High Precision Not High Energy Using Atomic Physics

High Precision, Not High Energy Using Atomic Physics to Look Beyond the Standard Model Part 2: Never Measure Anything But Frequency

Beyond the Standard Model Ways to look for new physics: 1) Direct creation 2) Passive detection 3) Precision measurement Look for exotic physics in relatively mundane systems using precision spectroscopy to measure extremely tiny effects Image: Mike Tarbutt/ Physics World

New Physics from Forbidden Events Parity-Violating Transitions Observed, levels consistent with Standard Model Photon Statistics, other departures from normal No sign, consistent with Standard Model Lorentz/ CPT symmetry violation No sign, consistent with Standard Model holding strong… … but more stringent tests possible frequency shift measurements

Frequency “Never measure anything but frequency!” -- Arthur Schawlow (1981 Nobel in Physics) Extremely well-developed techniques for frequency measurements Atomic clocks Same techniques enable ultra-precise measurements of all sorts of frequencies Art Schawlow, ca. 1960 http: //www. aip. org/history/exhibits/ laser/sections/whoinvented. html

Clocks Newgrange passage tomb Built ~3000 BCE Timekeeping: counting “ticks” Harrison’s marine chronometer Image: Royal Museums Greenwich Clock: Model compared to standard

Comparing Clocks Step 1: Synchronize unknown clock with standard http: //time. gov/

Comparing Clocks Step 1: Synchronize unknown clock with standard Step 2: Wait a while

Comparing Clocks Step 1: Synchronize unknown clock with standard Step 2: Wait a while Step 3: Check standard again Adjust as needed…

Atomic Clocks Atoms are ideal time standards: Frequency of light fixed by Quantum Mechanics No moving parts (not accessible by users…) All atoms of given isotope are identical SI Unit of Time (definition 1967): The second is the duration of 9, 192, 631, 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom.

Ramsey Interferometry Atomic clock: Microwave source compared to atomic transition Complicated by motion of atoms Doppler shifts Inhomogeneities Limited interaction time Norman Ramsey ca. 1952 Image: AIP, Emilio Segre archive Best frequency measurements use Ramsey Interferometry (1989 Nobel Prize in Physics)

Ramsey Interferometry Step 1: Prepare superposition state Light from lab oscillator used to make “p/2 -pulse” p/2 “Bloch Sphere” picture

Ramsey Interferometry Step 1: Prepare superposition state Step 2: Free evolution for time T Upper and lower states evolve at different rates “phase” (wave frequency depends on energy of state) “Bloch Sphere” picture

Ramsey Interferometry Step 1: Prepare superposition state Step 2: Free evolution for time T Step 3: Second p/2 -pulse, interference Final population determined by phase between states p/2 “Bloch Sphere” picture

Ramsey Interferometry Step 1: Prepare superposition state Step 2: Free evolution for time T Step 3: Second p/2 -pulse, interference Final population determined by phase between states p/2 “Bloch Sphere” picture

Ramsey Interferometry Clock signal: interference fringes Maximum probability exactly on resonance frequency Uncertainty in frequency depends on 1/T For best performance, need to maximize free evolution time T Cold atoms, fountain clocks Image: NIST

Fountain Clock T~1 s Dawn Meekhof and Steve Jefferts with NIST-F 1 (Images: NIST) Part in 1016 accuracy 1. 00000000 ± 0. 000000001 s

Clocks for New Physics Clock technology enables 15 -digit precision Experimental clocks at 17 -18 digits Sensitive to tiny shifts Lorentz violation General Relativity Changing “constants” Forbidden moments Change in clock frequency due to 33 -cm change in elevation (Data from Chou et al. , Science 329, 1630 -1633 (2010))

Fine Structure Constant Determines strength of EM force Energies of atomic states (not this much change…) “Fine structure”: DEfs ~ Z 2 a 2 Exotic physics changes a Enrico Fermi Image: Chicago/AIP

Electron g-Factor Best measurement of a uses single trapped electron Rotation: Spin flip: Dirac Equation predicts g=2 Difference tests QED (from Hanneke et al. , PRA 83 052122 (2011)) g = 2. 00231930436146 ± 0. 00000056

Fine Structure Constant g = 2. 00231930436146 ± 0. 00000056 Extract value of a from QED Value from atom interferometry 8 th-order Feynman diagram Comparison tests high-order QED, including muons and hadrons Extend to positrons, protons, antiprotons…

Changing Constants (Right now…) Limits on past change: Oklo “natural reactor” Fission products from 1. 7 billion years ago Constrains possible change in a over time Image: R. Loss/Curtin Univ. of Tech.

Astronomical Constraints Look at absorption/emission lines from distant galaxies Wavelength depends on value of a in the past Compare many transitions, sort out redshift vs. Da Image: NASA

“Australian Dipole” From King et al. , ar. Xiv: 1202. 4758 [astro-ph. CO]

Modern AMO Physics Limits on change in a around Average rate of change: One year of atomic clock operation Spatial variation should lead to Image: NASA (Sun orbiting Milky Way moves through dipole)

Clock Comparisons 6 years 14 years ~1 year

Clocks for New Physics Clock technology enables 15 -digit precision Experimental clocks at 17 -18 digits Sensitive to tiny shifts Lorentz violation Changing “constants” Forbidden moments Change in clock frequency due to 33 -cm change in elevation (Data from Chou et al. , Science 329, 1630 -1633 (2010))

Electric Dipole Moment Fundamental particles have “spin” Magnetic dipole moment, energy shift in magnetic field Electric dipole moment would violate T symmetry Only tiny EDM (~10 -40 e-cm) allowed in Standard Model Larger in all Standard Model extensions

Electron EDM Great Big Gap Source: B. Spaun thesis, Harvard 2014

Measuring EDM Basic procedure: Apply large electric field, look for change in energy Problem 1: Electrons are charged, move in response to field Solution 1: Look at electrons bound to atoms or molecules Problem 2: Electrons redistribute to cancel internal field Solution 2: Relativity limits cancelation, look at heavy atoms Problem 3: Extremely large fields are difficult to produce in lab Solution 3: Polar molecules provide extremely large (GV/cm) internal fields for small applied lab fields Look for EDM in polar molecules involving heavy atoms

EDM Measurement State Preparation State Detection Electric field Atomic Beam Source Magnetic field

Ramsey Interference B E

EDM Limits Yb. F molecule (Imperial College) Th. O molecule (Harvard/Yale) Thallium atom (Berkeley) de < 8. 7 × 10 -29 e-cm (90% c. l. ) Source: B. Spaun thesis, Harvard 2014

Other Opportunities 1) Systematic improvement Steady improvement of uncertainties in clocks, etc. Longer run times ACME projects another factor of 10 in EDM limit

Other Opportunities 1) Systematic improvement 2) Similar processes, new systems New molecules, ions for EDM searches “Nuclear clock” in thorium Dysprosium spectroscopy Lorentz symmetry tests, coupling to dark matter

Other Opportunities 1) Systematic improvement 2) Similar processes, new systems 3) Exotic systems Measure g-factor for positron, proton, antiproton Test CPT symmetry Exotic “atoms” positronium, muonic hydrogen “Proton charge radius problem”

Other Opportunities 1) Systematic improvement 2) Similar processes, new systems 3) Exotic systems 4) ? ? Never underestimate the ingenuity of physicists… No new physics yet, but it has to be out there… Just a matter of looking carefully in the right places

Names to Conjure With Experiment Theory Gerald Gabrielse Toichiro Kinoshita Cornell University http: //gabrielse. physics. harvard. edu/ Dave De. Mille http: //www. yale. edu/demillegroup/ ACME Collaboration http: //laserstorm. harvard. edu/edm/ Ed Hinds http: //www 3. imperial. ac. uk/ccm/ NIST Time and Frequency http: //www. nist. gov/pml/div 688/ LNE-SYRTE http: //syrte. obspm. fr/tfc/frequences_optiques/accueil_en. php

Clock Comparisons Single clock can’t detect change in a, but comparison of two atoms can 1) Cs-Rb ground-state hyperfine, monitored over 14 years 2) Sr optical lattice clocks, over 6 years (compare to Cs standard) 3) Al+ and Hg+ trapped ions, over 1 year

Frequency Comb Ultra-fast pulsed laser: lots of little lasers with different frequencies Spaced by repetition rate determined by size of cavity Intensity Allows comparison of laser frequencies over huge range Frequency nn=n nrep+fcav n 2 n=2 n nrep+fcav × 2 nbeat = fcav