Project «GDH» & «SPASCHARM»
A Study of the Nucleon Spin Structure in
Strong and Electromagnetic Interactions
Dubna-Protvino-Prague-Moscow-Mainz-Glasgow-Los
Angeles-Basel-Edinburg-Zagreb-Pavia-LundKharkov-Bochum
S.B. Gerasimov
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
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

(
E



(
E

e


I
dv

4

Sk


p
GDH

thr


a
v
2
2
2
Anomalous
2
M
magnetic moment
production
threshol
(nucleo



thr
photodisin
tegration
thresho
(nucle

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))
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 SETUP
Because 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
4 Complex amplitudes - 16 real polarization observables.
A complete measurement from 8 carefully chosen observables.
I. S. Barker, A. Donnachie, J. K. Storrow, Nucl. Phys. B95, 347 (1975).
First experiment:
Transverse asymmetries T and F in π0 and η
photoproduction
Physics motivation:
Measurement of the target asymmetry T and the double-polarisation
observable F in order to investigate interference effects between the
S11(1535) and the D13(1520) nucleon resonances and to determine the
energy-dependent phase shift between s and d waves, which is not yet
taken into account by isobar models (MAID, SAID) for η
photoproduction.
Equipment:
A beam of circularly polarised photons, energy-tagged by the GlasgowMainz tagging system, in combination with a transversely polarised
'Frozen Spin' butanol target. The reaction products are detected using
the Crystal Ball / TAPS 4π photon spectrometer; the PID detector and
the cylindrical wire chambers perform particle identication and track
reconstruction 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 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.
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 channels
A1/2
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
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)
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
Proposed schedule and necessary resources for realization of the Project ”SPASCHARM-GDH” (k$)
Total
cost
Title of expense item
Laboratory proposals for
distribution of finances
2011
2012
2013
1. The modification of the UHF system of the polarized target
15.0
9.0
2.0
4.0
2. Design and preparation of the parts of ”Active Target”
6.0
4.0
2.0
-
3. Modification of the polarization measurement system
4.0
2.0
2.0
-
4. Purchase standard devices
41.0
16.0
14.0
11.0
TOTAL (equipment)
66.0
31.0
20.0
15.0
Materials
26.0
10.0
8.0
8.0
TOTAL
92.0
41.0
28.0
23.0
a) direct (immediate)
92.0
41.0
28.0
23.0
b) Grants of Germany (BMBF)
45.0
15.0
15.0
15.0
Total immediate expenses
137.0
56.0
43.0
38.0
2. Out of budget financing
30.0
10.0
10.0
10.0
a) Collaborator aid
15.0
5.0
5.0
5.0
b) Grant (Russia) financing
15.0
5.0
5.0
5.0
Finance sources
1. Budget expenses:
Leader of the Project
Deputies of the Leaders
A. Kovalik, Yu.A. Usov
S.B. Gerasimov, I.L. Pisarev
Form №29
Estimate of the expenses for the Project ”SPASCHARM-GDH” (k$)
Title of expense item
Total
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
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
Inclusive
Leader of the Project
Deputies of the Leaders
Director of the Laboratory
Leading engineer-economist
A. Kovalik, Yu.A. Usov
S.B. Gerasimov, I.L. Pisarev
A.G. Olshevsky
O.N. Shestakova