1. SPIN-Praha-2005 Dubna "Delta-Sigma" Experiment
Measurements of Energy Behaviours of Spin-Dependent np Observables over a GeV Region
Dubna "Delta-Sigma" Experiment
New accurate data on the neutron-proton spin-dependent total cross section difference ΔσL(np) at the neutron beam kinetic energies 1.4, 1.7, 1.9 and 2.0 GeV are presented.
A number of physical and methodical results on investigation of an elastic nppn charge exchange process
at 0º over GeV region are also presented.
Measurements were carried out at the Synchrophasotron and at the Nuclotron of the Veksler and Baldin Laboratory of High Energies of the Joint Institute for Nuclear Research.
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2. Plan of Talk
Introduction. Aims of the "Delta-Sigma" experiment. Program, Tools, Participants.
Determination of ΔσL,T(np) Observables and Method of Measurements.
Experimental Set-Up for the ΔσL,T(np) Measurements.
Parameters of Detectors and Neutron Beam and Results of σtot(np) and σtot(nC) Measurements.
The ΔσL(np) and ΔσL(I=0) Results and Discussion.
Determination of A00kk(np), A00nn(np) and Rdp Observables.
Magnetic Spectrometer for Investigation of Elastic nppn Charge Exchange Process.
A Number of Results on the Elastic nppn Charge Exchange Process Detection.
Conclusion.
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3. The investigations are being carried out under the program of the first priority JINR project of "Delta-Sigma" Experiment.
The aim of the project is to extend investigations of NN interaction over a new high 1.2 – 3.7 GeV energy region of free polarized neutron beams, provided at present only by the JINR VBLHE accelerators.
The main task of these studies is determination for the first time the imaginary and real parts of spin-dependent forward scattering NN amplitudes over this energy region.
To reach this aim, a sufficient data set on energy dependencies of np spin-dependent observables have to be obtained for direct and simple reconstruction of these amplitudes.
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4. The Delta-Sigma Experiment Research Program
Using
longitudinally (L) and transverse (T) polarized neutron beams and
the Dubna movable polarized proton target
to measure the energy dependencies of
a) ΔσL(np) and ΔσT(np) – the total cross section differences for parallel and antiparallel directions of beam and target polarizations, with energy steps of 100–200 MeV and expected statistical errors of 1 mb;
The observables ΔσL(np) and ΔσT(np) are linearly related to the imaginary parts of the two spin-dependent forward scattering invariant amplitudes c and d via optical theorems and allow to extract these imaginary parts.
b) (simultaneously and independently with the ΔσL,T(np) measurements) spin-correlation parameters A00kk(np) (together with ΔσL(np)) and A00nn(np) (together with ΔσT(np)) with expected statistical errors of 0.02 – 0.05.
The A00kk(np) and A00nn(np) values will be obtained from a registration of yields of elastic charge exchange process np pn at 0 angle. They are related to the real part of mentioned above amplitudes and data to be obtained will be used to extract ones.
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5. The Delta-Sigma Experiment Research Program
2. Using
high intensity unpolarised neutron beam and
liquid hydrogen and deuterium targets, to measure
at the same energies as for i. 1. the ratio Rdp=[dσ/dΩ(nd)] / [dσ/dΩ(np)] for elastic charge exchange process np pn at 0 angle with 5% statistical errors.
The ratio Rdp of differential cross sections on deuterium and hydrogen targets gives an additional relation between spin-dependent NN-amplitudes and a set of such data allows to avoid uncertainties of real parts extraction.
The data set on energy behaviors of spin-dependent observables ΔσL,T(np), A00kk(np), A00nn(np) and Rdp will be obtained for the first time over the energy range of neutron beam of 1.2–3.7 GeV.
Besides the direct amplitude reconstruction, this data set will be used to extend NN phase shift analysis to more high energies and to check of predictions of dynamical models.
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6. Accelerators and Tools
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Accelerators and Tools
THE SYNCHROPHASOTRON AND NUCLOTRON (VBLHE, JINR)
RELATIVISTIC (1 – 5) GEV
POLARIZED NEUTRON BEAMS
ORIENTATION OF POLARIZATION L OR T
REVERSION OF POLARIZATION DIRECTION CYCLE BY CYCLE
AVERAGE POLARIZATION VALUE OF 0.53
HIGH INTENSITY UNPOLARIZED NEUTRON BEAM
LARGE POLARIZED PROTON TARGET
VOLUME 140 cm3
POLARIZATION VALUE OF 0.7–0.8
CRYOGENIC HYDROGEN-H2 AND DEUTERIUM-D2 TARGETS (L=30 cm)
“ DELTA-SIGMA” SET-UP:
TRANSMISSION NEUTRON DETECTORS
MAGNETIC SPECTROMETER WITH PROPORTIONAL CHAMBERS
DETECTORS FOR TARGET SURROUNDING
TOF SYSTEM
MODERN DATA ACQUISITION SYSTEM
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7. Participants of the "DELTA-SIGMA" experiment
S.A.Averichev, L.S.Azhgirey, N.G.Anischenko, V.D.Bartenev, A.Bazhanov, N.A.Blinov, N.S.Borisov, S.B.Borzakov, Yu.T.Borzunov, T.N.Borzunova, E.I.Bunyatova, V.F.Burinov, Yu.P.Bushuev, L.P.Chernenko, E.V.Chernykh, V.F.Chumakov, S.A.Dolgii, A.N.Fedorov, V.V.Fimushkin, M.Finger1, M.Finger,Jr., L.B.Golovanov, D.K.Guriev, A.Janata2, A.D.Kirillov, V.G.Kolomiets, E.V.Komogorov, A.D.Kovalenko, I.G.Konskii, N.I.Kochelev, V.A.Krasnov, E.S.Kuzmin, N.A.Kuzmin, V.P.Ladygin, A.B.Lazarev, A.N.Livanov, P.K.Maniakov, E.A.Matyushevsky, A.A.Morozov, A.B.Neganov, G.P.Nikolaevsky, A.A.Nomofilov, Tz.Panteleev3, Yu.K.Pilipenko, I.L.Pisarev, Yu.A.Plis, R.V.Polyakova, V.Yu.Prytkov, P.A.Rukoyatkin, V.I.Sharov, T.V.Shavrina, S.N.Shilov, R.A.Shindin, Yu.A.Shishov, V.B.Shutov, O.N.Schevelev, M.Slunechka, V.Slunechkova, A.Yu.Starikov, L.N.Strunov, Yu.A.Usov, T.A.Vasiliev, V.I.Volkov, E.I.Vorobiev, I.P.Yudin, I.V.Zaitsev, V.N.Zhmyrov,
Joint Institute for Nuclear Research, Dubna
1 Charles University, Praha, Czech Republic
2 Institute for Nuclear Research, Rez, Czech Republic
3 Institute for Nuclear Research and Nuclear Energy, BAS, Sofia, Bulgaria
V.G.Baryshevsky, K.G.Batrakov, T.I.Klimkovich, S.L.Cherkas
RNNP,Belorussian State University, Belorussia
A.I.Kovalev, A.N.Prokofiev, V.A.Schedrov, A.A.Zhdanov
Peterburg Institute of Nuclear Physics, Gatchina
G.M.Gurevich
Institute for Nuclear Research, RAS, Moscow
V.G.Antonenko, Yu.P.Polunin
Russian Scientific Center "Kurchatov Institute", Moscow
F.Lehar. A. de Lesquen
DAPNIA, Saclay, France
A.A.Belyaev, A.A.Lukhanin
Kharkov Institute of Physics and Technology, Kharkov, Ukraine
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8. Determination of ΔσL,T (np) Observables
We use NN formalism and the notations for elastic nucleon-nucleon scattering observables from J. Bystricky, F. Lehar and P.Winternitz. J. Phys. (Paris). 39, 1 (1978).
The general expression for the total cross section of a polarized nucleon beam trasmitted through a polarized proton target is (S.M.Bilenky and R.M.Ryndin, Phys.Lett. 6 (1963) 217, R.J.N. Phillips, Nucl.Phys. 43 (1963) 413):
σtot = σ0tot + σ1tot (PB PT) + σ2tot (PB k)(PT k), (1)
where PB and PT are the beam and target polarizations, and k is the unit vector in the incident beam direction.
The term σ0tot is the spin-independent total cross section, and σ1tot and σ2tot are the spin-dependent contributions which connect with the observables ΔσT and ΔσL by the relations:
– ΔσT = 2 σ1tot = [σtot (↑↑) – σtot (↓↑)]/PB PT, (2)
– ΔσL = 2 (σ1tot + σ2tot) = [σtot (→→) – σtot (→←)]/PB PT (3)
Values of σ0tot, ΔσT and ΔσL are connected with the imaginary parts of three invariant forward scattering amplitudes a + b, c and d via three optical theorems:
σ0tot = (2π/K) Im [a(0) + b(0)], (4)
– ΔσT = (4π/K) Im [c(0) + d(0)], (5)
– ΔσL = (4π/K) Im [c(0) – d(0)] (6)
From isotopic invariance of strong interaction, one can write the following expressions for total cross section differences at isosinglet and isotriplet states:
ΔσL,T (np) = ½ΔσL,T (I=0) + ½ΔσL,T (I=1), (7)
ΔσL,T (pp) = ΔσL,T (nn) = ΔσL,T (I=1), (8)
ΔσL,T (I=0) = 2 ΔσL,T (np) – ΔσL,T (pp) (9)
Using the last equation, one can obtain values of ΔσL,T (I=0) from known quantities of ΔσL,T (np) and ΔσL,T (pp), measured at the same energy.
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9. Method of the ΔσL,T (np) Measurements
The trasmission method is used to measure the total cross section differences ΔσL,T (np).
N = M exp[– σ(Ω) nx], σ(Ω) = ln(M/N)/(nx), (10)
where M is a flux of incident particles, N is a number of particles transmitted by target, N/M is a transmission of target at a solid angle Ω, and nx is the thickness of target in cm–2. Unpolarized total cross section σtot can be obtained by extrapolation of Ω 0.
Using expression (1), the corresponding equations can be obtained for ΔσL,T with different orientation of beam and target polarizations. For example
– ΔσT (PT±) = 2 σ1tot– = 2[σtot (↑↑) – σtot (↓↑)]/ (|PB+| + |PB–|) |PT±|. (11)
Finally, for both signs of target polarization
– ΔσL,T = ½(– ΔσL,T (PT+) + – ΔσL,T (PT–)), (12)
where
ΔσL,T (Ω, PT±) = Ln R(PT±) / PB · PT± · nHx, (13)
|PB| = ½(|PB+| + |PB–|), (14)
R± = (N/M)– / (N/M) (15)
Statistical uncertainty is:
δ(ΔσL,T)stat = √(1/M+ + 1/N+ + 1/M– + 1/N–) / PB∙PT∙nH∙x (16)
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10. DELTA-SIGMA Setup at the Polarized Neutron Beams of the JINR VBLHE
VP 1 – beam line of polarized deuterons; 1V – beam line of polarized neutrons;
BT – beryllium neutron production target; IC – ionization chamber;
PIC 1-3, 9-16 – multiwire proportional/ionization chambers; CM – sweeping magnet;
C1-C4 – set of neutron beam collimators; SRM – neutron spin rotating magnet;
PPT – polarized proton target; NP – neutron profilometer
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11. M1, M2 – monitor neutron detector modules;
Layout of the Detectors for the Neutron Transmission Measurement
M1, M2 – monitor neutron detector modules;
T1, T2, T3 – neutron transmission detector modules;
CH2 – converters; A, S1-S4 – scintillation counters;
PC – multiwire proportional chambers
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12. Polarized Neutron Beam Parameters
The beam of free quasi-monochromatic neutrons, polarized along the vertical directions, is obtained by break-up at 0 of vector polarized deuterons in the Beryllium target BT 20 cm×8×8 cm2.
Neutron beam is formed by a set of collimators C1–C4.
The deuteron bean momentum Pd is known with accuracy of ~1 %.
The neutron beam has the momentum Pn = Pd /2.
Intensity of prepared neutron beam at Tn = 3.7 GeV was ~2∙106 n/cycle.
For the ΔσL measurements, the neutron spins are rotated from vertical direction to the direction of beam momentum by spin rotating magnet SRM.
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15. Systematic Errors
For the measured ΔσL values, the relative normalization and systematic errors from different sources are summarized as follows:
Beam polarization over the run …….……... ± 0.9 %
Target polarization ………………….…….. ± 5.0 %
Number of the polarizable hydrogen atoms.. ± 1.1 %
Polarization of other atoms ………….……. ± 0.3 %
Magnetic field integral of the neutron spin rotator …………….…... ± 0.2 %
Inefficiencies of veto counters …………..… ± 0.1 %
Total of the relative systematic errors … ± 5.3 %
Absolute error due to the extrapolation of results towards 0º ………………………… < 0.04 mb
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16. Energy Dependence of the –ΔσL (np) Observable Obtained with Free Neutron Polarized Beams
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17. Energy Dependence of the –ΔσL (I=0)
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18. Measurements of the ΔσL (np) energy dependence were
in main completed using L-polarized neutron beam from the Synchrophasotron and the Dubna L-polarized proton target . Results were published in:
References on –ΔσL (np) results
B.P.Adiasevich, V.G.Antonenko, S.A.Averichev, L.S.Azhgirey et al. Zeitschrift fur Physik C71 (1996) 65.
V.I.Sharov, S.A.Zaporozhets, B.P.Adiasevich, V.G.Antonenko et al. JINR Rapid Communications 3[77]-96 (1996) 13.
V.I.Sharov, S.A.Zaporozhets, B.P.Adiasevich, N.G.Anischenko et al. JINR Rapid Communications 4[96]-99 (1999) 5.
V.I.Sharov, S.A.Zaporozhets, B.P.Adiasevich, N.G.Anischenko et al. European Physical Journal C13 (2000) 255.
V.I.Sharov, N.G.Anischenko, V.G.Antonenko, S.A.Averichev et al. Russian Journal "Yadernaya Fizika“ (2005). To be published.
V.I.Sharov, N.G.Anischenko, V.G.Antonenko, S.A.Averichev et al. European Physical Journal C37 (2004)
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19. Measurements of the ΔσL,T (np) and A00kk(np) and A00nn(np) energy dependences using L and T orientations of beam and target polarizations will be available in the near future when the new high intensity source of polarized deuterons (CIPIOS) will be put in operation at the Nuclotron and when the T mode of target polarization will be ready.
We would like remind that as a result of the project program, the complete L,T data set of the np spin observables at 0º will be first obtained over a GeV energy region. This data set allows us to perform the first direct reconstruction of all three forward NN elastic scattering isosinglet amplitudes over this energy region. Analysis of the energy behaviour of Re and Im parts of these amplitudes (Argand plots) allow us to look for and verify the detected signal of a possible exotic six-quark state excitation.
During the last period, in frame of the project experimental program, the studies of elastic np->pn charge exchange process are carried out using high intensity unpolarized neutron beams and cryogenic H2 and D2 targets (l=34 cm). The first results of these measurements will be presented below.
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20. Measurements of the A00kk(np) and A00nn(np) from nppn Process
If the scattered particles are detected at 0º angle then only two non-vanishing spin-dependent quantities A00nn(E,0º) and A00kk(E,0º)
can be measured from the nppn scattering.
C.Lechanoine-Leluc and F.Lehar. Rev. Mod. Phys. 65, 47 (1993).
J. Ball, R.Binz, J.Bystricky et al. Eur.Phys.J. C 5, 57 (1998).
These NN-observables are connected with invariant amplitudes by (the centre of mass system):
dσ/dΩ (π) = ½[|a|2 + |b|2 + |c|2 + |d|2], (17)
dσ/dΩ A00nn(π) = ½[|a|2 – |b|2 – |c|2 + |d|2], (18)
dσ/dΩ A00kk(π) = Re a* d + Re b* c. (19)
These equations can be transformed to:
dσ/dΩ (1 + A00kk) = |b + c|2 = A + (Re b + Re c)2, (20)
dσ/dΩ (1 – A00kk – 2A00nn) = |b – c|2 = B + (Re b – Re c)2, (21)
dσ/dΩ (1 – A00kk + 2A00nn) = |b + c – 2d|2 =
= C + (Re b + Re c – 2Re d)2, (22)
where terms A, B, C contain the amplitudes imaginary parts only.
The amplitudes real parts b, c, and d can be determined from equations (20), (21), (22) using known imaginary ones.
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21. Rdp (π) = (2/3) · dσ/dΩSD ( np) / dσ/dΩ(np), (24)
Experimental observable
Rdp = dσ/dΩ(nd) / dσ/dΩ(np) (23)
is the ratio of a quasi-elastic nd scattering differential cross section to the free np elastic scattering one. At θCM = π (F.Lehar. Private communication)
Rdp (π) = (2/3) · dσ/dΩSD ( np) / dσ/dΩ(np), (24)
Rdp (π) = (2/3) · [0.25 · |a - b| · ( |c|2 - |d|2 )] /
0.5 · ( |a|2 + |b|2 + |c|2 + |d|2 ), (25)
where dσ/dΩSD ( np) is the “spin-dependent” part of the nppn differential cross section.
Energy dependence of the ratio Rdp for elastic charge exchange process nppn at 0º in Lab (or elastic npnp backward scatteting in C.M.S.) are being measured using high intensity unpolarised neutron beam from the Nuclotron and the magnetic spectrometer of the Delta-Sigma set-up with liquid hydrogen and deuterium targets.
The values of Rdp give an additional relation between spin-dependent NN-amplitudes and a set of such data allows to avoid one uncertainty of extraction of amplitudes real parts.
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22. Magnetic Spectrometer for Detection of Protons from nppn Charge Exchange Process
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23. Detected Events Distribution in the θ vs φ Plane
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24. SPIN-Praha-2005

25. SPIN-Praha-2005

26. SPIN-Praha-2005

27. Separation of the p and d Particles in the TOF vs Momentum Plane
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28. Estimation of dσ/dΩ for quasi-elastic np scattering on D2 target at 1
Estimation of dσ/dΩ for quasi-elastic np scattering on D2 target at 1.8 GeV
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29. SPIN-Praha-2005

30. Energy dependences of differential cross sections of elasticnp→pn charge exchange at 0˚ CM (F.Lehar. Private communication)
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31. An example of Rdp estimation at 1.8 GeV
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32. Energy dependence of the ratio Rdp for elastic charge exchange process nppn at 0º in Lab
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33. Energy dependence of the ratio Rdp (F. Lehar. Private communication) B
Energy dependence of the ratio Rdp (F.Lehar. Private communication) B.Pagels, Diplomarbeit, Universitat Freiburg i. Br.,1988, unpublished
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34. Conclusion
New –ΔσL(np) results complete in the main the measurement of energy dependence at the Dubna Synchrophasotron region.
Measured –ΔσL(np) values are in accordance with the existing np results at low energies, obtained with free neutron beams. The rapid decrease of –ΔσL(np) values above 1.1 GeV was observed in the first data taking runs and is confirmed in the latest run and a minimum or a shoulder around 1.8 GeV is observed.
The necessity of more detailed and accurate –ΔσL(np) measurements around 1.8 GeV and new –ΔσT(np) data in the kinetic energy region above 1.1 GeV is emphasized.
The possibilities for A00kk(np), A00nn(np) and Rdp measurements, using prepared magnetic spectrometer, were demonstrated.
New results at θCM = π for Rdp = dσ/dΩ(nd) / dσ/dΩ(np) - the ratio of a quasi-elastic nd scattering differential cross section to the free np elastic scattering one at 1.0, 1.2, 1.8 and 2.0 GeV are presented.
We are grateful to the JINR, JINR VBLHE and DLNP Directorates for these investigations support. The investigations were supported in part by the Russian Foundation for Basic Research (Grant № 02–02–17129).
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