the pn -system study at internal anke experiment
DESCRIPTION
HEPI, Tbilisi State University IKP, Forschungszentrum Jülich. The pn -system Study at Internal ANKE Experiment. David Mchedlishvili. GGSWBS’12. Outline:. Motivation dp →( pp ) s n reaction Experimental setup Single polarised Double polarised Results Cross section - PowerPoint PPT PresentationTRANSCRIPT
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TSUTBILISI STATE UNIVERSITY
The pn-system Study at Internal ANKE Experiment
HEPI, Tbilisi State University
IKP, Forschungszentrum Jülich
David Mchedlishvili
GGSWBS’12
August 6, 2012 The pn-system Study at Internal ANKE Experiment GGSWBS’12
Outline:
o Motivation
o dp→(pp)sn reaction
o Experimental setup
• Single polarised
• Double polarised
o Results
• Cross section
• Tensor analysing powers
• Spin correlation parameters
• First results on ∆ channel
o Overview of the future experiment
o Summary and outlook
August 6, 2012 The pn-system Study at Internal ANKE Experiment GGSWBS’12
np Scattering data
d/d
Ayy
Current experimental status of np data
np forward
np charge-exchange
np charge-exchange
np forward
ANKErange
ANKErange
ANKE is able to improve np database by providing a precise data at up to 2.9 GeV/A
August 6, 2012 The pn-system Study at Internal ANKE Experiment GGSWBS’12
np charge-exchange (large angles)
↓p
n
d→
↑n
↑p
↑psp
p→D
dp→(pp)1S0n
→→
At small excitation energies in the final pp system 1S0 state
Spin-flip from 3S1,3D1 of the deuteron to 1S0 of the diproton. Data sensitive to spin-flip, isospin-flip transitions.
np charge-exchange amplitudes in cm
with basis vectors in terms of initial and final cm momenta p and p':
))(())(())(()( llmmnnnif pnpnpnpnnp
pp
ppl,
pp
ppm,
pp
ppn
D.V.Bugg & C.W., Nucl.Phys.A467 (1987) 575
August 6, 2012 The pn-system Study at Internal ANKE Experiment GGSWBS’12
Proof of principle at 1.17 GeV
D.Chiladze et al. PLB 637, 170 (2006)
D.Chiladze et al. EPJA,40, 23 (2009)
Results:
• Method works at Tn = 585 MeV
• Application to higher energies Td=1.6, 1.8, 2.27 GeV
Tn = 585 MeV SAID np amplitudes
August 6, 2012 The pn-system Study at Internal ANKE Experiment GGSWBS’12
Experimental setup
Single polarised:
• Beam: Polarised deuterons at Td=1.2, 1.6, 1.8, 2.27 GeV
• Target: Unpolarised hydrogen cluster target
• Objectives: dσ/dq, Axx, Ayy
Double polarised:
• Beam: Polarised deuterons at Td=1.2, 2.27 GeV
• Target: Polarised ABS cell target
• Objectives: Ayp, Cx,x, Cy,y
t
Higher Energy
1.2 GeV
August 6, 2012 The pn-system Study at Internal ANKE Experiment GGSWBS’12
Polarised internal gas target at ANKE
• Atomic Beam Source (ABS) provided polarised H gas in the cell Qy = 0, -1, +1.
Density ≈ 1013 cm-2
• Cell: 20 x 15 x 370 mm3
• Lamb-shift Polarimetry
Complications due to cell:• Dedicated beam development involving
stacking injections and electron cooling
• Background handling
August 6, 2012 The pn-system Study at Internal ANKE Experiment GGSWBS’12
Reaction identification at 1.2 GeV
dp→(pp)n and np→dπ0 reactions provide double track events in forward detector:
• pp from dp→(pp)n
• dpsp from quasi-free np→dπ0
∆ttof [ns]
∆t m
ea
s [n
s]Fast pp pairs are distinguished from dpsp using time of flight method
August 6, 2012 The pn-system Study at Internal ANKE Experiment GGSWBS’12
Beam polarimetry
Beam polarisation is measured at Td = 1.2 GeV and “polarisation export” technique is applied to higher energies
•np→dπ0 Pz (SAID Ay for pp→dπ+)
•dp→(pp)sn Pzz (Axx, Ayy from previous ANKE measurements)
))2cos1)(()2cos1)(((4
11
),(
),(
qAqAPqN
qNyyxxzz
unpol
pol
Normalised count ratio of dp→(pp)sn events for low excited pp pairs (Epp< 3 MeV):→
Normalised count ratio of np→dπ0 events:→
cos)(1),(
),( pyz
unpol
pol APN
N
→
→
Pz up to 70%
Pzz up to 80%
August 6, 2012 The pn-system Study at Internal ANKE Experiment GGSWBS’12
Single polarised data: dσ/dq, Axx, Ayy
Td = 1.6 GeV
Td = 1.8 GeV
Td = 2.27 GeV
Large discrepancy
August 6, 2012 The pn-system Study at Internal ANKE Experiment GGSWBS’12
Double polarised data
•
• Epp < 3 MeV
dp→(pp)1S0n
→→
3coscos4
1
2cos12cos14
3
2cos12cos14
1cos
2
3
cos1
,,21
,21
,,21
,21
,,
0
*
xxyyyyyxxxxyyyyyxxyzz
xxyyyz
xxyyzzdyz
pyy
CCCCCCQP
CCQP
AAPAP
AQN
N
August 6, 2012 The pn-system Study at Internal ANKE Experiment GGSWBS’12
3coscos4
1
2cos12cos14
3
2cos12cos14
1cos
2
3
cos1
,,21
,21
,,21
,21
,,
0
*
xxyyyyyxxxxyyyyyxxyzz
xxyyyz
xxyyzzdyz
pyy
CCCCCCQP
CCQP
AAPAP
AQN
N
Double polarised data: Ayp
•
• Epp < 3 MeV
• With beam statePz = 0; Pzz = 0.
dp→(pp)1S0n
→→Td = 1.2 GeV
Td = 2.27 GeV
August 6, 2012 The pn-system Study at Internal ANKE Experiment GGSWBS’12
3coscos4
1
2cos12cos14
3
2cos12cos14
1cos
2
3
cos1
,,21
,21
,,21
,21
,,
0
*
xxyyyyyxxxxyyyyyxxyzz
xxyyyz
xxyyzzdyz
pyy
CCCCCCQP
CCQP
AAPAP
AQN
N
Double polarised data: Cy,y Cx,x
•
• Epp < 3 MeV
• With beam state Pzz = 0; (Ap
y, Ady = 0)
dp→(pp)1S0n
→→Td = 1.2 GeV
Td = 2.27 GeV
August 6, 2012 The pn-system Study at Internal ANKE Experiment GGSWBS’12
Epp<3 MeVTd = 1.6 GeV
Td = 1.8 GeV
Td = 2.27 GeV
dp→(pp)s∆0 reaction
• Td=1.2GeV• Td=2.27GeV
dp→(pp)n
Main mechanism:
One pion exchange
dp→(pp)∆0 + ???
Valuable information on the modelling of the np→p∆0 amplitudes
August 6, 2012 The pn-system Study at Internal ANKE Experiment GGSWBS’12
Tensor analysing powers
High mass region: 1.19 < MX < 1.35 GeV/c2
Differences:
Signs are flipped
Axx and Ayy are small at qt=0
Valuable constraints on the
modeling of the np→p∆0 amplitudes
dp→(pp)sn at Td = 1.2 GeV→
dp→(pp)s∆0
COMPARE!Td = 1.6 GeV
Td = 1.8 GeV
Td = 2.27 GeV
August 6, 2012 The pn-system Study at Internal ANKE Experiment GGSWBS’12
Future experiments
Measurement of nucleon-nucleon elastic scattering at small angles up to the maximum COSY energy
Byproducts:
• pd→(pp)sn: two slow protons detected in the STT
• pd→pd: the deuteron is detected in an STT (small angles) or in ANKE
(large angles)
• pd→(pp)s∆0 : two protons detected in the STT and ∆0 decay products
possibly detected in ANKE
• pd→pspdX (quasi free pn→dX): fast deuteron
detected in ANKE
• pd→psp{pp}s π‾ : two fast protons detected in ANKE
• pd→3He π0 : the 3He is detected in ANKE
August 6, 2012 The pn-system Study at Internal ANKE Experiment GGSWBS’12
Outlook
Further investigation of the dp→(pp)s∆0 reaction by using double
polarised data
Extension of the np program at ANKE by using proton beams at COSY
Summary
dp→(pp)sn observables:
1. dσ/dq, Axx, Ayy at Td = 1.2, 1.6, 1.8, 2.27 GeV
2. Ayp, Cx,x, Cy,y at Td = 1.2, 2.27 GeV
dp→(pp)s∆0 observables:
dσ/dm, Axx, Ayy at Td = 1.6, 1.8, 2.27 GeVTHANK YOU