Transcript Super BigBite Spectrometer Overview Andrew Puckett, University of Connecticut on behalf of the SBS Collaboration Hall A Collaboration Meeting December 16, 2013

Super BigBite
Spectrometer Overview
Andrew Puckett, University of Connecticut
on behalf of the SBS Collaboration
Hall A Collaboration Meeting
December 16, 2013
Outline
• Physics Program—approved experiments
• Nucleon form factors at large Q2
• GEp—Experiment E12-07-109
• GEn—Experiment E12-09-016
• GMn—Experiment E12-09-019
• SIDIS, TMDs, neutron transverse spin structure
• Neutron transverse SSAs—Experiment E12-09-018
• Hardware overview—SBS program components and
“ancillary” equipment
• Related activities
• Summary and Conclusions
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Acknowledgements
This talk relies heavily on material prepared by and representing the efforts of many
dedicated members and institutions of the SBS Collaboration. Special thanks for
contributions to this talk from collaborators/institutions including but not limited to:
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J. Annand, Glasgow U.
C. Ayerbe, W&M
G. Cates, UVA
E. Cisbani, INFN
F. de Persio, INFN
G. Franklin, CMU
M. Jones, JLab
C. Keppel, JLab
M. Khandaker, ISU
J. LeRose, JLab
N. Liyanage, UVA
C. F. Perdrisat, W&M
B. Quinn, CMU
S. Riordan, UMass Amherst
A. Sarty, SMU
R. Wines, JLab
B. Wojtsekhowski, JLab
The speaker also thanks the SBS CC, the Hall A Collaboration, the meeting organizers,
JLab management for support for the SBS physics program, and DOE for funding support
of the SBS construction.
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SBS original motivation (2007)—High-Q2 GE/GM from PT method
Results of Polarization Transfer Experiments at “large” Q2
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GEp-I: Phys. Rev. Lett. 84, 1398 (2000)
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673 INSPIRE-HEP citations (12/15/2013)
GEp-II: Phys. Rev. Lett. 88, 092301 (2002)
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593 INSPIRE-HEP citations (12/15/2013)
GEp-III: Phys. Rev. Lett. 104, 242301 (2010)
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109 INSPIRE-HEP citations (12/15/2013)
Extraction of the same physical quantity from different experimental
observables with different results!
Crisis for the one-photon-exchange approximation and the “clean”
interpretation of electron scattering data?
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Statistical FOM of polarization transfer expt.’s
Previous PT experiments: focusing magnetic spectrometers, small proton solid angle/ΔQ2
Theoretical PT FOM vs. Q2 for different beam
energies
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Theoretical PT FOM vs. ε at various Q2 values
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How to reach higher Q2?
• Elastic ep cross section scales roughly as
E2/Q12
• FPP efficiency is roughly Q2-independent
• FPP analyzing power scales roughly as 1/pp
~ M/Q2
• Therefore, statistical FOM scales roughly as
NAy2 ~ E2/Q16
• Increase beam polarization?  cannot be
increased much further: 80%100% would
only increase FOM by 1.6
• Increase Ay? Material with highest known Ay
= LH2  cost and safety prohibitive?
• Increase luminosity? Best possible at JLab
12 GeV ~ 1039 cm-2 s-1; ~factor of 2 above 6
GeV expt’s.
• Most room for growth? Increase solid
angle/Q2 acceptance!
• JLab PAC-approved GEp experiment: E1207-109; 45 days, max. Q2 = 12 GeV2,
Δ(μGE/GM) ~ 0.07
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SBS GEp Projected Results
• The SBS GEP experiment in ~11
days running will dramatically
improve the statistical precision in
μGE/GM at Q2 in the range
overlapping GEp-II/III, and in 30
days will reach comparable
precision at 12 GeV2 to that of
GEp-II/III at 5-6 GeV2
• Data of such precision carry
significant discovery potential and
may (or may not) settle the
questions of a zero crossing of GEp
and the onset (or lack thereof) of
dimensional scaling.
• Combined with GEN, GMN,
GMP experiments, full flavor
decomposition of F1 and F2
becomes possible up to 10 GeV2
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Neutron form factors: E12-09-016 & E12-09-019
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SBS as neutron arm w/48D48 + HCAL
Magnet sweeps charged particles out of acceptance,
limiting backgrounds
BigBite as electron arm w/upgraded 12 GeV
detector package (including re-use of GEMs, built
for GEP, not otherwise in use during BigBite expt’s.
High-luminosity polarized Helium-3 for GEN
Standard LH2/LD2 for GMN
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SIDIS/Neutron Transversity—E12-09-018
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BigBite as electron arm: DIS electrons at ~30
deg., 1 < p < 4 GeV
SBS as hadron arm @ 14 deg.
High-luminosity 3He target (same as GEN,
w/added flexibility of spin orientation)
Ancillary hardware: re-use HERMES RICH
detector as cost-effective PID solution
High-impact SSA/TMD physics (Collins/Sivers),
100X higher statistical FOM than HERMES,
high-x data.
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Super BigBite Spectrometer—Design Concepts
• Basic concept: 48D48 dipole magnet
from BNL + flexible detector package:
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Magnet Gap: 47 x 122 x 122 cm3
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Distance from tgt. to magnet yoke:
1.6-2.5 meters
Solid angle ~40-60 msr.
Bdl ~ 2 T-m. Momentum acceptance:
p > 2 GeV/c
Weight ~ 100 tons
Cut in yoke for passage of beam pipe
to reach forward angles & large ΔΩ
• Build/expand on success of BigBite
approach:
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Moderate solid-angle
Large momentum bite w/moderate
momentum resolution: σp/p ~ 1%
High-luminosity operation w/detectors
in direct view of the targethigh soft
photon fluxGEM technology (F.
Sauli, 1997)
Trigger based on large energy deposit
in total-absorption calorimeters
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SBS Magnet and
Infrastructure (JLab)
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From R. Wines Talk @DOE Review, 2013-11-4/5
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Adapted from R. Wines Talk @DOE Review, 2013-11-4/5
GMn, Q2 =
13.5 GeV2
GEp, Q2 =
12 GeV2
• HRS pivot and links limit space for SBS magnet
support: special counterweight support structure being
designed for GEP and other configurations requiring
short magnet distance
• Beam line magnetic shielding (active and passive)
being designed to reduce transverse component of SBS
field on the beamline
• Field clamps being designed to limit SBS field at
polarized target (upstream) and detectors (downstream)
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GEn, Q2 =
10 GeV2
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SBS Polarimeter GEMs
(UVA)
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From N. Liyanage Talk at SBS DOE Review, 2013-11-4/5
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From N. Liyanage Talk at SBS DOE Review, 2013-11-4/5
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From N. Liyanage Talk at SBS DOE Review, 2013-11-4/5
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SBS Front tracker GEMs
(INFN)
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From E. Cisbani Talk @DOE Review, 2013-11-4/5
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Front Tracker: main technical solutions
 Use COMPASS approach: 3xGEM, 2D readout - one significant difference: new single mask
GEM foil (instead of double mask) – cheaper and faster production
 Modular design: chambers consists of 3 independent GEM modules (40x50 cm2) with thin
dead area
 Electronics around the module, direct connection; 90 degree bending between modules
 External support frame in carbon fiber (long bars) to minimize thermal deformation
Requirements:
Hit spatial resolution ~ 70 mm
Stand large background (g ~ 250
MHz/cm2, e/p 160 kHz/cm2)
Transverse area > 40x120 cm2
cm2
40x50
module
Front Tracker Chamber: 40x150 cm2
SBS Front Tracker
Event rate ~ 20 kevents/s
Reuse: SBS/GEp5, BigBite/Gen,
BigBite/A1n …
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FT: GEM Module construction process
GEM Foils
HV curing and
quality test
Module
production fully
established in
Catania
Module
characterization
in Rome
Production speed
1 module/month
Electronics
Test
Permaglas Frames
Visual Inspection
Ultrasound bath
cleaning
Stretching
Gluing
Electronics integration
Test and characterization by rad.
source and cosmics
Assembling
gas lines
Put together
(align on reference pins)
Clean room
Finalization
(solder resistor, check HV)
SBS Front Tracker
Glue Curing
in vacuum
(>24 h)
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Hadron Calorimeter for SBS (CMU, G. Franklin et al.)
Requirements for SBS experiments
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Match acceptance of SBS magnet/FPP
High threshold and high trigger efficiency—goal:
95% efficiency, threshold 25% avg. signal
Linear energy response
Timing resolution
• TOF < 1.0 nsec required, Goal: 0.5 ns
Angular resolution ~5 mrad
Design
Concept based on COMPASS HCAL1, but:
Faster scintillator and wavelength shifter
WLS moved to center
Novel light guide
2-inch PMTs faster, better quantum efficiency
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ECAL for GEP experiment: W&M, CMU, JLab et al.
Purpose:
• Coincidence detection of elastically scattered electron
in epep
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BigCal opened,
Feb. 2008, end
of GEp2γ/WACS
Manage DAQ rates—efficient trigger at 75% of elastic
ep e- energy
• coarse ep angular correlation at trigger level
Measure e- energy/scattering angles
• Reject inelastic backgrounds
• Restrict search area for tracking in FT of proton
arm
• Re-use BigCal from GEp-III
Performance requirements:
• Energy resolution: σE/E ≤ 10% at 3.5 GeV
• Coordinate resolution: 6-8 mm
• Acceptance matching with proton arm.
• Luminosity: 8 x 1038 cm-2 s-1
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Annealing of rad. damage: from Hall C experience and
GEANT MC expect ~6% gain loss/hr (worst case).
Need to cure glass at ~5X faster rate than previously
realized
UV annealing requires PMT HV off—curing for 1 hour
out of every 8.
In situ thermal annealing also under investigation
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BigCal rad. damage in GEp-III
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High-luminosity Polarized 3He Target (UVA, G. Cates et al.)
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Dramatic increases in 3He SEOP rate from technical
advances: “hybrid” tech. (Rb+K), narrow-band lasers.
Diffusion rate through transfer tube now a bottleneck.
~5X increase in (Lumi. x pol.2) in new targets using
convection-driven flow (faster recirculation of polarized gas)
SBS Helium-3 Performance Specs:
~60% polarization, 60 cm cell length at >60 μA (GEN2)
~60% polarization, 60 cm cell length at >40 μA (SIDIS)
Flexible orientation of target spin any direction (SIDIS) and
fast (T~120 s), adiabatic spin rotation—control systematics
Metal end windows—prevent cell rupture due to rad. damage
Recent developments:
Convection-driven flow concept already demonstrated
Present R&D focused on metal end windows w/spin
relaxation rates consistent w/above performance specs.
• Exciting progress very recently (see right)
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Coordinate Detector (CD) for SBS (ISU, SMU, et al.)
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Purpose:
GEP expt.—precise coordinate measurement
for angular reconstruction in GEP—
• Use elastic ep angular correlations to
restrict search area for SBS tracking;
design goal >~95% proton reconstruction
efficiency
• Reject inelastic backgrounds
GEN/GMN expt.—use as proton veto
Performance Requirements:
Coordinate resolution <~ 1 mm
Timing resolution ~1 ns
“Occupancy” <~ 5% (prob. of accidental hit
within ~2.5 cm (~2.5σx) of BigCal shower
coordinate
High detection efficiency >~ 90%
Original plan calls for GEM-based CD.
New plan (pending approval) calls for
scintillator-based CD: design, simulation and
cost estimates suggest better performance at
lower cost than GEM-based solution.
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Other Related Activities
• BigBite upgrades:
• GRINCH—highly segmented gas Cherenkov detector (see talk of H. Yao (W&M) later in this session)
• Silicon microstrip detector for SBS—improve vertex (momentum) resolution by factor of 1.5
(2) respectively—see talk by F. De Persio (INFN) in this session
• Project management for DOE-funded official SBS program: JLab (J. LeRose et al.)—SBS
program recently underwent annual DOE review (Nov. 4/5)
• SBS Collaboration Charter adopted and Coordinating Committee formed; initially chaired by
B. Quinn (CMU)—consists of 1 representative from each approved expt., plus two SBS
program scientists and Hall A leader
• Improved cryotarget design work by S. Covrig—benefit all high-luminosity expts. in Halls
A/C including SBS GEP/GMN
• SBS Monte Carlo Simulations in GEANT4: Coordination of efforts and code management by
S. Riordan
• HERMES/SBS RICH refurbishment effort for SIDIS experiment—work starting soon:
• Definition of scope of work and budget estimate in development, informed by physics/detector simulations
• UConn group (A. Puckett) intends to assume primary responsibility for this work
• New, novel physics ideas being explored, including but not limited to:
• Pion structure function via low-energy spectator tagging of Sullivan process—DIS from the pion cloud of
the nucleon (see tomorrow’s talk by J. Zhang).
• Dihadron SIDIS, vector meson production, ...
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Summary and Conclusions
• SBS is a new, cost-effective magnetic spectrometer based on
time-tested “detectors behind a dipole magnet” approach
• Designed to detect forward-going, high-momentum particles
w/moderate solid angle and large momentum bite at high
luminosity (and simple, straight-line tracking in field-free
regions)
• Will facilitate the measurement of all four nucleon elastic EMFFs
(when combined with HRS GMp experiment) to at least 10
GeV2—tripling the Q2 range for which a precise flavor
decomposition of nucleon FFs is possible
• Enables additional, high-impact physics beyond form factors:
• SIDIS/neutron transversity experiment approved, 64 days, A- rating
• New ideas (e.g. pion structure function)
• Significant progress has already occurred (and continues) on the
main SBS program components and “ancillary” equipment.
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