N. Takabayashi

First results of the large COMPASS 6LiD polarized target

The COMPASS (NA58) experiment at CERN operates with a large solid polarized target (PT) to study the spin structure of the nucleon. The COMPASS PT system started its operation with the target material 6 LiD in 2001. Deuteron polarizations of þ54:2% and � 47:1% were achieved in a 3 He= 4 He dilution refrigerator at a magnetic field of 2: 5T : The equal spin temperature (EST) concept was found to hold among the deuteron, the 6 Li and the 7 Li nuclei during the dynamic nuclear polarization (DNP) process. The agreement with the EST concept allows the permanent monitoring of only one nuclear species by the nuclear magnetic resonance (NMR) method. r 2003 Elsevier Science B.V. All rights reserved.

Measurement of the tensor analyzing power Ayy in inclusive breakup of 9 GeV/c deuterons on carbon at large transverse momenta of protons

Abstract The tensor analyzing power A yy in inclusive breakup of 9 GeV/c deuterons on carbon has been measured at the detected proton angle of 85 mr. The analyzing power remains positive at the highest measured momentum of the proton in definite contradiction with the predictions of the existing models. The vector analyzing power A y has been obtained simultaneously with A yy .

Fragmentation of tensor polarized deuterons into cumulative pions

Abstract The tensor analyzing power T20 of the reaction d +A→π − (0°)+X has been measured in the fragmentation of 9 GeV tensor polarized deuterons into pions with momenta from 3.5 to 5.3 GeV/c on hydrogen, beryllium and carbon targets. This kinematic range corresponds to the region of cumulative hadron production with the cumulative variable xc from 1.08 to 1.76. The values of T20 have been found to be small and consistent with positive values. This contradicts the predictions based on a direct mechanism assuming NN collision between a high momentum nucleon in the deuteron and a target nucleon (NN→NNπ).

Time resolution of a scintillating fiber detector

Abstract The performance of scintillating fiber detectors with 2xa0m long light guides was investigated for COMPASS experiment, using a 450xa0MeV/ c electron beam.Prototypes consisting of 0.5xa0mm diameter fibers (Kuraray SCSF-38 single-cladding) with the position-sensitive photomultipliers H6568 (Hamamatsu) were constructed for the test. The time resolution of σ ∼430 ps was obtained with about 10 photoelectrons for the prototype of 10-layers structure.

TIME RESOLUTION OF MULTI-CLADDING SCINTILLATING FIBER HODOSCOPE

Abstract A prototype of a scintillating fiber hodoscope was constructed with multi-cladding scintillating fibers and a multi anode photomultiplier (H6568, HAMAMTSU). The hodoscope has a seven structure of a scintillating fiber with 0.5xa0mm in diameter and stacked in closest packing in order to improve its efficiency and time resolution. The hodoscope has been tested using a proton beam. The time resolution of about 700xa0ps in FWHM has been obtained.

A scintillating fiber tracker with high time resolution for high-rate experiments

A fast and precise scintillating fiber (SciFi) tracker, using 0.5-mm-diameter fibers (Kuraray SCSF-78MJ) and position-sensitive photomultiplier tubes (Hamamatsu H6568), has been developed for the COMPASS (NA58) experiment at CERN. Tests of a 16-channel prototype showed an excellent stability in time resolution, in spatial resolution, as well as in detection efficiency under different beam flux of up to 1.4 /spl times/ 10/sup 8/ muons/spill. Four SciFi tracker stations have been constructed and all of them are presently under operation in the experiment with high performances as expected from the prototype.

First results on the tensor analyzing power Ayy in deuteron inclusive breakup at large transverse momenta of protons

The tensor analyzing power A yy in inclusive breakup of 9 GeV/c deuterons on carbon has been measured at 85 mrad of the detected proton angle using polarized beam of the Synchrophasotron of the Laboratory for High Energies of JINR. The analyzing power A yy remains positive at the highest measured momentum of the proton in definite contradiction with the predictions based on the standard nucleon-nucleon potentials.

Polarized deuteron target system for low energy D⃗(d⃗,p)T measurement

Our group is constructing a polarized deuteron target system for a measurement of D(d,p)T reaction at low energies. If we assume that the incident energy of deuteron beam is 20 MeV, and its intensity is 1 nA, required specifications to the target system are the polarization is larger than 40%, the target thickness is ∼1 mg/cm2, a cooling power of refrigerator is several mW at 200 mK. At present, the lowest temperature of 200 mK and the cooling power of 2.6 mW at 500 mK was achieved. On the other hand, the development of target material has been made. The polarization of 17% was obtained to a electron irradiated—CD2 foil with a doze of 1×1016u200ae−/cm2.

Measurement of the Tensor Analyzing Power T20 in the Fragmentation of 9 GeV Tensor Polarized Deuterons into Cumulative Pions

Tensor analyzing power T 20 of the reaction d ↑ A → π–(0°)X was measured in the fragmentation of 9 GeV deuterons into pions with momenta from 3.5 to 5.3 GeV/c on hydrogen, beryllium and carbon targets. This momentum range corresponds to the region of cumulative production with the cumulative variable x c from 1.08 to 1.76. The values of T 20 were found to be small and consistent with positive values in contradiction with the predictions based on a direct mechanism assuming N N collision between a high momentum nucleon in the deuteron and a target nucleon (N N → N N π).