the pn -system study at internal anke experiment

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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


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


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


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


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


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


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


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%


Single polarised data: dσ/dq, Axx, Ayy

Td = 1.6 GeV

Td = 1.8 GeV

Td = 2.27 GeV

Large discrepancy


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


3coscos4

1

2cos12cos14

3

2cos12cos14

1cos

2

3

cos1

,,21

,21

,,21

,21

,,

0

*


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


3coscos4

1

2cos12cos14

3

2cos12cos14

1cos

2

3

cos1

,,21

,21

,,21

,21

,,

0

*


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


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


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


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


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

the pn -system study at internal anke experiment

Documents

pnsystem study

internal anke experiment

polarised deuterons

anke atomic beam source

ayy double polarised

gev dpppn

gev tn

polarised h gas