Die Präsentation wird geladen. Bitte warten

Die Präsentation wird geladen. Bitte warten

Markus Büscher DPG Frühjahrstagung Mainz 2004 1 Isospin breaking a 0 -f 0 mixing Markus Büscher Forschungszentrum Jülich Germany...

Ähnliche Präsentationen


Präsentation zum Thema: "Markus Büscher DPG Frühjahrstagung Mainz 2004 1 Isospin breaking a 0 -f 0 mixing Markus Büscher Forschungszentrum Jülich Germany..."—  Präsentation transkript:

1 Markus Büscher DPG Frühjahrstagung Mainz Isospin breaking a 0 -f 0 mixing Markus Büscher Forschungszentrum Jülich Germany... a tool to investigate (not only!) the structure of the light scalar mesons

2 Markus Büscher DPG Frühjahrstagung Mainz Nature of these states?? Genuine q q 4-quark states KK molecules The light scalar resonances COSY S I K * (?) a 0 - (?)a 0 0 (?)f 0 (?)a 0 + (?) f 0 (?) Nonet of light scalar mesons J P =0 + f 0 (500) ( ) f 0 (980) a 0 (980) f 0 (1370) K 0 *(1430) a 0 (1450) f 0 (1500) f 0 (1710) Possible candidates 9 states } 10 states }

3 Markus Büscher DPG Frühjahrstagung Mainz Observables? K (KK/ ) = (0.183±0.024) (seen/dominant) (KK/ ) =... (seen/dominant) a0–a0– a00a00 f0f0 a0+a0+ I3=I3= –1–10+1 m = (984.7±1.2) MeV/c 2 (average) = ( ) MeV/c 2 (estimate) m = (980±10) MeV/c 2 (estimate) = ( ) MeV/c 2 (estimate) a0a0 f0f0 Observables at COSY (yet unknown): Mass distributions Branching ratios to KK and (Differential) production cross sections Isospin ratios (e.g. pn vs. pp reactions) a 0 -f 0 mixing Polarization observables COSY limit a 0

4 Markus Büscher DPG Frühjahrstagung Mainz The Accelerator: COSY-Jülich COSY (Cooler Synchroton) at FZ-Jülich: (polarized) p & d beams phase-space cooling –electron & stochasting cooling p = 0.30 – 3.70 GeV/c –pp pp X (m X 1.1 GeV/c 2 ) –dd X (m X 1.03 GeV/c 2 ) –pp pK + Y* (m Y* 1.5 GeV/c 2 ) internal & extracted beams

5 Markus Büscher DPG Frühjahrstagung Mainz The detectors: ANKE & WASA WASA ANKE In operation since 1998 Ready for experiments in currently at CELSIUS (Uppsala) -nearly 4 coverage -charged and neutral particle i.d. -frozen pellet target ( L ~ few cm -2 s -1 ) -forward spectrometer (small acceptance) -optimized for K + /K - detection -cluster jet target ( L ~ few cm -2 s -1 )

6 Markus Büscher DPG Frühjahrstagung Mainz The a 0 /f 0 (980) at COSY ReactionWhere?ResultGoal pp pp K + K - COSY-11 ANKE a 0 0 /f 0 contribution?? pp d K + K 0 ANKEa 0 + channel dominates d + WASAFirst simple experiment for WASA ( 2006) pn d K + K - ANKE(Feb. 2004) d 0 WASAAngular asymmetries a 0 -f 0 mixing pd 3 He K + K - MOMOa 0 0 /f 0 contribution?? 3 H K + K 0 dd 4 He K + K - ANKEWinter 04/05? 4 He 0 WASAIsospin violation a 0 -f 0 mixing

7 Markus Büscher DPG Frühjahrstagung Mainz p(2.65 GeV)p dK + K 0 at ANKE Fit: [(K K ) S d] P + [(K K ) P d] S tot (pp dK + K 0 ) = (38 ± 2 stat ± 14 sys ) nb Q = 46 MeV K + d coincidence measurement Identification of pp dK + X events via TOF, E and particle momenta Identification of pp dK + K 0 events via dK + missing mass Dominance of a 0 + channel K+K+ d m(K + )+m( K 0 ) 83% V.Kleber et al., PRL 91, (2003)

8 Markus Büscher DPG Frühjahrstagung Mainz a 0 -f 0 mixing in dd 4 He 0 Strength of a 0 -f 0 mixing unknown Probably larger than 0- mixing Close & Kirk: mixing intensity = 8±3% (data from WA102) but critizised by Achasov & Kiselev, Oller dd 4 HeX cross section unknown Our estimate: (dd 4 He a 0 0 ) ~ ( ) pb Pilot measurement: dd 4 He a 0 0 /f 0 4 He K + K – Similar to dd 4 He 0 Direct production of a 0 0 in dd 4 He a 0 0 ( 0 ) is forbidden if isospin is conserved (12.7 ± 2.2) pb (15.1 ± 3.1) pb E.J.Stephenson et al., Phys. Rev. Lett. 91, (2003) ANKE Dominant channel dd 4 He f 0 (I=0) 4 He a 0 0 (I=1) 4 He 0 ??

9 Markus Büscher DPG Frühjahrstagung Mainz dd ( 0 ) vs. dd 0 CSB in propagation of a 0 /f 0 production Details in: C.Hanhart, nucl-th/ m Production nPropagatio CSB 00 /fa N m /fa a 00 /faN m m- 1 t 1 << d d a0a0 0 d d f0f0 a0a0 0 d d 0 d d 0 ? or 0 /

10 Markus Büscher DPG Frühjahrstagung Mainz More a 0 -f 0 mixing... f0f0 a0a0 K0K0 K0K0 _ Further enhancement: Kaon loops f0f0 a0a0 K–K– K+K+ 8 MeV normal CSB o (1%) N.N.Achasov et al., PLB 88, 367 (1979) CSB amplitude d d f0f0 a0a0

11 Markus Büscher DPG Frühjahrstagung Mainz a 0 /f 0 mixing in pn interactions Look, e.g., for angular asymmetries around 90° in pn d+Meson reactions V.Grishina et al., PLB 521, 217 (2001)V.Kudryavtsev et al., PRC 66, (2002) no mixing direct a 0 -f 0 or - mixing Kaon loops angular distribution of the a 0 mass distribution pn pn(d) 0 a00a00 a00a00

12 Markus Büscher DPG Frühjahrstagung Mainz People... M.Büscher, C.Hanhart, V.Hejny, S.Krewald, A.Sibirtsev, H.Ströher IKP, FZ Jülich U.-G.Meißner HISKP, Universität Bonn / IKP, FZ Jülich V.Kleber IKP, Universität zu Köln P.Fedorets, L.Kondratyuk, A.Kudryavtsev ITEP, Moscow, Russia V.Grishina INR, Moscow, Russia A.Dzuba, V.Koptev, S.Mikirtychiants, M.Nekipelov PNPI, Gatchina, Russia and the ANKE collaboration Experiment Theory

13 Markus Büscher DPG Frühjahrstagung Mainz I.d. of pp dK + K 0 ANKE K+K+ d T = 2.65 GeV t p K + -d coincidence measurement Identification of pp dK + X events via TOF, E and particle momenta Identification of pp dK + K 0 events via dK + missing mass Background < 10% COSY beam Spectrometer dipole

14 Markus Büscher DPG Frühjahrstagung Mainz First Results on the a 0 + V.Kleber et al., PRL 91, (2003) nucl-ex/ Q = 46 MeVFit: [(K K ) P d] S + [(K K ) S d] P tot (pp dK + K 0 ) = (38 ± 2 stat ± 14 sys ) nb (pp da 0 + dK + K 0 ) = 83% · tot p p d K + K 0 (ANKE)

15 Markus Büscher DPG Frühjahrstagung Mainz p(2.65 GeV)n dK + K - at ANKE D 2 as an effective neutron target K + K - d coincidence measurement unobserved spectator proton First data on -meson production on neutrons % Narrow a 0 0 /f 0 signal at small K + K - masses?? K+K+ d K-K- m(K + )+m( K - ) inv. mass (K + K - ) very preliminary!!


Herunterladen ppt "Markus Büscher DPG Frühjahrstagung Mainz 2004 1 Isospin breaking a 0 -f 0 mixing Markus Büscher Forschungszentrum Jülich Germany..."

Ähnliche Präsentationen


Google-Anzeigen