Acknowledgements: D. Armstrong, M. Dalton, K. Paschke, J. Mammei, M. Pitt, B. Waidyawansa and all my theory colleagues A n Experiments Krishna Kumar Stony Brook University The Electroweak Box Workshop at ACFI, UMass, Amherst, September 28, 2017
Outline • Brief motivation for A n measurements • Strange quark form factor experiments • A n in elastic electron-nuclear scattering • A n from electron-electron scattering • Concluding remarks 2 Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017
Parity Violating Electron Scattering (g Ae g VT + β g Ve g AT ) Weak Charge Q W g V is a function of sin 2 θ W 3 Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017
Parity Violating Electron Scattering (g Ae g VT + β g Ve g AT ) Weak Charge Q W g V is a function of sin 2 θ W 100% Pioneering 10% Nuclear Studies (1998-future) Variety of Physics Topics: -4 S.M. Study (2003-2012) 10 S.M. Design/Planning S.M. Future E122 continuous interplay between 1% -5 PVDIS-6 10 hadron physics and electroweak physics G0 Mainz-Be 0.1% H-I SAMPLE SOLID -6 10 A4 G0 ) Steady improvements in PV MIT-12C A4 H-III (A A4 accelerator and detector H-He -7 δ 10 H-II technology CREX PREX-I E158 PREX-II -8 10 Qweak ILC-Moller State of the Art MESA-12C -9 10 • sub-part per billion statistical MOLLER MESA-P2 reach and systematic control -10 10 • sub-1% normalization control -8 -6 -5 -3 -7 -4 10 10 10 10 10 10 A PV 3 Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017
Experimental Technique 4 Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017
Experimental Technique Symmetry of the apparatus helps systematic control: A corr = A det - A Q + α Δ E + Σβ i Δ x i Symmetric azimuthal coverage: Up cancels down, right cancels left… 4 Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017
Assumption on previous page: perfect longitudinal polarization The A n Systematic 5 Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017
6 Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017
PV Experiments 7 Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017
SAMPLE at MIT-Bates open geometry, integrating Proton Target 200 MeV G Ms , (G A ) at Q 2 = 0.1 GeV 2 Archival Plots Pasquini & Vdh (2004) Diaconescu & Ramsey-Musolf (2004) p N (inelastic) tot (N + p N) N (elastic) SAMPLE data Wells et al., PRC (2001) SAMPLE data S. Wells et al. (2001) 8 Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017
G0 at JLab CED + Cerenkov FPD e - beam target Proton Target Forward angle: recoiling proton detected Backward angle: Electrons and Pions detected 9 Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017
J. Mammei G0 Neutron (from 2 H) 10 Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017
PVA4 at Mainz Recent publication Precise backward angle measurements G Es + 0.23 G Ms at Q 2 = 0.23 GeV 2 G Es + 0.10 G Ms at Q 2 = 0.1 GeV 2 Both 1 H and 2 H G Ms , G Ae at Q 2 = 0.1, 0.23, 0.5 GeV 2 11 Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017
G0 Inelastic Scattering Backward angle 1 H measurements have the ability to tag electrons and pions, and there are bins dominated by inelastic electrons C. Capuano 2 H Ph.D. Thesis, William and Mary B n less than few x 10 -5 12 Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017
J. Mammei G0 Pion Production 13 Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017
Very Forward Angle Measurements: HAPPEX/PREX (Hall A) and Qweak (Hall C) Relationship between photo production cross-section and forward scattering amplitude works well when q/E → 0 Septum Magnet Elastic Inelastic detector hardware resolution: ∆ p/p ~ 10 -3 ~10 cm Quad target pure, thin 208 Pb Dipole target 14 Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017
HAPPEX/PREX Data Prediction fails dramatically for 208 Pb Any relevance for precision calculations of gamma-Z boxes for e-N scattering predictions? theory prediction works remarkably well for light nuclei work by A. Afanasev, M. Gorchstein and collaborators 15 Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017
Talks by W. Deconinck and J. Dowd B. Waidyawansa QWeak right column obsolete 16 Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017
Measuring A n from 12 C at Mainz-A1 Michaela Thiel, Anselm Esser, A1 collaboration K. Paschke elastic peak is well-separated raw data is uncorrelated between in precision spectrometers left/right spectrometers: very quiet beam! s r o t c e t e d 0 M . G o r c h t e i n e t a l . (570 MeV) (Forward Direction) - 5 ] Preliminary X (E Beam = 1 - 3 GeV) P R E m p p [ - 1 0 y A. Esser, ECT* r t e m m Trento, August’16. - 1 5 y s Very A m a e - 2 0 B e Preliminary s r e v - 2 5 s n a r spectrometer B T Future: could use other targets ( 28 Si, 40 Ca, 208 Pb) - 3 0 spectrometer A 210-570 MeV beam energies, 15 o -25 o scattering angles - 3 5 0 0 . 0 1 0 . 0 2 0 . 0 3 0 . 0 4 0 . 0 5 0 . 0 6 2 [ 2 2 Q G e V / c ] 17 Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017
E158: Electron-Electron (Møller) Scattering ~ 11 ppb raw statistical error at highest E beam, ~ 0.4% error on weak mixing angle Hydrogen Target Apart from longitudinal running, transversely polarized electron beam data was collected 18 Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017
A n must vanish at 90 degrees in the COM for Møller scattering E158 Transverse Data Dixon and Schreiber (2004) B n (max) ~ 7 ppm E158 acceptance: dotted lines Result: -7.03 ± 0.25 ± 0.36 ppm Theory: -6.91 ppm 6 Fig 2: Run2 46GeV Asymmetries vs Channel 19 Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017
E158 unpublished data might be interesting for phenomenology • The e-p vector analyzing power is found to be consistent with a dispersive approach prediction assuming that the asymmetry of the 30% inelastic background is zero • A PV for e-p scattering is found to be consistent with what is expected from the dominant inelastic scattering amplitude (similar to the inelastic scattering measurements done by G0, PVDIS and Qweak at JLab) 20 Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017
MOLLER proposed to do factor of 5 better than E158 “Odd” MOLLER Acceptance 21 Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017
Why Interesting Here? 22 Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017
Precision Test Planned for MOLLER • set up for physics running • convert to vertical polarization at polarized source • run a few hours • back to longitudinal polarization • back off beam energy by 50 MeV: horizontal polarization on target • extract vector analyzing power to precision and accuracy of demonstrate complete understanding of around or better than 0.5% apparatus: simultaneous test of beam Is theory good to 0.1% with polarization, radiative corrections, detector acceptance, backgrounds Dixon/Schreiber work? 23 Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017
Concluding Remarks • There is a wealth of A n measurements from the parity violation experiments on forward and backward angle elastic electron-proton scattering • Some additional A n measurements of electron-proton inelastic scattering might be of interest; new data forthcoming from Qweak • A n measurements on heavier nuclei provides an interesting theoretical challenge: any new insights relevant to electroweak boxes on light nuclei/proton? New data will soon become available both at 1 GeV (Qweak) and lower energies (Mainz A1) • There are already some interesting constraints on the neutral current amplitude in inelastic electron proton scattering: have all the available data been used to reduce gamma-Z box uncertainties? • The future holds many possibilities for providing precision measurements of A PV in inelastic electron proton scattering at a variety of kinematic points: MOLLER, SOLID and P2. How useful will they be? These experiments are all capable of making new A n measurements: what’s interesting? Continued dialog is necessary to make best use of existing results and optimizing the future program of auxiliary measurements 24 Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017
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