The science • The experiment • Status & milestonesweb.mit.edu/pavi09/talks/Page-Qweak.pdf · • The science • The experiment • Status & milestones With thanks to: • PAVI09

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 !


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.


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:


Extrapolation of Higher Q2 PV Data

Q2 (GeV2)


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


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


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⎡ ⎤+⎣ ⎦


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%.


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.:


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


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


• 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


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


QTOR Magnet• open geometry toroid: ΔΩ = 37 msr, Δφ = 49% of 2π• water cooled, iron-free, precision field-mapped


Triple Collimation system defines acceptance

# 1

*** #2 ***

#3


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


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


Distribution of events on a detector bar

How much light is produced for a given Q2?

Q2

(GeV

2)


Simulated `light-weighted Q2 distribution’

We have to measure this ! Hence, the Qweak tracking system….


Q2 Acceptance and efficiency measurements

Slide courtesy J. Mammei


Region I: GEM detectors• high rate capability, excellent resolution• sense area matched to collimator 1 aperture• rotator assembly to map all octants


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


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


Compton Polarimeter

• continuous high current polarimeter• electron (diamond strip) and

photon (CsI) detection

k’ (scattered photon)

Az

Compt

on E

dge

Zero crossing


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


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


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


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,


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 !


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


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

Documents

The science • The experiment • Status & milestonesweb.mit.edu/pavi09/talks/Page-Qweak.pdf · • The science • The experiment • Status & milestones With thanks to: • PAVI09