Post on 31-Jan-2021
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
S. Dymov Spin Physics at ANKE-COSY 3
• 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)
S. Dymov Spin Physics at ANKE-COSY 4
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
S. Dymov Spin Physics at ANKE-COSY 5
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
S. Dymov Spin Physics at ANKE-COSY 6
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
S. Dymov Spin Physics at ANKE-COSY 7
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
S. Dymov Spin Physics at ANKE-COSY 8
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)
S. Dymov Spin Physics at ANKE-COSY 10
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).
S. Dymov Spin Physics at ANKE-COSY 11
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:
S. Dymov Spin Physics at ANKE-COSY 12
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
S. Dymov Spin Physics at ANKE-COSY 13
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
S. Dymov Spin Physics at ANKE-COSY 14
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
Charge-exchange d-breakup (2)
S. Dymov Spin Physics at ANKE-COSY 15
New!
Td = 1.6 GeV
New!
Td = 1.8 GeV
Td = 2.3 GeV
New!
Deuteron breakup: dp {pp}s n (polarized beam)
Data for Td = 1.6, 1.8, 2.3 GeVNew: measurement of Axx, Ayy
np pn (CEX-amplitudes)Next step: p-beam
Charge-exchange d-breakup (3)
S. Dymov Spin Physics at ANKE-COSY 16
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
Deuteron breakup: dp {pp}s n (polarized beam)
Data for Td = 1.6, 1.8, 2.3 GeV New: measurement of dσ/dq
np pn (CEX-amplitudes)Next step: p-beam
Charge-exchange d-breakup (4)
S. Dymov Spin Physics at ANKE-COSY 17
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
Charge-exchange d-breakup (5)
S. Dymov Spin Physics at ANKE-COSY 18
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
Charge-exchange d-breakup (6)
S. Dymov Spin Physics at ANKE-COSY 19
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
S. Dymov Spin Physics at ANKE-COSY 20
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
S. Dymov Spin Physics at ANKE-COSY 21
• 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)
S. Dymov Spin Physics at ANKE-COSY 22
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
S. Dymov Spin Physics at ANKE-COSY 23
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)
S. Dymov Spin Physics at ANKE-COSY 24
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-
S. Dymov Spin Physics at ANKE-COSY 25
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-
S. Dymov Spin Physics at ANKE-COSY 26
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)
S. Dymov Spin Physics at ANKE-COSY 27
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
S. Dymov Spin Physics at ANKE-COSY 29
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
S. Dymov Spin Physics at ANKE-COSY 30
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 ),
S. Dymov Spin Physics at ANKE-COSY 31
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
S. Dymov Spin Physics at ANKE-COSY 32
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)
S. Dymov Spin Physics at ANKE-COSY 33
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
S. Dymov Spin Physics at ANKE-COSY 34
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