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Status of the nEDM measurement

Status of the nEDM measurement. Progress 2011 PSI Proposal R–05–03.1. Philipp Schmidt -Wellenburg on behalf of the nEDM collaboration. CP violation and EDM. CP so far only in weak decay Excellent probe for physics beyond the Standard Model Might explain BAU matter/anti-matter problem.

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Status of the nEDM measurement

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  1. Status of the nEDM measurement Progress 2011PSI Proposal R–05–03.1 Philipp Schmidt-Wellenburgon behalf of the nEDM collaboration

  2. CP violation and EDM • CP so far only in weak decay • Excellent probe for physics beyond the Standard Model • Might explain BAU matter/anti-matter problem A nonzero particle EDM violates P, T and, assuming CPT conservation, also CP. T

  3. The measurement technique Measure the difference of precession frequencies in parallel/anti-parallel fields: RAL-Sussex-ILL:dn< 2.9 x 10–26e cmC.A.Baker et al., PRL 97 (2006) 131801 for dn<10-26 ω< 60 nHz

  4. Ramsey resonance curve Sensitivity: • Visibility of resonanceE Electric field strengthT Time of free precessionN Number of neutrons The Ramsey technique “Spin up” neutron... B0↑ Apply /2 spin flip pulse... B0↑ + Brf Free precessionat ωL B0↑ Second /2 spin flip pulse. B0↑ + Brf

  5. Reminder • Phase I: • Operate and improve OILL@ILL (all cycles 2008) • Moved OILL March 2009 • Design of n2EDM, related R&D • Phase II: • Operate OILL@PSI (2009-2013) • Sensitivity goal: 5x10-27ecm • Design of n2EDM, construction and setup • R&D • Phase III: • Operate n2EDM (2014-2017) • Sensitivity goal: 5x10-28ecm   

  6. Magnetic fields Magnetic field control: • Four layer mu-metal shield • 33 trim coils (inside shield) • Six compensation coils(around apparatus) • Mercury comagnetometer • Cesium magnetometer array

  7. Mercury co-magnetometer • Average magnetic field (volume and cycle) • σ(B)~ 20 – 50 fT • Center of massdifferent than UCN • Important Systematic effectsdue to magnetic field gradients PM τ = 140s polarization cell B0 ≈ 1μT ¼ wave platelinear polarizer Hg lamps HgO source

  8. Mercuy comagnetometer

  9. Hg contaminated Sudden collapse 1st change of electrodes Geometric phase 2nd change of electrodes Hg under pressure 3rd change of electrodes

  10. Cesium magnetometers • Two cesium magnetometer arrays • Stabilized laser • PID phase locked DAQ Monitoring of vertical magnetic gradients ±140kV 1 2 3 4 5 … 11 12

  11. Most important source of systematic effects → Field mapping → Online Cs-OPM measurement → Combination of online information and field maps Magnetic field gradients

  12. Geometric phase • Gradient applied with trim coils: 0 – 4nT/cm • E-field: ±100 kV/12cm • For each setting:B0 up and B0 down • ~30 polarity changes • Gradient:Cs-OPM measurement • ~20h per point

  13. Results geometric phase • For B0 up: (-9.69 ± 0.33) * 10-27 e cm @ 10 pT/cm • For B0 down: (9.94 ± 0.25) * 10-27 e cm @ 10 pT/cm • Data are in agreement within 15 % to the calculations of Pendlebury 1.15 * 10-26 e cm @ 10 pT/cm • Discrepancy is still investigated, gradients from fluxgate maps seem to agree better…

  14. Cs-OPM response method • Measure the response of each Cs-OPMfor current changes for all trim coils → Response Matrix Amn → Invert Matrix → Calculate currents for each coil to get desired field value

  15. Cs-OPM response method

  16. Ultra cold neutrons • Regular pulses (every 480s for 4s) • 900 000 UCN in direct measurements • 16 000 UCN counted after 4s storagein precession chamber

  17. UCN Detector • Counts neutrons • Can distinguish gammas • Sends UCN countsto main DAQ

  18. Discrepancy for α0can be explained with UCN counting method Manual adjusted emptying sequence No manual tuning of trim coils (only Cs response) UCN Spin performance

  19. UCN emptying curve • Low α0 for T1 and T2 indication for strong depolarization (SC magnet → ~100%) τflip = 236 sτloss =16.5 sτ↓ = 163 s τ↑ = 16.9 sN = 29185α0 = 0.999 Best fit to data

  20. UCN Ramsey cycles Ramsey curve taken with 250 s precession time N0= 1205α0 = -0.46

  21. UCN nEDM run

  22. Outlook • Characterize UCN switch properties(April: storage and transmission measurements at ILL) • Recover excellent Hg performance(bake out electrodes, insulator ring) • Upgrade Cs-Array to 8 HV, 10 ground sensors • Characterize important UCN parameters with high UCN density (α , τ,Δh,T1, T2) • 150 nights nEDM-Data (July-December, 2012)

  23. Phase III - movable 5 layer cubic shielding (design discussion with companies ongoing) - active vibration compensation

  24. Physikalisch Technische Bundesanstalt, Berlin Laboratoire de Physique Corpusculaire, Caen Institute of Physics, Jagiellonian University, Cracow Henryk Niedwodniczanski Inst. Of Nucl. Physics, Cracow Joint Institute of Nuclear Reasearch, Dubna Département de physique, Université de Fribourg, Fribourg Laboratoire de Physique Subatomique et de Cosmologie, Grenoble Biomagnetisches Zentrum, Jena Katholieke Universiteit, Leuven Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse, Orsay Inst. für Kernchemie, Johannes-Gutenberg-Universität, Mainz Inst. für Physik, Johannes-Gutenberg-Universität, Mainz Paul Scherrer Institut, Villigen Eidgenössische Technische Hochschule, Zürich The Neutron EDM Collaboration M. Burghoff, A. Schnabel, J. Vogt G. Ban, V. Helaine1, Th. Lefort, Y. Lemiere, O. Naviliat-Cuncic, E. Pierre1, G. Quéméner K. Bodek, St. Kistryn, G. Wyszynski3, J. Zejma A. Kozela N. Khomutov Z. Grujic, M. Kasprzak, P. Knowles, H.C. Koch, A. Weis G. Pignol, D. Rebreyend S. Afach, G. Bison J. Becker, N. Severijns, R. Chankova S. Roccia C. Plonka-Spehr, J. Zenner1 W. Heil, A. Kraft, T. Lauer , D. Neumann, Yu. Sobolev2 Z. Chowdhuri, M. Daum, M. Fertl3 , B. Franke3, M. Horras3, B. Lauss, J. Krempel , K. Mishima4, A. Mtchedlishvili, P. Schmidt-Wellenburg, G. Zsigmond K. Kirch1, F. Piegsa, D. Ries also at: 1Paul Scherrer Institut, 2PNPI Gatchina, 3Eidgenössische Technische Hochschule, 4KEK

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