alignment study 19/may/2010 (s. haino). summary on alignment review inner layers are expected to be...
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Alignment study
19/May/2010(S. Haino)
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Summary on Alignment review
• Inner layers are expected to be kept “almost” aligned when AMS arrives at ISS
• Small shifts (30~50 μm) in z-direction will be possible due to (1) Change of gravity (2) Shrink of foam support
• Momentum (or Energy) reference is needed for the absolute rigidity calibration
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Alignment methods for AMS-PM
• Monitoring Layer 1N/9 movement8-layer acceptance (8 Layers+ Layer 1N or 9)103~104 protons (E > 10 GV)
• Incoherent alignment (ladder base alignment)Maximum acceptance (~ 0.5 m2sr)> 106 protons (E > 10 GV)
• Coherent alignment (momentum calibration)9-layer +Ecal acceptance (< 0.05 m2sr)~103 e+ and ~104 e- (E > ~100 GeV)
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Alignment monitoring
Layer 1NLayer 9
dY dZ
dθxy
MC data generated withGbatch/PGTRACK Alignment accuracy estimated from Gaussian fitting error on the residual of layer 1N/9 hit Proton flux weight above 10 GV
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Coherent alignment• Check of absolute alignment for
outer layersby comparing Rigidity measured by Tracker (RTracker)and Energy measured by Ecal (EEcal)on high energy e+ and e- sample
• Radiation energy loss makes PTracker=|RTracker| smaller w.r.t. EEcal
• Alignment shift makes RTracker shifted to the opposite direction for e+ and e-
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Coherent alignment - simulation
• AMS-B Gbatch/PGTRACK simulation(For details please see presentation by P. Zuccon)
• 108 e- and e+ each are injected in uniform Log10E distribution (10 < E < 500 GeV)isotropically from a plane 2.4m × 2.4m at Z = 1.8m Only trajectories which pass all the Tracker 9 layersare simulated
• Physics switches : LOSS= 1, DRAY= 1, HADR= 0, MULS= 1,BREM= 1, PAIR= 1
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Ecal energy correction• Absolute energy scale • Linearity due to the shower leak
Before
After
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EEcal/PTracker VS Egen
In case Layer 1N is shifted by ΔY = ±20 μm
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Coherent alignment - simulation
• Compare EEcal/PTracker distribution between RTracker > 0 and RTracker < 0for e+ and e- sample with EEcal > 80 GeV
• Flux weight applied assuminge- flux tuned by Fermi/LAT datae+ flux tuned and extrapolated by Pamela dataSimulated acceptance (full Ecal) :0.025 m2srLive data taking time :
100 days• Kolmogorov probability (P) is calculated
for the compatibility of two scaled histograms with RTracker > 0 and RTracker < 0
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EEcal/PTracker comparison
P: Kolmogoro
v probability
In case Layer 1N is shifted by ΔY = ±20 μm : T = 100 days
P: Kolmogoro
v probability
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-Log P VS ΔYIn case Layer 1N is shifted by ΔY : T = 100 days
Estimated error
~5 μm
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Alignment methods for AMS-PM
• Monitoring Layer 1N/9 movement2~3 μm accuracy (dY) for 10 min. live time
• Incoherent alignment (ladder alignment)> 106 protons (E > 10 GV) for 1~2 daysStudy in progress
• Coherent alignment (momentum calibration)~5 μm accuracy for 100 days live time
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Backup slides
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Alignment difference
Between Pre-int. (2008) and Flight-int. (2009)
• Ext. planes seem rotating w.r.t. Int. planes by order of 100 μm/60 cm ~ 10-2 degrees
• A small (~50 μm) Z-shift found in Ext. planes
• No significant shift found for internal layers
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Alignment differencebetween Pre-int.(2008) and Flight-int.(2009)
Ladder Rotaion (dY/dX)
Ladder Shift (dX)
Ladder Shift (dY)
Ladder Shift (dZ)
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Alignment with test beam• B-off runs with 400 GeV/c proton
beam (4B70D0BF-4b710CBF, 58 points available) are reconstructed with straight tracks
• The following three parameters are tuned w.r.t. the CR alignment (2009)(1) Layer shift along z-axis : ~20 μm(2) Ladder shift along x-axis : 5~10 μm(3) Ladder shift along y-axis : 5~10 μm
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Test beam alignmentLadder Shift (dX) RMS ~5 μm
Layer Shift (dZ) RMS ~15 μm
Ladder Shift (dY) RMS ~5 μm
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Mean of (400GV)/Rigidity
before alignment
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Mean of (400GV)/Rigidity
After alignment
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Alignment study with B-off/on
• The 5 alignment applied to proton TB runs
1. Linear fitting on B-OFF runs
2. Curved fitting (1/R = 0 fixed) on B-OFF runs
3. Curved fitting (1/R free par.) on B-OFF runs
4. Curved fitting (R = 400 GV fixed) on B-ON runs
5. Curved fitting (1/R free par.) on B-ON runs
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Alignment study with B-off/on
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Alignment study with AMS-01
dZ = 31±44 μm
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Alignment monitoring - simulation
• AMS-B Gbatch/PGTRACK simulation(For details please see presentation by P. Zuccon)
• 108 protons injected in uniform Log10R distribution (1 GV < R < 10 TV)isotropically from a plane 2.4m × 2.4m at Z = 1.8m
• Physics switches : LOSS= 1, DRAY= 1, HADR= 0, MULS= 1
• Alignment accuracy estimated from Gaussian fitting error on the residual of layer 1N/9 hit weighted by proton flux above 10 GV
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GeometryLayer8 Layer 1N
Layer1
Layer 2,3
Layer 4,5
Layer 6,7
Layer 9
Ecal 65 × 65 cm2
Layer 9
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External layes are kept as they are
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Elena Vannuccini
In-flight alignment: STEP 1
Step 1 Correction for random displacements of the sensors (incoherent alignment)
– Done with relativistic protons – Input trajectory evaluated from (misaligned) spectrometer fit
measured step 1
Flight dataSimulation
X side Y side
protons 7-100 GV (6x6y, all plane included in the fit)
After incoherent alignment:• residuals are centered• width consistent with nominal resolution + alignment uncertainty (~1mm)
Elena Vannuccini
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Elena Vannuccini
In-flight alignment: STEP 2
step 2step 1
After Step1: (possible) uncorrected global distortions might mimic a residual deflection
® spectrometer systematic effect
Step 2 Correction for global distortions of the system (coherent alignment)
– Done with electrons and positrons– Energy determined with the calorimeter
DE/E < 10% above 5GeV
Energy-rigidity match
HOWEVER, the energy measured by the calorimeter can not be used directly as input of the alignment procedure, for two reasons:
1. Calorimeter calibration systematic uncertainty
2. Electron/positron Bremstrahlung above the spectrometer
deflection offset
1
SpeSpeCalCal ΔηηPEP
CalSpe PP
calorimetercalibration uncertanty
ε1EP CalCal
Δη
Elena Vannuccini
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Elena Vannuccini
Bremsstrahlung effect
From Bethe-Heitler modelThe probability distribution of z– depends on the amount of traversed material– does not depend on the initial momentum
it should be the same for electrons and positrons!!
With real data:
– Spectrometer systematic gives a charge-sign dependent effect
– Calorimeter systematic has the same effect for both electrons and positrons
0
Spe
P
Pz
*P0
PSpe
PCal~P0
t~0.1X0
g e±
e±
€
z ~ 1
PCal
ηSpe
⏐ → ⏐ 1
PCal
1+ε ⎛ ⎝ ⎜ ⎞
⎠ ⎟ η
Spe±Δη
⎛
⎝
⎜ ⎜
⎞
⎠
⎟ ⎟