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

FPCP 2003, Paris June 5 th, 2003M. Sozzi - Kaon physics Outline Re(  ’/  ): the quest for direct CP violation Rare K L decays and CP violation Rare K S decays and CP violation T-odd correlations: beyond the SM Loop-induced decays and unitarity triangle Future projects Conclusions ?

FPCP 2003, Paris June 5 th, 2003M. Sozzi - Kaon physics 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!)

FPCP 2003, Paris June 5 th, 2003M. Sozzi - Kaon physics The Quest for Direct 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?”

FPCP 2003, Paris June 5 th, 2003M. Sozzi - Kaon physics E832 (KTeV) at FNAL Double K L beams ( =70 GeV/c) Regenerator for K S Pure CsI calorimeter Tagging by event position MC acceptance correction Maximize statistics

FPCP 2003, Paris June 5 th, 2003M. Sozzi - Kaon physics NA48 at CERN Simultaneous near/far targets Converging beams ( =100 GeV/c) Liquid Kr calorimeter Tagging by time-of-flight Lifetime weighting to minimize acceptance correction

FPCP 2003, Paris June 5 th, 2003M. Sozzi - Kaon physics Data Taking Periods NA48:  ’/   ’/   ’/  low intensity KSKS KSKS KSKS NA48/1: K S KLKL no spectrometer NA48/2: K  CERN-NA48 FNAL-KTeV 1996  ’/  Rare  ’/  =  ’/  results Total: 5.3M K L  0  0 Total: 7.1M K L  0  0

FPCP 2003, Paris June 5 th, 2003M. Sozzi - Kaon physics Ways towards direct CPV NA48: TOF tagging KTeV: MC incoherent regeneration

FPCP 2003, Paris June 5 th, 2003M. Sozzi - Kaon physics Re(  ’/  ) Results Final result ( ) Half statistics (1997) Direct CP violation proved at >7  level… after 36 years! Wait for further results from KTeV and KLOE  2 =6.2/3

FPCP 2003, Paris June 5 th, 2003M. Sozzi - Kaon physics Re(  ’/  ) and the SM Despite huge efforts,  ’/  not yet computed reliably Measured value is roughly compatible with the SM Expect improvements from lattice Date of exp. measurement SM theoretical predictions Exp. value

FPCP 2003, Paris June 5 th, 2003M. Sozzi - Kaon physics Other kaon Parameters KTeV  m = (5261  15)  10 6 ħ s -1  S = (89.65  0.07)  s  +   SW = (0.61  1.19)º  00  +  = (0.39  0.50)º Im(  ’/  ) = (  22.9  29.1)  NA48:  S = (89.60  0.07)  s CPT

FPCP 2003, Paris June 5 th, 2003M. Sozzi - Kaon physics Semileptonic Charge Asymmetry NA48 2  10 8 events in 2001 run Preliminary KTeV 3  10 8 events in 2001 run Measure of indirect CP violation in the mixing (  ) and limits on CPT and  S=  Q  L (e) = (3.317   0.072)   L (e) = (3.322   0.047)  CPT test using  data: Re(y+x  /2+a) = (  5  31)  10 -6

FPCP 2003, Paris June 5 th, 2003M. Sozzi - Kaon physics KLOE at DA  NE Peak luminosity: 8  cm -2 s -1 in 2002 Goal: 5  cm -2 s pb -1 (1.5  10 9  ) collected so far Good prospects for rare K S decays, interferometry, new IR BR(K      0  0 ) = (1.807   0.018)%  (KS  +   (  ))/  (KS  0  0 ) = (2.236   0.015)  0   2  (48  3)  from which (2000 data)

FPCP 2003, Paris June 5 th, 2003M. Sozzi - Kaon physics KLOE results BR(K S  e ) = (6.81  0.12  0.10)   S = (1.9  1.7  0.6)  Re(x + ) = (3.3  5.2  3.5)  K S semileptonic charge asymmetry  S=  Q in CPT-conserving amplitudes Using K L -crash tagging of K S : Preliminary E865 KLOE K S KLOE K L K+e3K+e3 K0e3K0e3 K+3K+3 K03K03 |V us |f + (0) V us (2001 data) K S K L         tt QM interference

FPCP 2003, Paris June 5 th, 2003M. Sozzi - Kaon physics E799-II (KTeV): Rare K L decays Intense KL flux allows sensitive searches; checks of  PT K L  e + e -  (1997, 93K events – norm.  0  0  0 D ): K L  e + e - e + e - ( , 1K events – norm  0  0 D  0 D ): no CP violation found in decay plane asymmetry K L  e + e -  +  - ( , 132 events – norm  +  -  0 D ): New results expected soon with full data sample: K L  e + e - e + e - and K L  e + e -  form factors, K L   +  - e + e - update BR(K L  e + e -  ) = (10.13  0.04  0.06  0.29 norm )  BR(K L  e + e - e + e - ) = (4.07  0.12  0.11  0.16 norm )  Preliminary BR(K L  e + e -  +  - ) = (2.69  0.24  0.12)  Preliminary

FPCP 2003, Paris June 5 th, 2003M. Sozzi - Kaon physics K L,S      e  e  : why? CPV inner bremsstrahlung CPC direct emission CPV direct emissionCharge radius For K L : 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

FPCP 2003, Paris June 5 th, 2003M. Sozzi - Kaon physics K L,S      e  e  KTeV: K L NA48: K S,K L 1.5K events BR = (3.63  0.18)  No asymmetry: A  = (  1.1  4.1)% BR = (4.69  0.30)  [NA48: BR = (3.08  0.2)  ] A  = (13.3  1.7)% [NA48: A  = (14.2  3.6)%]

FPCP 2003, Paris June 5 th, 2003M. Sozzi - Kaon physics NA48/1 – Rare KS decays First measurement of K S   0  31 events, 13.6 background BR(K S   0  ) z>0.2 = (4.9  1.6  0.8)  Preliminary 30% higher than  PT prediction For both: first contribution at O(p 4 ) in  PT Indications of large O(p 6 ) terms BR(K S   ) = (2.78  0.02  0.04)  Not yet sensitive to chiral structure of weak vertex

FPCP 2003, Paris June 5 th, 2003M. Sozzi - Kaon physics NA48/1 - Search for K S   0 e + e - Determines indirect CP-violating contribution to K L   0 e + e - decay Published limit from 1999 data: BR(K S   0 e + e - ) < 1.4  (90% CL) Signal region 2001 K S run data analyzed - Result available very soon

FPCP 2003, Paris June 5 th, 2003M. Sozzi - Kaon physics Search for K S  3  0 Expectation   Im (  000 ) sensitive to direct CPV CPLEAR (1999) Re(  000 ) = 0.18  0.15 Im(  000 ) = 0.15  0.20 SND, Novosibirsk (1999) BR(K S  3  0 ) < 1.4  Hadron machines: search for interference term

FPCP 2003, Paris June 5 th, 2003M. Sozzi - Kaon physics NA48/1: K S  3  0 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 BR(K S  3  0 ) < 1.4  (90% CL) Preliminary Re(  000 ) = (  2.6  1.0  0.5)  Im(  000 ) = (  3.4  1.0  1.1)  Im(  000 ) = (  1.2  0.7  1.1)  10 -2

FPCP 2003, Paris June 5 th, 2003M. Sozzi - Kaon physics m(K 0 )  m(K 0 ) = (  1.7  4.2)  GeV/c 2 Largest contribution to the error from f = 3  0 After NA48/1: Im(  ) = (  1.2  3.0)  CPT Test From K S  3  0 Bell-Steinberger relation (unitarity) connects indirect CPT violation  to CP-violating decays Assuming no CPT violation in the decay: Preliminary

FPCP 2003, Paris June 5 th, 2003M. Sozzi - Kaon physics KEK E246: T-violation in K +   0   Search for P T (  ) orthogonal to (  ) decay plane FSI in SM give P T < : probe of New Physics 660 MeV/c kaons stopped in absorber Combined result from 8.3M decays ( ): P T (  ) = (-1.12  2.17  0.9)  LOI to reach accuracy at J-PARC

FPCP 2003, Paris June 5 th, 2003M. Sozzi - Kaon physics NA48/2 – K  decays 60 GeV/c  5% 0º prod. angle Beam spectrometer New simultaneous K+ and K- narrow band beam Kaon momentum spectrometer

FPCP 2003, Paris June 5 th, 2003M. Sozzi - Kaon physics NA48/2 – K  physics Search for direct CP violation in K      +   and    0  0 Dalitz plot slope asymmetries:  (  g/2g)  2  (SM, SUSY: to ) Exploit “double ratio” cancellations Precise measurement of  interaction in K e4 decays (>10 6 )  (a 0 0 )  0.01 Rare K  decays and CP violation  K  decays expected Currently taking data

FPCP 2003, Paris June 5 th, 2003M. Sozzi - Kaon physics Protvino - K  New RF-separated beam at U-70 PS in construction 15 GeV/c kaons, alternating K+ or K- Magnetic detector evolved from ISTRA+, GAMS In preparation, expected 2004 Measurement of 3  Dalitz plot 1  T-odd correlations, search for New Physics in K l2 decays

FPCP 2003, Paris June 5 th, 2003M. Sozzi - Kaon physics HyperCP: K         Main goal: CP violation in hyperon decays Collected large samples of K  decays K         : FCNC GIM-suppressed loops Dominated by long- distance effects BR(K         ) = (9.8  1.0  0.5)  A  (K         ) =  0.02  0.11  0.04 From 1997 statistics (  1/5): Preliminary

FPCP 2003, Paris June 5 th, 2003M. Sozzi - Kaon physics The golden modes: K   FCNC, loop-induced, GIM-suppressed in SM Sensitive to New Physics MOREOVER: No long-range contributions QCD corrections under control Single H eff operator with matrix element linked to K e3 BUT: BR  , unconstrained kinematics, huge backgrounds Dedicated efforts required!

FPCP 2003, Paris June 5 th, 2003M. Sozzi - Kaon physics Kaons and the unitarity triangle Comparison to B constraints (10% on BR): Errors on , V td : better from B Errors on , sin2  : similar to B-factories Error on t : always better from K A. Buras, hep-ph/

FPCP 2003, Paris June 5 th, 2003M. Sozzi - Kaon physics Three contributions: 1) CP-conserving through K L   0  *  * estimate from K L   0  (KTeV/NA48 disagreement?) 2) Indirect CP-violating through K S   0 l + l - Not suppressed, unlike the case: measure from K S   0 l + l - (NA48 for e + e - ) 3) “Direct” CP-violating, short-distance, reliably predicted and interfering with (2): BR=4.3  (e + e - ), 0.9  (  +  - ). (3) is smaller by  5 for the  +  - case “Greenlee” background K L   l + l - : BR=6  (e + e - ), 1  (  +  - ) The rare decays K L   0 l + l -

FPCP 2003, Paris June 5 th, 2003M. Sozzi - Kaon physics KL  0e+eKL  0e+e expected Exp. Limits from KTeV (90% CL): Measurement requires accurate background subtraction BR(K L   0 e + e - ) < 2.8  BR(K L   0  +  - ) < 3.8  BR(Direct CPV)  Measured BR  L. Littenberg, hep-ex/

FPCP 2003, Paris June 5 th, 2003M. Sozzi - Kaon physics BNL E787: K +   + Theoretical prediction in the SM: BR(K +   + ) = 7.2  with small (  7%) uncertainty BR(K +   + ) =  0.82  Stopped K, redundant measurements Detection of  e chain Momentum region between  and  peaks Final result: 2 events (0.15 bkg.) Improved successor BNL E949 ran in 2002

FPCP 2003, Paris June 5 th, 2003M. Sozzi - Kaon physics Future: CKM at FNAL In-flight measurement RF-separated 22 GeV/c K + beam Redundant measurements to overconstrain kinematics (spectrometers + RICHs) Progress on RF-cavities, photon vetos, straws in vacuum Goal: 100 SM events in 2 years (S/B  10) Data taking in 2007

FPCP 2003, Paris June 5 th, 2003M. Sozzi - Kaon physics K L   0 Current KTeV limit: BR(K L   0 ) < 5.9  (90% CL) Using  0   e + e - decay No CP-conserving term Indirect CP-violating term negligible Theoretical prediction within the SM: BR(K L   0 ) = 2.7  With tiny (  2%) uncertainty Model independent bound

FPCP 2003, Paris June 5 th, 2003M. Sozzi - Kaon physics KEK E391a: K L   0 Pilot project at KEK-PS 2 GeV/c “pencil” beam: P T cut against  0  0 to reduce veto requirement to Double decay chamber, 10% acceptance “Engineering run” in fall 2002: CsI calibration, K L  0  0,  0  0  0 First data run in 2004 (4 months)

FPCP 2003, Paris June 5 th, 2003M. Sozzi - Kaon physics K L   0 at J-PARC J-PARC schedule: physics start in GeV (30-40 at start) 2  p/3.42 s 2 beam lines foreseen in K-hall 2 GeV/c K L (1.1  10 9 /pulse) 16% acceptance Goal: 1000 SM events

FPCP 2003, Paris June 5 th, 2003M. Sozzi - Kaon physics KOPIO at BNL : K L   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

FPCP 2003, Paris June 5 th, 2003M. Sozzi - Kaon physics KOPIO at BNL Several feasibility results achieved: Beam bunching performance proved (280 ns, goal: 200 ns) 25 mrad resolution with preradiator Veto efficiency performances Construction from 2006 Expect 40 SM events (S/B  2)

FPCP 2003, Paris June 5 th, 2003M. Sozzi - Kaon physics How is kaon physics? CERN: NA48 (K L ) NA48/1 (K S ) analysis, NA48/2 (K  ) running FNAL: KTeV (K L ) and HyperCP (K  ) analysis, CKM (K + ) in preparation BNL: E949 (K + ) analysis, KOPIO (K L ) in preparation KEK: E246 (K + ) analysis, E391a (K L ) ready to run Frascati: KLOE (K L,S, K  ) running, upgrades? Protvino: OKA (K  ) in preparation Novosibirsk: VEPP-2000 machine (K L,S, K  ) in preparation J-PARC: Neutral K beam line foreseen Alive and kicking!

FPCP 2003, Paris June 5 th, 2003M. Sozzi - Kaon physics 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

FPCP 2003, Paris June 5 th, 2003M. Sozzi - Kaon physics Spare slides

FPCP 2003, Paris June 5 th, 2003M. Sozzi - Kaon physics KL  eeKL  ee KTeV: K L BR = (3.63  0.18)  A  = (13.3  1.7)% Large CP-violating asymmetry seen

FPCP 2003, Paris June 5 th, 2003M. Sozzi - Kaon physics KS  eeKS  ee NA48: K S First measurement No asymmetry for K S BR = (4.69  0.30)  A  = (-1.1  4.1)%

FPCP 2003, Paris June 5 th, 2003M. Sozzi - Kaon physics KTeV limits on K L   0 BR(K L   0 ) < 5.9  (90% CL) Using  0   e + e - decay (0.12 events bkg.) BR(K L   0 ) < 1.6  (90% CL) Using  0   decay (3.7 events bkg.)

FPCP 2003, Paris June 5 th, 2003M. Sozzi - Kaon physics 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