Acknowlegements: The E158, HAPPEX, PREX and MOLLER Collaborations www.particleadventure.org Electrons are Not Ambidextrous:

New Insights from a Subatomic Matter of Fact Krishna Kumar Stony Brook University, SUNY Physics Colloquium BNL, November 4, 2014 Electroweak Nuclear Physics Outline

✦ Electron Scattering & Subatomic Structure ✦ Electron Scattering and the Weak Force ★ Electrons in the scattering process are NOT ambidextrous ✦ Parity-Violating Electron Scattering ✦ Two Modern Applications ★ The Neutron Skin of a Heavy Nucleus

• PREX: First direct electroweak measurement (Phys.Rev.Lett. 108 (2012) 112502)! • PREX-II: Followup precision measurement scheduled for 2016! ★ Search for New Superweak Forces

• MOLLER: Proposed ultra-precise weak mixing angle measurement! ✦ Outlook Electrons are Not Ambidextrous 2 Krishna Kumar, November 4 2014 Electroweak Nuclear Physics Outline Fundamental Symmetries, Nuclear Structure, Hadron Physics ✦ Electron Scattering & Subatomic Structure ✦ Electron Scattering and the Weak Force ★ Electrons in the scattering process are NOT ambidextrous ✦ Parity-Violating Electron Scattering ✦ Two Modern Applications ★ The Neutron Skin of a Heavy Nucleus

• PREX: First direct electroweak measurement (Phys.Rev.Lett. 108 (2012) 112502)! • PREX-II: Followup precision measurement scheduled for 2016! ★ Search for New Superweak Forces

• MOLLER: Proposed ultra-precise weak mixing angle measurement! ✦ Outlook Electrons are Not Ambidextrous 2 Krishna Kumar, November 4 2014 Electron Scattering and the Subatomic Structure ~ 1910 Rutherford Scattering The first fixed target scattering experiment Rutherford devised a scattering experiment involving a beam of alpha particles scattering off a gold foil

differential cross section d ⌦ d ⇥ ✓ ◆ # alphas scattered into solid angle per unit time Incident beam intensity Electrons are Not Ambidextrous 4 Krishna Kumar, November 4 2014 ~ 1910 Rutherford Scattering The first fixed target scattering experiment Rutherford devised a scattering alpha particles & gold atom’s positive charge: experiment involving a beam of alpha interaction governed by Maxwell’s equations particles scattering off a gold foil d⇤ Z Z 2 = 1 2 d 2mv2 sin2(⇥/2) ✓ ◆ ✓ ◆

Atom’s positive charge: static differential cross section EM potential d ⌦ d ⇥ ✓ ◆ # alphas scattered into solid angle per unit time Incident beam intensity Electrons are Not Ambidextrous 4 Krishna Kumar, November 4 2014 ~ 1910 Rutherford Scattering The first fixed target scattering experiment Rutherford devised a scattering alpha particles & gold atom’s positive charge: experiment involving a beam of alpha interaction governed by Maxwell’s equations particles scattering off a gold foil d⇤ Z Z 2 = 1 2 d 2mv2 sin2(⇥/2) ✓ ◆ ✓ ◆

Atom’s positive charge: static differential cross section EM potential d ⌦ d ⇥ ✓ ◆ # alphas scattered into solid angle per unit time Incident beam intensity Electrons are Not Ambidextrous 4 Krishna Kumar, November 4 2014 ~ 1910 Rutherford Scattering The first fixed target scattering experiment Rutherford devised a scattering alpha particles & gold atom’s positive charge: experiment involving a beam of alpha interaction governed by Maxwell’s equations particles scattering off a gold foil d⇤ Z Z 2 = 1 2 d 2mv2 sin2(⇥/2) ✓ ◆ ✓ ◆

Atom’s positive charge: static differential cross section EM potential d ⌦ d ⇥ ✓ ◆ •Established that atoms have a tiny nuclear # alphas scattered into core ~ 10-14 m, << atomic size of 10-10 m solid angle per unit time •Revolutionized experimentation: particle Incident beam intensity scattering as a microscope Electrons are Not Ambidextrous 4 Krishna Kumar, November 4 2014 A femtoscope Electron Scattering

At nuclear scales, particles behave mostly like waves Particle How to produce femtometer Accelerators wavelengths in the laboratory?

Electrons are Not Ambidextrous 5 Krishna Kumar, November 4 2014 A femtoscope Electron Scattering Electron interactions are well-understood

At nuclear scales, particles behave mostly like waves Particle How to produce femtometer Accelerators wavelengths in the laboratory? Quantum Electrodynamics Dirac: relativistic motion of electrons with spin 1/2

Electron scattering: electromagnetic interaction E’ described as an exchange of a virtual photon. θ

E N

Electrons are Not Ambidextrous 5 Krishna Kumar, November 4 2014 A femtoscope Electron Scattering Electron interactions are well-understood

At nuclear scales, particles behave mostly like waves Particle How to produce femtometer Accelerators wavelengths in the laboratory? Quantum Electrodynamics Dirac: relativistic motion of electrons with spin 1/2

Electron scattering: electromagnetic interaction E’ described as an exchange of a virtual photon. θ Mott: spin 1/2 electrons

E scattering off infinitely N heavy point spinless nucleus

2 2 θ q2: (4-momentum)2 of the virtual photon q = −4EE # sin 2

Electrons are Not Ambidextrous 5 Krishna Kumar, November 4 2014 € A femtoscope Electron Scattering Electron interactions are well-understood

At nuclear scales, particles behave mostly like waves Particle How to produce femtometer Accelerators wavelengths in the laboratory? Quantum Electrodynamics Dirac: relativistic motion of electrons with spin 1/2

Electron scattering: electromagnetic interaction E’ described as an exchange of a virtual photon. θ Mott: spin 1/2 electrons

E scattering off infinitely N heavy point spinless nucleus

2 2 θ q2: (4-momentum)2 of the virtual photon q = −4EE # sin 2 Powerful technique: high statistics and precise event-by-event kinematic determination Electrons are Not Ambidextrous 5 Krishna Kumar, November 4 2014 € The Size of a Nucleus

e Heavy, spinless d⇥ 4Z22E2 e γ = nucleus d Mott q4 ⇥

Electrons are Not Ambidextrous 6 Krishna Kumar, November 4 2014 If Q sufficiently large (wavelength < 10 fm) , nuclear size modifies formula The Size of a Nucleus Increase momentum transfer -> shorter wavelength -> higher resoluon -> smaller scales e Heavy, spinless d⇥ 4Z22E2 e γ = 208Pb nucleus d Mott q4 ⇥ Differential Cross Section

d d 2 = F (q) d d ⇥ ⇤Mott

1 2 3 q (fm)-1 Electrons are Not Ambidextrous 6 Krishna Kumar, November 4 2014 If Q sufficiently large (wavelength < 10 fm) , nuclear size modifies formula The Size of a Nucleus Increase momentum transfer -> shorter wavelength -> higher resoluon -> smaller scales e Heavy, spinless d⇥ 4Z22E2 e γ = 208Pb nucleus d Mott q4 ⇥ Differential Cross Section

d d 2 = F (q) d d ⇥ ⇤Mott The point-like scaering probability modified: Introduce a “form factor”

F (q)= eiqr(r)d3r Form factor is the Fourier transform of 1 2 charge distribuon 3 q (fm)-1 Electrons are Not Ambidextrous 6 Krishna Kumar, November 4 2014 If Q sufficiently large (wavelength < 10 fm) , nuclear size modifies formula The Size of a Nucleus Increase momentum transfer -> shorter wavelength -> higher resoluon -> smaller scales e Heavy, spinless d⇥ 4Z22E2 e γ = 208Pb nucleus d Mott q4 ⇥ Differential Cross Section

d d 2 = F (q) d d ⇥ ⇤Mott F (q) (r)

1 2 3 q (fm)-1 Electrons are Not Ambidextrous 6 Krishna Kumar, November 4 2014 If Q sufficiently large (wavelength < 10 fm) , nuclear size modifies formula The Size of a Nucleus Increase momentum transfer -> shorter wavelength -> higher resoluon -> smaller scales e Heavy, spinless d⇥ 4Z22E2 e γ nuclear = nucleus d Mott q4 charge ⇥ Differential Cross Section densities d d 2 = F (q) d d ⇥ ⇤Mott F (q) (r)

Electrons are Not Ambidextrous 6 Krishna Kumar, November 4 2014 The Size of the Proton

Otto Stern (1932) measured the proton

magnetic moment µp~ 2.5 µBohr : First indication that the proton was not just a positive, structureless electron (Nobel prize 1943)

Electrons are Not Ambidextrous 7 Krishna Kumar, November 4 2014 Precise e-p cross section measurements at various scattering angles The Size of the Proton

Otto Stern (1932) measured the proton

magnetic moment µp~ 2.5 µBohr : First indication that the proton was not just a positive, structureless electron (Nobel prize 1943)

Stanford U. Mark III Accelerator McAllister and Hofstadter, Physical Review 102 (1956) 851.

Electrons are Not Ambidextrous 7 Krishna Kumar, November 4 2014 Precise e-p cross section measurements at various scattering angles The Size of the Proton

Otto Stern (1932) measured the proton

magnetic moment µp~ 2.5 µBohr : First indication that the proton was not just a positive, structureless electron (Nobel prize 1943)

Stanford U. Mark III Accelerator McAllister and Hofstadter, Physical Review 102 (1956) 851.

Electrons are Not Ambidextrous 7 Krishna Kumar, November 4 2014 Precise e-p cross section measurements at various scattering angles The Size of the Proton

Otto Stern (1932) measured the proton

magnetic moment µp~ 2.5 µBohr : First indication that the proton was not just a positive, structureless electron (Nobel prize 1943)

Stanford U. Mark III Accelerator McAllister and Hofstadter, Physical Review 102 (1956) 851.

Electrons are Not Ambidextrous 7 Krishna Kumar, November 4 2014 Precise e-p cross section measurements at various scattering angles The Size of the Proton

Otto Stern (1932) measured the proton

magnetic moment µp~ 2.5 µBohr : First indication that the proton was not just a positive, structureless electron (Nobel prize 1943)

Stanford U. Mark III Accelerator McAllister and Hofstadter, Physical Review 102 (1956) 851.

It isn’t Mott, nor Dirac, nor modified Dirac with a larger magnetic moment…

Electrons are Not Ambidextrous 7 Krishna Kumar, November 4 2014 Precise e-p cross section measurements at various scattering angles The Size of the Proton

Otto Stern (1932) measured the proton

magnetic moment µp~ 2.5 µBohr : First indication that the proton was not just a positive, structureless electron (Nobel prize 1943)

Stanford U. Mark III Accelerator McAllister and Hofstadter, Physical Review 102 (1956) 851.

It isn’t Mott, nor Dirac, nor modified Dirac with a larger magnetic moment…

the proton has finite size ~ 1 fm

Robert Hofstadter – Noble Prize 1961

Electrons are Not Ambidextrous 7 Krishna Kumar, November 4 2014 Deep Inelastic Scattering Point-like Structures in the Proton Discovery of structureless partons inside protons and neutrons

- - e e W = Mass of recoiling fragments γ* p X

•proton absorbs energy and breaks up •total observed energy no longer conserved •need to measure both scattering angle and scattered momentum or energy

SLAC: Stanford Linear Accelerator Center

W1 and W2 are structure functions x is fraction of proton momentum carried by struck fragment

Electrons are Not Ambidextrous 8 Krishna Kumar, November 4 2014 Deep Inelastic Scattering Point-like Structures in the Proton Discovery of structureless partons inside protons and neutrons

- - e e W = Mass of recoiling fragments electrons are hitting * γ structureless objects p X that have negligible size!

•proton absorbs energy and breaks up •total observed energy no longer conserved •need to measure both scattering angle and scattered momentum or energy

SLAC: Stanford Linear Accelerator Center

W1 and W2 are structure functions x is fraction of proton momentum carried by struck fragment

Friedman, Kendall & Taylor: Nobel Prize 1990, Measurement at SLAC

Electrons are Not Ambidextrous 8 Krishna Kumar, November 4 2014 Since the 1960’s Subatomic Structure

Helium Atom

Alpha Particle

Electrons are Not Ambidextrous 9 Krishna Kumar, November 4 2014 Since the 1960’s Subatomic Structure

Electrons are Not Ambidextrous 9 Krishna Kumar, November 4 2014 The Weak Force and Particle Handedness The Weak Force Solar p-p chain Radioactivity

2H

Electrons are Not Ambidextrous 11 Krishna Kumar, November 4 2014 The Weak Force Solar p-p chain Radioactivity

Fermi Theory for weak interactions

Universal strength: coupling constant GF

“Effective” low energy theory that explains many 2H observed properties of radioactive nuclear decays

Electrons are Not Ambidextrous 11 Krishna Kumar, November 4 2014 The Weak Force Solar p-p chain Radioactivity

Fermi Theory for weak interactions

Universal strength: coupling constant GF

“Effective” low energy theory that explains many 2H observed properties of radioactive nuclear decays Theory known to breakdown at energy > 100 GeV Electrons are Not Ambidextrous 11 Krishna Kumar, November 4 2014 Similar to the landmark unification of electric and magnetic forces via Maxwell’s Equations Electroweak Unification

Early 1950s: first attempts to describe weak and electromagnetic interactions under one unified framework

Weak interactions are short range (much shorter than 1 fm)

Electrons are Not Ambidextrous 12 Krishna Kumar, November 4 2014 Similar to the landmark unification of electric and magnetic forces via Maxwell’s Equations Electroweak Unification

Early 1950s: first attempts to describe weak and electromagnetic interactions under one unified framework

Weak interactions are short range (much shorter than 1 fm)

How can a short range and long range force be unified?

Electrons are Not Ambidextrous 12 Krishna Kumar, November 4 2014 Similar to the landmark unification of electric and magnetic forces via Maxwell’s Equations Electroweak Unification

Early 1950s: first attempts to describe weak and electromagnetic interactions under one unified framework

Weak interactions are short range (much shorter than 1 fm)

How can a short range and long range force be unified?

1 q V = 4πε0 r

€

Electrons are Not Ambidextrous 12 Krishna Kumar, November 4 2014 Similar to the landmark unification of electric and magnetic forces via Maxwell’s Equations Electroweak Unification

Early 1950s: first attempts to describe weak and electromagnetic interactions under one unified framework

Weak interactions are short range (much shorter than 1 fm)

How can a short range and long range force be unified?

1 q −[ mc ] r V = e ! 4πε0 r

€ €

Electrons are Not Ambidextrous 12 Krishna Kumar, November 4 2014 Similar to the landmark unification of electric and magnetic forces via Maxwell’s Equations Electroweak Unification

Early 1950s: first attempts to describe weak and electromagnetic interactions under one unified framework

Weak interactions are short range (much shorter than 1 fm)

How can a short range and long range force be unified?

-1 − mc r [-0.45 (attometer) × r] 1 q [ ! ] e V = e 4πε0 r massive force carriers are W bosons ~ 80 GeV 60Co 60Ni

€ €

Electrons are Not Ambidextrous 12 Krishna Kumar, November 4 2014 Similar to the landmark unification of electric and magnetic forces via Maxwell’s Equations Electroweak Unification

Early 1950s: first attempts to describe weak and electromagnetic interactions under one unified framework

Weak interactions are short range (much shorter than 1 fm)

How can a short range and long range force be unified?

-1 − mc r [-0.45 (attometer) × r] 1 q [ ! ] e V = e 4πε0 r massive force carriers are W bosons ~ 80 GeV 60Co 60Ni

Weak interactions do not obey mirror symmetry € € particles involved not ambidextrous Electrons are Not Ambidextrous 12 Krishna Kumar, November 4 2014 Discovery of Parity Violation in Weak Force Phenomena Failure of Ambidexterity

parity transformation (reflection) ! ! ! ! ! ! x,y,z → −x,−y,−z p → −p, L → L, s → s 60Ni

60Co € €

Weak decay of 60Co Nucleus

Electrons are Not Ambidextrous 13 Krishna Kumar, November 4 2014 Discovery of Parity Violation in Weak Force Phenomena Failure of Ambidexterity

parity transformation (reflection) ! ! ! ! ! ! x,y,z → −x,−y,−z p → −p, L → L, s → s 60Ni

60Co € €

Weak decay of 60Co Nucleus

Electrons are Not Ambidextrous 13 Krishna Kumar, November 4 2014 Discovery of Parity Violation in Weak Force Phenomena Failure of Ambidexterity

parity transformation (reflection) ! ! ! ! ! ! x,y,z → −x,−y,−z p → −p, L → L, s → s 60Ni matter particles have spin = 1/2 60Co € ! ! s • p h = ! ! = ±1 € s p

Weak decay of handedness or 60 Co Nucleus helicity/chirality

€

Electrons are Not Ambidextrous 13 Krishna Kumar, November 4 2014 Discovery of Parity Violation in Weak Force Phenomena Failure of Ambidexterity

parity transformation (reflection) ! ! ! ! ! ! x,y,z → −x,−y,−z p → −p, L → L, s → s 60Ni matter particles have spin = 1/2 60Co € ! ! s • p h = ! ! = ±1 € s p

Weak decay of handedness or 60 Co Nucleus helicity/chirality

Mirror reflection flips sign of helicity 60 €Co 60Ni Left-handed right-handed left-handed L electron Only left-handed particles can exchange W bosons R right-handed (right-handed anti-particles) anti-neutrino

Electrons are Not Ambidextrous 13 Krishna Kumar, November 4 2014 Discovery of Parity Violation in Weak Force Phenomena Failure of Ambidexterity Nature is not “mirror-symmetric” parity transformation (reflection) ! ! ! ! ! ! x,y,z → −x,−y,−z p → −p, L → L, s → s 60Ni matter particles have spin = 1/2 60Co € ! ! s • p h = ! ! = ±1 € s p

Weak decay of handedness or 60 Co Nucleus helicity/chirality

Mirror reflection flips sign of helicity 60 €Co 60Ni Left-handed right-handed left-handed L electron Only left-handed particles can exchange W bosons R right-handed (right-handed anti-particles) anti-neutrino

Electrons are Not Ambidextrous 13 Krishna Kumar, November 4 2014 Is Electron Scattering Mirror-Symmetric? A Classic Paper

Electrons are Not Ambidextrous 14 Krishna Kumar, November 4 2014 Is Electron Scattering Mirror-Symmetric? A Classic Paper

Is there a neutral analog of the “charged” weak force? Electron-proton Neutron β Decay Weak Scattering

Electrons are Not Ambidextrous 14 Krishna Kumar, November 4 2014 Is Electron Scattering Mirror-Symmetric? A Classic Paper

Is there a neutral analog of the “charged” weak force? Electron-proton Neutron β Decay Weak Scattering

Electrons are Not Ambidextrous 14 Krishna Kumar, November 4 2014 Is Electron Scattering Mirror-Symmetric? A Classic Paper

Is there a neutral analog of the “charged” weak force? Electron-proton Neutron β Decay Weak Scattering

Parity-violating

Electrons are Not Ambidextrous 14 Krishna Kumar, November 4 2014 Is Electron Scattering Mirror-Symmetric? A Classic Paper

Is there a neutral analog of the “charged” weak force? Electron-proton Neutron β Decay Weak Scattering

Parity-violating

Electrons are Not Ambidextrous 14 Krishna Kumar, November 4 2014 Is Electron Scattering Mirror-Symmetric? A Classic Paper

Is there a neutral analog of the “charged” weak force? Electron-proton Neutron β Decay Weak Scattering

Parity-violating p e- p - rotation - e p p e- e p longitudinally reflection polarized - e p e-

Electrons are Not Ambidextrous 14 Krishna Kumar, November 4 2014 Parity-Violating Electron Scattering How Big is the Asymmetry?

•One of the incident beams longitudinally polarized •Change sign of longitudinal polarization •Measure fractional rate difference

Electrons are Not Ambidextrous 16 Krishna Kumar, November 4 2014 How Big is the Asymmetry?

•One of the incident beams longitudinally polarized •Change sign of longitudinal polarization •Measure fractional rate difference

−4 2 2 APV ~ 10 ⋅ Q (GeV )

€

Electrons are Not Ambidextrous 16 Krishna Kumar, November 4 2014 Need high rate with high 4-momentum transfer How Big is the Asymmetry?

•One of the incident beams longitudinally polarized •Change sign of longitudinal polarization E’ 4-momentum transfer •Measure fractional rate difference θ θ Q2 = 4EE " sin2 E 2

€ −4 2 2 APV ~ 10 ⋅ Q (GeV )

€

Electrons are Not Ambidextrous 16 Krishna Kumar, November 4 2014 Need high rate with high 4-momentum transfer How Big is the Asymmetry?

•One of the incident beams longitudinally polarized •Change sign of longitudinal polarization E’ 4-momentum transfer •Measure fractional rate difference θ θ Q2 = 4EE " sin2 E 2

€ −4 2 2 APV ~ 10 ⋅ Q (GeV )

Two developments set the stage for the first successful APV measurement: The€ frst was a crucial consequence from the discovery of quarks

Electrons are Not Ambidextrous 16 Krishna Kumar, November 4 2014 Need high rate with high 4-momentum transfer How Big is the Asymmetry?

•One of the incident beams longitudinally polarized •Change sign of longitudinal polarization E’ 4-momentum transfer •Measure fractional rate difference θ θ Q2 = 4EE " sin2 E 2

large rate at large Q2 € −4 2 2 APV ~ 10 ⋅ Q (GeV )

Two developments set the stage for the first successful APV measurement: The€ frst was a crucial consequence from the discovery of quarks

Electrons are Not Ambidextrous 16 Krishna Kumar, November 4 2014 A Model of Leptons: Steven Weinberg (1967) Electroweak Theory

Left- Right- gL gR 1 2 1 2 Charge 0,±1,± ,± 0,±1,± ,± γ 3 3 3 3 1 W Charge T = ± zero 2 € € 2 2 Z Charge T − qsin θW −qsin θW €

€ €

Electrons are Not Ambidextrous 17 Krishna Kumar, November 4 2014 A Model of Leptons: Steven Weinberg (1967) Electroweak Theory

μ- Left- Right- gL gR 1 2 1 2 + γ Charge 0,±1,± ,± 0,±1,± ,± νμ W 3 3 3 3 1 W Charge T = ± zero Charged Current 2 € € 2 2 Z Charge T − qsin θW −qsin θW €

€ €

Electrons are Not Ambidextrous 17 Krishna Kumar, November 4 2014 A Model of Leptons: Steven Weinberg (1967) Electroweak Theory The correct description of the neutral weak force The Z boson incorporated μ- ν μ Left- Right- gL gR 1 2 1 2 0, 1, , 0,±1,± ,± ν + 0 γ Charge ± ± ± μ W νμ Z 3 3 3 3 1 W Charge T = ± zero Charged Current Neutral Current 2 € € 2 2 Z Charge T − qsin θW −qsin θW €

€ €

Electrons are Not Ambidextrous 17 Krishna Kumar, November 4 2014 A Model of Leptons: Steven Weinberg (1967) Electroweak Theory The correct description of the neutral weak force The Z boson incorporated μ- ν μ Left- Right- gL gR 1 2 1 2 0, 1, , 0,±1,± ,± ν + 0 γ Charge ± ± ± μ W νμ Z 3 3 3 3 1 W Charge T = ± zero Charged Current Neutral Current 2 € One free parameter: € 2 2 Z Charge T − qsin θW −qsin θW weak mixing angle θW €

€ €

Electrons are Not Ambidextrous 17 Krishna Kumar, November 4 2014 A Model of Leptons: Steven Weinberg (1967) Electroweak Theory The correct description of the neutral weak force The Z boson incorporated μ- ν μ Left- Right- gL gR 1 2 1 2 0, 1, , 0,±1,± ,± ν + 0 γ Charge ± ± ± μ W νμ Z 3 3 3 3 1 W Charge T = ± zero Charged Current Neutral Current 2 € One free parameter: € 2 2 Z Charge T − qsin θW −qsin θW weak mixing angle θW € Does electron-nucleon deep inelastic scattering exhibit parity violation? Weinberg model € € - - Parity is violated e e 4 Z* A 10 ? PV ⇠ Parity is conserved

The first atomic parity violation measurements negative! Electrons are Not Ambidextrous 17 Krishna Kumar, November 4 2014 polarized electron-unpolarized deuteron deep inelastic scattering SLAC E122 C.Y. Prescott et al, 1978

conduction band -1/2 +1/2 need more than circularly polarized R 1010 events GaAs Eg = 1.43 eV

780 - 850 nmL 4 -3/2 valence band +3/2 APV 10 Estrain = 0.05 eV ⇠ -1/2 +1/2 5 (A ) 10 PV ⇠

Electrons are Not Ambidextrous 18 Krishna Kumar, November 4 2014 polarized electron-unpolarized deuteron deep inelastic scattering SLAC E122 C.Y. Prescott et al, 1978

conduction band -1/2 +1/2 need more than circularly polarized R 1010 events GaAs Eg = 1.43 eV

780 - 850 nmL 4 -3/2 valence band +3/2 APV 10 Estrain = 0.05 eV ⇠ -1/2 +1/2 5 (A ) 10 PV ⇠ •Optical pumping of a GaAs wafer: “black magic” chemical treatment to boost quantum efficiency ! •Rapid helicity reversal: polarization sign flips ~ 100 Hz to minimize the impact of drifts ! •Helicity-correlated beam motion: under sign flip, beam stability at the micron level

Electrons are Not Ambidextrous 18 Krishna Kumar, November 4 2014 polarized electron-unpolarized deuteron deep inelastic scattering SLAC E122 C.Y. Prescott et al, 1978

conduction band -1/2 +1/2 need more than circularly polarized R 1010 events GaAs Eg = 1.43 eV

780 - 850 nmL 4 -3/2 valence band +3/2 APV 10 Estrain = 0.05 eV ⇠ -1/2 +1/2 5 (A ) 10 PV ⇠ •Optical pumping of a GaAs wafer: “black magic” chemical treatment to •Parity Violation in Weak boost quantum efficiency Neutral Current Interactions ! ! Rapid helicity reversal: polarization 2 • •sin θW = 0.224 ± 0.020: same as sign flips ~ 100 Hz to minimize the in neutrino scattering impact of drifts ! ! •helped established the Standard •Helicity-correlated beam motion: Model (SM) of electroweak & under sign flip, beam stability at the strong interactions micron level

Electrons are Not Ambidextrous 18 Krishna Kumar, November 4 2014 polarized electron-unpolarized deuteron deep inelastic scattering SLAC E122 C.Y. Prescott et al, 1978 Glashow, Weinberg, Salam Nobel Prize awarded in 1979

conduction band -1/2 +1/2 need more than circularly polarized R 1010 events GaAs Eg = 1.43 eV

780 - 850 nmL 4 -3/2 valence band +3/2 APV 10 Estrain = 0.05 eV ⇠ -1/2 +1/2 5 (A ) 10 PV ⇠ •Optical pumping of a GaAs wafer: “black magic” chemical treatment to •Parity Violation in Weak boost quantum efficiency Neutral Current Interactions ! ! Rapid helicity reversal: polarization 2 • •sin θW = 0.224 ± 0.020: same as sign flips ~ 100 Hz to minimize the in neutrino scattering impact of drifts ! ! •helped established the Standard •Helicity-correlated beam motion: Model (SM) of electroweak & under sign flip, beam stability at the strong interactions micron level

Electrons are Not Ambidextrous 18 Krishna Kumar, November 4 2014 Continuous interplay between probing hadron structure and electroweak physics 4 Decades of Progress Parity-violating electron scattering has become a precision tool photocathodes, polarimetry, high power cryotargets, nanometer beam stability, precision beam diagnostics, low noise electronics, radiation hard detectors PVeS Experiment Summary Pioneering electron-quark PV DIS experiment SLAC E122 Pioneering Nuclear Studies (1998-2010) 100% -4 10% 10 S.M. Study (2003-2012) State-of-the-art: Future E122 1% • sub-part per billion statistical -5 PVDIS-6 10 G0 reach and systematic control Mainz-Be H-I -6 SAMPLE SOLID 0.1% • sub-1% normalization control

) 10 G0 A4 MIT-12C PV A4 H-III A4

(A H-He -7 δ 10 H-II Physics Topics PREX-I CREX •Strange Quark Form Factors! E158 PREX-II -8 10 Qweak SLAC! •Neutron skin of a heavy nucleus! ILC-Moller MIT-Bates! •Indirect Searches for New Interactions! MESA-12C -9 Mainz! 10 MOLLER •Novel Probes of Nucleon Structure! MESA-P2 Jefferson Lab •Electroweak Structure Functions at the EIC! 10-10 •Charge Lepton Flavor Violation at the EIC 10-8 10-7 10-6 10-5 10-4 10-3 APV Electrons are Not Ambidextrous 19 Krishna Kumar, November 4 2014 Neutron Skin of a Heavy Nucleus EM Charge vs Weak Charge Density

C. Horowitz

Rp ~ 5.5 fm 208Pb

Electrons are Not Ambidextrous 21 Krishna Kumar, November 4 2014 EM Charge vs Weak Charge Density

C. Horowitz

Rp ~ 5.5 fm 208Pb

neutrons expected to occupy a larger volume

Electrons are Not Ambidextrous 21 Krishna Kumar, November 4 2014 p n n p 2 Q EM ~ 1 Q EM ~ 0 Q W ~ 1 Q W ~ 1 - 4sin θW EM Charge vs Weak Charge Density

C. Horowitz

Rp ~ 5.5 fm 208Pb

neutrons expected to occupy a larger volume

Electrons are Not Ambidextrous 21 Krishna Kumar, November 4 2014 p n n p 2 Q EM ~ 1 Q EM ~ 0 Q W ~ 1 Q W ~ 1 - 4sin θW EM Charge vs Weak Charge Density

proton neutron C. Horowitz Electric (γ) charge 1 0 γ Weak ( -0.08 1

Rp ~ 5.5 fm 2 F Q2 GFQ n ( ) APV ≈ 208 2 Pb 4πα 2 Fp (Q )

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neutrons expected to occupy a larger volume

parity-violating electron scattering can directly constrain the RMS radius rn of a heavy spinless nucleus Electrons are Not Ambidextrous 21 Krishna Kumar, November 4 2014 p n n p 2 Q EM ~ 1 Q EM ~ 0 Q W ~ 1 Q W ~ 1 - 4sin θW EM Charge vs Weak Charge Density

proton neutron C. Horowitz Electric (γ) charge 1 0 γ Weak ( -0.08 1

Rp ~ 5.5 fm 2 F Q2 GFQ n ( ) APV ≈ 208 2 Pb 4πα 2 Fp (Q )

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electroweak neutrons expected to probe occupy a larger volume R. Furnstahl

parity-violating electron Mean Field Theory fit mostly by data other scattering can directly than neutron densities constrain the RMS radius rn of a heavy spinless nucleus Electrons are Not Ambidextrous 21 Krishna Kumar, November 4 2014 Neutron Distribution in a Nucleus What is the physics? …..And why is it interesting?

pressure pushes against surface tension

Symmetry Energy Equation of state (EOS) of dense nuclear matter 2 E(⇢, )=E0(⇢, = 0) + S(⇢) (⇢ ⇢ ) = n p ⇢

Electrons are Not Ambidextrous 22 Krishna Kumar, November 4 2014 Neutron Distribution in a Nucleus What is the physics? …..And why is it interesting?

pressure pushes against surface tension Symmetry Energy Constraints Symmetry• Heavy Ion Collisions Energy •Nuclear Binding Energies Equation of state (EOS) •Isobaric Analog State Energies of dense nuclear matter •Neutron Skin Thickness 2 pion and alpha scattering E(⇢, )=E0(⇢, = 0) + S(⇢) • •Dipole Polarizabilities (⇢n ⇢p) •Antiprotonic Atoms = ⇢ Involve model dependence and strong force uncertainties

Electrons are Not Ambidextrous 22 Krishna Kumar, November 4 2014 Neutron Distribution in a Nucleus What is the physics? …..And why is it interesting?

pressure pushes against surface tension Symmetry Energy Constraints Symmetry• Heavy Ion Collisions Energy •Nuclear Binding Energies Equation of state (EOS) •Isobaric Analog State Energies of dense nuclear matter •Neutron Skin Thickness 2 pion and alpha scattering E(⇢, )=E0(⇢, = 0) + S(⇢) • •Dipole Polarizabilities (⇢n ⇢p) •Antiprotonic Atoms = ⇢ Involve model dependence and strong force uncertainties

Electrons are Not Ambidextrous 22 Krishna Kumar, November 4 2014 Neutron Distribution in a Nucleus What is the physics? …..And why is it interesting?

pressure pushes against surface tension B.A.Brown, PRL 85 5296 (2000)

neutron Symmetry skin Energy Equation of state (EOS) of dense nuclear matter 2 E(⇢, )=E0(⇢, = 0) + S(⇢) dS P ⇢2 (⇢n ⇢p) ⇠ d⇢ = ⇢ ⇣ ⌘ Neutron matter P (MeV/fm3) x100 at a density of 0.1 fm-3. Electrons are Not Ambidextrous 22 Krishna Kumar, November 4 2014 size of neutron “skin” measures density dependence of symmetry energy Neutron Distribution in a Nucleus What is the physics? …..And why is it interesting?

pressure pushes against surface tension B.A.Brown, PRL 85 5296 (2000)

neutron Symmetry skin Energy Equation of state (EOS) of dense nuclear matter 2 E(⇢, )=E0(⇢, = 0) + S(⇢) dS P ⇢2 size of neutron skin ⇠ d⇢ ⇣ ⌘ density dependence of symmetry pressure Neutron matter P (MeV/fm3) energy at subnuclear densities x100 at a density of 0.1 fm-3. Electrons are Not Ambidextrous 22 Krishna Kumar, November 4 2014 γ The Pb Radius EXperiment Concept: PREX at the Thomas Jefferson National Accelerator Facility

E = 1 GeV

2 F Q2 GFQ n ( ) APV ≈ 2 4πα 2 Fp (Q )

Donnelly, Dubach & Sick (1988) Horowitz, Michaels € and Souder (2001)

Electrons are Not Ambidextrous 23 Krishna Kumar, November 4 2014 γ The Pb Radius EXperiment Concept: PREX at the Thomas Jefferson National Accelerator Facility

E = 1 GeV

2 F Q2 GFQ n ( ) APV ≈ 2 4πα 2 Fp (Q )

Donnelly, Dubach & Sick (1988) Horowitz, Michaels € and Souder (2001)

> 1015 events!

Electrons are Not Ambidextrous 23 Krishna Kumar, November 4 2014 γ The Pb Radius EXperiment Concept: PREX at the Thomas Jefferson National Accelerator Facility

E = 1 GeV

2 F Q2 GFQ n ( ) APV ≈ 2 4πα 2 Fp (Q ) Polarized e- Donnelly, Dubach & Sick (1988) Source Horowitz, Michaels € and Souder (2001) Hall A

> 1015 events!

Electrons are Not Ambidextrous 23 Krishna Kumar, November 4 2014 γ The Pb Radius EXperiment Concept: PREX at the Thomas Jefferson National Accelerator Facility Q2 ~ 0.01 GeV2 A ~ 0.7 ppm Roca-Maza et al PV Rate ~ 1 GHz ± 3% ∆(APV) ~ 20 ppb ± 0.06 fm ∆(Rn) ~ 0.06 fm

> 1015 events!

Electrons are Not Ambidextrous 23 Krishna Kumar, November 4 2014 γ The Pb Radius EXperiment Concept: PREX at the Thomas Jefferson National Accelerator Facility Q2 ~ 0.01 GeV2 A ~ 0.7 ppm Roca-Maza et al PV Rate ~ 1 GHz ± 3% ∆(APV) ~ 20 ppb ± 0.06 fm ∆(Rn) ~ 0.06 fm

Tiny signal buried in known background > 1015 events! Lockin Amplifier output

apparatus modulator lockin input Electrons are Not Ambidextrous 23 Krishna Kumar, November 4 2014 γ The Pb Radius EXperiment Concept: PREX at the Thomas Jefferson National Accelerator Facility Q2 ~ 0.01 GeV2 A ~ 0.7 ppm Roca-Maza et al PV Rate ~ 1 GHz ± 3% ∆(APV) ~ 20 ppb ± 0.06 fm ∆(Rn) ~ 0.06 fm

Tiny signal buried in known background > 1015 events! Lockin Amplifier output

injector accelerator target spectrometer detector

Electrons are Not Ambidextrous 23 Krishna Kumar, November 4 2014 Polarized Beam at JLab

B. Matthew Poelker 2011 E. O. Lawrence Award

Record Performance (2012): 180 µA at 89% polarization

Electron Gun Requirements • Ultrahigh vacuum Beam Current • No field emission • Maintenance-free Chargefromphotogun

24 Hours

Electrons are Not Ambidextrous 24 Krishna Kumar, November 4 2014 Polarized Beam at JLab

B. Matthew Poelker 2011 E. O. Lawrence Award

Record Performance (2012): 180 µA at 89% polarization

Electron Gun Requirements • Ultrahigh vacuum Beam Current • No field emission • Maintenance-free Chargefromphotogun

24 Hours ² Beam helicity is chosen pseudo-randomly at multiple of 60 Hz • sequence of “window multiplets”

Electrons are Not Ambidextrous 24 Krishna Kumar, November 4 2014 Polarized Beam at JLab

B. Matthew Poelker 2011 E. O. Lawrence Award

Record Performance (2012): 180 µA at 89% polarization

Electron Gun Requirements • Ultrahigh vacuum Beam Current • No field emission • Maintenance-free Chargefromphotogun

24 Hours ² Beam helicity is chosen pseudo-randomly at multiple of 60 Hz • sequence of “window multiplets” Example: at 240 Hz reversal Choose 2 pairs pseudo-randomly, force complementary two pairs to follow ! Analyze each “macropulse” of 8 windows any line noise effect here will cancel here together

Electrons are Not Ambidextrous 24 Krishna Kumar, November 4 2014 Polarized Beam at JLab

B. Matthew Poelker 2011 E. O. Lawrence Award

Record Performance (2012): 180 µA at 89% polarization

Electron Gun Requirements • Ultrahigh vacuum Beam Current • No field emission • Maintenance-free Chargefromphotogun

24 Hours ² Beam helicity is chosen pseudo-randomly at multiple of 60 Hz • sequence of “window multiplets” Example: at 240 Hz reversal Choose 2 pairs pseudo-randomly, force complementary two pairs to follow ! Analyze each “macropulse” of 8 windows any line noise effect here will cancel here together Noise characteristics have been unimportant in past JLab experiments: Not so for PREX, Qweak and MOLLER.... Electrons are Not Ambidextrous 24 Krishna Kumar, November 4 2014 PREX @ JLab Hall A: Overview

circa 1999

Electrons are Not Ambidextrous 25 Krishna Kumar, November 4 2014 PREX @ JLab Hall A: Overview

208 Pb

circa 1999 12 C beam

Electrons are Not Ambidextrous 25 Krishna Kumar, November 4 2014 PREX @ JLab Hall A: Overview

circa 1999

Electrons are Not Ambidextrous 25 Krishna Kumar, November 4 2014 PREX @ JLab Hall A: Overview

circa 1999

Electrons are Not Ambidextrous 25 Krishna Kumar, November 4 2014 second major SLAC E122 innovation: “flux integration” High Flux, Low Background Hall A High Resolution Spectrometers Elastic detector Inelastic

1 GHz scattered flux Quad 2 x 10-4 statistical error Dipole 30 times per second target Q Q

Electrons are Not Ambidextrous 26 Krishna Kumar, November 4 2014 second major SLAC E122 innovation: “flux integration” High Flux, Low Background Hall A High Resolution Spectrometers Elastic detector Inelastic

hardware resolution: 1 GHz scattered flux ∆p/p ~ 10-3 Quad 2 x 10-4 statistical error Dipole 30 times per second target Q Q

~10 cm Inelastic backgrounds negligible pure, thin 208Pb target

GeV Electrons are Not Ambidextrous 26 Krishna Kumar, November 4 2014 CW electron beam: scattered signal rate ~ 1 GHz Flux Integration 10 ppb (average 107 s)

A FR - FL Δ F pair = Apair= + Δ A FR + FL 2F

Detector D, Current I: F = D/I

Electrons are Not Ambidextrous 27 Krishna Kumar, November 4 2014 CW electron beam: scattered signal rate ~ 1 GHz Flux Integration 10 Hz Stat. Width: 100 ppm N = 100 M: 10 ppb (average 107 s)

A FR - FL Δ F pair = Apair= + Δ A FR + FL 2F

Detector D, Current I: F = D/I

Electrons are Not Ambidextrous 27 Krishna Kumar, November 4 2014 CW electron beam: scattered signal rate ~ 1 GHz Flux Integration 10 Hz Stat. Width: 100 ppm N = 100 M: 10 ppb (average 107 s)

A FR - FL Δ F pair = Apair= + Δ A FR + FL 2F

Detector D, Current I: F = D/I ΔI Δ E 2I 2E I order: x, y, θx, θy, E II order: e.g. spot-size Δ D Δ D - Δ I 2D 2D 2I

Electrons are Not Ambidextrous 27 Krishna Kumar, November 4 2014 CW electron beam: scattered signal rate ~ 1 GHz Flux Integration 10 Hz Stat. Width: 100 ppm N = 100 M: 10 ppb (average 107 s)

A FR - FL Δ F pair = Apair= + Δ A FR + FL 2F

Detector D, Current I: F = D/I ΔI Δ E 2I 2E I order: x, y, θx, θy, E II order: e.g. spot-size Δ D Δ D - Δ I 2D 2D 2I

After corrections, variance of Apair must get as close to counting statistics as possible: ~ 100 ppm at 10 Hz; central value then reflects Aphys

Electrons are Not Ambidextrous 27 Krishna Kumar, November 4 2014 CW electron beam: scattered signal rate ~ 1 GHz Flux Integration 10 Hz Stat. Width: 100 ppm N = 100 M: 10 ppb (average 107 s)

A FR - FL Δ F pair = Apair= + Δ A FR + FL 2F

Detector D, Current I: F = D/I ΔI Δ E 2I 2E I order: x, y, θx, θy, E II order: e.g. spot-size Δ D Δ D - Δ I 2D 2D 2I

After corrections, variance of Apair must get as close to counting statistics as possible: ~ 100 ppm at 10 Hz; central value then reflects Aphys

Must minimize (both) random and helicity-correlated fluctuations in average window-pair response of electron beam trajectory, energy and spot-size.

Electrons are Not Ambidextrous 27 Krishna Kumar, November 4 2014 CW electron beam: scattered signal rate ~ 1 GHz Flux Integration 10 Hz Stat. Width: 100 ppm N = 100 M: 10 ppb (average 107 s)

A FR - FL Δ F pair = Apair= + Δ A FR + FL 2F

Detector D, Current I: F = D/I ΔI Δ E 2I 2E I order: x, y, θx, θy, E II order: e.g. spot-size Δ D Δ D - Δ I 2D 2D 2I

After corrections, variance of Apair must get as close to counting statistics as possible: ~ 100 ppm at 10 Hz; central value then reflects Aphys

Must minimize (both) random and helicity-correlated fluctuations in average window-pair response of electron beam trajectory, energy and spot-size. The characteristics of the JLab beam, both at the 60 Hz time scale (~ppm, microns), to grand averages over several days (~ppb, nm), are critical to extracting a measurement which is dominated by statistical fluctuations. Electrons are Not Ambidextrous 27 Krishna Kumar, November 4 2014 Araw ~ 500 ppb Acorr = Adet - AQ + α ΔE+ Σβi Δxi Beam Stability Performance PREX-I ran from March to May 2012

Electrons are Not Ambidextrous 28 Krishna Kumar, November 4 2014 Araw ~ 500 ppb Acorr = Adet - AQ + α ΔE+ Σβi Δxi Beam Stability Performance PREX-I ran from March to May 2012 •Active feedback of charge asymmetry! •Careful laser alignment! •Precision beam position monitoring! •Active calibration of detector slopes

birefringent elements

Electrons are Not Ambidextrous 28 Krishna Kumar, November 4 2014 Araw ~ 500 ppb Acorr = Adet - AQ + α ΔE+ Σβi Δxi Beam Stability Performance PREX-I ran from March to May 2012

Electrons are Not Ambidextrous 28 Krishna Kumar, November 4 2014 Araw ~ 500 ppb Acorr = Adet - AQ + α ΔE+ Σβi Δxi Beam Stability Performance PREX-I ran from March to May 2012

raw average: ~ 20 nm corrections: < 5 nm or 100 ppb microns Sign flips using ½ wave plate & Wien filter ++ -+ +- --

Electrons are Not Ambidextrous 28 Krishna Kumar, November 4 2014 Araw ~ 500 ppb Acorr = Adet - AQ + α ΔE+ Σβi Δxi Beam Stability Performance 2 methods of “slow” reversal

raw average: ~ 20 nm corrections: < 5 nm or 100 ppb microns Sign flips using ½ wave plate & Wien filter ++ -+ +- --

Electrons are Not Ambidextrous 28 Krishna Kumar, November 4 2014 Araw ~ 500 ppb Acorr = Adet - AQ + α ΔE+ Σβi Δxi Beam Stability Performance 2 methods of “slow” reversal

raw average: ~ 20 nm corrections: < 5 nm or 100 ppb microns Sign flips using ½ wave plate & Wien filter ++ -+ +- --

Electron Beam

Electrons are Not Ambidextrous 28 Krishna Kumar, November 4 2014 Raw Asymmetry Data

integrated rate ~ 1 GHz

Statistical behavior of 171 ppm width data consistent: @ 30 Hz detector fluctuations dominated by electron Ai A¯ 120 Hz flipping counting statistics ± 0.1% i Araw

parts per million standard deviations

Electrons are Not Ambidextrous 29 Krishna Kumar, November 4 2014 Raw Asymmetry Data

integrated rate ~ 1 GHz

Statistical behavior of 171 ppm width data consistent: @ 30 Hz detector fluctuations dominated by electron Ai A¯ 120 Hz flipping counting statistics ± 0.1% i Araw

parts per million standard deviations ppm

Electrons are Not Ambidextrous 29 Krishna Kumar, November 4 2014 Raw Asymmetry Data raw statistical error: 50 ppb (8.4%) integrated rate ~ 1 GHz

Statistical behavior of 171 ppm width data consistent: @ 30 Hz detector fluctuations dominated by electron Ai A¯ 120 Hz flipping counting statistics ± 0.1% i Araw

parts per million standard deviations Grand averages of all 4 606 ± 113 combinations 496 ± 107 of slow reversal 566 ± 095 685 ± 092

flips are ppm statistically consistent 594 ± 50 parts per billion (ppb) Electrons are Not Ambidextrous 29 Krishna Kumar, November 4 2014 systematic error due to electron beam asymmetries: 7 ppb Raw Asymmetry Data raw statistical error: 50 ppb (8.4%) integrated rate ~ 1 GHz

Statistical behavior of 171 ppm width data consistent: @ 30 Hz detector fluctuations dominated by electron Ai A¯ 120 Hz flipping counting statistics ± 0.1% i Araw

parts per million standard deviations Grand averages of all 4 606 ± 113 combinations 496 ± 107 of slow reversal 566 ± 095 685 ± 092

flips are ppm statistically consistent 594 ± 50 parts per billion (ppb) Electrons are Not Ambidextrous 29 Krishna Kumar, November 4 2014 Phys.Rev.Lett. 108 (2012) 112502 Normalization Errors

Absolute Relative Systematic Error (ppm) ( %) Polarization 0.0083 1.3 Detector Linearity 0.0076 1.2 Beam current normalization 0.0015 0.2 Rescattering 0.0001 0 Transverse Polarization 0.0012 0.2 Q2 0.0028 0.4 Target Backing 0.0026 0.4 Inelastic States 0 0 TOTAL 0.0140 2.1

Electrons are Not Ambidextrous 30 Krishna Kumar, November 4 2014 Phys.Rev.Lett. 108 (2012) 112502 Normalization Errors Goal for total systematic error ~ 2% achieved! Absolute Relative Systematic Error (ppm) ( %) Polarization 0.0083 1.3 Detector Linearity 0.0076 1.2 Beam current normalization 0.0015 0.2 Rescattering 0.0001 0 Transverse Polarization 0.0012 0.2 Q2 0.0028 0.4 Target Backing 0.0026 0.4 Inelastic States 0 0 TOTAL 0.0140 2.1

Electrons are Not Ambidextrous 30 Krishna Kumar, November 4 2014 Phys.Rev.Lett. 108 (2012) 112502 Normalization Errors Goal for total systematic error ~ 2% achieved! Absolute Relative Systematic Error (ppm) ( %) Polarization 0.0083 1.3 Detector Linearity 0.0076 1.2 Beam current normalization 0.0015 0.2 Rescattering 0.0001 0 Transverse Polarization 0.0012 0.2 Q2 0.0028 0.4 Target Backing 0.0026 0.4 Inelastic States 0 0 TOTAL 0.0140 2.1

Electrons are Not Ambidextrous 30 Krishna Kumar, November 4 2014 PREX Result

Phys.Rev.Lett. 108 (2012) 112502

Electrons are Not Ambidextrous 31 Krishna Kumar, November 4 2014 PREX Result

R =5.781 0.175(exp) n ± 0.026(model) ± 0.005(strange) fm ±

Phys.Rev.Lett. 108 (2012) 112502

Electrons are Not Ambidextrous 31 Krishna Kumar, November 4 2014 R R =0.302 0.175(exp) 0.026(model) 0.005(strange) fm n p ± ± ± PREX Result

R =5.781 0.175(exp) n ± 0.026(model) ± 0.005(strange) fm ±

Phys.Rev.Lett. 108 (2012) 112502

Electrons are Not Ambidextrous 31 Krishna Kumar, November 4 2014 R R =0.302 0.175(exp) 0.026(model) 0.005(strange) fm n p ± ± ± PREX Result

R =5.781 0.175(exp) n ± 0.026(model) ± 0.005(strange) fm ±

Phys.Rev.Lett. 108 (2012) 112502

First electroweak indication of a neutron skin of a heavy nucleus (CL ~ 90-95%)

Electrons are Not Ambidextrous 31 Krishna Kumar, November 4 2014 Future Prospects

Electrons are Not Ambidextrous 32 Krishna Kumar, November 4 2014 Future Prospects PREX-II approved; to run Fall 2016 (goal: 3% stat. error)

PREX-II

PREX-II

Electrons are Not Ambidextrous 32 Krishna Kumar, November 4 2014 Future Prospects PREX-II approved; to run Fall 2016 (goal: 3% stat. error)

PREX-II

E Rate (MHz APV days to (GeV) @ 50 µA) (ppm) 1% on R PREX-II 208 1.05 1700 0.6 30 120 1.25 810 1.1 20 48 1.7 270 2.5 12 2.2 150 2.8 18

Electrons are Not Ambidextrous 32 Krishna Kumar, November 4 2014 Ultimate goal: further factor of 2 error reduction beyond PREX-II Future Prospects PREX-II approved; to run Fall 2016 (goal: 3% stat. error)

PREX-II

ultimate goal

E Rate (MHz APV days to (GeV) @ 50 µA) (ppm) 1% on R PREX-II 208 1.05 1700 0.6 30 120 1.25 810 1.1 20 48 1.7 270 2.5 12 Expand measurements to 2.2 150 2.8 18 new Mainz-MESA facility Electrons are Not Ambidextrous 32 Krishna Kumar, November 4 2014 Neutron Skins and Neutron Stars Horowitz and Piekarewicz, PRL 86 (2001) Lattimer and Prakash, Science 304 (2004) • Heavy nucleus has neutron skin Heavy Nucleus Neutron Star • Neutron star has solid crust over liquid core skin ~10 Both neutron skin and neutron ~10 km star crust are made out of neutron fm rich matter at similar densities. crust

Electrons are Not Ambidextrous 33 Krishna Kumar, November 4 2014 Neutron Skins and Neutron Stars Horowitz and Piekarewicz, PRL 86 (2001) Lattimer and Prakash, Science 304 (2004) • Heavy nucleus has neutron skin Heavy Nucleus Neutron Star • Neutron star has solid crust over liquid core skin ~10 Both neutron skin and neutron ~10 km star crust are made out of neutron fm rich matter at similar densities. crust D. Page

Crab Nebula

Electrons are Not Ambidextrous 33 Krishna Kumar, November 4 2014 Neutron Skins and Neutron Stars Horowitz and Piekarewicz, PRL 86 (2001) Lattimer and Prakash, Science 304 (2004) • Heavy nucleus has neutron skin Heavy Nucleus Neutron Star • Neutron star has solid crust over liquid core skin ~10 Both neutron skin and neutron ~10 km star crust are made out of neutron fm rich matter at similar densities. crust D. Page

equation of state of Crab Nebula dense neutron matter

Electrons are Not Ambidextrous 33 Krishna Kumar, November 4 2014 Neutron Skins and Neutron Stars Horowitz and Piekarewicz, PRL 86 (2001) Lattimer and Prakash, Science 304 (2004) • Heavy nucleus has neutron skin Heavy Nucleus Neutron Star • Neutron star has solid crust over liquid core skin ~10 ~10 @Esym(⇢) km L =3⇢0 fm @⇢ ⇢0 crust NL1 D. Page Linear Fit, r = 0.979 Roca-Maza et al NL2 Nonrelativistic models NL3* NL-SV2 0.3 PK1NL3 Relativistic models TM1 NL3.s25

Sk-T4 G1 PK1.s24 G2 NL-RA1 PREX-II SkI5 PC-F1 NL-SH

PC-PK1 FSUGold 0.25 Sk-Rs

DD-ME1 DD-PC1 SkI2 (fm) Ska DD-ME2 SV Sk-Gs RHF-PKA1

np RHF-PKO3 r

∆ 0.2 SkM* SkSM*SkMP SIV HFB-17 MSL0 Sk-T6SkX MSkA SkP BCP SLy5 SLy4

0.15 HFB-8 MSk7 v090 D1N SGII D1S PREX-II 0.1 0 50 100 150 L (MeV) Electrons are Not Ambidextrous 33 Krishna Kumar, November 4 2014 Neutron Skins and Neutron Stars Horowitz and Piekarewicz, PRL 86 (2001) Lattimer and Prakash, Science 304 (2004) • Heavy nucleus has neutron skin Heavy Nucleus Neutron Star • Neutron star has solid crust over liquid core skin ~10 ~10 @Esym(⇢) km L =3⇢0 fm @⇢ ⇢0 crust NL1 D. Page Linear Fit, r = 0.979 Roca-Maza et al NL2 Nonrelativistic models NL3* NL-SV2 0.3 PK1NL3 Relativistic models TM1 NL3.s25

ultimate G1 Sk-T4 PK1.s24 G2 NL-RA1 PREX-II SkI5 PC-F1 goal NL-SH PC-PK1 FSUGold 0.25 Sk-Rs ± 0.03 fmDD-ME1 DD-PC1 SkI2 (fm) Ska DD-ME2 SV Sk-Gs RHF-PKA1

np RHF-PKO3 r

∆ 0.2 SkM* SkSM*SkMP SIV HFB-17 MSL0 Sk-T6SkX MSkA SkP BCP SLy5 ultimate SLy4

0.15 HFB-8 MSk7 goal v090 D1N ± 20 MeV SGII D1S PREX-II 0.1 0 50 100 150 L (MeV) Electrons are Not Ambidextrous 33 Krishna Kumar, November 4 2014 The Evolution of the Universe

Electrons are Not Ambidextrous 34 Krishna Kumar, November 4 2014 The Evolution of the Universe

Electrons are Not Ambidextrous 34 Krishna Kumar, November 4 2014 The Evolution of the Universe

Electrons are Not Ambidextrous 34 Krishna Kumar, November 4 2014 Search for New Superweak Forces Physics down to a length scale of 10-19 m well understood but..... Modern Electroweak Physics Many questions still unanswered…. The High Energy Frontier: Collider Physics The Cosmic Frontier: Particle, Nuclear and Gravitational Astrophysics A comprehensive search for clues requires, in addition: The Intensity/Precision Frontier

Electrons are Not Ambidextrous 36 Krishna Kumar, November 4 2014 Physics down to a length scale of 10-19 m well understood but..... Modern Electroweak Physics Many questions still unanswered…. The High Energy Frontier: Collider Physics The Cosmic Frontier: Particle, Nuclear and Gravitational Astrophysics A comprehensive search for clues requires, in addition: The Intensity/Precision Frontier ✦ Violation of Accidental (?) Symmetries ★ Neutrinoless Double-Beta Decay, Electric Dipole Moments... ✦ Direct Detection of Dark Matter ✦ Measurements of Neutrino Masses and Mixing ✦ Precise Measurements of SM observables Intense beams, ultra-high precision, exotic nuclei, table-top experiments, rare processes.... Electrons are Not Ambidextrous 36 Krishna Kumar, November 4 2014 Electroweak Interactions at scales much lower than the W/Z mass Indirect Clues

Dynamics involving Many theories predict new forces that E particles with m > Λ disappeared when the universe cooled

courtesy ! Λ (~TeV) V. Cirigliano! H. Maruyama

MW,Z (100 GeV) 1 1 = + 5 + 6 + L LSM L 2 L ···

higher dimensional operators can Heavy Z’s and neutrinos, technicolor, be systematically classified compositeness, extra dimensions, SUSY… SM amplitudes can be very precisely predicted

Electrons are Not Ambidextrous 37 Krishna Kumar, November 4 2014 Electroweak Interactions at scales much lower than the W/Z mass Indirect Clues

Dynamics involving Many theories predict new forces that E particles with m > Λ disappeared when the universe cooled

courtesy ! Λ (~TeV) V. Cirigliano! H. Maruyama

MW,Z (100 GeV) 1 1 = + 5 + 6 + L LSM L 2 L ···

higher dimensional operators can Heavy Z’s and neutrinos, technicolor, be systematically classified compositeness, extra dimensions, SUSY… SM amplitudes can be very precisely predicted Search for new neutral superweak forces l l 1 1 Look for tiny but measurable deviations from 1 0 6 Z precisely calculable predictions for SM processes 2 L f f 2 2 must reach Λ ~ several TeV Electrons are Not Ambidextrous 37 Krishna Kumar, November 4 2014 2 All flavor-conserving weak neutral current amplitudes are functions of sin θW Electron’s Weak Charge Parity-violating Electron-Electron Scattering

e T e T (gA gV +β gV gA )

2 gV and gA are function of sin θW Weak Charge QW

electron & proton target: small SM 2 QW = 1 4 sin ✓W weak charge

Electrons are Not Ambidextrous 38 Krishna Kumar, November 4 2014 2 All flavor-conserving weak neutral current amplitudes are functions of sin θW Electron’s Weak Charge Parity-violating Electron-Electron Scattering

e T e T (gA gV +β gV gA )

2 gV and gA are function of sin θW Weak Charge QW

electron & proton target: small SM 2 QW = 1 4 sin ✓W weak charge 1 + 6 2 L

Electrons are Not Ambidextrous 38 Krishna Kumar, November 4 2014 2 All flavor-conserving weak neutral current amplitudes are functions of sin θW Electron’s Weak Charge Parity-violating Electron-Electron Scattering

e T e T (gA gV +β gV gA )

2 gV and gA are function of sin θW Weak Charge QW

electron & proton target: small SM 8 2 2 A 8 10− E (1 4sin ) QW = 1 4 sin ✓W weak charge PV ≈ × beam − ϑ W Tiny! 1 + 2 6 € L

Electrons are Not Ambidextrous 38 Krishna Kumar, November 4 2014 2 All flavor-conserving weak neutral current amplitudes are functions of sin θW Electron’s Weak Charge Parity-violating Electron-Electron Scattering

e T e T (gA gV +β gV gA )

2 gV and gA are function of sin θW Weak Charge QW

electron & proton target: small SM 8 2 2 A 8 10− E (1 4sin ) QW = 1 4 sin ✓W weak charge PV ≈ × beam − ϑ W Tiny! 1 + 2 6 € L

45 & 48 GeV Beam SLAC E158: 1999-2004 85% longitudinal polarization 4-7 mrad LH2 End Station A at the Stanford Linear Accelerator Center (SLAC)

Electrons are Not Ambidextrous 38 Krishna Kumar, November 4 2014 Tree-level prediction: ~ 250 ppb A ≈ 8 ×10−8 E (1− 4sin2 ϑ ) PV beam W SLAC E158

€

Electrons are Not Ambidextrous 39 Krishna Kumar, November 4 2014 -9 Tree-level prediction: ~ 250 ppb APV = (-131 ± 14 ± 10) x 10 Final E158 Result A ≈ 8 ×10−8 E (1− 4sin2 ϑ ) PV beam W SLAC E158 Phys. Rev. Lett. 95 081601 (2005)

€

Electrons are Not Ambidextrous 39 Krishna Kumar, November 4 2014 -9 Tree-level prediction: ~ 250 ppb APV = (-131 ± 14 ± 10) x 10 Final E158 Result A ≈ 8 ×10−8 E (1− 4sin2 ϑ ) PV beam W SLAC E158 Phys. Rev. Lett. 95 081601 (2005)

€

Electrons are Not Ambidextrous 39 Krishna Kumar, November 4 2014 -9 Tree-level prediction: ~ 250 ppb APV = (-131 ± 14 ± 10) x 10 Final E158 Result A ≈ 8 ×10−8 E (1− 4sin2 ϑ ) PV beam W SLAC E158 Phys. Rev. Lett. 95 081601 (2005)

Czarnecki and Marciano (1995) €

Electrons are Not Ambidextrous 39 Krishna Kumar, November 4 2014 -9 Tree-level prediction: ~ 250 ppb APV = (-131 ± 14 ± 10) x 10 Final E158 Result A ≈ 8 ×10−8 E (1− 4sin2 ϑ ) PV beam W SLAC E158 Phys. Rev. Lett. 95 081601 (2005)

Czarnecki and Marciano (1995) €

2 sin θw some theory extrapolation error

Electrons are Not Ambidextrous 39 Krishna Kumar, November 4 2014 -9 Tree-level prediction: ~ 250 ppb APV = (-131 ± 14 ± 10) x 10 Final E158 Result A ≈ 8 ×10−8 E (1− 4sin2 ϑ ) PV beam W SLAC E158 Phys. Rev. Lett. 95 081601 (2005)

Czarnecki and Marciano (1995) €

0.250 Erler and Ramsey-Musolf (2004)

0.245 SLAC E158 NuTeV

Z Moller

0.240 ν-DIS (M ) (M > W

θ Cesium 2 APV

sin 0.235

Z-pole 0.230

0.225 0.001 0.01 0.1 1 10 100 1000 Q [GeV] Electrons are Not Ambidextrous 39 Krishna Kumar, November 4 2014 -9 Tree-level prediction: ~ 250 ppb APV = (-131 ± 14 ± 10) x 10 Final E158 Result A ≈ 8 ×10−8 E (1− 4sin2 ϑ ) PV beam W SLAC E158 Phys. Rev. Lett. 95 081601 (2005)

Czarnecki and Marciano (1995) €

0.250 Erler and Ramsey-Musolf (2004)

0.245 SLAC E158 NuTeV

Z Moller

0.240 ν-DIS (M ) (M > W

θ Cesium 2 APV

sin 0.235 3% Z-pole 0.230

0.225 0.001 0.01 0.1 1 10 100 1000 Q [GeV] Electrons are Not Ambidextrous 39 Krishna Kumar, November 4 2014 -9 Tree-level prediction: ~ 250 ppb APV = (-131 ± 14 ± 10) x 10 Final E158 Result A ≈ 8 ×10−8 E (1− 4sin2 ϑ ) PV beam W SLAC E158 Phys. Rev. Lett. 95 081601 (2005)

€ Limits on “New” Physics

95% 0.250 Erler and Ramsey-Musolf (2004)

0.245 17 TeV 16 TeV SLAC E158 NuTeV

Z Moller

0.240 ν-DIS (M ) (M > W

θ Cesium 2 APV

sin 0.235 3% 0.8 Z-pole 1.0 TeV (Zχ) 0.230

0.225 0.001 0.01 0.1 1 10 100 1000

Q [GeV] 0.01•GF Electrons are Not Ambidextrous 39 Krishna Kumar, November 4 2014 -9 Tree-level prediction: ~ 250 ppb APV = (-131 ± 14 ± 10) x 10 Final E158 Result A ≈ 8 ×10−8 E (1− 4sin2 ϑ ) PV beam W SLAC E158 Phys. Rev. Lett. 95 081601 (2005)

€ Limits on “New” Physics

95%

0.25 SM 0.248 current 2008 PDG 0.246 proposed 17 TeV 16 TeV 0.244

0.242 133 SLAC E158 ) Cs NuTeV

μ 0.24 ( Q ν-DIS Q (APV) W(e)

W W θ

2 0.238 sin 0.236 anti-screening screening 0.8 1.0 TeV (Z ) 0.234 χ LEP 1 0.232 Tevatron 0.23 SLC 0.228 0.0001 0.001 0.01 0.1 1 10 100 1000 10000 0.01•G μ [GeV] F Electrons are Not Ambidextrous 39 Krishna Kumar, November 4 2014 -9 Tree-level prediction: ~ 250 ppb APV = (-131 ± 14 ± 10) x 10 Final E158 Result A ≈ 8 ×10−8 E (1− 4sin2 ϑ ) PV beam W SLAC E158 Phys. Rev. Lett. 95 081601 (2005)

€ Limits on “New” Physics

95%

2013 17 TeV 16 TeV

0.8 1.0 TeV (Zχ) MOLLER: improve QW(e) by a factor of 5

0.01•GF Electrons are Not Ambidextrous 39 Krishna Kumar, November 4 2014 The 12 GeV Upgrade of JLab First physics beams to Hall A in 2014 126 GeV Upgrade magnets and power supplies 11 GeV

CHL-2

Two 1.10.6 GV linacs

Enhanced capabilities Lower pass beam energies in existing Halls still available

Electrons are Not Ambidextrous 40 Krishna Kumar, November 4 2014 An ultra-precise measurement of the weak mixing angle using Møller scattering 11 GeV Møller scaering MOLLER at JLab Measurement Of Lepton Lepton Electroweak Reaction Unique opportunity leveraging the 12 GeV Upgrade investment detector Evolutionary progression to systems extraordinary luminosity and electron beam stability with high longitudinal beam polarization hybrid toroid

upstream liquid

39 2 toroid hydrogen Luminosity: 3x10 cm /s! 28 m target

APV = 35.6 ppb

δ(APV) = 0.73 parts per billion

e δ(Q W) = ± 2.1 % (stat.) ± 1.0 % (syst.) 80% electron polarized beam Electrons are Not Ambidextrous 41 Krishna Kumar, November 4 2014 An ultra-precise measurement of the weak mixing angle using Møller scattering 11 GeV Møller scaering MOLLER at JLab Measurement Of Lepton Lepton Electroweak Reaction Unique opportunity leveraging the 12 GeV Upgrade investment detector Evolutionary progression to systems extraordinary luminosity and electron beam stability with high longitudinal beam polarization hybrid toroid

upstream liquid

39 2 toroid hydrogen Luminosity: 3x10 cm /s! 28 m target

APV = 35.6 ppb

δ(APV) = 0.73 parts per billion

e δ(Q W) = ± 2.1 % (stat.) ± 1.0 % (syst.)

MOLLER projected δ(sin2θW) 80% electron = ± 0.00026 (stat.) ± 0.00012 (syst.) polarized beam Electrons are Not Ambidextrous 41 Krishna Kumar, November 4 2014 best contact interaction reach for leptons at low OR high energy MOLLER Physics Reach sensitive to SUSY, doubly-charged scalars, heavy Z’ bosons, light dark Z’s... 2 2 QW = 1 4 sin ✓W gij µ 1 e1e2 = ¯e iµei¯e j ej L 22 + 2 6 i,j=L,R L = 7.5 TeV g2 g2 | RR LL|

Electrons are Not Ambidextrous 42 Krishna Kumar, November 4 2014 best contact interaction reach for leptons at low OR high energy MOLLER Physics Reach sensitive to SUSY, doubly-charged scalars, heavy Z’ bosons, light dark Z’s... 2 2 QW = 1 4 sin ✓W gij µ 1 e1e2 = ¯e iµei¯e j ej L 22 + 2 6 i,j=L,R L = 7.5 TeV g2 g2 | RR LL| An independent measurement of the weak mixing angle with precision comparable to the two best collider measurements

Electrons are Not Ambidextrous 42 Krishna Kumar, November 4 2014 best contact interaction reach for leptons at low OR high energy MOLLER Physics Reach sensitive to SUSY, doubly-charged scalars, heavy Z’ bosons, light dark Z’s... 2 2 QW = 1 4 sin ✓W gij µ 1 e1e2 = ¯e iµei¯e j ej L 22 + 2 6 i,j=L,R L = 7.5 TeV g2 g2 | RR LL| An independent measurement of the weak mixing angle with precision comparable to the two best collider measurements

However, Z resonance measurements insensitive to new contact interactions Electrons are Not Ambidextrous 42 Krishna Kumar, November 4 2014 Unique opportunity leveraging the 12 GeV Upgrade investment Best Low Q2 Reach in Next Decade

Qe 0.045 W ⇠ unprecedented e A 0.001 G QW new F sensitivity e = 2.4% ⇠ · QW

Electrons are Not Ambidextrous 43 Krishna Kumar, November 4 2014 Unique opportunity leveraging the 12 GeV Upgrade investment Best Low Q2 Reach in Next Decade

Qe 0.045 W ⇠ unprecedented e A 0.001 G QW new F sensitivity e = 2.4% ⇠ · QW LEP200 E158 Reach ee ee ⇤VV 17.7 TeV ⇤RR LL 17 TeV ⇠ ⇠

Electrons are Not Ambidextrous 43 Krishna Kumar, November 4 2014 Unique opportunity leveraging the 12 GeV Upgrade investment Best Low Q2 Reach in Next Decade

Qe 0.045 W ⇠ unprecedented e A 0.001 G QW new F sensitivity e = 2.4% ⇠ · QW LEP200 E158 Reach MOLLER Reach ee ee ee ⇤VV 17.7 TeV ⇤RR LL 17 TeV ⇤RR LL 38 TeV ⇠ ⇠ ⇠

Electrons are Not Ambidextrous 43 Krishna Kumar, November 4 2014 Unique opportunity leveraging the 12 GeV Upgrade investment Best Low Q2 Reach in Next Decade

Qe 0.045 W ⇠ unprecedented e A 0.001 G QW new F sensitivity e = 2.4% ⇠ · QW LEP200 E158 Reach MOLLER Reach ee ee ee ⇤VV 17.7 TeV ⇤RR LL 17 TeV ⇤RR LL 38 TeV ⇠ ⇠ ⇠

MOLLER is accessing discovery space that cannot be reached until the advent of a new lepton collider or neutrino factory Electrons are Not Ambidextrous 43 Krishna Kumar, November 4 2014 Unique opportunity leveraging the 12 GeV Upgrade investment Best Low Q2 Reach in Next Decade δ(sin2θW) = ± 0.00024 (stat.) ± 0.00013 (syst.) ~ 0.1% Qe 0.045 W ⇠ unprecedented e A 0.001 G QW new F sensitivity e = 2.4% ⇠ · QW LEP200 E158 Reach MOLLER Reach ee ee ee ⇤VV 17.7 TeV ⇤RR LL 17 TeV ⇤RR LL 38 TeV ⇠ ⇠ ⇠ Future projections, similar time scale: 2 2 ± 10σ discovery potential at Q <

(e) MOLLER

eff 0.231 0.231

2 (pdf uncertainties) sin 0.23 0.23 MOLLER is accessing discovery 0.229 APV 0.229 space that cannot be reached 0.228 0.228 until the advent of a new lepton 0.227 0.227 1 10 100 1000 collider or neutrino factory MH [GeV] Electrons are Not Ambidextrous 43 Krishna Kumar, November 4 2014 collaboration between U. Manitoba, Stony Brook and MIT Unique Spectrometer Concept )

ECOM = 53 MeV 10 e 8 e e Forward 6

4 Backward e identical particles! 2

0020406080 100 120 140 160 180

Scattered Electron Energy (GeV COM Scattering Angle (degrees) odd number of coils: 100% azimuthal acceptance 30

25

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Lab Scattering Angle (mrad) 1234567891011 meters Scattered Electron Energy (GeV)

first toroid hybrid toroid

meters Electrons are Not Ambidextrous 44 Krishna Kumar, November 4 2014 collaboration between U. Manitoba, Stony Brook and MIT Unique Spectrometer Concept )

ECOM = 53 MeV 10 e 8 e e Forward 6

4 Backward e identical particles! 2

0020406080 100 120 140 160 180

Scattered Electron Energy (GeV COM Scattering Angle (degrees) odd number of coils: 100% azimuthal acceptance 30 conceptual engineering design:

25 MIT-Bates, UMass, Manitoba

20

15

10

5

0

Lab Scattering Angle (mrad) 1234567891011 meters Scattered Electron Energy (GeV)

first toroid hybrid toroid

meters Electrons are Not Ambidextrous 44 Krishna Kumar, November 4 2014 Expertise from several generations of successful parity experiments MOLLER Status ~120 Collaborators, 30 institutions, 6 countries Technical Challenges

• ~ 150 GHz scattered electron rate – Design to flip Pockels cell ~ 2 kHz – 80 ppm pulse-to-pulse fluctuations • 1 nm control of beam centroid on target – Novel “slow helicity reversal” methods • > 10 gm/cm2 liquid hydrogen target – 1.5 m: ~ 5 kW @ 85 µA

• Full Azimuthal acceptance; θlab ~ 5 mrad – novel two-toroid spectrometer – radiation hard, highly segmented integrating detectors • Redundant 0.4% beam polarimetry – Pursue both Compton and Atomic Hydrogen techniques

Electrons are Not Ambidextrous 45 Krishna Kumar, November 4 2014 Expertise from several generations of successful parity experiments MOLLER Status ~120 Collaborators, 30 institutions, 6 countries Technical Challenges • Science Review: Sep 10, 2014 – Conducted by DOE NP: Tim Hallman, Chair • ~ 150 GHz scattered electron rate – one of the theory talks by Bill Marciano – Design to flip Pockels cell ~ 2 kHz – 6 panelists: T.W.Donnelly, D.Hertzog, – 80 ppm pulse-to-pulse fluctuations C.Horowitz, Z-T.Lu, M.Perelstein, T. Rizzo • 1 nm control of beam centroid on target – Positive outcome: unique opportunity highlighted, – Novel “slow helicity reversal” methods small theory uncertainty, importance of • > 10 gm/cm2 liquid hydrogen target achieving proposed error bar – 1.5 m: ~ 5 kW @ 85 µA

• Full Azimuthal acceptance; θlab ~ 5 mrad – novel two-toroid spectrometer – radiation hard, highly segmented integrating detectors • Redundant 0.4% beam polarimetry – Pursue both Compton and Atomic Hydrogen techniques

Electrons are Not Ambidextrous 45 Krishna Kumar, November 4 2014 Expertise from several generations of successful parity experiments MOLLER Status ~120 Collaborators, 30 institutions, 6 countries Technical Challenges • Science Review: Sep 10, 2014 – Conducted by DOE NP: Tim Hallman, Chair • ~ 150 GHz scattered electron rate – one of the theory talks by Bill Marciano – Design to flip Pockels cell ~ 2 kHz – 6 panelists: T.W.Donnelly, D.Hertzog, – 80 ppm pulse-to-pulse fluctuations C.Horowitz, Z-T.Lu, M.Perelstein, T. Rizzo • 1 nm control of beam centroid on target – Positive outcome: unique opportunity highlighted, – Novel “slow helicity reversal” methods small theory uncertainty, importance of • > 10 gm/cm2 liquid hydrogen target achieving proposed error bar – 1.5 m: ~ 5 kW @ 85 µA

• Full Azimuthal acceptance; θlab ~ 5 mrad – novel two-toroid spectrometer – radiation hard, highly segmented integrating detectors • Redundant 0.4% beam polarimetry – Pursue both Compton and Atomic Hydrogen techniques

Electrons are Not Ambidextrous 45 Krishna Kumar, November 4 2014 MOLLER is a unique opportunity enabled by the 12 GeV Upgrade MOLLER Summary Cannot be done elsewhere in the world

Commissioning + 3 years (~30 weeks/year)

✦ Scientific Significance ★ Unique observable and among the most sensitive in terms of discovery reach, for flavor- and CP-conserving scattering amplitudes, in the next decade ★ Textbook legacy ✦ Scope of Future Research Effort ★ Purely Leptonic Reaction: theoretical uncertainty already well under control ★ A strong, experienced and motivated group of experimental researchers ✦ Feasibility and Three Year Science Output ★ Evolutionary development of technical capabilities to reach unprecedented sensitivity

Electrons are Not Ambidextrous 46 Krishna Kumar, November 4 2014 Perspective on Future PVES MOLLER, SOLID, P2

Sensitive discovery reach over the next decade ! for CP-/flavor-conserving and LNV scattering amplitudes

✦ If LHC sees ANY anomaly in Runs 2 or 3 (~2022) ★ The unique discovery space probed will become a pressing need, along with other sensitive low energy probes (e.g. g-2 anomaly) ✦ Discovery scenarios beyond LHC signatures ★ Hidden weak scale scenarios ★ Lepton Number Violating Amplitudes ★ Light Dark Matter Mediators ★ …

Electrons are Not Ambidextrous 47 Krishna Kumar, November 4 2014 Summary

✦ Parity-Violating Electron Scattering ★ Enabled unique studies of the weak force ★ Technical progress has enabled unprecedented precision ★ flagship experiments at electron accelerators ✦ Fundamental Nuclear/Nucleon Physics ★ Neutron RMS radii of heavy nuclei (PREX, CREX) ★ valence quark structure of protons and neutrons (SOLID) ✦ Fundamental Electroweak Physics ★ Search for new dynamics at the TeV scale (MOLLER, SOLID, P2) • complementary to colliders; would help interpret potential anomalies! • precision measurement of the weak mixing angle A remarkably productive research program that will continue to flourish over the next decade

Electrons are Not Ambidextrous 48 Krishna Kumar, November 4 2014