Parity Violation at Jefferson Lab Kent Paschke University of Virginia Kent Paschke University of Virginia September 7, 2012 Report to the NSAC Subcommittee

2 Kent PaschkeJLab Parity Violation NSAC Subcommittee, September 2012 Neutral Currents Beyond the Standard Model mass scale Λ, coupling  f or each fermion and handedness combination Eichten, Lane and Peskin, PRL50 (1983) Consider or Heavy Z’s and neutrinos, technicolor, compositeness, extra dimensions, SUSY… Many new physics models require new, heavy, neutral current interactions Sensitivity to TeV-scale contact interactions if: δ (sin 2 θ W ) ≤ 0.5% away from the Z resonance opposite-parity transitions in heavy atoms parity-violating electron scattering Precision neutrino scattering PV couplings through interference with EM Z0Z0 Low energy WNC interactions (Q 2 <<M Z 2 )

3 Kent PaschkeJLab Parity Violation NSAC Subcommittee, September 2012 Parity Violation in Electron Scattering Electromagnetic amplitude interferes with Z-exchange as well as any new physics unpolarized target (g A e g V T +  g V e g A T ) Weak Charge Q W E158 (2004) 48 GeV Møller Scattering Phys. Rev. Lett (2005) A PV = (-131 ± 14 ± 10) ppb Electron weak vector charge QWeak (Jlab, ) Proton weak vector charge 1 GeV elastic e-p scattering SAMPLE (Bates), A4 (MAMI), G0 and HAPPEX (JLab) Proton Weak Form Factors ( ) Probing over a range of low-Q 2, strange quark contributions to the form-factors are small (<3%) and consistent with zero. Elastic e-p and e-N scattering A PV ~ 100 ± 10 ppm Parity Violation in Weak Neutral Current Interactions sin 2 θ W = ± 0.020: same as in neutrino scattering C.Y. Prescott, et al. E122 (1978) improved by PV-DIS-6 (JLab, 2012) PV in Deep Inelastic Scattering from 2 H

4 Kent PaschkeJLab Parity Violation NSAC Subcommittee, September Decades of Technical Progress photocathodes, polarimetry, high power cryotargets, nanometer beam stability, precision beam diagnostics, low noise electronics, radiation hard detectors Beyond Standard Model Searches Strange quark form factors Neutron skin of a heavy nucleus QCD structure of the nucleon SLAC MIT-Bates Mainz Jefferson Lab sub-part per billion statistical reach and systematic control sub-1% normalization control Parity-violating electron scattering has become a precision tool Interplay between probing hadron structure and electroweak physics For future program: Pioneering Proton Form Factors ( ) Near Future Future Program

5 Future 2012 PDG Kent PaschkeJLab Parity Violation NSAC Subcommittee, September 2012 Running Weak Charge Czarnecki and Marciano (1995, 2000) Petriello (2002) Erler and Ramsey-Musolf (2004) Sirlin et. al. (2004) Zykonov (2004) Improvement in SM prediction E158: First confirmation of SM running Constraints on new physics into 15 TeV (lepton compositeness) TeV (Z’, extra dimensions) E158 Deviation from this SM curve would indicate observation of a new interaction, beyond the SM Z 0 Future Program of Precision Weak Charge Measurements Elastic Electron-Proton Scattering Moller Scattering Deep Inelastic Scattering off Deuterium Each tests different couplings and plays a role in constraining/detailing possible BSM physics

6 Qweak A V SM value The strange quark program has led to significant improvement measurement of quark weak vector couplings Kent PaschkeJLab Parity Violation NSAC Subcommittee, September 2012 Proton Weak Charge, Q W p R. Young et al., PRL (2007) Program to study strange quark contribution to the nucleon form-factors (expected) Strange Quark FF: shape of curve Proton weak vector charge: projection to Q 2 = 0 g ~ 0.45 m Z’ ~ 2.1 TeV g ~ 0.45 m Z’ ~ 2.1 TeV g ~ 2π Λ ~ 29 TeV Extra Z‘ Non-perturbative theory

7 Kent PaschkeJLab Parity Violation NSAC Subcommittee, September 2012 QWeak at JLab Designed with CFD simulation Boiling <40ppm at 180 μA (about 3% excess noise) 2300 Watts World’s highest power cryotarget New Hall C Compton Polarimeter Polarization, measured through Compton and Moller preliminary “internal consumption only” Width 236 ppm at 240 Hz Integrating Main Detector 5 GHz total rate Integrating Main Detector 5 GHz total rate 1 ppm precision in 4 minutes

8 Kent PaschkeJLab Parity Violation NSAC Subcommittee, September 2012 Proton Weak Charge Main detector asymmetry in “prompt” monitoring plots Run II Beam Properties Δx-0.95 nm Δy-0.24 nm Δx’-0.07 nrad Δy’-0.06 nrad A Energy 0.23 ppb Future: MESA/P2 at Mainz A PV = -20 ppb to 2.1% (0.4ppb) δ(sin 2 θ W ) = 0.2% New ERL complex will also support a high- current extracted beam suitable for a PV measurement of proton weak charge Funding approved from DFG Development starting now Planned running JLab QWeak Completed run ( ) First results (~5% of data) to be released at DNP

9 Kent PaschkeJLab Parity Violation NSAC Subcommittee, September GeV Upgrade at JLab 2-11 GeV Two 0.6 GV linacs 1.1 CHL-2 Upgrade magnets and power supplies Enhanced capabilities in existing Halls Lower pass beam energies still available 12 GeV for Hall D Unique Facility for PVeS High intensity High polarization Low noise (cold CW RF) Energy range Unique Facility for PVeS High intensity High polarization Low noise (cold CW RF) Energy range

10 Kent PaschkeJLab Parity Violation NSAC Subcommittee, September 2012 MOLLER at 11GeV JLab Figure of Merit proportional to beam power At 11 GeV, JLab luminosity and stability makes large improvement possible δ(Q e W ) = ± 2.1 % (stat.) ± 1.0 % (syst.) δ(A PV ) = 0.73 parts per billion A PV = 35.6 ppb Luminosity: 3x10 39 cm 2 /s 75 μA80% polarized MOLLER δ(sin 2 θ W ) = ± (stat.) ± (syst.)~ 0.1% Matches best collider (Z-pole) measurement! An ultra-precise measurement of the weak mixing angle using Møller scattering

11 Kent PaschkeJLab Parity Violation NSAC Subcommittee, September 2012 Precision Measurement of sin 2 θ W Direct measurement of SM weak mixing angle is average of two measurements that disagree by 3σ......yet the naive statistical average agrees to a very high level with the LHC Higgs candidate The consistency of the SM prediction, between directly measured m H, m W, m t, sin 2 θ W bears testing sin 2 θ W improvements at hadron colliders very challenging “Giga-Z” option of ILC or neutrino factory: powerful but far future We failed to nail sin 2 θ W when we had the colliders! -B.Marciano

Kent PaschkeJLab Parity Violation NSAC Subcommittee, September 2012 MOLLER Sensitivity to BSM Physics best contact interaction reach for leptons at low OR high energy To do better for a 4-lepton contact interaction would require: Giga-Z factory, linear collider, neutrino factory or muon collider Heavy Photons: The Dark Sector Heavy Photons (Z): The Dark Sector Hypothesis could explain (g-2) μ discrepancy as well as several intriguing astrophysical anomalies related to dark matter Beyond kinetic mixing: introduce mass mixing with Z arXiv: v2DavoudiaslDavoudiasl, Lee, Marcianoiano Complementary to direct heavy photon searches: Lifetime/branching ratio model dependence vs mass mixing assumption MOLLER reach: red dashed lines

13 Kent PaschkeJLab Parity Violation NSAC Subcommittee, September 2012 Meeting the Challenges of MOLLER ~ 150 GHz scattered electron rate (80ppm at 2kHz) 100% Azimuthal acceptance, with θ lab ~ 5-15 mrad Robust and redundant 0.4% beam polarimetry 1 nm control of beam centroid on target > 10 gm/cm 2 target needed Strong Collaboration being formed with international participation JLab Director’s Review (chair: C. Prescott) gave strong endorsement Conceptual design and cost range being developed (~ 20M$) Funding proposal has been submitted to DoE ~3 years construction, aim to complete data collection in 2020 Unprecedented Precision Preparations on Track ee’s ep’s

14 SAMPLE E122 PDG PV-DIS-6 Kent PaschkeJLab Parity Violation NSAC Subcommittee, September 2012 SOLID: C 1q, C 2q in Deep Inelastic Scattering Cs 11 GeV PVDIS Qweak A V V A PDG This box matches the scale of the C 1q plot PV-DIS with 2 H Red ellipses are PDG fits Green bands are the proposed measurement of PV-DIS (SOLID) Blue bands represent expected data: Qweak (left) and PV-DIS-6GeV (right)

15 Kent PaschkeJLab Parity Violation NSAC Subcommittee, September 2012 Direct sensitivity of parton-level CSV Important implications for PDF’s Could be partial explanation of the NuTeV anomaly Charge Symmetry ViolationHigher Twist QCD and Hadronic Structure in PV-DIS Strategy: requires precise kinematics and broad range Variations over x, Q 2 can discriminate QCD effects and new physics Q 2 [GeV 2 ] x Bj Measure A d in narrow bins of x, Q 2 with 0.5% precision Statistical error bar σ A /A(%) shown at center of bins in Q 2,x 4 months at 11 GeV 2 months at 6.6 GeV SOLID Large acceptance spectrometer based on large solenoid (e.g. CLEO) High luminosity Tracking, calorimetry, Cerenkov detectors Precision polarimetry cancellations isolate effects to coherent operator: Diquarks! HT thumbprint (increase with x, Q 2 ) should be clear if it is significant

16 Kent PaschkeJLab Parity Violation NSAC Subcommittee, September 2012 SoLID would fill a unique corner of parameter space d/u PV-DIS on proton semi-inclusive DIS from polarized targets Transverse Spin Structure Deuterium PV-DIS drives the need for SoLID, but it also supports a broad program of hadronic studies J/Ψ Production No other technique can provide comparable precision on axial hadronic weak neutral currents Since electron vertex must be vector, the Z’ cannot couple to the C 1q ’s if there is no electron coupling: can only affect C 2q ’s Leptophobic Z’ as light as 120 GeV could have escaped detection Leptophobic Z’ arXiv: v1 Buckley and Ramsey-Musolf

17 Kent PaschkeJLab Parity Violation NSAC Subcommittee, September 2012 Fundamental Symmetries at an EIC Hadronic physics: Novel γ Z structure functions polarized electron, unpolarized hadron unpolarized electron, polarized hadron e-e- p, D, 3 He BSM: Search for Lepton Flavor Violation e→ τ BaBar limits tau decay (quark flavor diagonal) EIC can go beyond HERA limits on search for neutrinoless τ production and competes with super-B factory e-e- p, D, 3 He proton deuteron There are 15 different structure function combinations that can be measured (EM, γZ, W) Inclusive cross-check of semi-inclusive Δs extraction

18 Kent PaschkeJLab Parity Violation NSAC Subcommittee, September 2012 Summary: Compelling new opportunities in PVeS Since 2007: New constraint on quark vector weak charges (Completion of Strange quark program) (First electroweak observation of neutron skin in a heavy nucleus) Successfully completed PV-DIS-6 running (results soon!) Successfully completed QWeak running MOLLER at JLab Ultra-precise weak-mixing angle comparable to the best collider measurements, needed and unavailable anywhere else! TeV-scale BSM sensitivity to complement LHC SOLID at JLab Unique access to axial weak hadronic coupling tests un-illuminated corner of BSM parameter space Broad program of hadronic studies: high-x partonic structure, transverse spin structure, nuclear modification, QCD studes P2 at Mainz Factor of two and low Q 2 available on Q w p Extend precision and improved interpretation JLab provides unique capabilities that enable a compelling program of high precision studies of parity violation in electron scattering

Backups

Complementarity to LHC Direct Searches Virtually all GUT models predict new Z’s For ‘light’ 1-2 TeV, Z’ properties can be extracted Suppose a 1 to 2 TeV heavy Z’ is discovered at the LHC Can we point to an underlying GUT model? J. Erler and E. Rojas MSSM sensitivity if light super- partners, large tanβ MSSM Ramsey-Musolf and Su, Phys. Rep. 456 (2008) RPV SUSY Doubly-charged Scalars improves reach significantly beyond LEP-200

High Sensitivity, Complementary to LHC Moller sensitivity: With mass, width, and A FB can get constraint on e R /e L Figure: F. Petriello & S. Quackenbush Moller: LHC: Best current limits on 4-electron contact interactions: LEPII at 200 GeV (Average of all 4 LEP experiments) insensitive toOR To do better for a 4-lepton contact interaction would require: Giga-Z factory, linear collider, neutrino factory or muon collider

22 Kent PaschkeJLab Parity Violation NSAC Subcommittee, September 2012 PVeS Program and SUSY Qweak P2 MOLLER SOLID Ramsey-Musolf and Su, Phys. Rep. 456 (2008) Complementary sensitivity to SUSY MSSM sensitivity if light super- partners, large tanβ MSSM Ramsey-Musolf and Su, Phys. Rep. 456 (2008) RPV SUSY

SoLID Design for PVDIS Physics 20 o - 35 o, E’~ GeV, δp/p ~ 2% some regions 10’s of kHz/mm 2, Pion rejection with Cerenkov + segmented calorimeter Several large solenoids would work (Zeus, Babar): present design focuses on CLEO GEM Sashlyk gas Cerenkov collimator

24 Kent PaschkeJLab Parity Violation NSAC Subcommittee, September 2012 Charge Symmetry Violation We already know CSV exists:  u-d mass difference δm = m d -m u ≈ 4 MeV δM = M n - M p ≈ 1.3 MeV  electromagnetic effects For A PV in electron- 2 H DIS Direct sensitivity of parton-level CSV Important implications for PDF’s Could be partial explaination of the NuTeV anomaly δd δu bag model (solid) Radionov et al. QED splitting (dashed) Glueck et al. x Sensitivity will be enhanced if u+d falls off more rapidly than δu-δd as x → 1 Significant effects are predicted at high x

CSV in Heavy Nuclei: EMC Effect 5%  Mean Field approach to estimate an EMC- like effect for N ≠ Z nuclei  Possible explanation for NuTeV anomaly which used iron target. visible at 5% level in PV-DIS