spin physics at anke-cosytheor.jinr.ru/~spin2012/talks/plenary/dymov.pdfnn interaction properties at...

September 21st 2012,

Sergey Dymov, JINR, FZ Juelich

for the ANKE collaboration

SPIN 2012, Dubna

Spin Physics at ANKE-COSY

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S. Dymov Spin Physics at ANKE-COSY 2

Contents

Experimental facility• COSY in Juelich• ANKE @ COSY

Experiments with polarized beam and target at ANKE• NN interaction properties at small momentum transfers• nuclear structure, short range NN interactions • η meson properties• NN→NNπ near threshold (χPT) and in Δ region

Future program

Summary


• 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

Hadronic probes: protons, deuterons

Polarization: beam and targets

COSY (COoler SYnchrotron) at Jülich (Germany)


Beam quality: without cooling: ∆p/p ~ 1·10-3 electron cooling: ∆p/p ≤ 5·10-5 pp1.5 GeV/c

Beam intensities: protons, unpolarized: 2·1010 (cooled) protons, polarized: 7·109 (cooled) deuterons, unpolarized: 5·1010 (cooled) deuterons, polarized: 1·1010 (cooled)

COSY – Beam parameters


ANKE

TOF

WASA

COSY – Experimental Facilities

Hadron physics with hadronic probes

Experimental set-ups:

ANKE WASA EDM (BNL/JEDI) PAX

TOF (ext.)

PAX

EDM

… the machine forhadron spin physics


ANKE@COSY

The ANKE spectrometer at internal targetposition of COSY allows measurement of:

• Fast forward positive and negative ejectiles in Forward, Positive and Negative detectors (FD, PD, ND): momentum, Id by TOF, dE/dX

• Slow positive ejectiles in Vertex detector (STT): energy, tracking, Id by dE/dX

Targets available:• Cluster jet H2 and D2• Internal polarized (H, D) target (PIT) with a storage cell

STT


Polarized Internal Target (PIT):

Polarised H (D) gas (ABS) in the cell Qy = 0, -1, +1

Density ~1013 cm-2

Storage cell: 20 x 15 x 390 mm3

Lamb-shift Polarimeter

Polarized Internal Target (PIT):

Polarised H (D) gas (ABS) in the cell Qy = 0, -1, +1

Density ~1013 cm-2

Storage cell: 20 x 15 x 390 mm3

Lamb-shift Polarimeter

PIT at ANKE

COSY beamCOSY beam


η meson properties:• study of FSI in the near-threshold dp→3He η with polarized d beam• presize η-mass determination by missing-mass method

NN interaction properties at small momentum transfers:• small angle pp, np-elastic scattering

• charge-exchange (CE) deuteron break-up reaction

Short range NN interactions:• deuteron break-up reaction at large momentum transfer• pp→{pp}sπ

0 in Δ (1232) region

χPT development for NN→NNπ:• near-threshold pp→{pp}sπ

0 and pn→{pp}sπ-

Experiments with polarized beam and target at ANKE

Diproton production

Internal Experiments at COSY Folie 9

GEM: pd → 3Heη

SATURNE: pd → 3Heη

NA48: π− p → η n

MAMI: γ p → η p

KLOE: φ → η γ

CLEO: Ψ(2s) → η J/ψ

GEM: pd → 3Heη

SATURNE: pd → 3Heη

NA48: π− p → η n

MAMI: γ p → η p

KLOE: φ → η γ

CLEO: Ψ(2s) → η J/ψ

COSY/ANKE: d+p→3He+ηMethod: precise determination of production threshold !

COSY/ANKE: d+p→3He+ηMethod: precise determination of production threshold !

Precision data – but inconsistency w/ new data !?

Precision data – but inconsistency w/ new data !?

dBarrier bucket

New technique !

New technique !

RF solenoid EDDA

RF-induced spin-resonance

PLB 619 (2005) 281

0

1 1 resf

G fγ

= × − ÷

COSY: Determination of η-mass via 2-body reaction

Phys. Rev. ST-AB, 13, 022803 (2010)


Determination of η-mass via 2-body reaction

Near threshold: Final state momentum is very sensitive to the η-mass !

Dependence: pf = pf ( pd, mη )

Needed accuracy: ∆pd / pd < 10 -4

The goal:

Accurace of the η-mass: ∆m η < 50 keV/c2

Final state momentum of 3He-nuclei: ∆pf = 400 keV/c

Beam momentum: ∆pd = 300 keV/c

Result: m(η)=(547.873 +- 0.005(stat) +- 0.027(syst)) MeV/c2Compatible with the decay measurements. Phys. Rev. D 85, 112011 (2012).


Diproton reactions at ANKE

S wave: Isotropy in {pp} - rest frame pp Final State Interaction (Migdal-Watson FSI factor)

Excitation energy resolution Example: pp→{pp}sγ at 500 MeV

Deuteron: bound (p+n) system, very well studied Diproton: free {pp}-pair in 1S0 state, Epp < 3 MeV

New tool to study hadron interactions

Two nucleon systems:


d-breakup at high momentum transfer

pd dynamics at high momentum transfer– pd {pp}s (00) + n– Kinematics like pd backward elastic

→ Same ∆+ONE+SS modelkey to T20 problem in pd dp

– internal deuteron momentum for ONE 0.35 - 0.6 GeV/c– S-wave pp-pairs

→ Suppression of ∆ → Dominance of ONE→ NN-potential at short distance

– Next: – Analyzing power T20 ,

obtained parasitically from the CE data at 1.2, 1.6, 1..8 GeV

S.Yaschenko et al., PRL 94 (2005) 072304

V. Komarov et al., PL B 553 (2003) 179


dp observables: dσ/dΩ, T20, T22, Cy,y,

np observables: Ay, Ayy, Dyy, Cxy,y,

quasi-free

dp→{pp}S (00)+n

pd→{pp}S(1800)+n

↓ p

n

d→

↑ n

↑ p

↑ psp

p→D

deuteron beam:

deuteron target:

np system: different isospin channel

via Charge-Exchange deuteron breakup:

Charge-exchange d-breakup (1)

Epp < 3 MeVEpp < 3 MeV Transition from d → (pp)1S0: pn → np spin flip

np spin-dependent amplitudes:

•

22222220 ,,,, εδβγ

σ +⇒TTdqd


Axx (T22)

Td = 1.2 GeV

Ayy (T20)

Tn = 600 MeV⇒ SAID np amplitudes

Deuteron breakup: dp {pp}s n (polarized beam)

Data for Td = 1.2 GeV – Proof of Method !

np-data published in – EPJA ,40, 2009

theory – David Bugg & Colin Wilkin NPA, 467, 1987



New!

Td = 1.6 GeV

New!

Td = 1.8 GeV

Td = 2.3 GeV

New!


Data for Td = 1.6, 1.8, 2.3 GeVNew: measurement of Axx, Ayy

np pn (CEX-amplitudes)Next step: p-beam



Td = 1.8 GeV

Td = 1.6 GeV

New!

New!

Td = 2.3 GeV

New!

P R E L

I M I N

A R Y


Data for Td = 1.6, 1.8, 2.3 GeV New: measurement of dσ/dq

np pn (CEX-amplitudes)Next step: p-beam



During this time:Change of target-polarization

(+,-) every 5 sec

Deuteron breakup: dp {pp}s n (polarized beam and target)

First double polarized measurement at ANKE

E1 E2

(COSY-Supercycle)

Acceleration

15 min

45 min

Stacking Injection (~100x)

(Electron cooling on)

Measurement cycle

Beam

current

New! Td = 1.2 GeV

Cy,y

Cx,x



New!

∆0

New!

n

n ∆0Deuteron breakup: dp {pp}s ∆0 (polarized) np p∆0

first measurement (at 2.3 GeV)! significant differences (∆0 and n):

- relative sign of A´s interchanged- A´s ~ 0 for low momentum transfer

Td = 2.3 GeV

dp {pp}s+X



Future NN interaction program at ANKE: pp scattering

• Description of nucleon-nucleon interaction requires precise data for Phase Shift Analysis

• COSY-EDDA collaboration produced wealth of data forpp elastic scattering.

• There are no experimental data at low angles (θcm


R. Arndt: “Gross misconception within the community that np amplitudes are known up to a couple of GeV. np data above 800 MeV is a DESERT for experimentalists.”

Ay (np)

dσ /dΩ (np)

ANKE

np forward

np charge-exchange

ANKE

np forward

np charge-exchange

ANKE is able to provide the experimental data both for

pp and np systems and improve our understanding of NN interaction

Future NN interaction program at ANKE: np scattering


• Theoretical description of pN→pp π process is considerably simplified if two final protons are detected at low excitation energy, i.e. such di-protons are predominantly in the 1S0 state.

• Spin structure of the pn→{pp}sπ-- (or pp→{pp}sπ

0 ) is ½+½+→0+0- only two spin amplitudes (compared to 6 for pp→dπ+)

Near-threshold pion production at ANKE (1)


Near-threshold pion production at ANKE (2)

Extension of ChPT to the NN→NNπ process

A full data set of all observables in pp → {pp}sπ0 and np → {pp}sπ− would allow us to determine the partial wave amplitudes and test the ChPT predictions.

pp → {pp}sπ0 includes 3P0 → 1S0 s, 3P2 → 1S0 d and 3F2 → 1S0 d (Ps, Pd and Fd)np → {pp}sπ−− adds 3S1 → 1S0 p and 3D1 → 1S0 p (Sp and Dp)

The p-wave amplitudes give access to the 4Nπ contact operator, controlled by the low energy constant d.

3Nscattering

NN NNπ

LEC d connects different low-energy reactions: pp→de+ν, pd→pd, γd→nnπ+

Our goal is to establish that the same LEC controls NN→NNπ


Accessing LEC d via Ax,x and dσ/dΩ The direct and most clean way to access the LEC d is to measure the cross section and the spin correlation coefficient Ax, x in np → {pp}sπ−−:

(1-Ax,x)dσ/dΩ ~ |δ|2k2 sin2θ, Ay,y=1

where δ is one of the p-wave amplitudes, containing the 4Nπ contact termOnly one factor (1-Ax, x)dσ/dΩ(90

0) has to be extracted from the measurement.

The method does require subtraction of data with different systematic errors.

ChPT calculation by FZJuelich IKP theory, no dwaves included (V.Baru et al)


Experimental program at ANKE

pN→{pp}sπ interactions at T=353 MeV:

dσ/dΩ and Ayp in pp→{pp}sπ

0 measured in 2009, published

dσ/dΩ and Ayp in pn→{pp}sπ

- measured in 2009, published

Ax,x, Ay,y in np→{pp}sπ- measured in 2011

Next step: measurement of Ax,z in pn→{pp}sπ-


Experiment: scheme of measurementdσ/dΩ and Ay

p

pd→{pp}sπ-+pspec pp→{pp}sπ

0

Polarized proton beam: Py=65%H2 , D2 cluster jet target: d=5∙10

14 cm-2

Luminosity: L=1.5 pb-1Polarimetry, normalization: pn→dπ0

π0 case: {pp} detectedπ- case: + pspec or π-


pp→{pp}sπ0 (talk by D. Tsirkov on Tuesday)

ANKE (black) compared to CELCIUS (red) at 360 MeV(R. Bilger et al, NPA 663 (2001) 633)

Results on dσ/dΩ and Ay (1)

D.Tsirkov et al., Phys. Lett. B 712, 370 (2012)


pn→{pp}sπ-

TRIUMF dataH. Hahn et al., Phys. Rev. Lett. 82 (1999) 2258,H. Hahn et al., Phys. Rev. Lett. 82 (1999) 2258,F. Duncan et al., Phys. Rev. Lett. 80 (1998) 4390F. Duncan et al., Phys. Rev. Lett. 80 (1998) 4390

S.Dymov et al., , Phys. Lett. B 712, 375 (2012)

Results on dσ/dΩ and Ay (2)

ANKETRIUMF pn→{pp}sπ

-

TRIUMF π- 3He→pnnsp


Measurement of Ax,x in dp→psp{pp}sπ-

Vector polarized deuteron beam (P=50-60%) + hydrogen polarized internal target (Q=70-80%)with a storage cell (lower target density)

+ Beam and target polarization product PyQy from Ay, y=1, Ax, x(0

0)=Ax, x(1800)=1 :

Ax, x~ PyQy , Ay, y~ PyQy

• Cell material: 25 μm of Al + 5 μm of teflon is the main source of background• Shape of background obtained from dedicated measurement with N2 in the cell and with empty cell

Polarimetry, normalization: pn→dπ0


cos2(φ) = 1 get Ay,y

cos2(φ) = 0 get Ax,x

θπ=72-1080θπ=0-36

0

θπ=36-720 θπ=108-144

0

θπ=144-1800

3) Ax,x from 1-parameter fit

Results on Ax,x in pn→{pp}sπ- (1)

Observed experimental asymmetry:

ξ=Σ1−Σ2Σ1+ Σ2

where Σ1=N ↑↑+ N ↓↓,Σ2=N ↑↓+ N ↓↑

1) Ay,y from the 2-parameter fit2) From the theory Ay,y = 1, consistent with data. Ay,y can be fixed

ξ /PQ=(Ax , x sin2φ+ A y , y cos

2φ ),


PWA prediction without d-waves:

(1-Ax,x) dσ/dΩ(900) ≈ 52 nb

Preliminary result from the Ax,x measurement:

(1-Ax,x)dσ/dΩ(900) = (78 ± 25) nb

(analysis is in progress)

Preliminary results on Ax,x in pn→{pp}sπ- (2)

(1-Ax,x)dσ/dΩ ~ |δ|2k2 sin2θ


Next step: Ax,z in pn→{pp}s π--

Assumptions used in PWA:

Phase of MSP fixed by Watson theorem

(relates the phase of initial interaction to that of pp-elastic scattering)

Neglect initial 3P2-3F2 coupling,

phases of MdP, Md

F fixed by Watson theorem

Neglect squares of d-waves and their interference

Ax,z will test the assumptions and provide new constrains on PWA.np → {pp}sπ− is preferable since it contains information on the p-waves

Theoretical uncertainty inherent in the assumptions is hard to estimate

Longitudinal beam polarization requires a Siberian snake @ COSY(snake installation at PAX IP is foreseen in 2012-2013)


Physics at COSY using longitudinally polarized beams: Snake Concept

• Should allow for flexible use at two locations

• Fast ramping (< 30s)

• Cryogen-free system

B⋅ dl (Tm)

pn→{pp}sπ- at 353 MeV 3.329

PAX at COSY 140 MeV 1.994

BUP at COSY 30-50 MeV 1.165

Tmax at COSY 2.88 GeV 13.887

ANKE-location

180o

180o

EDDA

PAX-location


COSY - unique fascility for hadron physics with polarized hadronic probes

ANKE allows to investigate a broad field of physics, including NN-scattering, meson production and presicion experiments

The polarized internal target at ANKE allows thedouble polarization experiments – key to the future experimental program at ANKE

Longitudinal polarization at COSY brings new opportunities

Summary

Introduction: OverviewSlide 2Slide 3COSY – Beam parametersSlide 5Slide 6Slide 7Slide 8Slide 9COSY: Determination of h-mass via 2-body reactionSlide 11NN Scattering: pd dynamicsCOSY: NN scattering at ANKERecent Achievements – NN scatteringSlide 15Slide 16Slide 17Slide 18Introduction: NN interactionSlide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 29Slide 30Slide 31Slide 32Slide 33Slide 34

spin physics at anke-cosytheor.jinr.ru/~spin2012/talks/plenary/dymov.pdfnn interaction properties at...

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