A. F. Prudkoglyad

Polarization in the reaction π−p → π0n at 40 GeV/c

Abstract The paper presents results on measuring the polarization in the reaction π − p→ π 0 n at 40 GeV/ c in the 4-momentum transfer range 0 t |⩽2 (GeV/ c ) 2 . The results based on the statistics of about 2.2 million recorded events made it possible to observe a noticeable value and complex structure in the polarization behaviour up to | t |⩽2 (GeV/ c ) 2 .

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.

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.

Polarization parameters in the reactions π−p↑→ηn and π−p↑→η′n at 40 GeV/c

The polarization parameter in the reactions π−p→ηn and π−p→η′n at 40 GeV/c with −t ranging from 0 to 2.6 (GeV/c)2 and 1.0 (GeV/c)2, respectively, was measured in experiments using a propanediol polarized target. Only gamma particles from the neutral meson decay were detected. The polarization parameter of the first reaction turns out to be negative in a widet interval (0.05<−t<1.6 (GeV/c)2) and probably changes its sign at larger values oft. The average value of the polarization parameter of the second reaction is equal to −17±8)% in the region 0.05<−t<0.5 (GeV/c)2.

Searches for single-spin asymmetry in the inclusive production of neutral pions in the central region at a proton beam energy of 70-GeV

Results are presented that were obtained by measuring single-spin asymmetry in the inclusive production of neutral pions in the reaction p+p ↑→ π0+X at xF≈0. A beam of 70-GeV protons was extracted directly from the vacuum chamber of the accelerator by means of a bent single crystal. For transverse momenta in the range 1.0<pT<3.0 GeV/c, the single-spin asymmetry independently measured by two detectors is zero within the errors. This result is in agreement with Fermilab data obtained at 200 GeV, but it is at odds with CERN data measured at 24 GeV.

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.

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.

A study of the RAMPEX electromagnetic calorimeter stability

The short- and long-term stabilities of the electromagnetic calorimeter for the RAMPEX experiment at the accelerator of the Institute for High Energy Physics has been investigated. Brief descriptions of the experimental setup, the calorimeter, and the monitoring system of the calorimeter are provided. A procedure for measuring the stability is described, and results of these measurements are presented. The necessity to study the stability has been dictated by the weakness of the effect in measuring the single-spin asymmetry of hadron production in the inclusive reaction π− = p↑(↓) → h + X at energies of 40 and 70 GeV/c.