CBM beam pipe current status Andrey Chernogorov Sergey

CBM beam pipe current status Andrey Chernogorov, Sergey Belogurov, ITEP, Moscow Outline • The main idea. “Pipe” = “Window”+”Tube”. Balance between measurable particles (window) and ions (tube) • Studied configurations • Results for Ur. QMD central events at 25 AGe. V • Results for Ur. QMD central events at 8 AGe. V • Stereo angle effects on STS performance • Effects of the junction between STS and RICH sections • Conclusions FRRC session. 12 December 2010, Obnisk A. Chernogorov, S. Belogurov, ITEP, Moscow FRRC session. Obnisk, 12. 2010

Studied configurations Some of “Ideal ” configurations. Effects: cylinder-cone; Be-Al. Al: window – scaling from VELO, cone – “simple” manufacturing. “Realistic” configurations. Effects of bellows, width of “Tube”. 1. 6º configuration fits to ladders of S. Igolkin without cutting the central rib. Any configuration has a weld 1 x 10 mm A. Chernogorov, S. Belogurov, ITEP, Moscow FRRC session. Obnisk, 12. 2010 2

Results for Ur. QMD central events at 25 AGe. V Range distribution window welding Figure of merit: integrated range in the pipe: IR=Σli·qi 2· ne li – range of a particle inside the pipe qi - its charge ne – relative electron density Total ionization losses and number of delectrons are roughly proportional to IR Cylinder is optimal with MF, cone – without MF (The same for 8 AGe. V). No contradiction with the conclusions of HERAb and LHCb. A. Chernogorov, S. Belogurov, ITEP, Moscow FRRC session. Obnisk, 12. 2010 3

Results for Ur. QMD central events at 25 AGe. V Clear trends for “ideal” configurations, for “real” ones no big difference! A. Chernogorov, S. Belogurov, ITEP, Moscow FRRC session. Obnisk, 12. 2010 4

Results for Ur. QMD central events at 25 AGe. V Comparison of Al and Be cones 30%/7% No pipe /c No pipe 30 -50% /c A. Chernogorov, S. Belogurov, ITEP, Moscow FRRC session. Obnisk, 12. 2010 5

Results for Ur. QMD central events at 25 AGe. V Clear trends for “ideal” configurations, for “real” ones more narrow seems slightly better. Vertex resolution much worse than expected from multiple scattering and not indicative. Effects of wrong hits pickup in track-finder Thanks to I. Vassiliev for the basic analysis routine A. Chernogorov, S. Belogurov, ITEP, Moscow FRRC session. Obnisk, 12. 2010 6

1 Results for Ur. QMD central events at 8 AGe. V Much softer conditions for tracker at SIS-100! STS layout should not be the same as for SIS-300 A. Chernogorov, S. Belogurov, ITEP, Moscow FRRC session. Obnisk, 12. 2010 7

Results for Ur. QMD central events at 8 AGe. V STS with given layout works perfectly with any beampipe. As any optimistic conclusion should be double checked. Probably for SIS-100, STS layout may be simplified and made cheaper. However, taking into account realistic STS simulation may change the answer! A. Chernogorov, S. Belogurov, ITEP, Moscow FRRC session. Obnisk, 12. 2010 8

Results for Ur. QMD central events at 8 AGe. V Only S/B and mass resolution are somewhat sensitive to Al beampipe A. Chernogorov, S. Belogurov, ITEP, Moscow FRRC session. Obnisk, 12. 2010 9

Stereo angle effects on STS performance Big number of fakes is a big problem for track finding, especially for extending the algorithm to the segments with missed points. We looked at sensors with smaller stereo angles…. SIS-300 A. Chernogorov, S. Belogurov, ITEP, Moscow FRRC session. Obnisk, 12. 2010 10

Stereo angle effects on STS performance SIS-100 For both SIS 100 and SIS 300, stereo angle of 6 ° is the best for track finding. However improvement is paid by S/B ratio in K/L reconstruction. Momentum resolution becomes worse bellow 6° A. Chernogorov, S. Belogurov, ITEP, Moscow FRRC session. Obnisk, 12. 2010 11

Flange/window effects on RICH Default cbmroot geometry: 1 -st section of pipe with Be window h 0. 1 mm on the end with flange 2. 0 x 2. 5 cm on the end with a weld 2. 5 x 0. 2 cm on the end A. Chernogorov, S. Belogurov, ITEP, Moscow FRRC session. Obnisk, 12. 2010 13

Flange/window effects on RICH The influence of the flange is almost imperceptible. There is a slight decrease of parameters when using Be window, while passing 20 or more ions. In general, when the number of ions no more than 30, the configuration of the window can be used. A. Chernogorov, S. Belogurov, ITEP, Moscow FRRC session. Obnisk, 12. 2010 14

Conclusions - - - Influence of shape and material of the beampipe on the STS performance is studied. Pipe is considered as a composition of “window” and “tube” For 25 AGe. V central events the effects of beampipe are the most prominent in reconstruction efficiency for secondary tracks, ghost probability, CPU time, reconstruction efficiency for secondary particles, Signal to Background, Mass resolution For 8 AGe. V only S/B and mass resolution are somewhat sensitive to Al beampipe. It should be checked with more realistic STS In the presence of MF the best “tube” is narrow cylinder (no ions are taken into account) Both Be and Al options are feasible. Be provides higher buckling SF and thinner window. Decrease of the stereo angle may help to reduce number of fakes and improve track finding performance, however care should be taken of the S/B ratio in particle reconstruction The influence of the flange is almost imperceptible. When the number of ions no more than 30, the configuration of the window can be used. A. Chernogorov, S. Belogurov, ITEP, Moscow FRRC session. Obnisk, 12. 2010 15