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Rare Kaon Decays: Opportunities at CERN

Rare Kaon Decays: Opportunities at CERN. Augusto Ceccucci/CERN Padova, January 18, 2005. Why study Rare Kaon Decays In the 21 st century?. Search for explicit violation of Standard Model Lepton Flavour Violation Study the strong interactions at low energy

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Rare Kaon Decays: Opportunities at CERN

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  1. Rare Kaon Decays: Opportunities at CERN Augusto Ceccucci/CERN Padova, January 18, 2005 A. Ceccucci, CERN

  2. Why study Rare Kaon DecaysIn the 21st century? • Search for explicit violation of Standard Model • Lepton Flavour Violation • Study the strong interactions at low energy • Chiral Perturbation Theory, Form Factors • Test fundamental symmetries • CP,CPT • Probe the flavour sector of the Standard Model • FCNC s d Vtd Unique probe of the s→d quark transitions Vts* A. Ceccucci, CERN

  3. Quark mixing and CP-Violation Quark mixing is described by the Cabibbo-Kobayashi-Maskawa (CKM) matrix Ng=2 Nphase=0  No CP-Violation Ng=3 Nphase=1  CP-Violation Possible Im lt= Im Vts*Vtd ≠ 0 • Predictions of standard theory (after KM ): • Direct-CP Violation exists: e’/e 0 NA48, KTeV • CP violation in the B meson sector: ACP(J/y Ks), BaBar, Belle • Paradigm shift: having established the above • look for inconsistencies in SM using observables with small theoretical errors A. Ceccucci, CERN

  4. 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

  5. Further Enticement: New Physics? • These rare kaon decays are second order weak interactions mediated by Z penguins that could be sensitive to NP • A deviation from the predicted rates of SM would be a clear indication of new physics • Complementary programme to the high energy frontier: • When/if new physics will appear at the LHC, the rare decays may help to understand the nature of it A. Ceccucci, CERN

  6. NA48: ’/ 1997 ’/ 1998 ’/ 1999 no spectrometer 2000 KL NA48/1 KS ’/lower inst. intensity 2001 2002 NA48/1: KS 2003 NA48/2: K Kaons@CERN:NA48 Direct CP-Violation established! 1996 Re e’/e = 14.7 ± 2.2 10-4 Ave: Re e’/e = 16.7 ± 2.3 10-4 + KLRare Decays First observation of K0S→p0 e+e-and K0S→p0m+m- Search for Direct CP-Violation in charged kaon decays NA48/2: K 2004 A. Ceccucci, CERN

  7. NA48 Vacuum Tank A. Ceccucci, CERN

  8. NA48 Detector Total: 5.3M KL00 1996 400 GeV protons From CERN SPS Magnetic spectrometer Liquid krypton EM calorimeter 90 m long Vacuum tank A. Ceccucci, CERN

  9. Recent but well established Rare Kaon Decay Tradition @CERN:NA48/1 A. Ceccucci, CERN

  10. NA48/1: K0s→p0e+e-andK0s→p0m+m- Principal aim of NA48/1: Measure the Indirect CP-Violating Contribution to K0L→p0e+e-andK0L→p0m+m- Direct CPV Indirect CPV 0++, 2++ CPC A. Ceccucci, CERN

  11. NA48/1: Backgrounds • Many other sources investigated and found to be negligible (e,g neutral cascade decays) • Blind analysis: Control and signal region remained masked until the study of the background was finished A. Ceccucci, CERN

  12. K0S→p0 e+e-and K0S→p0m+m- M. Patel PhD thesis M. Slater PhD thesis 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

  13. 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: • A. J. Buras, R. Fleischer, S. Recksiegel, • F. Schwab, hep-ph/0402112, NP B697 (2004) A. Ceccucci, CERN

  14. NA48/1: Semileptonic X0 decays S+ X0semileptonic decay is the only source of S+ in the neutral beam because X0→S+ p- is kinematically forbidden A. Ceccucci, CERN

  15. Preliminary Result • Based on 6238 X0b-decays: BR(X0→S+e- n)=(2.51 ± 0.03sta ±0.11sys)10-4 Compare KTeV: (2.71 ± 0.38) 10-4 Systematics: Trigger Efficiency 2.6 % Acceptance 3.0 % X0 ff (g1 and f2) 1.0 % X0Polarisation 1.0 % X0 Lifetime 0.5 % Tot systematics 4.2 % Stat Uncertainty 1.2 % A. Ceccucci, CERN

  16. NA48/2 : K+/K- Simultaneous K+ and K- beams A. Ceccucci, CERN

  17. A. Ceccucci, CERN NA48/2: Aim • Direct CP violation in K±   ±  ±, K±  ±00 M(u)1 + gu, u= f( ) (Ag ) < 210 –4 g + - g - Ag = ———— g+ + g- • In addition: • Study of pp scattering using Ke4 (and p±p0p0) events • Study of medium-rare charged kaon decays • Study of semi-leptonic decays

  18. Ke4 hypothesis K- mass 0.3 0.4 m(), GeV/c2 0 0.1 0.2 m(e), GeV/c2 Background  cos(e) K±+-e±ν (Ke4)selection (preliminary) 2003 data: > 500k (background ~0.6%) Cabibbo-Maksymowicz variables [backgr. in red] A. Ceccucci, CERN

  19. 4m2()= 0.0779(GeV/c2)2 M2(00), (GeV/c2)2 A. Ceccucci, CERN First Observation of the + - - rescatteringin K  0 0 decays 29M decays NA48/2 Preview! M2(00), (GeV/c2)2

  20. a0-a2 = 0.265 = 0. M2(00), (MeV/c2)2 A. Ceccucci, CERN Determination of a0-a2 fromK  0 0 decays N. Cabibbo hep-ph 0405001, PRL93 (2004)

  21. K±  ±+- >1000ev. (PDG: ~ 800) K±±e+e-& K±±+-selection(preliminary) NA48/2 (2003) K±  ± e+e- >2600ev. Form-factor M(± e+e-), GeV/c2 Z=(M(ee)/MK)2 • low background (1-2%) • expected data sample in 2003-2004 • comparable to the World best sample A. Ceccucci, CERN

  22. “CERN Director General Outlines Seven-point Strategy for European Laboratory” 18.6.2004 Official CERN Press ReleaseGeneva 18 June 2004. “At the 128th session of CERN Council, held today under the chairmanship of Professor Enzo Iarocci, CERN Director General, Robert Aymar, outlined a seven-point scientific strategy for the Organization. Top of the list was completion of the Large Hadron Collider (LHC) project with start-up on schedule in 2007. This was followed by consolidation of existing infrastructure at CERN to guarantee reliable operation of the LHC, with the third priority being an examination of a possible future experimental programme apart from the LHC.”……… ……… The possible Future Programme was reviewed by the SPSC in Villars (September 22-27, 2004) A. Ceccucci, CERN

  23. Message from the CERN Director General to the staff (Jan 05) • The top priority is to maintain the goal of starting up the Large Hadron Collider (LHC) in 2007 • “…Meanwhile, the natural break we have in the fixed-target programme in 2005 is already allowing the community to develop a well-focused programme for the future” A. Ceccucci, CERN

  24. The Next Step: NA48/3K+→ p+ n n at the CERN-SPS SPSC-2004-029 SPSC-I229 Cambridge, CERN, Dubna, Ferrara, Firenze,Mainz, UC Merced,Perugia, Pisa,Saclay, Sofia, Torino, + ?? • Work inspired by: • High Quality NA48/2 charged Kaon beams and Beam Spectrometers • Outstanding Progress by BNL E787/E949 • In flight technique with separated beam proposed by FNAL CKM • not ratified by HEPAP P5 A. Ceccucci, CERN

  25. K+→p+nn : Theory • The hadronic matrix element can be extracted from • the well measuredK+→p0 e+ n • No long distance contributions QCD NLO Buchalla, Buras 1999 Prediction (CKM Workshop): BR(K+→ p+nn) = 8.0 ± 1.1 × 10-11 Expect improvements NNLO calculation + reduction parametric uncertainty  4 % error (Buras) A. Ceccucci, CERN

  26. Main K+decay modes competing with K+→p+nn BR(K+→p+nn)~10-10 !! A. Ceccucci, CERN

  27. 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 • Twice the SM, but only based on 3 events… A. Ceccucci, CERN

  28. NA48/3 (I229): Decay In Flight 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 Vey Difficult to miss p0 !! • Disadvantage: Unseparated Kaon beam Region I Region II A. Ceccucci, CERN

  29. NA48/3 Detector Layout p+ K+ n undetected 800 MHz (p/K/p) 10 MHz Kaon decays n 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. Already Available New high-intensity K+ beam for NA48/3 A. Ceccucci, CERN

  32. 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

  33. NA48 WC A. Ceccucci, CERN

  34. Main Tracker w/o beam pipe? ? We are considering a full straw tracker operated in vacuum A. Ceccucci, CERN

  35. TRT ATLAS Straw diameter – 4 mm, length – 40 and 150 cm 17 end-cap wheels are built in JINR (105 kpc of straws) COMPASSTRACKER Straw diameter – 6 and 10 mm, length up to 3.8 m Straw tracker operated in vacuum: COSY-TOF, Juelich,IKP Straw tracker, 3100 straws, evacuated – 10-3 mbar (P.Wintz) MECO, BNL (W.Molzon) Etc. 15 chambers were built in JINR A. Ceccucci, CERN

  36. Straw Tacker w/o beampipe Four views (X,Y,U,V) One Station (Exploded view) A. Ceccucci, CERN

  37. New 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

  38. ANTI • Set of ring-shaped photon vetoes surrounding the decay tank • Specification: inefficiency to detect photons above 100 MeV < 10-4 • The NA48 ANTI’s (AKL) need to be replaced • Extensive R&D Performed by American and Japanese groups • Claims that inefficiency as low as 10-5 can be achieved • Baseline solution: Lead/ Plastic scintillator sandwich (1-2 mm lead / 5 mm plastic scintillator) • Cost driver of NA48/3 A. Ceccucci, CERN

  39. LKR • The NA48 Liquid Krypton Calorimeter • Must achieve inefficiency < 10-5 to detect photons above 1 GeV • Advantages: • It exists • Homogeneous (not sampling) ionization calorimeter • Very good granularity (~2 2 cm2) • Fast read-out (Initial current, FWHM~70 ns) • Very good energy (~1%, time ~ 300ps and position (~1 mm) resolution • Disadvantages • 0.5 % X0 of passive material in front of active LKR • The cryogenic control system needs to be updated A. Ceccucci, CERN

  40. MAMUD • To provide pion/muon separation and beam sweeping. • Iron is subdivided in 150 2 cm thick plates (260  260 cm2 ) • Four coils magnetise the iron plates to provide a • 1.3 T dipole field in the beam region • Active detector: • Strips of extruded polystyrene scintillator • (1 x 4 x130 cm3) • Light is collected by WLS fibres 1.2 mm diameter Pole gap is 11 cm V x 30 cm H Coils cross section 15cm x 25cm A. Ceccucci, CERN

  41. Where are we? • August 2004 test run • WC: raise intensity to about 30 times NA48/2 • GIGATRACKER • Tested a state-of the-art ALICE SPD assembly in our beam • Use a thinner 25 micron MICROMEGAS amplification gap • Read out KABES with 480 MHz FADC (former NA48 tagger FADC) • Read KABES at ~14 times the NA48/2 rate • LKR: Complement the photon coverage with Small Angle Calorimeter SAC (CMS ECAL prototype) • CHOD test of prototypes • September 26-27, 2004 • Our presentations at Villars were well received • October 7, 2004 • John Dainton, SPSC Chairman reported the conclusions from Villars at CERN in a seminar at CERN • Verbally: ”The SPSC looks forward to receive a proposal” • October 18, 2004 • Letter of Intent officially submitted. SPSC-2004-029 SPSC-I229 • We have establishing working groups aiming to submit a proposal by mid 2005: A. Ceccucci, CERN

  42. SPSC ●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 - no competition … yet! ●longer term opportunity for K0π 0νν - direct competition (decay at rest) ●synergy with energy frontier @ LHC … @ CERN -B-physics - LF violation ●rare charmdecay: feasibility of operating experiment (NA60) ?

  43. Time Schedule • 2005 • Launch GIGATRACKER R&D • Vacuum tests • Evaluate straw tracker • Start realistic cost estimation • Complete analysis of beam-test data • Submit proposal to SPSC • 2006-2008 • Costruction, Installation and beam-tests • 2009-2010 • Data Taking A. Ceccucci, CERN

  44. Conclusions • We have found a fortunate combination where a compelling physics case can be addressed with an existing accelerator, employing the infrastructure (i.e. civil engineering, hardware, some sub-systems) of an existing experiment • We stress that this initiative in not a mere continuation of NA48 • We are seeking new Collaborators! A. Ceccucci, CERN

  45. Kaons: Longer term (i.e. More Protons Needed!) • K0L→p0e+e-and K0L→p0m+m- (NA48/4) • K0L→p0n n (NA48/5) A. Ceccucci, CERN

  46. K0L→p0ee(mm) : Perspectives • Detector s(gg)×2 • Very ambitious, KTeV/NA48 already state of the art • KS-KL time dependent interference ×2 • Position experiment between 9 and 16 KS lifetimes (hep-ph/0107046) • KS-KL time independent interference ×3 • Assume constructive interference (theoretically preferred) • Data Taking ×5 • Run in “factory mode”. After all E799-II run only for a few months to collect ~7 × 1011KL decays • Beam intensity ×4 • Need ~1012 protons/sec, slowly extracted, high energy (≤ 1 TeV), DC • Tot ~ ×240 →sens on BR ~ ×15 (on Im lt ~×4-15) • explore the window of opportunity between current upper limit and SM Ideal Kaon Application for High Intensity/High Energy Machine A. Ceccucci, CERN

  47. K0L→p0n n • Purely theoretical error ~2%: SM 3 10-11 • Purely CP-Violating (Littenberg, 1989) • Totally dominated from t-quark • Computed to NLO in QCD ( Buchalla, Buras, 1999) • No long distance contribution SM~3 × 10-11 • Experimentally: 2/3 invisible final state !! • Best limit from KTeV using p0→eeg decay BR(K0→ p0nn) < 5.9 × 10-7 90% CL 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

  48. E391a@PS-KEK • First dedicated experiment to search for KL→p0 nn • SES~ 3 10-10 • Based on pencil kaon beam and photon vetoes • Scheduled for ~100 days KEK PS beam in 2004 • This is a Stage I project for further study at J-PARC A. Ceccucci, CERN

  49. KOPIO@BNL • Aim 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

  50. KL→p0nn @CERN? From KAMI proposal E391A J-PARC NA48/5? SPS CERN may become competitive if the E391A technique works A. Ceccucci, CERN

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