V. V. Mochalov

Observation of significant spin effects in hard collisions at 40 GeV/c

Abstract A single-spin asymmetry in the inclusive π 0 production at small x F was measured. In the experiment 40 GeV/c π − mesons were incident on transversely polarized protons and deutrons. An asymmetry of (40–50)% has been revealed in the hard scattering region.

Precision measurement of energy and position resolutions of the BTeV electromagnetic calorimeter prototype

Abstract The energy dependence of the energy and position resolutions of the electromagnetic calorimeter prototype made of lead tungstate crystals produced in Bogoroditsk (Russia) and Shanghai (China) is presented. These measurements were carried out at the Protvino accelerator using a 1– 45 GeV electron beam. The crystals were coupled to photomultiplier tubes. The dependence of energy and position resolutions on different factors as well as the measured electromagnetic shower lateral profile are presented.

Study of radiation damage in lead tungstate crystals using intense high-energy beams

We report on the effects of radiation on the light output of lead tungstate crystals. The crystals were irradiated by pure, intense high-energy electron and hadron beams as well as by a mixture of hadrons, neutrons and gammas. The crystals were manufactured in Bogoroditsk, Apatity (both Russia), and Shanghai (China). These studies were carried out at the 70-GeV proton accelerator in Protvino.

Design and performance of LED calibration system prototype for the lead tungstate crystal calorimeter

A highly stable monitoring system based on blue and red light emitting diodes coupled to a distribution network comprised of optical fibers has been developed for an electromagnetic calorimeter that uses lead tungstate crystals readout with photomultiplier tubes. We report of the system prototype design and on the results of laboratory tests. Stability better than 0.1% (r.m.s.) has been achieved during one week of prototype operation.

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.

Measurement of the single-spin asymmetry in the reaction π−d↑ → π0X in the beam-fragmentation region at 40 GeV and pT of up to 2 GeV/c

The single-spin asymmetry AN in the reaction π− + d↑ → π0 + X in the beam-fragmentation region at the energy of 40 GeV was investigated by using the PROZA setup installed at the U-70 accelerator of the Institute for High Energy Physics (IHEP, Protvino). It was measured to be AN = (13.6 ± 2.6(stat.) ± 2.0(syst.))% in the intervals 0.7 < xF < 1.0 and 1.0 < pT < 1.8 GeV/c. The results agree with the asymmetry of π0 mesons in the charge-exchange reaction π− + p↑ → π0 + n at the same values of the transverse momentum and beam energy. The asymmetry in the reaction K− + d↑ → π0 + X was simultaneously measured and found to be AN = (11 ± 14)% for pT > 1.2 GeV/c.

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.

Reconstructing the Coordinates of Inclined Showers in Lead Glass Electromagnetic Calorimeters

A method for reconstructing the coordinates of inclined showers in lead glass electromagnetic calorimeters is described. Such showers are generated by photons with energies of 0.5–4.0 GeV that are incident on the detector at angles of as great as 30°. An analytical expression for the description of the actual photon coordinate in the calorimeter versus the coordinates of the shower’s center of gravity is proposed. Using this expression, it is possible to reconstruct the coordinates of inclined electromagnetic showers over wide ranges of angles and energies. The dependences of the spatial resolution on the photon energy and angle are determined. The longitudinal fluctuations of the shower length and their effect on the spatial resolution of the calorimeter are discussed. Results of simulation of the shower in a lead glass are used to determine the parameters of actual showers. The applicability of this method is tested by processing experimental data.

Single-spin asymmetry of inclusive neutral-pion production in pp∩ interactions at 70 GeV in the region -0.4 < xf < -0.1

For the kinematical region specified by the inequalities −0.4 < xF < −0.1 and 0.9 < pT < 2.5 GeV/c, the results are presented that were obtained by experimentally determining the single-spin asymmetry of inclusive neutral-pion production in the reaction p + p↑ → π0 + X at 70 GeV. According to these results, the asymmetry is close to zero in the region −0.2 < xF < −0.1 and grows in magnitude with decreasing xF, amounting to (−10.6 ± 3.2)% for −0.4

Single-spin asymmetry of inclusive π0-meson production in 40-GeV pion interactions with a polarized target in the target-fragmentation region

Data on the single-spin asymmetry (AN) of inclusive π0 production in 40-GeV pion interactions with a polarized target, π−+↑→π0+X, are presented for the target-fragmentation region. The result is AN=(−13.8±3.8)% for −0.8<xF<−0.4 and 1<pT<2 GeV/c and is compatible with zero for −0.4<xF<−0.1 and 0.5<pT<1.5 GeV/c. At a π0 momentum of about 1.7 GeV/c in the c.m. frame, the asymmetry becomes nonzero both in the central and in the target-fragmentation region. The behavior of the asymmetry is similar to that observed in the beam-fragmentation region of the E-704 (FNAL, 200 GeV) and STAR (BNL, 20 TeV) experiments, which employed a polarized proton beam.