N* Program at COSY April 19, 2009 | Hans Ströher (FZ-Jülich)

Selected recent results COSY N* Program: Outline COSY-facility Detection systems Selected recent results 2 2

COSY N* Program: Facility WASA COSY ANKE p, d TOF 3

COSY N* Program: Detectors ANKE 4 4

COSY N* Program: Detectors WASA 5 5

COSY N* Program: Detectors TOF Target Tracking Detectors 6 6

Focussing and defocussing of hydrogen or deuterium hyperfine states COSY N* Program: Targets Cooled Laval nozzle Operation principle: Focussing and defocussing of hydrogen or deuterium hyperfine states Condensation point Virtual target point Skimmer Cluster jet Pellet Polarized (ABS) 7 7

COSY COSY N* Program: Overview N N  N N*  [N N] X (= g, p, h, …) Mostly: no resonance structure, but 3(4)b-phase space & final state IA & resonances difficult to extract resonance parameters But: p N(+)  (N N*)+(+)  d X(+) Special cases, e.g. p p  p p p0p0 Roper COSY WASA at CELSIUS 8 8

COSY N* Program: Recent Results pp  p K+ L 9 9

COSY-TOF experiment: pp  p K+ L COSY N* Program: Recent Results COSY-TOF experiment: pp  p K+ L K+ p Strangeness trigger: charged multiplicity (2  4) Delayed vertex reconstruction: K+ N p p L (1116) p- M(pp-) 10 10

COSY N* Program: Recent Results COSY-TOF experiment: pp  p K+ L Data (3.06 GeV/c) Dalitz plot Contributions of resonances Which resonances contribute ? 11 11

= + COSY N* Program: Recent Results COSY-TOF experiment: pp  p K+ L Full Model N* only FSI only = + Result: Change of different N* contributions as function of beam momentum 12 12

COSY N* Program: Future Plans COSY-TOF experiment: pp  p K+ L Data (cross sections)  ambiguities Counts Ay cos(Θp) cos(Θp) Cross sections not sufficient; polarization data needed ! 13 13

COSY N* Program: Recent Results pp  N K+ S ? 14 14

COSY-11 vs. ANKE experiment: pp  n K+ S+ COSY N* Program: Recent Results COSY-11 vs. ANKE experiment: pp  n K+ S+ COSY-11 (n K+) COSY-11:  S+ cross section near threshold larger than for L !  Contribution of D++* (1620) ? COSY-11 threshold enhancement (K+S+) 15 15

COSY-11 vs. ANKE experiment: pp  n K+ S+ COSY N* Program: Recent Results COSY-11 vs. ANKE experiment: pp  n K+ S+ ANKE: pp  K+p X contributions: L, S0, S+ 5 new energies COSY-11 (n K+) ANKE (K+p, K+p) COSY-11 threshold enhancement (K+S+): No confirmation ! 16 16

COSY N* Program: Recent Results pp  p K+ S*(1480) (…) (…) 17 17

COSY N* Program: Recent Results ANKE-COSY experiment: pp  p K+ (p+- X-+)0 Missing mass distributions Y* (1480) needed in both channels w/ same parameters (M,G) 18 18

COSY N* Program: Recent Results pp  p K+ S*(1385) / L*(1405) 19 19

COSY N* Program: Recent Results ANKE-COSY experiment: pp  p K+ (p- p) X Missing mass distributions L (1405) L-tag !  Separation of L* / S* S (1385) Unambiguous separation of L(1405) and S(1385)  Lineshape of L(1405) 20 20

(Isospin, Strangeness) COSY N* Program: Future Plans WASA-at-COSY experiment: pp  p K+ L p0 (g) Decay scheme for L* / S* L* 1405 -0 + S*0 1385 Mass (MeV/c2) p0 -0 + p0 S 1190 g L 1116 p- 0 + 940 (0, -1) (½ , 0) (1, -1) (Isospin, Strangeness) Direct observation with WASA: Strangeness tag needed 21 21

2p production dominated by resonance excitation COSY N* Program: Recent Results pp  p p p0p0 s N* D N double D 2p production dominated by resonance excitation 22 22

COSY N* Program: Recent Results WASA-at-COSY experiment: pp  p p p0p0 p in forward det´s 2p0 reconstructed from 4g in EMC (pp) invariant mass vs. (ppp) Invariant mass Enhancement at D(1232) and N(1440) observed 23 23

DD model does not reproduce p0p0 data ( PRL 102, 052301) COSY N* Program: Recent Results ABC-Effect ABC: 2p (~ 310 MeV) strong enhancement over phase space no pp-resonance conventional view: excitation + decay of DD-excitation in relative s-wave DD model does not reproduce p0p0 data ( PRL 102, 052301) 24 24

COSY N* Program: Recent Results WASA-at-COSY experiment: pn  d p0 p0 ABC-effect WASA at CELSIUS:PRL 102 Energy dependence of p0p0 cross section 25 25

COSY N* Program: Recent Results WASA-at-COSY experiment: pn  d p0 p0 ABC-effect WASA at CELSIUS:PRL 102 WASA-at-COSY preliminary Striking energy dependence of p0p0 cross section ( ABC-resonance ? ) 26 26

COSY N* Program: Recent Results ANKE-COSY experiment: pp  (pp)s (pp)0 WASA-at-COSY pn  d p0p0 INN = 0 Ipp = 0 ANKE-COSY pp  (pp)s (pp)0 INN = 1 Ipp = 0,2 Could ANKE be missing the point ? Strong spin-isospin dependence ! 27 27

COSY N* Program: Summary, Outlook N* activities at COSY-Jülich – recent results: - higher lying N* resonances - Y*(1480) - L (1405) - ABC (DD)  What about: pp  {nn}s p+p+ ? Future: - ANKE: special cases – no extended program - TOF: hyperon resonances program; polarization - WASA: N* not highest priority; strangeness tag for Y* - Theory support (PWA) 28 28

Thank you for your attention 29