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Future rare kaon decays experiments

Future rare kaon decays experiments. How will the UT look like in years >2010?…. Why study rare K decays in the LHC era?. Are K rare decays still interesting? More importantly, will it be worth to study them in the years of LHC?

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Future rare kaon decays experiments

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  1. Future rare kaon decays experiments How will the UT look like in years >2010?… Paolo Valente – INFN Roma – 1 BEACH 2006, Lancaster University

  2. Why study rare K decays in the LHC era? • Are K rare decays still interesting? • More importantly, will it be worth to study them in the years of LHC? Theory tells us: yes, a few K rare decays are – and will be – still very interesting because: • There could be more degrees of freedom near the electroweak scale, i.e. New Physics beyond the SM • We know very well the flavour mixing, but we still do not understand the underlying mechanism Rare K decays are the ideal tools Paolo Valente – INFN Roma – 2 BEACH 2006, Lancaster University

  3. Why study rare K decays in the LHC era? Rare K decays are the ideal tools: • Mediated by Flavour Changing Neutral Currents • Strongly suppressed by the hierarchy in the CKM matrix • Theoretically clean since dominated by short-distance contributions In other words, from K rare decays we can extract information on the flavour structure of New Physics Vts* Vtd s d Paolo Valente – INFN Roma – 3 BEACH 2006, Lancaster University

  4. Flavour mixing • Quark mixing is described by the Cabibbo-Kobayashi-Maskawa (CKM) matrix • 3 generations (implying CP violation is possible) • hierarchy Im lt= Im Vts*Vtd ≠ 0 • Success of the Standard Model: • Direct CP violation in the K system: e’/e 0 [NA48, KTeV] • CP violation in the B sector: ACP(J/y Ks), [BaBar, Belle] • Now we need precise determinations of the CKM parameters: • Use observables withsmall theoretical errors Paolo Valente – INFN Roma – 4 BEACH 2006, Lancaster University

  5. UT fits • 95% confidence regions extracted using |Vub| / | Vcb|, εK, ΔmBd, ΔmBs and sin2β • ρ = 0.214 ± 0.047 η = 0.343 ± 0.028 • Constraints from |Vub| / |Vcb|, ΔmBd and ΔmBs compared with constraints from CP violating quantities in the K (εK) and in the B (sin2β) sectors • ρ = 0.181 ± 0.060 η = 0.404 ± 0.035 Paolo Valente – INFN Roma – 5 BEACH 2006, Lancaster University

  6. UT and rare K decays • Already strong bounds on the unitarity triangle come from K and B DF=2 and tree level transitions • FCNC transitions can tell us more… Im lt = A2l5h Re lt = A2l5r Enhanced sensitivity to SM violations because of strong CKM suppression ~l5 KL  p0 vv K+ p+ vv KL  p0 e+e- KL  m+m - Paolo Valente – INFN Roma – 6 BEACH 2006, Lancaster University

  7. New Physics potential • Second order weak interactions sensitive to NP • A deviation from the predicted rates of SM would be a clear indication of NP • Complementary program to the high-energy frontier: • If [When!]new physics will appear at the LHC, rare decays may help to understand the nature of it Paolo Valente – INFN Roma – 7 BEACH 2006, Lancaster University

  8. New Physics scenario Vts* Vtd s d • Is flavour mixing completely governed by universal CKM matrix? s d yes no • No extra complex phases • Same operators as in Standard Model, but with different coefficients • High correlation between K and B rare decays • Extra phases - can lead to large deviations from SM prediction (especially for the CP-violating modes) New flavour simmetry breaking, L ~ 1 TeV natural scale Minimal flavour violation (MFV) Paolo Valente – INFN Roma – 8 BEACH 2006, Lancaster University

  9. K+→p+nn : SM prediction The hadronic matrix element can be extracted from thewell measured K+→p0e+n Small theoretical uncertainty, no long distance contributions BRSM(K+p+nn) QCD NLO Buchalla, Buras 1999 = C+ A4 [(r0-r)2+h2] = (8.0±1.0) 10-11 • Expected improvements NNLO calculation + reduction parametric CKM uncertainties  2 % error expected in the next few years Paolo Valente – INFN Roma – 9 BEACH 2006, Lancaster University

  10. KL→p0nn : SM prediction Already at the level of 2 % BRSM(KLp0nn) = C0 [Im(Vts* Vtd)/10-4]2 = (3.0±0.6) 10-11 • Expect to be completely dominated by parametric CKM uncertainties [Vtd and mt] in the next few years • The cleanest mode! Paolo Valente – INFN Roma – 10 BEACH 2006, Lancaster University

  11. So, why study rare K decays in the LHC era? • 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 1st ingredient: Physics! • KL→p0l+l- ,KL→p0nn,K+→p+nn are the golden modes… • BR ~ 10-10 or below • few % precision desirable to match the theoretical error …more needed! • Need very intense kaon beams • Need dedicated detectors with exceptional background rejection Paolo Valente – INFN Roma – 11 BEACH 2006, Lancaster University

  12. Rare K decays panorama JPARC is coming … you’ve heard from Tadashi Nomura E949 @JPARC pK=0.6 GeV 2.3 M/s I will concentrate on P326 in the following E391a @JPARC pK=2 GeV 320 M/s P326 @CERN unseparated, pK=75 GeV 9 M/s E391a @KEK pK=2 GeV 0.6 M/s P940 @FNAL unseparated, pK=45 GeV 3.5 M/s KOPIO @BNL pK=0.7 GeV 33 M/s CKM @FNAL separated, pK=22 GeV 9 M/s E949 @BNL KAMI @FNAL pK=10 GeV 38M/s E787 @BNL stopped K OKA @Protvino separated, pK=15 GeV 0.4 M/s K+ KLOD @Protvino 7 M/s K0 Paolo Valente – INFN Roma – 12 BEACH 2006, Lancaster University

  13. 400 GeV protons from the SPS, producing an high intensity kaon beam P326: K+→p+nn at the CERN SPS… 2nd ingredient: The beam Paolo Valente – INFN Roma – 13 BEACH 2006, Lancaster University

  14. …using part of the NA48 setup… Some pieces [and many physicists] from previous [successful] kaon experiments 3rd ingredient: A community of physicists 4th ingredient: A suitable detector! Paolo Valente – INFN Roma – 14 BEACH 2006, Lancaster University

  15. …but P326 is also much more! • The P326 project wants to exploit acombination of opportunities: • A strongphysics case • eagerly waited from theorists • fully complementary to the high-energy frontier • The possibility of having an high intensity kaon beam at the CERN SPS, using anexisting infrastructure • A communityof (enthusiast) physicists coming from successful kaon physics experiments (NA48, KLOE, and more) • The possibility of using part ofanhigh-performance and highly-specializeddetectoras NA48 [in particular very valuable parts as the Liquid Kr, the vacuum tank, the hodoscope, the magnet, the muon detector, …] … but it is also a playground for further improving experimental techniques for rare kaon decays studies by dedicated R&D studies Paolo Valente – INFN Roma – 15 BEACH 2006, Lancaster University

  16. Measurement technique: decay in flight p+ qpK qpK K+ n n • pK = 75 GeV/c • At least 10% acceptance • Signal to background  10:1 • 80 events in 2 years • 1012 rejection power needed • Define kinematical cuts ... pp (GeV/c) Paolo Valente – INFN Roma – 16 BEACH 2006, Lancaster University

  17. Background rejection Kinematically constrained Not kinematically constrained 92% of total background 8% of total background • Span across the signal region • Define a signal region • Due to K+p+p0 , split signal region in 2 Paolo Valente – INFN Roma – 17 BEACH 2006, Lancaster University

  18. Background rejection Decay BR Rejection m+n 0.63 m veto g veto p+p0 0.21 kinematics charged veto p+p+p- 0.06 p+p0p0 0.02 g veto p0m+n 0.03 g veto m veto p0e+n 0.05 g veto E/p Kinematical cuts are not sufficient to bring down backgrounds by a factor ~1012 Need veto detectors! Paolo Valente – INFN Roma – 18 BEACH 2006, Lancaster University

  19. An experimental challenge! GigaTracker + Cherenkov Straw tracker + hodoscope Liquid Krypton + g vetoes Magnetized Iron + RICH • Track and identify kaons in the beam • at0.8 GHzrate • with0.5%momentum resolution • with150 pstime resolution • with a tight material budget • Track decay products • in a10-6 mbarvacuum • with0.5%momentum resolution • with150 pstime resolution • with a tight material budget • Reject m background at10-6level • 10s p/mseparation at high p • Reject p0 and veto additional g with a10-5single g detection inefficiency Eg > 1 GeV Paolo Valente – INFN Roma – 19 BEACH 2006, Lancaster University

  20. What is already available: NA48 Total: 5.3M KL00 1996 Magnetized Iron Hodoscope Liquid krypton EM calorimeter 90 m vacuum tank Magnetic spectrometer beam Paolo Valente – INFN Roma – 20 BEACH 2006, Lancaster University

  21. Experiment layout * Already available * * magnet magnet * Gigatracker * * 1 m Notice the ~30:1 aspect ratio 0 m 200 m 100 m Paolo Valente – INFN Roma – 21 BEACH 2006, Lancaster University

  22. P326 beam Dipoles (1st achromat) Dipoles (2nd achromat) Collimator Collimator Collimator CEDAR Muon sweep From T10 target Scraper Quadrupoles Gigatracker Quadrupoles Almost 50× more kaons with present SPS Paolo Valente – INFN Roma – 22 BEACH 2006, Lancaster University

  23. Challenge #1 GigaTracker + Cherenkov • Track and identify kaons in the beam • at0.8 GHzrate • with0.5%momentum resolution • with150 pstime resolution • with a tight material budget • Beam Cherenkov counter already available (CEDAR) • New photo-detectors • Will be tested at SPS North Area in October Paolo Valente – INFN Roma – 23 BEACH 2006, Lancaster University

  24. Gigatracker Station 3 Specifications: • Momentum resolution ~ 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/cm2 Station 2 Station 1 • Hybrid Detector: • SPIBES (Fast Si micro-pixels) • Momentum measurement • Facilitate pattern recognition in subsequent FTPC • Timing to select the right track • FTPC (NA48/2 KABES micro-megas with FADC readout) • Track direction 48 mm 36 mm Paolo Valente – INFN Roma – 24 BEACH 2006, Lancaster University

  25. Gigatracker: Si micro-pixel • size: 36 mm (X) × 48 mm (Y) • pixel size: 300 mm × 300 mm • chip thickness 100 mm • X/X0 << 1% • momentum resolution 0.4% Signal/Background ratio Objective: s(t) ~ 200 ps (per station): Complex readout chip bump-bonded on the sensor 0.13 mm CMOS technology (now under development, CERN+INFN) Timing resolution (ps) Paolo Valente – INFN Roma – 25 BEACH 2006, Lancaster University

  26. Gigatracker: FTPC • Gas TPC + micro-megas • Coming from NA48/2 • R&D on new, fast, readout electronics to improve time resolution Tdrift2 micro-megas gap 25 mm Tdrift1 Paolo Valente – INFN Roma – 26 BEACH 2006, Lancaster University

  27. Challenge #2 Straw tracker + hodoscope • Track decay products • in a10-6 mbarvacuum • with0.5%momentum resolution • with150 pstime resolution • with a tight material budget Uncorrelated Non-Gaussian tails due to Non-Gaussian pp resolution Region I Region II Mmiss2 (GeV/c2)2 Paolo Valente – INFN Roma – 27 BEACH 2006, Lancaster University

  28. Straw tracker in vacuum • 6 chambers with 4 double layers of straw tubes 9.6 mm diameter • Rate: ~45 KHz per tube (max 0.5 MHz) (m+p) 2.3 m 7.2 m Operate in high vacuum X/X0 ~ 0.1% per view Low mass 7.2 m Redundant p measurement 2 magnets 270 and 360 MeV Pt kick 5.4 m 130 mm/hit s(p)/p = 0.23%  0.005% p s(q) ~ 50  20 mrad Good resolution 8.8 m Veto for charged particles up to 60 GeV/c 5 cm radius beam holes displaced in the bending plane according to the beam path Paolo Valente – INFN Roma – 28 BEACH 2006, Lancaster University

  29. TRT ATLAS Straw diameter – 4 mm, length – 40 and 150 cm Straw tracker in vacuum 17 end-cap wheels are built in JINR (105 kpc of straws) COMPASS TRACKER Straw diameter – 6 and 10 mm, length up to 3.8 m Straw trackers were already operated in vacuum: COSY-TOF, Juelich, MECO, BNL but … 15 chambers were built in JINR … no large straw detector operated in vacuum since now Paolo Valente – INFN Roma – 29 BEACH 2006, Lancaster University

  30. Challenge #3 Liquid Krypton + g vetoes • Reject p0 and veto additional g with a10-5single g detection inefficiency Eg > 1 GeV Paolo Valente – INFN Roma – 30 BEACH 2006, Lancaster University

  31. Photon vetoes • ANTI: Rate ~4 MHz (m)+ ~0.5 MHz (g) (OR of 13 rings) g in veto E (GeV) q (rad) • Liquid Kripton: Rate ~7 MHz (m) + ~4 MHz (g)+ ~3 MHz (p) g in LKr E (GeV) q (rad) Paolo Valente – INFN Roma – 31 BEACH 2006, Lancaster University

  32. Liquid Kripton 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%, • Very good time ~ 300 ps, 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 Paolo Valente – INFN Roma – 32 BEACH 2006, Lancaster University

  33. Veto rings • Set of ring-shaped photon vetoes surrounding the decay tank • Extensive R&D performed by American and Japanese groups… … followed by specialized studies for P326 by INFN groups • Inefficiency as low as 10-5 challenging but possible • Baseline solution: Lead/Plastic scintillator sandwich with WLS fibers readout • Large contribution to the total cost of the P326 project • Small angle calorimeters to close the gap of the beam-pipe Decay tube Paolo Valente – INFN Roma – 33 BEACH 2006, Lancaster University

  34. Challenge #4 Magnetized Iron + RICH • Reject m background at10-6level • 10s p/mseparation at high p Paolo Valente – INFN Roma – 34 BEACH 2006, Lancaster University

  35. MAgnetized MUon Detector • To provide pion/muon separation and beam sweeping. • 150 iron plates, 2 cm thick (260260 cm2) • Four coilsmagnetize the iron plates to provide a1.3 T dipole fieldin the beam region • Active detector: • Strips of extruded polystyrene scintillator (14130 cm3) • Light is collected by WLS fibers (1.2 mm diameter) • m rejection 10-5 • About 7 MHz of muons and 3 MHz of pions Pole gap is 3011 cm2 Coils cross section 1525 cm2 Paolo Valente – INFN Roma – 35 BEACH 2006, Lancaster University

  36. A RICH for P326 PMT’s p+ beam pipe 1 atm Ne gas mirror PMT’s 18 m • Spherical split mirror, f=17 m • 18 m long, 1 atm Neon gas • 12 GeV threshold for p • >3 s p/m separation p<35 GeV Paolo Valente – INFN Roma – 36 BEACH 2006, Lancaster University

  37. P326 collaboration Paolo Valente – INFN Roma – 37 BEACH 2006, Lancaster University

  38. P326 time schedule 2006-2007 • Refine layout, RICH R&D • Gigatracker R&D • Photon vetoes R&D • Vacuum tests • Straw tracker R&D • Liquid krypton test-beam (Oct. ’06) • Approval 2008-2009 • Construction, installation and tests 2010-2011 • Data taking Paolo Valente – INFN Roma – 38 BEACH 2006, Lancaster University

  39. P326: going on… We are looking for new collaborators! We have found a fortunate combination where acompelling physics casecan be addressed with anexisting accelerator, employing the infrastructure (i.e. civil engineering, hardware, some sub-systems) of anexisting experiment … … even though this anewinitiative And with new, challenging detectors to be designed and built Paolo Valente – INFN Roma – 39 BEACH 2006, Lancaster University

  40. Longer term (more protons needed!) • K0L→p0e+e-andK0L→p0m+m- • K0L→p0nn See T. Nomura… E391a and JPARC Paolo Valente – INFN Roma – 40 BEACH 2006, Lancaster University

  41. Conclusions • Rare K decays are interesting now, since they are sensitive to New Physics effects • They will still be very interesting when results will be coming from the LHC? Yes, maybe even more, since they can give unique information on the flavour structure of New Physics • Very ambitious experimental programs • requiring very intense hadron beams • requiring challenging detectors: hermetic, highly efficient, with PID capabilities • A lively and enthusiastic community • still not tired of many years of success from glorious past kaon experiments… • … even in hard times from the funding point of view! Paolo Valente – INFN Roma – 41 BEACH 2006, Lancaster University

  42. Paolo Valente – INFN Roma – 42 BEACH 2006, Lancaster University

  43. KL→p0nn • Purely theoretical error:  2% • 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) Paolo Valente – INFN Roma – 43 BEACH 2006, Lancaster University

  44. Looking at the far future… • A competitive program can start now for charged kaons at the current SPS • For a very competitive neutral kaon decay experiment, ~ 1013 slowly extracted, high energy protons per second would be needed Paolo Valente – INFN Roma – 44 BEACH 2006, Lancaster University

  45. E949 Stopped K technique ~0.1 % acceptance Paolo Valente – INFN Roma – 45 BEACH 2006, Lancaster University

  46. 2 events E787 + 1 event E949 Paolo Valente – INFN Roma – 46 BEACH 2006, Lancaster University

  47. E787/E949 result hep-ex/0403036 PRL93 (2004) BR(K+→ p+ nn) = 1.47 +1.30-0.89 10-10 2 the Standard Model, but with a large error (3 events…) AGS Paolo Valente – INFN Roma – 47 BEACH 2006, Lancaster University

  48. E391a Vacuum tank CsI calorimeter Main barrel Front barrel Then going to J-PARC… Paolo Valente – INFN Roma – 48 BEACH 2006, Lancaster University

  49. E949 @JPARC • Stopped K+ • With respect to E787/949: • Lower energy • Separated beam • Spectrometer: higher B field • More compact • Better resolution • Finer segmentation • Improved  veto detector (crystals) • Objective: • 50 events • Not in J-PARC phase-1 • Needs beamline, room, funding Paolo Valente – INFN Roma – 49 BEACH 2006, Lancaster University

  50. KLOD • IHEP Protvino 60 GeV proton beam • Off-axis angle=35 mrad • KL’s peak momentum = ~6 GeV/c • Objective: • 28 events/9 background in 3 years • Run in 2008 Paolo Valente – INFN Roma – 50 BEACH 2006, Lancaster University

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