September 1, 2009 | Andro Kacharava (JCHP/IKP, FZ-Jülich)

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np Scattering Experiments at ANKE-COSY

Forschungszentrum Jülich

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

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)

→→

(1) NN – Interaction

• 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

• 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

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

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)

→ →

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

→→

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

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

→

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

PolarizedInternal Target

(PIT)

Spectator detector

Atomic BeamSource

Lamb-Shift Polarimeter

Silicon Telescope

SiliconTelescope

System

Spectator detection

Exp. Facility (I): ANKE detection system

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

Selected Results from ANKE-COSY

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:

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

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

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

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)

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

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

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 → →

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

The END

Thank you very much for your – attention –

Many thanks to the

organizers !

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

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

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

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

Future plans: Experiments with polarized probes

COSY proposal #152 ArXiv:nucl-ex/0511028