1. 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 UrQMD central events at 25 AGeV
Results for UrQMD central events at 8 AGeV
Stereo angle effects on STS performance
Effects of the junction between STS and RICH sections
Conclusions
FRRC session. 12 December 2010, Obnisk

2. Studied configurations Any configuration has a weld 1x10 mm
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 1x10 mm
A.Chernogorov, S.Belogurov, ITEP, Moscow
FRRC session. Obnisk,

3. Results for UrQMD central events at 25 AGeV
window
welding
Range distribution
Figure of merit: integrated range in the pipe: IR=Σli·qi2· ne
li – range of a particle inside the pipe
qi - its charge
ne – relative electron density
Total ionization losses and number of d-electrons are roughly proportional to IR
Cylinder is optimal with MF, cone – without MF (The same for 8 AGeV). No contradiction with the conclusions of HERAb and LHCb.
A.Chernogorov, S.Belogurov, ITEP, Moscow
FRRC session. Obnisk,

4. Results for UrQMD central events at 25 AGeV
Clear trends for “ideal” configurations, for “real” ones no big difference!
A.Chernogorov, S.Belogurov, ITEP, Moscow
FRRC session. Obnisk,

5. Results for UrQMD central events at 25 AGeV
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,

6. Results for UrQMD central events at 25 AGeV
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,

7. Results for UrQMD central events at 8 AGeV1
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,

8. Results for UrQMD central events at 8 AGeV
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,

9. Results for UrQMD central events at 8 AGeV
Only S/B and mass resolution are somewhat sensitive to Al beampipe
A.Chernogorov, S.Belogurov, ITEP, Moscow
FRRC session. Obnisk,

10. 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,

11. 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. Flange/window effects on RICH
Default cbmroot geometry: 1-st section of pipe
with Be window h0.1mm on the end
with flange 2.0x2.5cm on the end
with a weld 2.5x0.2cm on the end
A.Chernogorov, S.Belogurov, ITEP, Moscow
FRRC session. Obnisk,

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,

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 AGeV 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 AGeV 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,