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|Vus| and K S decays from KLOE

|Vus| and K S decays from KLOE. Gaia Lanfranchi, LNF/ INFN On behalf the KLOE Collaboration XL Rencontres de Moriond 5-12 March, 2005. Kaon physics at KLOE:. |Vus| and K S decays from KLOE G. Lanfranchi – LNF/INFN. The KLOE Detector:. Calorimeter.

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|Vus| and K S decays from KLOE

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  1. |Vus|and KS decays from KLOE Gaia Lanfranchi, LNF/ INFN On behalf the KLOE Collaboration XL Rencontres de Moriond 5-12 March, 2005

  2. Kaon physics at KLOE: |Vus| and KS decays from KLOE G. Lanfranchi – LNF/INFN

  3. The KLOE Detector: Calorimeter Drift Chamber sp/p = 0.4 % (tracks with q > 45°) sxhit = 150 mm (xy), 2 mm (z) sxvertex ~1 mm s(Mpp) ~ 1 MeV σ(E)/E = 5.7%/E(GeV) σ(t) = 54 ps/E(GeV)  50 ps |Vus| and KS decays from KLOE G. Lanfranchi – LNF/INFN

  4. Vus is a fundamental parameter of SM • PDG 2004: violation of unitarity? • To measure Vus we need ΓLe3 …. • We need to measure: BR(KLe3), τL |Vus| and KS decays from KLOE G. Lanfranchi – LNF/INFN

  5. KL lifetime: direct measurement •  KL lifetime is “hard” to measure ! • Last measurement 30 years ago (Vosburgh et al, PRD 6 (1972), 1834): • Can’t stop KL’s! •  Knowledge of the KL momentum spectrum is required. •  Measure KL lifetime @ KLOE is possible because: •  KL’s are slow (βγ0.22, λL 340 cm); •  KL’s are (almost) monochromatic (P(KL)110 MeV); •  KL’s are background free (unambiguously tagged ). |Vus| and KS decays from KLOE G. Lanfranchi – LNF/INFN

  6. KL lifetime: statistical error vs fit region T= ΔL/λ Number of eventsδτ/τ 0.40 8,000,000 0.3% 0.04 8,000,000  2.4% 0.004 8,000,000  20% KLOE To reach the 0.3% statistical accuracy you need a factor 3.5103 more events!! Number of events in the fit region T = fit region in lifetime units Statistical error |Vus| and KS decays from KLOE G. Lanfranchi – LNF/INFN

  7. KL dominant BR’s: present experimental situation KL  KL e NA48: 0.4010±0.0045 KTeV: 0.4067±0.0011 PDG 2004: 0.3881±0.0027 KTeV: 0.2701 ±0.0009 PDG 2004: 0.2719±0.0022 KL 30 KL π+π-0 KTeV: 0.1945±0.0018 PDG 2004: 0.2105±0.0023 KTeV: 0.1252±0.0007 PDG 2004: 0.1258±0.0019 |Vus| and KS decays from KLOE G. Lanfranchi – LNF/INFN

  8. KL dominant BR’s: What is KLOE’s role in this scenario? KLOE can measure:  absolute branching fractions (instead of ratios!);  KL lifetime. Therefore KLOE can provide a complete and self-consistent set of measurements of the dominant KL decay widths without relying on external inputs. |Vus| and KS decays from KLOE G. Lanfranchi – LNF/INFN

  9. The KLOE KL “beam”: 1) Pure andtagged KL beam: • KL tagged by KS+-events: • Efficiency ~ 70% (mainly geometrical) • KL angular resolution: ~ 1° • KL momentum resolution: ~ 1 MeV KS+- we can measure absolute BRs since the normalization is provided by tagging events. KL 2p0 2) Low energy, monochromatic beam: P (KL)  110 MeV, βγ0.22, λL 340 cm  a big fraction of KL (50%) decays inside the detector  We can measure KL lifetime. p 110 MeV  KS KL BR = 34% |Vus| and KS decays from KLOE G. Lanfranchi – LNF/INFN

  10. KL absolute BR’s and lifetime: DATA SAMPLE: 2001+2002 data sample: 400 pb-1 statistics, 50106 tagged KL:  13 million tagged KL used to evaluate the absolute BR’s;  40 million tagged KL used to evaluate systematic uncertainties;  15 million of KL 3π0 for the direct measurement of the lifetime. |Vus| and KS decays from KLOE G. Lanfranchi – LNF/INFN

  11. KL absolute BR’s: For each KL decay mode (i=π,πe,30,+-0) we count the number of events in a given fiducial volume: Tagging efficiency: Depends on the channel Can introduce a BIAS Reconstruction efficiencies: • KLπ, πeε (rec)  60% • KL  π+π-π0 ε (rec)  45% • KL  3π0 ε (rec)  100% Integral over the fiducial volume: ε (FV, τL)  26%, depends on τL |Vus| and KS decays from KLOE G. Lanfranchi – LNF/INFN

  12. KL absolute BR’s: tag bias After these cuts the tag bias is reduced to 1-2 %: p+p-p0 Ke3 Km3 3p0 etagi / etagall .998(4) .986(2) .984(3) 1.017(3) Slightly different tagging efficiencies for different KL topologies: etagi / etagall 1 1) Different trigger efficiency for KL decays in FV / KL interactions in calo / KL punch-through:  require that KS pions satisfy trigger conditions by themselves  trigger efficiency cancels out 2) Interference effect between KS and KL tracks lowers reconstruction efficiency for KSπ+π- decays at small RL:  cut on the opening angle of KS pions |Vus| and KS decays from KLOE G. Lanfranchi – LNF/INFN

  13. KL absolute BR’s: KLcharged • Charged decays selected by closing the kinematics at the vertex: Pmis- Emiss. • Fit data with linear combination of 3 MC shapes. • Large statistics, accuracy is dominated by systematics . Lesser of Pmiss  Emiss in  or  hyp. (MeV) |Vus| and KS decays from KLOE G. Lanfranchi – LNF/INFN

  14. KL absolute BRs: KL charged • Pmiss - Emiss distribution very sensitive to radiation and momentum resolution • Check data/MC agreement via independent PID: e/μ/π from TOF and shower shape • Radiative corrections properly included in the Monte Carlo generators. Enriched sample of KLπe events Enriched sample of KLπ events Pmiss Emiss (MeV) (πe hypothesis) Pmiss Emiss (MeV) (πμ hypothesis) |Vus| and KS decays from KLOE G. Lanfranchi – LNF/INFN

  15. KL absolute BR’s: KL 000 The photon vertex of KL  3p0 is reconstructed by TOF, using cluster time/position and KL momentum (from K S p+p- ) . (Xγ,Yγ,Zγ,Tγ) L Lγ π+  solved for the two variables Lγ, LK  LK e+ e- π-  Use events with  3 photons “clustering” a vertex  99.2% selection efficiency  Residual background (1.3%, mainly π+π-π0 events) is subtracted.. |Vus| and KS decays from KLOE, G. Lanfranchi – LNF/INFN

  16. KL absolute BR’s: final results Absolute BR's results (tKL= 51.54  0.44 ns, PRD 6 (1972), 1834) BR(KL e) = 0.4049  0.0010stat 0.0031syst BR(KL ) = 0.2726  0.0008stat  0.0022syst BR(KL 3) = 0.2018  0.0004 stat 0.0026 syst BR(KL ) = 0.1276  0.0006 stat 0.0016 syst Systematics: |Vus| and KS decays from KLOE, G. Lanfranchi – LNF/INFN

  17. KL dominant BR’s: unitarity and lifetime • The BR depend on the KL lifetime through the acceptance: eFV Assuming S BR(KL X) =1 we have an indirect measurement of the KL lifetime: tKL= (50.72  0.14stat 0.36syst) ns ε = 25% 340 cm l(KL) (cm) • The sum of the dominant branching fractions (plus KL rare decays from PDG) gives: |Vus| and KS decays from KLOE, G. Lanfranchi – LNF/INFN

  18. KL dominant BR’s: results imposing unitarity BR(KL e) = 0.4007  0.0006  0.0014 BR(KL ) = 0.2698  0.0006  0.0014 BR(KL 3) = 0.1997  0.0005  0.0019 BR(KL ) = 0.1263  0.0005  0.0011 |Vus| and KS decays from KLOE G. Lanfranchi – LNF/INFN

  19. KL dominant BR’s: comparison KL e (no PDG) 0.4045±0.0009 χ2 = 5.1 KL  0.2702±0.0007 χ2 = 0.3 KLOE NA48 KTeV PDG04 KLOE KTeV PDG04 KL π+π-0 0.1255±0.0006 χ2= 0.4 KL  30 (no PDG) 0.1968±0.0012 χ2=1.9 KLOE NA48* KTeV PDG04 KLOE KTeV PDG04 * Presented by L.Litov @ICHEP04 15

  20. KL lifetime: direct measurement L Lγ π+  solved for the two variables Lγ, LK  LK e+ e- π- We use KLπ0π0π0 events tagged by KSπ+π- events:  “tagging” and “tagged” events are fully decoupled.  trigger efficiency is 100%, almost flat in the fiducial volume  The KL vertex is reconstructed by TOF, using cluster time/position and KL momentum (from K S π+π-) . (Xγ,Yγ,Zγ,Tγ) |Vus| and KS decays from KLOE G. Lanfranchi – LNF/INFN

  21. KL lifetime: control sample We use KLπ+π-π0 events to measure : EmC time scale calibration;  Vertex resolution;  Vertex reconstruction efficiency. + -  (vertex,π+π-)  1 mm KL γ  e+ + e- KS γ π- |Vus| and KS decays from KLOE G. Lanfranchi – LNF/INFN

  22. KL lifetime: EmC time scale and vertex resolution Vertex resolution: Plot di risoluzione π+π-π0 data: <σ (LK)>  2.5 cm LK (+-) (cm) EmC Time Scale: Plot di time scale L(γγ) – L(π+π-) (cm) set at 0.1% level L(π+π-) (cm) L(π+π-) (cm) |Vus| and KS decays from KLOE G. Lanfranchi – LNF/INFN

  23. KL lifetime: final result Events/0.3 ns + data Yes, it’s going down!!  14 x 106 events Fit region = 6 -26 ns ( 40% τL) t*= LK/βγc (ns) τL(KLOE) = (50.87 ±0.16 (stat) ± 0.26 (syst)) ns |Vus| and KS decays from KLOE G. Lanfranchi – LNF/INFN

  24. KL lifetime: comparison average: τL = (50.98 ± 0.21) ns KLOE direct KLOE indirect Vosburgh et al, PRD 6 (1972), 1834 PDG 2004 = (51.8 ± 0.4) ns |Vus| and KS decays from KLOE G. Lanfranchi – LNF/INFN

  25. |Vus| from Ke3 decays and τL: • Most precise test of CKM unitarity comes from 1st row: |Vud|2 + |Vus|2 + |Vub|2~ |Vud|2 + |Vus|2  1 – D where it can be tested at 10-3 level: 2|Vud|dVud = 0.0015 from super-allowed 0+ 0+ Fermi transitions, n b-decays 2|Vus|dVus = 0.0011 from semileptonic kaon decays (PDG 2002 fit) • |Vus| from neutral Kl3 partial decay widths: ½ 128 p3 GKl3 1 K0p- Vus f+ (0) = G2m M5KSew Il (l+,l0 l+´,...) 1 + dem,l f+Kp(0)form factor at zero momentum transfer, pure theory calculation (PT, lattice) I(l) phase space integral, Sew short distance corrections (1.0232) l+, l0 momentum dependence of vector and scalar form factors (f+(t), f0(t),t =q2) demelectromagnetic correction (amplitude and phase space): 0.5%Ke3-0.8%Kmu

  26. |Vus| from Ke3 decays and τL: l+ = 0.0226  0.0114 from KTeV + ISTRA l+ = 0.0023  0.0004 l0 = 0.0154  0.0008 BR(KL e) = 0.4007  0.0006  0.0014 BR(KL ) = 0.2698  0.0006  0.0014 Prescription from hep-ph/0411097 (F. Mescia @ICHEP04): 1) Quadratic parametrization of the form factor momentum dependence: 2) KL lifetime from KLOE (average of the two measurements) : tKL= (50.81  0.23) ns 3) BRs from KLOE set the sum = 1: 4) Form factor f+K(0) from Leutwyller-Roos: 0.961(8) confirmed by D. Becirevic et al (Lattice+CHPT) 0.960(9) M. Okamoto et al. (MILC) (Lattice+CHPT)0.962(11)

  27. |Vus| from Kl3 decays and τL: |Vus|f+Kπ(0) KLOE PRD 6 (1972), 1834 KLOE results: |Vus|f+K(0) (KSe3) = 0.2169 0.0017 |Vus|f+K(0) (KLe3) = 0.2164 0.0007 |Vus|f+K(0)(KLm3) = 0.2174 0.0009 From Unitarity: (1-|Vud|2)1/2f+K(0) = 0.2177 0.0028

  28. KS physics: first observation of KSπ decay:  2001 Data signal +ppg+ pp Emiss = MK2 + PK2 – E– Em Pmiss = |PK – P– Pm| Selection à la KSπe: Kcrash tag + 2 tracks from IP with Mππ< 490 MeV (reject KSππ(γ)) TOF identification: compare πμ expected flight times, reject ππ,πμ bkg Kinematic closure: use KL to obtain KS momentum PK and test for presence of neutrino: |Vus| and KS decays from KLOE G. Lanfranchi – LNF/INFN

  29. The KLOE KS “beam”: KL“crash” βγ 0.22 , TOF  30 ns KStagged by KL interaction in EmC:  efficiency  30 %  KSangular resolution: 1 (0.3 in )  KSmomentum resolution: 1 MeV  3 · 105 tags/pb-1 KSπe |Vus| and KS decays from KLOE G. Lanfranchi – LNF/INFN

  30. Direct search for KSπ0π0π0 decay: • Analysis Outline: • Signal selection: • KL crash tag + 6 prompt photons , no tracks from IP • Background: • KS π0π0 + 2split/accidental clusters • Background rejection: • compare 3p vs 2p hypotheses: • c23p- pairing of 6g clusters with better p0 mass estimates • c22p -bestpairing of 4g’s out of 6: p0 masses, • E(KS), P(KS), c.m. p0 -p0 angle c22p Data MC KS 3p0 80 Signal BOX 60 40 20 c23p 0 0 10 20 30 40 KS  3p0is pure CP violating decay, never observed: SM prediction: GS000 = GL000|e+e000|2, giving BR(KS  3p0) = 1.9 10-9: Best result:BR(KS  3π0 ) < 7.4 10-7 (90% CL) (NA48, hep-ex/0408053) |Vus| and KS decays from KLOE G. Lanfranchi – LNF/INFN

  31. KSπ0π0π0 upper limit: final result Nbkg =3.13 ± 0.82stat± 0.37sys BR(KSπ0π0π0) < 1.2  10-7 @ 90% CL Nobs =2  (events with KL tag) = 24.3% KLOE A(KS  p0p0p0) NA48 A(KL  p0p0p0) A factor 5 better than the previous limit! Using the PDG values and our limit we have: |h000| = < 1.8 10-2 , 90% CL 90 % CL NA48 (hep-ex/0408053) |Vus| and KS decays from KLOE G. Lanfranchi – LNF/INFN

  32. KSπ0π0π0 decay and Bell-Steinberger relation: (1 + i tanfSW)(Re e -iIm d) = Sf A*(KSf) A(KLf) CP Exp. input (G and phases) CPT 1 ΓS Uncertainty on KS  3p0 amplitude enters in the Bell-Steinberger relation: KS,L = K1,2+( ± δ)K2,1 A limit onBR(KSπ0π0π0)  10-7 error on Im δ  2 · 10-5 (dominated now by η+- ) |Vus| and KS decays from KLOE G. Lanfranchi – LNF/INFN 29

  33. NA48 Summary: What we have now: Measurements of all the dominant KL BR’s at 0.5% accuracy; Two measurements of the KL lifetime at 0.6% accuracy;  Best upper limit on KSπ0π0π0 decay;  First Observation of KSπ decay • Coming soon: • Final result on KS semileptonic BR; •  Analysis of KL semileptonic form factor slopes; •  Analysis of K±, BR’s and lifetime. |Vus| and KS decays from KLOE G. Lanfranchi – LNF/INFN 30

  34. BACKUP SLIDES

  35. Daily Lum (nb-1) Int Lum (pb-1) Peak Lum (cm-2 s-1) NA48 The present data taking: Luminosity collected since may 2004: L 770 pb-1 • goal is 2 fb-1 within december 2005 a factor 4 more than the present statistics Next in line: •  Limit on KS-> 3π0 at the 10-8 level •  KS semileptonic asymmetry to 4 × 10-3  First interferometry studies of KSKL system |Vus| and KS decays from KLOE G. Lanfranchi – LNF/INFN

  36. The KLOE detector:  e+ e- Be beam pipe (0.5 mm thick) Instrumented permanent magnet quadrupoles (32 PMT’s) Drift chamber (4 m  3.3 m) 90% He + 10% IsoB, CF frame 12582 stereo sense wires Electromagnetic calorimeter Lead/scintillating fibers 4880 PMT’s Superconducting coil (5 m bore) B = 0.52 T ( B dl = 2 T·m) |Vus| and KS decays from KLOE, G. Lanfranchi – LNF/INFN

  37. KL lifetime: vertex reconstruction efficiency vertex efficiency for3π0 MC (%) vertex efficiency forπ+π-π0 (data & MC) (%) MC DATA LK (true) (cm) LK ( π+π-) (cm) |Vus| and KS decays from KLOE G. Lanfranchi – LNF/INFN

  38. KL absolute BR’s: KL 000 KLOE photons are very low energy photons! Photon efficiency measured on data using KLπ+π-π0 events Photon energy spectrum + DATA - Monte Carlo Plot dell’energia totale per 6 fotoni O della massa totale. 7 MeV <Eγ< 250 MeV |Vus| and KS decays from KLOE, G. Lanfranchi – LNF/INFN

  39. 000 +-0 e  Effect of the tag bias: Before cuts: After cuts: ε (tagging) ε (tagging) LK (cm) LK (cm)

  40. The t0 of the event: T(measured) = T(stop)-T(start) T(stop) = T + 1(cables+FEE) T(start) = Ttrg + 2(cables+FEE) + rephasing T(measured) = T + (2 - 1) - (Ttrg+ rephasing) = T + T0

  41. The t0 of the event: T(measured) = T(stop)-T(start) T(stop) = T + 1(cables+FEE) T(start) = Ttrg + 2(cables+FEE) + rephasing T(measured) = T + (2 - 1) - (Ttrg+ rephasing ) = T + T0 In the simplest case of a photon we have: T = L/c  Tmeasured-L/c = T0 For each event we have to find one particle that can fix the T0 for that event !

  42. KS  π0π0π0 search: background calibration  DATA -- MC ALL ALL c22p<14 c23p c23p A good agreement is observed in each scatter plot region 14<c22p<40 c22p>40 c23p c23p

  43. KS  π0π0π0 search: background calibration c23p<4 c23p>4  DATA -- MC ALL c22p c22p A good agreement is observed in each scatter plot region ALL c22p

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