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Rare Kaon Decays - 3

Rare Kaon Decays - 3. Laurence Littenberg BNL E. Fermi School, Varenna - 26 July 2005. Organization. Introduction & general motivation Lepton Flavor Violation, etc. Brief review of Unitarity K +    K L  0  K  K L  l + l - K L  0 l + l -. _. A( K +  + ).

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Rare Kaon Decays - 3

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  1. Rare Kaon Decays - 3 Laurence Littenberg BNL E. Fermi School, Varenna - 26 July 2005 L. Littenberg – Varenna

  2. Organization • Introduction & general motivation • Lepton Flavor Violation, etc. • Brief review of Unitarity • K+ • KL0 • K • KLl+l- • KL0l+l- L. Littenberg – Varenna

  3. _ A(K++) U.T. & K • ReC/ImC ~ 0.0006 • Range of mC(mC) 1.25-1.35GeV gives 8.5% in charm amplitude • 2.5% in total amplitude, 5% in BR AT AC L. Littenberg – Varenna

  4. _ _ The Challenge of KL0 • B(KL0) ~ 310-11, need intense flux of K’s • rates inevitably rather high • hard to minimize both random vetoing & veto-blindness • Kinematic signature weak (2 particles undetectable) • Backgrounds with 0 up to 1010 times larger than signal • Veto inefficiency on extra particles, both charged particles and photons, must be 10-4 • Self-vetoing is a problem • shower spreading makes it hard to maximize both signal efficiency and veto power • Huge flux of neutrons in beam • can make 0 off residual gas – requires high vacuum • halo must be tiny • hermeticity requires photon veto in this beam • Need convincing measurement of background L. Littenberg – Varenna

  5. 1st dedicated KL0 experiment - E391a • KEK 12 GeV PS • 4° “pencil” beam • <pK> ~ 2 GeV/c • CsI calorimeter Pencil beam L. Littenberg – Varenna

  6. Pencil Beam 5 stages of collimators made of heavy metal (tungsten) 2 stages of sweeping magnets Thermal neutron absorber Pb/Be plug for control of /neutron flux Fine alignment using telescope GEANT M.C. agrees well with the measurements L. Littenberg – Varenna

  7. Covered by plastic scintillators (Charged Veto (CV)) Recycled 576 Un-doped CsI (70X70X300 mm3 (from E162) 50X50X500 mm3 (from KTeV)) CC03 (Tungsten + Scin.) E391a detector setup KL beam L. Littenberg – Varenna

  8. po produced at CC02 po produced at CV (?) KL popopo KL p+p-po KL  popo KL gg 2g analysis Data without tight veto M.C. for KL decays ( Without Normalization) PT(GeV/c) Reconstructed vertex (cm) L. Littenberg – Varenna

  9. Veto Optimization ~Main-barrel timing (low E sample)~ upstream KLgg pure sample gg B.G.sample ② ① early late downstream Backsplash should NOT veto! • Real photon hit  should veto. • Backsplash  should NOT veto. L. Littenberg – Varenna

  10. E391a Result from 10% of Run I • No events observed/expected background of 0.030.01 events (mainly K2) • 1.14109 KL decay, 0.0073 acceptance  s.e.s of 1.1710-7 • B(KL0)<2.86 10-7 @ 90% CL (c.f. 5.9 10-7 from KTeV) Z(cm) L. Littenberg – Varenna

  11. Better quality of data(online plots) Run-I Run-II PT(GeV/c) Reconstructed vertex (cm) Run-II analysis Run-III this fall ( Conditionally approved ) L. Littenberg – Varenna

  12. E391a status & prospects • First physics run Feb-June 2004 • 2.21012 12 GeV POT, 50% duty factor • 5 105 KL/pulse • Detector worked well • Nominal s.e.s. 410-10 • But acceptance ~ 15 lower than in proposal (0.0073) • first sight of the enemy • Halo neutrons, self-vetoing, etc. • Analysis of 10% of data  B(KL0)<2.86 10-7 • Run II, Feb-March 2005 • Many problems fixed, 60% of Run 1 • Run III, this fall, conditionally approved L. Littenberg – Varenna

  13. JPARC Phase I Beamlines L. Littenberg – Varenna

  14. 100 more KL Thicker photon vetoes Deeper, more granular crystals Faster electronics KEK-PS to J-PARC • 1014 interacting 30 GeV protons/cycle, 5srbeamline @ 16° • 22MHz KL @ 20m, <pK> = 2.1 GeV/c, 9%/5m decay • 4% acceptance • 23 events in 3 Snowmass years (competition from ) • S:B~1:1 L. Littenberg – Varenna

  15. Signal KL00 bckgnd 16° case 0 pT Z-decay Step by step at JPARC • “Step by step” approach, learning as they go • Different beam angles, lengths • Larger detector • Eventual goal – few 100 evts L. Littenberg – Varenna

  16. KL0 Experiment veto beam veto calor. prod. tgt L. Littenberg – Varenna

  17. KL0 Experiment veto prerad beam veto calor. prod. tgt L. Littenberg – Varenna

  18. In the KLCoM • Bckgnd mainly in discrete areas • Obvious for KL00 “even” • But even “odd” case not ubiquitous • K3 infests slightly different area • Even after all bckgrnds accounted for, still some clear space for signal • Can get factor 50-100 L. Littenberg – Varenna

  19. KOPIO Technique • High intensity micro-bunched beam from the AGS • Measure everything! (energy, position, angle, time) • Eliminate extra charged particles or photons • KOPIO: p0 inefficiency < 10-8 • Suppress backgrounds • Predict backgrounds from data:dual cuts • Use “blind” analysis techniques • Test predictions “outside the box” • Weight candidate events with S/N likelihood function L. Littenberg – Varenna

  20. 40 ns between microbunches AGS Provides • Proton Beam • 100TP/spill (upgraded from present 70TP) • ~5s spill, 2.3s interspill • Microbunching • Extract debunched beam resonantly between empty buckets • 25MHz frequency • 200ps bunch width • 10-3 interbunch extinction • Kaon Beam • 42.5o take-off angle • Soft momentum spectrum • 0.5-1.5 GeV/c • 3108 KL/spill • 8% decay • 10 GHz neutrons =200 ps L. Littenberg – Varenna

  21. Tests of Microbunching Tests of: Microbunch width Interbunch extinction Studied the RF extraction mechanism proposed for KOPIO & measured a microbunch rms width of 244 ps -- KOPIO spec is 200 ps rms Measured the inter-bunch extinction ratio (flux between bunches/within bunch). KOPIO requires ~ 10-3. 4.5 MHz 93 MHz L. Littenberg – Varenna

  22. KOPIO Concepts L. Littenberg – Varenna

  23. KOPIO Detector L. Littenberg – Varenna

  24. Preradiator – convert & measure  properties . . . . . .  e+ . . . 4m . e- . . . . . . Cathode strip drift chambers Extruded Scintillator & WLS fibers 64 Layers (4% X0/layer, 2.7 X0) 256 Chambers 288 Scintillator Plates (1200 m2) 150,000 Channels Readout L. Littenberg – Varenna

  25. KOPIO Prototype Measurements–BNL LEGS Tagged Photon Beams Preradiator Angular resolution: 25 mr at 250 MeV/c Simulations agree with measurements. L. Littenberg – Varenna

  26. Shashlyk Photon Calorimeter Shashlyk modules prototyped and tested in beams. Required specs have all been met APD L. Littenberg – Varenna

  27. Beam test of Calorimeter modules Simulation: Combined PR +CAL Energy Resolution L. Littenberg – Varenna

  28. Charged Particle Veto in vacuum L. Littenberg – Varenna

  29. Charged Particle Veto Performance Plastic Scintillator – backed up by  vetoes! MC 10-3 10-4 Data 10-5 10-6 • 290 L. Littenberg – Varenna

  30. Barrel Veto/Calorimeter • Cylindrical array of 840 modules with 2.5m ID • Both signal detection and vetoing functions • 1g in prerad + 1g in BV/C • Modified version of calorimeter shashlyk technology, pmt readout • Energy resolution calculated to be almost as good as calorimeter • Time resolution should be comparable • B V/C lined with thin, high-efficiency, charged particle veto scintillators US end of barrel sealed by wall of plate shower-counter vetoes L. Littenberg – Varenna

  31. D4 & downstream vetoes • Charged & g vetoes in D4 sweeping magnet • Field sweeps vertically • DS vetoes detect g’s emerging from the beam • Lead/scintillator plate sandwich counters • Hermeticity completed by catcher veto at the back 48D48 L. Littenberg – Varenna

  32. Photon Veto Efficiency KOPIO PV Estimates and Simulations based on improved E949 Measurements supplemented by FLUKA calculations 1 MeV Visible Energy Threshold L. Littenberg – Varenna

  33. E949 SPI Measurement K2 Decay + 2 1 L. Littenberg – Varenna

  34. Catcher: Hadron Blind Beam  Veto beam Aerogel Counter 420 modules ofPb-Aerogel counter L. Littenberg – Varenna

  35. Catcher R&D results Modules prototyped and tested in beams. L. Littenberg – Varenna

  36. KOPIO Detection Modes Primary detection mode: Secondary mode: 2 photons covert in preradiator 1 photon in preradiator, 1 in BV Reconstruct 1ste+e- in “Preradiator”, Point to K decay vertex in vacuum L. Littenberg – Varenna

  37. KL modes simulated for bkgnd studies Largest back-grounds L. Littenberg – Varenna

  38. Other Backgrounds • K+ contamination of beam: <0.001 of signal rate • KLK+e-, K-e+: ~ 0.001 of signal rate • nN p0N: negligible production from residual gas in decay volume if pressure<10-6 Torr. Requirements on reconstructed ZV(KL) suppress rate from US wall to <0.01 of signal rate • n: far smaller than neutron background • Hyperons: <10-5 of signal rate • Fake photons < 0.05 of signal rate assuming ~10-3 10-3 suppression from (vetoing)  (g/n discrimination) • Two KL giving single candidate: negligible due to vetoes • (KL pX)  (p p0e ): ~0.01 of signal rate • KS p0p0: ~4  10-4 of KL p0p0 background rate _ L. Littenberg – Varenna

  39. Kinematic Separation of Signal & Background Pion kinetic energy squared (T*2) vs Ln(Missing Energy) Signal Backgrounds L. Littenberg – Varenna

  40. Radiative Ke3 • Background from radiative Ke3 when • e+ annihilates before being vetoed & resulting  combines with radiated to make “0” • 2nd  from annihilation very soft, so missed • Then it’s critical to veto on - • But what if - is very slow? Either - • have long gate with big random loss • or let background creep in • Can fight this with kinematics - • If - really slow, p m • Then m2=(pK - p0 - m)2 should be  0: L. Littenberg – Varenna

  41. _ Optimized S/B vs. Signal for KOPIO(assuming SM B(KL0 )) L. Littenberg – Varenna

  42. 1st yr 2nd yr 3rd yr KOPIO: SM Precision L. Littenberg – Varenna

  43. Discovering New Physics - Early L. Littenberg – Varenna

  44. Constraining New Physics - Early L. Littenberg – Varenna

  45. 3rd yr 1st yr 2nd yr Discovering/Constraining New Physics L. Littenberg – Varenna

  46. KOPIO Summary & Outlook • Excellent discovery potential for non-SM physics • Unique connection with underlying parameters • Extremely rapid progress in first part of run • Experiment background rejection scoped for 10-11 • 5 discovery if BR 0.6< BRSM or >1.7 BRSM • If find Br ~ BrSM • Likelihood analysis using ~150 evts • Precision on BR: 14%; Im t: 7% • Rule out non-SM effects outside (1  0.24)  BRSM • Unique constraint on some BSM operators L. Littenberg – Varenna

  47. _ A New Challenge: K _ • Another clean short-distance dominated decay • Related to Ke4 the way K is related to Ke3 • Calc. by Geng et al., also by Valencia & LL. Latter obtain: • B(KL+-)  [1.8(1.4-)2 + 0.32]  10-13 • B (KL00)  (1.4-)2  10-13 • B (K++0)  [0.7(1.4-)2 + 0.72]  10-14 • Very interesting angular distributions in +- case •  and  terms correspond to different l states, therefore in principle can extract  and  separately • In practice -  term dominates almost completely • KL+- major experimental challenge: • Must reject KL+- 0 by >1012, K3 by similar factor. • Must reject KL+- by >108 • Best to get into KL c.m.(only at low momenta) •  veto & particle ID usually best at high momenta • KL00 seems even harder, but has certain advantages • Detector can focus on  detection & vetoing, KL00 suppressed • Experiments seeking KL0 can add this to their menu. • K++0 was the first to have been probed L. Littenberg – Varenna

  48. E391a limit on KL00 Data Signal MC signal box PT PT normalization box m (GeV/c2) m (GeV/c2) No events seen, normalized via KL00, BR<3.210-5 @ 90% CL (preliminary) One day run, ~100 times more data will be available, half with better quality L. Littenberg – Varenna

  49. E787 search for K++0 Target of opportunity in monitoring data for K++ Data Signal MC No events observed, 90% CL limit established: B (K++0)< 4.3 10-5 Far short of SM expectation, but comparable to K++-e+ Can also get limits on non-SM process K++0X0 L. Littenberg – Varenna

  50. Short distance part of B(KL+-) given by: KL+- where  is a kinematic factor  1, Y(xt) 1.02(mt/170)1.56, & YNL  310-4 = 1.7510-9A4Y2(xt)(0-)2 = (0.960.10) 10-9 (where 01.2) So could potentially measure  or be sensitive to BSM physics KL+- K3 Moreover there’s a very good measurement by AGS-871 (6000 events!) But a number of roadblocks need to be overcome: 1. B(KL+-) dominated by absorptive contribution from KL 2. Much larger than the dispersive part that contains BSD! 3. Long-distance dispersive part interferes with short-distance contribution L. Littenberg – Varenna

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