Jie Pan University of Manitoba

Transcription

1 Jie Pan University of Manitoba (for the Qweak Collaboration) The JLab Hall-C User Meeting Jan 3, 018 1

2 Overview Qweak determines QpW and sinθw to high precision via measuring parity-violation asymmetry (~300 ppb) in e-p elastic scattering at low Q (0.048 GeV) Deviations from Standard Model predictions would be sensitive to PV semi-leptonic physics beyond the SM Qweak Ran in Hall C with two run periods during Commissioning data (~4% of total dataset) was published in PRL 111, (013) - Data were unblinded last March - Results out of full analysis were released last September This will lead to a publication soon! J.Pan (University of Manitoba): Qweak JLab Hall-C User Meeting 1 /3/ 018

3 Search for Physics beyond the Standard Model The Standard Model (SM) - A successful low energy effective theory of more fundamental physics, yet incomplete Two complimentary approaches in testing SM and searching for new physics - Direct searches for new particles at high energy (e.g. LHC) - Indirect searches to test the SM via precision measurements at low energy (e.g. PVES, including Qweak) The Qweak Experiment - Elastic scattering of electron beam from proton target (e+p e+p) - Measure significantly suppressed SM observable (QW(p)) to high precision - Sensitive search for new physics at TeV mass scale J.Pan (University of Manitoba): Qweak JLab Hall-C User Meeting 1 /3/ 018 3

4 Proton's Weak Charge in the Standard Model Weak charges - neutral current analog to the electric charges - At tree level, QpW = 1-4sinθW ( θw - weak mixing angle); Qweak can lead to a high precision test of sinθw at low energy J.Pan (University of Manitoba): Qweak JLab Hall-C User Meeting 1 /3/ 018 4

5 Parity Violating Electron Scattering - Scatter electrons of opposite helicity from an unpolarized target right-handed e- beam left-handed e- beam - The scattering process: EM + WNC - The interference term gives rise to a parity-violating asymmetry ~ -00 ppb J.Pan (University of Manitoba): Qweak JLab Hall-C User Meeting 1 /3/ 018

6 Extraction of the Proton's Weak Charge The PV asymmetry in e-p elastic scattering: At Qweak kinematics (Q 0 and θ 0): The QpW term dominates the total asymmetry (~/3) G F Q p A PV = [Q W + B ( θ,q ) Q ] 4 π α Proton s weak charge (QpW = 1-4sinθW at tree level) J.Pan (University of Manitoba): Qweak Hadronic structure - contains GγEM & GZEM form factors, well determined by existing higher Q PVES data JLab Hall-C User Meeting 1 /3/ 018 6

7 Qweak Apparatus [T. Allison et al. Nuclear Instruments and Methods in Physics Research A 781 (01) ] J.Pan (University of Manitoba): Qweak JLab Hall-C User Meeting 1 /3/ 018 7

8 Multiple Helicity Reversals Three independent techniques for helicity reversal of e- beam: Rapid pseudo-random reversal (960/sec): Rejects LH target boiling noise. IHWP at ~8 hour intervals: Mechanical action unable to induce electrical or magnetic induced false asymmetries. Wien filter at monthly intervals: Rejection of beam size (or focus) modulation induced false asymmetry and suppression of slow drifts in apparatus linearity. Also as check construct NULL: out-of-phase quantity from the two slow reversal techniques to bound unaccounted for false asymmetries. J.Pan (University of Manitoba): Qweak JLab Hall-C User Meeting 1 /3/ 018 8

9 From Raw Asymmetry to Physics Asymmetry STEP 1: Measure Araw - Integrate detector signal (S) over each helicity state and normalized to beam charge (Q) Y=S/Q - Calculate asymmetries for each quartet pattern STEP :

10 Aluminum Target Window Backgrounds Dilution fraction (fal) IHWP IN or OUT Wien Filter L or R Sign correction for slow reversals and further systematic corrections are needed to extract physics asymmetry for Al - Directly measured with empty target Asymmetry (AAl) - Directly measured from thick Al dummy target (Corrections for effects of H made using simulation and data driven models of elastic and quasi-elastic scattering) Time Period [~8 hour intervals] fal ~.% AAl = 11 ± 77 ppb Resulting in a -38 ppb correction to the hydrogen asymmetry (0%) J.Pan (University of Manitoba): Qweak JLab Hall-C User Meeting 1 /3/

11 Detector Optical Imperfections: Abias Systematic

12 Final Aep & Uncertainty Contributions

13 QpW Determination Method - global fit of PVES data extrapolated to Q = 0 [R.D. Young et al. PRL 99, 1003]

14 Results Determined from Qweak Aep

15 Results Determined from Qweak Aep

16 Results Determined from Qweak Aep

17 Results Determined from Qweak Aep

18 Running of SinθW

19 Sensitivity to New Physics

20 Leptoquarks Impact of QpW on leptoquarks: [Erler, Kurylov, Ramsey-Musolf, Phys. Rev. D 68, (003)] Included HERA, LEP and APV data in analysis [Aaron, et al. Phys. Lett. B 70, (011)] New Qweak data has sensitivity to distinguish among LQ 9% CL New Qweak data rule out leptoquark masses limit ~.3 TeV for g = 4πα (The current LHC limits at ~1 TeV) J.Pan (University of Manitoba): Qweak JLab Hall-C User Meeting 1 /3/ 018 0

21 Implications for Dark Parity Violation Dark Photon - possible portal for new force to communicate with SM? Dark parity violation [Davoudiasl, Lee, Marciano, Phys. Rev. D89, (014)] [Davoudiasl, Lee, Marciano, Phys. Rev. D9, 000 (01)] - New source of low energy PV through mass mixing between Z0 and Zd - Complementary to direct searches for heavy dark photons New Qweak point rules out some of the allowed region

22 Summary Qweak precisely measured QpW, in good agreement with SM Aep = -6. ± 7.3 (stat) ±.8 (syst) ppb QWp (this exp.) = ± [QWp (SM) = ± ] Lead to a very sensitive measurement of sinθw at low Q for BSM test ~ 0.46% in precision Mass reach for new neutral current semi-leptonic PV physics ruled 9% CL: - Ʌ/g < 7.4 TeV (<3. TeV for arbitrary flavor ratios) - Quark flavor dependent mass reach limit Ʌ ~ 6 TeV (assume g = 4π) Will play a role in future analyses of bounds (or discoveries) of a variety of new physics Builds scientific and technical foundation for next generation of measurements J.Pan (University of Manitoba): Qweak JLab Hall-C User Meeting 1 /3/ 018

23 The Qweak Collaboration 101 collaborators 6 grad students 11 post docs 7 institutions Institutions: 1 University of Zagreb College of William and Mary 3 A. I. Alikhanyan National Science Laboratory 4 Massachusetts Institute of Technology Thomas Jefferson National Accelerator Facility 6 Ohio University 7 Christopher Newport University 8 University of Manitoba, 9 University of Virginia 10 TRIUMF 11 Hampton University 1 Mississippi State University 13 Virginia Polytechnic Institute & State Univ 14 Southern University at New Orleans 1 Idaho State University 16 Louisiana Tech University 17 University of Connecticut 18 University of Northern British Columbia 19 University of Winnipeg 0 George Washington University 1 University of New Hampshire Hendrix College, Conway 3 University of Adelaide 4 Syracuse University Duquesne University D. Androic, D.S. Armstrong, A. Asaturyan, T. Averett, J. Balewski, K. Bartlett, J. Beaufait, R.S. Beminiwattha, J. Benesch, F. Benmokhtar, J. Birchall, R.D. Carlini, G.D. Cates, J.C. Cornejo, S. Covrig, M.M. Dalton, C.A. Davis, W. Deconinck, J. Diefenbach, J.F. Dowd, J.A. Dunne, D. Dutta, W.S. Duvall, M. Elaasar, W.R. Falk*, J.M. Finn*, T. Forest,, C. Gal, D. Gaskell, M.T.W. Gericke, J. Grames, V.M. Gray, K. Grimm, F. Guo, J.R. Hoskins, K. Johnston, D. Jones, M. Jones, R. Jones, M. Kargiantoulakis, P.M. King, E. Korkmaz, S. Kowalski, J. Leacock, J. Leckey, A.R. Lee, J.H. Lee, L. Lee, S. MacEwan, D. Mack, J.A. Magee, R. Mahurin, J. Mammei, J.W. Martin, M.J. McHugh, D. Meekins, J. Mei, R. Michaels, A. Micherdzinska, A. Mkrtchyan, H. Mkrtchyan, N. Morgan, K.E. Myers, A. Narayan, L.Z. Ndukum, V. Nelyubin, H. Nuhait, Nuruzzaman, W.T.H van Oers, A.K. Opper, S.A. Page, J. Pan, K.D. Paschke, S.K. Phillips, M.L. Pitt, M. Poelker, J.F. Rajotte, W.D. Ramsay, J. Roche, B. Sawatzky, T. Seva, M.H. Shabestari, R. Silwal, N. Simicevic, G.R. Smith, P. Solvignon*, D.T. Spayde, A. Subedi, R. Subedi, R. Suleiman, V. Tadevosyan, W.A. Tobias, V. Tvaskis, B. Waidyawansa, P. Wang, S.P. Wells, S.A. Wood, S. Yang, R.D. Young, P. Zang, and S. Zhamkochyan 1 3 7, , , 1 10, , Spokespersons Project Manager Grad Students *deceased Hadron - China ,, , 0 0 1, , , , 19, /10/ 016 3

24 Thank you! 4 Hadron - China /10/ 016