Introduction to Hall-D Software February 27, 2009 David Lawrence - JLab.
Simulation/Reconstruction for CPP Experiment David Lawrence JLab Sept. 27, 2013 9/27/131simulation...
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Transcript of Simulation/Reconstruction for CPP Experiment David Lawrence JLab Sept. 27, 2013 9/27/131simulation...
simulation status - D. Lawrence - JLab 1
Simulation/Reconstruction for CPP Experiment
David Lawrence JLabSept. 27, 2013
9/27/13
simulation status - D. Lawrence - JLab 2
The GlueX Detector in Hall-D
9/27/13
CPP Experiment will use GlueX detector in Hall-D:• Linearly polarized photon source (~9GeV for GlueX)• 2T solenoidal magnetic field (dp/p = few %)• Drift chambers• High resolution Time-of-flight detector• FCAL segmented lead-glass calorimeter
Modifications to standard GlueX setup:• Replace LH2 target with thin Sn target• Move target upstream to improve low-angle acceptance• Remove start-counter• Add muon/pion detector• Move coherent peak to 6GeV
simulation status - D. Lawrence - JLab 3
Experimental Setup
FDC
Solenoid
TOF FCALTarget
Signal reaction
Beam polarization
• All occur via the Primakoff effect (interaction with the Coulomb field of nucleus)
• All result in very forward going particles
• Low t (-t < 0.005 GeV2)
9/27/13
Muon Detector
Normalization
simulation status - D. Lawrence - JLab 4
Motivation for geometery changes in target region
With start counterWithout start counter
9/27/13
• Smaller z values = target is further upstream• GlueX LH2 target extends from z=50cm to z=80cm
simulation status - D. Lawrence - JLab 5
Start Counter is in the way
9/27/13
Location: (X, Y, Z) = (2.3, 0, 96.6)=============================================== Volume: STRC material: Scintillator density: 1.032 g/cm^3rad. length: 42.1442 cm A: 11.0618 Z: 5.56867 ancestory: STRC -> STRT -> LASS -> HALL -> SITE
Nose angle=17.5o
Trajectory=1.4o
Material=3mm/sin(18.9o) = 9.3mm or 0.022 rad. lengths
simulation status - D. Lawrence - JLab 6
GlueX Simulation Tool Chain
Generators(pythia, genr8, …)
hdgeant(hddsGeant3.F)
mcsmearhdgeant.hddm
hdgeant_smeared.hddm
generated.hddm
reconstruction
Multiple generators exist including:• bggen (pythia + low energy reactions)• genr8 (isobar t-channel configurable)• coherent bremstrahlung photons
GEANT3-based simulation engine:• detailed geometry defined• partial hit digitization
Final stage smearing:• cumulative-level smearing done• dark hits/noise hits added• future: dead-channel removal
HDDS XMLCentralDC_HDDS.xmlForwardTOF_HDDS.xml…
Simulation geometry defined in XML
9/27/13
simulation status - D. Lawrence - JLab 79/27/13
simulation status - D. Lawrence - JLab 89/27/13
Without Vertex Constraint
simulation status - D. Lawrence - JLab 9
With Vertex Constraint
9/27/13
simulation status - D. Lawrence - JLab 10
Kinematics of Experiment
9/27/13
ypp is angle between pp scattering plane and polarization vector in helicity frame
fpp is angle between pp system and incident photon polarization vector in CM frame
simulation status - D. Lawrence - JLab 11
Primakoff + ro
Primakoff only
Wpp(GeV/c2)
Linear Polarization of incident photon beam helps distinguish Primakoff from coherent ro production
9/27/13
fpp ypp
(invariant mass of p+p- system) (invariant mass of p+p- system)
simulation status - D. Lawrence - JLab 12
Extracting the Cross Section(sort of)
9/27/13
• Generated (not simulated) events representing 10 days of running with 70% polarization and r background only
• Fits done for different W bins to extract Primakoff and coherent r contributions
Black: MARK-II dataRed: Statistical errors (from fits)Curves: Theory
simulation status - D. Lawrence - JLab 13
Beam Polarization via po Primakoff
9/27/13
q
f
Use asymmetry between vertical and horizontal polarization data to extract polarization
Plots by Alexander Mushkarenkov
Exercise done with 100% polarization and no backgrounds
simulation status - D. Lawrence - JLab 14
Software Level-1 Event filter
A. Somov GlueX-doc-1043
• Event is kept if either L1a_fired or L1b_fired is true
• Roughly 50% of hadronic events should be accepted by L1 trigger
• Some tuning of FCAL cut will be needed
• Trigger implemented in TRIGGER library (DMCTrigger objects)⎯ hd_eventfilter
Nominal goal for L3 is to discard 90% of L1-accepted events
9/27/13
simulation status - D. Lawrence - JLab 15
Energy deposition in FCAL
1 GeV
2 GeV
9/27/13
p+
m+
/ m p detector FCAL
GEANT3 simulation by Lubomir Pentchev
GEANT3GEANT4
• Trigger depends strongly on FCAL response
• Particle ID depends on BOTH FCAL and /m p detector
response
• Currently have limited ability to simulate FCAL response to hadronic showers
simulation status - D. Lawrence - JLab 16
Some ideas on what is needed next …
• Implement muon detector in HDDS and test with hdgeant4– Devise code management system to maintain CPP specific geometry while keeping aligned with
geometry shared with GlueX (e.g. FDC)
• Simulations of / m p separation with refined muon/pion detector design
• Tracking in / m p detector ?
• Complete implementation of relevant reactions in GlueX ANALYSIS package– gp -> pp+p-
– gp -> ppo
• Full-scale simulation and extraction of signal reaction with all relevant backgrounds– s meson– Incoherent p+p- ?
• Simulate Polarization measurement using Primakoff asymmetry with:– 70% polarization– Realistic trigger– Backgrounds
9/27/13
simulation status - D. Lawrence - JLab 17
Backup Slides
9/27/13
simulation status - D. Lawrence - JLab 18
Backgrounds• Experiment will measure reaction:
g Pb -> Pb p+p-
• Primary background will be coherent ro production followed by r-> pp decay– Will use angular distributions to separate Primakoff from
coherent ro production (see later slides)
• Currently gathering list of other potentially relevant backgrounds including:– s meson production (angular distributions same as Primakoff)
– incoherent p+p- production– …
9/27/13
simulation status - D. Lawrence - JLab 19
Relating cross-section to ap-bp
9/27/13
Figure 5. from Pasquini et al. Phys. Rev. C 77, 065211 (2008)
Cross-section for gg -> p+p- calculated based on two values of ap-bp:
ap-bp = 13.0 x 10-4 fm3 (top, dotted line)
ap-bp = 5.7 x 10-4 fm3 (solid and dashed lines)
Cross-section varies by ~10% for factor of 2 variation in ap-bp
Need measurement of ( s gg -> p+p- ) at few percent level
gg -> p+p-
dotted: subtracted DR calculation with ap-bp = 13.0dashed: subtracted DR calculation with ap-bp = 5.7solid: unsubtracted DR calculation with ap-bp = 5.7
Invariant mass of p+p-
ap-bp = 13.0
ap-bp = 5.7
(Data points from MARK-II)
simulation status - D. Lawrence - JLab 20
Detector Rates/Acceptance
• 107 tagged photons/second on 5% radiation length Pb target
• 500 hours of running• Wpp acceptance down to ~320 MeV/c2
(working to improve acceptance to even lower Wpp)
• Estimated ~36k* Primakoff events(contrast this with the ~400 events in the acceptance of the MARK-II measurement)
9/27/13
* before detector acceptance
simulation status - D. Lawrence - JLab 21
Charged Particle Tracking
Source code is checked out and built via nightly cron job on 3 platforms
Twice a week cron jobs automatically simulate and reconstruct single track events and multi-track b1p events
Plots from 5/4/12 semi-weekly single track tests
o Tracking code development began in 2004
o Tracking is done in multiple stages:• Track Finding• Wire-based fitting (wire positions only)• Time-based fitting (drift times used)
o Fitting done using a Kalman Filter (replaced original least-squares fitter)
9/27/13
simulation status - D. Lawrence - JLab 22
Charged Particle Tracking
Plots from 5/7/12 semi-weekly b1p tests
Results of recent semi-weekly test doing full reconstruction of b1p events
Final state: p p+ p+ p- p-
gg(5 charged tracks)
Some mis-identification of p+ and proton exists
>60% reconstruction efficiency of “X” meson
9/27/13
simulation status - D. Lawrence - JLab 23
Calorimetry
FCALCode developed based on experience with Rad-f experiment in Hall-B• Full reconstruction (GlueX-doc-823)• Depth corrections (GlueX-doc-1093)• Calibration procedure established
BCALo 1st generation Code developed copied from
KLOE and adapted to GlueXo 2nd generation currently under
development by GlueX• Improved angular resolution• Better error estimation• Increased po reconstruction efficiency
(61%->73% 11/28/11 report)
FCAL reconstruction efficiencyRed: minblocks= 1
Black: minblocks= 2
BCAL reconstructed energy resolution
9/27/13
simulation status - D. Lawrence - JLab9/27/13 24
pp invariant mass
w/ vertex constraint
w/ vertex constraint
w/o vertex constraint
w/o vertex constraint