Mitglied der HelmholtzGemeinschaft Baryons 2013 International Conference on

Mitglied der Helmholtz-Gemeinschaft Baryons 2013 International Conference on the Structure of Baryons June 24 th – 28 th 2013, Glasgow The Hadron Physics Program at COSY-ANKE: selected results June 26, 2013 | Andro Kacharava (JCHP/IKP, FZ-Jülich)

Outline Ø • • • Ø Introduction Overview of the program Experimental facilities (COSY, ANKE) SPIN physics program: selected results Nucleon-Nucleon scattering Pion production Hyperon-Nucleon interaction Future measurements

Introduction: Program overview Goal: Study of 3 -body final states aiming to extract basic spin-dependent two-body scattering information Tools: • Hadronic probes (p, d) • Double polarization (beam and target) Topics: 1. NN scattering ↔ pp- and np-amplitudes, nuclear forces 2. Meson production ↔ NNπ amplitudes (PWA), Ch. PT 3. Strangeness production ↔ YN interaction, N scattering lengths COSY proposal #152 Ar. Xiv: nucl-ex/0511028

Introduction: COSY storage ring COSY (COoler SYnchrotron) at Jülich (Germany) • Energy range: 0. 045 – 2. 8 Ge. V (p) 0. 023 – 2. 3 Ge. V (d) Ø Hadronic probes: protons, deuterons Ø Polarization: beam and targets • • • Max. momentum ~ 3. 7 Ge. V/c Energy variation (ramping mode) Electron and Stochastic cooling Internal and external beams High polarization (p, d) Spin manipulation

Introduction: COSY overview Hadron physics with hadronic probes WASA Experimental set-ups: Ø ANKE Ø WASA Ø EDM ANKE EDM (BNL/JEDI) Ø PAX Ø TOF (ext. ) TOF … the machine for hadron spin physics

Apparatus: ANKE spectrometer ANKE PIT S. Barsov et al. , NIM A 462, 364 (1997) Main features: Ø Excellent Kaon identification (Positive and Negative) Ø Low energy proton (spectator) detection (STT) Ø Di-proton ({pp}s) selection (by FD) Ø Polarized (unpolarized) dense targets STT

Apparatus: PIT at ANKE Polarized Internal Target (PIT): Ø Ø Ø Polarised H (D) gas (ABS) in the cell • Qy = 0, -1, +1, high degree >90% • Density ≥ 1013 cm-2 Storage cell: 20 x 15 x 390 mm 3 Lamb-shift Polarimeter COSY beam M. Mikirtychiants et al. , NIM A 721, 83 (2013)

NN scattering: Motivation (pp) • Description of nucleon-nucleon d /d (pp) interaction requires precise data for Phase Shift Analysis (PSA) • COSY-EDDA collaboration produced wealth of data (35°<θp<90°) for pp elastic scattering • Large impact on PSA > 0. 5 Ge. V: Significantly reduced ambiguities in I=1 phase shifts • No exp. data at smaller angles (θp<35°) above Tp=1. 0 Ge. V F. Bauer et al. , PRL 90, 142301 (2003) M. Altmeier et al. , PRL 85, 1819 (2000) Ay (pp) EDDA ANKE

NN scattering: Motivation (np) np charge-exchange R. Arndt: “Gross misconception within the community that np amplitudes are known up to a couple of Ge. V. np data above 800 Me. V is a DESERT for experimentalists. ” np charge-exchange d /d (np) ANKE np forward Ayy (np) ANKE np forward ANKE is able to provide the experimental data for both: pp and np systems and improve our understanding of NN interaction

NN scattering: Measurements at ANKE np system: different isospin channel Ø via Charge-Exchange deuteron breakup: deuteron beam: dp→{pp}S (0 )+n 0 deuteron target: pd→{pp}S(180 )+n 0 dp observables: d /d , T 20, T 22, CN, N → d D Ø n → ↑n p ↑p ↑ psp ↓ p quasi-free np observables: Ay, Ayy, Cxy, y Ø Transition from d → (pp)1 S : 0 pn np spin flip Ø np spin-dependent ampl. s: 2 2 d , T 20 , T 22 , , dq Epp < 3 Me. V, {pp}s

NN scattering: pp elastic § dσ/dΩ at 8 beam energies: Tp = 1. 0, 1. 6, 1. 8, 2. 0, 2. 2, 2. 4, 2. 6, 2. 8 § Precision measurements: Tp = 1. 0 Ge. V • Luminosity by Schottky technique ~ 2% • Absolute cross section ~ 5% § i l re P y r a n i m Details: Stein et al. , PR ST-AB 11, (2008) • • ANKE Tp = 2. 8 Ge. V Tp = 2. 0 Ge. V SAID ANKE SAID • ANKE

NN scattering: pp elastic (Ay) ANKE exp. , April 2013, on-line (fast) analysis Tp = 0. 8 Ge. V SAID • Ay for pp elastic (ANKE) at 6 beam energies: Tp = 0. 8, 1. 6, 1. 8, 2. 0, 2. 2, 2. 4 • FD and STT detection system is used; † ANKE + ANKE SAID y r a ANKE n i m i l e Analysis in progress. . . • Beam polarization from EDDA <Py> ≈ 50 to 65% (Preliminary) ANKE data shows different shape compared with SAID predictions at higher energies ! Pr Tp = 2. 0 Ge. V SAID † ANKE + ANKE

NN scattering: np system Di-proton program: {pp} in 1 S 0 state D. Chiladze et al. EPJA 40, 23 (2009) Axx (T 22) Deuteron breakup: dp {pp}sn (polarized beam) Ø np-data at Td = 1. 2 Ge. V: Proof of method ! Ø theory: Impulse approximation with current SAID input [DB&CW, NPA 467, 575, (1987)] Td = 1. 2 Ge. V Ayy (T 20) Achievements: • Method works at Td = 1. 2 Ge. V • Application to higher energies Td=1. 6, 1. 8, 2. 27 Ge. V (for an angular range up to θc. m. < 350) Goal: deduce the energy dependence of the spin-dependent np-elastic amplitudes Tn = 600 Me. V SAID np amplitudes

NN scattering: np system (dσ/dq, Aii) D. Mchedlish. et al. , EPJA 49, 49 (2013) dp {pp}sn Td = 1. 6 Ge. V (800 Me. V/A) Td = 1. 8 Ge. V (900 Me. V/A) Td = 2. 27 Ge. V (1135 Me. V/A) reduced by 25% SAID ANKE

NN scattering: np system (Ay, Ci, i) • D. Mchedlish. et al. , EPJ A 49, 49 (2013) →→ dp → {pp}sn • Di-proton system, Epp < 3 Me. V • New: measurements for Cx, x and Cy, y Td = 1. 2 Ge. V Td = 2. 27 Ge. V Problem with reduced by 25% Challenge: put info (about np spin-dependent amplitudes) into the SAID program !

NN scattering: np with Δ-isobar Di-proton program: {pp} in 1 S 0 state (Epp < 3 Me. V) → • deuteron breakup: dp {pp}s 0 (polarized) Td = 2. 3 Ge. V n 0 • spin transfer in the process: np p 0 first measurement (at 2. 3 Ge. V) ! significant differences ( 0 and n): - relative sign of A´s interchanged - A´s ~ 0 for low momentum transfer dp {pp}s+X 0 D. Mchedlishvili et al. , ar. Xiv: nucl-ex/1305. 54 n

NN scattering: np → pΔ 0 channel dp {pp}s+X Mchedlishvili et al. , ar. Xiv: nucl-ex/1305. 54 Td = 1. 6 Ge. V Direct mechanism: ∆ isobar direct production by the one pion exchange Td = 1. 8 Ge. V Exchange mechanism: ∆ isobar excites inside the projectile deuteron 1. 2. Pion-nucleon are from different vertices I=1/2 and I=3/2 both are allowed • Direct one-pion-exchange model for np p 0 works fine for high Mx; • Search for other mechanisms that might dominate near N thresh. ; Further theory work is needed ! Td = 2. 27 Ge. V

NN scattering: np → pΔ 0 channel → dp→{pp}s∆0 high mass region: 1. 19 < MX < 1. 35 Ge. V/c 2 → dp→{pp}sn at Td = 1. 2 Ge. V COMPARE ! Differences: Ø Signs are flipped for all Td Ø Axx and Ayy are small at qt=0 Data will provide further impetus to the construction of more refined np→p∆0 models ! Ø next step: pd {pp}s. X measur. at higher proton energies

Pion production: Physics case Extension of Ch. PT to the NN→NNπ process • A full data set of all observables in pp → {pp}s 0 and np → {pp}s - • Extract the relevant PW amplitudes and test the Ch. PT predictions ( is in a p-wave, initial & final NN-pairs in S-wave, di-proton {pp}s in 1 S 0 state) pp → {pp}s 0 includes 3 P 0 → 1 S 0 s, 3 P 2 → 1 S 0 d and 3 F 2 → 1 S 0 d 3 S → 1 S p and 3 D → 1 S p np → {pp}s - adds 1 0 • p-wave amp. s (M p. S, Mp. D) give access to the 4 Nπ contact operator, controlled by the Low Energy Constant (LEC) d NN NN 3 N scattering V. Baru et al. , PRC 85, (2009) A. Filin et al. , PLB 681, (2009) LEC d connects different low-energy reactions: pp→de+ν, pd→pd, γd→nnπ+ Final goal is to establish that the same LEC controls NN→NNπ !

Pion production: π0 channel dσ/dΩ and Ay in pp→{pp}sπ0 D. Tsirkov et al. , PLB 712, 370 (2012) Near threshold at Tp=353 Me. V Ay is large due to s-d interference ! • ANKE ○ CELSIUS • well represented by retaining only pion s and d waves, no evidence for high PW’s; • assuming coupling between NN-channels and invoking Watson theorem allows to estimate corresponding amplitudes with their phases: Ms. P, Md. P and Md. F

Pion production: π− channel dσ/dΩ and Ay in pn→{pp}sπ- Tp=353 Me. V • ANKE ▲ S. Dymov et al. , PLB 712, 375 (2012) --- best fit global fit TRIUMF H. Hahn et al. , PRL 82 (1999) F. Duncan et al. , PRL 80 (1998) • both observables are described in terms of s-, p-, and d- wave pion amplitudes; • an amplitude analysis of the combined data sets allowed to obtain: Ms. P, Md. F, M p. S, Mp. D

Pion production: π− channel Ax, x and Ay, y in np→{pp}sπ- (Tp=353 Me. V) All Observables in np→{pp}sπ- (ANKE data) Ay, y ≡ 1 conservation laws 1 2 Ax, z measurement in: 3 • pp→{pp}sπ0 will test the PWA assumptions • pn→{pp}sπ- will choose between the solutions S. Dymov et al, Acc. in PRC, ar. Xiv: nucl-ex/1304. 36 Data will allow a robust PW decomposition for both channels and determine relevant pion p-wave production strength making contact with Ch. PT theory !

Strangeness: YN interaction p p K+ Y N (mostly COSY data) T. Roźek et al. , PLB 643, 251 (2006) Ø Importance of Final State Interaction of p system ▲●○ pp → p. K+Λ Ø Incoherent sum of 3 S and 1 S 1 0 Ø FSI with unknown relative strengths Ø Spin dependence of FSI is unknown leaves too much ambiguity in theor. modeling Ø No direct measurements exist ! ■□ pp → p. K+Σ 0 without FSI (. . ) with Yp FSI ( )

Strangeness: Spin-singlet/triplet Λp interaction Separation of spin-singlet (as) and triplet (at) Λp production amplitudes and final state interactions through the measurement of: pp → K+(Λp) spin correlation CNN Experimental information: • Some data on low energy (spin-averaged) Λp total elastic cross sections; • Binding energies of hypernuclei suggest spin singlet force as is more attractive than at ; • Λp FSI in K- d → π− (Λp) is sensitive to S-wave spin-triplet; • FSI of pp → K+(Λp) is unknown mixture of as and at ; • Precise (inclusive) measurements carried out at SATURNE and HIRES/COSY; • HIRES: global fit of all relevant data gave best fit with purely singlet (Λp) amplitude Ø Better to measure in a single experiment ! COSY proposal #219 (2013)

Strangeness: Spin-singlet/triplet Λp interaction Further information: • COSY-TOF has clearly shown dominance of N* prodiction in pp → K+(Λp): suggests S-wave final state dominance; • In the near-threshold region there are two pp → K+(Λp) final S-wave production amplitudes: Μ 1 = [ W 1, s ηf p • εi + i. W 1, t p • (εi X εf)] f • i • The unpolarized cross section is proportional to: I (pp → K+Λp) = ¼ (|W 1, s|2 + 2 |W 1, t|2) • The spin-correlation picks out purely the singlet: I (pp → K+Λp) CNN (pp → K+Λp) = ¼ |W 1, s|2 Ø The ratio of spin-triplet to spin-singlet production is fixed completely by spin-correlation: [ 1 - CNN (pp → K+Λp) ] / 2 • CNN = |W 1, t|2 / |W 1, s|2 Ø The first aim of exp. : what fraction of the production is associated with spin-singlet and triplet (Λp) ? Ø There will be a tremendous enhancement near Λp threshold due to very strong FSI ! S. Abd El-Samad et al. , PLB 688, 142 (2010) G. Fäldt and C. Wilkin, EPJ A 24, 431 (2005) A. Gasparyan et al. , PRC 69, 034006 (2004)

Strangeness: Spin dependence of the p force Ø Each of the W 1, t and W 1, s will have own FSI factor, depending on spin-triplet/singlet scattering lenghts; • HIRES/COSY PLB 687, 31 (2010) Ø We want to measure CNN as a function of the kaon momentum in the region of …. phase-space combined fit …. spin aver. par. combined fit Λp final state interaction peak; Ø Simple π+ρ exchange model near threshold suggests that singlet production is 5 times stronger than triplet will give globally CNN ≈ 0. 84. G. Fäldt and C. Wilkin, EPJ A 24, 431 (2005) ØANKE has considarable experience in detecting K+p correlations and able to measure such an observable !

Future measurements: ANKE experiments Double polarization: (i) pn np (spin observables) (ii) np {pp}s - (Axz parameter) (iii) pp K+ p (CNN coefficient) All experiments are approved and scheduled for 2013/14 !

Summary Ø COSY - unique opportunities for hadron physics with polarized hadronic probes (beam & target) – High precision + Spin Ø ANKE state-of-the art facility to investigate a broad and exciting field of physics Ø Physics: “NN interaction, Ch. PT, FSI ” – selected examples and further plans at ANKE Ø New opportunities to explore longitudinal polarization using Siberian Snake at COSY

The END Many thanks to the conference organizers !

Spare slides

Strangeness: K+K- pair production at ANKE pp → pp. K+K • Production of kaon pairs below the and above φ-threshold can be understood in terms of pp & Kp FSI • The shapes of Kp and Kpp invariant masses are strongly influenced by the K-p interaction ! RKp shows preference for low values of MKp K+pp K-pp Y. Maeda et al. , PRC 77, 015294 (2008) • It has been suggested (CW) this may connected with the production of the (1405) excited hyperon assuming the decay N* K+ (1405) RKp C. Wilkin, Acta. Phys. Polon. Suppl. 2, 89 (2009) • The strength of the KN intercation important element in the iterpretation of possible kaon nuclear systems, such as deeply bound K-pp states. Q. I. Ye et al. , PRC 87, 065303 (2013) RKpp

Physics at COSY using longitudinally polarized beams: Snake Concept o • Should allow for flexible use at two locations 80 1 ANKE-location • Fast ramping (< 30 s) PAX-location • Cryogen-free system EDDA pn→{pp}sπ- at 353 Me. V 3. 329 PAX at COSY 140 Me. V 1. 994 BUP at COSY 30 -50 Me. V 1. 165 Tmax at COSY 2. 88 Ge. V 13. 887 1 8 0 o B dl (Tm)

ANKE Silicon Tracking Telescopes: