Electric Dipole Moment Experiments Birmingham Particle Physics - PowerPoint PPT Presentation

Electric Dipole Moment Experiments Birmingham Particle Physics Seminar, Feb.13, 2019 W. Clark Griffith University of Sussex

2 W. Clark Griffith, PP seminar, EDMs Outline • what’s an EDM and how to measure it • different types of searches • mercury EDM – nuclear CP violation • polar molecules – electron EDM • neutron EDM • PSI nEDM/n2EDM • cryogenic nEDM

3 W. Clark Griffith, PP seminar, EDMs Electric Dipole Moments • permanent EDM of a particle/atom/molecule violates T and P • with CPT theorem → implies CP violation • Standard Model EDM predictions are vanishingly small • any nonzero measurement is a background free signal of CP violating new physics! • SM CP violation is too small to account for baryogenesis T • BSM extensions preferably allow for new sources of of CP violation = measurable EDMs • EDM experiments have an excellent potential for BSM discovery

4 W. Clark Griffith, PP seminar, EDMs Measuring an EDM via spin precession B E d μ ω L larger E-fields give better sensitivity, need to control magnetic fields very well, guard against any B-fields correlated with E

5 W. Clark Griffith, PP seminar, EDMs EDM searches: neutron nEDM measurements utilise UltraCold Neutrons (UCN) v = 0-6 m/s, can be stored in material bottles 26 e |d n | < | < 3 3 × 10 10 -26 e cm cm 2006 result – Sussex/RAL/ILL reanalysed in 2015 accounting for gravitational depolarisation systematic Sussex led experiment has had world lead since 1999 2 æ ö 300 GeV ç ÷ - » j ´ 24 d sin 10 e.cm ç ÷ n CP L è ø SUSY

6 W. Clark Griffith, PP seminar, EDMs – electron EDM is enhanced by relativistic EDM searches: electron effects in heavy paramagnetic atoms/molecules – best atomic limit is from Berkeley Thallium beam experiment: d Tl = –585 d e | d e | < 1.6 × 10 − 27 e cm (2002) atoms B.C. Regan, E.D. Commins, C.J. Schmidt, and D. DeMille, PRL 88 , 071805 (2002). molecules – polar molecules now give best limits YbF at Imperial College: d YbF ~ 10 6 d e YbF ! | d e | < 1.05 × 10 − 27 e cm (2011) ThO ! J.J. Hudson, D.M. Kara, I.J. Smallman, B.E. Sauer, M.R. Tarbutt, and E. A. Hinds, Nature 473 , 493 (2011). ThO at Harvard/Yale: 2010 ! 2015 ! 2020 | d e | < 1.1 × 10 − 29 e cm (2018) -ACME Collab. Nature 562 , 355 (2018)

7 W. Clark Griffith, PP seminar, EDMs EDM searches: diamagnetic atoms – Diamagnetic atoms ( 1 S 0 ground state) with 1.00E-25 finite nuclear spin ( I ) are sensitive to the EDM of the nucleus / CP-violating nuclear 1.00E-26 forces 95% CL limit (e cm) UV lamps 1.00E-27 Expected signal is larger for heavier atoms: 2-cell UV laser 1.00E-28 4-cell ≈ 10 -3 1.00E-29 " #$$ Hg < 7.4×10 ./0 1cm 199 Hg is the heaviest, stable I=1/2 nucleus 1.00E-30 1985 1990 1995 2000 2005 2010 2015 2020 other diamagnetic experiments: Xe (Princeton, Tokyo, TUM, Mich.) trapped Ra (Argonne,KVI) S.K. Lamoreaux, J.P. Jacobs, B.R. Heckel, F.J. Raab, and E.N. Fortson, PRL 59 , 2275 (1987). J.P. Jacobs, W.M. Klipstein, S.K. Lamoreaux, B.R. Heckel, and E.N. Fortson, PRA 52 , 3521 (1995). Rn (Mich./TRIUMF) M.V. Romalis, W.C. Griffith, J.P. Jacobs, and E.N. Fortson, PRL 86 , 2505 (2001). W.C. Griffith, M.D. Swallows, T.L. Loftus, M.V. Romalis, B.R. Heckel, and E.N. Fortson, PRL 102 , 101601 (2009). B. Graner, Y. Chen, E.G. Lindahl, and B.R. Heckel, PRL 116 , 161601 (2016).

8 W. Clark Griffith, PP seminar, EDMs EDM searches Energy SUSY? fundamental TeV CP-violating phases • EDM limits from the neutron, θ QCD , d q , ! d e , d µ d q QCD paramagnetic, and diamagnetic atoms can set C qe , C qq orthogonal bounds on CP- violation in SUSY and other g π NN nuclear C S , P , T d n , d p standard model extensions • It is important to improve EDM EDMs of sensitivity in all 3 sectors nuclei atomic EDMs of paramagnetic atoms EDMs of and molecules diamagnetic atoms: Tl, Cs, YbF, ThO… Hg, Xe, Ra, Rn…

9 W. Clark Griffith, PP seminar, EDMs Mercury EDM experiment Univ. of Washington, Seattle, USA a gas of Hg atoms is contained in a quartz vapor cell… a stack of 4 cells is placed in a magnetic and ± 10 kV electric field spin precession of the Hg atoms is interrogated by a UV laser ± 10 kV cosine wound coil for vertical B

10 W. Clark Griffith, PP seminar, EDMs Hg spin precession measurement Transverse Optical Pumping B 254 nm σ + Optical Rotation Angle Absorption Probe Probe Pump

11 W. Clark Griffith, PP seminar, EDMs Hg spin precession measurement Measure ω L via Optical Rotation B ω L 254 nm Linear Detector Linear Polarizer Absorption Pump

12 W. Clark Griffith, PP seminar, EDMs 4 cell, 199 Hg magnetometer EDM sensitive frequency combination = µ ¶ 3 8 B 4 dE w - D + 3 ( z ) w OT c ¶ 3 ! 3 z ! Cancels up to 2 nd order gradient noise w MT E 1 B w = D w - D w c m o 3 w MB E w OB EDM insensitive channels: ω OT - ω OB and (ω OT + ω OB ) – (ω MT + ω MB ) monitor for E field correlations odd and even in z, respectively.

13 W. Clark Griffith, PP seminar, EDMs The EDM of mercury atoms… 30 e |d Hg Hg | < | < 7 7.4 .4 × 10 10 –30 e cm cm • ... is still consistent with zero, smallest EDM upper bound achieved in any measurement! • ...is associated with the mercury nuclear spin ! " < 1.6×10 )*+ ,cm • might arise from the neutron EDM ! / < 2×10 )*1 ,cm • or the proton EDM ! : < 10 )*; cm 9 2 345 < 1.5×10 )78 • T-violating nuclear forces Caveats: assumes single source for ! <= very large uncertainties in nuclear calculations

14 W. Clark Griffith, PP seminar, EDMs Electron EDM • EDM measurements in atoms with unpaired electron spins tend to be sensitive to the electron EDM • how spherical is the electron? • In heavy atoms, the atomic EDM is enhanced relative to the electron EDM best limit is from Thallium: d Tl = –585 d e | d e | < 1.6 × 10 − 27 e cm (2002) U. California, Berkeley B.C. Regan, E.D. Commins, C.J. Schmidt, and D. DeMille, PRL 88 , 071805 (2002).

15 W. Clark Griffith, PP seminar, EDMs Electron EDM – molecular enhancement • With a relatively modest laboratory electric field, the unpaired electron in paramagnetic systems experiences a much larger internal electric field • Gives a large enhancement of ! " relative to the atomic or molecular EDM • x10 3 in heavy atoms (Tl,Fr) • x10 6 in molecules O + e- e- + Measure Th this http://laserstorm.harvard.edu/edm/

16 W. Clark Griffith, PP seminar, EDMs Electron EDM – current status 10 -22 Predicted value of the electric dipole moment (e.cm) All current competitive experiments are done using Extensions to Standard Model polar molecules 10 -24 10 -26 YbF beam (Imperial, 2011) Trapped HfF + (JILA, 2017) 10 -28 ThO beam (ACME-I, 2014) n -loop CP-violating ThO beam (ACME-II, 2018) diagram phases 10 -30 YbF projected sensitivity 10 -32 Energy scale for MSSM, f ~ 1 new particles MSSM, f ~ a / p 10 -34 Left-right Multi-Higgs When + = 1 and sin(0 12 ) ~1 : 10 -36 ! " = 10 &'( e.cm corresponds to Λ ≈ 100 TeV Standard Model

17 W. Clark Griffith, PP seminar, EDMs Current eEDM experiment at Imperial B RF spin analyzer Spin precession region RF spin polarizer Supersonic YbF beam Temperature: 4 K To increase precision: Speed: 590 m/s (1) Increase number of detected molecules (2) Reduce magnetic noise (3) Increase spin-precession time

18 W. Clark Griffith, PP seminar, EDMs More molecules and reduced magnetic noise New plates reduce Johnson noise 20x improved detection New magnetic Prepares 6x shields New more molecules magnetometer array Ø x20 improved eEDM sensitivity relative to 2011 result Ø 2019: aim for new measurement with uncertainty of 5 x 10 –29 e.cm Ø 2020: improve limit to 2 x 10 –29 e.cm Ø This is limit of current method - to go further, must increase spin precession time

19 W. Clark Griffith, PP seminar, EDMs New YbF experiment Ø Spin precession time limited by thermal expansion of beam – need ultracold molecules Ø Have recently demonstrated laser cooling of YbF molecules to 100 µK > 300x improvement Ø 2019-2022: build this apparatus and demonstrate eEDM sensitivity at 10 –30 e.cm level Ø Longer term: use the apparatus to measure eEDM with uncertainty below 10 -31 e.cm

20 W. Clark Griffith, PP seminar, EDMs YbF next-next-generation • full 3D laser cooling/trapping of YbF • launched 10 cm up into E and B field region, fall back down for detection • will have many less molecules than in a beam, but much longer coherence time • beam: ~ 0.001 sec • fountain: ~ 1 sec Design for a fountain of YbF molecules to measure the electron's electric dipole moment M R Tarbutt, B E Sauer, J J Hudson and E A Hinds New J. Phys. 15 (2013) 053034

21 W. Clark Griffith, PP seminar, EDMs ACME electron EDM experiment • A dvanced C old M olecule E lectron edm • Collaboration between Harvard (John Doyle, Gerald Gabrielse) and Yale (David Demille) • uses ThO molecules • with ~100 V/cm laboratory electric field, electron sees internal field ~ 85 GV/cm • Ω -doublet molecular state structure allows spectroscopic reversal of EDM signal H state diagram • a powerful tool for ruling out systematic effects • small magnetic g-factor: " ∆ $ ⟹ &~10 *+ ThO level diagram

22 W. Clark Griffith, PP seminar, EDMs ACME apparatus http://laserstorm.harvard.edu/edm/gallery.html