Detector parameters for 3 Tesla solenoid field is defined in simjlc/param/jlc3T.com.withoutIT. Geometry of VTX is same as 2 Tesla case, but those of CDC and CAL are reduced.
Method
Using the Debug Generator, single muon track with fixed momentum is
generated.
Figure: 3 Tesla solenoid case postscript
Figure: 2 Tesla solenoid case postscript
Note
- At high momentum region, pt resolution in 3 Tesla case ( 1x10-4 pt (GeV)) is twice as worse as that of 2 Tesla(0.5x10-4 pt (GeV)) when VTX constraint is imposed. In the case of CDC alone, it is about three times worse.
- At low momentum region, pt resolution does not change. This is becasue, it is dominated by multiple-coulomb scattering.
Figure: Impact parameter resolution as a function of pt. 2 Tesla and 3 Tesla case are compared. postscript
IP resolution is reduced from about 2.8micron-m to 3.5micron-m at high momentum region, becasue momentum resolution is worse only at high momentum region.
For the study, four detector parameter sets are prepared. Radius of beam pipe of them are, 1.0cm, 1.5cm, 2.0cm, 2.5cm. Radius of vertex detector layers are also changed, keeping the distance from the beam pipe to the outer mose vertex layer is same. Results are shown in the figure below. postscript
When pt=1.0 GeV, impact parameter resolution as a function of beam-pipe
position is
| Radius of beam-pipe (cm) | IP resolution(micron-m) |
| 1.0 | 15.9 |
| 1.5 | 20.5 |
| 2.0 | 25.1 |
| 2.5 | 30.2 |
As seen from the table, for 1GeV track, IP resolution reduced
by about 5 micron-m when beam-pipe radius is reduced by 0.5 cm. For
high momentum track, p > 100 GeV, improvement of momentum resolution is
less than 1 micron-m even if the radius of beam pipe is changed from 2.5
cm to 1.0 cm.
In the study above, the distance from the beam pipe to the outer most VTX layer is fixed. Here, we change the total length between the inner most and the outer most VTX layer, while keeping the location of the beam pipe and the inner most VTX layer, and study the impact parameter resolution. Actually, we compare the resolution among three sets of VTX layer configuration:
- Set 1: r=1.9, 3.1, 4.3, 5.5 cm
- Set 2: r=1.9, 3.3, 4.7, 6.1 cm
- Set 3: r=1.9, 3.5, 5.1, 6.7 cm
The obtained IP resolution for typical value of momentum is shown
in the following table.
| Pt(GeV) | Set 1 (micron-m) | Set 2 (micron-m) | Set 3(micron-m) |
| 1.0 | 20.5478 | 20.8822 | 21.2405 |
| 10.0 | 4.4953 | 4.53216 | 4.56731 |
| 100.0 | 3.33517 | 3.40323 | 3.47774 |
As sen in the table, differences among the set is less than 1 micron and very small.