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Preliminary results of the analysis

Preliminary results of the analysis. Cesare Bini , Salvatore Fiore Università di Roma “La Sapienza” e sez. INFN Roma1. MonteCarlo generations. Signal: Modified Phokhara5 MC (10k events) Background: 2001-02 Neu kaon MC LSF 1:1

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Preliminary results of the analysis

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  1. Preliminary results of the analysis Cesare Bini , Salvatore Fiore Università di Roma “La Sapienza” e sez. INFN Roma1 Salvatore Fiore – Preliminary results of the K0K0analisys – LNF, Dec. 12, 2006

  2. Salvatore Fiore – Preliminary results of the K0K0analisys – LNF, Dec. 12, 2006

  3. MonteCarlo generations Signal: • Modified Phokhara5 MC (10k events) Background: • 2001-02 Neu kaon MC LSF 1:1 • e+e-4 pions pure phase space LSF 3:1 (home made) • 2005 All Phys MC LSF 1:1 (570 pb-1 – work in progress) Salvatore Fiore – Preliminary results of the K0K0analisys – LNF, Dec. 12, 2006

  4. All events Trigger OK: 95.4% EVCL OK: 65.4% Vertices OK: 45.0% mK2 (MeV) 2 tracks OK: 45.0% KS mass OK: 30.0% mK1 (MeV) Signal and background: the first cuts • Trigger requirement • EVCL: KSKL stream • Vertices:two inside a fiducial volume of 3cm radius and ±8cm in z around IP (regeneration rejection) • # of tracks: two tracks attached to each vertex are required Signal KS invariant mass reconstructed by π+π- tracks: 4 MeV circle cut applied around KS reco mass in m(K1) vs m(K2) plane Salvatore Fiore – Preliminary results of the K0K0analisys – LNF, Dec. 12, 2006

  5. KS momenta cut KSKStracks for signal events have lower momenta either than KSKL events, or fake KSKL given by 4pions pK2 (MeV) pK2 (MeV) pK2 (MeV) Neu kaon 4 pions Signal shape: pK1 (MeV) pK1 (MeV) Cut: pK < 95MeV pK1 (MeV) Salvatore Fiore – Preliminary results of the K0K0analisys – LNF, Dec. 12, 2006

  6. KS KS invariant mass cut Signal shape: 4 pions f0,a0 mass is reconstructed from the two KS tracks Neu kaon mKK(MeV) mKK(MeV) mKK=995MeV peak due to split tracks mKK(MeV) Cut: m(f0,a0) < 1010MeV Salvatore Fiore – Preliminary results of the K0K0analisys – LNF, Dec. 12, 2006

  7. Cut: m(4pions) < 1010MeV 4 pions invariant mass cut Neu kaon 4 pions Signal shape: m4pions (MeV) m4pions (MeV) m4pions(MeV) Salvatore Fiore – Preliminary results of the K0K0analisys – LNF, Dec. 12, 2006

  8. E2miss-P2miss cut Using the 4-momentum conservation , we obtain a variable which is zero for the signal, negative for channels like (wrong KS momentum reconstruction) Neu kaon 4 pions Signal shape: Signal -5000 200 -5000 200 E2miss-P2miss(MeV2) E2miss-P2miss(MeV2) Cut:-200>E2miss-P2miss>200MeV2 -1000 0 1000 E2miss-P2miss(MeV2) Salvatore Fiore – Preliminary results of the K0K0analisys – LNF, Dec. 12, 2006

  9. f0 /a0 invariant mass: signal efficiency MC truth before (solid) and after (dashed) the cuts selection efficiency(wrong errors) selection efficiency for is 24.2% mKK(MeV) mKK(MeV) Salvatore Fiore – Preliminary results of the K0K0analisys – LNF, Dec. 12, 2006

  10. 2001-02 analysed data With the previous cuts we analysed: 2001-02 data sample and 2001-02 MC (neu kaon + 4pions) Data-MC comparison before last four cuts pK2 (MeV) pK1 (MeV) red: mcblack: data same luminosity: 420 pb-1 E2miss-P2miss(MeV2) mKK(MeV) Salvatore Fiore – Preliminary results of the K0K0analisys – LNF, Dec. 12, 2006

  11. 2005 Data vs 2001-02 pK2 (MeV) 2005 data sample (990 pb-1): Plots are normalized to the same luminosity 2005 all phys MC(570 pb-1): analisys is following the ongoing production black: 2005 blue: 2002 pK1 (MeV) mKK(MeV) E2miss-P2miss(MeV2) Salvatore Fiore – Preliminary results of the K0K0analisys – LNF, Dec. 12, 2006

  12. After all the selections performed, there is a residual background, from 2001-02 MC’s, of 3 events from neu kaon and 4 events from the 4 pions In 2001-02 data we see 7 events, in 2005 we see 15 2005 data only 2001-02 red: MCblack: data mKK(MeV) mKK(MeV) Salvatore Fiore – Preliminary results of the K0K0analisys – LNF, Dec. 12, 2006

  13. Upper limits With these results from data and MC, we obtain the resulting upper limit for # of events is evaluated using Feldman-Cousins method • B.R. < 7.0·10-8 @ 90%C.L. (420 pb-1) • B.R. < 3.9·10-8 @ 90%C.L. (1.4 fb-1) (assuming MC05 is consistent with old one) Salvatore Fiore – Preliminary results of the K0K0analisys – LNF, Dec. 12, 2006

  14. Theoretical estimates for • Escribano’s estimate for this B.R. is 7.5·10-8 (Escribano, hep-ph/0607325) • Achasov’s estimate is 1.3÷4.4·10-8 (Achasov,Gubin Phys.Rev.D64:094016,2001) • Isidori and Maiani are working on an estimate of this B.R. based on their model and the present results for f0 and a0 couplings in pp and hp decays Salvatore Fiore – Preliminary results of the K0K0analisys – LNF, Dec. 12, 2006

  15. Salvatore Fiore – Preliminary results of the K0K0analisys – LNF, Dec. 12, 2006

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