1. KLOE general meeting 19-20 December 2002 Tor Vergata K charged status report DST production status New analysis items:  K + K - cross section/  line shape BR measurement strategy enhanced 2 body decay tag BR systematic vs cosmic veto

2. KLOE general meeting 19-20 December 2002 Tor Vergata K charged DST production  K charged DST production code has been finalized  Production started on a limited number of runs (~ 4.5 pb-1)  Energy scan runs are used as bench mark: DST produced directly from raw data ( not from streamed ) to avoid bias on the K + K - cross section analysis  Production now stopped due to the TAPE shortage

3. KLOE general meeting 19-20 December 2002 Tor Vergata Analysis items: Some items are brand new and the correlated job sharing/items assignment is not yet frozen; furthermore a lot of items overlap each other. A tentative and approximate job sharing list can be:  K + K - cross section : P.Branchini,B.Sciascia,L.Passalacqua K ±    0  0 : E.Gorini, M.Primavera, A.Ventura BR(K ±  )/BR(K ±  0 ): M.Martemianov, R.Versaci, V.Patera K e3, K  3 : E.De Lucia, P.De Simone, L.Passalacqua, B.Sciascia DST :production/check : all together

4. KLOE general meeting 19-20 December 2002 Tor Vergata Analysis :  line shape fit MeV  K + K - cross section points obtained counting events with single vs double K  0 decay Fit by M.Antonelli Both line shape and cross section value at peak must be checked using the new DST with retracking

5. KLOE general meeting 19-20 December 2002 Tor Vergata Analysis: BR measurement strategy Based on the tag mechanism: given an identified 2 body K ± decay on one emisphere (handle) then we look at K ± decay on the other side (signal) The tag decay must have triggered by itself the events so to cancel out  trigger from  ID of the signal To achieve emisphere separation only EMC trigger must be considered Also the  cluster of the K  decay can trigger firing two adjacent trigger sectors with good efficiency (30%) Two auto triggering tag types with different topologies allow good systematic checks

6. KLOE general meeting 19-20 December 2002 Tor Vergata K  auto trigger all  trg  all   energy (MeV) The high energy  cluster can stretch between two adjacent sector. The muon inpinges on the ECAL surface with an angle, going through 2 sectors   

7. KLOE general meeting 19-20 December 2002 Tor Vergata Tag statistic The request to have a clean “handle” (  clean 2 body decay auto triggering ) to study the K decay on the other side reduce our analysis sample. We evaluated our yeld on a 4.85 pb -1 sample, considering “signal” any K decay in FV with any charged track attached: Tag N/pb-1N trig /pb-1N signal /pb -1 N signal @ 200pb -1 K  0 9.5x10 4 7.3x10 4 1.7x10 4 3.4x10 6 K  2.79x10 5 9.5x10 4 2.3x10 4 4.6x10 6 total 3.74x10 5 1.87x10 5 4.0x10 4 8.0x10 6 70 MeV < P K < 130 MeV 20 cm > |z ip | 10 cm > R ip 40 cm < R vertex < 150 cm

8. KLOE general meeting 19-20 December 2002 Tor Vergata  tag vs  0 tag: signal shape The signal shape seems to be independent from the tag used as “handle” Red = K  Blue = K  0

9. KLOE general meeting 19-20 December 2002 Tor Vergata BR vs Cosmic veto double  tag events Double   tag events Cosmic sectors fired The cosmic veto could bias the BR measure expecially in case of muon tag. We used the double tag events to measure the effect. The two  cosmic from N 2 /N 0 and N 1 /N 0 are equal if there is no depletion of N2 events by cosmic veto. T3 filter seems to recover the cosmic vetoed events % %

10. KLOE general meeting 19-20 December 2002 Tor Vergata Conclusions and outlook Needed to restart DST production as soon as possible Cross section measure can be used as bench mark for systematics and correlation of retracking vs old reconstruction Some analysis is already in advanced stage ( see A.Ventura talk) Group effort on analysis is increasing