Qweak Installation:May 2010-May 2012

~1 year of beam in 3running periods:

Run 0 : Jan – Feb 2011 (published)

Run 1: Feb – May 2011 (my dissertation)

Run 2: Nov 2011 – May 2012

06/02/2015

Determination of the Weak Charge of the ProtonThrough Parity Violating Asymmetry Measurements in the

Elastic e+p Scattering

Adesh Subedi

Thesis Prize Talk – UGM 2015

Outline

o Physics motivation

o The QWeak apparatus

o My contributions to the experiment

Hardware: target

Monte-Carlo simulations: energy sensitivity, inelastic dilution

factor, electromagnetic radiative correction

Blinded Run 1 data analysis (thesis result); about 1/3 of total data

o Extraction of the weak charge of the proton

o Summary

2

EW Parity violating

EM Parity conserving

+

Weak charge is the neutral weak analog of electromagnetic charge

𝐴𝑃𝑉𝑒𝑝

=𝜎𝑅−𝜎𝐿

𝜎𝑅+𝜎𝐿 ~

𝑀𝑊𝑒𝑎𝑘𝑃𝑉

|Μ𝐸𝑀 | ∝

𝑄2

𝑀𝑍

𝐴𝑃𝑉𝑒𝑝

= 𝐺𝐹𝑄2

4𝜋𝛼 2

𝜖𝐺𝐸𝛾𝐺𝐸

𝑍+𝜏𝐺𝑀𝛾𝐺𝑀

𝑍 − 1−4sin 2𝜃𝑤 𝜖 ′ 𝐺𝑀𝛾𝐺𝐴

𝑍

𝜖 𝐺𝐸𝛾

2 + 𝜏 𝐺𝑀

𝛾

2

𝑤𝑕𝑒𝑟𝑒 𝐺𝐸,𝑀𝛾

𝑎𝑟𝑒 𝐸𝑀 𝐹𝐹𝑠 𝑎𝑛𝑑 𝐺𝐸,𝑀𝑍 & 𝐺𝐴

𝑍 𝑎𝑟𝑒 𝑛𝑒𝑢𝑡𝑟𝑎𝑙 𝑤𝑒𝑎𝑘 𝐹𝐹𝑠

𝑠𝑖𝑛2𝜃𝑤 = 1 − 𝑀𝑊

𝑀𝑧

2

= 𝑤𝑒𝑎𝑘 𝑚𝑖𝑥𝑖𝑛𝑔 𝑎𝑛𝑔𝑙𝑒 𝑎𝑛𝑑

𝜏 =𝑄2

4𝑀2, 𝜖 = [1 + 2 1 + 𝜏 tan2

𝜃

2 −1

, 𝜖 ′ = 𝜏 1 + 𝜏 1 − 𝜖2

𝐴𝑃𝑉𝑒𝑝

= −𝐺𝐹𝑄2

4𝜋𝛼 2 𝑄𝑊

𝑃 + 𝑄2𝐵 𝑄2 , 𝜃 when 𝜃~0, 𝜖 ~ 1 & 𝜏<<1

The world PVES data → 𝐵 𝑄2 , 𝜃

𝑨𝑷𝑽𝒆𝒑

, 𝑸𝟐, 𝑩 𝑸𝟐, 𝜽 → 𝑸𝒑𝒘

𝑸𝑾𝒑

→ 𝑪𝟏𝒖, 𝑪𝟏𝒅 & 𝐬𝐢𝐧𝟐 𝜽𝒘. 𝑪𝟏𝒖, 𝑪𝟏𝒅 → 𝑸𝑾𝒏

Parity Violating Asymmetry

when Q2<<MZ

3

Weak charge of the proton( )

𝑸𝑾𝒑

𝑸𝑾𝒑

𝑸𝑾𝒏

= -2 (2C1u + C1d)

= -2 (C1u + 2C1d)

In general, Qw(Z,N) = -2{C1u(2Z+N) + C1d(Z+2N)}

The Qweak experiment proposed 4% determination of A 0.3% extraction of sin2θw: most precise at low Q2

High-precision extraction of both C1u, C1d, in combination with APV data

𝑄𝑊𝑝

(Enhanced TeV-scale sensitivity to signatures of BSM physics)

4

Experimental Apparatus

LH2 target

Parameters:Ibeam = 180 μAEbeam= 1.160 GeVθ = 6° - 12°Integrated rate = 6.4 GHzBeam Polarization = 88%Target = 34.5 cm LH2

Cryopower = 3 kW

Beam

Collimators

Qweak ToroidalMagnetic Spectrometer (QTor)

Horizontal Drift Chambers

Quartz Cherenkov bars

Downstream Luminosity Monitors

Shield Hut

Used only during low current tracking mode operation

Vertical Drift Chambers

Trigger Scintillators

GOAL: 6 ppb measurement of APV

ep (-234 ppb)

5

PVES Asymmetryo Parity transformation is equivalent to helicity reversal

o Pseudo random quartet ordering frequency ~ 1 kHz

o Asymmetry formed by a quartet (4 ms) A = + B

o Statistical power is ΔA = σquartet/√N = 226 ppm/ √N

where N is the number of quartets

Detector signal integrated in each helicity window

226 ppmper quartet

Blinded asymmetry 6

Qweak Target Loop

Centrifugal pump(15 l/s, 7.6 kPa)

3 kW Heater

3 kW HX utilizing4K & 14K He coolant

35 cm cell (beam interaction volume)

Solid Tgts

Coolant IN

Coolant OUT

Beam

o World’s highest power cryogenic target ~2.2 kW of beam power

o Designed with computational fluid dynamics (CFD) to reduce density fluctuations

7

Nominal running point

Target Performance

Time (sec)

Time (sec)

Pump speed = 28.5 Hz

From 3 independent ways, tgt. noise at 960 Hz reversal rate , 180 μA beam , 4x4 mm2

raster <50 ppm

Very small contribution to the total measured quartet asymmetry width (226 ppm)

Pump speed = 12 Hz

Mai

n D

ete

cto

r Y

ield

(V

/μA

)

4x4 mm2 raster 169 μA beam current

8

Effect of Sub-cooling

o Pump speed scan at various loop temperatures

o Nominal : 20 K, 35 psi

o Tgt. Noise highly suppressed by sub-cooling of LH2

180 μA4 x 4 mm2

Important for future experiments!!!

9

Did reversal at higher frequency help?

Fast Fourier Transforms of Main Detector Yield show tgt. noise at smaller frequencies

20 μA3 x 3 mm2

180 μA4 x 4 mm2

10

Did reversal at higher frequency help?

A480 Hz(quartet) =)3+2(+)4+1(

)3+2()4+1(

yyyy

yyyy - A480 Hz(pair) =)4+3(+)2+1(

)4+3()2+1(

yyyy

yyyy -

)8+7+6+5(+)4+3+2+1(

)8+7+6+5()4+3+2+1(

yyyyyyyy

yyyyyyyy -A240 Hz(pair) =A240 Hz(quartet) =

)6+5+4+3(+)8+7+2+1(

)6+5+4+3()8+7+2+1(

yyyyyyyy

yyyyyyyy -

+ - - + - + + -

y1 y2 y3 y4 y5 y6 y7 y8

MPS at 960 Hz helicity reversal

Normalized detector yield

o MPSes can be reordered to mimic helicity reversal frequencieso Two ways or reordering : Quartet and Pair

and so on…

o Mimicked asymmetry is not physical !!o BUT, asymmetry width is all we needo Calculate asymmetry widths at various mimicked helicity reversal

frequencies o Fit to extract tgt. noise 11

Did reversal at higher frequency help?28.5 Hz pump speed 4x4 mm2 raster169 μA beam current

o Boiling width ∝ (f)-0.4

o Quartet ordering suppresses noise better than pairwise ordering

o Tradeoff: increased dead time associated with faster helicity reversal

Important for future experiments!!!

12

Data Analysis

13

Removal of false Asymmetrieso Changes in helicity correlated beam properties create false asymmetries

o We identified, minimized & corrected for such helicity correlated false asymmetries

o where χ =X and Y angles and positions, Energy and Charge

o ∂A/∂χi determined by linear regression on natural beam motion (my dissertation) or driven motion

o Regression corrections applied at the quartet level

14

Linear Regression: Residual Correlations

Define residual asymmetry as, Aresidual = A - sign* <APV>

Found to be zero at the quartet level

Significant, non zero residual correlations at slug (~ 8 hrs) level

X’ most significant

Do a simple X’ correction (happily, highly correlated with X, Y, Y’ & E!)

- Cancels most slopes except for Q

Do another simple correction for Q

15

Two step post-regression correction at slug level:X’ and then on Q

Zero correlations within the error bars

Note: A complete post-regression would null these

Linear Regression: Residual Correlations

16

Regression( <IN> + <OUT>)/2

(ppb)Post regression

<IN> + <OUT>)/2 (ppb)Regression

<IN,- OUT> (ppb)Post regression

<IN, -OUT> (ppb)Wiens(~month) Mean Error Mean Error Mean Error χ2/dof Mean Error χ2/dof

1 -77.0 28.3 -52.2 28.3 -277.1 27.8 1.8 -271.5 27.8 1.7

2 10.8 24.0 12.3 24.0 -238.2 24.0 1.2 -218.7 24.0 1.0

3 -27.6 25.6 -24.8 25.6 -222.3 25.6 1.4 -202.7 25.6 1.3

4 -59.7 26.9 -22.2 26.9 -253.1 26.9 2.0 -229.0 26.9 2.0

5 -149.4 25.5 -22.4 25.5 -179.0 25.2 2.8 -187.0 25.2 0.5

Run 1 -58.1 11.6 -19.8 11.6 -232.0 11.5 2.0 -219.8 11.5 1.4

Linear Regression: Post-regression

After post-regression correction- (<IN> + <OUT> )/2 zero within 2 sigma. Was ~5 sigma away before!- <IN,-OUT> Chi2/dof improved for Wiens 2 and 5 and Run 1 overall - Other corrections to follow

Δ (<IN> + <OUT>)/2 = 38.3 ppb (3.3σ shift) Δ <IN,- OUT> = 12.2 ppb (1σ shift)

Null asymmetry Blinded Physics asymmetry

Note : blinded asymmetry

17

Extraction of Physics Asymmetry

o Corrections to the raw asymmetry done in two levels

o Level I : corrections that affect χ2/dof of data- Linear regression, post-regression,

negligible transverse leakage and non-linearity correction Amsr= Araw +Areg + AT +Anon-lin

- Beamline background subtraction- Normalization by beam

polarization

o Level II: corrections that do not affect χ2/dof of data- Subtraction of other backgrounds- Experimental bias correction

18

Extraction of Physics Asymmetry

o Corrections to the raw asymmetry done in two levels

o Level I : corrections that affect χ2/dof of data- Linear regression, post-regression,

negligible transverse leakage and non-linearity correction Amsr= Araw +Areg + AT +Anon-lin

- Beamline background subtraction- Normalization by beam

polarization

o Level II: corrections that do not affect χ2/dof of data- Subtraction of other backgrounds- Experimental bias correction

Note : Blinded Asymmetry

19

Extraction of Physics Asymmetry

o Corrections to the raw asymmetry done in two levels

o Level I : corrections that affect χ2/dof of data- Linear regression, post-regression,

negligible transverse leakage and non-linearity correction Amsr= Araw +Areg + AT +Anon-lin

- Beamline background subtraction- Normalization by beam

polarization

o Level II: corrections that do not affect χ2/dof of data- Subtraction of other backgrounds- Experimental bias correction

Note : Blinded Asymmetry

20

Effective Kinematics determined from simulations

Acceptance averaged incident beam energyEs = 1.155 ± 0.003 (GeV)

Acceptance averaged < Q2 > = 0.0250 ± 0.0006 (GeV/c)2

Effective scattering angle, ϴeff = 7.90 ± 0.30o

From Run 1 data

Aep = -299.7 ± 13.4 (statistics) ± 17.2 (systematics) ± 68 (blinding) ppb

ResultsResults

21

Determination of the Weak Charge of the Proton

o Global fit of all PVES data on H, D, 4He up to Q2 = 0.63 (GeV/c)2

o Free fit parameters:- C1u, C1d

- ρs , μs

- iso-vector axial FF (GZA)

o All H data corrected for E and Q2

dependence of

o World PVES data constrain uncertainties of hadronicstructure in the B-term.

o is the intercept of the fit

o PVES data points extrapolated to ϴ = 0

𝑸𝑾𝒑

□γZ RC

22

Determination of the Weak Charge of the Proton

𝑸𝑾𝒑

Run 1 Blinding box range Weak charge of the proton

QpW (SM) = 0.0710 ± 0.0007

QpW (PVES) = 0.0870 ± 0.0085

Blinded Run 1 result

23

o Global fit of all PVES data on H, D, 4He up to Q2 = 0.63 (GeV/c)2

o Free fit parameters:- C1u, C1d

- ρs , μs

- iso-vector axial FF (GZA)

o All H data corrected for E and Q2

dependence of

o World PVES data constrain uncertainties of hadronicstructure in the B-term.

o is the intercept of the fit

o PVES data points extrapolated to ϴ = 0

□γZ RC

Determination of the Weak Vector Charges of the Quarks

o Combined with APV data on 133Cs

o C1 coefficients of light quarks C1u = -0.1940 ± 0.0039 C1d = 0.3448 ± 0.0038

oQW(Z,N) = -2{C1u(2Z+N) + C1d(Z+2N)}

oWeak charge of the proton Qn

W (PVES+APV) = 0.0865 ± 0.0085

o Weak charge of the neutron Qn

W (PVES+APV) = -0.9910 ± 0.0081 Qn

W (SM) = -0.9890 ± 0.0007 PVES data including Qweak

Combined fit

SM value

Note: Qweak measurement blinding box not included

Blinded Run 1 result

24

Running of Weak mixing Angle

SM prediction of running of the weak mixing angle

The full Qweak measurement will offer the most precise determination below the Z-pole

Run 1 Blinding box range 25

Implications of the Qweak experiment

o Sensitive to potential new parity-violating physics that couples

to electrons/quarks

o Assume agreement with the Standard Model within ΔQpW

Our model-independent mass reach is given by

Λ/g ≡ (2√2 GF ΔQpW)-0.5 ≥ 2.0 TeV

This mass reach is for 2σ (95% confidence limit)

To set exact mass limits, one must choose a model (a value for the

coupling)

26

Summary

o Final Qweak measurement will test the Standard Model

o Least noise achieved from the highest power cryogenic liquid hydrogen target. Encouraging for future experiments

o Blinded Run 1 statistical analysis result reported in my thesis. Efforts ongoing to finalize analysis

o Final Qweak results expected soon!

27

The Qweak Collaboration

D. Androic,1 D.S. Armstrong,2 A. Asaturyan,3 T. Averett,2 J. Balewski,4 J. Beaufait,5 R.S. Beminiwattha,6 J. Benesch,5

F. Benmokhtar,7 J. Birchall,8 R.D. Carlini,5, 2 G.D. Cates,9 J.C. Cornejo,2 S. Covrig,5 M.M. Dalton,9 C.A. Davis,10 W. Deconinck,2

J. Diefenbach,11 J.F. Dowd,2 J.A. Dunne,12 D. Dutta,12 W.S. Duvall,13 M. Elaasar,14 W.R. Falk,8 J.M. Finn,2, T. Forest,15, 16 D. Gaskell,5

M.T.W. Gericke,8 J. Grames,5 V.M. Gray,2 K. Grimm,16, 2 F. Guo,4 J.R. Hoskins,2 K. Johnston,16 D. Jones,9 M. Jones,5 R. Jones,17

M. Kargiantoulakis,9 P.M. King,6 E. Korkmaz,18 S. Kowalski,4 J. Leacock,13 J. Leckey,2, A.R. Lee,13 J.H. Lee,6, 2, L. Lee,10

S. MacEwan,8 D. Mack,5 J.A. Magee,2 R. Mahurin,8 J. Mammei,13, J.W. Martin,19 M.J. McHugh,20 D. Meekins,5 J. Mei,5 R. Michaels,5

A. Micherdzinska,20 A. Mkrtchyan,3 H. Mkrtchyan,3 N. Morgan,13 K.E. Myers,20 A. Narayan,12 L.Z. Ndukum,12 V. Nelyubin,9

Nuruzzaman,11, 12 W.T.H van Oers,10, 8 A.K. Opper,20 S.A. Page,8 J. Pan,8 K.D. Paschke,9 S.K. Phillips,21 M.L. Pitt,13 M. Poelker,5

J.F. Rajotte,4 W.D. Ramsay,10, 8 J. Roche,6 B. Sawatzky,5 T. Seva,1 M.H. Shabestari,12 R. Silwal,9 N. Simicevic,16 G.R. Smith,5

P. Solvignon,5 D.T. Spayde,22 A. Subedi,12 R. Subedi,20 R. Suleiman,5 V. Tadevosyan,3 W.A. Tobias,9 V. Tvaskis,19, 8

B. Waidyawansa,6 P. Wang,8 S.P. Wells,16S.A. Wood,5 S. Yang,2 R.D. Young,23 and S. Zhamkochyan 3

Spokespersons Project Manager Grad Students

97 collaborators 23 grad students

10 post docs 23 institutions

Institutions:1 University of Zagreb2 College of William and Mary3 A. I. Alikhanyan National Science Laboratory 4 Massachusetts Institute of Technology5 Thomas Jefferson National Accelerator

Facility6 Ohio University7 Christopher Newport University8 University of Manitoba,9 University of Virginia10 TRIUMF11 Hampton University12 Mississippi State University13 Virginia Polytechnic Institute & State Univ14 Southern University at New Orleans15 Idaho State University16 Louisiana Tech University17 University of Connecticut18 University of Northern British Columbia 19 University of Winnipeg20 George Washington University21 University of New Hampshire22 Hendrix College, Conway23 University of Adelaide

28

Thank You !

29

Supplemental Slides

30

The Standard Model

Three types of particles

o U(1)ϒ x SU(2)L x SU(3)c o Quarks : strongly interacting (QCD)o Leptons: weakly interacting (EW)o Bosons: force mediation

- Higgs boson to generate mass

However, does not include:

o Gravityo Neutrino oscillationso Dark matter & dark energy

Standard Model: Effective low energy theory

31

Testing the Standard Model

High energy frontier Precision (Intensity) frontier

Direct search of new particles Highest energies Low signature events

Indirect search of new particles Low-modest energies High signature events

KATRIN

Qweak

32

Electron-proton scattering

(E,p)S(-)

…………………………………………………..ϴ

Electron Proton

Energy transfer ν = E-E’3-momemtum transfer q= p-p’4 momentum transfer Q2 ≡ - q2 = - (ν2 - q2) ≥ 0If M is the mass of proton then for elastic scattering,

(E’,p’)

S(+)

33

Continuous Electron Beam Accelerator Facility (CEBAF)

34

Polarized Source

8 hourreversal

960 Hzreversal

monthlyreversal

35

Qweak required ΔP/P ≤ 1%

Strategy: use 2 independent polarimeters

• Use new Compton polarimeter (1%/h)• High Ibeam, non-invasive • Known analyzing power provided

by circularly-polarized laser

• Use existing <1% Hall C Møller polarimeter: • Low beam currents, invasive• Known analyzing power provided by

polarized Fe foil in a 3.5 T field.

Møller Polarimeter

Compton Polarimeter

Compton Moller

Preliminary

Precision Polarimetry

Diamond strip e-det

Achieved 0.61% !

36

Target DesignWorld’s highest power

and lowest noisecryogenic target ~3 kW

IBeam = 180 uAL = 35 cm (4% X0)Pbeam = 2.2 kWAspot = 4x4 mm2

V = 57 litersT = 20.00 KP ~ 220 kPa

Centrifugal pump(17 l/s, 7.6 kPa, 3-7 m/s)

3 kW Heater

3 kW HX utilizing4K & 14K He coolant

35 cm cell (beam interaction volume)

Solid Tgtsbeam

Electron Beam180 μA, 4x4 mm2

Designed using CFD

37

QTOR Magnet• Manitoba / TRIUMF / MIT-Bates / JLab• Open geometry resistive toroid, for maximum solid angle acceptance• Eight water cooled, dble pancake coils•Separates elastics from inelastics at focus

3-axis Mapper

Power Supply:150 V, 9100 A

38

Quartz Cerenkov Detectors

Yield 100 pe’s/track with 2 cm Pb pre-radiatorsResolution (~10%) limited by shower fluctuations.

Simulation of MD face:

Measured

Azimuthal directionR

adia

ld

irec

tio

n

Azimuthal symmetry maximizes rate and decreases sensitivity to HC beam motion, transverse asymmetry.

Spectrosil 2000 (fused silica) Cerenkov radiators: • Eight bars, each 2 m long, 18 cm hi, 1.25 cm thick• Rad-hard. non-scintillating, low-luminescence

Quartz Bars

Azimuthal direction

Rad

ial

dir

ecti

on

Scanner39

Neutral line-of-sight Collimation

14.9 mm φ, ±0.88⁰47 cm ds of tgt1.6 kW beam power

Beam Collimator:

40

Determining the KinematicsRequired uncertainty on Q2 is 0.5% Combination of tracking and simulation

• HDCs before magnet to msr θ– Q2 = 2E2 (1-cosθ) / [1 + E/M(1-cosθ)]

• VDCs & trigger scintillators after magnet to msr light weighted Q2

across quartz bars

radial

azim

uth

al

41

Beam parameter correctionsAreg = -35 ± 11 ppb

Areg = -¶A

¶c ii=1

5

å Dc iBeam Property

Modulation Amplitude

Msrd Δχi

(monthly)Msrd ∂A/∂Δχi

(monthly)

X ± 125 μm -3.3 nm -2.11 ppm/μm

Y ± 125 μm 2.5 nm 0.24 ppm/μm

X′ ± 5 μrad -0.7 nrad 100.2 ppm/μrad

Y′ ± 5 μrad 0.02 nrad 0.0 ppm/μrad

E± 61 ppm(70 keV)

0.1 nm -1.56 ppm/μm

Avg gives net correction, suppressed by symmetry

Both Driven and Natural beam

motion used to determine detector

sensitivities

1

3

5

7

∂A

/∂X

(p

pm

/mm

)

∂A/∂Y

1 2 3 4 5 6 7 8 Bar #1 2 3 4 5 6 7 8 Bar #

∂A

/∂Y

(pp

m/m

m)

can

cels

X

Y

∂A/∂X

Run 2 (77%) Uncorrected Asymmetries

42

𝑨𝒎𝒔𝒓𝒃𝒍𝒊𝒏𝒅𝒆𝒅 = 1 − 𝑓𝐵𝐵 − Σi=1

3 𝐟𝐢 𝑃𝐴𝑃𝑉𝑒𝑝

+ 𝐶𝑀𝐷𝑈𝑆 < 𝐴𝑈𝑆 > + 𝑃𝑓𝐴𝑙𝐴𝐴𝑙 + 𝑃𝑓𝑛𝑒𝑢𝑡𝑟𝑎𝑙 𝐴𝑛𝑒𝑢𝑡𝑟𝑎𝑙

+ 𝑃𝑓𝑖𝑛𝑒𝑙𝑎𝑠𝑡𝑖𝑐 𝐴𝑖𝑛𝑒𝑙𝑎𝑠𝑡𝑖𝑐 + 𝐵𝑜𝑓𝑓𝑠𝑒𝑡

𝐴𝑃𝑉𝑒𝑝

= 𝑅𝑇𝑜𝑡𝑎𝑙

𝑨𝒎𝒔𝒓 −𝑪𝑴𝑫

𝑼𝑺<𝐴𝑼𝑺>

𝑷 − Σi=1

3 𝐟𝐢𝐀𝐢

1− 𝑓𝐵𝐵 − Σ𝐟𝐢

Amsr = measured asym.APV

ep = physics asym.P = beam polarizationBB = beamline bkgd.fi = bkgd. fractionsAi = bkgd. asymmetriesi = Al, neutral & inelastic

RTotal = RQ2RRCRDetRBin

Methodology

Assuming Boffset = 0 for this analysis

= US lumi- MD correlation factor

<AUS> = average US lumi asym.

43

Wien

0Wien

0

Wien

0

Wien

0Wien

0

Wien

0Wien

0

Wien

0

Wien

0

Wien

0

13.4

ppb

8.0

ppb7.5

ppb

9

ppb

Dominant errors:

Al asym.

Q2

Post-regression

BB correction slope (C_MD^US)

Polarization

Al dilutionProposed final precision

18.6

ppb

Many numbers from Wien 0Many to-be-updated errors are likely much smallerHow to reduce errors on post-regression and CMD

US?

5.7

ppb 4.5

ppb

8.5

ppb

22.9

ppb

Status

Data Quality: Beam Parameter Differences

Run 1 helicity correlated beam parameter differences survey

Degradation of parity quality in Wiens 4 & 5 (a golden opportunity to test linear regression reliability)

45

0 0.0025 0.005 0.0075

Electroweak Corrections

~7% correction

Q2 DependenceE Dependence

• Calculations are primarily dispersion theory type

• error estimates can be firmed up with data!

• Qweak: inelastic asymmetry data taken at W ~ 2.3 GeV, Q2 = 0.09 GeV2

γZ

Hall, Blunden, Melnitchouk, Thomas & Young 0.0054 ± 0.0004arXiv:1504.03973 (2015)

Re VγZ corr. to QW(p)

46

Tree Level Gymnastics

(Eq. 2 from paper)

AQweak AHadronic AAxial

~0 ~0

=1

47