Search

In the last decade, heavy-ion based experiments (HypHI, STAR and ALICEi ) announced surprisingly short lifetime for 3 ΛH mesonic weak decay (MWD), which is difficult to interpret given the fact that 3 ΛH is a very loosely bound system. It will be very interesting to study this issue with a different experimental approach. We propose a direct measurement for 3 ΛH hypernucleus MWD lifetime with ∼10% precision as J-PARC E73 experiment; 4 ΛH hypernucleus lifetime will also be measured as a feasibility test for our experimental approach. In this proceeding, we will introduce the experimental method and the current status of E73 experiment.

Background Mitral regurgitation (MR) is sometimes observed in cardiac sarcoidosis (CS), and might be related to worsening heart failure. However, mechanism and clinical significance of MR associated with CS remains undetermined. Methods We retrospectively analyzed consecutive 51 CS patients, and identified 16 patients with moderate to severe MR evaluated by quantitative echocardiography. According to the assessment of coaptation point and tenting height, main mechanisms of the 16 patients with MR were classified into prolapse (P) in 5, and tethering in 11 (T). Prednisolone was started from 30 mg/day, gradually tapered over a period of 6 months to a maintenance dose of 5 to 10 mg/day and continued a lifetime. Results At the first visit, patients with MR showed higher incidence of NYHA class IV heart failure as compared to those without MR (56 vs. 9%, p Conclusions MR associated with CS has variety of mechanisms including prolapse, tethering and inflammation of the LV papillary muscle, and may be related to ventricular remodeling and poor clinical outcome.

The present status of hypernuclear gamma-ray spectroscopy with Hyperball is summarized. We observed two gamma transitions of 16-Lambda-O(1- -> 1-,0-) and obtained the strength of the Lambda-N tensor force. In 10B(K-,pi- gamma) data, we did not observe the spin-flip M1 transition of 10-Lambda-B(2- -> 1-), but gamma rays from hyperfragments such as 7-Lambda-Li(7/2+ -> 5/2+) and 9-Lambda-Be(3/2+ ->1/2+) were observed. In 11B(pi+,K+ gamma) data, we observed six gamma transitions of 11_Lambda-B. We also attempted an inclusive gamma-ray measurement with stopped K- beam.

A new 3-axis magnetic field measurement system based on the Hall elements has been constructed at KEK. The new system was designed for the larger magnets of higher energy accelerator facilities such as J-PARC. We employed a 7 m long 2 m wide iron base, and the magnet and the field mapping machine were set on the same base. We set pivot fittings at intervals of 250 mm through the longer side of the base. Therefore the alignment accuracy between the mapping machine and the magnet is promised within 0.1 mm in total by simply putting the magnet on the base. In addition, by teaching the mapping-machine coordinates of the two separate points on the magnet axis to the mapping machine, the field measurement points on the magnet coordinates can automatically be calculated and positioned in software way. We used three single-axis Hall elements mass-produced by industry. 3 Hall elements could be mounted on a rectangular PEEK block. The distance between hall elements is approximately 3.3 mm. The accuracy of 3 directions of Hall elements is within 0.5 degrees. The temperature of Hall elements was controlled within 60 /spl plusmn/0.1 degrees centigrade. Owing to the light weight of the Hall sensor unit and the strong carbon fiber rod with one side support, the bend of the rod was less than 10 mm for 2200 mm rod length. Thus we have successfully measured the field of the big Q-magnet, whose bore diameter and length are 200 mm and 3 m.

We will measure the x‐rays from kaonic 3He and 4He 3d→2p transition by using silicon drift detectors. Our precision goal is set to 1 eV to provide crucial information on the kaon‐nucleus strong interaction in the low energy limit. The experiment is to be performed as one of the first experiment in the J‐PARC hadron facility (J‐PARC E17). An overview and the present status of the experiment are presented.

The KEK to Kamioka long-baseline neutrino experiment (K2K) has begun its investigation of neutrino oscillations suggested by atmospheric neutrino observations. Twenty-eight neutrino events have been detected in coincidence with the expected arrival time of the beam in the 22.5 kt fiducial volume of Super--Kamiokande, the far detector at 250 km distance. The expectation is 37.8+3.5-3.8, derived using measurements of neutrino interactions in a near detector and extrapolation using a beam simulation validated by a measurement of pion kinematics after production and focusing. The background is of order 10^-3 events., Comment: 6 pages, 3 embedded figures, LaTeX with RevTeX style, submitted to PRL. This version is As Submitted

A hybrid emulsion experiment was carried out to study double-strangeness nuclei produced via Ξ− hyperon capture at rest with the expectation of ten times larger statistics than previous experiments. We have analyzed 5% of the total emulsion and found one “twin-hypernuclei” event involving the emission of two single-Λ hypernuclei and a nuclear fragment from a Ξ− hyperon stopping point. The event is interpreted as the decay of a Ξ − + 14 N atomic system to 5 Λ He + 5 Λ He + 4 He + neutron . The species of the Ξ−-atom and the fragmentation products are uniquely identified for the first time for twin-hypernuclei events. Combined with the results from a past hybrid-emulsion experiment, one double-Λ hypernucleus and three twin-hypernuclei events have been found from Ξ− captures on light emulsion nuclei. The ratio of the detected rate of double-Λ hypernuclei to that of twin-hypernuclei is compared with theoretical estimates.

A high-intensity, high-resolution pion beam line has been proposed for the Japan Hadron Facility. An intensity of 109 and a momentum resolution of 10 -4 will be available. High-resolution, high-statistics, and high-sensitivity spectroscopic studies of hypernuclei will be possible.

The Θ(+) pentaquark baryon was searched for via the π(-)p→K(-)X reaction with a missing mass resolution of 1.4 MeV/c(2) (FWHM) at the Japan Proton Accelerator Research Complex (J-PARC). π(-) meson beams were incident on the liquid hydrogen target with a beam momentum of 1.92 GeV/c. No peak structure corresponding to the Θ(+) mass was observed. The upper limit of the production cross section averaged over the scattering angle of 2° to 15° in the laboratory frame is obtained to be 0.26 μb/sr in the mass region of 1.51-1.55 GeV/c(2). The upper limit of the Θ(+) decay width is obtained to be 0.72 and 3.1 MeV for J(Θ)(P)=1/2(+) and J(Θ)(P)=1/2(-), respectively, using the effective Lagrangian approach.

The Theta+ was searched for via the K+p -> pi+X reaction using the 1.2 GeV/c K+ beam at the K6 beam line of the KEK-PS 12 GeV Proton Synchrotron. In the missing mass spectrum of the K+p -> pi+X reaction, no clear peak structure was observed. Therefore a 90 % C.L. upper limit of 3.5 ub/sr was derived for the differential cross section averaged over 2degree to 22degree in the laboratory frame of the K+p -> pi+Theta+ reaction. This upper limit is much smaller than the theoretical calculation for the t-channel process where a K0* is exchanged. From the present result, either the t-channel process is excluded or the coupling constant of g_{K*N\Theta} is quite small.

A technique using VHS high-fidelity equipment to record two different distinguishable signals on the same track is described. The first signal has to be recorded by a longer-gap-length head in order to obtain higher residual output after overwrite erasing by the second signal for coating-type materials. When the wavelength of the first signal is relatively short, the shorter the second signal wavelength, the greater is the erasure of the first signal. The azimuth angle should be chosen in such a way as to minimize the crosstalk between the first and second recorded signal. This phenomenon can be used for rotary erasing and overwrite erasing. >