the science • the experiment • status &...
TRANSCRIPT
June 23, 2009 PAVI09 S. Page, Univ. Manitoba 1
The Qweak Experiment at Jefferson Lab
• The science• The experiment• Status & milestones
With thanks to:• PAVI09 organizers for this kind invitation• Qweak collaboration for their support, hard work (& slides!)• DOE, NSF and NSERC for funding our experiment• Monday and Tuesday morning speakers for providing a great
introduction to this talk !
June 23, 2009 PAVI09 S. Page, Univ. Manitoba 2
The Science: Running of sin2θW
Qweak: 1. Best error bar by a factor of two2. Cleanest of all the hadronic testsQweak:
Stepping stone to 12 GeV Moller expt
Latestatomictheory
Theory: J. Erler, M.J. Ramsey-Musolf, et al.
June 23, 2009 PAVI09 S. Page, Univ. Manitoba 3
The Science: Parity violating ep scattering
( )2Q
20
20 4
4Q
2QQ p
weakFd d GA B
dQ
dσ σσ σ
+ −→
→
−
θ
+
− −⎡ ⎤ ⎡ ⎤≡ ⎯ ⎯ ⎯→ +⎢ ⎥ ⎣ ⎦+ πα⎣ ⎦“ form factor” correction…
PV asymmetry:
A ≈ - 3 x 10-7 ; δA/A = 2% δQwp / Qw
p = 4% δsin2θW / sin2θW = 0.3%
The challenge:
June 23, 2009 PAVI09 S. Page, Univ. Manitoba 4
Extrapolation of Higher Q2 PV Data
Q2 (GeV2)
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The Experiment
spin (+)
spin (-)
1 GeV e- beam
protontarget
(elastic) scattered e- at 8º
Q2 = 0.03 GeV2
85%1% ( .)
zPmeas±
7
1.165150 180
. . / 10
GeVA
h c I Iμ
δ −
−
<
2% measurement of 0.3 ppm asymmetry
LuminosityMonitor
e− Beam
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D. Armstrong, A. Asaturyan, T. Averett, J. Benesch, J. Birchall, P. Bosted, A. Bruell, C. Capuano,R. D. Carlini1 (Principal Investigator), G. Cates, C. Carrigee, S. Chattopadhyay, S. Covrig, C. A. Davis,
K. Dow, J. Dunne, D. Dutta, R. Ent, J. Erler, W. Falk, H. Fenker, J.M. Finn1*, T. A. Forest, W. Franklin, D. Gaskell, M. Gericke, J. Grames, K. Grimm, F.W. Hersman, D. Higinbotham, M. Holtrop,
J.R. Hoskins, K. Johnston, E. Ihloff, M. Jones, R. Jones, K. Joo, J. Kelsey, C. Keppel, M. Khol, P. King, E. Korkmaz, S. Kowalski1, J. Leacock, J.P. Leckey, L. Lee, A. Lung, D. Mack, S. Majewski, J. Mammei,
J. Martin, D. Meekins, A. Micherdzinska, A. Mkrtchyan, H. Mkrtchyan, N. Morgan, K. E. Myers, A. Narayan, A. K. Opper, SA Page1, J. Pan, K. Paschke, M. Pitt, M. Poelker, T. Porcelli, Y. Prok, W. D. Ramsay, M. Ramsey-Musolf, J. Roche, N. Simicevic, G. Smith2, T. Smith, P. Souder, D. Spayde, B. E. Stokes,
R. Suleiman, V. Tadevosyan, E. Tsentalovich, W.T.H. van Oers, W. Vulcan, P. Wang, S. Wells, S. A. Wood, S. Yang, R. Young, H. Zhu, C. Zorn
1Spokespersons *deceased 2Project Manager
College of William and Mary, University of Connecticut, Instituto de Fisica, Universidad Nacional Autonoma de Mexico, University of Wisconsin, Hendrex College, Louisiana Tech University, University of Manitoba, Massachusetts Institute of Technology, Thomas Jefferson National Accelerator Facility, Virginia Polytechnic Institute & State University, TRIUMF,
University of New Hampshire, Yerevan Physics Institute, Mississippi State University, University of Northern British Columbia, Cockroft Institute of Accelerator Science and Technology, Ohio University, Hampton University,
University of Winnipeg, University of Virginia, George Washington University, Syracuse University, Idaho State University, University of Connecticut, Christopher Newport University
The Qweak Collaboration
June 23, 2009 PAVI09 S. Page, Univ. Manitoba 7
35 cm Liquid Hydrogen Target
Polarized Electron Beam
Collimator W ith Eight Openingsθ = 9 ± 2°
Toroidal Magnet
Eight Fused Silica (quartz)Cerenkov Detectors
5 inch PMT in Low GainIntegrating Mode on Each
End of Quartz Bar
Elastically Scattered Electrons
325 cm
580 cm
LuninosityMonitor
Region 3Dri ft Cham bers
Region 2Drift Chambers
Region 1GEM Detectors
35 cm Liquid Hydrogen Target
Primary Collimator with 8 openings
Region IGEM Detectors
Region IIDrift Chambers
Toroidal Magnet
Region IIIDrift Chambers
Elastically Scattered Electron
Eight Fused Silica (quartz) Čerenkov Detectors Integrating Mode
Luminosity Monitors
~3.2 m
Region I, II and III detectors are for Q2
measurements at low beam current
Experimental Details ( )22 4~ Q Q QpweakA B Q⎡ ⎤+⎣ ⎦
June 23, 2009 PAVI09 S. Page, Univ. Manitoba 8
2% on Az ≈ 4% on Qw ≈ 0.3% on sin2θW
Uncertainty ΔAz/Az ΔQw/Qw
Statistical (2,544 hours at 180 μA) 2.1% 3.2%
Systematic: 2.6%Hadronic structure uncertainties --- 1.5%Beam polarimetry 1.0% 1.5%Absolute Q2 determination 0.5% 1.0%Backgrounds 0.5% 0.7%Helicity correlated beam properties 0.5% 0.7%
Total: 2.5% 4.1%
Error BudgetPV asymmetry is remarkably sensitive to sin2θw !
Final error on Δsin2θW / sin2θW includes QCD uncertainties (1-loop) in calculation of the running 0.2% → 0.3%.Final error on Δsin2θW / sin2θW includes QCD uncertainties (1-loop) in calculation of the running 0.2% → 0.3%.
June 23, 2009 PAVI09 S. Page, Univ. Manitoba 9
Systematic Errors – H.C. beam propertiesExtensive MC simulations of event rate on detector bars for variousbeam properties at target (position, angle, size, energy…) e.g.:
June 23, 2009 PAVI09 S. Page, Univ. Manitoba 10
Parameter Max. DC value Max. run-averaged Max. noise during helicity-correlated value quartet spin cycle
(2544 hours) (8 ms)
Beam intensity 180 μA (150) AQ < 10-7 < 3 × 10-4
Beam energy ΔE / E ≤ 10-3 ΔE / E ≤ 10-9 ΔE / E ≤ 3 × 10-6
(Q2 measurement) 3.5 nm@35 mm/% 12 μm@35 mm/%
Beam position 2.5 mm <δx> < 2 nm 7 μm
Beam angle θ0= 60 μrad <δθ> < 30 nrad 100 μrad
Beam diameter 4 mm rastered <δσ> < 0.7 μm < 2 mm (~100 μm unrastered) (unrastered)
-- most requirements have been achieved for previous Jlab parity experiments.
Beam Property Requirements
June 23, 2009 PAVI09 S. Page, Univ. Manitoba 11
HC position change : ~1 HC position change : ~1 nanometers nanometers HC angle change: <1 HC angle change: <1 nanoradiannanoradianHC Energy change: <0.5 ppbHC Energy change: <0.5 ppb
R&D ongoing at Jlab and
UVa
Imperfections in laser spot or polarization
H.C. beam asymmetries
Studies in injector used to diagnose, fix problems:
Polarization transferLaser electrons:
Polarized Source
June 23, 2009 PAVI09 S. Page, Univ. Manitoba 12
• computational fluid dynamics used in design
• Additional safeguards: large raster size ~(4mm x 4mm), faster pump speed, and more cooling directed onto windows....
• Faster helicity reversal: 125 - 500 Hz to minimize noise
LH2 Target
Target cell
beam
H2 flow
Motor with Cryo bearings LH2 Pump
June 23, 2009 PAVI09 S. Page, Univ. Manitoba 13
Downstream:8 detectors@ θ ~ 0.55°• 100 GHz / det• null asymmetry monitor
Upstream: 4 detectors @ θ ~ 5°• 130 GHz / detector• mainly detects Moller e-• target density monitor• insensitive to beam angle, energy changes
Qweak luminosity monitors
Luminosity monitors:• current mode operation• higher rates than main detectors• quartz Cerenkov, air light guides
June 23, 2009 PAVI09 S. Page, Univ. Manitoba 14
QTOR Magnet• open geometry toroid: ΔΩ = 37 msr, Δφ = 49% of 2π• water cooled, iron-free, precision field-mapped
June 23, 2009 PAVI09 S. Page, Univ. Manitoba 15
Triple Collimation system defines acceptance
# 1
*** #2 ***
#3
June 23, 2009 PAVI09 S. Page, Univ. Manitoba 16
900 MHz e- per bar
Current mode readout (Ia = 6 μA)
Elastic focus – blue Inelastics - redToroidal Spectrometer Produces 8 Beam Spots
Each focus is ~2 meters long
Main Detector – elastic electron image on quartz bars
June 23, 2009 PAVI09 S. Page, Univ. Manitoba 17
Light Output Uniformity
Current Mode electronics and tests
Current mode readout with low noise I-VPreamp and 18 bit integrating ADC.ADC. Electronics test with DAQ:Preamp noise << counting statistics
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Distribution of events on a detector bar
How much light is produced for a given Q2?
Q2
(GeV
2)
June 23, 2009 PAVI09 S. Page, Univ. Manitoba 19
Simulated `light-weighted Q2 distribution’
We have to measure this ! Hence, the Qweak tracking system….
June 23, 2009 PAVI09 S. Page, Univ. Manitoba 20
Q2 Acceptance and efficiency measurements
Slide courtesy J. Mammei
June 23, 2009 PAVI09 S. Page, Univ. Manitoba 21
Region I: GEM detectors• high rate capability, excellent resolution• sense area matched to collimator 1 aperture• rotator assembly to map all octants
June 23, 2009 PAVI09 S. Page, Univ. Manitoba 22
Region II: HDC’s
• Pairs of 6-layer Horizontal Drift Chambers per tracking octant • x, x’, u, u’, v, v’ 1192 electronic channels F1TDC readout• Rotator assembly to map all octants
June 23, 2009 PAVI09 S. Page, Univ. Manitoba 23
Region III: VDC’s
• two per octant, with rotator ass’y•280 wires / plane • these things are huge!!!
Beam is kicked on / off a 1 μm Fe foil for good real/random ratio, low duty factor to minimize heating/depolarization.
Moller polarimetry at higher beam current:
Goal: ±1% absolute
June 23, 2009 PAVI09 S. Page, Univ. Manitoba 25
Compton Polarimeter
• continuous high current polarimeter• electron (diamond strip) and
photon (CsI) detection
k’ (scattered photon)
Az
Compt
on E
dge
Zero crossing
June 23, 2009 PAVI09 S. Page, Univ. Manitoba 26
Diamond strip electron detectors• More rad-hard than silicon• Multistrip planes, 200 μm pitch (8, need 4)
Large area prototype test with source: 9000 ehp
20 x 20 mm2 @ inner edge ~ 5mm from beam
Sourcetest
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Schedule and critical dates:
Installation begins October, 2009Commissioning/Engineering run begins May, 2010Production running beamtime begins Nov., 2010Beamtime end = 12 GeV shutdown in May, 2012
Anticipated results
June 23, 2009 PAVI09 S. Page, Univ. Manitoba 28
The Science: proton weak chargein the Standard Model
Qwn = -10Neutron
udd
-2C1d = -1 + 4/3 sin2θW-1/3d
Qwp = 1 - 4 sin2θW ≈ 0.07
-2C1u = + 1 – 8/3 sin2θW
Weak (vector)
+1Protonuud
+2/3u
ElectricCharge
Particle
Constraints on Standard Model C1q ‘sand effective couplings for non-SM extensions
29
All Data & Fits Plotted at 1 σ
Isovector weak charge
Isos
cala
rwea
k ch
arge
Standard ModelPrediction
Young, Carlini, Thomas & Roche, PRL
HAPPEx: H, HeG0 (forward): H, PVA4: HSAMPLE: H, D
30
All Data & Fits Plotted at 1 σ
Isovector weak charge
Isos
cala
rwea
k ch
arge
Standard ModelPrediction
Young, Carlini, Thomas & Roche, PRL
HAPPEx: H, HeG0 (forward): H, PVA4: HSAMPLE: H, D
June 23, 2009 PAVI09 S. Page, Univ. Manitoba 31
Model-independent search for new physics:
New physics term:
J. Erler et al., Phys. Rev. D 68, 016006, 2003
QpWeak projected 4% (2200 hours production)
QpWeak projected 8% (14 days production)
SLAC E158, Cs APV
FermiLab Run II projectedFermiLab Run I
4
3
2
1
00 2 4 6 8 10 12
ΔQpWeak/ Qp
Weak (%)
Mass Sensit ivit y vs ΔQpWeak/ Qp
Weak
68% CL
95% CL
Λ/g
(TeV
)At 95% CL,
June 23, 2009 PAVI09 S. Page, Univ. Manitoba 32
http://lepewwg.web.cern.ch/LEPEWWG
single bestZ-polemeasurementsdo notagree witheach other!
Comparison to Z-pole data for sin2θW
Qweak ± 0.00072
12 GeV Moller Next talk !
June 23, 2009 PAVI09 S. Page, Univ. Manitoba 33
EXTRA SLIDES
34
Estimates of 2 Boson Exchange effects on APV at Qweak KinematicsTPE (Blunden et.al.) -0.05%
TBE (Tjon, Blunden, Melnitchouk) 0.13% (N and Δ) arXiv:0903.2759
TBE (Gorchtein & Horowitz) ~ 6% (dispersion relations)Phys. Rev. Lett. 102, 091806 (2009)
New calculation underway emphasizing estimating the uncertainties on high energy terms - Alex Sibirtsev, et al.
Source QpWeak Uncertainty
Δ sin θW (MZ) ±0.0006Zγ box ±0.0005Δ sin θW (Q)hadronic ±0.0003WW, ZZ box - pQCD ±0.0001Charge symmetry 0
Total ±0.0008
Electroweak Radiative Corrections
Erler et al., PRD 68(2003)016006.
QpWeak Standard Model (Q2 = 0) 0.0713 ± 0.0008
QpWeak Global Fit Value (Young, et.al.) 0.055 ± 0.017
QpWeak Experiment anticipated uncertainty 0.0XXX ± 0.003
June 23, 2009 PAVI09 S. Page, Univ. Manitoba 35
Parameter Value
Incident Beam Energy 1.165 GeVBeam Polarization 85% Beam Current 180 μA LH2 Target Length 35 cm (0.04 X0) Production Running Time 2544 hours Nominal Scattering Angle 7.9 degScattering Angle Acceptance ±3 degAcceptance 49% of 2πSolid Angle ΔΩ = 37 msrAcceptance Averaged Q2 < Q2 > = 0.026 (GeV / c)2
Acceptance Averaged Physics Asymmetry < A > = -0.234 ppmAcceptance Averaged Expt'l Asymmetry < A > = -0.200 ppmIntegrated Cross Section 4.0 μb Integrated Rate (all sectors) 6.5 GHz (.81 GHz per sector)
Details of operationProduction data taking in current mode