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Status of the pp ee analysis

Status of the pp ee analysis. Mauro Raggi, LNF INFN 29 th August 2013 NA48/2 rare decay session NA62 Collaboration meeting Liverpool. Outline. Introduction to pp ee decay Status of the MC generators The CMC DE generator vs theory Review of the analysis strategy

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Status of the pp ee analysis

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  1. Status of the ppee analysis Mauro Raggi, LNF INFN 29thAugust 2013 NA48/2 rare decay session NA62 Collaboration meeting Liverpool

  2. Outline • Introduction to ppee decay • Status of the MC generators • The CMC DE generator vs theory • Review of the analysis strategy • List of cuts Data and MC sample • BG evaluation technique • Likelihood method • Meeg cut and side band evaluation • Data MC comparison (ppee IB) • Resolutions and energy scales (charged neutral and global) • Mee resolution vsmee • Measurement of the Kaon Flux • BG evaluation in K2pDg • Trigger efficiency • BR values and systematic checks Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  3. Introduction to ppeedecay • The interference thanks to the possibility of measuring the plane of polarization of the e+e- pair is splitted into 3 terms: • IB/E, IB/M and E/B. • IB/M cancels when integrated over f as inppg, while E/B is only non-zero if CP violation is allowed. • Short and long distance parity violation contributions • Theoretical paper on ppeeare currently: • H. Pichl, ``K --> pi pi0 e+ e- decays and chiral low-energy constants,'’Eur. Phys. J. C 20, 371 (2001) [arXiv:hep-ph/0010284]. • L. Cappiello, O. Cata, G. D'Ambrosio and D. GaoEur. Phys. J. C (2012) 72:1872 • Never observed so far Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  4. BR IB isospin breaking correction Cut IB Pub. IB isospin Cut IB stand IB isospin The isospin breaking correction only changes the absolute value of the BR (-2%) not the shape of the Q distribution. Values are not published (G. D’Ambrosio private communication) Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  5. DE matrix element New set of form factors including unknown parameters From NA48/2 K±->p±p0g While Need to implement the T3 components Combination are the same as K±->p±p0g Thanks to P. Massarotti Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  6. Table of comparison MC theory Both IB and DE generators have been implemented in a private version of CMC007 For both components all 2003 MC sample has been generated with a statistics which exceeds 10 time the data one. Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  7. Analysis strategy • Use only the full 2003 data sample (SS0-1-2-3) • Use p+p0D(g)IB as normalization channel • Use: (1Vtx or 2Vtx or 1TrkP) as trigger sample • Perform the BRIB and possibly charge asymmetry measurements • Leave the enlargement of the sample and P violation for final result Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  8. Analysis definitions cuts (presel) • GoodVertex • -1000 < ZVTX< 8000 • NVTXtrk = 3 • GoodTrack • TrackQual>0.75 new • 2 GeV<TrackP< 60 GeV • 12 cm <RDCH1<135 cm • 12 cm <RDCH4<135 cm • Ddead > 2 cm • Track to trackdist > 2cm • GoodClusters • 2Gev < Ecl <60 GeV • accep(LKR) routine for geometricalacceptance • Cluster to cluster > 10cm • Cluster status <4 new Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  9. Common preselection • Preselectioncuts (common to PPD and signalanalysis) • NgoodVertex=1 • 3 < NgoodCluster < 8 • 3 < NgoodTracks < 8 • Ellipse 3pc cut • 116ns < Track time <154ns new! • 3 goodtrack are the sameused in vertexfitting Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  10. Signal selection • ngoodCl ≥4 • Nelectrons =2 E/P>0.85 new • Npions =1 E/P<0.85 • Ngammas =2 cluster with no associatedtrack &Ecl>3 GeV • COG < 2 cm • abs(ETOT-pk)< 6 GeV • abs(Mpi0-MPI0PDG)<10 MeV • Mee > 0.001022GeV • Distance of electrons @ DCH1 > 0.25againstconversions • Total charge of electrons = 0 • abs(Meeg-MPI0PDG)>0.005) cut on Dalitzdecay mass • abs(MK-MKPDG) < 10 MeV Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  11. Data MC comparison ppee Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  12. MK for data and MC (no BG sub) • Data MC comparison is non good due to 10% BG in the data sample • MK(MC) • media = 493.30 MeV Sigma = 5.6 MeV • MK(data) • media = 492.69 MeV Sigma = 5.85 MeV Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  13. MK for data and MC (BG sub) • Data MC comparison is good after BG subtraction in the data sample • MK(MC) • media = 493.30 MeV Sigma = 5.6 MeV • MK(data) • media = 493.29 MeV Sigma = 5.37 MeV Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  14. ZV data MC for signal Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  15. Data MC Meeno BG sub • Region above 100 MeV dominated by p+p0p0D BG • Bad agreement between data and MC Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  16. Data MC Mee BG sub • Good agreement in between D’Ambrosio and data • Data peak at 120MeV due to 3PD BG almost disappeared • Is the remaining discrepancy due to DE events? Or only insufficient MC statistics in 3pD? Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  17. BG estimate signal Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  18. Final set of cuts except MK • Integrating in the mass plot • BG(3PD)= 190.5±11 • BG(2PD)= 100±5 Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  19. Flux normalization • Use the fluxmeasurement and BRs to estimate BG value • Scale the MC to: NToT(BG)=Kfluxx Acc(BG) x Eff x BR(BG) • Compute the integral in the region MK±10MeV • BG(3PD)= 192±12.5stat ± 6ext • BG(2PD)= 75±10stat ±2.4ext Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  20. BG estimate summary table • The BG measurementsagreeverywell on the 3PD • The value for PPD isnotsoogood due to low MC statistics in the plot • The valuewewill use for the BG subtractionis: • 280±17stat±7syst • The systematicassignedis the 0.5*differencebetween the 2 estimates 10 Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  21. Flux measurement Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  22. The Kaon flux measurement • Used the decay K±->p±p0D(g) (PPD) means K±->p±ge+e-(g) • Same trigger chain of the signal • Very similar final state in the charged trigger (e+e-p+) • MonteCarlo generator used: • According to Evgueni suggestion using the KLOE generator (CMC 51) • 1 times full 2003 data set 222 Million events generated run by run • 165 in the ZV region 1.3 time the data • Normalization BR used in the calculation: • BR(K->2p(g))xBR(p->Dalitz)=(20.66*1.174)x10-2=(2.425±0.073)x10-3 • No cut applied to minimum E*g assuming that generator is fine • Flux measurement formula: • (NPPD - NBGPPD)/(ePPDx AccPPDx BRPPD) Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  23. PPD selection cuts • N electrons = 2 (0.9<E/p) with different charges • Pion charged = 1 (E/p<0.85) • N gammas = 1 (no ass cluster) • COG < 2 cm • abs(M(eeg)-MPI0(PDG)) < 10 MeV • Distance of e+e- tracks at DCH1 > 0.25 cm • abs(ETOT-PK)< 6 GeV • Track and clusters in 5ns (data only) • abs(MK-MK(PDG)) < 10 MeV • T*p > 85 MeV • Trigger (2VTX or 1VTX or 1TRKP) Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  24. T*p PPD data BG estimate • Unknown BG source: • NBG=65*(130-85)*4+30*(140-130)*4+734=13634 < 0.1% • Systematic on the flux measurement (0.1%) • Km3D BG from MC estimate (subtracted from data) • NBG=7109 Km3D 65 events/bin Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  25. Data MC for PPD selection Data Mass fit results Mean 493.09 MeV Sigma 3.83 MeV MC Mass fit results Mean 493.18 MeV Sigma 3.93 MeV Mass are very close to each other <100 KeV They are apart from the PDG by 0.5 and 0.4 MeV Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  26. T*p data MC for PPD Data T*p fit Mean 1085.56 ±1.23x10-6Sigma 3.83 MeV MC T*p fit Mean 108.587 MeV Sigma 3.91 MeV The T*p is perfectly on it’s place 108.5 The difference in data to MC is order 30KeV only The scale of the spectrometer is really in the right place! Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  27. Flux calculation results 2003 • KFlux=(NPPD - NBGPPD)/(ePPDx AccPPDx BRPPD)=(7.766±0.23)x1010 • Error completely dominated by external error dBR(p0D)=3% • BG in PPD sample set to 0 and added 0.1% systematic Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  28. Trigger efficiency measurement Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  29. General remarks on trigger • Control trigger : CPRE & !WDOG (TRGW) • Sample Trigger : 1VTX or 2VTX or 1TRK-P • 1TRK-P: NT-PK (LvL 0) and 1TRK-P (Mfake<475 MeV) • We expect the trig effto be different for the 2 decays due to 1TRK-P component in fact: • The ppee has 1 more cluster (NT-PK more efficient) • The ppee has lower value of T*p (Mfake) 1TRK-P is more efficient • In the MC the efficiency of LvL0 NT-PK is not simulated correctly • Problems of low statistics for signal measurement (27 events) • Try to use BG enriched sample (330 events sample) • Cannot use efficiency measured using PPD Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  30. Trigger efficiency analysis • Control trigger : CPRE & !WDOG (TRGW) • Sample Triggers: (1VTX or 2VTX or 1TRKP) (1VTX or 2VTX) • Measured with both the signal and the normalization in data and MC with loose and tight cuts • Difference in between loose and tight cuts is < 0.1% in MC • Data shows the same agreement at least in PPD • Can we use the data loose cuts determination for trigger efficiency? Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  31. Trigger efficiency MC vs data PPD • Different absolute value due to bad simulation of NT-PK but same behavior as function of Mee (Mee>2MeV) • Difference increasing at low Mee DataMC Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  32. Trigger efficiency ppeevs PPD MC • This difference is expected and due to MBX cut is small due to electrons in the MC • NT-PK is not simulated • The difference in data comes from NT-PK (3 clus PPD 4clus ppee) PPD(MC) ppee(MC) Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  33. Trigger efficiency loose to tight Efficiency comparison for ppee MC. Tight 98.95 Loose 99.07 389197 control sample events247440control sample events Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  34. Total BR result for 2003 raw value • Stat: Includes only the error on Nppee • External error: only Kflux coming from BR(p0)D • Trig: 0.65% error on 98.7% measured from data loose selection • What about DE? Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  35. DE component fitting Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  36. DE and IB in the Mee spectrum • Generated 13 Million events of ppee DE run by run • 9.6M in ZV acceptance • Acceptance measurement: • Acc(DE) = (3.876± 0.006)% • Acc(IB) = (0.782± 0.0015)% • The ratio of acceptance is Acc(DE)/Acc(IB)~5 which meansthat the DE is a order ~6% in the data (according to D’Ambrosio prediction 1/77*BR(IB) ) • Using G. D’Ambrosio theoretical BR leads to a BG evaluation of: • N(ppee)DE =155±20 events ( includes a 10% error on the BR(DE) ) • This number can be subtracted as a BG to get the N(ppee)IB • N(ppee)IB =N(ppee)TOT - N(ppee)DE = 2540-155 = 2385 IB events Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  37. Fitting the DE • Fitting the DE using Mee is quite hard for different reasons: • Distributions of Mee is really very similar much more that in ppg • Regions in which the DE is dominant are populated by 10% BG • The low statistics does’nt allow to have a very hard selection cuts • Seems that our acceptance spoils the difference even more After the selection Before the selection IB MC GENDE MC GEN IB MC GENDE MC GEN Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  38. Real life is even harder… Mee IB MC RECDE MC REC Reconstructed MC after correct DE normalization including higher acceptance factor 5 IB MC DE MC T*p IB MC DE MC Situation in T*pi looks a bit better but BG has to be taken into account… Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  39. T*p BG distributions 3pD MC DE MC Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  40. Results of fitting attempts Fit with 3 MC only: IBMC,3pD,2pDg MC IB frac (86.9±2.2)% 2445±62 ev BG 3pD frac (9.39±1.2)% 264±34 evBG 2pDg frac (3.7±1.0)% 104±28 ev Estimate from BG fit measurement are: NBG 3PD 190.5 ± 13.0 NBG 2PD 100.0 ± 9.8 Residuals look quite good even without the DE. The enhancement of the 3PD bg +74 events is masking the presence of the DE Fits with DE does’nt converge! Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  41. Systematic checks Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  42. Cut variation systematics • I did many cuts variation that you can see in my April talk • MK, Mp, COG, Mee, Meeg,Egmin, PeMin • No effect has been seen except for the PeMIN • This has been redone • This misses still the correction of trigger efficiency point to point Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  43. Minimum electron energy Max difference (4.34-4.24)/4.24=2.3% max difference Part of this will be due to absence of trigger efficiency I propose to use the 0.5*Max Difference=1.2% systematic I’ll investigate this more soon. Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  44. Errors summary table Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  45. Preliminary BR result • Theoretical prediction from G. D’Ambrosio et al (Eur. Phys. J. C (2012) 72:1872): • BR(ppee)IB= 4.19 x 10-6 IB only no isospin correction (PUBLISHED) • BR(ppee)IB= 4.10 x 10-6 IB only isospin breaking correction (PRIVATE) • In the IB only BR we considered DE as a BG we subtracted: • DE = Kflux*AccDE*Eff*BRDE(Th) =155±20 events (+0.8% syst or EXT) Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  46. Conclusions • We performed the first measurement of the BR for K±->ppee • We reached less than 1% agreement between the two analysis • Total and IB only BR can be measured • The Background is very well under control (~9.6%) • First attempt to fit DE is showing many obstacles • Small difference in the spectrum • BG domination in favored DE regions • Low statistics in the data sample • The result is in good agreement with isospin breaking corrected theory • First systematic check does’nt reveal important contribution • Trigger efficiency to be added to systematic check routine Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  47. Thank you for your attention

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