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Open issues of the pp ee analysis

Open issues of the pp ee analysis. Mauro Raggi, LNF INFN 30 th August 2014. Outline. Possible analysis strategies Addition BG suppression BG evaluation for different strategy Radiative correction treatment Signal (no correction vs Photos+coulomb )

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Open issues of the pp ee analysis

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  1. Open issues of the ppee analysis Mauro Raggi, LNF INFN 30th August 2014

  2. Outline • Possible analysis strategies • Addition BG suppression • BG evaluation for different strategy • Radiative correction treatment • Signal (no correction vsPhotos+coulomb) • Normalization (Photos+gattivsGattionly) • Measuring the BR • Total OR IB only or model independent? • Meesystematic checks • New cuts vs old cuts. Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  3. 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

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

  5. Signal selection • ngoodCl ≥4 • Nelectrons =2 E/P>0.85 • 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 moved to 7MeV) cuton Dalitzdecays • Mpp > 0.12 GeV new rejectsmost of 3pD • abs(MK-MKPDG) < 10 MeV Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  6. Additional suppression of the BG Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  7. Mee for the two set of cuts Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  8. BG acceptances comparison • Adding the Mpp>120 MeV and abs(Meeg) >7 MeV • Background isreduced by factor 3.5 • The acceptancelossis ~15% • Data MC comparisonimproves • BG systematics to the BR goes down to 0.37% • Becomes a BR(ppee)Mpp>120 • Needs extrapolation in the full kinematic range to be performed • Introduce a cut in the definition of Ntot for the acceptance Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  9. Rad. Corr. flux measurement Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  10. The Kaon flux measurement • Used the decay K±->p±p0D(g) (PPD) means K±->p±ge+e-(g) • Same trigger chain of the signal • MonteCarlogenerator used: • Due to radiative correction issue sing several MC generators • We have KLOE, MS, Prague with no extra photons • We have Gatti+Photos with extra photons generation • ppD selection very sensitive to extra photons • BG to ppee very sensitive to extra photons as well • 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 • Flux measurement formula: • (NPPD - NBGPPD)/(ePPDx AccPPDx BRPPD) Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  11. PPD selection cuts • N electrons = 2 (0.9<E/p and P > 3 GeV) with different charges • Pion charged = 1 (E/p<0.85 P > 10 GeV) • N gammas = 1 (no ass cluster and E >3 GeV) • 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 • Mee>10 MeV (new improve data MC agreement) • Trigger (2VTX or 1VTX or 1TRKP) Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  12. Rad. Corr models acceptances • Rad. Correction systematic • Generation of extra photonsgive a 3.2% difference in the acceptance • Assumingphotos to have a 10% accuracywe propose 0.35% systematic • Absence of the Dalitz plot reweighting on our MC • We assume the maximum effect is None-Prague (0.7% systematic) Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  13. Rad correction and BG to ppee • With the old selection we have • Maximum difference in the BG evaluation of 29 event ~ 1.1% systematic • With the new selection we have • Maximum difference in the BG evaluation of 13 event ~ 0.6% systematic Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  14. Flux calculation results 2003 • Kflux=(7.971±0.03Stat±0.06Sys±0.24Ext)x1010=(7.971±0.25)x1010 • was (7.766±0.23)x1010 • Error completely dominated by external error dBR(p0D)=3% • Effect of the radiative corrections taken into account Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  15. Radiative corrections ppee Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  16. Radiative corrections on ppee • D’ambrioso papers does’nt include any kind of radiative corrections in the IB martix element and BR evaluation • We implemented the Photos into the IB generator of ppee(many thanks to Brigitte) • Include the radiative corrections due to e+e- interaction • We also included Coulomb corrections which are constant • We will estimate the systematic due to radiative correction by comparing the acceptance of corrected and non corrected MC • The acceptance are: • Rad corr (new sel)= 6.61E-3 with no rad 6.92E-3 -> 4.5% difference • Rad corr(old sel) = 7.44E-3 with no rad 7.81E-3 -> 4.7% difference • Assumingphotos to have a 10% accuracywe propose 0.45% systematic Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  17. Mee systematic check Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  18. Mee systematic check Trigger correction not icluded Offset on the BR Max effect (4.32-4.19)/4.32 ~ 3% Result independent of the selection type depend on the MC only Preliminary Check with new selection 0 BR(Ppee) 4.19E-06 +/- 8.84E-08 (Nevent22470 MinCut 1.00E+00 error 2.11E-02) 1 BR(Ppee) 4.24E-06 +/- 3.11E-08 (Nevent21080 MinCut 2.00E+00 error 2.18E-02) 2 BR(Ppee) 4.30E-06 +/- 4.81E-08 (Nevent19140 MinCut 3.00E+00 error 2.29E-02) 3 BR(Ppee) 4.30E-06 +/- 6.09E-08 (Nevent17140 MinCut 4.00E+00 error 2.42E-02) 4 BR(Ppee) 4.32E-06 +/- 6.87E-08 (Nevent15680 MinCut 5.00E+00 error 2.53E-02) 5 BR(Ppee) 4.29E-06 +/- 7.54E-08 (Nevent14290 MinCut 6.00E+00 error 2.65E-02) 6 BR(Ppee) 4.25E-06 +/- 8.06E-08 (Nevent13120 MinCut 7.00E+00 error 2.76E-02) 7 BR(Ppee) 4.26E-06 +/- 8.43E-08 (Nevent12260 MinCut 8.00E+00 error 2.86E-02) 8 BR(Ppee) 4.31E-06 +/- 8.70E-08 (Nevent11600 MinCut 9.00E+00 error 2.94E-02) Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

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

  20. DE and IB in the Mee spectrum • Difference on the spectrum is very little in the NA48/2 acceptance • G. D’Ambrosio theoretical paper does’nt provide proper treatment of radiative corrections for the IB that are greater than the DE effect itself due to the 2 electrons in the final state • BG is 3 times bigger than the DE component need a fit with • Data, IB, DE, INT, BG(2pd), BG(3pD) too many distributions • Much better conditions expected in NA62 • 104 rejection of the BG due to photon veto • 10-20 times more statistics expected • Needs in any case improved theoretical description to get a result. Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  21. Fitting the DE • Fitting the DE using Mee is quite hard for different reasons: • IB and DE distributions of Mee are very similar much more wrtppg • Regions where 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

  22. 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

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

  24. BR calculations options • 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 systematic subtraction to be understood • Model independent BRtot? What error for accTot? Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  25. Conclusions • We improved a lot the analysis agreement between me and Milena • We developed new strategy for BG subtraction • We included the treatment of radiative corrections in both analysis • The comparison with theory is biased by absence of radiative correction in the theoretical paper. Mauro Raggi - I.N.F.N. - Laboratori Nazionali di Frascati - Italy

  26. Thank you for your attention

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