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Parity Violation at Jefferson Lab

Parity Violation at Jefferson Lab. Report to the NSAC Subcommittee. September 7, 2012. Kent Paschke University of Virginia. Consider or . δ (sin 2 θ W ) ≤ 0.5% away from the Z resonance. Neutral Currents Beyond the Standard Model. Sensitivity to TeV-scale contact interactions if:.

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Parity Violation at Jefferson Lab

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

  2. Consider or • δ(sin2θW) ≤ 0.5% • away from the Z resonance Neutral Currents Beyond the Standard Model Sensitivity to TeV-scale contact interactions if: Low energy WNC interactions (Q2<<MZ2) Z0 • Precision neutrino scattering • PV couplings through interference with EM • opposite-parity transitions in heavy atoms • parity-violating electron scattering Eichten, Lane and Peskin, PRL50 (1983) mass scaleΛ, couplingg for each fermion and handedness combination Many new physics models require new, heavy, neutral current interactions Heavy Z’s and neutrinos, technicolor, compositeness, extra dimensions, SUSY… NSAC Subcommittee, September 2012 Kent Paschke JLab Parity Violation

  3. E122 (1978) Electromagnetic amplitude interferes with Z-exchange as well as any new physics Proton Weak Form Factors (2000-2011) E158 (2004) QWeak (Jlab, 2010-2012) Parity Violation in Electron Scattering C.Y. Prescott, et al. Weak Charge QW PV in Deep Inelastic Scattering from 2H Elastic e-p and e-N scattering Electron weak vector charge Proton weak vector charge 48 GeV Møller Scattering SAMPLE (Bates), A4 (MAMI), G0 and HAPPEX (JLab) APV ~ 100 ± 10 ppm 1 GeV elastic e-p scattering (gAegVT+β gVegAT) APV = (-131 ± 14 ± 10) ppb • Parity Violation in Weak Neutral Current Interactions • sin2θW = 0.224 ± 0.020: same as in neutrino scattering Probing over a range of low-Q2, strange quark contributions to the form-factors are small (<3%) and consistent with zero. improved by PV-DIS-6 (JLab, 2012) Phys. Rev. Lett.95 081601 (2005) unpolarized target NSAC Subcommittee, September 2012 Kent Paschke JLab Parity Violation

  4. 3 Decades of Technical Progress Parity-violating electron scattering has become a precision tool Interplay between probing hadron structure and electroweak physics SLAC MIT-Bates Mainz Jefferson Lab • Beyond Standard Model Searches • Strange quark form factors • Neutron skin of a heavy nucleus • QCD structure of the nucleon • Pioneering • Proton Form Factors (1999-2009) • Near Future • Future Program For future program: • sub-part per billion statistical reach and systematic control • sub-1% normalization control photocathodes, polarimetry, high power cryotargets, nanometer beam stability, precision beam diagnostics, low noise electronics, radiation hard detectors NSAC Subcommittee, September 2012 Kent Paschke JLab Parity Violation

  5. Improvement in SM prediction E158: First confirmation of SM running Future Program of Precision Weak Charge Measurements Future Running Weak Charge E158 2012 PDG • Czarnecki and Marciano (1995, 2000) • Petriello (2002) • Erler and Ramsey-Musolf (2004) • Sirlin et. al. (2004) • Zykonov (2004) Constraints on new physics into 15 TeV (lepton compositeness) 0.5-2 TeV (Z’, extra dimensions) • 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 Deviation from this SM curve would indicate observation of a new interaction, beyond the SM Z0 NSAC Subcommittee, September 2012 Kent Paschke JLab Parity Violation

  6. A Qweak Proton Weak Charge, QWp Non-perturbative theory g ~ 2πΛ ~ 29 TeV SM value V Extra Z‘ g ~ 0.45 m Z’ ~ 2.1 TeV (expected) Program to study strange quark contribution to the nucleon form-factors Strange Quark FF: shape of curve Proton weak vector charge: projection to Q2 = 0 The strange quark program has led to significant improvement measurement of quark weak vector couplings R. Young et al., PRL 99 122003 (2007) NSAC Subcommittee, September 2012 Kent Paschke JLab Parity Violation

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

  8. Main detector asymmetry in “prompt” monitoring plots 0.2 Proton Weak Charge JLab QWeak Completed run (2010-2012) First results (~5% of data) to be released at DNP Future: MESA/P2 at Mainz 0 -0.2 New ERL complex will also support a high-current extracted beam suitable for a PV measurement of proton weak charge • APV = -20 ppb to 2.1% (0.4ppb) • δ(sin2θW) = 0.2% • Funding approved from DFG • Development starting now • Planned running 2017-2020 NSAC Subcommittee, September 2012 Kent Paschke JLab Parity Violation

  9. Two 0.6 GV linacs Upgrade magnets and power supplies CHL-2 12 GeV Upgrade at JLab 1.1 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 2-11 GeV NSAC Subcommittee, September 2012 Kent Paschke JLab Parity Violation

  10. APV = 35.6 ppb δ(sin2θW) = ± 0.00026 (stat.) ± 0.00012 (syst.) 75 μA 80% polarized ~ 0.1% MOLLER at 11GeV JLab Matches best collider (Z-pole) measurement! Luminosity: 3x1039 cm2/s An ultra-precise measurement of the weak mixing angle using Møller scattering Figure of Merit proportional to beam power At 11 GeV, JLab luminosity and stability makes large improvement possible MOLLER δ(APV) = 0.73 parts per billion δ(QeW) = ± 2.1 % (stat.) ± 1.0 % (syst.) NSAC Subcommittee, September 2012 Kent Paschke JLab Parity Violation

  11. Precision Measurement of sin2θW 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 We failed to nail sin2θW when we had the colliders! -B.Marciano The consistency of the SM prediction, between directly measured mH, mW, mt, sin2θW bears testing • sin2θW improvements at hadron colliders very challenging • “Giga-Z” option of ILC or neutrino factory: powerful but far future NSAC Subcommittee, September 2012 Kent Paschke JLab Parity Violation

  12. Beyond kinetic mixing: introduce mass mixing with Z Complementary to direct heavy photon searches: MOLLER reach: red dashed lines MOLLER Sensitivity to BSM Physics Lifetime/branching ratio model dependence vs mass mixing assumption Heavy Photons: The Dark Sector Heavy Photons (Z): The Dark Sector best contact interaction reach for leptons at low OR high energy Davoudiasl, Lee, Marciano arXiv:1203.2947v2 To do better for a 4-lepton contact interaction would require: Giga-Z factory, linear collider, neutrino factory or muon collider Hypothesis could explain (g-2)μ discrepancy as well as several intriguing astrophysical anomalies related to dark matter NSAC Subcommittee, September 2012 Kent Paschke JLab Parity Violation

  13. Meeting the Challenges of MOLLER Unprecedented Precision • ~ 150 GHz scattered electron rate (80ppm at 2kHz) • 100% Azimuthal acceptance, with θlab ~ 5-15 mrad • Robust and redundant 0.4% beam polarimetry • 1 nm control of beam centroid on target • > 10 gm/cm2 target needed ee’s ep’s Preparations on Track • 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 NSAC Subcommittee, September 2012 Kent Paschke JLab Parity Violation

  14. PV-DIS with 2H This box matches the scale of the C1q plot Red ellipses are PDG fits A SOLID: C1q, C2q in Deep Inelastic Scattering V 11 GeV PVDIS Blue bands represent expected data: Qweak (left) and PV-DIS-6GeV (right) Qweak V Green bands are the proposed measurement of PV-DIS (SOLID) A E122 SAMPLE Cs PV-DIS-6 PDG PDG NSAC Subcommittee, September 2012 Kent Paschke JLab Parity Violation

  15. SOLID QCD and Hadronic Structure in PV-DIS Measure Ad in narrow bins of x, Q2 with 0.5% precision • Large acceptance spectrometer based on large solenoid (e.g. CLEO) • High luminosity • Tracking, calorimetry, Cerenkov detectors • Precision polarimetry Q2[GeV2] 4 months at 11 GeV 2 months at 6.6 GeV Statistical error bar σA/A(%) shown at center of bins in Q2,x xBj Charge Symmetry Violation Higher Twist • cancellations isolate effects to coherent operator: Diquarks! • HT thumbprint (increase with x, Q2) should be clear if it is significant • Direct sensitivity of parton-level CSV • Important implications for PDF’s • Could be partial explanation of the NuTeV anomaly Strategy: requires precise kinematics and broad range Variations over x, Q2 can discriminate QCD effects and new physics NSAC Subcommittee, September 2012 Kent Paschke JLab Parity Violation

  16. Deuterium PV-DIS drives the need for SoLID, but it also supports a broad program of hadronic studies Leptophobic Z’ SoLID would fill a unique corner of parameter space Since electron vertex must be vector, the Z’ cannot couple to the C1q’s if there is no electron coupling: can only affect C2q’s Transverse Spin Structure arXiv:1203.1102v1 Buckley and Ramsey-Musolf semi-inclusive DIS from polarized targets • Leptophobic Z’ as light as 120 GeV could have escaped detection d/u PV-DIS on proton J/ΨProduction No other technique can provide comparable precision on axial hadronic weak neutral currents NSAC Subcommittee, September 2012 Kent Paschke JLab Parity Violation

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

  18. Since 2007: MOLLER at JLab SOLID at JLab P2 at Mainz Summary: Compelling new opportunities in PVeS • Ultra-precise weak-mixing angle comparable to the best collider measurements, needed and unavailable anywhere else! • TeV-scale BSM sensitivity to complement LHC • Factor of two and low Q2 available on Qwp • Extend precision and improved interpretation • 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 • 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 JLab provides unique capabilities that enable a compelling program of high precision studies of parity violation in electron scattering NSAC Subcommittee, September 2012 Kent Paschke JLab Parity Violation

  19. Backups

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

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

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

  23. GEM Sashlyk gas Cerenkov collimator SoLID Design for PVDIS Physics • 20o - 35o, E’~ 1.5 - 5 GeV, δp/p ~ 2% • some regions 10’s of kHz/mm2, Pion rejection with Cerenkov + segmented calorimeter • Several large solenoids would work (Zeus, Babar): present design focuses on CLEO

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

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

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