Rikkyo University Murata.lab / RIKEN 　Master course 2nd

　 Kentaro Watanbe

PHENIX Colaboration meeting 2012

＠ Rikkyo UniversityOptical Alignment System for the PHENIX Muon

Tracker 　

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In order to achieve better momentum resolution We should correct for these relative movement !! The purpose of the optical alignment system(OASYS) is the real-time monitoring of the relative alignment among the stations.

the muon is flyting 15 degrees

Alignment for MuTr W physics

W signal : 500μm 〜 1.0mmMuTr Chamber resolution : 100μm

During the experiment period Each chamber moves 50 to 300 μm by the magnetic field or temperature excursion !!!

Optical Alignment System ① The OASYS consists of a light source at station 1, a convex lens at station 2, and a CCD camera at station3. When an individual station moves, the image on the CCD camera moves reflecting the station movement. By observing the position of the light spot on the image of the CCD camera, we can monitor each station’s relative movement.

We use a halogen lamp and optical fiber as a light source for the OASYS. Optical fibers guide light from the halogen lamp It is attached on the edge of station1. Seven CCD cameras have been set up to each octant as in a diagram.

station1 station3station2

OASys CCD →

Optical Alignment System ②

56 OASYS cameras by each arm. total 112 cameras

The results of measurement are peak position distributions for 1000 samples obtained within 30 minutes. The typical sharp image and the typical broad image are displayed. The measured resolution is 1.4 μm for sharp image, and 3.1 μm for the broad image.

Resolution for the CCD camera

The typical sharp image

The typical brod image

resolution is 1.4 μm resolution is 3.1 μm

capture raw data image

6.6mm

8.8mm

OASys determines the center position by Fitting. First, it makes two histograms which are projected image on the horizontal or vertical axis.….

Optical Alignment SystemN

ort

h A

rm

Sou

th A

rm

All

cam

era

X

dir

ect

ion

Normalize vertical (first day opsition) Range : -15[pixel] to 15[pixel], Horaizontal Range : 2010/1/10~2010/4/20

All

cam

era

X

dir

ect

ion

12 camerabroken

3 camerabroken

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Movement of optics

X direction

Y directionRun9 first of March to end of June

4 month

one day

Daily fluctuation

10μm

Fourier transform

No Peak Spectrum !

This fluctuation is defined error of long term.

I’m focused the movement of the long term. So, I treat daily fluctuation as random noise. it means the error bar of OASys become about 10μm

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Linear Fit the Movement of optics

90μm

７ 0μm

X direction

Y direction

I think this long term movement as the rotation or translational motion or Monotonic expansion of the chamber by the fixture degradation, land subsidence.

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Linear fit all camera: North Arm X direction 2009 3/1 〜 6/30 (120day)

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Linear fit : North Arm Y direction 20093/1 〜 6/30 (120day)

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Linear fit : South Arm X direction 20093/1 〜 6/30 (120day)

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Linear fit : South Arm Y direction 20093/1 〜 6/30 (120day)

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OASys Vector Map in Run9

It is real chamber movement ??

North Arm South Arm

What do you think this movement ??

collision

external point

stub point st3

sagitta

stub point st2stub point st1

sagitta = stub point st3

stub point st3

external point

external point

ー※The external division is defined from 2 stub information (st1&st2).

How to define the sagitta

Zero Field Run Saggita AnalysisWe must confirm that OASys parameter can be tracing real chamber movement by another independent tool. It is “zero field run saggita analysis !!” Because, in the zero magnetic field, almost track became straight. It means the sagitta will disturibute around 0.0

Sagitta distribution & miss Alignment

2009 PHYSICS RUN

zero field cosmic 1st zero field 2nd zero field

pp500GeV pp200GeV

March MayJanuary

chamber moving ??

mean March

mean May

Miss Alignment = mean_March – mean_May > chamber resolution

Muon momentum study pp500GeV

momentum [GeV]

run condition

under 10GeV 97.3% of ALL !!

This spectrum is pp500GeV track associated muon momentum distribution (No track cut ).

500GeV (3104228/3187765) 97.3%

momentum [GeV]

High pt spectrum seems to decrease than pp500GeV. However under 10GeV muon is 98.3%, high pt muon is not sensitive for the residual distribution.

Muon momentum study pp200GeV

run condition

under 10GeV 98.3% of ALL !!

200GeV (961325/945105) 98.3%

Muon momentum study summary

pp200GeVpp500GeV

momentum [GeV]

The residual distribution is based on under 10 GeV muon. The spectrum is same in pp200GeV and pp500GeV. It means the residual from different beam can be compered. And the different of beam is not sensitive 2nd gaussian.

pp200GeVpp500GeV

1/momentum [/GeV]

Normalized ( 〜10GeV)

1/p

Norm

alize

d lo

g

scale

1GeV

0.2GeV

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sample: south octant8 half2

simulation study From zero field cosmic study, we make sure second gaussian component is not based on hadron decay. So, we guess that component will be based on the effect of multiple scattering another momentum. After the last meeting, Oide-san gave me simple multiple scattering root macro. I modified that macro to near real condition.

Fist Step : Air volume contribution (fix muon momentum)

At first I assumed if 2.0 GeV muon go through between St1 to St3. Then muon is affected by the effect of multiple scattering from air volume. I want to know the final position (St3) is how much spread by that effect.

2GeV muon

st1

st3

calculation by handThe multiple scattering is roughly Gaussian for small deflection angles, the projected angular distribution, with a width given by

The projected y direction distribution is given by

@ South station2 〜 station3

moun momentum : 2GeVx : 160cmair radiation length : 37g ・cm^-2air density :

→σ = 469μm

the result of simulation

2GeV muon

The cause of fixed momentum 2Gev, it can be fit with single gaussian. This simulation consistent with hand calculation.

different momentum distribution

1GeV fixedRMS: 939μm

2GeV fixedRMS: 470μm

5GeV fixedRMS: 188μm

10GeV fixedRMS: 94μm

different momentum contribution

The second gaussian component is appeared !!!

Generate muon distribution pp500GeV

Fit 2gaussian

simulation datamomentum 1 〜10GeV

RChiS= 1.1019

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South Arm Run9 March Zero field

oct 1 half 1

oct 1 half 2

oct 2 half 1

oct 2 half 2

oct 3 half 1

oct 3 half 2

North Arm Run9 March Zero field

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A few octant have asymmetry distribution. It is not first priority to find out this asymmetry source. However, I was able to find out that source by simple correlation study. So, today I would like to talk about this study.

1

2

3

4

5

6

7

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Run9 South March mean position direction ?

1

2

3

4

5

6

7

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Run9 North March mean position direction ?

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0 1 2 3 4 5 6 7 8 9

-200

-150

-100

-50

0

50

100

150

200

Calculation alignment system (Millepede)

PHENIX Physics RUNzero field run 1st zero field run 2nd zero field run 3rdfew

monthsfew months

Meaning OASysIt is important to align relative positions among the three stations, because it affects the momentum measurement. We align position among the three stations using field off run at the beginning of the experiment. However, each station moved 100-300 μm during the experiment period. In order to monitor this real-time movement, an optical alignment system(OASYS) has been installed into muon tracking chamber.

Optical Alignment System (OASys)The zero field run data taking is less frequent.

However, OASys data taking can be 365days. It is meaningful OASYS.

OASys data taking

Making use of this advantage, OASys send the signal to taking zero field run for Millepede Alignment.

Re-Alignment

Re-Alignment

warning!! warning!!

The change of Second gaussian component上記の通り、２つのガウシアンと pol0 でフィッティングを行うと３月のデータと５月のデータで第２ガウシアンの ratio が変化しているように見受けられる。特に５月のデータでは、その量が総じて減っている。この理由を考察する事で今までハドロンの decay として扱っていた２つ目の component に対して正確に ID する事が今回の study の目的である。

Run9 March South Oct8 half1Rchis : 1.82

Run9 MaySouth Oct8 half1Rchis : 3.07

単純に Fit が上手く決まらないのが原因で第２ガウシアンの要素が死んだと考えるもののsample 。

Run9 MarchNorh Oct3 half1Rchis : 1.24

Run9 MayNorh Oct3 half1Rchis : 170

Fit は上手くいっていて本当に第２ガウシアンのスペクトルの形が変化したのかもしれない。と思うもの。

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