A Study of the Nucleon Spin Structure inStrong and Electromagnetic Interactions

Dubna-Protvino-Prague-Moscow-Mainz-Glasgow-LosAngeles-Basel-Edinburg-Zagreb-Pavia-Lund-

Kharkov-Bochum

S.B. Gerasimov

Project «GDH» & «SPASCHARM»

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

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 production to understand charmonium hadronic production mechanism and to extract gluon polarization Δg(x) at large x

Strong Interactions

Experiments:

• Measurement of single-spin asymmetries in the production of miscellaneous light resonances with the use of 34 GeV π- beam

• Measurement of single-spin and double-spin asymmetries in charmonium production with the use of 70 GeV polarized proton beam

Strong Interactions

Equipment:

U70 accelerator at Protvino• Unpolarised π- beam; E = 34 GeV

• Polarized proton beam; E = 70 GeV

• Large frozen spin proton target at Protvino

SPASCHARM experimental setup

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.

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

Electromagnetic Interactions(Mainz, A2-collaboration)

• Motivation

• Equipment

• Experiments

hadron-spinphoton-spin hadron-spinphoton-spin

a p

22

224

((k

M

eSdv

v

EEI

thr

apGDH

Anomalous magnetic moment

1) Experimental verification of the GDH sum rule

(nuclei) threshold tegrationphotodisin

(nucleon) threshold production thr

Proposed in 1966

Prediction on the absorption of circularly polarized photons by longitudinally polarized hadrons

More detailed information on resonance propertiesand multipole amplitudes

by investigating the helicity structure of

partial reaction channels

More detailed information on resonance propertiesand 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))

2) Helicity Dependence of Meson Photoproduction

MAINZ MICROTRON continuous polarized electron beam, E=1.5 GeV,

Pe=85%

Glasgow-Mainz Photon Tagger

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

A2 DETECTOR SETUPBecause of its high-granularity and large acceptance the CB/TAPS setup is a suitable detector system for measurements of reactions with multi-photon final

states like in π0 → 2γ, η → 2γ or η → 3π0 → 6γ

I. S. Barker, A. Donnachie, J. K. Storrow, Nucl. Phys. B95I. S. Barker, A. Donnachie, J. K. Storrow, Nucl. Phys. B95,, 347 347 (1975).(1975).I. S. Barker, A. Donnachie, J. K. Storrow, Nucl. Phys. B95I. S. Barker, A. Donnachie, J. K. Storrow, Nucl. Phys. B95,, 347 347 (1975).(1975).

44 Complex amplitudes - Complex amplitudes - 1616 real polarization observables. real polarization observables.A A complete measurement fromcomplete measurement from 88 carefully chosen carefully chosen observablesobservables. .

First experiment:Transverse asymmetries T and F in π0 and η

photoproductionPhysics motivation:Measurement of the target asymmetry T and the double-polarisationobservable F in order to investigate interference effects between theS11(1535) and the D13(1520) nucleon resonances and to determine theenergy-dependent phase shift between s and d waves, which is not yettaken into account by isobar models (MAID, SAID) for η photoproduction.

Equipment:A beam of circularly polarised photons, energy-tagged by the Glasgow-Mainz tagging system, in combination with a transversely polarised'Frozen Spin' butanol target. The reaction products are detected usingthe Crystal Ball / TAPS 4π photon spectrometer; the PID detector andthe cylindrical wire chambers perform particle identication and trackreconstruction for charged particles.

The cross section for single meson production in case of a transversely polarised target and a circularly polarised

photon beam

As the target asymmetry T is a single polarisation observables, it isaccessible with only a polarised target and an unpolarised photonbeam. However, using a circularly polarised photon beam does notaffect this asymmetry but gives also access to the double-polarisationobservable F. The target asymmetry T can be extracted integratingover both helicity states of the incoming circularly polarised photons,which eliminates any contributions from F.

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.

Helicity amplitudes in proton and neutron channelsA1/2 A3/2

N* MAID2005 SAID PDG MAID2005 SAID PDG

P33(1232) -137 -129 ± 1 -135 ± 6 -260 -243 ± 1 -255 ± 8

P11(1440) -61 -67 ± 2 -65 ± 4 - - -

D13(1520) -27 -24 ± 2 -24 ± 9 161 135 ± 2 166 ± 8

S11(1535) 66 30 ± 3 90 ± 30 - - -

S31(1620) 66 -13 ± 3 27 ± 11 - - -

S11(1650) 33 74 ± 1 53 ± 16 - - -

D15(1675) 15 33 ± 4 19 ± 8 22 9 ± 3 15 ± 9

F15(1680) -25 -13 ± 2 -15 ± 6 134 129 ± 2 133 ± 12

D33(1700) 226 89 ± 10 104 ± 15 210 92 ± 7 85 ± 22

P13(1720) 73 - 18 ± 30 -11 - -19 ± 20

F35(1905) 18 2 ± 5 26 ± 11 -28 -56 ± 5 -45 ± 20

F31(1910) 18 - 3 ± 14 - - -

F37(1950) -94 -62 ± 4 -76 ± 12 -121 -80 ± 3 -97 ± 10

P11(1440) 54 47 ± 5 40 ± 5 - - -

D13(1520) -77 -67 ± 4 -59 ± 9 -154 -112 ± 3 -139 ± 11

S11(1535) -51 -16 ± 5 -46 ± 27 - - -

S11(1650) 9 -28 ± 4 -15 ± 21 - - -

D15(1675) -62 -50 ± 4 -43 ± 12 -84 -71 ± 5 -58 ± 13

F15(1680) 28 29 ± 6 29 ± 10 -38 -58 ± 9 -33 ± 9

P13(1730) -3 - -1 ± 15 -31 - -29 ± 61

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 system Crystal Ball/TAPS: measurement of reaction products in 4π geometry

• PAC-2009 of CB-MAMI collaboration: 9 of 14 proposals – various double polarization experiments

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.

1.5 K radiation shield

25 K radiation shield

Separator (3K) and Evaporator (1.2K) precooling stages (4He)

80 K radiation shield

3He/4He Dilution stageTmin ≈ 23 mK

Polarization ≈ 94% Relaxation ≈ 1500 hours

≈≈

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)

Main parameters

• 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

Working plan 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).

Form №26

Title of expense itemTotalcost

Laboratory proposals fordistribution of finances

2011 2012 2013

1. The modification of the UHF system of the polarized target 15.0 9.0 2.0 4.0

2. Design and preparation of the parts of ”Active Target” 6.0 4.0 2.0 -

3. Modification of the polarization measurement system 4.0 2.0 2.0 -

4. Purchase standard devices 41.0 16.0 14.0 11.0

TOTAL (equipment) 66.0 31.0 20.0 15.0

Materials 26.0 10.0 8.0 8.0

TOTAL 92.0 41.0 28.0 23.0

Finance sources

1. Budget expenses:

a) direct (immediate) 92.0 41.0 28.0 23.0

b) Grants of Germany (BMBF) 45.0 15.0 15.0 15.0

Total immediate expenses 137.0 56.0 43.0 38.0

2. Out of budget financing 30.0 10.0 10.0 10.0

a) Collaborator aid 15.0 5.0 5.0 5.0

b) Grant (Russia) financing 15.0 5.0 5.0 5.0

Proposed schedule and necessary resources for realization of the Project ”SPASCHARM-GDH” (k$)

Leader of the Project A. Kovalik, Yu.A. UsovDeputies of the Leaders S.B. Gerasimov, I.L. Pisarev

Form №29

Title of expense itemTotal cost

2011 2012 2013

1 R & D agreement expenses 15.0 11.0 2.0 2.0

2 Job cost in the LNP’s experimental shop 2.0 1.0 1.0 -

3 Materials 26.0 10.0 8.0 8.0

4 Transport expenses 2.0 1.0 1.0 -

5 Unforeseen expenses 6.0 2.0 1.0 2.0

6 Electronic instruments 41.0 16.0 14.0 11.0

7 Travel expenses 45.0 15.0 15.0 15.0

Inclusive

a) to nonruble zone countries 30.0 10.0 10.0 10.0

b) to ruble zone countries 12.0 4.0 4.0 4.0

c) visits to JINR 3.0 1.0 1.0 1.0

Total immediate expenses: 137.0 56.0 43.0 38.0

Estimate of the expenses for the Project ”SPASCHARM-GDH” (k$)

Leader of the Project A. Kovalik, Yu.A. UsovDeputies of the Leaders S.B. Gerasimov, I.L. PisarevDirector of the Laboratory A.G. OlshevskyLeading engineer-economist O.N. Shestakova