np Scattering Experiments at ANKE-COSY
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Transcript of np Scattering Experiments at ANKE-COSY
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September 1, 2009 | Andro Kacharava (JCHP/IKP, FZ-Jülich)
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np Scattering Experiments at ANKE-COSY
Forschungszentrum Jülich
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COSY (Cooler Synchrotron) at Jülich (Germany)
• Hadronic probes: protons, deuterons
• Polarization: beams & targets
Outline
• Introduction
• Experimental Program
• NN-Scattering Experiments
• Charge–Exchange Reaction
• Experimental Facility
• Selected Results
• Outlook
• Summary
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ANKE-COSY Program: An Overview
Goal:
Study of 3-body final states aiming to extract basic spin-dependent two-body scattering information
Tools:
NN scattering ↔ np amplitudes, nuclear forces
Meson production ↔ NN amplitudes (ChPT), FSI
Strangeness production ↔ YN interaction, OZI rule
Topics:
Status:
Towards the double polarization measurements ( dp - Nov’2009)
• Hadronic probes (p,d)• Double polarization (beam/target)
→→
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(1) NN – Interaction
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• All labs with appropriate facilities have a duty to help to extend the NN database
• Needed to understand the NN forces and to interpret the coupling to inelastic channels
• Characterization requires precise data for Phase Shift Analyses
• Thanks in large part to EDDA, there is a wealth of data for pp system
NN-Interaction (I): General remarks
EDDA
d/d
pp elastic database
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• Ramping mode (Ep < 2.5 GeV)
• Wide energy & angular range
• High precision, consistency
for pp (I=1)-system:
d/dPRL 78 (1997); EPJ A 22 (2004)
AN PRL 85 (2000); EPJ A 23 (2005)
A** PRL 90 (2003); PR C 71 (2005)
Full characterization of
elastic pp scattering (PWA)
No dibaryon signal
NN-Interaction (II): The EDDA Legacy
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Current experimental status
■ R. Arndt: 1. “Gross misconception within the
community that np amplitudes are known to a couple of GeV”
2. “np data above 800 MeV is a DESERT for experimentalists”
np system poorly known →ANKE is providing high-quality data in forward/backward region
Ayy
d/d
np forward
np charge-exchange
np forward
np charge exchange
NN-Interaction (III): np database
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d ↑ n
↑ p
↑ psp n
p
pDdp observables: d/d, T20, T22, Ay,y, ...
np observables: Ay, Ayy
d beam: up to 1.1 GeV np d target: up to 2.8 GeV pn
quasi-free
pd→psp (pn)→→dp→psp (np)→
np forward
d beam:
d target:
→
NN-Scattering (I): np elastic (small angle)
→ →
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dp observables: d/d, T20, T22, Ay,y, ...
np observables: Ay, Ayy
d beam: up to 1.1 GeV np d target: up to 2.8 GeV pn
quasi-free
→
np charge-exchange
d beam:
d target:
→
NN-Scattering (II): np elastic (large angle)
dp→(pp)1S0n
pd→(pp)1S0n
↓ p
n
d→
↑ n
↑ p
↑ psp
p→
D
→→
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In impulse approximation, the pd n {pp}
amplitude corresponding to the figure
M = <k,m1,m2,m3|f13eiq.r/2|d,m,m3>
k = pp relative momentum in final state.
q = momentum transfer from p to n.
Epp = excitation energy in final pp state.
np charge-exchange amplitudes in cm:
with basis vectors in terms of initial and final cm momenta p and p':
p p’
D.V.Bugg & C.W., Nucl.Phys.A467 (1987) 575
np-Scattering (I): Deuteron Charge-Exchange
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In collinearkinematics
over a range in t
;2/,31 2
3
4
qkSIkdtd
d qkS 2,
;
qkSR
2,
2[ ] ;2
1 22222
20 RIT ;23 2222
22 RIT
R.IC zz *, 2 IC xx *
, ;2 RIC yy *, ;2
2222
2220 ,,,, TTdtd
,2;222
20
22 ITI
cos3;2 *,
*, yxzyy ICIC
dp→(pp)1S0 n
→
,RδεβΙ 2222 2
np-Scattering (II): Deuteron Charge-Exchange
→
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Characteristics:
• Energy range:
0.045 – 2.8 GeV (p)
0.023 – 2.3 GeV (d)
• Max. momentum ~ 3.7 GeV/c
• Energy variation (ramping mode)
• Electron and Stochastic cooling
• Internal and external beams
• High polarization (p,d)
• Spin manipulation
COSY Facility
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PolarizedInternal Target
(PIT)
Spectator detector
Atomic BeamSource
Lamb-Shift Polarimeter
Silicon Telescope
SiliconTelescope
System
Spectator detection
Exp. Facility (I): ANKE detection system
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Main components of PIT:
• Atomic Beam Source (ABS)• H or D• H beam intensity (2 HFS) 8 ∙ 1016 atoms/s• Beam size at the IP σ = 2.85 ± 0.42 mm• Polarization for Hydrogen
PZ = 0.89 ± 0.01
PZ = -0.96 ± 0.01
• Lamb-Shift Polarimeter (LSP)• Storage Cell (SC) in target chamber
Exp. Facility (II): Polarized Internal Gas Target
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Selected Results from ANKE-COSY
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dp→{pp}S (00)+n→→
↓ p
n
d→
↑ n
↑ p
↑ psp
p→D Measurements:
• at Tn up to 1.15 GeV for np
(Td=1.6, 1,8, 2.3 GeV)
np-Scattering (II): Measurements at ANKE
Epp < 3 MeV
np system: different isospin channel
via Charge-Exchange deuteron breakup:
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dp → dp Pz, Pzz
np → dπ0 Pz
dp → 3Heπ0 Pzz
2cos12cos14
1
cos2
11,
*
0
xxyy
y
AA
AN
N
zz
z
P
PzP
zzP
yA
yyA xxA
→
→
→
Selected Results (I): Polarimetry reactions
Td =1.2 GeV (Tn=585 MeV)
Pz≈75% Pzz ≈60% with EDDA and LEP
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SAID
ANKE
(Tn = 585 MeV)
dp → dp
dp → 3Heπ0
np → dπ0
dp → (pp)n
D. Chiladze et al. Phys. Rev. STAB , 9 (2006) Depolarization less then 4%
ANKE ANKE
ANKE
Selected Results (II): Beam polarization
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Experiments at higher energies uses polarization export technique
Data has been taken at Td =1.6, 1.8, and 2.23 GeV
ResultResult
y I = -0.213 ± 0.005
y III = -0.216 ± 0.006
yy I = 0.057 ± 0.003
yy III = 0.059 ± 0.003
Time
II
I III
1.2 GeV 1.2 GeV
1.8 GeV
Energy rampingEnergy ramping y I = y III
yy I = yy III
Selected Results (III): Polarization export
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dp→{pp}1S0 n
→
2222
2220 ,,,, TTdqd
Axx (T22)
Td = 1170 MeV
Transition from deuteron to {pp}1S0:
pn np spin flip
np spin-dependent amplitudes:
Results:
• Method works at Tn = 585 MeV• Application to higher energies
• Td=1.6, 1.8, 2.23 GeV (in progress)
D.Chiladze et al. PLB 637, 170 (2006)
Ayy (T20)
Selected Results (IV): Analysing powers, Cross sec.
Tn = 585 MeV SAID np amplitudes
New !
D.Chiladze et al. EPJA,40, 23 (2009)
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dp→{pp}1S0 n
→
2222
2220 ,,,, TTdqd
Transition from deuteron to {pp}1S0:
pn np spin flip
np spin-dependent amplitudes:
Results at q=0:
Selected Results (V): Spin amplitudes
D.Chiladze et al. EPJA,40, 23 (2009)
t20 (q=0) = 0.37 ± 0.02 0,
03.061.0
2
22
0
0
20
20
t
t
SAID prediction = 0.58
Epp <1 Mev
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dp→{pp}1S0 n
→
2222
2220 ,,,, TTdqd
Axx (T22)
Td = 1170 MeV
Transition from deuteron to {pp}1S0:
pn np spin flip
np spin-dependent amplitudes:
Results:
• Method works at Tn = 585 MeV• Application to higher energies
• Td=1.6, 1.8, 2.23 GeV (in prog.)
Next step:
• Double polarized → Cy,y, Cx,x
=> relative phases
Cy,y
Cx,x
D.Chiladze et al. PLB 637, 170 (2006)
Ayy (T20)
dp → →
Selected Results (VI): Spin correlations
Production run for double polarization measurements: Nov.’2009
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Outlook: Double polarization
High target polarization Qy ~ 80%
by nuclear reaction np → dπ0
Online monitoring of ABS polarization
by Lamb-shift polarimeter
Silicon Tracking Telescope – as a tool
for Polarimetry operating with storage cell
L ≥2 x 1029 s-1cm-2 achieved at COSY
dp – test experiment at ANKE → →
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COSY - unique opportunities for hadron physics with polarized hadronic probes (beam & target)
Deuteron breakup reaction successfully used as a method to study np charge-exchange amplitudes - proof of principal is achieved !
The method suggests that measurements at higher energies will provide useful information in regions where the existing np database is far less reliable
ANKE equipment has been commissioned and it ready for extraction of spin correlation parameters
Use of inverse kinematics with a polarized proton incident on a polarized deuteron will extend study up to max. COSY energy 2.9 GeV
Summary
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The END
Thank you very much for your – attention –
Many thanks to the
organizers !
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Unpolarized np pn differential cross section:
As first approximation, consider data with Epp < 3 MeV; 1S0 dominance.
There are two form factors from the integral over the Fermi momenta:
S+ and S- are longitudinal (=0) and transverse ( = 1) form factors.
In terms of the wave functions of the deuteron S- and D-states, u and w,
and the 1S0 pp wave function k,
np-Scattering: Deuteron Charge-Exchange
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Define a ratio of form factors by
unpolarized intensity depends
only upon spin-flip amplitudes:
Terms can be separated by measuring with polarised beams/targets:
unpolarized cross section
d,p vector analysing powers
d tensor analysing powers
d-p vector spin correlations
d-p tensor spin correlation
np-Scattering: Deuteron Charge-Exchange
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79.10
0
15.086.10
0
(SAID)
(ANKE)
APTDSG 142(0)
DTAPTDSG 2142 (0)
DSG, DT, APT from SAID
27.0
Value from SAID WI00Error from R. Arndt SE-Solution
22
22
20002
002
T
T20 = 0.39 ± 0.04 (ANKE)
dp→(pp)1S0 n
→
Bugg, Wilkin, NP A467(1987) 575
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Features:– Three layers (double sided)
1st: 60 m2nd: 300 m3rd: 5 mm
– Ekin~2 MeV (60 MeV/c)– 800 Channels– Self-triggering– On-board electronics
– UHV compatible– Large Acceptance
• 10% per telescope• 30 mm from the beam
COSY-Hardware (III): Silicon Tracking Telescope
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Future plans: Experiments with polarized probes
COSY proposal #152 ArXiv:nucl-ex/0511028