Simulation of charged particles traversing the LHCb RICH photon detectors

1. Simulation of charged particles traversing the RICH photon detectors. q q Simulation of charged particles traversing the LHCb RICH photon detectors Malcolm John

2. Direction of Cherenkov Photons incident on the photocathode. Simulation of charged particles traversing the LHCb RICH photon detectors Malcolm John

3. Absorption/Reflection at photocathode modeled from Born & Wolf derivation using: nphotocathode = 2.7 + 1.5i , thickness = 23nm (measured from EMI bialkali photocathodes) Simulation of charged particles traversing the LHCb RICH photon detectors Malcolm John

4. Diameter Active diam. Thickness Rad. of curv. = 127mm = 114mm = 4mm = 100mm q Number of photoelectrons created for one saturated track through a curved HPD window.. q Simulation of charged particles traversing the LHCb RICH photon detectors Malcolm John

5. 10GeV/c passing into the front face of the HPD at 15o to the normal. Side view (zoom) Simulation of charged particles traversing the LHCb RICH photon detectors Malcolm John

6. 10GeV/c passing through the back of the HPD at 5o to the normal. Side view (zoom) Simulation of charged particles traversing the LHCb RICH photon detectors Malcolm John

7. 10GeV/c passing through the curved HPD window at 85o to the normal. WORST CASE !!!! - but very rare. Isometric projection Simulation of charged particles traversing the LHCb RICH photon detectors Malcolm John

8. Parameterisation in SICb of particles traversing HPDs. The photoelectron hit patterns resulting from the standalone window simulation are plugged directly into SICb.  One of 18 different patterns is chosen depending on the angle the particle makes with the curved window.  Photons falling outside the 11cm tube diameter are killed.  The number of photoelectrons included in the pattern is modified by the sin2C factor. - However 99% of tracks are fully saturated because of the high refractive index of glass/quartz. Simulation of charged particles traversing the LHCb RICH photon detectors Malcolm John

9. SICb Event display. 2 BsDs events. 11cm diameter HPD. Red dots are the plugged patterns parameterising the effect of traversing charged particles. Blue dots are the normal Cherenkov photons. Simulation of charged particles traversing the LHCb RICH photon detectors Malcolm John

10. Standalone study of an MaPMT with 25mm quartz lens also done. 10 GeV/c at 60o to the photocathode normal. Simulation of charged particles traversing the LHCb RICH photon detectors Malcolm John

11. 10 GeV/c at 180o to the photocathode normal. 10 GeV/c at 0o to the photocathode normal coming out of the tube. 25mm2, 25mm thick Rad. of Curv. =25mm Simulation of charged particles traversing the LHCb RICH photon detectors Malcolm John

12. length radius q Number of photoelectons created with a 10 GeV/c traversing a 25mm thick quartz MaPMT lens. (a) (a) Photoelectrons created. (b) Photoelectrons collected into a pixel. (c) Number of hit pixels. (b) (c) Simulation of charged particles traversing the LHCb RICH photon detectors Malcolm John

13. Effect of charged particles traversing the photon detectors on the pattern recognition performance.  The pattern recognition algorithm now includes a second iteration using the result of the first iteration as an improved estimate of the local background.  This had been written (GW) to allow the pattern recognition to cope with photon clusters from tracks going backwards in the gas radiators.  This improved algorithm has been used with the traversing particle parameterisation included to assess the new effect.  No other explicit modifications to the algorithm have been made at this time. Simulation of charged particles traversing the LHCb RICH photon detectors Malcolm John

14. Performance of the Pattern Recognition Algorithm. 11cm diameter HPDs. true e   K p X rec. e 848 5 106 7 4 30  25 107 316 8 2 34  6 9 6600 13 4 33 K 2 9 38 893 12 41 p 0 1 4 11 272 0 X 35 9 107 32 0 753 For 300 BsDs-((K+K-) -) + Prob(   K,p) = 0.6 ± 0.1 % 0.4 % Prob(   K,p,X) = 2.3 ± 0.2 % 2.4 % Prob(K  ,,e) = 3.1 ± 0.8 % 1.6 % (no trav. particle param.) Simulation of charged particles traversing the LHCb RICH photon detectors Malcolm John

15. Performance of the Pattern Recognition Algorithm. MaPMTs with lens. true e   K p X rec. e 858 4 79 1 0 16  17 108 278 7 1 37  13 13 6712 11 3 43 K 1 0 34 923 7 62 p 0 0 1 4 283 0 X 28 6 68 18 0 732 For 300 BsDs-((K+K-) -) + Prob(   K,p) = 0.5 ± 0.1 % 0.5 % Prob(   K,p,X) = 1.5 ± 0.2 % 1.6 % Prob(K  ,,e) = 2.1 ± 0.5 % 1.1 % (no trav. particle param.) Simulation of charged particles traversing the LHCb RICH photon detectors Malcolm John

16. Conclusion  A parameteristion of charged particles traversing the RICH photon detectors has been included in SICb for PAD-HPD geometry and MaPMT (with lens).  The existing pattern recognition copes well with the new effect included.  Parameterization should be reviewed later in light of testbeam results. Simulation of charged particles traversing the LHCb RICH photon detectors Malcolm John