Measurements of Energy Behaviours of Spin-Dependent np Observables over a GeV Region

1
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
?sL(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. Measurement
s 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.
2
Plan of Talk

• Introduction. Aims of the "Delta-Sigma"
  experiment. Program, Tools, Participants.
• Determination of ?sL,T(np) Observables and Method
  of Measurements.
• Experimental Set-Up for the ?sL,T(np)
  Measurements.
• Parameters of Detectors and Neutron Beam and
  Results of stot(np) and stot(nC) Measurements.
• The ?sL(np) and ?sL(I0) 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.

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.

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) ?sL(np) and ?sT(np) the total cross section
  differences for parallel and antiparallel
  directions of beam and target polarizations, with
  energy steps of 100200 MeV and expected
  statistical errors of 1 mb
• The observables ?sL(np) and ?sT(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
  ?sL,T(np) measurements) spin-correlation
  parameters A00kk(np) (together with ?sL(np)) and
  A00nn(np) (together with ?sT(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.

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
  Rdpds/dO(nd) / ds/dO(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 ?sL,T(np), A00kk(np),
  A00nn(np) and Rdp will be obtained for the first
  time over the energy range of neutron beam of
  1.23.7 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.

6
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 0.70.8
• CRYOGENIC HYDROGEN-H2 AND DEUTERIUM-D2
  TARGETS (L30 cm)
• DELTA-SIGMA SET-UP
• TRANSMISSION NEUTRON DETECTORS

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

8
Determination of ?sL,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)
• stot s0tot s1tot (PB PT)
  s2tot (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 s0tot is the spin-independent total
  cross section, and s1tot and s2tot are the
  spin-dependent contributions which connect with
  the observables ?sT and ?sL by the relations
• ?sT 2 s1tot stot (??) stot
  (??)/PB PT, (2)
• ?sL 2 (s1tot s2tot) stot
  (??) stot (??)/PB PT. (3)
• Values of s0tot, ?sT and ?sL are connected with
  the imaginary parts of three invariant forward
  scattering amplitudes a b, c and d via three
  optical theorems
• s0tot (2p/K) Im a(0)
  b(0), (4)
• ?sT (4p/K) Im c(0) d(0),
  (5)
• ?sL (4p/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
• ?sL,T (np) ½?sL,T (I0) ½?sL,T
  (I1), (7)
• ?sL,T (pp) ?sL,T (nn) ?sL,T
  (I1), (8)
• ?sL,T (I0) 2 ?sL,T (np) ?sL,T
  (pp). (9)
• Using the last equation, one can obtain values of
  ?sL,T (I0) from known quantities of ?sL,T (np)
  and ?sL,T (pp), measured at the same energy.

9
Method of the ?sL,T (np) Measurements

• The trasmission method is used to measure the
  total cross section differences ?sL,T (np).
• N M exp s(O) nx, s(O)
  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
  O, and nx is the thickness of target in cm2.
  Unpolarized total cross section stot can be
  obtained by extrapolation of O? 0.
• Using expression (1), the corresponding equations
  can be obtained for ?sL,T with different
  orientation of beam and target polarizations. For
  example
• ?sT (PT) 2 s1tot 2stot
  (??) stot (??)/ (PB PB) PT. (11)
• Finally, for both signs of target polarization
• ?sL,T ½( ?sL,T (PT)
  ?sL,T (PT)),
  (12)
• where
• ?sL,T (O, PT) Ln R(PT) / PB
  PT nHx,
  (13)
• PB ½(PB PB),
  (14)
• R (N/M) / (N/M) .
  
  (15)
• Statistical uncertainty is
• d(?sL,T)stat v(1/M 1/N
  1/M 1/N) / PBPTnHx. (16)

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

11

• 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

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 cm88
  cm2.
• Neutron beam is formed by a set of collimators
  C1C4.
• 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 2106 n/cycle.
• For the ?sL measurements, the neutron spins are
  rotated from vertical direction to the direction
  of beam momentum by spin rotating magnet SRM.

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Systematic Errors

• For the measured ?sL 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 lt 0.04 mb

16
Energy Dependence of the ?sL (np) Observable
Obtained with Free Neutron Polarized Beams
17
Energy Dependence of the ?sL (I0)
18

• Measurements of the ?sL (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
  ?sL (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
  377-96 (1996) 13.
• V.I.Sharov, S.A.Zaporozhets, B.P.Adiasevich,
  N.G.Anischenko et al. JINR Rapid Communications
  496-99 (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) 79-90.

19

• Measurements of the ?sL,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-gtpn charge exchange process are
  carried out using high intensity unpolarized
  neutron beams and cryogenic H2 and D2 targets
  (l34 cm). The first results of these
  measurements will be presented below.

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)
• ds/dO (p) ½a2 b2 c2
  d2, (17)
• ds/dO A00nn(p) ½a2 b2
  c2 d2, (18)
• ds/dO A00kk(p) Re a d Re b
  c. (19)
• These equations can be transformed to
• ds/dO (1 A00kk) b c2 A
  (Re b Re c)2, (20)
• ds/dO (1 A00kk 2A00nn) b
  c2 B (Re b Re c)2, (21)
• ds/dO (1 A00kk 2A00nn) b c
  2d2
• 
  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.

21

• Experimental observable
• Rdp ds/dO(nd) / ds/dO(np)
  (23)
• is the ratio of a quasi-elastic nd
  scattering differential cross section to the free
  np elastic scattering one. At ?CM p
  (F.Lehar. Private communication)
• Rdp (p) (2/3) ds/dOSD ( np) /
  ds/dO(np), (24)
• Rdp (p) (2/3) 0.25 a - b2
  0.5 ( c2 - d2 ) /
• 0.5 (
  a2 b2 c2 d2 ),
  (25)
• where ds/dOSD ( 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.

22
Magnetic Spectrometer for Detection of Protons
from np?pn Charge Exchange Process
23
Detected Events Distribution in the ? vs f Plane
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Separation of the p and d Particlesin the TOF vs
Momentum Plane
28
Estimation of ds/dO for quasi-elastic np
scattering on D2 target at 1.8 GeV
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Energy dependences of differential cross sections
of elasticnp?pn charge exchange at 0 CM
(F.Lehar. Private communication)
31
An example of Rdp estimation at 1.8 GeV
32
Energy dependence of the ratio Rdp for elastic
charge exchange process np?pn at 0º in Lab
33
Energy dependence of the ratio Rdp(F.Lehar.
Private communication)B.Pagels, Diplomarbeit,
Universitat Freiburg i. Br.,1988, unpublished
34
Conclusion

• New ?sL(np) results complete in the main the
  measurement of energy dependence at the Dubna
  Synchrophasotron region.
• Measured ?sL(np) values are in accordance with
  the existing np results at low energies, obtained
  with free neutron beams. The rapid decrease of
  ?sL(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
  ?sL(np) measurements around 1.8 GeV and new
  ?sT(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 ?CM p for Rdp ds/dO(nd) /
  ds/dO(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 ?
  020217129).