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Biagio Di Micco17/07/2002 - Radiative Phi Decays Meeting 1  Status of the work Biagio Di Micco Università degli Studi di Roma 3.

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Presentation on theme: "Biagio Di Micco17/07/2002 - Radiative Phi Decays Meeting 1  Status of the work Biagio Di Micco Università degli Studi di Roma 3."— Presentation transcript:

1 Biagio Di Micco17/07/ Radiative Phi Decays Meeting 1  Status of the work Biagio Di Micco Università degli Studi di Roma 3

2 Biagio Di Micco17/07/ Radiative Phi Decays Meeting 2 Last Lu Feng’s results Evaluation of the upper limit Problem in the estimation of the background E min cut too strong Solution of the problem Montecarlo statistic needed Proposed way to generate Montecarlo statistic Analysis strategy Pass1 pre-analysis (signal efficiency and data selection) Determination of cuts to improve the analysis.

3 Biagio Di Micco17/07/ Radiative Phi Decays Meeting 3 Upper limit evaluated Lu Feng’s result Br(  PDG 2001 Theoretical prediction 5.5    CL 5    CL 4.5× % CL (2000) 1.8× % CL (2002) Crystal Ball preliminary via C and CP violation Br(  Lu Feng, KLOE memo n.267 March 2002 Lu Feng, KLOE note n.173 March    CL via weak interaction  

4 Biagio Di Micco17/07/ Radiative Phi Decays Meeting 4 Lu Feng’s results 1/2 Estimated background 59

5 Biagio Di Micco17/07/ Radiative Phi Decays Meeting 5 Lu Feng’s result 2/2 Background shapeMC signal shape The function is fitted with the method “Unbinned maximum likelihood” Data fit The shape of the background doesn’t match with which of the data 95% C.L.

6 Biagio Di Micco17/07/ Radiative Phi Decays Meeting 6 The background problem Estimated efficiency of the background N. of expected events But what about the upper limit on the 0 events samples? MC statistic too loose!!

7 Biagio Di Micco17/07/ Radiative Phi Decays Meeting 7 Montecarlo statistic needed to obtain N max < 1 We have them We don’t have them and they are too many for a simple generation (we must include selection cuts in the generator itself) We don’t have them but we can start generation now Channels not studied by Lu Feng (we don’t have the generator) Submitted to production

8 Biagio Di Micco17/07/ Radiative Phi Decays Meeting 8 Selection for  Ls KK Filtered events by EVCL  = 1.6 % All events K0 L flylenght Selected events : 10 6 K0 L decaying before beam pipe

9 Biagio Di Micco17/07/ Radiative Phi Decays Meeting 9 E min cut From the note

10 Biagio Di Micco17/07/ Radiative Phi Decays Meeting 10 M  distribution in the data E min > 130 MeV Without E min > 130 MeV

11 Biagio Di Micco17/07/ Radiative Phi Decays Meeting 11 Radiative photon selection criteria Data seems reproduce the signal )( ) ˆ ( 1     M Erad rad MM EE     To chose the combination that makes it minimum 2  We have 4 combinations for each event so the criteria biases the distribution of the background

12 Biagio Di Micco17/07/ Radiative Phi Decays Meeting 12 New criteria Before kinematic fitAfter kinematic fit  rad is the most energetic one

13 Biagio Di Micco17/07/ Radiative Phi Decays Meeting 13 M  distribution comparison MC  3   2 criteria Maximum energy criteria M  Mev/c 2 DATA

14 Biagio Di Micco17/07/ Radiative Phi Decays Meeting 14 Cuts choice Common to Lu Feng and my analysis > 3 total number of clusters after recover splitting 4 prompt clusters number (|t-l/c| < 5  t cos(  clusters ) < 0.93   > 15° E tot (prompt clusters) > 900 MeV Ptot < 110 MeV My cuts P cin-fit (  2 >  2 0 ) > < M  <170 E%cos(  ) plane cut E min > 50 MeV N  < M rin < 595 MeV/c 2

15 Biagio Di Micco17/07/ Radiative Phi Decays Meeting 15  2 cut DATA MC P(  2 >  2 0 ) Flat distribution as expected for good errors estimation Problems with MC perhaps bad estimation of the errors CUT: P(  2 >  2 0 ) > 0.01 Peak at small P  2 of the kinematical 3-C fit  MC = 99.5 %  DATA = 94.9 %

16 Biagio Di Micco17/07/ Radiative Phi Decays Meeting 16  0 content of the sample M  distribution of two photon in the event (6 combinations) DATA MC M  MeV/c 2 CUT: 110 < M  <170  MC = 62.3 %  DATA = 23.4 %

17 Biagio Di Micco17/07/ Radiative Phi Decays Meeting 17 Source of  0 sample M recoil   1 is the least non  0 energetic one Evidence for events:     ee  0 44 But they are not the only one To investigate more deeply M  MeV/c 2 M recoil of  rad

18 Biagio Di Micco17/07/ Radiative Phi Decays Meeting 18 No other strong evidence of decays in 2  M  MeV/c 2

19 Biagio Di Micco17/07/ Radiative Phi Decays Meeting 19 Correlation in the plane E-cos(  ) of the least energetic E (MeV) cos(  ) E (MeV) cos(  ) E (MeV) cos(  ) E (MeV)  MC = 96.5 %  DATA = 75.7 % CUT: E > 100 MeV OR cos(  ) < 0.8 cos(  )

20 Biagio Di Micco17/07/ Radiative Phi Decays Meeting 20 Distribution of E min Emin MeV CUT: E min > 50 MeV  MC = 97.0 %  DATA = 74.7 %

21 Biagio Di Micco17/07/ Radiative Phi Decays Meeting 21 Distribution of cos(  ) of the four photon DATAMC

22 Biagio Di Micco17/07/ Radiative Phi Decays Meeting 22 Number of photons with cos(  ) > 0.7  MC = 77.9%  DATA = 56.9 % N N CUT: N < 2

23 Biagio Di Micco17/07/ Radiative Phi Decays Meeting 23 Distribution of M  M  MeV/c 2 CUT: 505 MeV/c 2 < M  < 595 MeV/c 2 DATAMC  MC = 84.2 %  DATA = 25.8 %

24 Biagio Di Micco17/07/ Radiative Phi Decays Meeting 24 SUMMARY

25 Biagio Di Micco17/07/ Radiative Phi Decays Meeting 25 To do  Study the background with MC to evaluate expected events  submitted channels: wait for production  find kinematic cuts for  make generator  Try to improve the analysis  Increase  0 MC efficiency with 4-c kinematic fit to increase  0 resolution for the channel  Find the other sources of  0  do a 3  analysis to find other sources of background.  Evaluate systematic errors (  is affected by  unknown S matrix, experimental systematic effects)  Extend the analysis to all data   ee     ee


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