LCFI physics studies meeting, 7 th December 04Sonja Hillertp. 1 Charge efficiency and leakage rates  purity vs efficiency plots give only part of the picture for vertex charge reconstruction  should be complemented by charge efficiency: efficiency for reconstructing a charged vertex for a sample of b-tagged jets:  b,chg = (N chg,MPt / N MPt ) leakage rates for charged and neutral vertices: with Nab = number of vertices generated with charge a, reconstructed with charge b define 0 = 1 – N 00 /N 0X +- = 1 – (N 11 + N -1-1 ) / (N 1X + N -1X )

LCFI physics studies meeting, 7 th December 04Sonja Hillertp. 2 Charge efficiency, leakage rates for L/D approach  charge efficiency for improved detector lower than for degraded one due to wrongly reconstructed neutral vertices, which are larger in number than charged vertices  increase in leakage rates at high  b corresponds to drop seen in the purity plots

LCFI physics studies meeting, 7 th December 04Sonja Hillertp. 3 L/D performance: IP tracks removed (MC info) L/D min L/D max, T cut only cuts also fraction of vertices with added tracks fraction of vertices in which tracks are missed fraction of missed tracks that failed track selection absolute number of missed tracks that failed track sel. 66% 29% 36% 73% 88% 36%  check how close to 100% purity one can come by artificially suppressing IP tracks:  once done without, once with upper cut on L/D and cut on T  reach similar limit (97.0% without, 97.2% with these cuts), for different reasons: for L/D min = -10:

LCFI physics studies meeting, 7 th December 04Sonja Hillertp. 4 Neural net update  used same input variables as previously L/D, b/  (b) (= 3D-Dnorm), L  ~ factor 2 smaller training sample: ~6500 signal, background tracks  excluded inner vertex tracks from NN approach (all assigned)  4 architectures with 3, 4, 5 and 6 sigmoidal nodes in hidden layer  trained 20 networks per architecture, 50 epochs each  print network, if error function values in consecutive runs differ by < 2%  20 networks reached error function values < 0.01,  for these calculated purity vs efficiency for a choice of NN out cut values  at M Pt > 2 GeV, maximum purity reached was 92% compared to 95% obtained for the standard L/D approach  will look at all nets trained: correlation between purity and error fct value?  what happens to L/D, b/  (b) network when adding 3 rd random input?