interacting neutral particle or system of particles with .Comment: 4 pages, 2 figure
Search for the decay K+ to pi+ gamma gamma in the pi+ momentum region P>213 MeV/c
We have searched for the K+ to pi+ gamma gamma decay in the kinematic region
with pi+ momentum close to the end point. No events were observed, and the 90%
confidence-level upper limit on the partial branching ratio was obtained, B(K+
to pi+ gamma gamma, P>213 MeV/c) < 8.3 x 10-9 under the assumption of chiral
perturbation theory including next-to-leading order ``unitarity'' corrections.
The same data were used to determine an upper limit on the K+ to pi+ gamma
branching ratio of 2.3 x 10-9 at the 90% confidence level.Comment: 15 pages, 3 figures; no change in the results, accepted for
publication in Physics Letters
Rare Decays
The rare decays of the meson have had a long tradition as a laboratory
for testing the symmetry properties of the weak interactions, and the manner in
which these symmetries are broken by higher order effects. Present--day
interest is focussed on decays that are suppressed by --symmetry or GIM
symmetry. Such decays, in the standard theory, are sensitive to effects of the
virtual top quark, and could also reveal new interactions transcending the
standard model. In addition, the radiative decays of the meson have become
a useful testing--ground for effective Lagrangians describing the low energy
interactions of pions, kaons and photons.Comment: Invited Talk at the Third Workshop on High Energy Particle Physics
(WHEPP 3) Madras, 1994, LaTex, 14 pages, 3 figures available upon reques
Further search for the decay in the momentum region P < 195 MeV/c
We report the results of a search for the decay
in the kinematic region with momentum MeV/c using the
data collected by the E787 experiment at BNL. No events were observed. When
combined with our previous search in this region, one candidate event with an
expected background of events results in a 90% C.L. upper limit
of on the branching ratio of .
We also report improved limits on the rates of and where are hypothetical, massless, long-lived
neutral particles.Comment: 5 pages, 3 figures, Accepted for publication in Phys. Rev.
Open data from the third observing run of LIGO, Virgo, KAGRA, and GEO
The global network of gravitational-wave observatories now includes five detectors, namely LIGO Hanford, LIGO Livingston, Virgo, KAGRA, and GEO 600. These detectors collected data during their third observing run, O3, composed of three phases: O3a starting in 2019 April and lasting six months, O3b starting in 2019 November and lasting five months, and O3GK starting in 2020 April and lasting two weeks. In this paper we describe these data and various other science products that can be freely accessed through the Gravitational Wave Open Science Center at https://gwosc.org. The main data set, consisting of the gravitational-wave strain time series that contains the astrophysical signals, is released together with supporting data useful for their analysis and documentation, tutorials, as well as analysis software packages
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Kaon physics at high intensity machines
The motivation for and present activity in rare kaon decay experiments are described. The reach of present and future accelerators for this physics is discussed. 56 refs., 10 figs
Search for heavy neutrinos in decay and status of lepton universality test in the PIENU experiment
International audienceIn the present work of the PIENU experiment, heavy neutrinos were sought in pion decays . No evidence for extra peak was found in the muon kinetic energy spectrum and 90% confidence level upper limits were set on the neutrino mixing matrix in the mass range of 15.7 to 33.8 MeV/c^2, improving an order of magnitude over previous experiments. Current status of lepton universality test is also reported