Recent results from g4sbs
Andrew PuckettUniversity of Connecticut
SBS Collaboration MeetingJuly 22, 2016
The Super BigBite Spectrometer (SBS) in Hall A
7/22/16 SBS Collaboration Meeting 2016 2
E12-07-109: Proton form factor ratio GEp/GMp using polarization transfer
E12-09-016 and E12-09-019: Neutron magnetic form factor GMn and neutron form
factor ratio GEn/GMn
E12-09-018: Transverse target SSA in SIDIS
GEP: 45 beam-days in Hall A
GEN + GMN: 50 + 25 beam-days in Hall A
SSA in SIDIS: 64 beam-days in Hall A • SBS is a novel magnetic spectrometer based on
time-tested “detectors behind a dipole magnet” approach
• Detects forward-going, high-energy particles with medium solid angle acceptance and large momentum bite at highest achievable luminosities of CEBAF
• Physics program: nucleon EMFFs and SIDIS, 180 beam-days approved in Hall A
• Conditionally approved: Pion structure function via tagged DIS, 27 days Hall A
GEANT4 MC Requirements for SBS Experiments• Detector background rates/occupancies:
• Inform shielding design• Reduce detector background rates from sources other than target• Calculate radiation budgets• Design shielding of SBS electronics
• Inform DAQ/trigger requirements/design• Inform/test reconstruction software development
• SBS/BigBite magnetic field maps:• Characterize SBS optics/spin transport• Optimize SBS acceptance for the different experiments
• Detector performance:• Characterize position/time/energy resolution of detectors
• New proposal development:• Realistic and accurate acceptance and rate calculations (and detector
resolution)• Flexible interface to physics event generators
7/22/16 SBS Collaboration Meeting 2016 3
g4sbs: GEANT4 MC for SBS experiments• Source code available in a github repository owned and managed
by JLab: https://github.com/JeffersonLab/g4sbs• Write access to the repository is managed by Ole Hansen. • Multiple branches exist, but most recent development has taken place in
the uconn_dev branch, periodically merged into the (more stable, but out-of-date) master branch.
• External libraries required: • ROOT: version 5 only for now—ROOT 6 compatibility is in the works• GEANT4: version 10.0 or later for recent code versions (for latest
version with spin tracking, requires version 10.1 or later!)• g4sbs documentation page (developed and maintained by UConn
group): https://hallaweb.jlab.org/wiki/index.php/Documentation_of_g4sbs• Existing: how-tos for installation and execution, documentation of g4sbs-
specific commands, where to download field maps, etc.• Forthcoming: documentation of output ROOT tree structure, self-
contained, working example scripts for running the simulation, example ROOT macros for data analysis
7/22/16 SBS Collaboration Meeting 2016 4
Existing Geometries—GEP
7/22/16 SBS Collaboration Meeting 2016 5
• Detectors: • ECAL, HCAL, CDet, GEMs (front tracker and polarimeter GEMs), CH2 analyzer
• SBS magnet: • Iron yoke w/cutout, coils, front and rear field clamps, pole shims to reach higher field integral
• Target: • LH2 cell, vacuum chamber+snout
• Beamline: • Downstream beam pipe, flanges, magnetic shielding, corrector dipoles, lead shielding
An elastic ep event in g4sbs illustrating full detector response
Existing Geometries—SIDIS
7/22/16 SBS Collaboration Meeting 2016 6
A SIDIS 3He(e,e’𝛑+)X event in g4sbs
• Detectors: HCAL, RICH, SBS GEMs, BigBite (GEMs, GRINCH, Shower+Preshower) • SBS magnet: Iron yoke w/cutout, coils• 60-cm 3He gas target, glass cell• BigBite magnet• Beamline: “standard” downstream beam pipe• Missing: target chamber details, shielding and collimation, downstream beamline shielding, target
magnetic shielding, etc.
Existing Geometries—GEN+GMN
7/22/16 SBS Collaboration Meeting 2016 7
A quasi-elastic 3He(e,e’n)X event in g4sbs
• Detectors: HCAL, BigBite (GEMs, GRINCH, Shower+Preshower) • SBS magnet: Iron yoke w/cutout, coils• 60-cm 3He gas target, glass cell• BigBite magnet• Beamline: “standard” downstream beam pipe• Missing: target chamber details, shielding and collimation, downstream beamline shielding, target
magnetic shielding, etc.
Targets• Currently available target options (driven by SBS physics
program):• Gas targets:
• Hydrogen• 3He• (fictional) free neutron
• Liquid hydrogen/deuterium
• To be added:• Solid targets• Optics/dummy targets• Empty target• Polarized NH3• Others?
7/22/16 SBS Collaboration Meeting 2016 8
Magnetic Field• “Standard” BigBite field map available• SBS TOSCA maps have been calculated for most
configurations• Only GEP 12 GeV2 map has been extensively simulated
so far using g4sbs• SBS field map is not independent of SBS angle/distance
from target, because of beamline active and passive magnetic shielding elements
• Uniform SBS magnetic field in dipole gap available as an approximation when detailed TOSCA map is not available or when speed is more important than precision.• Spin tracking available using SBS TOSCA map—
soon to be added for uniform field.
7/22/16 SBS Collaboration Meeting 2016 9
“Built-in” event generators in g4sbs• Elastic ep or quasi-elastic (e,e’p), (e,e’n):
• Rosenbluth cross section weight computed using Kelly parametrization of nucleon FFs.
• Inclusive inelastic ep, en, ed: • Christy-Bosted parametrization of inclusive inelastic structure functions• Final-state nucleon generated assuming 𝛑N final state
• Inclusive DIS:• Final-state electron using CTEQ6 PDFs.
• ”Beam:” throw beam electrons at target from upstream (w optional ”rastering”, currently no option for position/angle offset)• SIDIS:
• N(e,e’h)X, with h = pi+/pi-/pi0/K+/K-/p/pbar• Leading-order cross section with CTEQ6 PDFs and DSS2007 qàh
fragmentation functions• Wiser: inclusive pion production• “Gun”: generic particle gun (any valid GEANT4 particle).
Generate flat in angle and momentum within user-defined limits
7/22/16 SBS Collaboration Meeting 2016 10
7/22/16 SBS Collaboration Meeting 2016 11
PYTHIA6.4 Interface
• PYTHIA6.4 interface written to study “minimum bias” events at high energies (W > 2 GeV), mainly to analyze trigger rates.
• Uses built-in ROOT/Pythia6 generator “TPythia6”• Requires ROOT build with Pythia6 add-on enabled• Pythia6 ROOT add-on is not a requirement for g4sbs, only for stand-alone event generator!• Standalone ROOT-based PYTHIA6 event generator produces ROOT tree containing events and primary particles• g4sbs reads events from a ROOT file in a standard format and generates primary particles to propagate through
experiment layout• Using “gamma/e-” option simulates ”all” physics with photon-nucleon invariant mass W > 2 GeV (includes
photoproduction)• Standard ROOT format (LUND-based) easily extensible to other event generators.
New: GEP Trigger analysis with “L2” logic
• Signal in HCAL logic group with max signal for elastic ep events, with different cuts on FPP event topology (top left)
• Top right: HCAL trigger efficiency vs. threshold for different event topologies
• Bottom right: Dependence of efficiency on FPP scattering angle in FPP1 (2)
7/22/16 SBS Collaboration Meeting 2016 12
Correlated ECAL-HCAL trigger efficiency
For events with a “good” scattering in FPP1 (left) and events with a “good” scattering in FPP2.
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ECAL-HCAL Kinematic Correlations in “Level 2” Coincidence Trigger
Implement ep angular correlations in the coincidence trigger, by listing for each HCAL trigger sum all ECAL trigger sums exceeding 0.1% of the total event rate
7/22/16 SBS Collaboration Meeting 2016 14
New: GEP Trigger rates with “L2” HCAL logic
• Top left: ECAL trigger rate vs threshold• Top right: HCAL L2 trigger rate vs
threshold (based on global OR of all possible 4x4 sums of HCAL signals)
• Bottom left: real coincidence rate (PYTHIA6 events) vs ECAL/HCAL thresholds.
• TO DO: analysis of accidentals (not trivial for correlated coincidence triger with many logic combinations)
7/22/16 SBS Collaboration Meeting 2016 15
GEM Rate Update
• Effect of reversing front-back orientation of all GEMS, for GEP 12 GeV2 configuration:• ~20% increase for FT layer 1 hit rates, smaller increases for
subsequent FT layers• Negligible changes in FPP1/FPP2 hit rates
7/22/16 SBS Collaboration Meeting 2016 16
BigBite and SBS optics from GEANT4• Charged particles are traced through magnetic field layout of BigBite/SBS in GEANT4 using
classical 4th-order Runge-Kutta numerical integration of the equation of motion.• Charged-particles deposit energy in GEMs, making “hits”—GEM “hits” are then smeared by a
Gaussian with a σ of 70 µm, representing the coordinate resolution of GEMs, and a straight-line track is fitted.
• In MC, we know the track parameters at the target and at the “focal plane” (GEM location).• We expand the reverse transport matrix in a power series in the measured track parameters:�x
0tgt
, y
0tgt
, y
tgt
, 1/p�=
X
i+j+k+l+m6
C
ijklm
x
0,y
0,y,1/px
i
fp
y
j
fp
x
0kfp
y
0lfp
x
m
tgt
• Track parameters at the target are linear functions of the expansion coefficients• Use standard linear algebra libraries, e.g., Singular Value Decomposition (SVD), to fit
the coefficients, avoid pitfalls of nonlinear fitting/numerical minimization/Minuit• Why fit 1/p instead of p or the traditional δ = 100 × (p/p0 – 1) in the expansion?
• SBS/BigBite are large-acceptance spectrometers—range of “delta” can equal or exceed ±100%, it is no longer a good expansion variable.
• SBS/BigBite are non-focusing, dipole spectrometersàan expansion in 1/p converges very quickly—xfp, x’fp are almost linear in 1/p for dipole magnets
7/22/16 SBS Collaboration Meeting 2016 17
SBS and BigBite Optics/Resolution from g4sbs—Old resultshpdiff
Entries 182096
Mean -4.054e-05
RMS 0.006654
/ ndf 2χ 45.57 / 7
Constant 8.624e+01± 2.604e+04
Mean 0.0000156± -0.0001566
Sigma 0.000017± 0.005374
- 1true
/preconp-0.10 -0.05 0.00 0.05 0.100
10000
20000
hpdiffEntries 182096
Mean -4.054e-05
RMS 0.006654
/ ndf 2χ 45.57 / 7
Constant 8.624e+01± 2.604e+04
Mean 0.0000156± -0.0001566
Sigma 0.000017± 0.005374
hxptardiffEntries 182096
Mean -3.464e-05
RMS 0.001435
/ ndf 2χ 6.17 / 7
Constant 6.557e+01± 1.659e+04
Mean 2.919e-06± -1.248e-05
Sigma 0.0000041± 0.0007234
tgt,true - (dx/dz)
tgt,recon(dx/dz)
-0.010 -0.005 0.000 0.005 0.0100
5000
10000
15000hxptardiff
Entries 182096
Mean -3.464e-05
RMS 0.001435
/ ndf 2χ 6.17 / 7
Constant 6.557e+01± 1.659e+04
Mean 2.919e-06± -1.248e-05
Sigma 0.0000041± 0.0007234
hyptardiffEntries 182096
Mean -1.429e-05
RMS 0.001491
/ ndf 2χ 17.11 / 7
Constant 6.296e+01± 1.561e+04
Mean 3.360e-06± -3.666e-05
Sigma 0.0000050± 0.0007755
tgt,true - (dy/dz)
tgt,recon(dy/dz)
-0.010 -0.005 0.000 0.005 0.0100
5000
10000
15000 hyptardiffEntries 182096
Mean -1.429e-05
RMS 0.001491
/ ndf 2χ 17.11 / 7
Constant 6.296e+01± 1.561e+04
Mean 3.360e-06± -3.666e-05
Sigma 0.0000050± 0.0007755
hytardiffEntries 182096
Mean 4.394e-05
RMS 0.002748
/ ndf 2χ 20.02 / 13
Constant 38.7± 9575
Mean 7.191e-06± -1.693e-05
Sigma 0.000011± 0.001615
tgt,true - y
tgt,recony
-0.02 -0.01 0.00 0.01 0.020
5000
10000 hytardiffEntries 182096
Mean 4.394e-05
RMS 0.002748
/ ndf 2χ 20.02 / 13
Constant 38.7± 9575
Mean 7.191e-06± -1.693e-05
Sigma 0.000011± 0.001615
p (GeV)2 4 6 8 10
-1tr
ue/p
reco
np
-0.10
-0.05
0.00
0.05
0.10
7/22/16 SBS Collaboration Meeting 2016 18
hpdiffEntries 114640
Mean -2.429e-05
RMS 0.01332
/ ndf 2χ 49.13 / 22
Constant 26.2± 6199
Mean 0.0000437± -0.0003809
Sigma 0.00005± 0.01137
- 1true
/preconp-0.10 -0.05 0.00 0.05 0.100
2000
4000
6000 hpdiffEntries 114640
Mean -2.429e-05
RMS 0.01332
/ ndf 2χ 49.13 / 22
Constant 26.2± 6199
Mean 0.0000437± -0.0003809
Sigma 0.00005± 0.01137
hxptardiffEntries 114640
Mean -1.47e-05
RMS 0.002242
/ ndf 2χ 90.76 / 22
Constant 24.4± 5328
Mean 4.854e-06± -1.602e-05
Sigma 0.000006± 0.001169
tgt,true - (dx/dz)
tgt,recon(dx/dz)
-0.02 -0.01 0.00 0.01 0.020
2000
4000
hxptardiffEntries 114640
Mean -1.47e-05
RMS 0.002242
/ ndf 2χ 90.76 / 22
Constant 24.4± 5328
Mean 4.854e-06± -1.602e-05
Sigma 0.000006± 0.001169
hyptardiffEntries 114640
Mean -1.365e-05
RMS 0.00335
/ ndf 2χ 20.55 / 22
Constant 18.3± 3393
Mean 1.14e-05± 1.67e-05
Sigma 0.000019± 0.001779
tgt,true - (dy/dz)
tgt,recon(dy/dz)
-0.02 -0.01 0.00 0.01 0.020
1000
2000
3000hyptardiff
Entries 114640
Mean -1.365e-05
RMS 0.00335
/ ndf 2χ 20.55 / 22
Constant 18.3± 3393
Mean 1.14e-05± 1.67e-05
Sigma 0.000019± 0.001779
hytardiffEntries 114640
Mean -3.35e-05
RMS 0.005182
/ ndf 2χ 35.73 / 27
Constant 14.2± 2518
Mean 2.140e-05± -5.003e-05
Sigma 0.00004± 0.00296
tgt,true - y
tgt,recony
-0.02 -0.01 0.00 0.01 0.020
1000
2000
hytardiffEntries 114640
Mean -3.35e-05
RMS 0.005182
/ ndf 2χ 35.73 / 27
Constant 14.2± 2518
Mean 2.140e-05± -5.003e-05
Sigma 0.00004± 0.00296
p (GeV)1 2 3 4 5
-1tr
ue/p
reco
np
-0.10
-0.05
0.00
0.05
0.10
SBS angle, vertex and momentum resolution for 1.4-Tesla uniform field, σp/p ~ 0.5% (average for 2-10 GeV pions)
BigBite angle, vertex and momentum resolution for ”map_696A.dat”, σp/p ~ 1.1%
Optics and Spin Transport Studies for GEP, Q2 = 12 GeV2
p (GeV)5 6 7 8 9
(deg
)be
ndθ
4
6
8
thetatrack*180.0/TMath::Pi():phtemp
Entries 10141
Mean 0.001816
RMS 0.1244
xptar0.2− 0.1− 0.0 0.1 0.2 0.30
20
40
60
80
100
120
140
160
htempEntries 10141
Mean 0.001816
RMS 0.1244
xptarhtemp
Entries 10141
Mean 0.00249−
RMS 0.03907
yptar0.10− 0.08− 0.06− 0.04− 0.02− 0.00 0.02 0.04 0.06 0.080
20
40
60
80
100
120
140
160
180
htempEntries 10141
Mean 0.00249−
RMS 0.03907
yptar
htempEntries 10141
Mean 0.004617
RMS 0.03375
ytar0.06− 0.04− 0.02− 0.00 0.02 0.04 0.06 0.080
20
40
60
80
100
120
140
160
htempEntries 10141
Mean 0.004617
RMS 0.03375
ytarhtemp
Entries 10141
Mean 6.98
RMS 1.152
p5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.00
20
40
60
80
100
120
140
htempEntries 10141
Mean 6.98
RMS 1.152
p
SBS angular and vertex acceptance for GEP highest Q2
Track vertical bend angle vs. momentum
• GEANT4 simulation for optics and spin transport:• Use “particle gun” generator with limits chosen wide enough to populate full acceptance of SBS (use 40 cm target)• Proton momenta generated in the range of 5-9 GeV (corresponding to highest Q2 of GEP)• Generate 10,000 protons in three different starting spin orientations in the fixed TRANSPORT coordinate system:
• Pure “X” (vertically down)• Pure “Y” (horizontal, toward small angle)• Pure “Z” (along SBS central ray)
• Fit reconstruction coefficients and spin transport matrix elements
7/22/16 SBS Collaboration Meeting 2016 19
SBS optics fitting from GEANT4 htemp
Entries 10110Mean 06− 7.578eRMS 0.0003706
/ ndf 2χ 16.82 / 12Constant 13.6± 953.9 Mean 06− 3.495e±07 −3.636e− Sigma 0.0000037± 0.0002795
xptar-xptarrecon0.003− 0.002− 0.001− 0.000 0.001 0.002 0.0030
200
400
600
800
1000htemp
Entries 10110Mean 06− 7.578eRMS 0.0003706
/ ndf 2χ 16.82 / 12Constant 13.6± 953.9 Mean 06− 3.495e±07 −3.636e− Sigma 0.0000037± 0.0002795
xptar-xptarrecon {abs(xptar-xptarrecon)<.003}htemp
Entries 10120Mean 05−1.173e− RMS 0.001012
/ ndf 2χ 27.24 / 7Constant 20.0± 1357 Mean 06− 7.853e±06 −1.205e− Sigma 0.0000087± 0.0006144
yptar-yptarrecon0.010− 0.005− 0.000 0.005 0.0100
200
400
600
800
1000
1200
1400htemp
Entries 10120Mean 05−1.173e− RMS 0.001012
/ ndf 2χ 27.24 / 7Constant 20.0± 1357 Mean 06− 7.853e±06 −1.205e− Sigma 0.0000087± 0.0006144
yptar-yptarrecon {abs(yptar-yptarrecon)<.01}
htempEntries 10123Mean 06− 1.369eRMS 0.002316
/ ndf 2χ 23.67 / 9Constant 16.7± 1155 Mean 05− 1.977e±05 −2.165e− Sigma 0.000021± 0.001493
ytar-ytarrecon0.020− 0.015− 0.010− 0.005− 0.000 0.005 0.010 0.015 0.0200
200
400
600
800
1000
1200 htempEntries 10123Mean 06− 1.369eRMS 0.002316
/ ndf 2χ 23.67 / 9Constant 16.7± 1155 Mean 05− 1.977e±05 −2.165e− Sigma 0.000021± 0.001493
ytar-ytarrecon {abs(ytar-ytarrecon)<.02}htemp
Entries 10075
Mean 0.0001236RMS 0.009052
/ ndf 2χ 17.34 / 16Constant 9.6± 637.8
Mean 0.0000931± 0.0002882 Sigma 0.00011± 0.00662
precon/p-1.00.04− 0.02− 0.00 0.02 0.040
100
200
300
400
500
600
700 htempEntries 10075
Mean 0.0001236RMS 0.009052
/ ndf 2χ 17.34 / 16Constant 9.6± 637.8
Mean 0.0000931± 0.0002882 Sigma 0.00011± 0.00662
precon/p-1.0 {abs(precon/p-1.0)<.05}
xptarrecon0.2− 0.1− 0.0 0.1 0.2 0.3
xptar
0.2−
0.1−
0.0
0.1
0.2
0.3
xptar:xptarrecon
yptarrecon0.10− 0.08− 0.06− 0.04− 0.02− 0.00 0.02 0.04 0.06 0.08
yptar
0.10−
0.08−
0.06−
0.04−
0.02−
0.00
0.02
0.04
0.06
0.08
yptar:yptarrecon
ytarrecon0.08− 0.06− 0.04− 0.02− 0.00 0.02 0.04 0.06 0.08
ytar
0.06−
0.04−
0.02−
0.00
0.02
0.04
0.06
0.08
ytar:ytarrecon
precon5 6 7 8 9
p
5.0
5.5
6.0
6.5
7.0
7.5
8.0
8.5
9.0
p:precon
• SBS angle, vertex and momentum resolution for 5-9 GeV protons
• sigma(xptar) ~ 0.3 mrad• sigma(yptar) ~ 0.6 mrad• sigma(ytar) ~ 1.5 mm• sigma(p)/p ~ 0.66%• Improvement of the fit not
significant beyond about 4th-order expansion of reconstruction coefficients
7/22/16 SBS Collaboration Meeting 2016 20
Spin transport properties of SBS in GEP
p (GeV)5 6 7 8 9
(deg
)χ
60
70
80
90
100chi*180.0/TMath::Pi():p
xxS1.0− 0.5− 0.0 0.5 1.00
100
200
300
yxS1.0− 0.5− 0.0 0.5 1.00
100
200
300
400
zxS1.0− 0.5− 0.0 0.5 1.00
500
1000
1500
xyS1.0− 0.5− 0.0 0.5 1.00
50
100
150
200
yyS1.0− 0.5− 0.0 0.5 1.00
1000
2000
3000
zyS1.0− 0.5− 0.0 0.5 1.00
200
400
xzS1.0− 0.5− 0.0 0.5 1.00
500
1000
1500
yzS1.0− 0.5− 0.0 0.5 1.00
100
200
zzS1.0− 0.5− 0.0 0.5 1.00
100
200
300
400
• Spin precession in a magnetic field is governed by the Thomas-BMT equation• For an almost pure dipole field, as in SBS, the proton spin precesses relative to its trajectory
by an angle:
• Precession angle is almost constant within useful acceptance of SBS for elastic ep events (cancellation between momentum dependence of gamma and thetabend)
BMT equation for protons
� = �p✓bend
7/22/16 SBS Collaboration Meeting 2016 21
Spin fit results (5th-order)htemp
Entries 10100
Mean 0.0001228−
RMS 0.004318
Pxfp-Pxfprecon0.03− 0.02− 0.01− 0.00 0.01 0.02 0.030
200
400
600
800
1000
1200
htempEntries 10100
Mean 0.0001228−
RMS 0.004318
Pxfp-Pxfprecon {abs(Pxfp-Pxfprecon)<.03}htemp
Entries 10112
Mean 05− 3.055e
RMS 0.004307
Pyfp-Pyfprecon0.03− 0.02− 0.01− 0.00 0.01 0.02 0.030
200
400
600
800
1000
1200
1400
1600
1800htemp
Entries 10112
Mean 05− 3.055e
RMS 0.004307
Pyfp-Pyfprecon {abs(Pyfp-Pyfprecon)<.03}
htempEntries 10086
Mean 05−6.089e−
RMS 0.005175
Pzfp-Pzfprecon0.03− 0.02− 0.01− 0.00 0.01 0.02 0.030
200
400
600
800
1000
1200htemp
Entries 10086
Mean 05−6.089e−
RMS 0.005175
Pzfp-Pzfprecon {abs(Pzfp-Pzfprecon)<.03}htemp
Entries 10141
Mean 0.9988
RMS 0.001751
Determinant0.985 0.990 0.995 1.000 1.005 1.010 1.0150
200
400
600
800
1000
htempEntries 10141
Mean 0.9988
RMS 0.001751
Determinant
Pxfprecon1.0− 0.8− 0.6− 0.4− 0.2− 0.0 0.2 0.4
Pxfp
1.0−
0.8−
0.6−
0.4−
0.2−
0.0
0.2
0.4
Pxfp:Pxfprecon
Pyfprecon0.2− 0.0 0.2 0.4 0.6 0.8 1.0
Pyfp
0.2−
0.0
0.2
0.4
0.6
0.8
1.0
Pyfp:Pyfprecon
Pzfprecon0.4− 0.2− 0.0 0.2 0.4 0.6 0.8 1.0
Pzfp
0.2−
0.0
0.2
0.4
0.6
0.8
1.0
Pzfp:Pzfpreconhtemp
Entries 10141
Mean 0.9988
RMS 0.001751
Determinant0.985 0.990 0.995 1.000 1.005 1.010 1.0150
200
400
600
800
1000
htempEntries 10141
Mean 0.9988
RMS 0.001751
Determinant
• Fit deviations from the ideal dipole approximation up to 5th-order (still some room for improvement)
• Fit individual matrix elements directly• Don’t enforce any event-by-event unitary constraints on the 3x3 rotation matrix.• Determinant results very close to 1 in most events anyway.• TO DO: Add sieve slit to MC, analyze systematics of spin transport calculation.
7/22/16 SBS Collaboration Meeting 2016 22
C16/ECAL Thermal Annealing Simulation
• Longitudinal segmentation of C16 lead-glass to implement depth-dependent radiation-induced darkening
7/22/16 SBS Collaboration Meeting 2016 23
C16/ECAL Thermal Annealing Simulationhdose_rate_vs_depth_ECAL
Entries 3099057
Mean 10.07
RMS 8.656
Depth in lead-glass (cm)0 5 10 15 20 25 30 35 40 45 50
Loca
l dos
e ra
te (k
rad/
h)
0.00
0.02
0.04
0.06
0.08
0.10hdose_rate_vs_depth_ECAL
Entries 3099057
Mean 10.07
RMS 8.656
Aµ = 75 beam
, I2ECAL in GEP high Q
Dose_rate_vs_Zdepth
Entries 148197
Mean 7.419
RMS 7.827
Depth in lead-glass (cm)0 5 10 15 20 25 30 35 40 45 50
Loca
l dos
e ra
te (k
rad/
h)
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8Dose_rate_vs_Zdepth
Entries 148197
Mean 7.419
RMS 7.827
Aµ = 20 beam
C16 in Hall A Test, I
hratioEntries 69
Mean 16.14
RMS 11.08
/ ndf 2χ 6.22 / 16
p0 0.464± 3.665
Depth in lead-glass (cm) 0 5 10 15 20 25 30 35 40 45 50
Rat
io C
16/G
EP
0
1
2
3
4
5
6
7
8
hratioEntries 69
Mean 16.14
RMS 11.08
/ ndf 2χ 6.22 / 16
p0 0.464± 3.665
Aµ = 20 beam
C16 in Hall A Test, I
• GEANT4 dose rate calculation, comparison between GEP 12 GeV2
case (left), C16 prototype test in Hall A (middle), and ratio C16/GEP (right)
7/22/16 SBS Collaboration Meeting 2016 24
C16 Signal Reduction after calibration of model
, max not in edge blockphe 4 summed N×4 0 500 1000 15000.00
0.02
0.04
0.06
0.08
0.10
C16, rad. damage OFF
C16 rad. damage ON
7/22/16 SBS Collaboration Meeting 2016 25
C16 Individual block spectra
Num. photoelectrons0 200 400 600 800 100012001400
1
10
210
310
410
Num. photoelectrons0 200 400 600 800 100012001400
1
10
210
310
410
Num. photoelectrons0 200 400 600 800 100012001400
1
10
210
310
410
Num. photoelectrons0 200 400 600 800 100012001400
1
10
210
310
410
Num. photoelectrons0 200 400 600 800 100012001400
1
10
210
310
410
Num. photoelectrons0 200 400 600 800 100012001400
1
10
210
310
410
Num. photoelectrons0 200 400 600 800 100012001400
1
10
210
310
410
Num. photoelectrons0 200 400 600 800 100012001400
1
10
210
310
410
Num. photoelectrons0 200 400 600 800 100012001400
1
10
210
310
410
Num. photoelectrons0 200 400 600 800 100012001400
1
10
210
310
410
Num. photoelectrons0 200 400 600 800 100012001400
1
10
210
310
410
Num. photoelectrons0 200 400 600 800 100012001400
1
10
210
310
410
Num. photoelectrons0 200 400 600 800 100012001400
1
10
210
310
410
Num. photoelectrons0 200 400 600 800 100012001400
1
10
210
310
410
Num. photoelectrons0 200 400 600 800 100012001400
1
10
210
310
410
Num. photoelectrons0 200 400 600 800 100012001400
1
10
210
310
410
• Left: Simulated number of photoelectrons in C16 blocks, elastic events
• Right: Actual data from prototype (assumption of identical spectra in “undamaged” state, validated by GEANT4, used to simplify gain matching)
7/22/16 SBS Collaboration Meeting 2016 26
Projected ECAL Performance
Energy deposition in block (GeV)0 1 2 3 4
Num
. pho
toel
ectr
ons
in P
MT
0
1000
2000
3000
Slope = ( 548.1 +/- 0.734) phe/GeV
Energy deposition in block (GeV)0 1 2 3 4
Num
. pho
toel
ectr
ons
in P
MT
0
1000
2000
3000
Slope = ( 527.9 +/- 0.7512) phe/GeV
• Left: ECAL photoelectron yield vs. energy deposition, undamaged case• Right: ECAL photoelectron yield vs. energy deposition, thermal equilibrium state in
GEP 12 GeV2 point• Average ratio equilibrium/undamaged = (96.3 +/- 0.2) %• More details in final report to DOE (see Mark's final report to DOE (requires login) )
7/22/16 SBS Collaboration Meeting 2016 27
Documentation Update
• Documentation remains in Hall A Wiki for now: https://hallaweb.jlab.org/wiki/index.php/Documentation_of_g4sbs
• Up-to-date as of now; recent additions include documentation of ROOT output file and tree structure
7/22/16 SBS Collaboration Meeting 2016 28
Other ongoing projects
• RTPC simulation for TDIS (Rachel Montgomery, Glasgow)• GEn recoil with charge-exchange polarimetry (John
Annand, Glasgow)• Optimization of GMn acceptance• Radiation budget calculations (Dasuni Adikaram)
7/22/16 SBS Collaboration Meeting 2016 29
Near-term plans for Monte Carlo• Geometries needed:
• Sieve slit• Details of beamline/targets for experiments/configurations other than
GEP, 12 GeV2
• Full digitization of detectors: • More detailed GEM description, with parametrized strip response,
clusters, etc. • Generate pseudo-data: full signal chain from energy deposition to
parametrized voltage vs. time, ADC/TDC values• Develop and benchmark reconstruction algorithms• Highest priority next few months: analysis of GEM tracking
• Trigger simulations for BigBite w/GRINCH• Re-do experiment figure-of-merit projections, prepare for
Jeopardy/PAC reapproval process• Optimize detector layout for SIDIS• Simulation/results document/white paper
7/22/16 SBS Collaboration Meeting 2016 30