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Beam pipe influence on the STS performance

Beam pipe influence on the STS performance. 14th CBM Collaboration Meeting, October 6.-9. 2009, Split, Croatia. A.Chernogorov, S.Belogurov, ITEP, Moscow. This part I will speak about. Outline: Introduction Simulation conditions Layout of the stations Pipe configurations

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Beam pipe influence on the STS performance

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  1. Beam pipe influence on the STS performance 14th CBM Collaboration Meeting, October 6.-9. 2009, Split, Croatia A.Chernogorov, S.Belogurov, ITEP, Moscow

  2. This part I will speak about Outline: • Introduction • Simulation conditions • Layout of the stations • Pipe configurations • Detailed results for one configuration • Comparative analysis for all configurations • Conclusions Leading effect: additional hits produced by delta electrons 14th CBM Collaboration Meeting , Split, Croatia October 6-9 2009

  3. Simulation conditions • 100 Central UrQMD Events (Au+Au@25AGeV/c) (UrQMD1.3 input file14: http://www-linux.gsi.de/~cbmsim/cbm_vmc_doc/input.htm) • Specially prepared geometry of STS stations (2.5° hole). Previous standard geometry had rectangular holes with constant height and was not suitable for our study. • Several geometries for Al and Be beam pipe • Track simulation with Geant3 (generation threshold 30 keV, Energy loss threshold 70 keV) /u/sbelogur/cbm/run/sts_sim_my.C based on standard sts_sim.C (July09 Cbmroot version) • Track reconstruction using L1Performance class /u/sbelogur/cbm/run/sts_reco_my.C based on recUrQMD_only.C by I.Vassiliev • Selection condition of tracks passing near the pipe: not less than one point of a track should belong to the cone with 5° vertex angle (MCTracks&RECOTracks) • Two level observables – excess hits due to pipe, quality of tracks reconstruction Selection condition of tracks near the pipe for analysis in order to separate effects of tracking algorithm 14th CBM Collaboration Meeting , Split, Croatia October 6-9 2009

  4. Layout of stations Special geometry was created for us by Anna with square holes of 2.5° aperture. Set of sensors 2, 4, 6, 12, 18 cm. For central ones sizes were introduced manually to follow the 2.5° requirement. 14th CBM Collaboration Meeting , Split, Croatia October 6-9 2009

  5. Layout of stations We have found that with previous geometry hit probability per strip >10% i.e. too many fakes. We introduced a new geometry with sensors of 1.4, 2, 4, 6, 12 cm and all central sensors 2 times shorter than before. 14th CBM Collaboration Meeting , Split, Croatia October 6-9 2009

  6. Pipe configurations For mechanical stability should be: h~D/E, where h is the thickness of the pipe;D is diameter of the pipe;E is the Young's modulus;E(Be)=300GPa, E(Al)=70GPa 14th CBM Collaboration Meeting , Split, Croatia October 6-9 2009

  7. Detailed results for Be tube Ø28mm h0.5mm configuration Hit density for 1, 4, 8 STS stations 14th CBM Collaboration Meeting , Split, Croatia October 6-9 2009

  8. Detailed results for Be tube Ø28mm h0.5mm configuration 14th CBM Collaboration Meeting , Split, Croatia October 6-9 2009

  9. Comparative analysis for all configurations 14th CBM Collaboration Meeting , Split, Croatia October 6-9 2009

  10. Conclusion • Effects of pipe are visible for all configurations, especially for reconstruction of secondary tracks and for ghosts • Lowest effects are observed for cylindrical tube Ø20mm, largest ones for pipe having 2.5° cone’s shape • Usage of the Be allows to reduce considerably pipe’s effects in comparison with Al 14th CBM Collaboration Meeting , Split, Croatia October 6-9 2009

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