1. Deuteron Polarimetry at COSY
David Chiladze
IHEPI, Tbilisi State University
IKP, Forschungszentrum Jülich

2. Outline Introduction Experimental tools Beam polarimetry
Summary & outlook
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3. Introduction: NN Scattering
Characterization requires precise data for Phase Shift Analyses
Current experimental status of NN data:
pp system (I=1) well-known up to 2.5 GeV (EDDA): Majority of data on unpolarized, single, and double polarized observables
np system (I=0) poorly known → ANKE will provide high-quality data in forward/backward region
np charge-exchange
ANKE
range
d/d
np forward
np charge-exchange
ANKE
range
Ayy
The complete description of the NN interaction requires precise data as input to Phase Shift Analyses (PSA), from which the scattering amplitudes can be reconstructed.
The PSA generally requires many independent observables and without polarisation experiments it cannot be done.
Many of such experiments has been carried out for the pp system and as an example, well-known EDDA experiment at COSY has produced: Majority of the data on unpolarized, single, and double polarized observables, which made large impact and allowed significantly reduce the ambiguities in phase shifts.
In contrast to the pp system the np system is poorly known and the current experimental status on np data one can see from the figures, np elastic data-base is practically empty above 1 GeV, especially for double-polarized observables.
We propose to improve significantly our knowledge of the np elastic scattering by measuring cross sections, analysing powers, and
spin-correlation coefficients in both forward and backward directions using the deuteron as a source of quasi-free neutrons.
np forward
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4. Introduction: Motivation
Double polarized experiments at ANKE
np spin physics
Single polarized experiment
Polarized charge-exchange reaction dp→(2p)n
Direct reconstruction of the spin-dependent np amplitudes via measurement of and T20 & T22 (Tn = 0.6 – 1.15 GeV)
Aim of first measurement (Td = 1.2 GeV)
Feasibility of the experiment
Polarimetry standards at ANKE
(Proposal #152, “Spin physics from COSY to FAIR”) →
At present, the instrumentation development at ANKE-COSY are in the phase, when we are approaching the goal to start the double-polarized experiments.
One of the challenging subject of the double-polarized programme at ANKE is the np spin physics. the data base of spin-observables in np scattering is very incomplete above 800 MeV.
As a first step in this direction, we propose to study the polarized CE reaction. It's known that information on the spin-dependent np elastic amplitudes can be obtained by measuring the Charge-Exchange break-up of polarized deuterons on hydrogen. By the measurement of the differential cross section and tensor analyzing powers we get the access to the spin-dependent np amplitudes.
In order to show feasibility of this study and to develop polarimetry standard at ANKE, we did the test measurement with polarized deuteron beam. The results of this experiment I am going to show.
For several years COSY has provided circulating beams of polarized protons. Used together with a polarized hydrogen target, these beams have been successfully exploited by the EDDA collaboration to measure Unpolarized cross sections and different spin observables up to maximum proton energy available at COSY. With those measurements EDDA has clarified the spin dependence of pp scattering amplitudes. In the other hand,
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5. Experimental tools: COSY
Polarized and unpolarized proton and deuteron source
Protons up to 2.88 GeV
Deuterons up to 2.23 GeV
Internal and external experiments
ANKE
EDDA
LEP
COSY is a cooler synchrotron which has a source for polarized and unpolarazed prototons and deuterons. It can accelerate and store protons up to 2.88 GeV and deuterons up to 2.23 GeV both for internal and external experiments. To assist the polarizations of the beam inside a COSY a LEP is used. In case of protons an extensive number of successful measurements with polarized beams and targets was done with the internal EDDA detector. It can be used as a polarimeter which determine the polarization of the beam with high precision. COSY is going a program with polarised deuteron beam and polarised deuterone storage cell targets at the ANKE spectrometer placed at an internal target station at cosy ring. DEuterons don’t have to cross any depoarization ressonanses during the acceleration but therefore it is important to chack that we don’t have the depolarization of the beam at COSY. for this we measured polarization with LEP EDDA and ANKE for three different energies simultaniosly I will discribe them separatly
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6. Experimental tools: LEP & EDDA
Spin mode
Pz ideal
Pzz ideal
Intensity [I0] 1
-2/3 2
+1/3 +1 3
-1/3 -1 4
+1/2
-1/2
2/3 5 6 7
dC → dC
Td = 75.6 MeV
Ay(40°) = 0.61 ± 0.04 →
L E P
S.Kato et al.
Nucl.Inst.Meth. A 238, 453 (1985)
E.J. Stephenson
Deuteron　Polarimeter for EDM Search.
Pz ≈ 75 % Pzz ≈ 60 %
Slope = 1.05 ± 0.06
Offset = 0.04 ± 0.01
dp → dp
Td = 270 MeV
Ay, Ayy (65° – 95°)c.m. →
E D D A
During the experiment source was arranged so that it provides eight different states of the beam including one unpolarised and seven different combination of vector and tensor polarization. the values of the ideal polarisation and relative intesities are listed in the table. To assist the polarisation of the beam the LEP was used. It uses dC elastic scatering on injection energy. the studies of cross section and analysing powers and resulting figur of merit suggests that polarimeter should work best for 40 degree angles. unfortunatly the tensor analysing power is verys mall so LEP is sensible only for vector polarisation
EDDA uses dp elastic scatering for polarimeter. we used td 270 MeV energy where precise value of analysing powers are known. and after we compare vector polarisation measurements of EDDA and LEP and the result is shown in the figure. the
K. Sekiguchi et al.
Phys.Rev. C 65, (2002)
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7. Experimental tools: ANKE setup
Td = 1170 MeV
dp → dp
dp → 3Heπ0
dp → dpsp π0
dp → (pp)n → → → →
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8. Beam polarimetry: Reaction identification
dp → dp
dp → 3Heπ0
mπ0
dp → dpsp π0
dp → (pp)n
Low branch
High branch
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9. Beam polarimetry: Ay, Ayy measurement
dp → dp
ANKE
ANKE
dp → 3Heπ0
np → dπ0
dp → (pp)n
SAID
(Tn = 585 MeV)
ANKE
ANKE
Depolarization less then 4%
D. Chiladze et al. Phys. Rev. STAB 9, (2006)
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10. Beam polarimetry: CE reaction
D.Chiladze et al. Phys. Let. B 637, 170 (2006) →
dp→(pp)1S0 n
Axx (T22)
Transition from deuteron to (pp)1S0: pn  np spin flip
Obtain np elementary spin-dependent amplitudes:
Results:
Method works at Tn = 585 MeV
Application to “uncharted territory”
Next step:
Double polarized → Cy,y, Cx,x (using PIT see talk K. Grigoriev)
Td = 1170 MeV
Ayy (T20) 2 22 20 , e d b g s + Þ T dq
Cy,y
Cx,x
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11. Beam polarimetry: Polarization export
Polarized deuteron beam at 3 energies
Calibration of the beam polarization of arbitrary energy
Super cycle: Td = 1.2 GeV, 1.8 GeV. II I
III
1.2 GeV
1.8 GeV
Energy ramping
ey I = ey III
eyy I = eyy III
Results
ey I = ±
ey III = ±
eyy I = ±
eyy III = ±
Time
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12. Polarisation standard at 1.2 GeV Analysing power measurement
Summary & Outlook
Polarisation standard at 1.2 GeV
Analysing power measurement
Polarisation export technique
Higher beam energy (up to 2.3 GeV)
Double polarized dp→(2p)n reaction → →
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13. PzEDDA = (0.95±0.02)PzLEP + (0.04±0.01) LEP (Td = 76 MeV)
dC → dC
EDDA (Td = 270 MeV)
dp → dp
ANKE (Td = 1170 MeV)
dp → 3Heπ0
dp → dpsp π0
dp → (pp)n
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14. Experimental facility
LEP (Td = 76 MeV)
EDDA (Td = 270 MeV)
ANKE (Td = 1170 MeV)
ANKE
EDDA
LEP
Spin mode
Pz ideal
Pzz ideal
Intensity [I0] 1
-2/3 2
+1/3 +1 3
-1/3 -1 4
+1/2
-1/2
2/3 5 6 7
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15. Introduction: np elastic (small angle)
np forward
dp→psp (np) →
deuteron beam: → p
pd→psp (pn) →
deuteron target: → d
↑ n → p
d beam: up to 1.1 GeV for np
d target: up to 2.8 GeV for pn D
↑ p
dp observables: d/d, T20, T22, Ay,y, ...
↑ psp n
How can we realize this program at ANKE ?
This picture shows the schematic view of dp or pd break-up reaction in a single-scattering approximation.
As we see, there are two possibilities to study quasi-elastic np scattering at ANKE:
with the deuteron beam or deuteron target, which makes a difference in spectator particle detection: in case of deuteron beam it is a fast proton and in the case of deuteron target - slow proton (typically few MeV).
With these break-up reactions, we will focus on the quasi-free np elastic scattering at forward c.m. angles;
quasi-free
np observables: Ay, Ayy
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16. Introduction: np elastic (large angle)
np charge-exchange
dp→(pp)1S0n →
deuteron beam: n
pd→(pp)1S0n →
deuteron target: → d
↑ n → p
d beam: up to 1.1 GeV for np
d target: up to 2.8 GeV for pn D
↑ p
dp observables: d/d, T20, T22, Ay,y, ...
↑ psp
↓ p
While exploiting deuteron charge-exchange break-up, or quasi-free np elastic scattering at backward angles, we will gain additional info about the final-state polarization.
In this case the reaction provides a spin filter that selects an np charge-exchange spin-flip from the deuteron states
to the 1S_0 state of the diproton.
Though in both configurations there are deuteron corrections, these can be largely handled and has already been shown at other laboratories (for example at SACLAY) to work well.
and our preliminary results shows, that the suggested method to extract np observables from the dp, in quasi-free approximation works well !
By using a deuterium target the beam energy range could be extended up to about 2.8 GeV.
quasi-free
np observables: Ay, Ayy, Dyy, Axy,y, ...
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