A Study of the Nucleon Spin Structure in Strong and Electromagnetic Interactions

1. Dubna-Protvino-Prague-Moscow-Mainz-Glasgow-Los Angeles-Basel-Edinburg-Zagreb-Pavia-Lund- Kharkov-Bochum S.B. Gerasimov A Study of the Nucleon Spin Structure inStrong and Electromagnetic Interactions Project «GDH» & «SPASCHARM»

2. Experiments with Polarized Targets and Beams. Projects ”GDH” & ”SPASCHARM” • Dubna, Dzhelepov Laboratory of Nuclear Problems, JINR N.A. Bazhanov, N.S. Borisov, A.N. Fedorov, I.V. Gapienko, V.A. Kalinnikov, A. Kovalik, E.S. Kuzmin, A.B. Lazarev, G.I. Lykasov, A.B. Neganov, I.L. Pisarev, Yu.A. Plis, S. Prakhov (UCLA), A.A. Priladyshev, A.B. Sadovski, S.N. Shilov, Yu.A. Usov, • Dubna, Flerov Laboratory of Nuclear Reactions, JINR M.P. Ivanov • Dubna, Bogoliubov Laboratory of Theoretical Physics, JINR S.B. Gerasimov, S.S. Kamalov • Protvino, Institute for High Energy Physics V.V. Mochalov, A.N. Vasiliev, N.I. Belikov, V.N. Grishin, A.M. Davidenko, A.A. Derevscikov, V.I. Kravtsov, Yu.A. Matulenko, Yu.M. Melnik, A.P. Meshanin, S.B. Nurushev, A.F. Prudkoglyad, L.F. Soloviev, A.E. Yakutin • Prague, Charles University J. Brož, J. Černy, Z. Doležal, P. Kodyš, P. Kubik J. Švejda, I. Wilhelm • Prague, IEAP, CTU F. Lehar, S. Pospišil, M. Solar • Moscow, Institute for Nuclear Research, Russian Academy of Science G.M. Gurevich, R.L. Kondratiev • Mainz, Institut für Kernphysik H.-J. Arends, M. Martinez, A. Thomas, E.-P. Schilling, M. Ostrick • Glasgow, Glasgow University, Los Angeles, University of California, UCLA, Basel, Institut f¨ur Physik, Edinburg, Department of Physics, University of Edinburg, Zagreb, Rujer Boskovic Institute, Pavia, Sezione di Pavia, INFN, Lund, MAX-lab., Lund University, Kharkov, Kharkov Institute of Physics and Technology, Bochum, Institut für Experimentalphysik Ruhr Universität Leader of the Project A.Kovalik, Yu.A. Usov Deputies of the Leaders S.B. Gerasimov, I.L. Pisarev

3. Strong Interactions(IHEP, Protvino) Goals: • Study of single-spin assymetry based on large statistics of the production of light meson resonances (ρ, ω etc) • Study of spin effects in charmonium productionto understand charmonium hadronic production mechanism and to extract gluon polarization Δg(x) at large x

4. Strong Interactions Experiments: • Measurement of single-spin asymmetries in the production of miscellaneous light resonances with the use of 34 GeVπ-beam • Measurement of single-spin and double-spin asymmetries in charmonium production with the use of 70GeV polarized proton beam

5. Strong Interactions Equipment: U70 accelerator at Protvino • Unpolarisedπ-beam; E = 34 GeV • Polarized proton beam; E = 70GeV • Large frozen spin proton target at Protvino

6. SPASCHARM experimental setup

7. First stage (unpolarized beams) • A study of the single spin assymetry AN of light resonances consisted of u-, d- and valence quarks. • Inclusive and exclusive reactions will be studied simultaneously. • The errors in the exclusive reactions with big asymmetries are expected to be several times less than now.

8. Second stage (polarized beams) • The goal of the proposed experiment is to measure double-spin asymmetry ALL with the use of longitudinally polarized beam and target in the process: p→ + p→ → χc2 (J/Ψ) + X, (χc2 → J/Ψ + γ). • The measured experimental asymmetry is given by where PB is the beam polarization, PTeef is the effective target polarization, I++ , I+− are the number of events normalized to the incident beam

9. Electromagnetic Interactions(Mainz, A2-collaboration) • Motivation • Equipment • Experiments

10. 1) Experimental verification of the GDH sum rule • Proposed in 1966 • Prediction on the absorption of circularly polarized photons by longitudinally polarized hadrons photon-spin hadron-spin photon-spin hadron-spin p a Anomalous magnetic moment

11. 2) Helicity Dependence of Meson Photoproduction More detailed information on resonance properties and multipole amplitudes by investigating the helicity structure of partial reaction channels Main goals: single- production (D13 (1520), F15 (1680)) - production (S11 (1535), D13 (1520)) double  - production (D13 (1520), P11 (1440), P11 (1710))

12. MAINZ MICROTRON continuous polarized electron beam, E=1.5 GeV, Pe=85%

13. Glasgow-Mainz Photon Tagger

14. Polarisation transfer from electron to photon beam as a function of energy transfer

15. A2 DETECTOR SETUPBecause of its high-granularity and large acceptance the CB/TAPSsetup is a suitable detector system for measurements of reactions with multi-photon final stateslike in π0 → 2γ, η → 2γ or η → 3π0 → 6γ

16. 4 Complex amplitudes - 16 real polarization observables. A complete measurement from8 carefully chosen observables. I. S. Barker, A. Donnachie, J. K. Storrow, Nucl. Phys. B95, 347 (1975).

17. First experiment:Transverse asymmetries T and F in π0 and ηphotoproduction Physics motivation: Measurement of the target asymmetry T and the double-polarisation observable F in order to investigate interferenceeffects between the S11(1535) and theD13(1520) nucleon resonancesand to determine the energy-dependent phase shift between s and dwaves, which is not yet taken into account by isobar models (MAID,SAID) for η photoproduction. Equipment: A beam of circularly polarised photons, energy-tagged bythe Glasgow- Mainz taggingsystem, in combination with atransversely polarised 'Frozen Spin' butanol target. The reactionproducts are detected using the Crystal Ball / TAPS 4πphoton spectrometer; the PID detectorand the cylindrical wirechambers perform particle identication and track reconstructionfor charged particles.

18. The cross section for single mesonproduction in case of a transversely polarised target and a circularly polarised photon beam As the target asymmetry T is a single polarisation observables, it is accessible with only a polarised target and an unpolarised photon beam. However, using a circularly polarised photon beam does not affect this asymmetry but gives also access to the double-polarisation observable F. The target asymmetry T can be extracted integrating over both helicity states of the incoming circularly polarised photons, which eliminates any contributions from F.

19. The helicity dependent total cross section for semiexclusive channels a) γd→π0X (X=pn or d) and b) γd→π±NN (full circles) compared to our previous results (open circles) and to corresponding model predictions in the Δ-resonans region.

20. Helicity amplitudes in proton and neutron channels

21. SUMMARY • MAMI C: circularly and linearly polarized energy tagged photon beams up to 1.5 GeV • FST: longitudinally and transversely polarized proton and deuteron targets • Any combinations of beam and target polarizations are possible • Detecting systemCrystal Ball/TAPS: measurement of reaction products in 4πgeometry • PAC-2009 of CB-MAMI collaboration: 9 of 14 proposals – various double polarization experiments

22. SUMMARY • The new polarization program SPASCHARM is being prepared in Protvino. • Inclusive and exclusive reactions will be studied simultaneously. • All the new data will much help us to understand spin dependence of strong interactions in the quark confinement region. • The results on ∆g(x) at large x will be unique and complementary to those which exist and might be obtained at COMPASS, HERMES, RHIC and JLAB at smaller x.

25. 1.5 K radiation shield25 K radiation shield 80 K radiation shield ≈ ≈ 3He/4He Dilution stage Tmin ≈ 23 mK Polarization ≈94% Relaxation ≈1500 hours Separator (3K) and Evaporator (1.2K) precooling stages (4He)

27. Internal longitudinal Holding coil(solenoid coil manufactured of 0.227-μm multifilamental NbTi cable and consisting of four layers, each having 600 turns wound around a 0.3-mm thick copper holder, T ≈ 1.5 K)

29. Working parameters of the dilution cryostat are in agreement with the technical requirements: - Tmin≈ 23 mK; - polarization relaxation time ≈ 1500 hours (at T=30 mK); - time to cool from room temperature ≈ 5 hours; - LHe consumption in the frozen spin mode ≈ 2 l/hour Internal holding coils provide longitudinal/ transverse field 0.4 Tesla at 30 A Any combinations of beam and target polarizations are possible Two-part insert makes the sample loading operation easy and convenient Future development: New insert, containing light-guides, for active polarized target Main parameters

30. 2011: − Design of the ”Active Target” (GDH). − First measurement of the spin asymmetry in meson photo production up to 1500 MeV using linearly polarized photon beam and transversely polarized proton target (GDH). − Measurement of the single-spin asymmetry AN of light reso nances consisting of u−, d− and s−valence quarks (SPASCHARM). 2012: − Measurement of transverse asymmetries T and F in η-photoproduction in the region of S11 (1535) resonance (circularly polarized photon beam and transversely polarized proton target) (GDH). − Manufacturing and tests of the ”Active Target” (GDH). − Measurement of AN for inclusive and exclusive reactions π p → ω(782)n and π − p → η (958)n (SPASCHARM). 2013: − Upgrade of the proton frozen spin target to the polarized deuteron variant. Measurement of the helicity dependence of single and double pion photoproduction processes and the GDH integral on the neutron (circularly polarized photons up to 1450 MeV and longitudinally polarized deuteron target) (GDH). − Experiments with the ”Active Target” (GDH). − Measurements of the single-spin asymmetry AN in charmonium production (SPASCHARM). Working plan

31. Form №26 Proposed schedule and necessary resources for realization of the Project ”SPASCHARM-GDH” (k$) Leader of the Project A. Kovalik, Yu.A. Usov Deputies of the Leaders S.B. Gerasimov, I.L. Pisarev

32. Form №29 Estimate of the expenses for the Project ”SPASCHARM-GDH” (k$) Leader of the Project A. Kovalik, Yu.A. Usov Deputies of the Leaders S.B. Gerasimov, I.L. Pisarev Director of the Laboratory A.G. Olshevsky Leading engineer-economist O.N. Shestakova