1 / 40

THE CERN Experiment NA62 for Rare Kaon Decays

THE CERN Experiment NA62 for Rare Kaon Decays. Massimo Lenti INFN Sezione di Firenze. Outline of the presentation. Physics motivations for K + → p + nn The beam The main background channels The apparatus The signal acceptance and S/B Time schedule and Conclusions. Kaon Physics.

carlos-wolf
Download Presentation

THE CERN Experiment NA62 for Rare Kaon Decays

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. THE CERN Experiment NA62for Rare Kaon Decays Massimo Lenti INFN Sezione di Firenze

  2. Outline of the presentation • Physics motivations for K+→p+nn • The beam • The main background channels • The apparatus • The signal acceptance and S/B • Time schedule and Conclusions M. Lenti

  3. Kaon Physics CP M. Lenti

  4. K→pnn Use Isospin Symmetry and normalize to K→pen M. Lenti

  5. Theoretical uncertainties: KL→p0nn Matrix Element from Kl3 Only Top contributes M. Lenti

  6. Theoretical Uncertainties: K+→p+nn Charm and Top contribute CKM M. Lenti

  7. Physics motivations • Theoretically very clean • Sensitive to Vtd • Very sensitive to New Physics • Present (E787/949):BR(K+p+nn) = 1.73 ×10-10 • with 7 events +1.15 -1.05 Need a 10% measurement (100 events): NA62 M. Lenti

  8. How many K+ decays? ] ~1013 K+ decays • BR(K+→p+nn) ~ 8×10-11 • Look for ~100 signal events • Signal acceptance ~ 10% NA48/NA62 Use the existing CERN accelerators Use the existing NA48 experimental hall M. Lenti

  9. The Beam • Primary Beam: • 400 GeV/c protons • 3×1012 protons/pulse (3×NA48/2) • 4.8/16.8 s duty cycle • Secondary Beam: • 75 GeV/c momentum (Dp/p~1%) • Beam acc.: 12.7 mstr(32×NA48/2) • Total rate: 800 MHz • K+ ~ 6% • 4.5×1012 K+decays/y (45×NA48/2) M. Lenti

  10. The Beam purity • Only 6% K+ but: • protons and positrons don’t decay... • pions and muons decays cannot mimic K+ decays • but beam-gas interactions !! Keep vacuum at 10-6 mbar: use existing NA48 decay tank (already directly measured) Tag the K+ in the beam: use a CEDAR M. Lenti

  11. The CEDAR The CEDAR is a Cherenkov counter Used at CERN since long time Vary gas pressure and diaphragm aperture to select K+ November 2006: test beam with a CEDAR 100 GeV/c beam Filled with Nitrogen Adapt to NA62 needs: Fill with Hydrogen Change PMT and FE Pions Protons Kaons M. Lenti

  12. Background: K+ decays M. Lenti

  13. Kinematics p qKp K+ n n m2miss=(PK-Pp)2 92% K+ decays 8% K+ decays PK : beam spectrometer Pp: straw chambers spectrometer M. Lenti

  14. Beam Spectrometer (I) • 3 Silicon Pixels stations across the 2nd Achromat: • 60(X) × 27(Y) mm per station (18000 pixel/station) • Beam rate: 800 MHz (“Gigatracker”), 50 MHz/cm2 M. Lenti

  15. Beam Spectrometer (II) s(PK)/PK ~ 0.2% s(qK) ~ 14 mrad • 300×300 mm pixels p-in-n • (18000 pixel per station) • 200 mm Si sensor + 100 mm chip • 0.13 mm CMOS technology <0.5% X0 /station s(t) ~ 200 ps/station Mech. support Si sensor Pixel matrix M. Lenti R-O chip

  16. Beam Spectrometer (III) Readout VESSEL’S SIDE CLAMPED DETECTOR’S EDGE CLAMPED The cooling System DETECTOR’S EDGE SLIDING M. Lenti VESSEL’S SIDE SLIDING

  17. Straw Chambers • 4 chambers with 4 layers/view • Ø 9.6 mm straw tubes in vacuum • 2.1 m long straws • 0.1% X0 per view (4 views) • 130 mm hit resolution per view • NA48 magnet (256 MeV/c pt kick) • holes follow beam path M. Lenti

  18. Straws Prototype In vacuum 2007 prototype M. Lenti

  19. Kinematics Reco. Missing mass measurement: dominated by angle between Kaon and pion M. Lenti

  20. Background 1: K+→m+n • Km2 :largest BR: 63.4% • Need ~10-12 rejection factor • Kinematics: 10-5 • Muon Veto: 10-5 • Particle ID: 10-2 MUV RICH M. Lenti

  21. Muon Veto: MUV • Re-use of Front Module of • NA48 Hadron Calorimeter • Build a new module • Build a Fast Plane for trigger • 10-5m detection inefficiency New module: sandwich of iron plates and scintillator strips M. Lenti

  22. RICH • p-m 3s separation 15-35 GeV/c • Neon at 1 atm (p thr.: 12 GeV/c) • 2000 PMT • 18 mm pixel • 100 ps Mirrors 18 m Beam Pipe PMT: Hamamatsu R7400 U03 M. Lenti

  23. 15 GeV/c e RICH prototype: 2009 test beam m p p×mp/mm Ring Radius (mm) 35 GeV/c p e p×mp/mm Muon suppression (15.35 GeV/c): 0.7% (preliminary) Ring Radius (mm) M. Lenti

  24. Background 2: K+→p+p0 (Kp2) 2nd Largest BR:20.9% • Need ~10-12rejection factor • Kinematics: 5×10-3 • Photon Veto: 10-5per photon (10-8per p0) • Large angle:12ANTIs (10 < acceptance < 50 mrad) • Medium angle:NA48 LKr (1 < acceptance < 10 mrad) • Small angle: IRC, SAC (acceptance < 1 mrad) M. Lenti

  25. Large Angle Veto • 12 ring em calorimeters in vacuum • 5 staggered planes per ring • inefficiencies: • 10-4.05<Eg<1 GeV • 10-5Eg>1 GeV OPAL Lead Blocks reused M. Lenti

  26. Large Angle Veto: 1° ring First ring built in Frascati and installed at CERN. Test beam in mid-october 2009 M. Lenti

  27. Small Angle Veto • shaslyk calorimeter on the beam axis • 10-5ineff. High energy g Tested in October 2006 In the NA48 tagged photon beam (see later) M. Lenti

  28. Liquid Kripton Calorimeter • Use the existing NA48 LKr calorimeter • 10-5 ineff. Eg>5 GeV • 10-4 ineff. 1<Eg<5 GeV Ineff. for Eg>10 GeV tested on data collected by NA48/2 (K+→p+p0) p g g M. Lenti

  29. Liquid Kripton Calorimeter (II) Kevlar window Magnet Calorimeter October 2006 test: Tagged photon beam Using the existing NA48 setup vacuum e- g Electron beam (25 GeV/c) Bremsstrahlung Drift chambers Energy deposition in LKr electron • 2×108 electrons collected • 10-5 ineff.sensitivity below 10 GeV g Energy GeV M. Lenti X LKr cm

  30. Multibody Background Ex. K+→p+p-e+n Stagger Straws to be hermetic for p- up to 60 GeV/c M. Lenti

  31. The NA62 Layout 10 MHz 800 MHz 50 MHz M. Lenti

  32. NA62 Event Display M. Lenti

  33. Signal Acceptance Region I: 0<mmiss2<0.01 GeV2/c4 Region II: 0.026<mmiss2<0.068 GeV2/c4 Remind: Km2mmiss2 < 0 Kp2mmiss2 = 0.0182 GeV2/c4 15 <pp< 35 GeV/c Fiducial decay region: 60 m Acceptance: 3.5% (Region I), 10.9% (Region II): 14.4% (I+II) M. Lenti

  34. Signal/Background M. Lenti

  35. Trigger Levels • 10 MHzL0 trigger input • 1track × m! × g! → 1 MHzL1 trigger input → PC farm • Software trigger reduction ~ 40 M. Lenti

  36. Conclusions • 2006-2009: R&D, test beam • 2009-2011: Construction • 2012: start data-taking • NA62 approved by CERN Research Board: 5.12.2008 • NA62 approved by INFN: 24.7.2009 • Clear Physics case • many other physics channels The NA62 Collaboration: ITP Bern, Birmingham, Bristol, CERN, Dubna, INFN (Ferrara, Firenze, Frascati, Napoli, Perugia, Pisa, Rome I, Rome II, Torino), Fairfax, Glasgow, IHEP, INR, Liverpool, Louvain, Mainz, Merced, San Louis Potosi, SLAC, Sofia, TRIUMF M. Lenti

  37. SPARES M. Lenti

  38. RK: theory Few % effect possible M. Lenti

  39. RK: NA62(2007-2008) 40% of data analyzed, 51000 Ke2 candidates, 8% background M. Lenti

  40. RK: prelim.results M. Lenti

More Related