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Kaon Physics

Kaon Physics. New determination of |V us | Using very rare K decays to search for new physics Future efforts Summary. R. Ray Fermilab. July 6 - 9, 2005. Kaon Experiments with New Results at KAON 2005. CERN NA48: 1997-2001 K L NA48/1: 2000, 02 K s NA48/2: 2003, 04 K . Fermilab,

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Kaon Physics

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  1. Kaon Physics • New determination of |Vus| • Using very rare K decays to search for new physics • Future efforts • Summary R. Ray Fermilab July 6 - 9, 2005

  2. Kaon Experiments with New Results at KAON 2005 CERN NA48: 1997-2001 KL NA48/1: 2000, 02 Ks NA48/2: 2003, 04 K Fermilab, KTeV: KL/KS Frascati: KLOE: e+e- KsKL, K+K- BNL E949: stopped K+ BNL E865: K+ KEK E391a: KL Protvino ISTRA+: K- Physics in Collision 2005 R. Ray - Fermilab

  3. Vud Vus Vub Vcd Vcs Vcb Vtd Vts Vtb d s b d’ s’ b’ = Resolution of the CKM Unitarity Problem Unitarity Problem First Row 1 -(|Vud|2 + |Vus|2 + |Vub|2) = 0.0043  0.0019 (PDG 2002) 2s difference from unitarity Physics in Collision 2005 R. Ray - Fermilab

  4. 2002 PDG |Vux| Evaluations |Vud| = 0.9734 ± 0.0008 from 0+ 0+ nuclear b decays, neutron decay. |Vus| = 0.2196 ± 0.0023 from K+, K0 decays to pen (pmn not used by PDG because of large form factor uncertainties) |Vub| = (3.6 ± 0.7)  10-3 from semileptonic B decays 2003 K+ measurement from BNL E865 consistent with unitarity Interesting to revisit KL measurements (PDG fit values based on averages of many old experiments with large errors) Physics in Collision 2005 R. Ray - Fermilab

  5. _ l- _ n |Vus|2 K0 _ _ d d u s p+ Determination of Vus by Measurement of Kl3 Decays WANT THIS Measurement of rates B(K  pen), B(K  pmn) Measurement of form factors needed to calculate phase space integrals Radiative corrections (theory) Form factors at t=0 (theory) GKl3 = B(Kl3)/tL (tL from PDG) Only external measurement (New measurement from KLOE now available!) Physics in Collision 2005 R. Ray - Fermilab

  6. 2003: BNL E865 Measurement of B(K+ p0e+n) • Using 70,000 K+e3 decays normalized to K+ p+p-, K+  p0m+n, • K+  p+p0p0, they found B(K+e3) to be 5% higher than PDG. • Result is consistent with CKM unitarity at 1% level. • Assumes other K+ branching ratios are correct. Data/MC comparison for e+ momentum from p0 e+e-g decay for signal and normalization modes. Physics in Collision 2005 R. Ray - Fermilab

  7. New Measurements in 2004 “the kaon revolution” - Marciano • KTeV measured 6 largest branching fractions and KL semileptonic • form factors (Ke3 and Km3) + Ke3g and Km3g • NA48 measured KL pen/charged fraction, Ke3 FF and • B(KL  p0p0p0), Ke3g and Km3g • KLOE measured 4 main KL branching fractions, KL lifetime, • B(KS  pen). Also a new measurement of B(K+  m+n) and first • observation of B(KS  pmn). • New K+e3 measurement from NA48 • New K+e3branching fraction and FF results from ISTRA+. Physics in Collision 2005 R. Ray - Fermilab

  8. GKm3 / GKe3 = G(KL p m n) / G(KL  p e n) G+-0 / GKe3 = G(KL p+p-p0) / G(KL  p e n) G000 / GKe3 = G(KL p0p0p0) / G(KL  p e n) G+- / GKe3 = G(KL p+p-) / G(KL  p e n) G00 / G000 = G(KL p0p0) / G(KL  p0 p0p0)     KL Branching Ratio Measurements • KTeV measures the following 5 ratios of partial decay rates: • These six decay modes account for 99.93% of KL decays, so ratios • may be combined to determine branching fractions. • NA48 measures: • G(KL  p e n) / G(2 track) and B(KL p0p0p0), Ke3 FF, B(Ke3) • KL measurements consistent with KTeV, K result consistent with E865 • KLOE (e+e-  K+K-, KLKS) can tag one kaon and measure branching • fractions using accompanying kaon. They measure branching fractions • for the 4 main KL decay modes. E.g. Physics in Collision 2005 R. Ray - Fermilab

  9. Simple event reconstruction and selection may be used to distinguish different decay modes with very little background Physics in Collision 2005 R. Ray - Fermilab

  10. KTeV Measured Partial Width Ratios Data - MC Comparison for Radiative Photon Candidates It is critical to model radiation properly in MC Radiation changes Ke3 acceptance by 3%. Effect on other modes is < 0.5% Both KTeV and NA48 have published new measurements of B(Ke3g) and B(Km3g) Physics in Collision 2005 R. Ray - Fermilab

  11. Comparison of KTeV, NA48, KLOE and PDG KL Branching Fractions Value based on PDG-style fit to all new measurements (KTeV, KLOE, NA48) Physics in Collision 2005 R. Ray - Fermilab

  12. KLOE KL Lifetime Measurements • “Indirect method” - From BR measurements • Detector acceptance depends on tL. • SB(KL major decays)[tL] + 0.0036 1tL • tL = (50.72  0.14  0.33) ns • “Direct Method” using KL p0p0p0 - Fit proper time distribution. Sum of rare decays tL = (50.87  0.16  0.26) ns Combining both KLOE results: tL = (50.81  0.23) ns Old PDG Average: tL = (50.98  0.4) ns New measurement of t soon! Physics in Collision 2005 R. Ray - Fermilab

  13. Parameterization: where Semileptonic Form Factor Measurements (to determine IK integrals) IK depends on the two independent semileptonic FFs. . Phase space, no form factor Phase space with form factor Ke3 Km3 y y - y t/mp2 t/mp2 Physics in Collision 2005 R. Ray - Fermilab

  14. KL Form Factor Results Linear Model Km3Form Factor Physics in Collision 2005 R. Ray - Fermilab

  15. Charged Kaon Decays • New measurement of semileptonic form factors from ISTRA+ • New measurements of B(K  p0en): • BUT, decay modes used as normalization for K  p0en have • not been re-measured. (KLOE, NA48) • Also, new measurement of K+ lifetime is needed (KLOE) Physics in Collision 2005 R. Ray - Fermilab

  16. K0: KTeV quadratic FF (including 0.7% model dep.) K+: ISTRA+ quadratic FF (including 0.7% model dep.) Input to Recent |Vus| Calculation B(KLe3): KTeV, KLOE, NA48 B(KLm3): KTeV, KLOE B(KSe3): KLOE B(K+e3): E865, NA48, ISTRA+ tL: KLOE + PDG average tS: KTeV, NA48 average t+: PDG Short-distance radiative correction = 1.023 (Sirlin) Long-distance radiative corrections: (Andre, Cirigliano et al.) de = 0.0104  0.002 dm = 0.019  0.003 de+ = 0.0006  0.002 f+(0) = 0.961  0.008 (Leutwyler - Roos) Physics in Collision 2005 R. Ray - Fermilab

  17. Comparison with Unitarity Average of all recent results accounting for correlations |Vus|f+(0) = 0.2173  0.0008 Uses updated |Vud| = 0.9739  0.0003 (Hardy, Towner; Marciano, Sirlin - KAON 2005) Using f+(0) = 0.961  0.008 (Leutwyler - Roos): |Vus| = 0.2261  0.0021 1 -(|Vud|2 + |Vus|2 + |Vub|2) = 0.0004  0.0011 Unitarity restored! Physics in Collision 2005 R. Ray - Fermilab

  18. Consistency of BR and FF results with Lepton Universality Compare for Ke3 and Km3 1.0058(10) from T. Andre 0.6622(18) from KTeV Same test with PDG values gives 1.0270  0.0182 Physics in Collision 2005 R. Ray - Fermilab

  19. Rich and varied field: • Short-distance dominated decays • KL p0nn, K+  p+nn, KL  p0e+e- • Precise determination of flavor mixing • Excellent tools to test SM to high precision • Long-distance dominated rare or radiative decays • K+ p+l+l-, KL  p0gg, KS  gg, KL  m+m- • Study low-energy QCD dynamics and long-distance backgrounds to short-distance physics • Reliance on chiral perturbation theory • Lepton Flavor Violating decay modes • KL  p0me, KL  me, K+  p+m+e- • Dramatic indicators of New Physics h _ _ _ KL p0nn KL  p0l+l- KL m+m- r _ K+ p+nn Very Rare Kaon Decays Physics in Collision 2005 R. Ray - Fermilab

  20. Short-Distance Decays K _ h _ KL p0nn r _ K+ p+nn • The theoretically cleanest processes in meson decays • Suppressed to the 1-loop level by GIM, no tree • level pollution. • No competing long-distance contributions. • No significant QCD corrections • Hadronic m.e. from K pen Physics in Collision 2005 R. Ray - Fermilab

  21. _ K  pnn in the Standard Model _ K+ p+nn _ 2 = (3.0  0.6) x 10-11 B(KL p0nn)[SM] = C0 Im(Vts*Vtd) 10-4 _ KL p0nn +1.9 -0.9 Model-independent limit (Grossman, Nir) _ _ _ B(K+ p+nn)[SM] = C+|Vcb|4 [(r - rc)2 + (sh)2] = (8.0  1.0) x 10-11 ~ 5% error due to charm Error on measured parameters Controls amount of CPV in SM Theoretical error ~ 1%! _ _ Physics in Collision 2005 R. Ray - Fermilab

  22. (sin2b) = (sin2b) _ K  pnn B  J/y KS _ Testing the Standard Model _ • In K  pnn the phase barises from Z0 diagrams (DS=1) while in • A(J/y KS) it originates in the Bd - Bd box diagram (DB=2) • Any non-minimal contribution to Z0 diagrams could lead to a violation of: • Any deviation from this relation is a • definitive sign of new physics • This is one of the cleanest tests of the SM • Complementary to searches at the energy frontier • When new physics appears at the TeVatron/LHC, rare decays will • help to understand the details _ Physics in Collision 2005 R. Ray - Fermilab

  23. Some Predictions from Beyond the Standard Model Complied by S. Kettell _ _ Physics in Collision 2005 R. Ray - Fermilab

  24. _ First dedicated KL p0nn Experiment Designed to get to SES ~ 10-10 Run I - Feb to July, 2004 Run II - Feb - April 2005 Run III - Anticipated in Fall of 2005 New preliminary result based on 10% of Run I E391a at KEK Experimental method (1) Measure g hit position and energy (2) Reconstruct Z decay vertex assuming M(2g) = M(p0) (3) Require missing Pt and decay vertex in fiducial volume Physics in Collision 2005 R. Ray - Fermilab

  25. E391a (cont.) • Pencil Beam • ~ 4 cm x 4 cm at CsI • improves transverse momentum resolution • Hermetic photon veto • reject background from KL 2p0 where two photons • are missing • Vacuum • 10-5 pa in decay region • minimize background from neutron interactions • detectors in low vacuum region (~0.1 Pa) separated from high vacuum region by thin membrane • In Run I, part of vacuum membrane drooped into beam resulting in neutron backgrounds. Fixed for Run II. Physics in Collision 2005 R. Ray - Fermilab

  26. KEK E391a (cont.) Physics in Collision 2005 R. Ray - Fermilab

  27. E391a (cont) • Kaon Decay Background • KL 2p0 background estimated • using Monte Carlo simulation • 4g invariant mass for both KL 2p0 • and 3p0 accurately reproduced • The expected number of events is 0.02 • in the signal region and 0.05 in the side • band region KL 2p0 Physics in Collision 2005 R. Ray - Fermilab

  28. Summary of E391a Background Estimation Physics in Collision 2005 R. Ray - Fermilab

  29. Preliminary E391a Result from 10% of Run I Data Sample p0 Pt vs. Reconstructed Z Vertex • No events in the signal box • S.E.S. = 1.17 x 10-7 • BR < 2.86 x 10-7 (90% C.L.) • Based on 1.14 x 109 KL decays • ~ 2X better than previous KTeV limit • Run II data in hand • With anticipated Run III data the • Grossman-Nir limit may be within reach Signal Box Z(cm) Severe cuts required to reduce background from membrane. Resulting acceptance 10x lower than design. Runs II and III will have higher acceptance and lower background. Multi p0 background from neutron interactions Single p0 background from neutron interactions Physics in Collision 2005 R. Ray - Fermilab

  30. E787/E949 at BNL K+ p+nn _ h • Stopped K+ experiment - K+ in, p+ out • Measure full kinematics of p+ (E, P, Range) • PID by recording p-m-e decay chain • Hermetic photon veto detectors • Two major backgrounds • K+ m+n (BR=63%) • kinematics • PID (p/m separation) _ K+ p+nn r • K+ p+p0(BR=21%) • kinematics • photon veto Signal region 1 Signal region 2 Physics in Collision 2005 R. Ray - Fermilab

  31. New event Combined Result for E787/E949: B(K+ p+nn) = (1.47 ) x 10-10 PRL 93 (2004) 031801 _ +1.30 - 0.89 _ ~2  B(K+ p+nn)SM E787/949 (cont.) Results from region 1 • E787 (1995-98) observed two candidates • with a background of 0.15  0.05 events • B(K+ p+nn) = (1.57 ) x 10-10 _ +1.75 - 0.82 • E949 is a modest upgrade to E787 to • accommodate higher rates • SES goal of < 10-115-10 SM events • Only 20% of running time realized • E949 observed one additional event Physics in Collision 2005 R. Ray - Fermilab

  32. _ Physics similar to KL p0nn. Better experimental signature. Complicated by long distance contributions and radiative backgrounds. Observation of KS  p0e+e- (m+m-) has revitalized interest in KL  p0e+e- (m+m-). KL BR can now be predicted. KL p0e+e- and KL  p0m+m- Physics in Collision 2005 R. Ray - Fermilab

  33. KTeV: KL p0e+e- 1999 Data M(gg) 1 event in signal ellipse 0.99 ± 0.35 expected background events Blind analysis Box 130 < mgg < 140 MeV/c2 485 < meegg < 510 MeV/c2 Signal ellipse ± 2s M(eegg) BR(KL  p0e+e-)  3.50 x 10-10 (90% C.L.) (1999) [PRL 93, 021805 (2004)] BR(KL p0e+e-)  2.8 x 10-10 (90% C.L.) (1997+1999) Physics in Collision 2005 R. Ray - Fermilab

  34. Data  Background MC BR(KL p0mm)  3.8 x 10-10 (90% C.L.) [PRL 86, 5425 (2001)] KTeV: KL p0m+m- 1997 Data 2 events in signal region 0.87  0.15 expected background events New result on 1999 data expected soon Physics in Collision 2005 R. Ray - Fermilab

  35. Sensitivity of KL p0ee(mm) to New Physics Physics in Collision 2005 R. Ray - Fermilab

  36. B(KLp0e+e-) = 2 B(KSp0e+e-) = 5.2  10-9 aS Importance of KSp0e+e- aS is one of two form factors Indirect CP violating contribution B(KL p0e+e-)IND = B(KSp0e+e-)/ 330 Direct CP violating term Interference term sensitive to Im(lt) = Im(VtdVts*) Extraction of aS from B(KS) along with a measurement of B(KL) allows for extraction of Im(lt) ~ h Physics in Collision 2005 R. Ray - Fermilab

  37. B(KS p0ee) = (5.8 (stat)  0.3 (syst) 0.8 (theory)) x 10-9 |aS|=1.06 (stat)  0.07 (syst) PLB 576 (2003) +2.8 -2.3 +0.26 -0.21 NA48: First Observation of KS p0e+e- 0 events found in control region 7 events found in signal region Probability of background only ~ 10-10 Physics in Collision 2005 R. Ray - Fermilab

  38. +1.4 -1.2 +0.38 -0.32 B(KS  p0mm) = (2.9 (stat)  0.2 (syst)) x 10-9 |aS| = 1.55 (stat)  0.05 (syst) PLB 599 (2004) NA48: First Observation of KS p0m+m- 0 events found in control region 6 events found in signal region Results for aS are consistent for p0e+e- and p0m+m- Physics in Collision 2005 R. Ray - Fermilab

  39. _ Planned experiments focus mainly on K  pnn (all are designed to obtain ~100 SM events in 2-3 years) _ KOPIO (BNL): KL p0nn (approved, awaiting funding) JHF: KL p0nn, K+ p+nn, K+ T violation (proposals) NA48/3 (CERN): K+ p+nn (proposal) OKA (Protvino): continue ISTRA+ program of high statistics studies of somewhat rare K+ decays beginning with Ke2 (under construction - data-taking in 2006) _ _ _ Future Efforts Physics in Collision 2005 R. Ray - Fermilab

  40. New Kl3 measurements result in +3% shift in |Vus| compared to PDG and • are consistent with CKM unitarity (depending on f+(0)): • 1 -(|Vud|2 + |Vus|2 + |Vub|2) = 0.0004  0.0011 • 5-8% shifts observed in main KL branching fractions. • Value in repeating old measurements with modern, high statistics experiments. • First results from KL p0nn experiment E391a at KEK. More to come… • Next generation of rare K decay experiments hold promise of precise • determination of r, h to compare with the B system. _ Summary Physics in Collision 2005 R. Ray - Fermilab

  41. Extra Slides Physics in Collision 2005 R. Ray - Fermilab

  42. Summary of KL Lifetime Measurements Physics in Collision 2005 R. Ray - Fermilab

  43. Determination of |h+-| Using B(KL p+p-) KTeV: |h+-| = (2.239  0.005 KTeV  0.008EXT)x 10-3 (using new average tL) Physics in Collision 2005 R. Ray - Fermilab

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