1. Biagio Di Micco  mass measurement Systematics on   mass measurement Biagio Di Micco

2.  mass measurement What we bless... The results actually presented at conferences have been blessed more than one year ago; Until now we preferred to not give further preliminary result to give directly the final result; In this way, large part of the work on systematic could not be shown until now. We are blessing all this work and we can discuss if give another preliminary result; Main part of these plots come from KLOE Memo n. 333

3. Biagio Di Micco  mass measurement Motivation M  = (547.311 ± 0.028 ± 0.032) MeV/c 2 Reaction used: p + d → 3 He +  High discrepancy with NA48! Using   3   from     p →  n : M  = (547.843 ± 0.030 ± 0.041 ) MeV/c 2 [ A, Lai et al., Phys. Lett. B 533 (2002) 196] The most precise measurements differ by 8s GEM is in good agreement with old measurements GEM result:

4. Biagio Di Micco  mass measurement Method and selection. f  hg (h  gg) f  p 0 g (p 0  gg) A kinemati fit is performed imposing energy-momentum conservation and time of flight of photons the energy momentum conservation imposes 4 constraints the energies of the three photons are over constrained and determined by the angles through the kinematic fit. h mass p 0 mass |t – r/c | < min(5  t,2ns) 50  <   < 130  the kinematic fit is performed on all combination and that with the smallest c 2 is retained. Selection c 2 < 35 At least 3 photons with the requirements: 3g final state

5. Biagio Di Micco  mass measurement 5 Measurement method constraints equation ● energy-momentum conservation ● t-r/c of clusters ● cluster position x,y,z ● cluster energies ● cluster times from e + e -  e + e - 86000 ev./run  = 3 MeV/c 2  = 39 MeV/c 2 before kin. fit after kin. fit the kinematic fit squeeze the distribution because of the very good angular resolution.  = 3 MeV/c 2 ●  s ● momentum ● vertex position measured quantities

6. Biagio Di Micco  mass measurement Dalitz plot The photons are ordered according their energies p0p0  2 < 35 DATA Accepted region E 1 < E 2 < E 3  cut h p 0 cut signal region

7. Biagio Di Micco  mass measurement DATA MC Fit of the gg invariant mass double gaussian for  0 single gaussian for  Fit to the invariant mass distribution

8. Biagio Di Micco  mass measurement Cuts Dalitz plot cut c 2 photon angle dependence azimuthal and polar angle; vertex position vertex position determination; DC – EMC global misalignment calorimeter energy response energy scale knowledge deviation from linearity fit distortion sqrt(s) systematic checks

9. Biagio Di Micco  mass measurement Dalitz cut systematic The cut on the Dalitz produces a small distortion on the invariant mass distribution that shifts the measured mass. The distortion is null in the limit of infinite resolution and can be easily corrected using MC.  The effect is evaluated using a toy MC that just generate  decays with a gaussian mass spectrum with  (DATA)

10. Biagio Di Micco  mass measurement Dalitz cut correction - slope 13 keV residual systematic corrected Toy MC Dalitz m MeV DATA 200 keV variation

11. Biagio Di Micco  mass measurement Dalitz cut correction - constant 11 keV systematic rms of the points without correction. mhmh MeV

12. Biagio Di Micco  mass measurement p 0 case M p MeV Slope cut Constant cut

13. Biagio Di Micco  mass measurement c 2 cut

14. Biagio Di Micco  mass measurement Angular dependence The 3 photons are boosted back in the  rest frame. The normal to the plane of the 3 photons is evaluated. vertical line   photon plane 15 keV rms normal 10 keV rms

15. Biagio Di Micco  mass measurement A sample of      has been used to determine shifts in the vertex position and displacement between DC and EMC. ++   The p + p - vertex is compared with that coming form e + e -  e + e -. The tracks are extrapolated from the vertex to the calorimeter, and compared with the cluster position. ++ Minimum approach point Vertex position and DC-EMC alignment

16. Biagio Di Micco  mass measurement Mis-determination of the I.P x   x eeee y   y eeee z   z eeee We keep the vertex from the tracking algorithm and compare it with the ee values event by event 2 normal dist. 1 normal distr. 2 normal dist.

17. Biagio Di Micco  mass measurement 2001 2002 The standard deviation respect to the zero value is taken as systematic displacement as a function of run n.

18. Biagio Di Micco  mass measurement 2002 EMC-DC displacement ++  x y z

19. Biagio Di Micco  mass measurement Global systematic Uncertainty on the mass values (fractional error)

20. Biagio Di Micco  mass measurement Energy response linearity deviation are 2% at most. Applying these correction we find: energy scale  m/m = 8  10 -6 (4 keV) lin. dev.  m/m = 7  10 -6 (4 keV) E clu = 0.994xE true – 0.2 MeV The same ppg sample can be used to check the energy response of the calorimeter, comparing the g energy evaluated from the pp tracks with the cluster energy. Different approach using f  p + p - p 0 (p 0  gg) The same result in the overlapping region (different g energy allowed by the kinematics)

21. Biagio Di Micco  mass measurement Global check of the method M fit = M input + (41 ± 3) keV/c 2    n.d.f  50pb -1 for each point linearity is perfect. A correction for the constant term is needed. To check possible distortions due to the algorithm itself. m  fit MeV

22. Biagio Di Micco  mass measurement Correction source The correction comes from a distortion of the energy distribution respect to the true value DUMMY (smearing of the true MC informations) GEANFI (Efit – Etrue)/s -(Efit-Etrue)/s This asymmetry is able to produce 30 keV correction on the mass out from the blessing

23. Biagio Di Micco  mass measurement GEANFI DUMMY SMEARING t=(Efit – Etrue)/s This effect produce a correction of -52 keV, to be conservative we assume 26 keV error for the moment. out from the blessing

24. Biagio Di Micco  mass measurement We can compute Smearing according the previous distribution. Dm h  30 keV

25. Biagio Di Micco  mass measurement Unluckily the residuals are not sensitive to these distortions. DATA MC-DUMMY GEANFI x y z E t out from the blessing

26. Biagio Di Micco  mass measurement Systematic summary p fit dist.

27. Biagio Di Micco  mass measurement Fit quality (data sample divided in 8 periods) hp0p0

28. Biagio Di Micco  mass measurement Fit results

29. Biagio Di Micco  mass measurement sqrt(s) correction The mass shows an high sensitivity to the sqrt(s) value.  m   m  × 10 -3  m   m  × 10 -3

30. Biagio Di Micco  mass measurement sqrt(s) determination The absolute scale of the  s is obtained fitting the cross section e + e -  K s K L (f line shape). The fit takes into account the ISR effect and the phase space factor of the KK couple. m f (CMD-2) = 1019.483 ± 0.011 ± 0.025 MeV The ratio m f (CMD-2)/m f (KLOE) is used to set the absolute  s scale.

31. Biagio Di Micco  mass measurement sqrt(s) not affected estimate: D PDG = 1s

32. Biagio Di Micco  mass measurement p 0 gg 2005 m(h  p 0 gg) Br(    stat  syst    Using the Br evaluated on 2002 data. ½ 2005 statistics 600 pb -1 MC shape from rad04 bkg  1s signal 434 pb -1

33. 33 Results and systematics Systematic due to the vertex position determination have been also evaluated, the sqrt(s) is calibrated by fitting the  line shape. M(  0 ) = ( 134990  6 stat  30 syst ) keV M(  0 ) PDG = ( 134976.6  0.6 ) keV  NA48 compatibility: 0.24   Independent measurement with the        decay mode in progrees: m       MeV/c   very preliminary fully in agreement with the  channel  M(  ) = ( 547822  5 stat  69 syst ) keV KLOE PRELIMINARY m(f) = 1019.483 ± 0.011 ± 0.025 CMD-2 Phys. Lett. B578, 285 the energy calibration has been determined using      and e + e -  events, the calorimeter calibration is know at better than 2%  m/m = 11  10 -6 (6 keV) on the  mass. radiative return and threshold effects included in the fit

34. Results and systematics Systematic due to the vertex position determination have been also evaluated, the sqrt(s) is calibrated by fitting the  line shape. M(  0 ) = ( 134990  6 stat  30 syst ) keV M(  0 ) PDG = ( 134976.6  0.6 ) keV  Systematics dominated by √s knowledge  NA48 compatibility: 0.24   Cross check with  →       decay mode: m       MeV/c  M(  ) = ( 547822  5 stat  69 syst ) keV KLOE PRELIMINARY m(f) = 1019.483 ± 0.011 ± 0.025 CMD-2 Phys. Lett. B578, 285