simulation of charged particles traversing the lhcb rich photon detectors

Simulation of charged particles traversing the LHCb RICH photon detectorsSimulation of charged particles traversing the LHCb RICH photon detectors Malcolm John Malcolm John

Simulation of charged particles traversing the RICH photon detectors.

Simulation of charged particles traversing the LHCb RICH photon detectorsSimulation of charged particles traversing the LHCb RICH photon detectors Malcolm JohnMalcolm John

Direction of Cherenkov Photons incident on the photocathode.


Absorption/Reflection atphotocathode modeled from

Born & Wolf derivation using:

nphotocathode = 2.7 + 1.5i , thickness = 23nm(measured from EMI bialkali photocathodes)


Number of photoelectronscreated for one saturated

track through a curved HPD window..

DiameterActive diam.

ThicknessRad. of curv.

= 127mm= 114mm= 4mm= 100mm


10GeV/c passing intothe front face of the HPD

at 15o to the normal.

Side view (zoom)


10GeV/c passing throughthe back of the HPDat 5o to the normal.

Side view (zoom)


10GeV/c passing throughthe curved HPD window

at 85o to the normal.WORST CASE !!!! - but very rare.

Isometric projection


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 sin2C factor. - However 99% of tracks are fully saturated because of the high refractive index of glass/quartz.

Parameterisation in SICb of particles traversing HPDs.


SICb Event display.2 BsDs events.

11cm diameter HPD.

Red dots are the plugged patterns parameterising the effect of traversing charged particles.

Blue dots are the normal Cherenkov photons.


Standalone study of an MaPMT with 25mm quartz lens also done.

10 GeV/c at 60o to the photocathode normal.


25mm2, 25mm thick Rad. of Curv. =25mm

10 GeV/c at 180o to the photocathode normal.

10 GeV/c at 0o to the photocathode normalcoming out of the tube.


Number of photoelectons created with a 10 GeV/c traversing a 25mm thick

quartz MaPMT lens.

length

radius

(c)

(b)

(a)

(a) Photoelectrons created.(b) Photoelectrons collected into a pixel.(c) Number of hit pixels.


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.


Performance of the PatternRecognition Algorithm.11cm diameter HPDs.

848

25

6

2

0

35

4

2

4

12

272

0

30

34

33

41

0

753

7

8

13

893

11

32

106

316

6600

38

4

107

5

107

9

9

1

9

e K p X

Prob( K,p) = 0.6 ± 0.1 %

e

K

p

X

rec.true

Prob( K,p,X) = 2.3 ± 0.2 %

Prob(K ,,e) = 3.1 ± 0.8 % 1.6 %

2.4 %

0.4 %

For 300 BsDs-((K+K-) -) +

(no trav.particleparam.)


Performance of the PatternRecognition Algorithm.

MaPMTs with lens.

858

17

13

1

0

28

0

1

3

7

283

0

16

37

43

62

0

732

1

7

11

923

4

18

79

278

6712

34

1

68

4

108

13

0

0

6

e K p X

Prob( K,p) = 0.5 ± 0.1 %

e

K

p

X

rec.true

Prob( K,p,X) = 1.5 ± 0.2 %

Prob(K ,,e) = 2.1 ± 0.5 % 1.1 %

1.6 %

0.5 %

(no trav.particleparam.)

For 300 BsDs-((K+K-) -) +


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

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