Recent progress and plans for Snowmass

1. Recent progress and plans for Snowmass • study dependence of vertex charge reconstruction on energy and polar angle • results shown are for standard detector only, for Snowmass will compare with following • geometries: • detector with innermost layer removed, beam pipe radius 25 mm, thickness 1 mm • same as previous, with additional layer at 71 mm (as suggested by John Jaros) • detector with innermost layer moved to 8.5 mm, beam pipe radius 8 mm • SiD vertex detector geometry, inserted into TESLA global detector • for each detector, L/D cut optimised at 200 GeV, used at all energies • exception: 4 layer detector; there, it has been tried to use a seed decay length dependent • cut, which was shown to have a negligible effect (~ 1 permille shift in purity) • to calculate vertex charge, use L/D approach with ‘inner vertex’ information; • plot cos q for centre of mass energy range 50 GeV to 500 GeV

2. L/D cut dependence in bins of seed decay length • decay length distribution peaks at • much shorter distances from the • IP for low than it does for high ECM •  at low ECM, performance more • affected by backround from IP • tracks and gluon splitting • left: l0 as function of L/D cut, • in four bins of seed decay length • optimal L/D cut decreases as • one moves away from the IP • dotted line: standard cut value

3. Improvement obtained from variable L/D cut ? dependence of l0 on L/D cut flat over wide range of L/D in each Ldec bin  only first two Ldec bins show difference in l0 when moving from const to variable L/D cut for standard detector, change in resulting l0, integrated over Ldec, below statistical error

4. Polar angle dependence at different CM energies • as ECM increases, jets • become narrower and • momentum is better • measured • probability of losing tracks • at the edge of the detector • decreases •  at higher energies, • performance stays excellent • out to large values of cos q

5. Detector comparison • first results from detector comparison (standard, 4layer): • differences are mainly seen at low centre of mass energies (50 GeV to 200 GeV) • jets from the corresponding jet energy range are common in multijet events at the ILC • for detector comparison, average l0 values over cos q range 0 to 0.9 • at low energies, find ratio of averaged leakage rates l0 (4layer) / l0 (standard) ~ 1.3 • ratio between luminosities required to obtain equivalent results would be larger, • e.g. in events, for which vertex charge of two jets is measured, signal / background ratio • could improve by (1.3)2 ~ 1.7