Alignment study 19/May/2010 (S. Haino)

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

Alignment methods for AMS-PM Monitoring Layer 1N/9 movement 8-layer acceptance (8 Layers+ Layer 1N or 9) 10 3 ~10 4 protons (E > 10 GV) Incoherent alignment (ladder base alignment) Maximum acceptance (~ 0.5 m 2 sr) > 10 6 protons (E > 10 GV) Coherent alignment (momentum calibration) 9-layer +Ecal acceptance ( ~100 GeV)

Alignment monitoring Layer 1N Layer 9 dYdYdZdZ dθ xy MC data generated with Gbatch/PGTRACK Alignment accuracy estimated from Gaussian fitting error on the residual of layer 1N/9 hit Proton flux weight above 10 GV

Coherent alignment Check of absolute alignment for outer layers by comparing Rigidity measured by Tracker (R Tracker ) and Energy measured by Ecal (E Ecal ) on high energy e+ and e - sample Radiation energy loss makes P Tracker = | R Tracker | smaller w.r.t. E Ecal Alignment shift makes R Tracker shifted to the opposite direction for e+ and e -

Coherent alignment - simulation AMS-B Gbatch/PGTRACK simulation (For details please see presentation by P. Zuccon) 10 8 e - and e + each are injected in uniform Log 10 E 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 layers are simulated Physics switches : LOSS= 1, DRAY= 1, HADR= 0, MULS= 1, BREM= 1, PAIR= 1

Ecal energy correction Absolute energy scale Linearity due to the shower leak Before After

E Ecal /P Tracker VS E gen In case Layer 1N is shifted by ΔY = ±20 μm

Coherent alignment - simulation Compare E Ecal /P Tracker distribution between R Tracker > 0 and R Tracker 80 GeV Flux weight applied assuming e - flux tuned by Fermi/LAT data e + flux tuned and extrapolated by Pamela data Simulated acceptance (full Ecal) : m 2 sr Live data taking time : 100 days Kolmogorov probability ( P ) is calculated for the compatibility of two scaled histograms with R Tracker > 0 and R Tracker < 0

E Ecal /P Tracker comparison P: Kolmogorov probability In case Layer 1N is shifted by ΔY = ±20 μm : T = 100 days P: Kolmogorov probability

-Log P VS ΔY In case Layer 1N is shifted by ΔY : T = 100 days Estimated error ~5 μm

Alignment methods for AMS-PM Monitoring Layer 1N/9 movement 2~3 μm accuracy ( dY ) for 10 min. live time Incoherent alignment (ladder alignment) > 10 6 protons (E > 10 GV) for 1 ~ 2 days Study in progress Coherent alignment (momentum calibration) ~5 μm accuracy for 100 days live time

Backup slides

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 ~ degrees A small ( ~50 μm ) Z-shift found in Ext. planes No significant shift found for internal layers

Alignment difference between Pre-int.(2008) and Flight-int.(2009) Ladder Rotaion (dY/dX) Ladder Shift (dX)Ladder Shift (dY) Ladder Shift (dZ)

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

Test beam alignment Ladder Shift (dX) RMS ~5 μm Layer Shift (dZ) RMS ~15 μm Ladder Shift (dY) RMS ~5 μm

Mean of (400GV)/Rigidity before alignment

Mean of (400GV)/Rigidity After alignment

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

Alignment study with B-off/on

Alignment study with AMS-01 dZ = 31±44 μm

Alignment monitoring - simulation AMS-B Gbatch/PGTRACK simulation (For details please see presentation by P. Zuccon) 10 8 protons injected in uniform Log 10 R 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

Geometry Layer8  Layer 1N Layer1 Layer 2,3 Layer 4,5 Layer 6,7 Layer 9 Ecal 65 × 65 cm 2 Layer 9

External layes are kept as they are

 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 data Simulation X sideY side protons GV (6x6y, all plane included in the fit) After incoherent alignment: residuals are centered width consistent with nominal resolution + alignment uncertainty (~1  m)  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   E/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 calorimeter calibration uncertanty  Elena Vannuccini 

Bremsstrahlung effect From Bethe-Heitler model The 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 * P0P0 P Spe P Cal ~P 0  t~0.1X 0  e ± e±