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Status report on  0  ( a 0  0 ) 5  final state

Status report on  0  ( a 0  0 ) 5  final state. P.Gauzzi, R.Volpe. Outline. Background evaluation: determination of the weights to apply to the MC samples for the relevant background processes, 3, 7,  0  0  ( 0 and f 0 )

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Status report on  0  ( a 0  0 ) 5  final state

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  1. Status report on 0 (a00)5  final state P.Gauzzi, R.Volpe

  2. Outline • Background evaluation: determination of the weights to apply to the MC samples for the relevant background processes, 3, 7, 00 (0 and f0) • New analysis cuts: to reduce the depencence of the efficiency on the π0 invariant mass. • Efficiency

  3. Background evaluation • Analysed sample: 2001– 2002 data  L = 217 pb-1 • The final sample has large irreducible background, that has to be subtracted • We cannot rely on the MC cross-sections: • For some process are wrong (e.g. π0) • In other cases are not well known (f0) • Other processes depend on merging/splitting (→3, 7), we don’t know how well they are reproduced by the MC • Our goal is to determine for each process a weight to apply to MC (‘rad04’ 2001-02 production): • Select a sample dominated by the specific background with a small signal (a0) content • Fit some distribution to determine the weight and check with other variables • w = Nfit / Nexpected(MC)

  4. data 7 KLKs 0 M (MeV)(a0)  (30) 2002 • Eprompt > 700 MeV • 2fit < 27 • E3 > 75 MeV • |M()-547.3| > 30 MeV • Erec(3) < 340 MeV • 2sel3 > 4 • 12<2f0sel< 20 N(a0)/Ntot  0.4% • KSKL contribution from MC “all_phys” • Free parameters: w(→7), w(KSKL) and w(π0), other pocesses fixed w(7)=1.190.02 w()=13.7  4.5 w(KLKS)=3.80.6

  5. M(f0 ) (MeV)  (30) 2002 Check with other distributions • data 7 KLKs 0 cos(ω)(0) Φ (rad) (0) cos(f0 ) cosψ(f0)

  6. 2fit  (30) 2002 • data 7 KLKs 0 cos(a0) M (MeV) (a0)

  7. M (MeV) (a0)  (30) 2001 • data 7 KLKs 0 w(7)=1.08  0.02 w()= 10.6  2.1 w(KLKS)=3.40.5 Different machine bckg conditions  8% correction in 2001 vs 19% in 2002

  8. M(f0 ) (MeV)  (30) 2001 • data 7 KLKs 0 cos(ω) (0) cos(f0) cosψ(f0) Φ (rad) (0)

  9. M (MeV) (a0)  (30) 2001 • data 7 KLKs 0 cos(a0) M (MeV) (a0) 2fit

  10. () () • data →3π0 7 f0 0 a0  () 2002 • Eprompt > 700 MeV • 2fit < 27 • 2a0sel < 27 • d2< M < d1 • |M()-547.3| < 30 MeV • E1+E2+E3 > 950 MeV N(a0)/Ntot  7% •  respectively in the hypoth.  and 0 w()=3.390.07 w()=3.920.52

  11.  () 2001 • data →3π0 7 f0 0 a0 () () w()=2.010.03 w()=3.130.03

  12.  () • Factor of 3 more 3 events in 2001 than in 2002 according to MC: N(2001) =19.4 evts/pb-1 ; N(2002)= 6.5 evts/pb-1 • Also in data N(2001) > N(2002) 2001 2002 E1+E2+E3 (MeV) E1+E2+E3 (MeV)

  13.  () 2002 • data →3π0 7 f0 0 a0 E1+E2+E3 (MeV) E() (MeV) M(MeV)(f0) cos (0) Ein t.w.(MeV)

  14. data →3π0 7 f0 0 a0  () 2001 E1+E2+E3 (MeV) E() (MeV) cos(f0) M(MeV) cos(0) Ein t.w.(MeV)

  15. d2 d1 Mπ (MeV) M(MeV) (f0) 0 Signal (a0 ) →7π0 3f0 0 • Eprompt >700 MeV • 2fit < 27 • 2a0sel < 27 • d1< M(0) <d2 N(a0)/Ntot  1.5 %

  16. 0 2002 • data →3π0 7 f0 0 M (MeV) w(ω)=0.7370.007 w(oth. bckg.)=1.830.25 Other bckg. is mainly f0, other processes fixed  (°) (0)

  17. 0 2001 • data →3π0 7 f0 0 M (MeV) w(ω)=0.6920.005 w(oth. bckg.)=1.08 0.03  (°) (0)

  18. M(a0) (MeV) cos(f0) 0 2002 M(a0)(MeV) cos(f0) 2001 M(a0) (MeV) M(a0)(MeV)

  19. f0  Signal (a0 ) →7π0 3f0 0 • Eprompt >700 MeV • 2fit < 27 • 2a0sel < 27 • |M()-547.3| > 30 MeV • M(0) <d1 N(a0)/Ntot  2 % Cut 4 rejects a0 and 3 d1 Mπ (MeV) M(MeV) (f0)

  20. f0  →7π0 3f0 0 • Fit with 7, 0 and all other processes fixed, but f0 and 0 2002 2001 cos(ω) cos(ω) w(f0) = 1.46 0.02 w() = 5.04  0.67 w(f0)=1.400.02 w()=1.70  0.30 w(0) is not relevant  in the final sample there is no 0

  21. f0  2002 →7π0 3f0 0 cos(f0)  (°) ()  (°) (f0)

  22. f0  2001 →7π0 3f0 0 cos(f0)  (°) ()  (°) (f0)

  23. Further check on weights • Final check, by using all the weights together on the same sample, with a small signal (a0) content • Eprompt >700 MeV • 2fit < 27 • 2a0sel < 27 • |M(3)-547.3| > 30 MeV • Erec(3) < 340 MeV

  24. Check on weights 2002 →7π0 3f0 0 2fit 2fit E (MeV) M (MeV) 12(°) cos(0) cos(f0)  (°) (0)

  25. Summary of weights • In order to evaluate systematics on weigths, we repeated the fit on some other variables and compare the results

  26. Old cuts • Eprompt > 700 MeV • Etot > 900 MeV • 2fit < 27 • 2a0sel < 27 • |M()-547.3| < 30 MeV • E() < 340 MeV • 2II fit < 33 • M(0) < d1 • Mππ(f0 hyp.) < 760 MeV • Residual 3 contamination around Mπ  1020 MeV • In order to reduce the (7) background, we would like to harden cut 7. • Cut 8 introduces a dependence of the efficiency on the 0 mass • 00mass for f0 in MC is simulated with the fit to 2000 data, then cut 9 is not reliable • Cuts 2 and 4 are not necessary anymore

  27. New cut to reject  • residual →3 events are concentrated around Mπ  1020 MeV • Cut on the energies of the three most energetic clusters E1+E2+E3 < 980 MeV →3 E1+E2+E3 (MeV) M(MeV)

  28. Old cut Cut on 2IIfit • Nseg/N back • cut * cutxNseg/Nback Signal (a0) →7π0 3f0 New cut Cut on 2IIfit cut 2IIfit Old cut: 2IIfit < 33 New cut: 2IIfit < 24 2IIfit < 18 2IIfit < 21 2IIfit < 24 2IIfit < 27 M (MeV)

  29. tot Mπ (MeV) π0 cut Old cut |M| (MeV) M(MeV) ~ 30% drop in efficiency

  30. new old 000      New π0 cut Exploit the angle between the ’s from the π0 of the  ω7 f03 a0  Old cut New cut d2 d1 |M| (MeV) |M|-d1 (MeV) New cut: M(0) < d1 .OR. M(0) > d2 .OR. (ω)<30° .OR. (ω)>60° M(MeV)

  31. New cut New f0 cut • * is the angle between the non associated  and the flight direction of , in the  rest frame Old cut cos(*) |cos(*)|<0.8 |cos(*)|<0.65 |cos(*)|<0.5 M (MeV) a0  f0

  32. New f0 cut • data ω7 f03 a0  is the angle between the 2  associated to the 0 in the 0 hypothesis Cut :  > 42° (0)

  33. Eprompt > 700 MeV 2fit < 27 |M()-547.3| < 30 MeV E1+ E2+ E3 < 980. MeV 2II fit(a0) < 24 M(0) < d1 .OR. M(0) > d2 .OR. (ω)<30° .OR. (ω)>60° |cos*(ω)| < 0.8 (0) > 42° New cuts to reduce 3 “ 7 “ 0 “ f0

  34. Efficiency Old analysis New analysis M (MeV) (Tr., Filfo, Evcl, preselection not included) Efficiencies still to be checked

  35. Efficiency Efficiencies averaged over the whole M spectrum 1. To be checked with data 2.+3. Check done with the min bias sample (Camilla’s sample): 1495 events selected, all 1495 pass both FILFO and EVCL, but better check needed, about 5% of our final sample is missing in the min bias one • In the old analysis i  64%, but we have moved the angular cut (21°) in the preselection • Old analysis: tot = 32%

  36. Efficiency matrix • To be used to fit the spectrum to the various models • Takes into account of the smearing due both to mass resolution and to photon pairing • According to MC  14% of wrong pairings Mrec (MeV) Mgen (MeV)

  37. Check of pairing on data • Data • Right p. • Wrong p. • 2sel is the difference between the first and the second photon combination for the a0 hypothesis • Two component (right and wrong pairing) fit to the 2sel distribution of the data (final sample) • Right and wrong pairing shapes from MC wrong pairings = (11.5 ± 0.70) % 2sel

  38. Final sample Other background (0, , KK,…) negligible

  39. Final sample • data ω7 f0 3 2002 2001 Mπ (MeV)

  40. Final sample • data ω7 f0 3 Bkcg subtracted 2001+2002 Mπ (MeV)

  41.  0  • data ω7 f0 3 Final sample cos cos

  42. Final sample M (MeV) M (MeV)

  43. Conclusions • New analysis scheme: efficiency vs π0 invariant mass became flatter than in the past • Background evaluation: weighting procedure seems to work  ~ 55% background to be subtracted from the final sample • Efficiency evaluation: still preliminary, other checks needed  smearing matrix • Systematics evaluation on analysis cuts is in progress • To do: evaluation of other systematic effects (MC energy scale correction, photon efficiency curves, accidentals, …) Fit(s) of the spectrum to get the a0 parameters and the Br(0)

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