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pp scattering lengths from Kaon Ke4 and 3 p decays by NA48/2

pp scattering lengths from Kaon Ke4 and 3 p decays by NA48/2. M.Lenti INFN Sezione di Firenze On behalf of the NA48 collaboration. HADRON07, Frascati 8-13 October 2007. Plan of the presentation. The NA48/2 experiment The Cusp (K ± → p ± p 0 p 0 )

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pp scattering lengths from Kaon Ke4 and 3 p decays by NA48/2

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  1. ppscattering lengths from Kaon Ke4 and 3p decays by NA48/2 M.Lenti INFN Sezione di Firenze On behalf of the NA48 collaboration HADRON07, Frascati 8-13 October 2007

  2. Plan of the presentation • The NA48/2 experiment • The Cusp (K±→p±p0p0) - Data 2003+2004: preliminary results - p+p-→p0p0 rescattering • Ke4 (K±→p+p-e±n) - Data 2003: preliminary results - Form factors fits • Conclusions HADRON 07

  3. The CERN NA48/2 experiment 7×1011ppp SPS protons at 400 GeV/c Kaon beam at 60±3 GeV/c momentum K+/K-~1.8 HADRON 07

  4. The NA48 detectors • 2003 run: 50 days • 2004 run: 60 days • 1997-2001: NA48 KLKS (e’/e) • 2002: NA48/1 KS • 2003-2004: NA48/2 K± (Dg) • 2007: NA62 K± (Ke2/Km2) • 2011: NA62 K+→p+nn K± HADRON 07

  5. K±→p0p0p±:selection • 1 tracks, 4 e.m. Clusters • clusters pairing: all possible combinations (3) • p0→gg vertex by imposing p0 mass • choose combination with closest vertices • K decay vertex: average of p0vertices • Calculate p0p0 invariant mass p0p0 inv.mass resolution 3p invariant mass (2004) HADRON 07

  6. Cusp evidence 2004: 43.6 M events 2003: 16.0 M events Change of slope at the p+p-threshold HADRON 07

  7. + K+ 0 0 N.Cabibbo, PRL 93 (2004) 121801 Cusp interpretation: 1 Loop No M1 amplitude M1 amplitude present:13% depletionunder the threshold HADRON 07

  8. N.Cabibbo and G.Isidori, JHEP 503 (2005) 21 Cusp interpretation: 2 Loops • All 1- and 2-loops rescattering processes • 5 S-wave scattering lengths expressed as linear comb. of a0 and a2 • Isospin symmetry breaking effect in • No radiative corr. : 5% precision on a0-a2 Subleadingeffect No rescatteringamplitude Leading effect M2(00), (GeV/c2)2 HADRON 07

  9. Cusp: fit to the data 5 parameters fit (g, h’, m+(a0-a2), m+a2, N) 7 bins excluded from the fit 2003+2004 data HADRON 07

  10. Cusp: results (1) HADRON 07

  11. Cusp: result (2) HADRON 07

  12. Ke4 (K±→p+p-e±n): selection • 3 tracks • missing energy and pt • E/p for electron PID Background estimated from Wrong sign events: 0.5% level 440000 from K+ 240000 from K- 2003 data set HADRON 07

  13. Ke4: kinematics variables Decay amplitude described by two axial (F, G) and one vector (H) form factors which can be partial wave expanded (s and p wave; d neglected): and further expanded in powers of q2: HADRON 07

  14. Ke4: form factors fit Fs, Fp, Gp, Hp and d are extracted from a fit to 10(Mpp)×5(Men)×5(cosqe)×5(cosqp)×12(f) = 15000 equi-populated bins • Data - MC Men(GeV/c2) Mpp(GeV/c2) • • K+ • K- cosqp cosqe f(rad) HADRON 07

  15. Ke4: form factors fit HADRON 07

  16. Ke4: fit results Preliminary (2003 data) HADRON 07

  17. Ke4: d dependence Use Roy equations in order to relate the d variation and the pp scattering lengths The Universal band center line parametrization corresponds to a 1-parameter fit with a fixed relation between a2 and a0 HADRON 07

  18. Ke4: pp scattering lengths HADRON 07

  19. Cusp and Ke4: comparison HADRON 07

  20. Conclusions • Preliminary 2003+2004 measurement of a2-a0 in 3p decay presented • Preliminary 2003 measurement of a2, a0 and form factors in Ke4 presented • General agreement between the NA48/2 results above HADRON 07

  21. Spare Slides HADRON 07

  22. Only s-wave possible Preliminary 2003+2004 40000 evts, bck 2-3% HADRON 07

  23. Dalitz plot slopes of K±→p±p0p0 HADRON 07

  24. Dalitz plot slopes of K±→p±p+p- HADRON 07

  25. Ke4: Transition Amplitude HADRON 07

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