TPC track distortions Review of situation Alain Blondel, Silvia Borghi , Simone Giani, Simone Gilardoni and all the people that contributed with ideas or suggestions or comments during the analysis meetings and offline Thanks to Charles Pattison for the ntuple productions
TPC track distortions Review of situation. Alain Blondel, Silvia Borghi , Simone Giani, Simone Gilardoni and all the people that contributed with ideas or suggestions or comments during the analysis meetings and offline Thanks to Charles Pattison for the ntuple productions. Outlook. - PowerPoint PPT Presentation
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
TPC track distortionsReview of situationAlain Blondel, Silvia Borghi,
Simone Giani, Simone Gilardoni and all the people that contributed with ideas or suggestions or comments during the analysis meetings
and offline
Thanks to Charles Pattison for the ntuple productions
7 July 2003 Silvia Borghi 2
Two distortions effect
1. Electromagnetic effect induces a d0 shift dependent on z position (smaller effect, 10 mm)
2. Blondel’s effect (larger effect 30-40 mm)
Outlook
7 July 2003 Silvia Borghi 3
OX
Definition of d0
- d0
impact parameter
x
yTrack
Sxy=0
clockwise
Fit circlecenter
How d0 changes in case of distortions
7 July 2003 Silvia Borghi 4
First Effect
Presented at analysis meetingon 29th April 2003
and studied in Dydak’s et al. HARP Memo 03-002, 30 June
2003
7 July 2003 Silvia Borghi 5
EC
500 mm 285 mm 215 mm 500 mm
B2
We consider the following regions.•the forward part (region A and E)•the backward part (region C and B2)We observe a different effect in these two regions.
C: -51°<<0B2: 0<>35°
E: 68°<<77°A: 0<<77° from end-cap
A
29th April 2003
7 July 2003 Silvia Borghi 6
MiniBoone at 8.9 GeV/c C B2E
29th April 2003
7 July 2003 Silvia Borghi 7
HARP Memo 03-0016 June 2003
Therefore, during all of HARP data taking after 8 August 2001, the high voltage of the inner field cage was lowered by 1.6% than the corresponding high voltage of the outer field cage.
[3] We thank L. Linssen for having brought the high voltage misalignment problem to our attention, and for ongoing calibration work to ascertain the precise size of misalignment
No feedback from collaboration until
¨
¨
7 July 2003 Silvia Borghi 8
The effects of the magnetic and electric field inhomogeneities have the same overall effect on the distortion of track sagittas.
Another distinct feature is the strong dependence of the displacements on the longitudinal position inside the active TPC volume, especially around the nominal target position. This suggests that the position and the length of the target plays an important rôle. The higher upstream the track, the less it will be affected. Therefore, tracks from thin targets will generally be less affected than tracks emerging at the downstream end of long targets. This may shed some light on observations on TPC track distortions reported recently [7].
¨
¨F. Dydak, A. Krasnoperov, Yu. Nefedov
HARP Memo 03-00230 June 2003
The effect is most prominent at small radius, where near the target position displacements of order 10 mm are expected.
Positive tracks are systematically shifted to smaller momentum, negative tracks to higher momentum.
¨¨
¨¨(As already shown in my previous first plot)
7 July 2003 Silvia Borghi 9
BUT …
As you can see in the next plots the shift for positive particles is constant in the direction of negative d0, but for negative particles the shift is not always in the same direction of positive d0 and sometime the shift is equal to one of positive particles
7 July 2003 Silvia Borghi 10
Be thick (1 ) at 12 GeV/c CE
7 July 2003 Silvia Borghi 11
Be thin (2% ) at 8 GeV/cCE
7 July 2003 Silvia Borghi 12
Be thin (5% ) at 15 GeV/c
with inverted BCE
7 July 2003 Silvia Borghi 13
In the forward region (region A or E) the d0 peak for positive particles is shifted to -10 mm and sometime the d0 peak for negative particles is shifted to 10 mm.
If we consider the first part of TPC (region C and B2) this effect disappears and the d0 distribution is centered in 0.
The shift for positive particles is the same also for inverted magnetic field.
Conclusions (on 29th April 2003) …
7 July 2003 Silvia Borghi 14
Our state of the art knowledge:The Memo 03-002 could confirm the shift for positive particles, but it could not explain, yet, why sometimes the peak of negative particle is not shifted on the positive d0.
The last plot shows that a more dominant effect of distortion exists.
On the same subject: CONCLUSIONS Memo 03-002
The problem of TPC track distortions due to magnetic and static electric field inhomo geneities has been adressed in a quantitative way. …The high voltage misalignment between the outer and inner field cages is identified as the likely primary cause of sagitta distortions of TPC tracks. The position and the length of the target plays an important rôle. ¨
¨
7 July 2003 Silvia Borghi 15
Blondel’s Effect
Already presented in analysis meetings in April
2003
7 July 2003 Silvia Borghi 16
Where did we start?
Negative bluePositive red
Ta thick at 3 GeV/c
7 July 2003 Silvia Borghi 17
Ta thick at 3 GeV/c From C. Morone’s Thesis
7 July 2003 Silvia Borghi 18
XO
-
B
B
D
D
C
C
A
AE
E
Ta thick at 3 GeV/c
1/
7 July 2003 Silvia Borghi 19
1/(charge * Pt) (1/MeV/c)
+ -
-+
+ +- -
Ta thick at 3 GeV/c
7 July 2003 Silvia Borghi 20
+ -
-+
+ +- -
Miniboone at 8.9 GeV/c
7 July 2003 Silvia Borghi 21
One possible explanation
Distortions due to ExB effects are the cause of this effect.
This effect may not be constant in time and in space.
The banana effect does not depend in conclusive manner on
• the target (al and k2k 1 lambda)
• the interaction length of target (k2k 1 lambda and k2k replica)
• beam momentum (Be thin at 8 GeV/c and 12 GeV/c)
• the data 2001 or 2002 (C and Al).
Summary of table
7 July 2003 Silvia Borghi 24
What happens if B is inverted?
Be 5% at 15 GeV/c B neg
C 2%at 3 GeV/c B pos
7 July 2003 Silvia Borghi 25
If the beam is positive the banana has the same position also when B is inverted.
Compatible with ExB effect.
Not yet explained:
Why is the d0 peak at 0 always present?(demonstrates that this ExB effect is not constant )Why not in coincidence with understood spill time structure or run time structure?
What happens if B is inverted?
7 July 2003 Silvia Borghi 26
Another possible explanation(additional or alternative)
Beam effects:• Rate• Size• Optics.
7 July 2003 Silvia Borghi 27
First run: 9377-9381
C 2%at 3 GeV/c B posno beam interruption between runs with banana and runs
without banana
Does the banana depend on the beam?
7 July 2003 Silvia Borghi 28
After ~7 runs:On 15th October 2001 at 12.39:• vertical collimator settings: 53.8 • events per burst 60
On 15th October 2001 at 17.56:Beam expert has finished tuning the beam.
On 15th October 2001 at 18.13:• the vertical collimators to +- 52.0. • events per burst is ~80
7 July 2003 Silvia Borghi 29
First run: 9377-9381 First run: 9389-9449
C 2%at 3 GeV/c B posno beam interruption between runs with banana and runs
without banana
Does the banana depend on the beam?
7 July 2003 Silvia Borghi 30
What happens? (preliminary)
1. In C setting (and also in a Be setting) the banana disappears when the beam spot size decreases.
2.The spot size alone does not create the banana, in fact in Be 2% lambda 15 GeV/c a smaller spot size shows the banana effect
3. We never observed the banana with negative beam.
7 July 2003 Silvia Borghi 31
In these cases the spot size and the focusing of the beam seems to play a important role.
The rate of T9 protons seems not to matter.
Preliminary conclusions
7 July 2003 Silvia Borghi 32
The banana is always present in all regions and no evident changes are noted.
The tracks belonging to the banana have no strong dependencies by • 0 • tan() • z0
Space dependence of the banana effect
7 July 2003 Silvia Borghi 33
The banana effect does not depend in conclusive manner on
• the target (al and k2k 1 lambda)• the interaction length of target (k2k 1 lambda and k2k replica)• beam momentum (Be thin at 8 GeV/c and 12 GeV/c) • the data 2001 or 2002 (C and Al).• setting (C)• magnetic field polarity (Be at 15 GeV/c) • rate of protons in T9 (C)• on spill time during the same run• the spatial regions • the track parameters: 0, tan(), z0
Conclusion
7 July 2003 Silvia Borghi 34
?Does the banana effect depend on• the beam spot size• the time: in which way• the ionization of the chamber that creates a ExB effect
If we do not use the settings affect by the banana, which amount of data we lose
If we do not understand really this effect, how can we be sure that the effect (in a smaller way) is not present in the other settings