Recent results and future direction of the parity-violating electron scattering program in Hall A at Jefferson Lab

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1 Recent results and future direction of the parity-violating electron scattering program in Hall A at Jefferson Lab, University of Virginia For the HAPPEX, PREX, PVDIS, MOLLER and SOLID Collaborations SPIN, Dubna 0 September 0

2 Parity Violating Electron Scattering / A + A weak A +A A weak interference between neutral weak and electromagnetic amplitudes Polarized e - Source Hall A pseudo-random Change helicity of beam - equivalent to changing parity Spin 0, Dubna

3 Absolute uncertainty PVES Experiments st generation nd generation 3rd generation 4th generation Relative uncertainty Asymmetry size Spin 0, Dubna 3

4 Absolute uncertainty PVES Experiments st generation nd generation 3rd generation 4th generation Relative uncertainty Jefferson Lab, Hall A Experiments Standard Spectrometers New Apparatus Asymmetry size Spin 0, Dubna 4

5 Hall A Parity - Standard Setup 3 Data Quality Checks 3. Detector Acceptances Detector acceptances are checked to ensure that the detector is well aligned and not imposing geometric cut to skew the Q. The top two plots in Fig. 3. are S0 triggered plots, and the bottom two are detector triggered plots. The S0 paddles are much bigger than the detector and covers the entire detector plane. The detector x/y distribution plots with detector triggers look identical to the S0 triggered plots, indicating that the detector does not impose any geometric cuts on the acceptance. Elastic Inelastic detector LHRS Detector Plane Dist. -3! Quad !0 Detector Plane y (m) Detector Plane x (m) Detector Plane x (m) Dipole ! Detector Plane x (m) Detector Plane x (m)..4 Entries e+07 RHRS Detector Plane Dist. RMS S0 Trigger Dist. LHRS Detector Plane 50 Lead - Lucite Cerenkov Shower Calorimeter phototube current integrated over fixed ;me periods 50 S0 Trigger Detector Plane y (m) 0-00 Q Q Detector Plane y (m) Detector Plane y (m) 00 target RHRS Detector Plane Dist. -3!0 50 Psuedo-random, -50 rapid helicity flip 0-00 det Trigger Detector Plane x (m) Detector Plane x (m)..4 0 det Trigger Detector Plane x (m) Detector Plane 0 precision x (m) hundreds of times a second..4 Figure 3.: Detector acceptance plots with S0 and detector triggers. The bounding box is the outline of the detector with the PMT located at about.m in x. The cuts used to generate these plots are -0&& LHRS::"P.hapadcL>550 && L.tr.n== abs(extgtcor_l.th)<0.07 && abs(extgtcor_l.ph)<0.07 && abs(extgtcor_l.dp)<0.05" parts per million RHRS::"P.hapadcR>700 && R.tr.n== && abs(extgtcor_r.th)<0.07 && abs(extgtcor_r.ph)<0.07 && abs(extgtcor_r.dp)<0.05" Spin 0, Dubna 5

6 Polarization enters result directly A PV = A raw P e Precision must be better than statistics Technical Challenges V. Tvaskis DLNP building, Thursday6:50 Resonant cavity photon target, up to kw intensity Beam false asymmetries must be kept small X position difference ± 0.53 nm RMS =.77 µm Y position difference ±.83 nm RMS = 9.50 µm Currently we achieve ~nm position differences and <nrad angle differences HAPPEX 50 II micron micron X angle difference 0 Y angle difference These need to be improved for future experiments! !0.6 ± 0.4 nrad RMS =.3 µrad ± 0.5 nrad RMS =.9 µrad µ rad Spin 0, Dubna 6

7 Strange Quarks in the Nucleon Strange quarks exist in the nucleon at short distance scales. G p E = 3 Gu,p E G n E = 3 Gu,n E 3 Gd,p E 3 Gd,n E Use charge symmetry -> three equations and three unknowns 3 Gs E 3 Gs E How do they influence the interactions of the nucleon? Momentum ~ 4% 0 x(s + s)dx N s s N Mass 0-30%, N Measuring neutral weak proton form-factor (using Parity Violation) enables separation of up, down and strange contributions Spin % s Spin 0, Dubna 7

8 s GE World Data Zhu constraint is used for axial form-factor Form Factor error: precision of EMFF (including γ) and Anapole correction Significant systematic uncertainty in higher Q points G0 (extrapolated) HAPPEX H 4 HAPPEX He Q At Q ~ 0. GeV, G s < few percent of G p ~ 0. GeV A4 SAMPLE with G A calculation M + G s s G E % 95% HAPPEX-III G0 (FORWARD) HAPPEX-H MAMI A4 (different ) % (G + G Q Worldwide Program p E Q ~ 0. p M ) s GE FormFactor error G0 correlated error Leading moment fit 68.3% 95% G0-backward ( H) Q ~ 0.6 HAPPEX-3 G0-forward s GM G s M Spin 0, Dubna 8

9 HAPPEX Program Taken alone is a stringent constraint on the strange quark form factor. High precision, small systematic error, Clean theoretical interpretation Phys. Rev. Lett. 08, 000 (0) HAPPEX-III (0) s G +0.5G E s M Q = 0.64 GeV Phys.Rev.Lett. 8 (999) HAPPEX-I (999) s GE +0.39G s M Q = GeV Phys.Rev.Lett. 98 (007) 0330 HAPPEX-II (006) s G +0.09G E s M Q = 0.07 GeV Phys.Rev.Lett. 96 (006) 0003 HAPPEX-II He (006) s GE Q = GeV A PV - A NS / A NS Spin 0, Dubna 9

10 Weak Charge Distribution of Heavy Nuclei Nuclear theory Neutron distribution is not accessible predicts a neutron to the charge-sensitive photon. skin on heavy nuclei knowledge of neutron densities comes primarily from hadron scattering => model-dependent interpretation Parity Violation can measure weak form factor model independently proton neutron Electric charge 0 γ M EM = 4πα Q F p Q ( ) [ ( ) F ( n Q )] M NC PV = G F ( 4sin θ W )F p Q Weak charge ~0.08 A PV G F Q 4πα ( ) ( ) F n Q F p Q Spin 0, Dubna 0

11 A crucial calibration point for nuclear theory The single measurement of Fn translates to a measurement of Rn via mean-field nuclear models and measuring R N pins down the symmetry energy Skyrme covariant meson covariant point coupling 0.35 F n (Q )/N ( R.J. Furnstahl ) r n in 08 Pb (fm) Rn calibrates the EOS of neutron rich matter - provides an important calibration point for nuclear theory and description of neutron stars r n! r p (fm) Skyrme relativistic meson relativistic point coupling symmetry energy a 4 (MeV) Spin 0, Dubna

12 PREX Lead Radius Experiment First electroweak observation of the neutron skin of a heavy nucleus (CL=95%) Q ~ 0.0 GeV 5 o sca'ering angle A PV ~ 0.6 ppm Rate ~.5 GHz Spin 0, Dubna

13 Recent R n Predic+ons Can Be Tested By PREX at Full Precision PREX could provide an electroweak complement to Rn predictions from a wide range of physical situations and model dependencies Hebeler Steiner Tamii Tsang PREX-II proposal Recent Rn predictions: Hebeler et al. Chiral EFT calculation of neutron matter. Correlation of pressure with neutron skin by Brown. Three-neutron forces! Steiner et al. X-Ray n-star mass and radii observation + Brown correlation. (Ozel et al finds softer EOS, would suggest smaller Rn). Tamii et al. Measurement of electric dipole polarizability of 08 Pb + model correlation with neutron skin. Tsang et al. Isospin diffusion in heavy ion collisions, with Brown correlation and quantum molecular dynamics transport model. These can be tested with δ(a PV )/A PV ~ 3% δ(r n )/R n ~ % Spin 0, Dubna

14 PREX II Future Studies Complimentary measurements CREX 48 Ca at E =.0 GeV and θ = 5 Q = GeV Rn measured to 0.06 fm (.0%) APV ~ 0.6 ppm better approximation of infinite nuclear matter 48 Ca at E =. GeV and θ = 4 Q = 0.0 GeV Rn measured to 0.03 fm (0.9%) APV ~ ppm larger asymmetry can use higher Q and energy microscopic models available constrain 3-neutron forces ( 3 He, 3 H and p-d scattering for 3-nucleon forces) density dependence of the symmetry energy of neutron rich nuclear matter data as input for: neutron star structure, heavy ion collisions and atomic parity violation Spin 0, Dubna 4

15 Nuclear Parameter Correlations strong correlation between RN and the pressure of neutron matter densities near 0. fm 3 constrains the equation of state of neutron matter Combined experiments reduce uncertainty EOS Spin 0, Dubna 5

16 Neutral Current Beyond the SM Many new physics models require new, heavy, neutral current interac;ons L = L SM + L new Heavy Z s and neutrinos, technicolor, compositeness, extra dimensions, SUSY Low energy WNC interactions (Q <<M Z ) Z 0 Consider f f f f or f f f f L f f = i,j=l,r (g ij ) ij f i µ f i fj µ f j Eichten, Lane and Peskin, PRL50 (983) mass scale Λ, coupling g for each fermion and handedness combina6on Sensi6vity to TeV- scale contact interac6ons if: Precision neutrino sca'ering PV couplings through interference with EM δ(sin θw) 0.5% away from the Z resonance opposite- parity transi6ons in heavy atoms parity- viola6ng electron sca'ering Spin 0, Dubna 6

17 PV Electron-Quark Scattering A PV = G F Q 4 (ge Ag T V + g e V g T A) A V V A Small scattering angles Large scattering angles QWeak APV Cs SOLID Scattering from a quark directly (DIS) avoids large radiative corrections. SOLID Spin 0, Dubna 7

18 PV Electron-Quark Scattering A PV = G F Q 4 (ge Ag T V + g e V g T A) A V V A Small scattering angles Large scattering angles Scattering from a quark directly (DIS) avoids large radiative corrections. SOLID Figure: R.Young Spin 0, Dubna 8

19 PV-DIS 6 GeV C couplings consistent with SM and allowed region considerably diminished. Extracted with SM value of C Higher Twist consistent with zero in this result SAMPLE PV-DIS SLAC PDG preliminary rad. corr. in progress SLAC Q =.9 GeV preliminary rad. corr. in progress Spin 0, Dubna 9

20 SOLID (PV-DIS) parity-violation in the deep inelastic scattering of electrons from D. Unique beyond the Standard Model (SM) search. sensitive to axial-hadronic currents, INSENSITIVE to unknown radiative corrections. Charge Symmetry violation (CSV) at the quark level. 3. higher-twist (HT) effects in the parity-violating asymmetry from quark-quark correlations. 4. Measure the d/u ratio in the proton, no nuclear corrections. 5. CSV is induced in heavier nuclei, implications for our understanding of the EMC effect. Ultra precise measurement 4 months GeV months 6.6 GeV Spin 0, Dubna 0

21 SOLID Technical 0 o - 35 o, E ~.5-5 GeV, δp/p ~ % some regions 0 s of khz/mm, (Extremely high rate) Pion rejection with Cerenkov + segmented calorimeter (Need PID) GEM Sashlyk gas Cerenkov collimator Use of baffles to block neutrals and low or high energy charged particles. Several large solenoids would work (Zeus, Babar): present design focuses on CLEO Spin 0, Dubna

22 SOLID allows a Diverse Program Transverse Spin Structure: semi-inclusive DIS from polarized proton and polarized 3 He to access neutron J/Ψ Production PV-DIS on proton d/u Spin 0, Dubna

23 Running of weak mixing angle This is complicated scheme dependent many orders in loops of all particles Parity violating moller scattering neutrino deepinelastic scattering cross-sections 6S 7S 33 Cs atomic transition electroweak fit with uncertainty Major improvements planned for the near future Spin 0, Dubna 3

24 MOLLER An ultra-precise measurement of the weak mixing angle using Møller scattering δ(qew) = ±. % (stat.) ±.0 % (syst.) Detector Array Q = (GeV/c) Ebeam = GeV 0.9 o < θlab < 0.97 o 8 m Hybrid Toroid Upstream Toroid Liquid Hydrogen Target ~75 μa,.5 m LH target APV 35.6 ± 0.73 ppb Electron Beam Spin 0, Dubna 4

25 Physics Reach L e e = i,j=l,r g ij ē i µe i ē j µ e j = 7.5 TeV grr g LL 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 Complementary to direct heavy photon searches: BaBar Test the consistency of the SM prediction, between directly measured mh, mw, mt, sin θw (Courtesy: J. Erler) allowed ε E774 a e E4 a Μ KLOE a Μ explained APV Moller MESAAPEX Test Combined MAMI sin θ eff (e) World average central value A FB (b) E MOLLER 0.3 A LR (had) For MeV m Zd APV (Cs) Ruled out M H [GeV] Ruled out Spin 0, Dubna 5

26 MOLLER Technical Order of magnitude more precise than current state of the art. Polarized Beam unprecedented polarized luminosity unprecedented beam stability helicity flip at khz Liquid Hydrogen Target 5 kw dissipated power ( X QWeak) computational fluid dynamics Toroidal Spectrometer Novel 7 hybrid coil design warm magnets, aggressive cooling Integrating Detectors build on QWeak and PREX intricate support & shielding radiation hardness and low noise Qweak target designed with CFD. Spin 0, Dubna 6

27 Lab Angle (mrad) Backward Forward Spectrometer Concept Full azimuthal coverage! Plenty of space for coils Lab Energy (GeV) ep elastic separation Strong focus reduces background Blocked line of sight Spin 0, Dubna 7

28 Conclusions Parity Violating Electron Scatter has the potential to contribute unique and timely information to a variety of fields. Hall A at Jefferson Lab has a successful major PV program underway. New apparatus and techniques will greatly the extend range and improve uncertainties. Spin 0, Dubna 8