1 / 27

International Conference on the Structure and Interactions of the Photon

International Conference on the Structure and Interactions of the Photon. Experimental Measurement of the F meson radiative decays into scalars and pseudoscalars mesons. The KLOE Coll. presented by Camilla Di Donato I.N.F.N. Naples. KLOE data collected.

eve-willis
Download Presentation

International Conference on the Structure and Interactions of the Photon

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. International Conference on theStructure and Interactions of the Photon Experimental Measurement of the F meson radiative decays into scalars and pseudoscalars mesons The KLOE Coll. presented by Camilla Di Donato I.N.F.N. Naples

  2. KLOE data collected • 1999 run : 2.5 pb-1 machine and detector studies • 2000 run : 25 pb-1 • 7.5x107f • published results • 2001 run: 190 pb-1 • 5.7x108f • analysis in progress • 2002 run: 300 pb-1 • 9.0x108f • analysis in progress

  3. KLOE • Drift chamber: • dp/p < 0.4% • xy150 m ; z2 mm • E.m. calorimeter: • sE/E = 5.4% / (E(GeV)) • st = 55 ps/(E(GeV))40 ps • 98% of 4 Magnetic field:0.52 T

  4. Fradiative decays • Analysis of 2000 data: Ldt = 16 pb-1 • F  hg / hgPhys. Lett. B541 (2002), 45 • F  p0 p0 gPhys. Lett. B537 (2002), 21 • F  h p0 gPhys. Lett. B537 (2002), 209

  5. Fradiative decays • Pseudoscalar mesons (JPC= 0-+) • h (547) (I=0) • h (958) (I=0) • Scalar mesons (JPC= 0++) • f0(980) (I=0) • a0(980) (I=1)

  6.  /  • The mass eigenstates ,  are related to SU(3) octet-singlet • 8, 1 through the mixing angle P • Recent studies based on PT and phenomenological analyses • suggested a two mixing angle scenario • In the quark flavour basis the two mixing angles are almost equal •  mixing is described by only one parameter (P)

  7.  /  • Pcan be extracted from the ratio • (Bramon et al., Eur.Phys.J.C7(1999)) : • Br() can probe the gluonic content of 

  8.  /  • Decayswith+- 3 final state: • ;+-0;0 Br  310-3 •  ; +- ;  Br  210-5 • Background from +-0and KLKS(with KLdecaying near the IP) • Analysis cut: • 1 vertex in IR with 2 tracks • 3 prompt  (E>10 MeV,|cos|<0.93) • Constrainedkinematic fit • topological cuts on the energy of particles • tot () = 37 % • tot () = 23 %  ´

  9. F =0.95 (interference with e+e-( )  /  • Main background is  • Selection: elliptic cut in the plane of the two most energetic photons Phys. Lett. B 541 (2002), 45 M (MeV) N() = 120 12 5 events; N() = 50210  220 events R = Br()/Br()

  10. (2) (1)  /  • Using PDG value for Br(): •  Br() = (6.100.610.43)10-5 • Pseudoscalar mixing angle: • P = (41.8  1.7) (flavor) •  P = (-12.9 1.7) (octet-singlet) • Gluonic content of : • Consistency check: if Z=0  |Y|=cosP • other constraints on Xand Yfrom: • (1) /(0 • (2) /(0

  11. M (MeV)  /  100 pb-1 (2001)

  12. dN/dE Ks p0 p0 Kl p+p-p0 Ks  p+p-g Kl p0p0p0 data Ks p0 p0 Kl p+p-p0 Ks  p+p-g Kl p0p0p0 data dN/dE 2000 2001 2002 Eg (MeV) Ep++Ep- (MeV) p+p-7 • Selection: preliminary Ep++Ep- (MeV) N() = 153 12 Br() = (7.05±0.50+0.53/-0.46)x10-5

  13. f f0 (980) g / a0 (980) g • The scalar mesonsf0(980) a0(980) are not easily interpreted • as qq states • Jaffe(1977) suggested qqqq states • Weinstein, Isgur (1990) suggested KK molecule • Both BR and scalar mass spectra are sensitive to nature Br(f0) 5  10-5 3  10-4 10-5 Br(a0) 2  10-5 2  10-4 10-5

  14. f0 model g2f0KK/(4) 2.3 0.15 0.3 (GeV2) (=g2a0KK/4) (=g2a0KK/4) (=2g2a0KK/4) gf0 /gf0KK 0.3—0.5 2 0.5 Br(00)104 ~ 1 ~ 0.15 ~ 0.2 a0 model g2a0KK/(4) 2.3 0.15 (GeV2) (=g2f0KK/4) (=g2f0KK/4) ga0/ga0KK 0.91 1.53 Br( a0)104 ~ 2 ~ 0.2 Models • Predictions from Achasov-Ivanchenko, Nucl.Phys.B315(1989)

  15. Scalar mesons (JPC= 0++) • f0(980) (I=0) f000+- • a0(980) (I=1) a0 • Studied decays (data sample: 16 pb-1 from the 2000 data,~5107) • f0 ; f000  5  final state • a0 ; a00  (39%)  5  • a0 ; a00 +-0 (23%)  2 ch. tracks +5  • first observation  Previous meas. at VEPP2M

  16. 5 g final states • cross sect.(nb) • Signal:00 (f0 ; (500) ; 00) ~ 0.35 •  00  0 • 0 ( a0 ;  00) ~ 0.1 •   • Background: e+e-0 00 ~ 0.5 • 3 (with accidental ’s) (~17) •  000 (with 2 lost) (~14) • Sample selection: • exactly 5 prompt photons • E > 7 MeV • |cos| < 0.93 to avoid the quadrupole region • 5Ei > 700 MeV to reject KLKS neutrals

  17.  0 0 00 • Constrained kinematic fit • to improve resolutions • Photon pairing • |M - M| < 5(M) • Reject events with: • |M - M| < 3(M) •  3102 events • <> = 40% 1+cos2 Estimated backgr. (~20%) e+e-0 00 33924 0 16616  000 15912

  18. radiative g gKK gf0KK gf0 0 K+ f f0 K- 0 Fit to Mspectrum • Model : • 1) f0 dominated by kaon loop • (Achasov-Ivanchenko, Nucl.Phys.B315(1989)) • 2) f0 propagator with finite width corrections • 3) (500) B-W with M=478 MeV and =324 MeV • (Fermilab E791-Phys.Rev.Lett.86(2001)770) • 4) point-like coupling of (500) to  • (Gokalp,Yilmaz,Phys.Rev.D64(2001)) • 5)  + interference term parameterizations • from Achasov-Gubin, (Phys.Rev.D63(2001)) • Two fits: • Fit A :| (f0) + (00 )|2 • Fit B : | (f0)+ () + (00 )|2 • Free parameters: Mf0, g2f0KK, g2f0/g2f0KK, g and(gg)2

  19. Fit results A B 2/ndf 109.5/33 43.2/32 Mf0 (MeV) 9624 973 1 g2f0KK/(4) 1.290.14 2.79 0.12 (GeV2) g2f0KK/g2f0 3.220.29 4.000.14 g — 0.060 0.008 • (  contribution negligible ) • Br(00) = (1.09  0.03  0.05)  10-4 (Fit B) • (SND: (1.220.10 0.06)  10-4 ; CMD-2: (1.080.170.09)  10-4)  Largef0- destructive interference at M < 700 MeV Br(f0)= (4.47  0.21)  10-4

  20. Events cos Events 0 (with ) • Constrained kinematic fit • to improve resolutions • Photon pairing: (1) 00 ; (2) 0 •  reject 00 events • M  < 760 MeV (reject f0 events) • |M - M| < 3(M) •  916 events <> = 32 % M (MeV/c2) • Data —MC • Estimated backgr.: (~30%) • e+e-0 00 546 • 00 15216 •  000 9810 •   52 Br(0)=(8.510.510.57) 10-5 SND :(8.8 1.40.9)  10 –5 ;CMD-2: (9.0 2.41.0)  10 –5

  21. 0 +-5 (+-0) • No background with the same final state • Backgr.: 2 Tracks + 3/4 photons (e+e-0 ; +-0) • ( ; +-0) • 2 Tracks + 6 photons • (KSKL+-000) • 1 vertex in IR with 2 tracks • 5 prompt  (E>10 MeV, |cos|<0.93) • Constrainedkinematic fit • M+-< 425 MeV (reject KSp+p-) •  197 events <>=19% • estimated backgr. 44 events Br(0)=(7.960.600.47) 10-5

  22. Fit to Mhspectrum • Same model as for the f0 (kaon loop) • Combined fit, relative normalization fixed • to Br()/Br(+-0) • Free parameters: • g2a0KK, ga0/ga0KK and Br(000) • Ma0=984.8 MeV (PDG) fixed • 2/ndf 27.2/25 • g2a0KK/(4) (GeV2) 0.40  0.04 • ga0/ga0KK 1.35  0.09 • Br(000) (0.5  0.5)  10-5 5 +-5 Br(a00)= (7.4  0.7)  10-5

  23. KLOE f0 model g2f0KK/(4) 2.790.12 2.3 0.15 0.3 (GeV2) (=g2a0KK/4) (=g2a0KK/4) (=2g2a0KK/4) gf0 /gf0KK 0.500.01 0.3—0.5 2 0.5 Br(00)1041.090.07 ~ 1 ~ 0.15 ~ 0.2 a0 model g2a0KK/(4) 0.400.042.3 0.15 (GeV2) (=g2f0KK/4) (=g2f0KK/4) ga0/ga0KK 1.350.09 0.91 1.53 Br( a0)1040.740.07 ~ 2 ~ 0.2 Summary of fit results • Comparison with predictions from Achasov-Ivanchenko, Nucl.Phys.B315(1989) • f0 parameters are compatible with model • a0 parameters seem not compatible with model

  24. 2001+2002 data 2000 data M (MeV) M0 (MeV) f f0(980) g / a0(980) g Phys. Lett. B 537 (2002), 21 Phys. Lett. B 536 (2002), 209

  25. Conclusions First KLOE published papers on f radiative decays, 2000 events: • Br() = (6.100.610.43)10-5 • P = (41.8  1.7)(flavor) • Br(00) = (1.09  0.03  0.05)  10-4 • Br(f0) = (4.47  0.21)  10-4 • Br(a0) = (7.4  0.7)  10-5 Analysis in progress on 2001+2002 events  500pb-1: more statistic and models with more free parameters

  26. ====================================================== Author : KLOE Collab. (Speaker: Camilla Di Donato) Type : Experimental Measurement of the Phi meson radiative decays into scalars and pseudoscalars mesons. The Kloe experiment has measured the radiative decays of the Phi meson into pi0, eta and eta'(958); these measurements are relevant to assess the mixing in the pseudoscalar nonet as well as to evaluate the gluon content in the eta'(958). Moreover also the radiative decays into pi0 pi0 gamma and eta pi0 gamma have been measured. These decays are dominated by the final states f0(980) and a0(980). The measurement of the branching ratios and of the pi0-pi0 or eta-pi0 invariant mass spectrum helps to understand the controversial nature of the above scalar mesons. ==================================================

More Related