recent results from g4sbs · 2016. 7. 22. · • hydrogen • 3he • (fictional ... • using...

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


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the uconn_dev branch, periodically merged into the (more stable, but out-of-date) master branch.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


Existing Geometries—GEP


• 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


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


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?


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.


“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



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)


Correlated ECAL-HCAL trigger efficiency

For events with a “good” scattering in FPP1 (left) and events with a “good” scattering in FPP2.


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


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)


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


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


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


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


hpdiffEntries 114640

Mean -2.429e-05

RMS 0.01332

/ ndf 2χ 49.13 / 22


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


Mean 0.0000437± -0.0003809

Sigma 0.00005± 0.01137


Mean -1.47e-05

RMS 0.002242

/ ndf 2χ 90.76 / 22


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


Mean -1.47e-05

RMS 0.002242

/ ndf 2χ 90.76 / 22


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


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


Mean 1.14e-05± 1.67e-05

Sigma 0.000019± 0.001779


Mean -3.35e-05

RMS 0.005182

/ ndf 2χ 35.73 / 27


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


Mean -3.35e-05

RMS 0.005182

/ ndf 2χ 35.73 / 27


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


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


yptar-yptarrecon {abs(yptar-yptarrecon)<.01}

htempEntries 10123Mean 06− 1.369eRMS 0.002316


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


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


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


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.


C16/ECAL Thermal Annealing Simulation

• Longitudinal segmentation of C16 lead-glass to implement depth-dependent radiation-induced darkening


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)


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


C16 Individual block spectra

Num. photoelectrons0 200 400 600 800 100012001400

1

10

210

310

410


1

10

210

310

410


1

10

210

310

410


1

10

210

310

410


1

10

210

310

410


1

10

210

310

410


1

10

210

310

410


1

10

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• 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)


Projected ECAL Performance

Energy deposition in block (GeV)0 1 2 3 4

Num

. pho

toel

ectr

ons

in P

MT

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1000

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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) )


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


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)


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


recent results from g4sbs · 2016. 7. 22. · • hydrogen • 3he • (fictional ... • using...

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