M. Fukushima

A phenomenological analysis on γp → π+n, πOp below 1.2 GeV

Abstract A phenomenological partial-wave analysis on γ p → π + n and π O p reactions has been performed in the energy range 0.25–1.2 GeV with available data, laying special emphasis on the polarization and asymmetry data. A good fit has been obtained.

Measurement of polarized target asymmetry on γp → π0p below 1 GeV

Abstract The polarized target asymmetry in the reaction γ p → π 0 p has been measured at c.m. angles of 30°, 80°, 105° and 120° for incident photon energies below 1 GeV. Two decay photons from π 0 were detected in coincidence at 30°, and at the other angles recoil protons and single photons from π 0 were detected. The results are compared with recent phenomenological analyses.

The measurement of polarized target asymmetry in γp → π0p between 0.4 and 1.0 GeV around 100°

Abstract The polarized target asymmetry for the process γ p → π 0 p was measured in the energies from 0.4 to 1.0 GeV at c.m. angles around 100° detecting both the gamma from π 0 and the recoil protons. A proton range telescope was used to detect the recoil protons. Observed asymmetries agree well with the existing data at overlapping data points. From the comparison between the present data and the available recoil proton polarization data, the contribution of the invariant amplitude A 3 can be examined. The experimental results are valuable in the determination of the photocouplings of nucleon resonances.

Polarized target asymmetry in π+ photoproduction between 0.3 and 1.0 GeV at 130°

Abstract The polarized target asymmetry for γ + p → π + + n was measured at c.m. angles around 130° for the energy range between 0.3 and 1.0 GeV. A magnetic spectrometer system was used to detect π + mesons from the polarized butanol target. The data show two prominent positive peaks at 0.4 and 0.8 GeV and a deep minimum at 0.6 GeV. These features are well reproduced by the phenomenological analysis made by us.

A 3He cooled cryostat with large cooling power for polarized targets

Abstract A 3He cooled cryostat with large refrigeration power has been developed for the polarized target experiment. It is able to cool down the target to a stable operation at 0.5 K within 1.5 h from room temperature. The cooling power of 200 mW at 0.5 K has been observed with the 2000 m3/h pump system. A much larger power will be obtained by the increase of the 3He pumping speed.

Backward polarization of π−p elastic scattering from 2.22 to 3.50 GeV/c

We have measured the polarization in π− backward elastic scattering at 2.22, 2.46, 2.71 and 3.50 GeV/c incident momenta, in the u-range−1.0 ≦u≦0.1 (GeV/c)2. The experiment used a polarized proton target and detected both pions and protons. We have found large discrepancies between the new data and the result of even the latest phase-shift analysis.

Polarized target asymmetry in π° photoproduction between 0.4 and 1.0 GeV around 100°

Abstract The polarized target asymmetry in the reaction γp→π°p has been measured at c.m. angles around 100° for photon energies between 0.4 and 1.0 GeV by detecting both the recoil proton and the π°. The result is compared with recent analyses.

Angular distributions of the polarized target asymmetry on γp →π+n at the energies of 0.5∠0.8 GeV

The preliminary results of the measurement of the polarized target asymmetry on γp→π+n at the C.M. angles between 40° and 160° in the energy range from 0.5 to 0.8 GeV are reported. The measurement is being performed detecting only π+ with a magnetic spectrometer system. The present data are well reproduced by the recent partial wave analyses.

High-precision measurement of π−p elastic scattering in a wide angular range at incident momenta between 2.06 and 3.48 GeV/c

Abstract We have measured the differential cross section for π − p elastic scattering at eight incident momenta, 2.06, 2.26, 2.45, 2.65, 2.86, 3.05, 3.26 and 3.48 GeV/ c , in a wide range of c.m. scattering angle between 15° and 160°. A pronounced dip-bump structure has been found at large angles. Details of the structure are quantitatively described as functions of the incident momentum.

A cryostat with a large cooling power for polarized target

We have constructed a new cryostat with a tube‐in‐tube type heat exchanger and a helical tube 3He condenser to satisfy the large cooling power and the quick normal operation required in the ES experiment. The cryostat is able to reach a stable operation within two hours from the precooling with the liquid nitrogen and has a cooling power of 200 mW at 0.5 K and 400 mW at 0.5 K and 400 mW at 0.6 K.The cryostat is now being used in the measurements of the polarized target asymmetries for the reaction γp↑↓→π+n and π0p with the incident gamma energies below 1 GeV at the 1.3 GeV electron synchrotron, Institute for Nuclear Study, Tokyo.