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The CERN Kaon Programme: New Opportunities in Rare Decays

Explore the CERN Kaon Programme and its recent highlights in studying rare decays, CP-violation, and non-perturbative aspects of the Strong Interaction.

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The CERN Kaon Programme: New Opportunities in Rare Decays

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  1. The CERN Kaon Programme:New Opportunities in Rare Decays Augusto Ceccucci/CERN Charles University, Prague, April 15, 2009 A. Ceccucci

  2. Forward • The Standard Model (SM) was largely built from kaons… • Theta-tau puzzle and the fall of Parity Conservation • Strangeness and flavour conservation in Strong Interactions • Universality of the Weak Interaction • Absence of Flavour Changing Neutral Currents (FCNC) and GIM Mechanism • CP-Violation : e and e’/e • …Kaon decays continue to be a powerful tool to • Probe the SM looking for New Physics inrare decays • Study non-perturbative aspects of the Strong Interaction (p-pscattering and CHPT) • Look for non-universal lepton couplings (e.g. RK) A. Ceccucci

  3. 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-SPS • Direct CP-Violation • In Neutral Kaons • Rare decays • Semileptonic decays • K0S,L in Neutral Final • States (CPT, CHPT) • K0S Rare Decays • Neutral Hyperon radiative • and semileptonic decays • Search for Direct • CP-Violation in K± • Pion-Pion • Scattering NA48/2: K 2004 NA62: K+ 2007-8 • Lepton Universality 2012 • Ultra-rare decays A. Ceccucci

  4. The CERN proton Complex is unique The SPS is needed as LHC proton injector only part-time NA48NA62 Nota Bene: NAYY≡ YYth Experiment Performed at the North Area SPS Extraction site For the reminder of the time it can provide 400 GeV/c protons for fast or slow extraction A. Ceccucci

  5. CERN Kaon Programme: Recent Highlights Short reminder! • Dg/g (search for Direct CP-Violation in K± ) • p-p scattering length • Meson Leptonic Decays (RK) Progress Report! A. Ceccucci

  6. EM Calorimeter (LKr) Magnetic Spectrometer 400 GeV/c protons from SPS on Be target 90 m long decay tank A. Ceccucci

  7. K± p±p+p– K± p±p0p0 Ag x 104 Ag x 104 [1] [2][3] [4] [1] [2][3] [4] NA48/2 Final Results: hep-ex:07070697 [1] Ford et al. at BNL (1970) [2] HyperCP at FNAL, prelim. (2000) [3] NA48/2 2003 final [4] NA48/2 2003+2004 prelim. [1] Smith et al. at CERN-PS (1975) [2] TNF at IHEP Protvino (2005) [3] NA48/2 2003 final [4] NA48/2 200+2004 preliminary Acg = (-1.5 ± 2.1)  10-4 Ang = (1.8 ± 1.8)  10-4 | v | K± p±p0p0 K± p±p+p– | v | 2.0 x 109 K+ 1.1 x 109 K- 5.9 x 107 K+ 3.2 x 107 K- Dalitz Plots u u A. Ceccucci

  8. Unexpected cusp-like structure In the 2p0 invariant mass At the p+p- threshold ZOOM ON THE CUSP REGION NA48/2 PLB 633 (2006) Destructive interference between virtual (below threshold) K±→p±p+p- states followed by p+p-→ pp and the K±→p± pp amplitude. Integrated event deficit ~13% Best fit to the Cabibbo – Isidori rescattering model (JHEP 0503 (2005) 21) 4mp+2 N. Cabibbo, PRL 93 (2004) 12181 a new method to measure pp scat. (a0 – a2 and its sign) A. Ceccucci

  9. NA48/2: p-p Scattering Length A. Ceccucci

  10. Meson LeptonicDecays Standard Model: excellent prediction of RM me (Me()) mM2–me2 RM= =( )2( )2(1+RQED) m mM2–m2 (M()) radiative correction(~few %) helicity suppression: enhances sensitivity to non-SM effects PDG 2008 RKSM = (2.4770.001)10–5 V. Cirigliano, I. Rosell,Phys. Lett. 99 (2007)231801 RSM = (1.23520.0002)10–5 Clark 72 Heard 75 Experiment: Ke2 is a challenging measurement and good practice towards K+p+nn Heintze 76 NA48/2 prelim. (2003)  PDG’08 (based on 1970s experments):RK=(2.450.11)10–5(RK/RK=4.5%) NA48/2 prelim. (2004) KLOE prelim.

  11. RK beyond the SM A possible scenario: minimal SUSY extension; LVF contribution with emission of  neutrinoenhances the decay rate. A.Masiero, P.Paradisi, R.Petronzio Phys. Rev. D74 (2006) 011701 mK m RKLVF= RKSM [1+( )4( )2|13|2tan6] mH me A few percent effect in large (not extreme) tanregime with massive charged Higgs. Example (13=510–4, tan=40, MH=500GeV):RKLVF = RKSM(1+0.013). Analogous SUSY effects in pion decay are suppressed by a factor (m/MK)4 610–3 NA62 goal: accuracy better than 0.5% to provide a stringent SM test

  12. Winhart • Moriond EW ‘09

  13. Proposal to Measure the RareDecay K+p+ n n at the CERN SPS CERN-SPSC-2005-013 SPSC-P-326 Bern ITP, Birmingham, CERN, Dubna, Ferrara, Fairfax, Florence, Frascati, IHEP, INR, Louvain, Mainz, Merced, Naples, Perugia, Pisa, Rome I, Rome II, San Luis Potosi, SLAC, Sofia, Triumf, Turin A. Ceccucci

  14. CP-Violation and Quark Mixing: Outlook • NA48/2 has closed another window of opportunity • Current experimental manifestations of CP-Violation (K and B decays and mixing) seem to be consistent with one complex phase in the CKM matrix (“Standard Model”) • Precise experimental probes are required to detect deviations from the Standard Model • A promising road is provided by the study of ultra-rare kaon decays A. Ceccucci

  15. CKM Unitarity and Rare Kaon Decays The unitarity of the CKM matrix can be expressed by triangles in a complex plane. There are six triangles, one is more “triangular”: VudVub*+VcdVcb*+VtdVtb*=0 It is customary to employ the Wolfenstein parameterization: Vus ~lVcb ~ l2 A Vub ~ l3 A(r- ih) Vtd ~ l3 A(1-r- ih) Sensitive to |Vtd| CP • It is important to check that the unitary triangle is the • same for all heavy quarks. • The s-quark is just as important as the b-quark. • If experiment shows that there are differences between the • flavors this would be an important discovery. A. Ceccucci

  16. NA48/1: K0S rare decays Examples of rare decays studies performed at CERN Important to determine CP-Violation from mixing in K0L decays KS→p0mm K0S→p0 e+e- NA48/1 NA48/1 6 events, expected back. 0.22 7 events, expected back. 0.15 BR(KS→p0ee)  109 = 5.8 +2.8-2.3(stat) ± 0.8(syst) PLB 576 (2003) BR(KS→p0mm)  109 = 2.9 +1.4-1.2(stat) ± 0.2(syst) PLB 599 (2004) A. Ceccucci

  17. “CKM Unitarity Triangle” The KM Mechanism for CP-Violation is very successful Paradigm shift: use precise probes to see deviations from SM A. Ceccucci

  18. Kaons and CKM triangle Cristopher Smith @ CKM ‘08 A. Ceccucci

  19. Physics Motivation In Standard Model: • NLO QCD [Buchalla, Buras ‘94], [Misiak, Urban ’99], [Buchalla, Buras ’99] • Charm • NNLO QCD [Buras, Gorbahn, Haisch, Nierste ’06] • EW Corrections to Pc [Brod, Gorbahn ’08] • Long Distance • |DE|< 1% [Mescia, Smith ’07] • dPc,u +6% [Isidori, Mescia, Smith ’05] l= Cabibbo Angle • The SM Prediction error is dominated • by the uncertainty on the CKM elements • The theory error can still be reduced [J. Brod @ CKM’08] A. Ceccucci

  20. SM Prediction vs. Experiment As reported by J. Brod, CKM ’08 For mc=(1286 ± 13) MeV [Kühn et al. ’07] [E787, E949 ’08] And, for comparison: [E391a ’08] A. Ceccucci

  21. Kaon Rare Decays and NP (courtesy by Christopher Smith) A. Ceccucci

  22. Proposed Detector Layout K+p+ n n • SPS primary p: 400 GeV/c • Unsepared beam: • 75 GeV/c • 800 MHz • p/K/p (~6% K+) p+ K+ n ~11 MHz of K+ decays n • Sensitivity is NOT limited by protons flux • Needs ~same amount of protons on target as NA48 A. Ceccucci

  23. Principles of NA62/P-326 • High momentum kaon beam to improve the rejection of the p0 induced backgrounds • Decay in-flight to avoid the scattering and the backgrounds introduced by the stopping target The experimental technique exploits: • Precise timing to associate the outgoing p+ to the correct incoming parent particle (K+) • Kinematical Rejection of two- and three-body backgrounds • Vetoes (g and m) • Particle Identification (K/p, p/m) To achieve the required background suppression, these techniques will be combined together and possible correlations have to be measured A. Ceccucci

  24. 1. Precise Timing CEDAR (rate ~ 50 MHz) RICH (rate ~ 10 MHz) Gigatracker (rate ~ 1 GHz) p+ p p+ p+ K+ n p+ ~120 m n Unseparated beam, in-flight decay: How do you associate the parent kaon to the daughter pion in a ~1 GHz beam ? K+ : Gigatracker(pixel detector) with very good time resolution (~ 100 ps) p+ : RICH(Neon, 1 atm) read out by Photomultipliers A. Ceccucci

  25. Si sensor pixel matrix R-O chip mechanical support GTK Station • Requirements: • Track and time each beam particle • Time resolution: 200 ps / station • Material Budget: < 0.5 % X0 / station • Pattern: 300 x 300 mm2 • Two options for the Read-Out: • On-Pixel TDC • End-of-Column TDC A. Ceccucci

  26. A. Ceccucci

  27. Gigatracker R/O Prototypes INFN Design: One TDC / pixel CERN Design: End of Column TDC Both Designs in 130 nm IBM CMOS technology A. Ceccucci

  28. 2. Kinematic Rejection ~92% of Kaon decays are kinematically constraint A. Ceccucci

  29. n n p+ p+ n n K+ K+ Spectrometer ~2.5 m Current Setup LKr vacuum He Kevlar Window Beam Pipe ~120 m • The Straw Trackers operated in vacuum will enable us to: • Remove the multiple scattering due to the Kevlar Window • Remove the acceptance limitations due to the beam-pipe • Remove the helium between the chambers New Straw Tracker setup vacuum RICH Straw Trackers • The Straw Tracker is essential to study ultra-rare-decays in flight A. Ceccucci

  30. RI RII m2miss GeV/c2 m2miss GeV/c2 Kinematical Rejection K+p+p0selected on 2007 data using LKr information only Look at the tails in the m2miss reconstructed with the NA48 DCH Data vs. NA48MC: reproducibility of non- gaussian tails within x2 K+p+nnregions: background ~210-3 New Straw Tracker: MC OLD DCH: Data vs. MC

  31. Straw Prototype built in 2007 • Ultrasound Welded mylar • (linear weld, no glue!) • 36 Al • 12 (Cu+Au) mylar straws A. Ceccucci

  32. Straw Prototype: Beam Test 2007 2200V 2300V 2400V Residuals RMS=104 μm σ = 45 μm full length Straw Prototype: 2.1 m RMS=100μm σ = 43 μm RMS=122 μm σ = 45μm cm RUN 20629, muons cm RUN 20650, pions Resolution (cm) Thr=6 fC, pions cm RUN 20694, kaons CO2 (80%) CF4 (10%) Isob. (10%) Drift Distance (cm) A. Ceccucci

  33. Details of Straw Chamber Design Straw Geometry, one view “Web” Design Spacer A. Ceccucci 04/11/2008

  34. Straw Chamber Engineering Square Views Interface ring flanges JINR-Dubna A. Ceccucci 04/11/2008

  35. 3. Vetoes • Photon vetoes to reject K+ p+p0 P(K+)= 75 GeV/c Requiring P(p+) < 35 GeV/c P(p0) > 40GeV/c It can hardly be missed in the calorimeters • Muon Veto to rejectK+ m+n • Signature: • Incoming high momentum K+ • Outgoing lowmomentum p+ p+ K+ A. Ceccucci

  36. Photon E=11 GeV Pion P=42 GeV/c Cluster not reconstructed Eg = 22 GeV Expected position LKr Measured gDetection Efficienty LKr ineff. per g (Eg > 10 GeV): h ~ 7 × 10-6 (preliminary) p+ track and lower energy g are use to predict the position of the other g K+p+ p0 selected kinematically A. Ceccucci

  37. Large Angle Photon Vetoes (LAV) OPAL LEAD GLASS BEING PROCESSED FOR USE IN NA62 in Building 904 at CERN A. Ceccucci

  38. The OPAL lead glasses A. Ceccucci

  39. A prototype at BTF - Frascati 25 blocks e- 471 MeV Energy Resolution σE/E = 9.7% Cluster time Resolution σTime = 560 ps A. Ceccucci

  40. ANTI Mechanical Design A. Ceccucci

  41. LAV prototype tested at CERN Preliminary time resolution with kaons st = 1.02 ns 20 blocks installed in the NA62 vacuum tube Muons and kaons from 2/10 to 6/10 Validation of the operation in vacuum, cabling and support mechanics A. Ceccucci

  42. LAV Mechanical Design HANDLING LEAD GLASSES VETO 1-5 MAN HOLE CABLING LNF-SPAS C.Capoccia SUPPORTS A. Ceccucci

  43. First LAV Vessel completed 24 Mar ‘09 1st Completed vessel To be integrated in the existing decay tank

  44. 4. Particle Identification • K+ Positive identification (CEDAR) • p/m separation (RICH) • p/e separation (E/P) p K+  m+ p0 n A. Ceccucci

  45. The RICH Detector • Neon Gas at atmospheric pressure 2×1000 PMT (hex packing 18 mm side) Mirror Mosaic (17 m Focal Length) Vessel: 17 m long, 3 m dd Beam Beam Pipe A. Ceccucci

  46. RICH Simulation: particles separation Momentum from the magnetic spectrometer Muon suppression in p sample (15<p<35 GeV/c):1.3×10-3 A. Ceccucci

  47. RICH-100 prototype: 2007 Test Beam 96 PMT Hamamatsu R7400 CERN ECN3 Cavern K12 beam line (NA48-NA62) 17 m long 60 cm wide vessel, filled with Neon at atm. pressure 200 GeV/c negative hadron beam from CERN SPS (mainly pions) 17 m focal, 50 cm wide, 2.5 cm thick glass mirror by MARCON A. Ceccucci

  48. RICH-100: 2007 Test Beam results Dqc≈ 50 mrad (biased by PM geometry) NHits ≈ 17 DtEvent≈ 70 ps A. Ceccucci

  49. RICH-100: 2007 Test Beam results NHits ≈ 17 DtEvent≈ 70 ps A. Ceccucci

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