1 / 19

Strangeness Production @ COSY

Strangeness Production @ COSY. ANKE. Proton Induced Strangeness Production on Protons and Nuclei Near Threshold Markus Büscher Forschungszentrum Jülich Germany. COSY-11. COSY-TOF. The Accelerator: COSY-Jülich. COSY ( Co oler Sy nchroton) at FZ-Jülich (Germany):

skylar
Download Presentation

Strangeness Production @ COSY

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Strangeness Production @ COSY ANKE Proton Induced Strangeness Production on Protons and Nuclei Near Threshold Markus Büscher Forschungszentrum Jülich Germany COSY-11 COSY-TOF Markus Büscher, HYP2003

  2. The Accelerator: COSY-Jülich COSY (Cooler Synchroton) at FZ-Jülich (Germany): • (polarized) p & d beams • phase-space cooling • electron & stochasting cooling • p = 0.30 – 3.65 GeV/c • pp  pp X (mX  1.1 GeV/c2) • dd  a X (mX  1.0 GeV/c2) • pp  pK+ Y* (mY*  1.5 GeV/c2) • internal & external beams Markus Büscher, HYP2003

  3. COSY vs. Other Accelerators Production Thresholds: p p  p K+ LTp = 1.58 GeV p p  p K+ S0 Tp = 1.79 GeV p p  p K0 S+ Tp = 1.80 GeV p p  p p K+ K-Tp= 2.50 GeV Some interesting reactions: • pp  pK+Y (mY  1.5 GeV/c2) • pp  pp a0/f0(980) • pA  pK+X (Tp = 1.0...2.3 GeV) Several dedicated detection systems... Electron accelerators Hadron accelerators Markus Büscher, HYP2003

  4. Cluster target drift chambers scintillator Detectors at COSY Detectors @ COSY ANKE, COSY-11: • circulating beam • thin internal targets • forward spectrometer (small acceptance) • magnetic spectrometer COSY-TOF: • extracted beam • small target (vertex) • nearly 4p coverage (no charge id) • non-magnetic MOMO (at BIG KARL) Markus Büscher, HYP2003

  5. COSY-TOF: Detection Principle intermediate fiber hodoscope “Quirl“ • No magnetic field • Detection of charged ejectiles • Complete geometrical reconstruction of each event kinematical variables • Start detector optimized for track/vertex reconstruction • Additionally: TOF & DE • Trigger: charge 2  4 Fiber hodoscope Start scintillator Flight path for TOF measurement double-sided ring m-strip Markus Büscher, HYP2003

  6. Strangeness Production … Initial- (ISI) and Final State Interactions (FSI): If (p,Y), (p,K), or (K,Y) travel along with each other, they interact and „distort“ spectra (observables):  exploit this to study such interactions !!  reactions close to threshold Example: (pL)-FSI  (pL) scattering length NN  NN X N Y K ISI Production FSI Markus Büscher, HYP2003

  7. N* & FSI Exp. p-L FSI N*(1650) L-Hyperon Production p p  p K+ L (COSY-TOF) Dalitz-plots: (analysis w/ theoretical model of A. Sibirtsev) • at 2.85 GeV/c (see Fig.)  in addition to p-L FSI, a strong contribution of the N*(1650) nucleon resonance is needed • At higher energies, also the N*(1710) has to be included [FSI+N*(1650)] : N*(1710) ~ 1 N* K+ p L p p W. Schröder, Ph.D. thesis Uni Erlangen, to be published Markus Büscher, HYP2003

  8. Lp Interaction p p  p K+ L (COSY-11) Total cross section for pp  p K+L • .........phase space • ____ p-K+ Coulomb repulsion and p-L strong FSI Dalitz-pot analysis:  spin-averaged Lp-scattering length: a = - (2.0 ± 0.2) fm But: a and r are correlated Watson formula applicable? Spin dependence (as/at)? Theory can help ... ! J.T. Balewski et al., EPJ A2, 99 (1998) Markus Büscher, HYP2003

  9. Lp Scattering Length • Data: • - Lp elastic scattering • (sel = ¼ ss + ¾ st) • - Bubble chamber • Fit: • - Effective-range expansion Lp Lp • Polarisation measurements (COSY)  as, at • Formula also applicable for gd  KLN G. Alexander et al., PR 173, 1452 (1968) observable S = s or t pp K+Lp SATURNE (Dm=2 MeV) a = (–1.5 ± 0.15exp ± 0.3th) fm A. Gasparian et al., subm. to PRC Markus Büscher, HYP2003

  10. q+ • “pentaquark“ states (+)??? observed in (nK+) in photo- nuclear reactions •  here: pp S++ • K0p pp  pK0S+ , 3.30 GeV/c preliminary!  nothing seen in pp L (K+p) !! “... we are optimistic to significantly contribute to the topic ...“ S-Hyperon Production p p  p K0 S+ (COSY-TOF) Dalitz-plots: • at 3.20 GeV/c (see Fig.)  rather smooth distribution Markus Büscher, HYP2003

  11. Nonet of light scalar mesons JP=0+ Possible candidates S } f0(500) (““) k(800) f0(980) a0(980) f0(1370) K0*(1430) a0(1450) f0(1500) K*(?) K*(?) 9 states COSY a0-(?) a00(?) f0(?) a0+(?) } I f0(?) 9 states K*(?) K*(?) The Light Scalar Resonances Markus Büscher, HYP2003

  12. Defined FS isospin Angular symmetries a0-f0 mixing +/0 (pp da0+ dK+K0) = 83% · 38 nb () pN  d 0 0 pn  d K+K- (pn  d a00/f0) vs. (pp  d a0+) (pd 3He a00/f0) vs. (pd 3H a0+) Angular asymmetries ANKE _ K+K0 Photon detector for  identification needed The a0/f0(980) at ANKE/COSY Charge-symmetry breaking a0-f0 mixing dd  4He0 Photon detector (WASA) dd  4HeK+K- pp  d + Summer 2003 COSY-11 pp  pp K+K- MOMO pd  3He K+K- M. Büscher et al., hep-ph/0301126 Markus Büscher, HYP2003

  13. pD K+X Tp = 2.0 GeV K+ Production from pA Reactions p A  K+ X (ANKE) • Inclusive cross sections for • D, C, Cu, Ag, Au Targets • T = 1.0 ...2.3 GeV (TNN = 1.58 GeV) • Reaction mechanisms • Strong collectivity below threshold • Model calculations (CBUU transport, folding model...) • Correlation measurements  pD data: • s(pn  K+X)  4·s(pp  K+X) pC K+X preliminary taken from: K.Tsushima et al., PRC 59, 369 (1999) Publication in preparation Markus Büscher, HYP2003

  14. Nuclear Medium Effects p A  K+ X (ANKE) • Cross-section ratios R(A/C) have very small systematic uncertainties • VK+ is sensitive to peak position in R(A/C) • pA reactions probe nuclear medium at rr0 • Best agreement with calculations for VK+(rr0) = +20 MeV • Expected accuracy <3 MeV K+ rescattering, pA  K+X (ANKE) w/o potentials Coulomb repulsion 0 20 +40 MeV Nuclear potential Transport model: Z.Rudy et al., EPJ A 15, 303 (2002) cross section ratio (Au/C) VK = +20 MeV R(Au/C) T=2.3 GeV M.Nekipelov et al., PLB 540, 207 (2002) Markus Büscher, HYP2003

  15. pp  pK0S+ , 3.30 GeV/c preliminary! pA  K+ X VK = +20 MeV R(Au/C) Strangeness Production … ... fundamental issues can be addressed ... • “Exotic“ states • + in pp  pK0S+ ??? • Charge-symmetry breaking • dd  a (p0h) and a0-f0 mixing • SU(3)flavor symmetry breaking • NY interaction at low relative energies (compare with NN) • In-medium masses ... needs to (and will) be vigorously investigated (at COSY)! Markus Büscher, HYP2003

  16. Background < 10% I.d. of ppdK+K0 events @ ANKE Spectrometer dipole T = 2.65 GeV • K+-d coincidence measurement • Identification of ppdK+X events via TOF, E and particle momenta • Identification of ppdK+K0 events via dK+ missing mass COSY beam p d K+ t Markus Büscher, HYP2003

  17. Fit: [(KK)Pd]S+ [(KK)Sd]P (pp  da0+  dK+K0) = 83% · tot tot(pp  dK+K0) = (38 ± 2stat± 14sys) nb First Results on the a0+ p p  d K+K0 (ANKE) Q = 46 MeV V.Kleber et al., PRL in print; nucl-ex/0304020 Markus Büscher, HYP2003

  18. L vs. S0 Production … pp  pK+L/S0 (COSY-11) L/S0 ratio (same excess energy above threshold): R ~ 25 at threshold, R(E)  3 Difference between L and S0? |L> = |(ud)[I=0,1S0], s> I=0, ½+ |S0> = |(ud)[I= 1,3S1], s> I=1 , ½+  R ~ 3 coupling: gNLK, gNSK  R ~ 27 SN  Lp transition effective Lagrangian / N* PRC 63 (2001) 022202 destructive π/K interference NPA 684 (2001) 397 incoh. π/K nucl-th/0004022 resonance +π/ρ/η nucl-th/0004022 S. Sewerinet al., PRL 83, 682 (1999) Markus Büscher, HYP2003

  19. Experimental challenges ... NN Partial Cross Sections: p p  N Y K (mostly COSY data) more specifically: p p  p L K+ p p  p S0K+ p p  p S+K0 p p  n S+K+ (p p  pp K+ K-) Markus Büscher, HYP2003

More Related