We have searched for the K{sup +} {yields} {pi}{sup +}{gamma}{gamma} decay in the kinematic region with {pi}{sup +} 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{sup +} {yields} {pi}{sup +}{gamma}{gamma}, P > 213 MeV/c) < 8.3 x 10{sup -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{sup +} {yields} {pi}{sup +}{gamma} branching ratio of 2.3 x 10{sup -9} at the 90% confidence level.
The photon detection inefficiency of electromagnetic calorimeters due to photonuclear reactions has been studied at photon energies below 1
GeV using a tagged-photon beam at the KEK-Tanashi 1.3-GeV ...electron synchrotron. Photonuclear reactions are identified by detecting low-energy neutrons with liquid scintillation counters surrounding the sample calorimeter. For a Cesium Iodide (CsI) calorimeter with a detection threshold of 10
MeV, the inefficiency due to photonuclear reactions is
10
-
4
at
E
γ
=
100
MeV
, and decreases to
2
×
10
-
7
at
E
γ
=
1
GeV
. For a lead-scintillator sampling calorimeter, the inefficiency is larger than the above values by a factor of 2–3, reflecting the sampling effect after photonuclear reactions. By decreasing the detection threshold down to 1
MeV, the inefficiencies are reduced by a factor of 10 for both types of calorimeters.
146 long-period red variable stars in the Large Magellanic Cloud (LMC) from the three-year Microlensing Observations in Astrophysics (MOA) project data base were analysed. A careful periodic analysis ...was performed on these stars and a catalogue of their magnitudes, colours, periods and amplitudes is presented. We convert our blue and red magnitudes to K-band values using 19 oxygen-rich stars. A group of red short-period stars separated from the Mira sequence has been found on a (log P,K) diagram. They are located at the short period side of the Mira sequence consistent with the work of Wood & Sebo. There are two interpretations for such stars; a difference in pulsation mode or a difference in chemical composition. We investigated the properties of these stars together with their colour, amplitude and periodicity. We conclude that they have small amplitudes and less regular variability. They are likely to be higher-mode pulsators. A large scatter has also been found on the long-period side of the (log P,K) diagram. This is possibly a systematic spread given that the blue band of our photometric system covers both standard B and V bands and affects carbon-rich stars.
PDF
