A.K. Opper June 2004 The Q p Weak Experiment: “A Search for New Physics at the TeV Scale Via a Measurement of the Proton’s Weak Charge” 63 People at: JLab,

A.K. Opper June 2004

The QpWeak Experiment:

“A Search for New Physics at the TeV Scale Via a Measurement of the Proton’s Weak Charge”

63 People at:

JLab, LANL, MIT, BATES, TRIUMF, William & Mary, Univ. of Manitoba, Virginia Tech, Louisiana Tech, Caltech, Univ. of Connecticut, Univ. Nacional Autonoma de Mexico, UNBC, Univ. of New Hampshire, Ohio Univ., Mississippi State, Hampton Univ., Yerevan Physics Institute

May 2000 Collaboration formedJanuary 2002JLab Proposal Approved with ‘A’ ratingJanuary 2003Technical design review complete2003 All needed funding secured DOE/JLab, NSF & NSERC2004 Design work and prototyping2007 Goal for initial experiment installation.

• 1st measurement of Qpw

• 10 measurement of sin2W running


• Standard model predicts sin2 w(Q)

• ALR QpW

= 1 – 4 sinW

• Complements APV and high energy measurements

• Tests consistency of SM and probes for new physics

10001001010.10.010.0010.225

0.23

0.235

0.24

0.245

0.25

Weak Mixing AngleScale dependence in MS-bar scheme

Uncertainties shown include statistical and systematic

NuTeV

QW (APV)

Z-pole

MSSM

SMSemi-Leptonic Sector (proposed)

Pure Leptonic Sector

Semi-Leptonic Sector (published)

Qweak(4% Qp

Weak)E-158

QeWeak

Anticipated Final Errors

E-158 Runs I + II(Preliminary)

(Moves aroundevery year or so!)

0.3% sin2W

Interfere Z0

Q(GeV/c)


072.0~sin41Q 2W

pweak (at tree level)

A 2MNC

MEM

GF

4 2

Q2 Qweakp F p Q2 ,

Q2 0 0

GF

4 2

Q2 Qweakp Q4B Q2

ZMEME GG ,, and contains

QpWeak : Extract from PV Electron Scattering

measures Qp EM - PC measures Qp

Weak - PV

MEM MNC

• Qpweak is a well-defined experimental observable

• Qpweak has a definite prediction in the electroweak Standard Model

Qeweak : electron’s weak charge is measured in PV Moller scattering (E158)

Interference helicity asymmetry, A,for polarized beam

A = = + - -

+ + -

______


Nucleon Structure Contributions to the Asymmetry

ppm 01. ppm 09. ppm 19.

Q

axialhadronic AAAA p

W

hadronic: (31% of asymmetry) - contains G

E,M GZE,M constrained

by HAPPEX, G0, MAMI PVA4

axial: (4% of asymmetry) - contains Ge

A, has large electroweak radiative corrections.

Will be constrained by G0 and SAMPLE

Expected constraintson Ahadronic from

currently running experiments

Quadrature sum of expected Ahadronic and Aaxial errors

contributes ~2% to error on QpW

---- Range of possible strange quark form factor contribution

Measure not calculate!

= -0.28 ppm


Le-q

PV LSMPV LNEW

PV GF

2e e C1qq q

q

g2

4e e hV

qq qq

Energy Scale of an “Indirect” Search for New Physics

• Parameterize New Physics contributions in electron-quark Lagrangian

• A 4% QpWeak measurement probes for new

physics at energy scales to:

g: coupling constant: mass scale

g

GF QW

p 4.6 TeV

•TeV discovery potential unmatched

until the LHC turns on


“Running of sin2W” in the Standard Model

At Q = 0.03 GeV/c: * Qp

weak (semi-leptonic) and * SLAC E158 (pure leptonic) * different sensitivities to SM extensions

Electroweak radiative corrections sin2W varies with Q

+ +

Erler et al., Phys. Rev D 68, 016006

10001001010.10.010.0010.225

0.23

0.235

0.24

0.245

0.25

Weak Mixing AngleScale dependence in MS-bar scheme

Uncertainties shown include statistical and systematic

NuTeV

QW (APV)

Z-pole

MSSM

SMSemi-Leptonic Sector (proposed)

Pure Leptonic Sector

Semi-Leptonic Sector (published)

Qweak(4% Qp

Weak)E-158

QeWeak

Anticipated Final Errors

E-158 Runs I + II(Preliminary)

(Moves aroundevery year or so!)

(Qpweak) = 4% (sin2W) = 0.3%


• Qpweak (semi-leptonic) and E158 (pure leptonic) together make a powerful

program to search for and identify new physics.

• Qweak measurement will provide a stringent stand alone constraint on Lepto-quark based extensions to the SM.

JLab Qweak SLAC E158

E158 Run I hep-ex/0312035 ± 0.012(projected final)

(proposed)

-


Illustration of the QpWeak Experiment

Incident beam energy: 1.165 GeVBeam Current: 180 μABeam Polarization: ~80%LH2 target power: 2.5 KW

Central scattering angle: 8° ±2Phi Acceptance: 50% of 2Average Q²: 0.028 GeV2

Acceptance averaged asymmetry: –0.28 ppmIntegrated Rate (all sectors): 5.2 GHz Integrated Rate (per detector): 650 MHz

Experiment Parameters(integration mode)

35 cm Liquid Hydrogen Target

Polarized Electron Beam

Collimator With Eight Openings = 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 3Drift Chambers

Region 2Drift Chambers

Region 1GEM Detectors

Polarized Electron Beam

35cm Liquid Hydrogen Target

Collimator with 8 openingsθ= 8° ± 2°

Region IGEM Detectors

Region IIDrift Chambers

Toroidal Magnet

Region IIIDrift Chambers

Elastically Scattered Electron

Eight Fused Silica (quartz)Čerenkov Detectors

Luminosity Monitors


Collimator Design

θ= 8°±2° (azimutal)φ= ±11° (polar, per octant)

Q²= 0.028 GeV²Rate = 650 MHz/octant

Kinematical acceptance:

Target

Collimator 1Defining aperture

Electron beam

Collimator 2(clean up)

Main TorusMagnet

Material: leaded brass (25% lead ,70% Cu, 5% Sn)

required survey accuracy: ~ 1 mrad

(~ 1 mm for alignment of precision

collimators with respect to target)

Shielding Wall


Qweak Toroidal Magnet

beam

scattered e envelope

•8 toroidal coils, 4.5m long along beam•Resistive, based on BLAST • Pb shielding between coils• Coil holders & frame all Al

• Bdl ~ 0.7 T-m• ~9500 A


Separated Inelastic & Photon Background

Inelastics

Elastic

Photons

• QpWeak spectrometer optics from GEANT simulation. Double collimator.

clean separation of elastics from inelastics & ’s at focal plane

At Detector(with Čerenkov cut): Elastic e-p rate = 650 MHz/octantInelastic rate = 30 KHz/octant Inelastic contamination ~ 0.005% Photon rate = 42 KHz/octant Photon contamination ~ 0.007%


View Along Beamline of QpWeak Apparatus with Simulated Events

Black region in center is Pb shielding


The Qpweak Detector and Electronics System

Focal plane detector requirements:

• Radiation hardness (expect > 300 kRad).• Insensitivity to background , n, . • Operation at counting statistics.

Electronics (LANL/TRIUMF/UMan design):

• Normally operates in integration mode.• Will have connection for pulse mode.• Low electronic noise contribution compared to counting statistics.• 1 MHz 16 bit ADC will allow for over sampling.

Op Amp

1 M 2 pF

Fiber Optic

Converter

15 V

1 MHz 16 bit ADC

110 VAC in Pulse mode in

10 k

PMT HV in

PMT anode

Fused Silica (synthetic quartz) Cerenkov detector

• Use 15 cm x 200 cm x 2.5 cm quartz bars read out at both ends by S20 photocathode PMTs (expect ~ 100 pe/event), 5 inch• n=1.47, Cerenkov= 47°

• total internal reflection tir=43°• reflectivity = 0.997


Position dependence of the # of pe’s on each of the PMTs.

Simulation includes the full weighted cross-section & spectrometer optics.

Light Collection in 12 cm x 2.54 cm x 2 m Quartz Cerenkov Detectors

Rotate Detector 12.5o

Length Width


Detector Performanceprototype sample tested in beam (G0)

• Alignment within a few degrees was critical

• In a quartz TIR detector the angle rather than position is the right variable.

• Top window: bar roughly perpendicular to beam

• Bottom Window: bar tilted 5 degrees to favor bottom PMT


The Qpweak 2200 Watt Liquid Hydrogen Target

Target:

• Similar in design to SAMPLE & G0 targets longitudinal liquid flow high stream velocity achieved with perforated, tapered “windsock”

QpWeak Target parameters/requirements:

• Length = 35 cm• Beam current = 180 A • Beam power = 2500 W • Raster size ~4 mm x ~4 mm square• Flow velocity > 700 cm/s• Density fluctuations (at 15 Hz) < 5x10-5

G0 target


G0 Target Cell & Manifold

cold helium gas

(dropped for Qweak)

(enlarged for Qweak)

perforated windsock/flow diverter

exit window(75 µ)


Determination of Average Q2

Need to know <Q2>/<Q2> ~ 0.7% requires survey accuracy ~ 1 mrad (~ 1 mm for alignment of precision collimator with respect to target)

Expected Q2 distribution

Calibration measurements at low beam current, event-by-event made with 1 set of GEMs and 2 sets of Drift Chambers to:

• Measure shape of focal plane distribution.• Measure position-dependent detector efficiency.• Compared measured Q2 distribution to Monte-Carlo


Measurement of the Signal-to-Background Dilution Factor

TOF Measurement: •Beam: 2 MHz pulse rate & low current• PMT anode 1 GHz transient digitizer TOF distribution of the anode current events of interest are in prompt peak

PMT Anode 1 GHz 8 bit transient digitizer

Decompose Prompt Peak: •Insert GEMs, drift chambers & scintillator.• Run at low beam current (“pulse mode”) in coincidence.• Scintillator allows for neutral rejection.• Tracking traces origin of scattered particles.

Pions Neutrons

Prompt:Elastic e-

+ 0 + brems.


Basel/Hall C Møller • Existing Hall C Møller can do 1%

(stat) in a few minutes• With care, absolute accuracy <1%

• Limitations- IMax ~ 10 A At higher currents the Fe target depolarizes.- Measurement is destructive

• Goals for an upgraded Møller-Measure Pbeam at 100 A or higher, quasi-continuously-Trick: kicker + strip or wire target (looks promising)

• Plus new HallC Compton polarimeter-Measure Pbeam at 100 A or higher, quasi-continuously


Anticipated Uncertainties on QpWeak

Qpweak/Qp

weak Possible Improvements

Statistical (2200 hours) 2.8% 2.5%Systematic:

Hadronic structure corrections 2.0% 1.5% Beam polarization 1.4% 1.0% Average Q2 determination 1.0% Helicity-correlated Beam Properties 0.6% Uncertainty in Inelastic contamination 0.2% Al Target window Background <1.0% 0.3% (Be)

Total systematic 2.9% 2.2%______________________________________________________________________Total 4.0% 3.3%

Bottom line:

Precision measurement of the running of sin2W requires effort but no new technology!

Additional uncertainty associated with QCD corrections (from extraction of sin2W): raises sin2W / sin2W from 0.2% to 0.3%.


Status Qweak: Summary

• Broad community performing precision measurements to test SM – including Qweak.

• Capital funding (NSF + university matching, JLAB, NSERC) secured JLab “infrastructure” - AC, DC, cooling water, installation manpower, recycle

G0 beamline systems....

• Magnet procurements during FY-04. Detector prototyping begun.

• On track for a ~3.5 year construction effort with possible installation in 2007.

• Strong scientific support for the measurement. Nuclear theory (Ramsey-Musolf, Erler, Haxton, Donnelly, Friar,…) and high

energy theory (W. Marciano & P. Lanacker).

• Collaboration healthy and growing -- addition of MIT/Bates Staff and the hiring of postdocs by a number of groups.

• Investigating possibility of better than a 4% measurement of Qweak.


Qweak Collaboration Spokespersons

Bowman, J. David - Los Alamos National LaboratoryCarlini, Roger (Principal Investigator) - Thomas Jefferson National Accelerator FacilityFinn, J. Michael - College of William and MaryKowalski, Stanley - Massachusetts Institute of TechnologyPage, Shelley - University of Manitoba

Qweak Collaboration Members

Armstrong, David - College of William and MaryAverett, Todd - College of William and MaryBirchall, James - University of ManitobaBotto, Tancredi - Massachusetts Institute of TechnologyBruell, Antje - Thomas Jefferson National Accelerator FacilityChattopadhyay, Swapan - Thomas Jefferson National Accelerator FacilityDavis, Charles - TRIUMFDoornbos, J. - TRIUMFDow, Karen - Massachusetts Institute of TechnologyDunne, James - Mississippi State UniversityEnt, Rolf - Thomas Jefferson National Accelerator FacilityErler, Jens - University of MexicoFalk, Willie - University of ManitobaFarkhondeh, Manouchehr - Massachusetts Institute of TechnologyForest, Tony - Louisiana Tech UniversityFranklin, Wilbur - Massachusetts Institute of TechnologyGaskell, David - Thomas Jefferson National Accelerator FacilityGrimm, Klaus - College of William and MaryHagner, Caren - Virginia Polytechnic Inst. & State Univ.Hersman, F. W. - University of New HampshireHoltrop, Maurik - University of New HampshireJohnston, Kathleen - Louisiana Tech UniversityJones, Richard - University of ConnecticutJoo, Kyungseon - University of Connecticut

Keppel, Cynthia - Hampton UniversityKhol, Michael - Massachusetts Institute of TechnologyKorkmaz, Elie - University of Northern British Columbia Lee, Lawrence - TRIUMFLiang, Yongguang - Ohio UniversityLung, Allison - Thomas Jefferson National Accelerator FacilityMack, David - Thomas Jefferson National Accelerator FacilityMajewski, Stanislaw - Thomas Jefferson National AcceleratorMammei, Juliette - Virginia Polytechnic Inst. & State Univ.Mammei, Russell - Virginia Polytechnic Inst. & State Univ.Mitchell, Gregory - Los Alamos National LaboratoryMkrtchyan, Hamlet - Yerevan Physics InstituteMorgan, Norman - Virginia Polytechnic Inst. & State Univ.Opper, Allena - Ohio UniversityPenttila, Seppo - Los Alamos National LaboratoryPitt, Mark - Virginia Polytechnic Inst. & State Univ.Poelker, B. (Matt) - Thomas Jefferson National Accelerator FacilityPorcelli, Tracy - University of Northern British ColumbiaRamsay, William - University of ManitobaRamsey-Musolf, Michael - California Institute of TechnologyRoche, Julie - Thomas Jefferson National Accelerator FacilitySimicevic, Neven - Louisiana Tech UniversitySmith, Gregory - Thomas Jefferson National Accelerator FacilitySmith, Timothy - Dartmouth CollegeSuleiman, Riad - Massachusetts Institute of TechnologyTaylor, Simon - Massachusetts Institute of TechnologyTsentalovich, Evgeni - Massachusetts Institute of Technologyvan Oers, W.T.H. - University of ManitobaWells, Steven - Louisiana Tech UniversityWilburn, W.S. - Los Alamos National LaboratoryWood, Stephen Thomas - Jefferson National Accelerator FacilityZhu, Hongguo - University of New HampshireZorn, Carl - Thomas Jefferson National Accelerator FacilityZwart, Townsend - Massachusetts Institute of Technology

JLab E02-020: “Qweak”

A Search for Physics at the TeV Scale via a Measurement of the Proton’s Weak Charge

Documents

A.K. Opper June 2004 The Q p Weak Experiment: “A Search for New Physics at the TeV Scale Via a Measurement of the Proton’s Weak Charge” 63 People at: JLab,