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Kaon Physics: Experimental Status and Perspectives

Kaon Physics: Experimental Status and Perspectives. Marco S. Sozzi CERN and Scuola Normale Superiore, Pisa. FPCP 2003, Paris – June 5 th 2003. Outline. Re( ’/ ): the quest for direct CP violation Rare K L decays and CP violation Rare K S decays and CP violation

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Kaon Physics: Experimental Status and Perspectives

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  1. Kaon Physics:Experimental Status and Perspectives Marco S. Sozzi CERN and Scuola Normale Superiore, Pisa FPCP 2003, Paris – June 5th 2003 M. Sozzi - Kaon physics

  2. Outline • Re(’/): the quest for direct CP violation • Rare KL decays and CP violation • Rare KS decays and CP violation • T-odd correlations: beyond the SM • Loop-induced decays and unitarity triangle • Future projects • Conclusions ? M. Sozzi - Kaon physics

  3. Still kaons? • The “minimal” flavour-laboratory • An amazing interferometric system • Long lifetime, few decay modes, large mixing • Both mass and flavour eigenstates accessible • All kinds of CP violation present • Difficulties in linking measurements to theory (not always!) M. Sozzi - Kaon physics

  4. The Quest forDirect CP Violation Indirect CP violation in the mixing:  Direct CP violation in the decay: ’ A fascinating 30-year long enterprise: “Is CP violation a peculiarity of kaons? Is it induced by a new superweak interaction?” M. Sozzi - Kaon physics

  5. E832 (KTeV) at FNAL Double KL beams (<p>=70 GeV/c)Regenerator for KSPure CsI calorimeterTagging by event positionMC acceptance correctionMaximize statistics M. Sozzi - Kaon physics

  6. NA48 at CERN Simultaneous near/far targetsConverging beams (<p>=100 GeV/c)Liquid Kr calorimeterTagging by time-of-flightLifetime weighting to minimize acceptance correction M. Sozzi - Kaon physics

  7. = ’/results Data Taking Periods ’/ Total: 5.3M KL00 1996 NA48: ’/ ’/ Rare Rare 1997 ’/ 1998 ’/ ’/ KS Rare 1999 no spectrometer 2000 KL KS FNAL-KTeV ’/low intensity 2001 KS Total: 7.1M KL00 2002 NA48/1: KS 2003 NA48/2: K CERN-NA48 M. Sozzi - Kaon physics

  8. Ways towards direct CPV NA48:TOF tagging KTeV: MCincoherent regeneration M. Sozzi - Kaon physics

  9. Re(’/) Results 2=6.2/3 Final result (1997-2001) Half statistics (1997) Direct CP violation proved at >7 level…after 36 years! Wait for further results from KTeV and KLOE M. Sozzi - Kaon physics

  10. Date of exp. measurement Re(’/) and the SM SM theoretical predictions Exp. value Despite huge efforts, ’/ not yet computed reliablyMeasured value is roughly compatible with the SMExpect improvements from lattice M. Sozzi - Kaon physics

  11. Other kaon Parameters KTeVm = (5261  15)  106ħ s-1S = (89.65  0.07)  10-12 s+SW = (0.61 1.19)º00 += (0.39 0.50)ºIm(’/) = (22.9  29.1)  10-4 CPT NA48: S = (89.60  0.07)  10-12 s M. Sozzi - Kaon physics

  12. Semileptonic Charge Asymmetry Measure of indirect CP violation in the mixing () and limits on CPT and S=Q Preliminary NA482  108 events in 2001 run L(e) = (3.317  0.070  0.072)  10-3 KTeV3  108 events in 2001 run L(e) = (3.322  0.058  0.047)  10-3 CPT test using  data: Re(y+x/2+a) = ( 5  31)  10-6 M. Sozzi - Kaon physics

  13. KLOE at DANE (KS +())/(KS 00)= (2.236  0.003  0.015) from which (2000 data) 0  2 (48  3) BR(K   00) = (1.807  0.008  0.018)% Good prospects for rare KS decays, interferometry, new IR Peak luminosity: 81031 cm-2 s-1 in 2002Goal: 51032 cm-2 s-1500 pb-1 (1.5 109 ) collected so far M. Sozzi - Kaon physics

  14. K+e3 K0e3 K+m3 K0m3 E865 KLOE KS KLOE KL |Vus|f+(0) KLOE results Using KL-crash tagging of KS: Preliminary (2001 data) S = (1.9  1.7  0.6)  10-2 KS semileptonic charge asymmetry Re(x+) = (3.3  5.2  3.5)  10-3 S=Q in CPT-conserving amplitudes BR(KSe) = (6.81  0.12  0.10)  10-4 QM interference Vus KS KLp+p-p+p- t M. Sozzi - Kaon physics

  15. E799-II (KTeV): Rare KL decays Intense KL flux allows sensitive searches; checks of PT KLe+e- (1997, 93K events – norm. 000D): KL e+e- e+e- (1997+1999, 1K events – norm 00D0D): no CP violation found in decay plane asymmetryKLe+e-+- (1997+1999, 132 events – norm +-0D): New results expected soon with full 1997+1999 data sample:KL e+e- e+e- and KLe+e- form factors, KL +- e+e- update Preliminary BR(KL e+e-) = (10.13  0.04  0.06  0.29norm)  10-6 Preliminary BR(KL e+e-e+e-) = (4.07  0.12  0.11  0.16norm)  10-8 BR(KL e+e-  + -) = (2.69  0.24  0.12)  10-9 M. Sozzi - Kaon physics

  16. CPV inner bremsstrahlung CPC direct emission CPV direct emission Charge radius KL,S ee : why? For KL: interference gives indirect CP-violating asymmetry in the orientation of  and eedecay planes Easier access to polarization asymmetry in K  Large ( 14%) asymmetries predicted M. Sozzi - Kaon physics

  17. KL,S ee A = (13.3  1.7)% KTeV: KL [NA48:A = (14.2  3.6)%] 1.5K events BR = (3.63  0.18)  10-7 [NA48: BR = (3.08  0.2)  10-7] BR = (4.69  0.30)  10-5 NA48: KS,KL No asymmetry:A = (1.1  4.1)% M. Sozzi - Kaon physics

  18. NA48/1 – Rare KS decays First measurement of KS  031 events, 13.6 background Preliminary BR(KS  0)z>0.2 = (4.9  1.6  0.8)  10-8 30% higher than PT prediction Not yet sensitive to chiral structure of weak vertex BR(KS  ) = (2.78  0.02  0.04)  10-6 For both: first contribution at O(p4) in PTIndications of large O(p6) terms M. Sozzi - Kaon physics

  19. Signal region NA48/1 - Search for KS0e+e- Determines indirect CP-violating contribution toKL 0e+e- decay Published limit from 1999 data:BR(KS 0e+e-) < 1.410-7 (90% CL) 2001 KS run data analyzed - Result available very soon M. Sozzi - Kaon physics

  20. Search for KS30 Expectation  Im (000) sensitive to direct CPV CPLEAR (1999)Re(000) = 0.18  0.15Im(000) = 0.15  0.20 SND, Novosibirsk (1999)BR(KS30) < 1.410-5 Hadron machines: search for interference term M. Sozzi - Kaon physics

  21. NA48/1: KS30 Re(000) = (2.6  1.0  0.5)  10-2Im(000) = (3.4  1.0  1.1)  10-2 Preliminary • Data from 2000 run • Use near-target data: 6.5M 30 events • Normalize to far-target data: 155M 30 events • Correct residual acceptance difference with MC Im(000) = (1.2  0.7  1.1)  10-2 BR(KS30) < 1.410-6 (90% CL) M. Sozzi - Kaon physics

  22. CPT Test From KS30 Bell-Steinberger relation (unitarity) connects indirect CPT violation  to CP-violating decays Largest contribution to the error from f = 30After NA48/1: Im() = (1.2  3.0)  10-5 Preliminary Assuming no CPT violation in the decay: m(K0)  m(K0) = (1.7  4.2)  10-19 GeV/c2 M. Sozzi - Kaon physics

  23. KEK E246: T-violation in K+ 0 Search for PT() orthogonal to () decay planeFSI in SM give PT < 10-5: probe of New Physics 660 MeV/c kaons stopped in absorber Combined result from 8.3M decays (1996-2000): PT() = (-1.12  2.17  0.9)  10-3 LOI to reach 10-4 accuracy at J-PARC M. Sozzi - Kaon physics

  24. NA48/2 – Kdecays 0º prod. angle 60 GeV/c 5% Beam spectrometer New simultaneous K+ and K- narrow band beamKaon momentum spectrometer M. Sozzi - Kaon physics

  25. NA48/2 – Kphysics • Search for direct CP violation in K  + and 00Dalitz plot slope asymmetries: (g/2g)  210-4 (SM, SUSY: 10-4 to 10-6) Exploit “double ratio” cancellations • Precise measurement of  interaction in Ke4 decays (>106) (a00)  0.01 • Rare K decays and CP violation • 1011K decays expected Currently taking data M. Sozzi - Kaon physics

  26. OKA @ Protvino - K New RF-separated beam at U-70 PS in construction15 GeV/c kaons, alternating K+ or K-Magnetic detector evolved from ISTRA+, GAMSIn preparation, expected 2004Measurement of 3 Dalitz plot asymmetries @ 1 10-4T-odd correlations, search for New Physics in Kl2 decays M. Sozzi - Kaon physics

  27. HyperCP: K  Main goal: CP violation in hyperon decaysCollected large samples of K decays K : FCNC GIM-suppressed loopsDominated by long-distance effects Preliminary BR(K ) = (9.8  1.0  0.5)  10-8 From 1997 statistics (1/5): A(K ) = 0.02  0.11  0.04 M. Sozzi - Kaon physics

  28. The golden modes: K   FCNC, loop-induced,GIM-suppressed in SMSensitive to New Physics MOREOVER:No long-range contributionsQCD corrections under controlSingle Heff operator with matrix element linked to Ke3 BUT:BR  10-11, unconstrained kinematics, huge backgrounds Dedicated efforts required! M. Sozzi - Kaon physics

  29. Kaons and the unitarity triangle • Comparison to B constraints (10% on BR): • Errors on , Vtd:better from B • Errors on , sin2:similar to B-factories • Error on t:always better from K A. Buras, hep-ph/9905437 M. Sozzi - Kaon physics

  30. The rare decays KL0l+l- Three contributions: 1) CP-conserving through KL0**estimate from KL  0 (KTeV/NA48 disagreement?) 2) Indirect CP-violating through KS 0l+l-Not suppressed, unlike the  case: measure from KS 0l+l- (NA48 for e+e- ) 3) “Direct” CP-violating, short-distance, reliably predicted and interfering with (2): BR=4.310-12 (e+e-), 0.910-12 (+-). (3) is smaller by  5 for the +- case “Greenlee” background KLl+l-: BR=610-7 (e+e-), 1 10-7 (+-) M. Sozzi - Kaon physics

  31. KL0e+e Exp. Limits from KTeV (90% CL): BR(KL 0e+e-) < 2.810-10BR(KL 0+-) < 3.810-10 Measured BR 10-12 Measurement requires accurate background subtraction BR(Direct CPV) 10-12 L. Littenberg, hep-ex/0212005 expected M. Sozzi - Kaon physics

  32. BNL E787: K+ + Theoretical prediction in the SM:BR(K+ +) = 7.2 10-11with small ( 7%) uncertainty Stopped K, redundant measurementsDetection of e chainMomentum region between  and  peaks Final result: 2 events (0.15 bkg.) BR(K+ +) = 1.56+1.750.82 10-10 Improved successor BNL E949 ran in 2002 M. Sozzi - Kaon physics

  33. Future: CKM at FNAL In-flight measurementRF-separated 22 GeV/c K+ beamRedundant measurements to overconstrain kinematics(spectrometers + RICHs)Progress on RF-cavities, photon vetos, straws in vacuumGoal: 100 SM events in 2 years (S/B  10)Data taking in 2007 M. Sozzi - Kaon physics

  34. KL 0 No CP-conserving termIndirect CP-violating term negligibleTheoretical prediction within the SM:BR(KL 0) = 2.710-11With tiny ( 2%) uncertainty Model independent bound Current KTeV limit:BR(KL 0) < 5.9 10-7 (90% CL)Using 0  e+e- decay M. Sozzi - Kaon physics

  35. KEK E391a: KL 0 Pilot project at KEK-PS2 GeV/c “pencil” beam: PT cut against 00to reduce veto requirement to 10-4Double decay chamber, 10% acceptance“Engineering run” in fall 2002:CsI calibration, KL00, 000First data run in 2004 (4 months) M. Sozzi - Kaon physics

  36. KL 0 at J-PARC J-PARC schedule: physics start in 200850 GeV (30-40 at start) 21014p/3.42 s 2 beam lines foreseen in K-hall2 GeV/c KL (1.1109/pulse)16% acceptanceGoal: 1000 SM events M. Sozzi - Kaon physics

  37. KOPIO at BNL : KL 0 800 MeV/c microbunched kaon beam Pb-scint. veto system (10-4) complemented by:KL momentum from TOF direction from pre-radiator(wires+scint. layers)“Pancake” beam M. Sozzi - Kaon physics

  38. KOPIO at BNL Several feasibility results achieved:Beam bunching performance proved (280 ns, goal: 200 ns)25 mrad resolution with preradiatorVeto efficiency performancesConstruction from 2006 Expect 40 SM events (S/B  2) M. Sozzi - Kaon physics

  39. How is kaon physics? CERN: NA48 (KL) NA48/1 (KS) analysis, NA48/2 (K) running FNAL: KTeV (KL) and HyperCP (K) analysis, CKM (K+) in preparation BNL: E949 (K+) analysis, KOPIO (KL) in preparation KEK: E246 (K+) analysis, E391a (KL) ready to run Frascati: KLOE (KL,S, K) running, upgrades? Protvino: OKA (K) in preparation Novosibirsk: VEPP-2000 machine (KL,S, K) in preparation J-PARC: Neutral K beam line foreseen Alive and kicking! M. Sozzi - Kaon physics

  40. Conclusions? Once upon a time, kaons delivered many surprises and precious insight… … they are still doing so today, and they will in the near future! CPV M. Sozzi - Kaon physics

  41. Spare slides M. Sozzi - Kaon physics

  42. KL ee KTeV: KL A = (13.3  1.7)% BR = (3.63 0.18)  10-7 Large CP-violating asymmetry seen M. Sozzi - Kaon physics

  43. KS ee NA48: KS A = (-1.1  4.1)% First measurement BR = (4.69 0.30)  10-5 No asymmetry for KS M. Sozzi - Kaon physics

  44. KTeV limits on KL 0 BR(KL 0) < 5.9 10-7 (90% CL)Using 0  e+e- decay(0.12 events bkg.) BR(KL 0) < 1.6 10-6 (90% CL)Using 0   decay(3.7 events bkg.) M. Sozzi - Kaon physics

  45. KTeV: ’/ improvements Several improvements in the analysis to reduce systematic errors: DCH simulation, alignment, reconstruction Use of angles and improvements for overlapping showers in CsI reconstruction Stat. Error  110-4 M. Sozzi - Kaon physics

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