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Status of the p 0 p 0 g analysis

Status of the p 0 p 0 g analysis. S. Giovannella, S.Miscetti. f decays meeting – 22 Feb 2005. Composition of the p 0 p 0 g final state. Two main contributions to p 0 p 0 g final state @ M f : 1. e + e -  wp 0  p 0 p 0 g s vis ( M f ) ~ 0.5 nb 2. f  S g  p 0 p 0 g

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Status of the p 0 p 0 g analysis

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  1. Status of thep0p0g analysis S. Giovannella, S.Miscetti f decays meeting – 22 Feb 2005

  2. Composition of the p0p0g final state Two main contributions to p0p0g final state @ Mf: 1.e+e-wp0 p0p0g svis(Mf) ~ 0.5 nb 2.f Sg p0p0g svis(Mf) ~ 0.3 nb Backgrounds: S= wp + Sg

  3. p2(1) e+ V g f/w/r p1(2) e─ Data and Montecarlo samples DATA 2001+2002 data : Lint = 450 pb─1 Data have some spread aroud the f peak + two dedicated off-peak runs @ 1017 and 1022 MeV  Data divided in 100 keV bins of  s RAD04 MC production: 5  Lint GG04 MC production: 1  Lint Improved e+e wp0p0p0ggenerator Three body phase space according to VDM from NPB 569 (2000), 158 MC

  4. Sample preselection and kinematic fit 1. Acceptancecut: 5 neutral clusters in TW with E > 7 MeV and |cosq|<0.92 [ TW: |Tcl-Rcl/c| < MIN( 5sT, 2 ns ) ] 2. Kinematic fit requiring 4-momentum conservation and the “promptness” of g’s ( TclRcl/c = 0 ) 3. Pairing: best g’s comb. for the p0p0g hypothesis 4. Kinematic fit for both g’s pairing, requiring also constraints on p masses of the assigned gg pairs

  5. g’s pairing p0 mass resolution parametrized as a function of the g’s energy resolution after kinematic fit: sM/M = 0.5 ( sE1/E1sE2/E2) Fit function for energy resolution: sE/E = ( P1 + P2 E ) / E[GeV]P3 - - - EMC resolution — FIT1 resolution Efit (MeV) The photon combination that minimize the following c2 is chosen: c2 = (Mgigj-Mp)/sMij + (Mgkgl-Mp)/sMkl

  6. Analysis cuts 1.e+e- → gg rejection using the two most energetic clusters of the event: E1+E2 > 900 MeV 2. ggg+accidentals background rejection: Eg(Fit2) > 7 MeV 3. Cut on 2nd kinematic fit: c2Fit2/ndf < 3 4. Cut on p masses of the assigned gg pairs: |Mgg-Mp| < 5sM • S= wp + Sg • eana(Sg) obtained using the 2000 data Mpp shape

  7. e+e- gg rejection e+e- gg rejection done using the two most energetic clusters of the event: E1+E2 > 900 MeV Data MC p0p0g events

  8. Dalitz plot analysis: data-MC comparison (I) Analysis @ √s = 1019.6 MeV (Lint = 145 pb-1)

  9. Dalitz plot analysis: data-MC comparison (II) Analysis @ √s = 1019.6 MeV (Lint = 145 pb-1)

  10. Background study for Dalitz plot analysis (I) In order to study the systematics connected to the background subtraction we found for each category a distribution “background dominated” to be fitted • fhg p0p0p0g (most relevant bckg contribution) • Background enriched sample : 4 < c2/ndf < 20 Scale factor : 1.0156 ±0.0002 All of this fit results are used to evaluate the systematics on the background counting : half of the difference ( 1 - scale factor ) is used

  11. Background study for Dalitz plot analysis (II) For f  hg  ggg , f  p0g, f  a0g we calculate a c2 in the mass hypothesis For e+e- gg, we fit the Df distribution for c2/ndf < 3 (and no gg rejection cut ) Scale factor : 0.86 ± 0.02 Scale factor : 2.5 ± 0.2 Scale factor : 1.85 ± 0.03 Scale factor : 0.82 ± 0.02

  12. Dalitz plot @ √s=1019.6 MeV • Fit to the Dalitz plot with the VDM and scalar term, including also • interference • Binning: 10 MeV in Mpp, 12.5 MeV in Mpg • What is needed: • Analysis efficiency • Smearing matrix • Theoretical functions • ISR • Only statistical error and • systematics on background • considered for the moment

  13. Analysis and pairing efficiencies vs Mpp , Mpg Analysis efficiency and smearing matrix evaluated from MC for each bin of the Mpp-Mpg plane Different for the two processes! In the fit of the Dalitz different eana and smearing used for the VDM and scalar contributions. For the moment the VDM results are used also for the interference term

  14. g(fKK) from G(f K+K–) g(f0KK) g(a0KK) g(f0pp) g(a0hp) p2(1) p2(1) } f0/a0 e+ e+ w r f fit output g g r/r/r f/w/w/w Charged kaon loop final state p1(2) p1(2) e─ e─ Fit function: the Achasov parametrization (I) • Scalar produced through a kaon loop • VDM contribution from the following diagrams : • All interferences considered

  15. Fit function: the Achasov parametrization (II) f0g Model dependent term wp/rp Modified in + cos f (???) f0g/VP interf [N.N.Achasov, A.V.Kiselev, private communication] VDM parametrization: CVP fixed - KVDM (norm factor), dbr , MV , GV free

  16. Fit function: different parametrization for the scalar term 1. Point-like Sg coupling. Corrections to a “standard” BW-like f0 (fixed S) described by the a0 , a1 parameters [Isidori-Maiani, private communication] 2. Fit based on the hadronic scattering amplitudes pp→pp , pp→KK in the p0p0g production mechanism [Boglione-Pennington, Eur. Phys. J. C 30 (2003) 503] This is implemented in our fit function with the replacement:

  17. Calculation of the radiative corrections ISR evaluated starting from the following s0 : f0 = “simple” BW (by integrating the Achasov scalar term) wp = SND parametrization from JETP-90 6 (2000) 927, obtained by fitting over a large s range ... Proper threshold behaviour H(s,x) from Antonelli, Dreucci

  18. Fit results: the Achasov parametrization

  19. Fit results: the Achasov parametrization

  20. Fit results: the Achasov parametrization

  21. Fit results: the Achasov parametrization

  22. Fit results: the Isidori-Maiani parametrization

  23. Fit results: the Isidori-Maiani parametrization

  24. Fit results: the Isidori-Maiani parametrization

  25. Fit results: the Isidori-Maiani parametrization

  26. Fit results: the Boglione-Pennington parametrization

  27. Fit results: the Boglione-Pennington parametrization

  28. Fit results: the Boglione-Pennington parametrization

  29. Fit results: the Boglione-Pennington parametrization

  30. Fit results: the Achasov parametrization

  31. Fit results: the Isidori-Maiani parametrization

  32. Fit results: the Boglione-Pennington parametrization

  33. The parametrization with the s meson (I) • The s is introduced in the scalar term as in ref. PRD 56 (1997) 4084. • The two resonances are not described by the sum of two BW but wth the • matrix of the inverse propagators GR1R2. • Non diagonal terms on GR1R2 are the transitions caused by the resonance • mixing due to the final state interaction which occured in the same decay • channels R1 → ab → R2 Where Df0 -fs -sf0 Ds   GR1R2 = PR1R2 = Sab gR2ab PR1ab (m) + CR1R2 CR1R2= Cf0s takes into account the contributions of VV, 4 pseudoscalar mesons and other intermediate states. In the 4q,2q models there are free parameters

  34. The parametrization with the s meson (II) • Extensive tests have been done on the formula used. • Good agreement found between our coding and the one of Cesare • we agreed that there is a mistype in the PRD • We have asked also the help of G.Isidori-S.Pacetti to check this The effect of the free term Cf0s and of its phase is large

  35. Fit results: the Achasov parametrization with s (I) Fit @ 1019.7 MeV SIMPLEX only

  36. Fit results: the Achasov parametrization with s (II) • Black (red) curve are ACH model with (without) the inclusion of the s meson • Blue (purple) curve are the contribution due to the f0 (s) meson only • with the ACH model when including the s meson

  37. Comparison between ACH-IM for the scalar term Without the inclusion of the s meson the agreement between ACH model and IM is not excellent although the integrals do not differ more than 20% above 700 MeV . Including the s the agreement is better!

  38. Conclusions • Fit results start giving reasonable results. Improvement due to: better binning, reduced free VDM parameters (overall scale factor + r, w masses). Is the interference phase added in the right way? • Systematics still to be included in the fit • Achasov model without sigma does not provide a good fit to data Parameters in agreement with our old analysis • The Isidori-Maiani function better describes the data Still some doubts in the use of the pp scattering phase • The Boglione-Pennington parametrization provide a very unstable fit, with very different parameters for different √s • A preliminary test including s in the kaon loop model shows an improvement of the fit

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