[en] The positive, high-spin states of the ^155-165Er isotopes are studied within the framework of the interacting boson-fermion model. The single fermion is assumed to be in the I = (13/2) orbit only. It was found that the calculated positive high-spin state energy spectra of the odd Er isotopes agree quite well with the experimental data. Also, the observed order reversal of the adjacent spin doublet states of the energy spectra for ^159-163Er has been successfully reproduced. The B(E2) values for ^157-163Er are calculated and compared with the experimental data. (author)

[en] We check the scintillation light yield of all BGO crystals used for the Extreme Forward Calorimeter (EFC) at BELLE. The percentage spread of the distribution is only 6%. The nonuniformity of the light yields measured lengthwise for the forward EFC is close to 13% and is ∼0% for the backward EFC. The test crystals, two per ingot, from mass-production are subjected to the radiation hardness test. The results obtained at BINP and NTU are in good agreement. Some EFC crystals, selected randomly, show the light yields drop about 25-50% after receiving 1 krad dose and remain stable afterwards. There is little sensitivity to the rate that the 1 krad dose is received, since the recovery process is very slow, in the order of days to weeks

[en] In the BELLE experiment at KEKB, a threshold Cherenkov counter system based on silica aerogels will be used to provide π/K separation in the momentum region from 0.8 to 3.5 GeV/c. The detector design, recent progress in R and D and results of beam tests are reviewed. (orig.)

[en] We measured the radiation damage on silica aerogel Cherenkov radiators originally developed for the B-factory experiment at KEK. The refractive index of the aerogel samples ranged from 1.012 to 1.028. The samples were irradiated up to 9.8 Mrad of equivalent dose. Measurements of transmittance and refractive index were carried out and these samples were found to be radiation hard. Deteriorations in transparency and changes of refractive index were observed to be less than 1.3% and 0.001 at 90% confidence level, respectively. Prospects of using aerogels under high-radiation environment are discussed. (orig.)

[en] Nuclear transparencies measured in exclusive incoherent ρ⁰ meson production from hydrogen, deuterium, carbon, calcium, and lead in muon-nucleus scattering are reported. The data were obtained with the E665 spectrometer using the Fermilab Tevatron muon beam with a mean beam energy of 470 GeV. Increases in the nuclear transparencies are observed as the virtuality of the photon increases, in qualitative agreement with the expectations of color transparency

[en] We detected 1--10 MeV neutrons at laboratory angles from 80 degree to 140 degree in coincidence with 470 GeV muons deep inelastically scattered from H, D, C, Ca, and Pb targets. The neutron energy spectrum for Pb can be fitted with two components with temperature parameters of 0.7 and 5.0 MeV. The average neutron multiplicity for 40<ν<400 GeV is about 5 for Pb, and less than 2 for Ca and C. These data are consistent with a process in which the emitted hadrons do not interact with the rest of the nucleus within distances smaller than the radius of Ca, but do interact within distances on the order of the radius of Pb in the measured kinematic range. For all targets the lack of high nuclear excitation is surprising

[en] The ratio of the deuteron to proton structure functions is measured at very small Bjorken x (down to 10^--6) and for Q²>0.001 GeV² from scattering of 470 GeV muons on liquid hydrogen and deuterium targets. The ratio Fⁿ₂/F^p₂ extracted from these measurements is found to be constant, at a value of 0.935±0.008±0.034, for x<0.01. This result suggests the presence of nuclear shadowing effects in the deuteron. The dependence of the ratio on Q² is also examined; no significant variation is found

[en] It is well known that the proton is a spin-1/2 particle, but how the constituents (quarks and gluons) assemble to this quantized spin is still a mystery. There is a worldwide effort to map out the individual contributions to the proton spin. It is established that the quark spins contribute around 30%, while the gluon intrinsic angular momentum is still under active investigation at the Relativistic Heavy Ion Collider. Fully resolving the proton spin puzzle requires information on the orbital angular momentum (OAM) of both quarks and gluons. Recent studies have shown that the so-called transverse momentum-dependent parton distribution functions (TMDs) can inform us about the OAM of the partons. One of the most important TMDs, and the main focus of this LOI, is the so-called Sivers function. To summarize, we propose to make the first measurement of the Sivers function of sea quarks, which is expected to be non-zero if the sea quarks contribute orbital angular momentum to the proton spin, as expected from the pion cloud model, which also partially explains the E866 results. Thus, we will be able to deduce whether or not sea quark orbital motion contributes significantly to the proton spin. Specifically, we will determine the contribution from the anti-up quarks, with Bjorken-x in the range of ~ 0.1 to 0.5. Drell-Yan production off a polarized proton target has never been measured, and is complementary to the recently approved (stage-1) experiment E1027 at Fermilab, which will measure the Sivers function of the valence quarks using a polarized proton beam on an unpolarized proton target. If the measured sea quark Sivers function is non-zero, we will also determine its sign.