LNF Scientific Committee May 2003

1. Kaon Physics at KLOE Claudio Gatti for the KLOE Collaboration • Kaons at KLOE • Kaon Physics • Neutral Kaons • Charged Kaons • Conclusions LNF Scientific Committee May 2003

2. KS(+)  KL(-) Kaons at KLOE • The  decays at rest allow us to select monochromatic (p ~ 110 MeV/c) pure beams of Kaons: • K rare decays. • Absolute branching ratios: • K life times: • The variety of K decay channels and the possibility for a complete closure of the kinematics allow the selection of many samples for measuring the efficiencies directly from data. lL ~ 340 cm lS ~ 0.6 cm l  ~ 95 cm K+K- 1.5 106/pb-1 KLKS 106/pb-1

3. CP Kaon Physics Rare Vus p+p-p0 KS p+p-(g)/p0p0 mS peu p0p0p0 p+p- gg tL l+,0 KL plu p0p0 pp0p0 pp0 t± l+,0 plu K± p0p0e±u mu

4. |Vus|•|f+(0)| t± For Ke3 modes: exp th VUS Introduced in 1963, known to 1.5% |VUS| = 0.2196±0.0019exp±0.0018th With ~ 400 pb-1 and taking eficiencies into account ~ 1-3106 Kl3 decays of each kind. We can measure: All branching ratios well below 10-2

5. BR(KLgg) / BR(KLp0 p0 p0) KLgg KLOE note182 regeneration KLp0 p0 p0 36 pb-1 312 pb-1 KLOE: tL = 51.5±0.5 ns PDG: tL = 51.7±0.4 ns R=(2.79±0.02stat±0.02syst)10-3 hep-ex/0305035 Submitted to PLB

6. CMD-2 ’99 PDG eval. from KL KLOE ’02 KLOE ’03 prelim. 6 7 8 10-4 KSe branching ratio Data ~170 pb-1 BR(p-e+u)=(3.440.09stat0.06syst)10-4 BR(p+e-u)=(3.310.08stat0.05syst)10-4 BR(peu) =(6.760.12stat0.10syst)10-4 preliminary

7.  CPT SM: KSe charge asymmetry preliminary First measurement of As! AS=(19±17stat±6syst)10-3 Compare with kTeV AL=(3.322±0.058stat±0.047syst)10-3 With  2 fb-1 dK below 10-3 KSe DS = DQ rule Rex+ = (2.2±5.3stat±3.5syst)10-3 Previous measurement: CPLEAR Rex+ = (-1.8±4.1stat±4.5syst)10-3

8. Radiative corrections New MC generators for pp and Ke3 decays including radiated photon, without any cutoff on the energy. The fraction of events in the tail is in agreement with present experimental knowledge. ppg N(Eg >50 MeV)/NTOT = 2.6x10-3 A clear definition of the treatment of radiative corrections is needed for VUS.

9. m- K- g K+ e+ g m2 (MeV2) Charged Kaons Tag on one side with: K or K self-triggering PID using DC and EmC Developed methods for extracting efficiencies from data

10.   0 + K+  – K– 0 0    t’ decay • Absolute branching ratio presently known to 2% • Efficiencies from data 187 pb-1 event counting 250 pb-1efficiency estimate ~ 80000 ev BR(K±±00) = (1.781±0.013stat±0.016syst)% preliminary KLOE note 187 PDG (1.73±0.04)% With 2 fb-1 BR to 0.3%

11. tg tg tg tg p0 p0 p± Kmntag Kmntag p0 p0 tg tg tg t’ decay: efficiencies VTX andTRK efficiencies measured in t’ decays selected using only photon clusters Cluster efficiency from ±0 decays, selected looking for the charged pion and only one photon in the EmC Similar techniques will be applied to Ke3, Ke4 decays

12. Conclusions • With ~ 500 pb-1 last year we measured: • KS semieptonic decay, BR, AS to 2% and tested S=Q rule. • KL BR to 2%. In ageement with NA48.Alsofirst look at KL lifetime. • K±±00 absolute BR to 1%. First look also at Ke4! • Beside these results, we learned how to handle background and developed many techniques to measure the efficiencies. • Moreover, all the relevant radiative corrections will be included in the MC simulation, which are as important as statistics for precise measurements.  and Ke3 generators are implemented without any cutoff on photon energy. • We have all the tools for measuring |VUS|•f+(0) in all semileptonic channels, and to begin analyses on the forthcoming 2 fb-1 physics.

13. Perspectives Published results

14. gg events 100% 98% Data/MC R(cm) Old MC New MC Fiducial region T (ns) MC improvements Efficiencies extracted from data. However, a correct MC simulation will help in reducing corrections and in bkg evaluation. Accidental cluster and DC hits extracted from data (gg) and inserted into MC. DC and EmC geometry corrected. EmC response corrected. eTRK

15. Ke3g N = 106 ~3% Eg>30 Mev q> 20 N = 9319