A. V. Ryazantsev

Preparation of new polarization experiment SPASCHARM at IHEP

A new experiment SPASCHARM devoted to a systematic study of polarization phenomena in hadron-hadron interactions in the energy range 10-70 GeV is under preparation at IHEP (Protvino). The physical observables will be single-spin asymmetries, hyperon polarizations and spin-density matrix elements. A universal setup will detect and identify various neutral and charge particles in the full azimuthal angle and a wide polar angle range. A polarized target is used to measure the SSA. The SPASCHARM sub-detectors are being designed and constructed now. The possibility of obtaining a polarized proton beam for the SPASCHARM experiment from Lambda decays is under study.

Effect of γ Irradiation on the Scintillation and Optical Properties of Lead Tungstate Crystals

The radiation hardness of a test batch of lead tungstate crystals grown by a new technology at the Bogoroditsk Technochemical Plant for the PANDA experiment has been measured. The optical properties of the crystals have been investigated at temperatures ranging from +20 to −20°C under irradiation with a 137Cs radionuclide source. The light yield in the crystal is seen to considerably increase with a decrease in its temperature. In addition, the loss of the crystal transparency under irradiation at low temperatures is higher than under irradiation at room temperature. As a result, at a fixed dose rate, the signal from the crystal at a negative temperature may be considerably greater than the signal at room temperature even if the accumulated dose is high.

Measuring the momentum dispersion of a proton beam extracted from the U-70 accelerator by channeling

The momentum dispersion of the proton beam extracted from the vacuum chamber of the U-70 accelerator by channeling was measured for the first time. At an 80-mrad bending angle of the Si single crystal, the following beam parameters were attained: an intensity of 107 protons/s for 1012 protons/s hitting the crystal, momentum dispersion of the beam Δp/p = 0.13%, and a background particle admixture of 0.03% or less.

Analyzing Power in the Reaction p + p └ → π 0 + X in the polarized-target fragmentation region at an energy of 50 GeV

The results obtained by measuring, at the U-70 accelerator in Protvino, the single-spin asymmetry AN in the reaction p + p└ → π0 + X at a beam energy of 50 GeV in the Feynman variable range of −0.6 < xF < −0.1 are presented. The asymmetry AN is close to zero at small |xF| and grows in magnitude with |xF|, reaching 6.4% in the region of |xF| > 0.25. The results of these measurements agree with data of the E704 experiment on the asymmetry of π0 mesons at the Fermi National Accelerator Laboratory in the region of polarized-beam fragmentation and with the results of measurements in the region of polarized-target fragmentation that were performed in Protvino by using a 40-GeV π−-meson beam and a 70-GeV proton beam.

Studying the radiation hardness of lead tungstate crystals under long-term γ irradiation

Changes in the transparency of lead tungstate crystals under continuous ∼1200-h irradiation with γ rays of a radionuclide 60Co source were investigated. The crystal temperature was maintained at a level of −15°C at a dose rate of 0.1 Gy/h. The crystal transparency recovery process was investigated after the irradiation at temperatures varying from −15 to +38°C. The study was performed while preparing for the PANDA experiment in the FAIR project in Germany.

Spin Physics Program At IHEP-Protvino

A new single‐spin asymmetry AN measurement has been carried out at IHEP at 50 GeV. AN was found to be −(6.2±1.5)% in the polarized target fragmentation region at −0.6<xF<−0.25. The result proves that asymmetry does not depend on beam energy. A review of polarization results from Protvino as well as a proposal of the new experiment SPASCHARM are also presented.

Expected accuracy in a measurement of the CKM angle alpha using a Dalitz plot analysis of B0 ---> rho pi decays in the BTeV project

A precise measurement of the angle α in the CKM triangle is very important for a complete test of the Standard Model. A theoretically clean method to extract α is provided by B0 → ρπ decays. Monte Carlo simulations to obtain the BTeV reconstruction efficiency and to estimate the signal-to-background ratio for these decays were performed. Finally the time-dependent Dalitz plot analysis, using the isospin amplitude formalism for tree and penguin contributions, was carried out. It was shown that, in one year of data taking, BTeV could achieve an accuracy on α better than 5°.

Expected accuracy in a measurement of the CKM angle {alpha} using a Dalitz plot analysis of B{sup 0} {sup {yields}} {rho}{pi} decays in the BTeV project

A precise measurement of the angle α in the CKM triangle is very important for a complete test of the Standard Model. A theoretically clean method to extract α is provided by B0 → ρπ decays. Monte Carlo simulations to obtain the BTeV reconstruction efficiency and to estimate the signal-to-background ratio for these decays were performed. Finally the time-dependent Dalitz plot analysis, using the isospin amplitude formalism for tree and penguin contributions, was carried out. It was shown that, in one year of data taking, BTeV could achieve an accuracy on α better than 5°.

Expected Accuracy in a Measurement of the CKM Angle

A precise measurement of the angle α in the CKM triangle is very important for a complete test of the Standard Model. A theoretically clean method to extract α is provided by B0 → ρπ decays. Monte Carlo simulations to obtain the BTeV reconstruction efficiency and to estimate the signal-to-background ratio for these decays were performed. Finally the time-dependent Dalitz plot analysis, using the isospin amplitude formalism for tree and penguin contributions, was carried out. It was shown that, in one year of data taking, BTeV could achieve an accuracy on α better than 5°.