� LArIAT Calibration with � Stopping Tracks � LArTPC Calibration & Reconstruction Workshop � December 10-11, 2018 � Jen Raaf �
LArIAT TPC � Caveats: � ¤ Small! Tabletop-sized, and so does not have some of the same challenges seen in larger TPCs � 40 cm ¤ Shorter wires à lower noise levels � ¤ Shorter drift distance à less diffusion and less sensitivity to impurities � m c ¤ Non-recirculating cryogenic 47 cm 0 9 purification system � ¤ Single pass through filtration system NB: LArIAT uses BNL v4* LArASICs to remove H 2 O and O 2 before filling hosted on a cold front-end cryostat. LAr boils off, and cryostat motherboard designed at MSU gets topped up every few hours � (not shown in this image) � ¤ Because of this, LArIAT sees a much For Run-I and Run-II: � larger range of argon (im)purity • 4-mm wire pitch � than most other LArTPC experiments � • 1 shield plane (vertical) � • 1 induction plane (+30º from vert.) � • 1 collection plane (-30º from vert.) � LArIAT Calibrations with Stopping Tracks | J. Raaf � Dec. 10, 2018 � 2 �
Before stopping track calibrations … � I will not cover the following types of calibrations that we do before we try to do the ADCs-to-charge calibration: � ¤ ASIC response � Check that gains & shaping times of all channels are uniform via calibrated input pulses � ¤ ¤ Wire-to-wire variations � Use crossing beam MIPs (at ~constant drift time) to check/calibrate variations in charge ¤ collection response seen from wire to wire. � ¤ Electron lifetime correction � LArIAT does not recirculate & repurify its argon. If we put dirty argon into the cryostat, we ¤ just have to correct for it … � LArIAT Run-I Preliminary � LArIAT Run-II Preliminary � Filter regeneration � HV Drift Studies � Filter regeneration � LArIAT Calibrations with Stopping Tracks | J. Raaf � Dec. 10, 2018 � 3 �
Stopping tracks � LArIAT has two sources of stopping tracks � ¤ Beam particles � ¤ Use beamline instrumentation to ID particle types entering the TPC, and to measure their momenta � ¤ Measure hit amplitude (in ADC counts), for clean samples of particles identified by beamline instrumentation � Conversion from ADCs to charge via an electronic calibration factor ¤ (determined at ASIC design stage & measured on test bench). Not discussed here. � Convert charge to energy, assuming Modified Box recombination model ¤ with parameters from ArgoNeuT best fit � Tune calorimetry constant to make dE/dx vs. momentum agree with Bethe- ¤ Bloch expectation � ¤ This method is susceptible to biases in beamline momentum measurement, but we use 100 MeV/c bins (much larger than uncertainty in momentum measurement) � ¤ Cosmic muons � ¤ Collect sample via light-based trigger (muon + delayed decay electron signal) � ¤ Reconstruct TPC track energy loss vs. residual range � ¤ Tune to achieve agreement with expectation � LArIAT Calibrations with Stopping Tracks | J. Raaf � Dec. 10, 2018 � 4 �
Beamline particle type selection � LArIAT has two sources of stopping tracks � Multi-Wire Proportional LArIAT Chambers (MWPCs) � TPC & cryostat � TPC � Dipole � Magnets � Beamline spectrometer (MWPCs + bending magnets) � Upstream ¤ Measure momentum by MWPCs Downstream MWPCs determining how much a particle track bends in the magnets � LArIAT Calibrations with Stopping Tracks | J. Raaf � Dec. 10, 2018 � 5 �
Beamline particle type selection � LArIAT has two sources of stopping tracks � Multi-Wire Proportional LArIAT Chambers (MWPCs) � TPC & cryostat � TPC � Dipole � Magnets � ¤ a � TOF � LArIAT Data � Preliminary � 2 ⎛ ⎞ m = p c ⋅ TOF − 1 ⎜ ⎟ ℓ c ⎝ ⎠ LArIAT Calibrations with Stopping Tracks | J. Raaf � Dec. 10, 2018 � 6 �
Energy loss vs. momentum � Strategy 1 � ¤ Select “light” beamline particles (pions/muons) via beamline spectrometer + TOF � ¤ For each track in the TPC that is matched to a beamline track � ¤ Measurements from the first 5 cm of this track will go into a momentum bin that is determined by the beamline spectrometer � ¤ Fill a histogram with reconstructed dE/dx for each of the spacepoints in the first 5 cm of the track � ¤ Repeat for every track in the data sample � ¤ Tune value of CalAreaConstant to make momentum bins match as best possible with Bethe-Bloch dE/dx prediction � LArIAT Calibrations with Stopping Tracks | J. Raaf � Dec. 10, 2018 � 7 �
Beamline track quality cuts � ¤ Keep only the cleanest beamline tracks � One and only one hit in each of the 4 wire chambers � ¤ ¤ Reconstructed track in TPC must match nicely with beamline track entry point � Project wire chamber track trajectory to front face of TPC � ¤ ¤ Track in TPC must be at least 10 cm long � To eliminate electrons (reconstructed as many short tracks) � ¤ To avoid including pion interaction points that could affect the dE/dx, we use only the first ¤ 12 spacepoints (~5 cm) for the calibration � Momentum at the most upstream face of TPC is adjusted by a flat correction factor to ¤ account for energy lost while traversing material between the 4 th (downstream) wire chamber and the entry point of the TPC � “Excluder” Beam window Beam window WC4 Evacuated volume DSTOF TPC � TPC � WC4 Halo veto 3.2 cm “dead” LAr LArIAT Calibrations with Stopping Tracks | J. Raaf � Dec. 10, 2018 � 8 �
Positive Polarity “Light” Particles � Procedure � LArIAT Preliminary � ¤ Start with light positive particles ( 𝜈 / 𝜌 ), tune calorimetry constants to achieve best agreement of data dE/dx vs. momentum and predicted dE/dx vs. momentum (Bethe-Bloch) � ¤ Apply same calo constants to heavier positive particles (K/p) � ¤ Apply same calo constants to negative particles ( 𝜈 / 𝜌 /K) � LArIAT Calibrations with Stopping Tracks | J. Raaf � Dec. 10, 2018 � 9 �
Tuning & verification � Fit Landau to data dE/dx distribution ¤ for each momentum bin of pion sample � Adjust collection plane calorimetry ¤ constant until fit MPV matches Bethe-Bloch expected value at that momentum � Choose calo constant that gives ¤ best agreement across full range of LArIAT Preliminary � momentum bins � Verify calibration by applying same ¤ calorimetry constants to kaon and proton samples à good agreement! � LArIAT Preliminary � LArIAT Preliminary � LArIAT Preliminary � LArIAT Calibrations with Stopping Tracks | J. Raaf � Dec. 10, 2018 � 10 �
Post-tuning � Run-I 𝜌 - Data Run-I K+ Data � Run-I K- Data LArIAT Preliminary � LArIAT Preliminary � ¤ dE/dx vs. momentum showing all particle species � ¤ Run-I pos, Run-I neg, Run-II pos, Run-II neg � ¤ All Run-I with same calo constants � LArIAT Preliminary � LArIAT Preliminary � ¤ All Run-II with same calo constants � LArIAT Calibrations with Stopping Tracks | J. Raaf � Dec. 10, 2018 � 11 �
Post-tuning � Run-I 𝜌 - Data Run-I K+ Data � Run-I K- Data LArIAT Preliminary � LArIAT Preliminary � Run-I test samples � Run-I tuning sample � ¤ dE/dx vs. momentum showing all particle species � ¤ Run-I pos, Run-I neg, Run-II pos, Run-II neg � ¤ All Run-I with same calo constants � LArIAT Preliminary � Run-II test LArIAT Preliminary � ¤ All Run-II with same calo samples � constants � Run-II tuning sample � LArIAT Calibrations with Stopping Tracks | J. Raaf � Dec. 10, 2018 � 12 �
Calibration with stopping cosmics � Strategy 2 � ¤ Michel electron sample � For ~30 seconds after each beam spill, we collected cosmic ray triggers � ¤ Trigger on light from muon and delayed coincidence of decay electron � ¤ Reconstruct tracks in TPC � ¤ GausHitFinder à TrajCluster à PMAlgTrack à Calorimetry � ¤ Select events containing a single stopping 3D track � ¤ Identify boundary between muon and electron by same technique as ¤ MicroBooNE (JINST 12 P09014 (2017)) � Tune calorimetry constant via dE/dx vs. residual range of track � ¤ LArIAT Calibrations with Stopping Tracks | J. Raaf � Dec. 10, 2018 � 13 �
Event selection � Preliminary � LArIAT Preliminary � For more details on reconstruction and uses of Michel electron sample, see W. Foreman’s talk earlier today. � ¤ Constructed muon endpoint must be close to identified start of Michel cluster � ¤ Start of Michel cluster based on hit charge and local linearity conditions; endpoint of muon track from PMAlgTrack � ¤ Require separation, projected along 3D track direction to be < 2 mm � LArIAT Calibrations with Stopping Tracks | J. Raaf � Dec. 10, 2018 � 14 �
Event selection � Preliminary � Preliminary � ¤ Require hit pitch to be less than 1.2 cm � ¤ Track inclination angle (angle relative to E field) must be > 20 deg � ¤ Vertical tracks = 90 degrees � ¤ Parallel to E field = 0 degrees � ¤ Distribution of angles matches well with ArgoNeuT sample used for parameterizing Modified Box model of recombination (see B. Baller talk) � LArIAT Calibrations with Stopping Tracks | J. Raaf � Dec. 10, 2018 � 15 �
Muon endpoint resolution � Preliminary � ¤ MC study determines how well we find the muon endpoint � ¤ On average, reconstructed muon endpoint is ~1.6 mm short of the true muon endpoint � ¤ Correct for this reconstruction bias in calibration � LArIAT Calibrations with Stopping Tracks | J. Raaf � Dec. 10, 2018 � 16 �
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