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Rare Kaon Decays Review and Prospects

Rare Kaon Decays Review and Prospects. Augusto Ceccucci/CERN Physics State of the Art Prospects. s. d. XL th Rencontres de Moriond, EW Interactions and Unified Theories. n. n. Motivations. Search for explicit violation of Standard Model Lepton Flavour Violation (LFV)

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Rare Kaon Decays Review and Prospects

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  1. Rare Kaon Decays Review and Prospects • Augusto Ceccucci/CERN • Physics • State of the Art • Prospects s d XLth Rencontres de Moriond, EW Interactions and Unified Theories n n A. Ceccucci, CERN

  2. Motivations • Search for explicit violation of Standard Model • Lepton Flavour Violation (LFV) • CP-Violation and Quark Mixing • Flavour Changing Neutral Currents (FCNC) • Unique probe of s → dtransitions • Small theoretical errors [for some decays!] • Other tests of fundamental symmetries • CP,CPT (e.g. KS→3p0 in G. Lanfranchi’s talk, KL→p+p-e+e-) A. Ceccucci, CERN

  3. Lepton Flavour Violation A. Ceccucci, CERN

  4. m→ e g x x |DG|=1 Puzzling replication of generations • Foreseen in many extensions of SM: • Generation-Changing gauge interactions (Cahn, Harari (1980)) • Left-Right symmetry • Technicolor • Compositeness • Super-symmetry m-e conversion x x K+→p+m+e- |D G| = 0 |D G| = 1 x x m→ eee KL→me A. Ceccucci, CERN

  5. K+p+m+e-AGS – E865 New Result based on 1998 data: hep-ph/0502020 BR(K+p+m+e-)< 2.2  10-11 (90%CL) Combined with previous results: BR(K+p+m+e-)< 1.2  10-11 (90%CL) • ~108 K+ /s • ~3 109part /pulse • PK~6 GeV/c Backgrounds (examples): K+→p+p+p-→ p+m+ne-n K+→p+p0→m+ne+e-g K+→m+p0n→m+e+e-g Accidentals 8 Candidates consistent with expected background of 8.2 ±1.9 Nsig <2.4 A. Ceccucci, CERN

  6. >150 TeV/c2 E871 >80 TeV/c2 E865 >37 TeV/c2 KTeV Lower bounds for generation-changing bosons (gX/gW~1) • Further progress on LFV (charged leptons) expected in muons • m→eg PSI • m- N →e- N MECO@AGS, J-PARC A. Ceccucci, CERN

  7. CP-Violation and Quark Mixing A. Ceccucci, CERN

  8. CKM matrix and CP-Violation Quark mixing is described by the Cabibbo-Kobayashi-Maskawa (CKM) matrix KM mechanism: Ng=2 Nphase=0  No CP-Violation Ng=3 Nphase=1  CP-Violation Possible e.g. Im lt= Im Vts*Vtd ≠ 0  CP • KM mechanism appears to be the main source of CP-violation in quarks: • Direct-CP Violation exists: e’/e 0 NA48, KTeV • CP violation in the B meson sector: ACP(J/y Ks), BaBar, Belle • Now look for inconsistencies in SM using independent observables affected by small theoretical uncertainties and different sensitivity • to new physics A. Ceccucci, CERN

  9. Kaon Rare Decays and the SM (holy grail) |Vtd| Kaons provide quantitative tests of SM independent from B mesons… …and a large window of opportunity exists! Im lt = A2l5h Re lt = A2l5r G. Isidori A. Ceccucci, CERN

  10. K→pnn : Theory in Standard Model charm contribution top contributions The Hadronic Matrix Element is measured and isospin rotated (~10% correction) A. Ceccucci, CERN

  11. Predictions in SM Error ~ 14% Mainly parametric Theory error due to charm (Buras04): Largest contribution from scale error. To be reduced by NNLO calculation Refer to Christopher Smith’s talk on long distance contributions The error is almost purely parametric A. Ceccucci, CERN

  12. Possibly the Cleanest SM test • In The phase b derives from Z0 diagrams (DS=1) whereas in A(J/y KS) originates in the box diagram (DB=2) • Any non-minimal contribution to Z0 diagrams would be signalled by a violation of the relation: • A deviation from the predicted rates of SM would be a clear indication of new physics • Complementary programme to the high energy frontier: • When new physics will appear at the Tevatron/LHC, the rare decays may help to understand the nature of it A. Ceccucci, CERN

  13. Some BSM Predictions Compiled by S. Kettel A. Ceccucci, CERN

  14. Data MC BG Sum Lnp0MC XLp0 MC Signal MC BR(KL p0nn)  5.9 x 10-7 (0ee, 1997 Data)[PRD 61,072006 (2000)] BR (KLp0nn)  1.6 x 10-6 (0g, 1997 1 Day) [PLB 447, 240 (1999)] K0Lp0nn :State of the Art KTeV 1997 Data Dalitz Analysis Still far from the model independent limit: BR(K0→ p0nn) < 4.4 × BR(K+p+nn) ~ 1.4 × 10-9 Grossman & Nir, PL B407 (1997) A. Ceccucci, CERN

  15. K+→p+nn : State of the art hep-ex/0403036 PRL93 (2004) AGS Stopped K ~0.1 % acceptance • BR(K+→ p+ nn ) = 1.47+1.30-0.89 × 10-10 • Compatible with SM within errors A. Ceccucci, CERN

  16. Setting the bar for the next generation of K+→p+nn experiments Current constraint on r,hplane ? 100 events Mean=SM 100 events Mean=E787/949 A. Ceccucci, CERN

  17. K0L→p0e+e-andK0L→p0m+m- I refer you to the talks by D. Greynat, C. Smith and L. Bellantoni Similar physics interest as K0L→p0nn . Complicated by long distance contibutions and radiative backgrounds Direct CPV Indirect CPV (Measured by NA48/1 but experimental error is still large) 0++, 2++ CPC A. Ceccucci, CERN

  18. One candidate in the signal box Combining 1997 and 1999: KTeV: KL→p0ee 1999 data PRL93, 021805 (2004) BR(KL→ p0 ee ) < 3.5 × 10-10 @90%CL BR(KL→ p0 ee ) < 2.8 × 10-10 @90%CL Expected Background 0.99 ± 0.35 events A. Ceccucci, CERN

  19. BR(K0L p0mm)  3.8  10-10 (90% C.L.) [PRL 86, 5425 (2001)] KTeV: K0L p0mm 2 events in signal region Data Background MC A. Ceccucci, CERN

  20. K0S→p0 e+e-and K0S→p0m+m- KS→p0 ee KS→p0mm NA48/1 NA48/1 6 events, expected back. 0.22 7 events, expected back. 0.15 BR(KS→p0ee)  10-9 = 5.8 +2.8-2.3(stat) ± 0.8(syst) |as|=1.06+0.26-0.21(stat) ± 0.07 (syst) PLB 576 (2003) BR(KS→p0mm)  10-9 = 2.9 +1.4-1.2(stat) ± 0.2(syst) |as|=1.55+0.38-0.32(stat) ± 0.05 (syst) PLB 599 (2004) A. Ceccucci, CERN

  21. K0L→p0ee (mm) in SM Thank to the KS measurements, the KLBR can now be predicted * Interference between short- and long-distance physics* (Isidori, Unterdorfer, Smith, EPJC36 (2004)) Constructivenow favored by two independent analyses* Destructive *G. Buchalla, G. D’Ambrosio, G. Isidori, Nucl.Phys.B672,387 (2003) *S. Friot, D. Greynat, E. de Rafael, hep-ph/0404136, PL B 595 * A. Ceccucci, CERN

  22. K0L→p0ee (mm): Sensitivity to NP Isidori, Unterdorfer, Smith: Fleischer et al*: Ratios of Bd → Kp modes could be explained byenhanced electroweak penguinswhich, in turn, would enhance the KLBR’s: ~ SES of KTeV search • A. J. Buras, R. Fleischer, S. Recksiegel, • F. Schwab, hep-ph/0402112, NP B697 (2004) A. Ceccucci, CERN

  23. Prospects • K0Lp0nn • Large window of opportunity exists. • Upper limit is 4 order of magnitude from the SM prediction • Expect results from data collected by E391a (proposed SES~3 10-10) • Next experiment KOPIO@ BNL • K0Lp0ee(mm) • Long distance contributions under better control • Measurement of KSmodes has allowed SM prediction • KS rates to be better measured (KLOE?) • Background limited (study time dep. Interference?) • 100-fold increase in kaon flux to be envisaged • K+p+nn • The situation is different: 3 clean events are published • Experiment in agreement with SM • Next round of exp. need to collect O(100) events to be useful • Move from stopped to in flight experiments A. Ceccucci, CERN

  24. KL→p0 nn E391a@PS-KEK • First dedicated experiment to search for KL→p0 nn • Proposed SES~ 3 10-10 • Based on pencil kaon beam and photon vetoes • Collecting data now: waiting for results • This is a Stage I project for further study at J-PARC A. Ceccucci, CERN

  25. KL→p0 nnKOPIO@BNL • Proposed to collect 60 KL→p0 nn events with S/B~2 (Im ltto 15%) • Measure as much as possible: • Energy, Position and Angle for each photon • Work in the Kaon Center of Mass • Micro-bunched AGS beam • Use TOF to measure KL momentum • Start construction in 2005? A. Ceccucci, CERN

  26. KOPIO@BNL Status: Approved, Currently under cost review Data Taking: 2011-? A. Ceccucci, CERN

  27. Prospects on K+→p+nn • Decays at rest: • Window of opportunity to accumulate more data at BNL until 2010 (before KOPIO data taking starts) • Ideas to pursue stopped kaon decays in Japan • Established technique… • …but hard to extrapolate to O(100) events • Decays in flight • Large acceptances, good photon rejection • Separated beam: FNAL CKM (Approved but Not Ratified) • Limited to about PK<30 GeV/c • Un-separated beam: CERN-NA48/3, FNAL-P940 • Limited by rate in beam trackers A. Ceccucci, CERN

  28. NA48/3:SPSC-I229 P(K)=75 GeV/c • Collect 80K+→p+nn events in about two years of data taking for: • 4  1012 Kaon decays/SPS year • BR( K+→p+nn )~10-10 • Acceptance ~ 10% • Absolute advantage: High energy kaon beam: >35 GeV of EM energy deposited in the vetoes very difficult to miss p0 !! • Disadvantage: ~1 GHz particle rate in beam tracker Region I Region II A. Ceccucci, CERN

  29. NA48/3 Detector Layout p+ K+ n n undetected 800 MHz (p/K/p) 10 MHz Kaon decays Only the upstream detectors see the 800 MHz beam A. Ceccucci, CERN

  30. Acceptance Region I Region II Acceptance Acceptance 75 GeV/c A. Ceccucci, CERN

  31. NA48/3 simulation Non-Gaussian MSC Gaussian MSC (old) DPp (Spectrometer 2)GeV/c DPp (Spectrometer 2) GeV/c DPp (Spectrometer 1) GeV/c DPp (Spectrometer 1) GeV/c New MSC REGION I • Uncorrelated non gaussian • tails REGION II A. Ceccucci, CERN M(miss)2 (GeV/c2)2

  32. Already Available New high-intensity K+ beam for NA48/3 A. Ceccucci, CERN

  33. SPSC@Villars ●new rare decay frontier in K physics at CERN ● new experiments planned for Kπνν important ●support R&D now for K+π +ννresults ≤ 2010

  34. P940: Redesign of FNAL-CKM to use Unseparated beam A. Ceccucci, CERN

  35. Conclusions • Rare kaon decays studies are complementary to those performed at the energy frontier • There are compelling physics cases that can be addressed with existing proton machines (SPS/MI/AGS) • Technically challenging experiments but feasible • Unique opportunity for you to join these efforts! A. Ceccucci, CERN

  36. Back-up Slides A. Ceccucci, CERN

  37. Track Momentum: 15 – 35 GeV/c (RICH limited ?) Signal Acceptance (Flyo estimation): 3.6%(Region I) 16%(Region II) Legenda: hV = Veto inefficiency (p0 or m) Acceptance = Background acceptance (Regions I or II) hID = Particle (electron-pion) separation inefficiency hVg= Veto inefficiency of radiative photon Formula: Preliminary, G. Ruggiero A. Ceccucci, CERN

  38. GIGATRACKER • Specifications: • Momentum resolution to ~ 0.5 % • Angular resolution ~ 10 mrad • Time resolution ~ 100 ps • Minimal material budget • Perform all of the above in • 800 MHz hadron beam, 40 MHz / cm^2 • Hybrid Detector: • SPIBES (Fast Si micro-pixels) • Momentum measurement • Facilitate pattern recognition in subsequent FTPC • Time coincidence with CHOD • FTPC (NA48/2 KABES technology with FADC r/o) • Track direction A. Ceccucci, CERN

  39. KABES 25 micron amplification gap Recent lab test with 25 mm gap Width ~30 ns Width ~18 ns 50 mm gap 25 mm gap improvement of occupancy observed with25mmamplification gap A. Ceccucci, CERN

  40. KABES r/o with 480 MHz FADC A. Ceccucci, CERN

  41. Competition A. Ceccucci, CERN

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