Paolo Massarotti Charged Kaon Meeting 4 may 2006 Charged kaon lifetime P. Massarotti

Paolo Massarotti Charged Kaon Meeting 4 may 2006 Outlook Length measurement: Resolution effects evaluation Fit error Angular checks Efficiency checks Time measurement: efficiency evaluation MC fit

Paolo Massarotti Charged Kaon Meeting 4 may 2006  = (12.367±0.044 stat ±0.065 syst ) ns KLOE preliminary Analysis status: length Weighted mean between    and  

Paolo Massarotti Charged Kaon Meeting 4 may 2006 Point of Closest Approach The resolution functions given by the P.C.A. method are an underestimate of the correct resolution functions but these ones reproduct the corrept asimmetry. So we use as resolution functions The Gaussian given by the MonteCarlo true with the centres given by the P.C.A. method. With these resolution functions we can reproduce the different MonteCarlo lifetimes and we also obtain a smaller systematic given by the fit stability as a function of the range used: ± 32 ps

Paolo Massarotti Charged Kaon Meeting 4 may 2006  + 14 = ( ± 0.084) ns  2 =1.64 P  2 =6.7%  + 12 = ( ± 0.075) ns  2 =1.35 P  2 =18.1%  + 11 = ( ± 0.058) ns  2 =1.17 P  2 =28.9%  + 13 = ( ± 0.076) ns  2 =1.50 P  2 =10.7% Resolution checks: MC   measurements  + = ( ± 0.059) ns  2 =1.06 P  2 =39% We weight MC proper time distribution to obtain different lifetimes

Paolo Massarotti Charged Kaon Meeting 4 may 2006 To do: fit error We make the fit in the region between 15 and 35 ns. To fit the proper time distribution we construct an histogram, expected histo, between 12 and 45 ns. This is a region larger than the actual fit region in order to take into account border effects. The number of entries in each bin is given by the integral of the exponential decay function, which depends on one parameter only, the lifetime, convoluted with the efficiency curve. A smearing matrix accounts for the effects of the resolution. We also take into account a tiny correction to be applied to the efficiency given by the ratio of the MonteCarlo datalike and MonteCarlo kine efficiencies. N exp j =  C smear ij ×  i ×  i corr × N i theo i = 1 nbins

Paolo Massarotti Charged Kaon Meeting 4 may 2006 What about the bin error ? We have calculated the error is given by: MC Toy to evaluate the correct error on the bin entries is needed Is this over- or under-estimated?

Paolo Massarotti Charged Kaon Meeting 4 may 2006 Angular checks: We have to evaluate the lifetime for two different angular windows:  Vertex between 75 o and 105 o  Vertex smaller than 75 o or greater than 105 o Efficiency checks: We have to evaluate the systematics given by the efficiency cuts

Paolo Massarotti Charged Kaon Meeting 4 may 2006 Self triggering muon tag Considering only kaon decays with a    X    X  we look for the neutral vertex asking  clusters on time: (t - r/c)  = (t – r/c)     invariant mass  agreement between kaon flight time and clusters time 00 E ,t ,x  ±± E ,x ,t  K  tag tt pKpK pKpK t0t0 lKlK xKxK E ,t ,x  Time Strategy

Paolo Massarotti Charged Kaon Meeting 4 may 2006 Time: Efficency comparison MonteCarlo kine vs MonteCarlo reco  fit window definition MC reco MC kine Fit window 10 : 40 ns

Paolo Massarotti Charged Kaon Meeting 4 may 2006 Time: Data and MonteCarlo reco MC Data reco MC Data

Paolo Massarotti Charged Kaon Meeting 4 may 2006 Time: MC measure between 18 and 37 ns T(ns)  + MC = ( ± 0.072) ns  2 =1.08 P  2 = 36% We have to evaluate data

Paolo Massarotti Charged Kaon Meeting 4 may 2006 KLOE soccer tournament 2006 Charged kaons Branchini Massarotti Meola Patera Versaci Neutral kaons Bossi Gatti Moulson Passeri Spadaro Radiatives: Bini, De Santis, Nguyen, Venanzoni, Mr X