Sin 2 q W = 0.238 q W = 29,2 ° Future PVES Experiments: New, high precision measurements of the weak mixing angle sin 2 θ W q W Frank Maas (Helmholtz Institute Mainz, Institute for Nuclear Phyiscs, PRISMA cluster of excellence Johannes Gutenberg University Mainz) “The Electroweak Box Workshop”, Amherst Center for Fundamental Interactions September 428-30, 2017
Search for New Physics: Various Methods High Energy (LHC) High Intensity High Precision (B-decays) ((g-2) µ , EDM, sin 2 q W , …) (at low energy)
Direct observation versus precision measurements: top-quark Direct measurement Precision measurements
P2
The role of the weak mixing angle The relative strength between the weak and electromagnetic interaction is determined by the weak mixing angle: sin 2 (θ W ) Q W (p) = 1 – 4 sin 2 θ W Q e (p) = +e electric charge of the proton weak charge of the proton sin 2 θ W : a central parameter of the standard model
P2 (Mainz/MESA)
„running “ sin 2 θ eff or sin 2 θ W (µ)
Precision measurements and quantum corrections: running sin 2 θ W (µ) running α Universal quantum corrections: can be absorbed into a scale dependent, „running “ sin 2 θ eff or sin 2 θ W (µ)
0.245 QW (p) NuTeV QW (e) 0.24 P2@MESA Qweak Moller SOLID 0.235 QW (APV ) LEP1 ATLAS eDIS Tevatron 0.23 SLD 3 % sin 2 θ W (Q) CMS 0.225 hs 0.0001 0.001 0.01 0.1 1 10 100 1000 10000 Q [GeV]
Sensitivity to new physics beyond the Standard Model
Sensitivity to new physics beyond the Standard Model Mixing with New Extra Z Dark photon or Contact interaction Fermions Dark Z
Dark Photon, Z-Boson
New massive force carrier of extra U(1) d gauge group; predicted in almost all string compactifications Dark photon LHC 10 -6 10 -2 10 6 10 9 10 11 10 13 Mass [eV] a ¢ = e 2 2 · a em Axion W’, Z’ Search for the O(GeV/c 2 ) mass scale in a world-wide effort Ø Could explain large number of astrophysical anomalies Arkani-Hamed et al. (2009) Andreas, Ringwald (2010); Andreas, Niebuhr, Ringwald (2012) Ø Could (have) explained presently seen deviation of >3 s between (g-2) μ Standard Model prediction and direct (g-2) μ measurement Pospelov(2008)
Status 2011 10 -2 (g-2) e vs. α (g-2) µ BaBar e + e − →γ µ + µ − Coupling KLOE Mixing Parameter ε |(g-2) µ |< 2 σ 10 -3 allowed parameter range for Dark Photon explanation of (g-2) μ E774 E141 10 -4 10 100 1000 Dark Photon Mass m γ ’ (MeV/c 2 ) Mass
H. Davoudiasl, W. Marciano
Running sin 2 θ W and Dark Parity Violation Possible P2 Q 2 -Range Bill Marciano
Running sin 2 θ W and Dark Parity Violation H. Davoudiasl, W. Marciano
Weak Charge Of Proton: Qweak (Jlab), P2 (MESA) Weak Weak Charge Charge Of Of Quarks: Electron: SOLID MOELLER (PVDIS) (JLAB) (JLAB)
The role of the weak mixing angle The relative strength between the weak and electromagnetic interaction is determined by the weak mixing angle: sin 2 (θ W ) Q W (p) = 1 – 4 sin 2 θ W Q e (p) = +e electric charge of the proton weak charge of the proton sin 2 θ W : a central parameter of the standard model
Proton: special case 1 – 4 sin 2 θ W Proton Weak charge: Q W (p) = 4 D sin 2 θ W D Q W (p) Error: = = 4/( (1/sin 2 θ W ) – 4 ) ( D sin 2 θ W /sin 2 θ W ) D Q W (p)/Q W (p) Rel. error: D sin 2 θ W /sin 2 θ W = ( (1/sin 2 θ W ) – 4 ) /4 D Q W (p)/Q W (p) Rel. error sin 2 θ W (50 MeV) Example: = 0.238 4/( (1/sin 2 θ W ) – 4 ) ~ 20 D Q W (p)/Q W (p) = 2% from Experiment D sin 2 θ W /sin 2 θ W = 0.1 % same precision as LEP, SLAC Neutron Weak charge: = D sin 2 θ W /sin 2 θ W D Q W (p)/Q W (n)
Jens Erler
Experimental Method: Parity Violating Electron Scattering
Parity Violating Asymmetry in elastic electron proton scattering σ ≈ (V-A) e (V-A) p A e V p +V e A p V-A coupling: parity-violating cross section asymmetry A LR longitudinally pol. electrons unpolarised protons
Parity violating cross section asymmetry tracking system weak charge polarisation measurement hadron structure
• Contributions to D sin² Q W for 35° central scattering angle, E=150 MeV, 10000 h of data taking
P2-Precision in sin 2 θ W Δsin 2 θ W = 3.6 10 -4 (0.13 %) Beam energy and luminosity needs further optimization S. Baunack, D. Becker and P. Larin Frank Maas, Teilchenphysikkolloquium, Heidleberg, Feb. 5, 2013
Conceptually very simple experiments A = (N + -N - )/(N + +N - ) D A = (N + +N - ) -1/2 = N -1/2 2% Measurement N = 6.25 x 10 18 events A = 20 x 10 -9 Highest rate, measure Q 2 : Large Solid Angle Spectrometers
Apparative (false) asymmetries: Extreme good control of beam and target Flip Helicity fast Extra spin flip
PVeS Experiment Summary 100% Pioneering 10% Strange Form Factor (1998-2009) -4 S.M. Study (2003-2005) 10 JLab 2010-2012 Future E122 1% -5 PVDIS-6 10 G0 Mainz-Be H-I SAMPLE SOLID -6 10 A4 G0 ) PV MIT-12C A4 H-III (A A4 H-He -7 δ 10 H-II PREX-I E158 PREX-II -8 10 Qweak MESA-12C -9 10 Moller Kent Paschke MESA-P2 -10 10 -8 -6 -5 -3 -7 -4 10 10 10 10 10 10 A PV
Counting Technique
Analogue Technique Measure Flux of Scattered electrons: - no pile-up (double count losses) - sensitive to small electr. fields. - no separation of phys. process
Qweak (1GeV) @ Jlab P2@MESA (0.150 GeV) @ Mainz Proton weak charge (4%) Proton weak charge (1.7%) Toroid spectrometer Solenoid spectrometer SOLID (PVDIS 11GeV) @ Jlab Quark weak charge Moeller (11GeV) @ Jlab Solenoid spectrometer Electron weak charge Toroid Spectrometer
P2-experimental setup Magnetic field 0.6 T P2-experiment: Magnetic solenoid spectrometer (0.6 T) with integrating detectors Superconducting magnet, 0.6 T 100 Detectors, Fused silica (“quartz”) e - beam, 150 µA PMT readout e - beam, 150 µA 3.7 m 100 Detectors, Fused silica (“quartz”) 13 t lead PMT readout 13 t lead 60 cm liquid H target collimator 3.7 m 60 cm liquid H target collimator
MESA accelerator new, Mainz Energy Recovering Acc. Beam Dump Magnetic spectrometer MAGIX Parity violation experiment P2
• Parity violating electron scattering: “Low energy frontier” comprises a sensitive test of the standard model complementary to LHC • Determination of sin 2 ( q W ) with high precision (same as Z-pole) • P2-Experiment (proton weak charge) in Mainz under preparation New MESA energy recovering accelerator at 155 MeV, target precision is 1.7% in Qweak i.e. 0.13% in sin 2 ( q W ), Sensitivity to new physics up to a scale of 49 TeV • Much more physics from PV electron scattering • Together with Moeller@Jlab (electron weak charge) and SOLID@Jlab (quark weak charge) very sensitive test of standard model and possibility to narrow in on Standard Model Extension
Other Measurements: Carbon, Lead
P2: Funding PRISMA “Forschungsbau”: Detector system (quartz-based) including electronics 2.0 M€ Solenoid magnet 1.5 M€ He-refrigerator for the hydrogen target 1.7 M€ University (through “Großgeräte”) Silicon tracker system for Q 2 -measurement development 0.5 M€ Enhanced sensitivity Double Wien filter for MESA 0.4 M€ To new physics Hydro-Moeller detector system 0.4 M€ Hydrogen target system 0.35 M€
P2: Funding Measurement of neutron distribution in nuclei deceisive for Neutron star properties PRISMA “Forschungsbau”: Detector system (quartz-based) including electronics 2.0 M€ Solenoid magnet 1.5 M€ He-refrigerator for the hydrogen target 1.7 M€ University (through “Großgeräte”) Silicon tracker system for Q 2 -measurement development 0.5 M€ Double Wien filter for MESA 0.4 M€ Hydro-Moeller detector system 0.4 M€ Hydrogen target system 0.35 M€
Yuxiang Zhao (SBU)
MESA: Beam parameter
Parity violating cross section asymmetry weak charge hadron structure Important input from other projects (S1, S3)
Polarimetry (<0.5%)
The double scattering Mott polarimeter: Mott Polarimeter: A. Gellrich and J. Kessler, Phys. Rev. A 43, 204 (1991) - Measuring left/right asymetry to calculate spin polarisation - Analysing power of target foils has to be extrapolated Double Scattering Polarimeter (DSP): - Analysing power of the targets can be calculated directly from measurements - Allows for higher precision measurement of spin polarisation - Invasive polarimetry at the electron source - Scattering chamber in operation, first double scattering data
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