A. N. Fedorov

Frozen spin solid targets developed at the Laboratory of Nuclear Problems (JINR, Dubna)☆

Experience with polarized targets [1,2] and achieving of very low temperatures in 1966 at the Laboratory of Nuclear Problems [3] and by another group [4] gave rise to the idea of using a radically new technique based on dissolving 3He in 4He to create a frozen spin polarized target. The short history of the development of such proton and deuteron targets at the LNP is given. The complex Cr(V) compounds in diols are used as target operating material. A characteristic feature of these targets is a long relaxation time (∼ 1000h) in magnetic fields of about 0.5 T. Lately, the Saclay-Argonne frozen spin proton polarized target used initially in E704 experiment at FERMILAB has been upgraded with adding the missing parts and the first physics experiment has been carried out.

The new frozen spin target at MAMI

The new frozen spin polarized target for experiments at the polarized beam of the real photon facility A2 of the MAMI accelerator is described. The A2-collaboration at the Mainz Microtron MAMI is measuring photon absorption cross section using circularly and linearly polarized photons up to the energy of 1.5 GeV. The photons are produced in the’ Bremsstrahlungs’ process. In the years 2005/2006 the Crystal Ball detector with its unique capability to cope with multi photon final states was set up in Mainz. Since 2010 the experimental apparatus has been completed by a polarized target. The horizontal dilution refrigerator of the Frozen-Spin Target has been constructed and is operated in close cooperation with the Joint Institute for Nuclear Research in Dubna, Russia. The system offers the opportunity to provide longitudinally and transversely polarized protons and deuteron. In this paper the operation experience of this new Frozen-Spin Target and first results from the runs in 2010 and 2011 are presented.

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.

Measurements of energy behaviour of spin-dependentnp—observables over 1.2–3.7 GeV energy region Dubna “Delta-Sigma” Experiment

New accurate data on the neutron-proton spin-dependent total cross section difference ΔσL(np) at the neutron beam kinetic energies 1.4, 1.7, 1.9 and 2.0 GeV are presented. A number of physical and methodical results on investigation of an elasticnp→pn charge exchange process over a few GeV region are also presented. Measurements were carried out at the Synchrophasotron and Nuclotron of the Veksler and Baldin Laboratory of High Energies of the Joint Institute for Nuclear Research.

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.

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.

Deuteron frozen-spin- polarized target for nd experiments at the VdG accelerator of Charles University

Abstract A frozen-spin- polarized deuteron target cooled by the 3 He/ 4 He dilution refrigerator is described. Fully deuterated 1,2-propanediol was used as a target material. Deuteron vector polarization about 40% was obtained for the target in the shape of a cylinder of 2-cm diameter and 6-cm length. The target is intended for a study of 3N interactions at the polarized neutron beam generated by the Van de Graaff accelerator at the Charles University in Prague.

AN AT SMALL NEGATIVE VALUES OF xF IN THE REACTION p + p↑ → π0 + X AT 70 GeV AND UNIVERSAL THRESHOLD IN INCLUSIVE PION PRODUCTION

The talk continues the series of Single Spin Asymmetry (SSA)