1. Salvatore Fiore University of Rome La Sapienza & INFN Roma1 for the KLOE collaboration LNF Spring School “Bruno Touscheck”, Frascati, 15-19 May 2006 CP/CPT tests at KLOE

2. 2 Neutral kaons at a  -factory e + e     b  S = m  = 1019.4 MeV BR(  K 0 K 0 ) ~ 34% ~10 6 neutral kaon pairs per pb -1 produced in an antisymmetric quantum state with J PC = 1  K L K S 10 6 /pb -1 ; p* = 110 MeV/c S = 6 mm K S decays near interaction point L = 3.4 m Large detector to keep reasonable acceptance for K L decays (~0.3 L ) K + K - 1.5  10 6 /pb -1 p* = 127 MeV/c  ± = 95 cm

3. 3 Neutral kaons at a  -factory: tagging p K = 110 MeV/c S = 6 mm L = 3.5 m The detection of a kaon at large (small) times tags a K S (K L ) K L,S K S,L t1t1 t2t2  t=t 1 - t 2 f2f2 f1f1  not possible at fixed target possibility to select a pure K S beam (unique at a  - factory, not possible at fixed target experiments) The  decay at rest provides monochromatic and pure beam of kaons  Tagging: observation of K S,L signals  presence of K L,S - precision measurement of absolute BR’s

4. 4 DA  NE: the Frascati  -factory W = m  (1019.4 MeV) L design 5  10 32 cm -2 s -1 Data taking finished last March L peak = 1.3 × 10 32 cm  s  L tot  2.5 fb -1 2001 170 pb -1 2002 280 pb -1 2004 734 pb -1 2005 1256 pb -1

5. 5  Be beam pipe (spherical, 10 cm , 0.5 mm thick) + instrumented permanent magnet quadrupoles (32 PMT’s) Drift chamber (4 m   3.75 m, CF frame)  Gas mixture: 90% He + 10% C 4 H 10  12582 stereo sense wires  almost squared cells  Electromagnetic calorimeter  lead/scintillating fibers (1 mm  ), 15 X 0  4880 PMT’s  98% solid angle coverage Superconducting coil (B = 0.52 T) The KLOE design was driven by the measurement of direct CP through the double ratio: R =  (K L  +   )  (K S  0  0 ) /  (K S  +   )  (K L  0  0 ) KLOE experiment

6. 6 KLOE detector specifications  E /E  5.7% /  E(GeV)  t  54 ps /  E(GeV)  50 ps  vtx (  ) ~ 1.5 cm (   from K L        )  p /p  0.4 % (tracks with  > 45°)  x hit  150  m (xy), 2 mm (z)  x vertex ~1 mm  (M  ) ~1 MeV

7. 7 K S tagged by K L interaction in EmC Efficiency ~ 30% (largely geometrical) K S angular resolution: ~ 1° (0.3  in  ) K S momentum resolution: ~ 2 MeV K L “crash”  = 0.22 (TOF) K S    e  K S    e  K L tagged by K S      vertex at IP Efficiency ~ 70% (mainly geometrical) K L angular resolution: ~ 1° K L momentum resolution: ~ 2 MeV KS  KS  KS  KS   KL  2KL  2KL  2KL  2 K S and K L tagging

8. 8 BR K L      CP Violation CP violating decay Related to  K using K L beam tagged by K S →     328 pb -1 ’01+’02 data Selection K L vertex reconstructed in DC PID using decays kinematics Fit with MC spectra including radiative processes Normalization using K L   events in the same data set

9. 9 Preliminary result BR(K L      )= (1.963  0.012  0.017)  10 -3 in agreement with KTeV [PRD70 (2004),092006] BR=(1.975  0.012)   confirm the discrepancy (4 standard deviations) with PDG04 BR=(2.090  0.025)   PDG2004 KTeV KLOE preliminary BR(K L      )  10 -3 Using BR(K S   ) and  L from KLOE and  S from PDG04  | = (2.216  0.013)  10 -3 |  | PDG04 = (2.280  0.013)  10 -3 BR K L      CP Violation (II) 1.5  with respect to prediction from Unitarity Triangle

10. 10 K S K L observables Measurements of K S K L observables can be used for these tests:      K S       00    K S            K S       kl3  S  L B(K L l3)  Re  Re y  i( Im  Im x  )   S  L B(K L l3)  (A S +A L )/4  i( Im  Im x  )     S  L     K L           S  L     K L        CPT test: the Bell-Steinberger relation Exact relation: phase convention independent, no approx, in the CPT limit Looking at Im(  )  0 as CPTV signal

11. 11  K S      K S       K S        K L        K L  l   K S          K L         K S          SW  = (0.759±0.001)         CPT test: inputs to the Bell-Steinberger relation  S  0.08958 ± 0.00006 ns  L = 50.84 ± 0.23ns A L   A S    K L        K L         =0.757 ± 0.012   = 0.763 ± 0.014 Im x + = (0.8 ± 0.7)  10 -2 Im x  from a combined fit of KLOE + CPLEAR data

12. 12 We get the following results (error contours) on each term of the sum      K S       00    K S            K S       S  L B(K L l3)  A S +A L )/4  i  Im x      S  L     K L           S  L     K L        10 -4 Im Re CPT test: accuracy on  i

13. 13 Re    Im   CPLEAR: Re    Im   CPT test: B-S KLOE result KLOE preliminary: Re  Im 