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Introduction Analysis Results Conclusions

Introduction Analysis Results Conclusions. Status of       analysis. F. Ambrosino T. Capussela F. Perfetto. Frascati 12 March 2008. Status of    analysis. Outline. Repeat the analysis with h mass constraint before photon’s pairing

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Introduction Analysis Results Conclusions

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  1. Introduction Analysis Results Conclusions Status of  analysis F. Ambrosino T. Capussela F. Perfetto Frascati 12 March 2008 Status of  analysis

  2. Outline • Repeat the analysis with h mass constraint before photon’s pairing • Review the correction to the photon efficiency • Look at Data /MC comparison for cmin2 Frascati 12 March 2008 Status of analysis

  3. OLD approach: • 7 and only 7 pnc with 21° <  < 159°and E> 10 MeV • g > 18° • Kin Fit with no mass constraint • P(2) > 0.01 • 320 MeV < Erad < 400 MeV AFTER PHOTON’S PAIRING • Kinematic Fit with h and p0mass constraints (on DATA Mh =547.822 MeV/c2 ) • NEW approach: • 7 and only 7 pnc with 21° <  < 159°and E> 10 MeV • g > 18° • Kin Fit with h mass constraint (onDATAMh = 547.822 MeV/c2 ) • P(2) > 0.01 • 320 MeV < Erad < 400 MeV AFTER PHOTON’S PAIRING • Kinematic Fit with p0mass constraint Sample selection Frascati 12 March 2008 Status of analysis

  4. Using the same cuts on c min and Dc : OLD - NEW Pur  75.4% Pur  82.2% Low purity Medium I purity Pur  84.5% Pur  91% Pur  92% Pur  96.3% Medium II purity Medium III purity Pur  94.8% Pur  98% Pur  99% Pur  97.6% High purity Frascati 12 March 2008 Status of analysis

  5. The slope in the efficiency shapes : OLD - NEW De 8% De 8% Low purity Medium I purity De 14% De 14.6% De22.3% De 21% Medium II purity Medium III purity De 25% De 25.3% De 26% De 26% High purity Frascati 12 March 2008 Status of analysis

  6. OLD - NEW RMS = 0.1632 RMS = 0.1169 Frascati 12 March 2008 Status of analysis

  7. Efficiency Correction to the photon efficiency is applied weighting the Montecarlo events for the Data/MC photon efficiency ratio ≈ 1  exp(E/8.1) Frascati 12 March 2008 Status of analysis

  8. Introduction Analysis Results Conclusions Efficiency (I) Correction to the photon efficiency is applied weighting the Montecarlo events for the Data/MC photon efficiency ratio ≈ 1  exp(E/8.1) P1 = 0.001601 P1 = 0.001258 P1 = 0.002014 P1 = 0.001876 Low purity High purity P1 = 0.001623 P1 = 0.001692 Medium II purity Frascati 12 March 2008 Status of analysis

  9. Introduction Analysis Results Conclusions Recoil is the most energetic cluster. In order to match every couple of photon to the right0we build a2-like variable for each of the 15 combinations: Photons pairing With: is the invariant mass ofi0for j-th combination = 134.98 MeV is obtained as function of photon energies Frascati 12 March 2008 Status of analysis

  10. Introduction Analysis Results Conclusions Energy resolution Frascati 12 March 2008 Status of analysis

  11. Introduction Analysis Results Conclusions Data – MC RMS A further check can be done comparing the energies of the two photons in the pion rest frame as function of pion energy A data MC discrepancy at level of 12 % is observed. Frascati 12 March 2008 Status of analysis

  12. Conclusions • We are ready to fit a and to evaluate the systematical errors in the NEW approach. • We have to resolve the Data MC discrepancy on cmin2 Frascati 12 March 2008 Status of analysis

  13. Introduction Analysis Results Conclusions 3in chiral theory The decay occours primarily on account of the d-u quark mass differences and the result arising from lowest order chiral perturbation theory is well known: And, at l.o. With: A good understanding of M(s,t,u) can in principle lead to a very accurate determination of Q: Frascati 19 Luglio 2007 Dalitz plot analysis of with the KLOE experiment

  14. Introduction Analysis Results Conclusions The dynamics of the 0 0 0 decay can be studied analysing the Dalitz plot distribution. The Dalitz plot density ( |A|2 ) is specified by a single quadratic slope : |A|2 1 + 2z with: Dalitz plot expansion Z  [ 0 , 1 ] Ei = Energy of the i-th pion in the  rest frame.  = Distance to the center of Dalitz plot. max = Maximun value of . Frascati 19 Luglio 2007 Dalitz plot analysis of with the KLOE experiment

  15. Introduction Theoretical tools Results Conclusions Dalitz plot expansion Frascati 19 Luglio 2007 Dalitz plot analysis of with the KLOE experiment

  16. Introduction Analysis Results Conclusions Dalitz expansion: theory vs experiment [1] Gasser,J. and Leutwyler, H., Nucl. Phys. B 250, 539 (1985) [2] Kambor, J., Wiesendanger, C. and Wyler, D., Nucl. Phys. B 465, 215 (1996) [3] Borosoy B., Niler R. hep-ph/0510384 v2 (2005) Frascati 19 Luglio 2007 Dalitz plot analysis of with the KLOE experiment

  17. Introduction Analysis Results Conclusions Sample selection • The cuts used to select:  0 0 0are: • 7 and only 7 prompt neutral clusters with 21° < <159° • and E> 10 MeV • Opening angle between each couple of photons > 18° • Kinematic Fit with no mass constraint • P(2) > 0.01 • 320 MeV < Erad < 400 MeV (after kin fit) The overall common selection efficiency (trigger, reconstruction, EVCL) is  = (30.30  0.01)% With these cuts the expected contribution from events other than the signal is < 0.1% Frascati 19 Luglio 2007 Dalitz plot analysis of with the KLOE experiment

  18. Introduction Theoretical tools Results Conclusions Sample selection Frascati 19 Luglio 2007 Dalitz plot analysis of with the KLOE experiment

  19. Introduction Analysis Results Conclusions Recoil is the most energetic cluster. In order to match every couple of photon to the right0we build a2-like variable for each of the 15 combinations: Photons pairing With: is the invariant mass ofi0for j-th combination = 134.98 MeV is obtained as function of photon energies Frascati 19 Luglio 2007 Dalitz plot analysis of with the KLOE experiment

  20. Introduction Analysis Results Conclusions Energy resolution Frascati 19 Luglio 2007 Dalitz plot analysis of with the KLOE experiment

  21. Introduction Analysis Results Conclusions Matching to s • Cutting on: • Minimum2 value • 2 between “best” and “second” combination One can obtain samples with different purity-efficiency Purity = Fraction of events with all photons correctly matched to0’s Frascati 19 Luglio 2007 Dalitz plot analysis of with the KLOE experiment

  22. Introduction Analysis Results Conclusions Samples Pur  75.4% Eff  30.3 % No cut on 2 and 2 Low purity Pur  84.5% Eff  22 % 2 < 10 2 > 1.2 Medium purity I Pur  92 % Eff  13.6 % 2 < 5 2 > 3 Medium purity II Pur  94.8% Eff  9.2 % 2 < 3 2 > 4 Medium purity III Pur  97.6% Eff  4.3 % 2 < 2 2 > 7 High purity Frascati 19 Luglio 2007 Dalitz plot analysis of with the KLOE experiment

  23. Introduction Theoretical tools Results Conclusions Efficiency Low purity Frascati 19 Luglio 2007 Dalitz plot analysis of with the KLOE experiment

  24. Introduction Theoretical tools Results Conclusions Efficiency Medium II purity Frascati 19 Luglio 2007 Dalitz plot analysis of with the KLOE experiment

  25. Introduction Theoretical tools Results Conclusions Efficiency High purity Frascati 19 Luglio 2007 Dalitz plot analysis of with the KLOE experiment

  26. Introduction Analysis Results Conclusions The problem of resolution Reconstructed Phase space Low Purity High Purity Frascati 19 Luglio 2007 Dalitz plot analysis of with the KLOE experiment

  27. Introduction Analysis Results Conclusions Second kinematic fit Once a combination has been selected, one can do a second kinematic fit imposing0 mass for each couple of photons. Frascati 19 Luglio 2007 Dalitz plot analysis of with the KLOE experiment

  28. Introduction Analysis Results Conclusions Fit procedure The fit is done using a binned likelihood approach We obtain an extimate by minimizing Where: • ni= recostructed events • i= for each MC event (according pure phase space): • Evaluate its ztrue and its zrec (if any!) • Enter an histogram with the value of zrec • Weight the entry with 1 + 2ztrue • Weight the event with the fraction of combinatorial background, for the signal (bkg) if it has correct (wrong) pairing Frascati 19 Luglio 2007 Dalitz plot analysis of with the KLOE experiment

  29. Introduction Analysis Results Conclusions Results on MC We have tested the fit procedure on MC by generating samples with different values of the parameter and looking at the result of our fit for these samples: Frascati 19 Luglio 2007 Dalitz plot analysis of with the KLOE experiment

  30. Introduction Analysis Results Conclusions Results on MC (Low Pur) Fitted region (0,0.6) Fitted region (0,0.7) Fitted region (0,0.8) Fitted region (0,1) Frascati 19 Luglio 2007 Dalitz plot analysis of with the KLOE experiment

  31. Introduction Analysis Results Conclusions Results on MC (Medium II Pur) Fitted region (0,0.6) Fitted region (0,0.7) Fitted region (0,0.8) Fitted region (0,1) Frascati 19 Luglio 2007 Dalitz plot analysis of with the KLOE experiment

  32. Introduction Analysis Results Conclusions Results on MC (High Pur) Fitted region (0,0.6) Fitted region (0,0.7) Fitted region (0,0.8) Fitted region (0,1) Frascati 19 Luglio 2007 Dalitz plot analysis of with the KLOE experiment

  33. Introduction Analysis Results Conclusions Data sample We have analyzed Lint = 418 pb1 of eecollisions collected in the 20012002 data taking period N1 = 1.4179  0.0012 Mevts Low purity N2 = 1.0292  0.0010 Mevts Medium I purity N3 = 0.6459  0.0008 Mevts Medium II purity N4 = 0.4453  0.0007 Mevts Medium III purity N5 = 0.2123  0.0005 Mevts High purity Frascati 19 Luglio 2007 Dalitz plot analysis of with the KLOE experiment

  34. Introduction Analysis Results Conclusions Analysis on data Trying some more systematics checks on the fitting range we got in BIG trouble… Frascati 19 Luglio 2007 Dalitz plot analysis of with the KLOE experiment

  35. Introduction Analysis Results Conclusions Linearity of DATA / MC ratio Check linearity of DATA/MCreco using for MC pure phase space… Nothing really strange @ high purity… Frascati 19 Luglio 2007 Dalitz plot analysis of with the KLOE experiment

  36. Introduction Analysis Results Conclusions Linearity of DATA / MC ratio (II) Idea: check linearity of DATA/MCreco using for MC pure phase space… But @ low purity = High statistics… Frascati 19 Luglio 2007 Dalitz plot analysis of with the KLOE experiment

  37. Introduction Analysis Results Conclusions A possible explanation_ The edge of the flat part of the phase space depends in the value of the eta mass. What if its value on data is larger than the nominal one ? Frascati 19 Luglio 2007 Dalitz plot analysis of with the KLOE experiment

  38. Introduction Analysis Results Conclusions To understand the effect we used a toy MC to generate 1200000 events with different eta masses: Sample 1 : M = 547.30 MeV Sample 2 : M = 547.822 MeV We observe that when the input mass value is used to build “z” variable the phase space shape does not change. But if one uses M = 547.30 MeV to build the “z” variable for sample 2 big deviations are observed…….. A toy MC Z2(547.8)/Z1(547.3) Frascati 19 Luglio 2007 Dalitz plot analysis of with the KLOE experiment

  39. Z2(547.3)/Z1(547.3) Introduction Analysis Results Conclusions To understand the effect we used a toy MC to generate 1200000 events with different eta masses: Sample 1 : M = 547.30 MeV Sample 2 : M = 547.822 MeV We observe that when the input mass value is used to build “z” variable the phase space shape does not change. But if one uses M = 547.30 MeV to build the “z” variable for sample 2 big deviations are observed…….. A toy MC Z2(547.8)/Z1(547.3) Frascati 19 Luglio 2007 Dalitz plot analysis of with the KLOE experiment

  40. Introduction Analysis Results Conclusions If the effect is given by the eta mass, correcting for it now all sample should exhibit good linearity for the ratio DATA/MCrec (phase space) Linearity @ Low purity Frascati 19 Luglio 2007 Dalitz plot analysis of with the KLOE experiment

  41. Introduction Analysis Results Conclusions If the effect is given by the eta mass, correcting for it now all sample should exhibit good linearity for the ratio DATA/MCrec (phase space) Linearity (II) @ High purity Frascati 19 Luglio 2007 Dalitz plot analysis of with the KLOE experiment

  42. Introduction Analysis Results Conclusions Results on data Let us look at what happens now… …..we gained greater stability with respect to the range and purity. Frascati 19 Luglio 2007 Dalitz plot analysis of with the KLOE experiment

  43. Introduction Analysis Results Conclusions We performed a kinematic fit constraining the mass (M = 547.822 MeV) Third kinematic fit Frascati 19 Luglio 2007 Dalitz plot analysis of with the KLOE experiment

  44. Introduction Analysis Results Conclusions The systematic check • This procedure relies heavily on MC. • The crucial checks for the analysis can be summarized • in three main questions: • Is MC correctly describing efficiencies ? • Is MC correctly describing resolutions ? • Is MC correctly estimating the “background” ? Frascati 19 Luglio 2007 Dalitz plot analysis of with the KLOE experiment

  45. Introduction Analysis Results Conclusions Efficiency (I) Correction to the photon efficiency is applied weighting the Montecarlo events for the Data/MC photon efficiency ratio ≈ 1  exp(E/8.1) Frascati 19 Luglio 2007 Dalitz plot analysis of with the KLOE experiment

  46. Introduction Analysis Results Conclusions Efficiency (I) Correction to the photon efficiency is applied weighting the Montecarlo events for the Data/MC photon efficiency ratio ≈ 1  exp(E/8.1) Low purity High purity Medium II purity Frascati 19 Luglio 2007 Dalitz plot analysis of with the KLOE experiment

  47. Introduction Analysis Results Conclusions Efficiency (II) Further check is to look at the relative ratio between the different samples: N2/N1 obs = .7258 ± 0.0004 N3/N1 obs. = .4556 ± 0.0004 N4/N1 obs. = .3140 ± 0.0004 N5/N1 obs. = .1498 ± 0.0003 N2/N1 exp. = .7263 ± .0002 N3/N1 exp. = .4497 ± .0002 N4/N1 exp. = .3048 ± .0002 N5/N1 exp. = .1431 ± .0001 Frascati 19 Luglio 2007 Dalitz plot analysis of with the KLOE experiment

  48. Introduction Theoretical tools Results Conclusions Efficiency (III) Frascati 19 Luglio 2007 Dalitz plot analysis of with the KLOE experiment

  49. Introduction Analysis Results Conclusions Resolution (I) A first check on resolution is from pion mass distribution Frascati 19 Luglio 2007 Dalitz plot analysis of with the KLOE experiment

  50. Introduction Analysis Results Conclusions Resolution (II) The center of Dalitz plot correspond to 3 pions with the same energy (Ei = M/3 = 182.4 MeV). A good check of the MC performance in evaluating the energy resolution of0 comes from the distribution of E0  Ei for z = 0 Frascati 19 Luglio 2007 Dalitz plot analysis of with the KLOE experiment

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