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Study of the decay f  f 0 (980) g  p + p - g

Study of the decay f  f 0 (980) g  p + p - g. C.Bini, S.Ventura, KLOE Memo 294 03/2004 (upd. 06/2005) C.Bini, KLOE Memo 304 03/2005 (upd. 06/2005). Outline. Motivations of this analysis. The data sample: what we measure and how the data look like. Theory, KL, NS, SA,.... The fits.

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Study of the decay f  f 0 (980) g  p + p - g

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  1. Study of the decay f f0(980)g  p+p-g C.Bini, S.Ventura, KLOE Memo 294 03/2004 (upd. 06/2005) C.Bini, KLOE Memo 304 03/2005 (upd. 06/2005)

  2. Outline • Motivations of this analysis. • The data sample: what we measure and how the data look like. • Theory, KL, NS, SA,.... • The fits. • Discussion of the results. • Conclusion: what we learn from this analysis.

  3. Motivations of this analysis • Assess clearly the f f0(980)gp+p-g signal; • determine the f0(980) parameters (coupling to the f to KK and pp); assess the quark content of the f0; • any further meson is needed to describe the data ? • Compare models.

  4. The data sample: the event selection • drc stream • “vertex”: Rv<8 cm; Zv<15 cm; • “2 tracks”: +,-; 45o<q+,q-<135o; • “pion identification” L1 vs. L2 cut (AND); • “large angle”: 45o<qpp<135o; • “track mass”: 129<MT<149 MeV; • “photon matching”: Ecl>10 MeV; qcl>22o Wg<0.03+3/Ecl Ng > 0 See Memo 294

  5. “off-peak” data “on-peak” data spectrum f0(980) signal The data sample: dN/dm • 6.7 ×105 events / 350 pb-1 “on-peak” data • 1.2 ×104 events /6.58 pb-1 “off-peak” data 1017 MeV • 1.0 ×104 events /4.93 pb-1 “off-peak” data 1022 MeV

  6. f0 signal in LA vs. SA events In the f0(980) region: ISR(LA)/ISR(SA)~5  [S/B]LA ~ 60 [S/B]SA The data sample: large angle vs. small angle Red = LA Blue = SA

  7. “off-peak” data “on-peak” data The data sample: Ac Charge asymmetry Ac in bins of m

  8. The data sample: √s dependence s(900-1000 MeV) = N(events 900<m<1000 MeV) / Linte(m)) Blue = “on-peak” sliced data Red = “off-peak” data

  9. Vetocos loss Acceptance loss Photon request loss The data sample: detection efficiency MC stream ppphvlag (ISR+FSR) Sample size ~ data All selection chain apart from: Filfo Vetocos TCA+Likelihood (taken from data) Corrections from: tracking efficiency photon efficiency (1-exp(-E/a)) a~8-10 MeV

  10. Red = data (40 pb-1 sample) Green = background Pink = estimated signal Black = data Blue = p+p-p0 Red = m+m-g Pink = p+p-(no g) The data sample: estimated background Dedicated MC generations of p+p-p0, m+m-g and p+p-(no g): Check done “before photon request”: good agreement above 450 MeV

  11. Zoom (signal region) Before the photon request At the end of the selection Red = data (40 pb-1 sample) Blue = MC(p+p-) + data/eg data Surviving p+p-

  12. Efficiency change after application of the data-MC correction The difference is assumed as an uncertainty (quad. add to stat.). (*) also tried ½ correct.+ ½ error The data sample: systematics due to low energy photons The larger systematic effect is due to the data-MC linearity difference

  13. p+ e+ p- f0 f e- Theory: KL,NS,SA,.... {M} has to rely on “some” model with “some” parameters

  14. If only one meson (no s included): 3 free parameters: mf, gfKK, gfpp Theory: KL (KL) by N.N.Achasov; where: g(m) = kaon-loop function d(m) = phase shift (based on pp scattering data) Df(m) = f0 propagator (finite width corrections)

  15. Theory: NS (NS) after several discussions with G.Isidori, L.Maiani and (recently) S.Pacetti; where the propagator (Flatte’ revised) is: with couplings 7 free parameters: mf, gffg, gfKK, gfpp,a0, a1, b1

  16. Theory: SA (NS) by M.E.Boglione and M.R.Pennington; where T11 = T(pp pp) and T12 = T(pp  KK): (1-m2/s) satisfies gauge invariance requirement. From the polynomials  coupling gf (GeV) residual at the f0 pole. 8 free parameters: m0, a1, b1, c1, a2 , b2, c2, l

  17. The fits. 491 bins, 1.2 MeV wide from 420 to 1009 MeV Free parameters: Background: mr, Gr, a, b, arp Signal: depending on the fit (3 for KL, 7 NS, 8 SA)

  18. The fits: KL (KL) f0(980) only: Fit uncertainties. Covariance matrix of the 3 signal parameters: 1.0 0.56 0.0 1.0 -0.36 1.0

  19. The fits: KL Study of the systematics on the 3 f0(980) parameters: The fits are repeated with fixed “non-scalar” part Summarizing: g2fKK has large systematic uncertainty

  20. The fits: NS

  21. The fits: NS (NS) systematics 1: dependence on the shape of the background baseline fit Polynomial background Second pole background

  22. The fits: NS (NS) systematics 2: correlation between mass and couplings Summarizing.... In terms of couplings

  23. Test of fit stability (on sub-samples); In red the results outside the ranges given before for the parameters

  24. The fits: SA In collaboration with M.R.Pennington  gf = 6.6 ×10-4 GeV

  25. The fits: try to include the s (KL) f0(980) + sBES(541 MeV) scoupling ~ 0 no change (KL) f0(980) + sE791(478 MeV) to f0 parameters (KL) f0(980) + sfree mass found a solution with m=600 MeV (NS) f0(980) + sBES(541 MeV) OR sE791(478 MeV)  bad fit

  26. Use r – w interference pattern to test mass scale and resolution mw = 782.18 ± 0.58 MeV PDG value = 782.59 ± 0.11 MeV Gw= 8.87 ± 0.84 MeV PDG value = 8.49 ± 0.08 MeV Two curves: fit with mw and Gw fixed or free The fits: comment on the background Background parameters: pion form factor (Kuhn-Santamaria parameters) b determines the background level in the f0(980) region  the signal size: Difference up to 5% in the f0 region.

  27. Background-subtracted spectra: KL fit NS fit SA fit Peak size: KL fit  25% of bck NS fit  24% of bck SA fit  33% of bck Different background parameters  different signal shapes Peak FWHM: KL fit  37 MeV NS fit  30 MeV SA fit  45 MeV Discussion of the results: the line-shape Ratio between “non-scalar part” resulting from NS and KL fits.

  28. f(A) = 3/2 p @ f0 pole = p (resonance) + p/2 (kaon-loop, background) Not enough sensitivity to the intermediate region Discussion of the results: the scalar amplitude A is the scalar amplitude: Re(A), Im(A), |A|, f(A) as functions of m: KL (solid), NS (dashed)

  29. Discussion of the results: the f0 parameters. Summarizing... • 5 ÷10 MeV mass difference: all within PDG 980 ±10 MeV. • Discrepancies due to a different interpretation of the line-shape: • for KL all is f0, for NS there is background also. • 3. Agreement on R • 4. gff0g >> gfMg with M any pseudoscalar meson (naïve statement)

  30. Red and Blue = data points Green = KL predictions Discussion of the results: extrapolation to “off-peak” data Not a fit but an “absolute” prediction Red = data points Blue = KL predictions Black = background

  31. Discussion of the results: interpretation of the charge asymmetry “Diluition” due to residual p+p-p0 background is included. The effect is at m<600 MeV Full = data points traingles = predictions ISR+FSR Squares = predictions ISR+FSR+f0(KL) • KL amplitude is able to describe the observed behaviour ! Again: not a fit but an “absolute” prediction

  32. Conclusion. • Goto publication soon including KL and NS results (not SA). • Main results of this analysis: • Observation of f f0(980)g p+p-g; • Determination of f0(980) parameters; • Positive test of the kaon-loop model; • Model-Independent approach very difficult; • We have no sensitivity in the low mass region (we don’t see any s but this is not a good place to look for it). • 2 fb-1 analysis to be done

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