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The completion of single-spin asymmetry measurements at the PROZA setup

The completion of single-spin asymmetry measurements at the PROZA setup. V. Mochalov (IHEP, Protvino) On behalf of the PROZA-SPASCHARM collaboration. Introduction remark. This talk itself is sad in some sense: This is probably the last report devoted to the current PROZA activity

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The completion of single-spin asymmetry measurements at the PROZA setup

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  1. The completion of single-spin asymmetry measurements at the PROZA setup V. Mochalov (IHEP, Protvino) On behalf of the PROZA-SPASCHARM collaboration

  2. Introduction remark • This talk itself is sad in some sense: • This is probably the last report devoted to the current PROZA activity • Polarization program with old JINR target is completed after 30 years of investigations • Nevertheless new spin program at IHEP is under preparation (see next talk by S.Nurushev) V. Mochalov, PROZA-M experiment

  3. Outline • Recent Single-spin asymmetry results from PROZA • AN in the beam (non-polarized) fragmentation region • AN in the target (polarized) fragmentation region • Review of previous results from PROZA • Polarization and single-spin asymmetry in exclusive (charge-exchange) reactions • Single-spin asymmetry in inclusive reactions in the central region • PROZA – answers and questions (instead of conclusion) V. Mochalov, PROZA-M experiment

  4. Asymmetry in the beam fragmentation region • Negative beam (π-/K/p-bar:97.9/1.8/0.3%) • Beam particle identification • Propane-diol (C3H8O2) target with 90% average polarization (diameter 20 mm, length 200 mm ) • Neutral particle trigger • EMC (800 lead glass channels) with trigger on transverse momenta pT V. Mochalov, PROZA-M experiment

  5. Negative particle beam profile on the target • x(target) = y(target)=3.5 mm (98% inside the target) V. Mochalov, PROZA-M experiment

  6. AN in the π-d↑→π0X reaction • AN in theK-d↑→π0X reaction is equaled zero (-0.46.1)% at 0.6<pT (GeV/c)<1.2 and • AN=(116.1)% at pT>1.2 (GeV/c) V. Mochalov, PROZA-M experiment

  7. pT dependence of AN in the beam fragmentation region • Asymmetry is zero at small pT (red points – previous results, published in 1989 ) and • Is significant at large pT: AN=(13.62.6(stat)2.0(syst))% at pT>1 (GeV/c)and 0.7 (0.7<xF<1.0) V. Mochalov, PROZA-M experiment

  8. First asymmetry measurements at the polarized target fragmentation region π-p↑→π0X, Phys.At.Nucl, 67 (2004) 1495 Asymmetry in the inclusive π0-production in the polarized target fragmentation region was measured in 1996-2002 in the reactions π-p↑→π0X pp↑→π0X AN increases with |xF| increased. The result is in agreement with E704 and STAR data. pp↑→π0X, Phys.At.Nucl, 68 (2005)1790 V. Mochalov, PROZA-M experiment

  9. Final PROZA-2 measurements • Asymmetry in pp↑→π0X in the polarized target fragmentation region at 50 GeV. • Two sets of data (2005 and 2007) are being used for analysis. • EMC consists of 720 lead glass blocks • proton beam up to 7∙106 p/cycle V. Mochalov, PROZA-M experiment

  10. Beam properties and stability • Proton beam was extracted from U70 vacuum chamber using bent crystal (80 mrad) • x=2.7 mm, y=3.7 mm • P/P<0.013% • Beam position stability <x><0.1 mm V. Mochalov, PROZA-M experiment

  11. γ and π0 reconstruction in EMC • EMC-720 was adjusted to measure low energy gammas (2.2 MeV/ADC channel) • Nevertheless reconstructed energy depends on real γ energy • EMC is 2.3 m downstream target: • Reconstructed energy depends on angle of incident γ • Special algorithm was developed V. Mochalov, PROZA-M experiment

  12. π0 mass • (π0)=17 MeV (left) • <m(π0)> after correction (circles) does not depend on angle and energy (right) V. Mochalov, PROZA-M experiment

  13. π0 kinematics V. Mochalov, PROZA-M experiment

  14. AN in the reaction pp↑→π0X (close to final) at 50 GeV (2005+2007 data) Preliminary At -0.6<xF<-0.25 single spin asymmetry AN= -(6.21.5)% V. Mochalov, PROZA-M experiment

  15. Comparison of the asymmetry with other experiments • AN in the inclusive π0 production at polarized particle fragmentation region at 0.25<xF<0.6 at 50 GeV (6.21.5)%is in a very good agreement with other experiments: • AN In the reaction π-p↑→π0X at 40 GeV (6.92.8) • With E704 data at 200 GeV (6.30.7) AN in inclusive π0 production does NOT depend on beam energy. V. Mochalov, PROZA-M experiment

  16. Polarization in the reaction π-p↑→π0n • Polarization P(t) in the range of 0<|t|<0.35(GeV/c)2equals 5.00.7%. • There is a minimum at "crossover" effect region t=-0.25 (GeV/c)2 • Polarizationchanges its sign in the dip region in the differential cross-section. • There are oscillations in polarization behavior. V.D. Apokin et al., Sov. J. Nucl. Phys. 45:840, 1987, [Yad.Fiz.45:1355-1357,1987] V.D. Apokin et al.Z.Phys.C15:293,1982 V. Mochalov, PROZA-M experiment

  17. Polarization in the reactions π-p↑→n and π-p↑→’(958)n • An essential polarization in wide interval of 0.05<-t<1.6 (GeV/c)2 in π-p↑→n at 40 GeV. • In the region 0.05<-t<0.4 (GeV/c)2 polarization is small (-5% ); • with -t increasing up to ~1(GeV/c)2, the polarization absolute value increases. AN=(-4411)% at the |t| range of 0.8-1.6 (GeV/c)2 • polarization changes a sign near -t=1.8 (GeV2/c)2 . • The averaged value of the polarization in the reaction π-p↑→’(958)n in the region of 0.05< -t <0.5 (GeV2/c)2 is (-17 8)%. V.D. Apokin et al., Z.Phys.C35:173,1987. V. Mochalov, PROZA-M experiment

  18. Asymmetry in the reactions π-p↑→(783)n and π-p↑→f2(1270)n •  was registered via γ decay (branching only 8.9%). • Asymmetry is large in both reactions • Indication on minimum at –t=0.2 (GeV/c)2 for both reactions I.A. Avvakumov et al.Yad.Fiz.42:1146,1985 V.D. Apokin et al.Yad.Fiz.47:727-730,1988] V. Mochalov, PROZA-M experiment

  19. Asymmetry in inclusive π0 production at xF=0 π-p↑→π0X,Phys.Lett.B243,461 (1990) • Asymmetry in the reaction π-p(d)↑→π0X is big and does not depend on target flavor. The result can not be explained by Sivers and Collins functions. Asymmetry in π-p(d)↑→ηX is even bigger • Asymmetry in the reaction pp↑→π0X is zero at the whole pT interval. The result confirms E-704 measurements at 200 GeV. pp↑→π0X, Phys.At.Nucl, 67 (2004) 1487 V. Mochalov, PROZA-M experiment

  20. Essential polarization (asymmetry) was found in all reactions There is indication on asymmetry oscillations There is a minimum at "crossover" effect region inπ-p↑→π0n Polarization changes sign in the dip region in the disserential cros-section Simple Regge model can not describe polarization modification required: U matrix with pomeron spin-flip Odderon pole is required in addition to ρ-pole Prediction: P(π0)+2P(η)=P(η) a0(980) – see Achasov. Does the asymmetry magnitude increase with meson mass? Is it real effect for all particles? Better accuracy is required. Is it valid for other reactions? What is theoretical explanation of this effect? How we can discriminate between models? There is no predictions for the most of the reactions except π-p↑→π0n and: It is very interesting to measure these processes with good accuracy. PROZA – answers and questionsexclusive V. Mochalov, PROZA-M experiment

  21. Asymmetry mainly does not depend on energy (see also E704, BNL, RHIC) Essential asymmetry was found for u- and d- quark particles. Asymmetry is quark flavor dependend (pion and proton beams). Asymmetry in η production is bigger than in π0 production (see also STAR) Asymmetry increases with p_T at the central region in the reaction π-p↑→π0X Threshold effect and scaling was observed. Asymmetry in non-polarized beam and polarized target (beam) regions close to the edge of phase space is equal in the reaction π-p↑→π0X We have very good possibility to measure asymmetry in different channels at intermediate energies with good accuracy. PQCD type models do not work at these energies? What is the asymmetry for ss-bar and heavier states (φ and others)? Most of the models can not predict non-zero asymmetry in the central region and describe p_T behavior. It is very important to measure asymmetry in wide kinematic region in different channels to discriminate between different models. PROZA – answers and questionsinclusive V. Mochalov, PROZA-M experiment

  22. We have found a lot of interesting in spin physics We all have desires, possibilities and duties trying to find much more inviting and unpredictable V. Mochalov, PROZA-M experiment

  23. Backup slides V. Mochalov, PROZA-M experiment

  24. IHEP/1968 -1977HERA Collaboration (France-USSR) • Polarization in elastic scattering of particles and antiparticles on polarized protons at 40 and 45 GeV. • Pomeron may carry the spin flip interaction (the first experimental hint) • Polarization in the elastic scattering of particle and antiparticle is not equal each to other with opposite sign in general, as it was predicted in the asymptotic model [S.M. Bilenky et al. 1963] • The energy variation of polarization depends on the type of particles and the magnitude of t. • Spin rotation parameter is consistent with the Chou - Yang model of rotating hadronic matter. • Chirality conservation hypothesis does not work V. Mochalov, PROZA-M experiment

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