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

5 September 2009V. Mochalov, PROZA-M experiment2 Introduction remark This talk itself is sad in some sense: This talk itself is sad in some sense: This is probably the last report devoted to the current PROZA activity 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 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) Nevertheless new spin program at IHEP is under preparation (see next talk by S.Nurushev)

5 September 2009V. Mochalov, PROZA-M experiment3 Outline Recent Single-spin asymmetry results from PROZA Recent Single-spin asymmetry results from PROZA A N in the beam (non-polarized) fragmentation region A N in the beam (non-polarized) fragmentation region A N in the target (polarized) fragmentation region A N in the target (polarized) fragmentation region Review of previous results from PROZA Review of previous results from PROZA Polarization and single-spin asymmetry in exclusive (charge-exchange) reactions Polarization and single-spin asymmetry in exclusive (charge-exchange) reactions Single-spin asymmetry in inclusive reactions in the central region Single-spin asymmetry in inclusive reactions in the central region PROZA – answers and questions (instead of conclusion) PROZA – answers and questions (instead of conclusion)

5 September 2009V. Mochalov, PROZA-M experiment4 Asymmetry in the beam fragmentation region Negative beam (π - /K/p-bar:97.9/1.8/0.3%) Negative beam (π - /K/p-bar:97.9/1.8/0.3%) Beam particle identification Beam particle identification Propane-diol (C 3 H 8 O 2 ) target with 90% average polarization (diameter 20 mm, length 200 mm ) Propane-diol (C 3 H 8 O 2 ) target with 90% average polarization (diameter 20 mm, length 200 mm ) Neutral particle trigger Neutral particle trigger EMC (800 lead glass channels) with trigger on transverse momenta p T EMC (800 lead glass channels) with trigger on transverse momenta p T

5 September 2009V. Mochalov, PROZA-M experiment5 Negative particle beam profile on the target  x(target) =  y(target) =3.5 mm (98% inside the target)  x(target) =  y(target) =3.5 mm (98% inside the target)

5 September 2009V. Mochalov, PROZA-M experiment6 A N in the A N in the π - d ↑ →π 0 X reaction A N in the (GeV/c) A N in the K - d ↑ →π 0 X reaction is equaled zero (-0.4  6.1)% at 0.6<p T (GeV/c) <1.2 and (GeV/c) A N =(11  6.1)% at p T >1.2 (GeV/c)

5 September 2009V. Mochalov, PROZA-M experiment7 p T dependence of A N in the beam fragmentation region Asymmetry is zero at small p T (red points – previous results, published in 1989 ) and Asymmetry is zero at small p T (red points – previous results, published in 1989 ) and Is significant at large p T : A N =(13.6  2.6(stat)  2.0(syst))% at p T >1 (GeV/c) and 0.7 (0.7 1 (GeV/c) and 0.7 (0.7<x F <1.0)

5 September 2009V. Mochalov, PROZA-M experiment8 First asymmetry measurements at the polarized target fragmentation region Asymmetry in the inclusive π 0 -production in the polarized target fragmentation region was measured in in the reactions π - p ↑ →π 0 X pp ↑ →π 0 X A N increases with |x F | increased. The result is in agreement with E704 and STAR data. pp ↑ →π 0 X, Phys.At.Nucl, 68 (2005)1790Phys.At.Nucl, 68 (2005)1790 π - p ↑ →π 0 X, Phys.At.Nucl, 67 (2004) 1495Phys.At.Nucl, 67 (2004) 1495

5 September 2009V. Mochalov, PROZA-M experiment9 Final PROZA-2 measurements Asymmetry in in the polarized target fragmentation region at 50 GeV. Asymmetry in pp ↑ →π 0 X in the polarized target fragmentation region at 50 GeV. Two sets of data (2005 and 2007) are being used for analysis. Two sets of data (2005 and 2007) are being used for analysis. EMC consists of 720 lead glass blocks EMC consists of 720 lead glass blocks proton beam up to 7∙10 6 p/cycle proton beam up to 7∙10 6 p/cycle

5 September 2009V. Mochalov, PROZA-M experiment10 Beam properties and stability Proton beam was extracted from U70 vacuum chamber using bent crystal (80 mrad) Proton beam was extracted from U70 vacuum chamber using bent crystal (80 mrad)  x =2.7 mm,  y =3.7 mm  x =2.7 mm,  y =3.7 mm  P/P<0.013%  P/P<0.013% Beam position stability  <0.1 mm

5 September 2009V. Mochalov, PROZA-M experiment11 γ and π 0 reconstruction in EMC EMC-720 was adjusted to measure low energy gammas (2.2 MeV/ADC channel) EMC-720 was adjusted to measure low energy gammas (2.2 MeV/ADC channel) Nevertheless reconstructed energy depends on real γ energy Nevertheless reconstructed energy depends on real γ energy EMC is 2.3 m downstream target: EMC is 2.3 m downstream target: Reconstructed energy depends on angle of incident γ Reconstructed energy depends on angle of incident γ Special algorithm was developed Special algorithm was developed

5 September 2009V. Mochalov, PROZA-M experiment12 π 0 mass  (π 0 )=17 MeV (left)  (π 0 )=17 MeV (left) after correction (circles) does not depend on angle and energy (right) after correction (circles) does not depend on angle and energy (right)

5 September 2009V. Mochalov, PROZA-M experiment13 π 0 kinematics

5 September 2009V. Mochalov, PROZA-M experiment14 A N in the reaction (close to final) at 50 GeV ( data) A N in the reaction pp ↑ →π 0 X (close to final) at 50 GeV ( data) xFxFxFxF A N,% -( ) -(0.8  2.2) -( ) -(2.0  1.8) -( ) -(1.5  1.9) -( ) -(2.3  2.1) -( ) -(5.8  1.8) -( ) -(6.8  4.1) -( ) -(11.0  5.8) -(6.2  1.5) At -0.6<x F <-0.25 single spin asymmetry A N = -(6.2  1.5) % Preliminary

5 September 2009V. Mochalov, PROZA-M experiment15 Comparison of the asymmetry with other experiments A N in the inclusive π 0 production at polarized particle fragmentation region at 0.25<x F <0.6 at 50 GeV (6.2  1.5)% is in a very good agreement with other experiments: A N in the inclusive π 0 production at polarized particle fragmentation region at 0.25<x F <0.6 at 50 GeV (6.2  1.5)% is in a very good agreement with other experiments: A N In the reaction π - p ↑ →π 0 X at 40 GeV (6.9  2.8) A N In the reaction π - p ↑ →π 0 X at 40 GeV (6.9  2.8) With E704 data at 200 GeV (6.3  0.7) With E704 data at 200 GeV (6.3  0.7) A N in inclusive π 0 production does NOT depend on beam energy.

5 September 2009V. Mochalov, PROZA-M experiment16 Polarization in the reaction Polarization in the reaction π - p ↑ →π 0 n Polarization P(t) in the range of 0<|t|<0.35 (GeV/c) 2 equals 5.0  0.7%. There is a minimum at "crossover" effect region t=-0.25 (GeV/c) 2 Polarization changes 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: ,1987] V.D. Apokin et al. Z.Phys.C15:293,1982

5 September 2009V. Mochalov, PROZA-M experiment17 Polarization in the reactions and 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 An essential polarization in wide interval of 0.05<-t<1.6 (GeV/c) 2 in at 40 GeV. π - p ↑ →  n at 40 GeV. In the region 0.05<-t<0.4 (GeV/c) 2 polarization is small (-5% ); 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. A N =(-44  11)% at the |t| range of (GeV/c) 2 with -t increasing up to ~1(GeV/c) 2, the polarization absolute value increases. A N =(-44  11)% at the |t| range of (GeV/c) 2 polarization changes a sign near -t=1.8 (GeV2/c) 2. polarization changes a sign near -t=1.8 (GeV2/c) 2. The averaged value of the polarization in the reaction in the region of 0.05< -t <0.5 (GeV2/c) 2 is (-17  8)%. 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.

5 September 2009V. Mochalov, PROZA-M experiment18 Asymmetry in the reactions and Asymmetry in the reactions π - p ↑ →  (783)n and π - p ↑ →f 2 (1270)n  was registered via  γ decay (branching only 8.9%).  was registered via  γ decay (branching only 8.9%). Asymmetry is large in both reactions Asymmetry is large in both reactions Indication on minimum at –t=0.2 (GeV/c) 2 for 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: ,1988]

5 September 2009V. Mochalov, PROZA-M experiment19 Asymmetry in inclusive π 0 production at x F =0 Asymmetry in the reaction Asymmetry in the reaction π - p(d) ↑ →π 0 X 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 Asymmetry in the reaction pp ↑ →π 0 X is zero at the whole p T interval. The result confirms E-704 measurements at 200 GeV. pp ↑ → π 0 X, Phys.At.Nucl, 67 (2004) 1487Phys.At.Nucl, 67 (2004) 1487 π - p ↑ →π 0 X, Phys.Lett.B243,461 (1990)Phys.Lett.B243,461 (1990)

5 September 2009V. Mochalov, PROZA-M experiment20 PROZA – answers and questions exclusive Essential polarization (asymmetry) was found in all reactions Essential polarization (asymmetry) was found in all reactions There is indication on asymmetry oscillations There is indication on asymmetry oscillations There is a minimum at "crossover" effect region in Polarization changes sign in the dip region in the disserential cros- section There is a minimum at "crossover" effect region in π - p ↑ →π 0 n Polarization changes sign in the dip region in the disserential cros- section Simple Regge model can not describe polarization modification required: Simple Regge model can not describe polarization modification required: U matrix with pomeron spin-flip U matrix with pomeron spin-flip Odderon pole is required in addition to ρ-pole Odderon pole is required in addition to ρ-pole Prediction: P( Prediction: P(π 0 )+2P(η)=P(η) a 0 (980) – see Achasov. a 0 (980) – see Achasov. Does the asymmetry magnitude increase with meson mass? Does the asymmetry magnitude increase with meson mass? Is it real effect for all particles? Better accuracy is required. Is it real effect for all particles? Better accuracy is required. Is it valid for other reactions? Is it valid for other reactions? What is theoretical explanation of this effect? What is theoretical explanation of this effect? How we can discriminate between models? How we can discriminate between models? There is no predictions for the most of the reactions except and: There is no predictions for the most of the reactions except π - p ↑ →π 0 n and: It is very interesting to measure these processes with good accuracy. It is very interesting to measure these processes with good accuracy.

5 September 2009V. Mochalov, PROZA-M experiment21 PROZA – answers and questions inclusive Asymmetry mainly does not depend on energy (see also E704, BNL, RHIC) Asymmetry mainly does not depend on energy (see also E704, BNL, RHIC) Essential asymmetry was found for u- and d- quark particles. 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 π 0 production (see also STAR) Asymmetry is quark flavor dependend (pion and proton beams). Asymmetry in η production is bigger than in π 0 production (see also STAR) Asymmetry increases with p_T at the central region in the reaction Asymmetry increases with p_T at the central region in the reaction π - p ↑ →π 0 X Threshold effect and scaling was observed. 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 Asymmetry in non-polarized beam and polarized target (beam) regions close to the edge of phase space is equal in the reaction π - p ↑ →π 0 X We have very good possibility to measure asymmetry in different channels at intermediate energies with good accuracy. 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? PQCD type models do not work at these energies? What is the asymmetry for ss-bar and heavier states (φ and others)? 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. 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. It is very important to measure asymmetry in wide kinematic region in different channels to discriminate between different models.

5 September 2009V. Mochalov, PROZA-M experiment22 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

5 September 2009V. Mochalov, PROZA-M experiment23 Backup slides

5 September 2009V. Mochalov, PROZA-M experiment24 IHEP/ HERA Collaboration (France-USSR ) Polarization in elastic scattering of particles and antiparticles on polarized protons at 40 and 45 GeV. 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) 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] 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. 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. Spin rotation parameter is consistent with the Chou - Yang model of rotating hadronic matter. Chirality conservation hypothesis does not work Chirality conservation hypothesis does not work