CryoEDM A Cryogenic Neutron-EDM Experiment at the ILL
Collaboration: Sussex University, RAL, ILL, Kure University, Oxford University Peter Geltenbort
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 1 Fundamental Inversions
C particle antiparticle (Q →−Q)
P position inverted (r →−r)
T time reversed (t →−t)
P. Geltenbort(courtesy of H. Kraus) Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 2 Symmetries Weak interactions are not P or C symmetric. Normal matter - n, μ, π - readily breaks C / P symmetry.
The combination CP is different: Normal matter respects CP symmetry to a very high degree.
Time reversal is equivalent to CP (with CPT ok): Normal matter respects T symmetry to a very high degree.
P. Geltenbort(courtesy of H. Kraus) Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 3 EDM breaks P and T Symmetry
neutron EDM: = [expressed in e·cm] spin dsnn d €
P odd T odd
P − T + + + − − + −
(P no big deal) (CP big deal) (assuming CPT invariance) P. Geltenbort(courtesy of H. Kraus) Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 4 Theoretical Overview • SM contribution is immeasurably small, but... • most models beyond SM predict values about 106 greater than SM. Very low background! • EDM measurements already constrained SUSY models. • “Strong CP Problem”: Why does QCD not violate CP? Nobody knows. • Finally, there is the question of baryon – anti- baryon asymmetry in the universe.
P. Geltenbort(courtesy of H. Kraus) Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 5 Two Motivations to Measure EDM
EDM violates T symmetry Deeply connected to CP violation and the matter-antimatter asymmetry of the Universe Standard model EDM is effectively zero, but big enough to measure in non-standard models Direct test of physics beyond the standard model P. Geltenbort(courtesy of H. Kraus) Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 6 EDM limits: the first 50 years (e·cm) n 10-20 neutron: 10-20 Electro- electron: magnetic 10-22 10-24
Multi Higgs SUSY φ ∼ 1
Left-Right φ ∼ α/π
-30 -30 Experimental Limit on d Experimental 10 10 1960 1970 1980 1990 2000 10-32 Factor ~10 per 8 years 10-34 Standard Model Cited ~280 times already! 10-36 [d < 6.3x10-26 e·cm (90% CL); PRL 82, 904 (1999)] n 10-38 “It is fair to say that the neutron EDM has ruled out more theories (put forward
to explain K0 decay) than any experiment in the history of physics” R. Golub P. Geltenbort (P. Harris) Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 7 Reality check If neutron were the size of the Earth...
+e Δx ... current EDM limit would -e correspond to charge separation of
P. Geltenbort(P. Harris) Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 8 Δx ≈ 3μ The ILL in Grenoble
P. Geltenbort(courtesy of H. Kraus) Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 9 Compare the precession frequency for parallel fields:
Experiments: Measurement of Larmor precession frequency of polarised neutrons in a magnetic & electric field
ν Δ μ ↑↑ = E↑↑/h = [-2B0 n -2Edn]/h
to the precession frequency for anti-parallel fields
σ (d ) = h n 2αET N α: polarisation product ν Δ μ E: electric field ↑↓ = E↑↓/h = [-2B0 n + 2Edn]/h T: observation time The difference is proportional to d and E: N: number of neutrons n ν ν h( ↑↑ - ↑↓) = 4E dn
P. Geltenbort (M. van der Grinten) Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 10 Measurement principle
Measure Larmor spin precession freq in parallel & antiparallel B and E fields
B E
dn makes precession faster...
μ B
... or slower. So, reverse E relative to B and look for freq shift.
P. Geltenbort(P. Harris) Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 11 1999 end of running α 0.5 0.7 E 4.5 kV/cm 11 kV/cm N 13000 18000 T 130 s 130 s
σ 6×10-25 e·cm × -25 EDM 1.5 10 e·cm
α : Si polariser E : DLC, bottle configuration, discharge cleaning, N : DLC, Si polariser, UCN- guides
P. Geltenbort (M. van der Grinten) Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 12 P. Geltenbort (M. Van der Grinten) Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 13 Ramsey’s Technique
“Spin up” 1. neutron...
Apply π/2 spin 2 s 2. flip pulse...
Free 130 s 3. precession...
Second π/2 spin 2 s 4. flip pulse.
P. Geltenbort(courtesy of H. Kraus) Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 14 Ramsey Resonance Phase gives frequency offset from resonance. 24000
22000
20000
18000 x x 16000 x x 14000
12000
Spin-Up Neutron Counts 10000 Resonant freq. x = working points 29.7 29.8 29.9 30.0 30.1 Applied Frequency (Hz)
P. Geltenbort(courtesy of H. Kraus) Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 15 The Measurement
P. Geltenbort(courtesy of H. Kraus) Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 16 Mercury Magnetometry
Polarized mercury atoms PMT
P. Geltenbort(courtesy of H. Kraus) Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 17 With Magnetometer
P. Geltenbort(courtesy of H. Kraus) Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 18 False EDM Signals
∂×B 1 vE ⇒ Br∝ B′ = ∂zcr γ 2 from divB = 0 from spec. rel.
Different for 199Hg and neutrons see: Phys. Rev. A 70, 032102 (2004) Need for precise magnetometry
P. Geltenbort(courtesy of H. Kraus) Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 19 Error budget (10-27 e·cm)
Effect Shift Uncertainty Statistical 0 15.1 Door cavity dipole -11.0 4.5 Other GP dipole shifts 0 6.0 (E x v)/c2 from translation 0 0.5 (E x v)/c2 from rotation 0 1.0 Light shift: direct & GP 3.5 0.8 B fluctuations 0 2.4 E forces – distortion of bottle 0 0.4 Tangential leakage currents 0 0.1 AC B fields from HV ripple 0 0.01 Hg atom EDM 0 0.5 2nd order E x v 0 0.02 Total –7.5 15.1 stat, 8.0 sys
P. Geltenbort(P. Harris) Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 20 Final Result (Room Temperature experiment)
New upper limit: -26 |dn| < 3.0 x 10 e·cm (90% CL)
Preprint hep-ex/0602020 PRL 97, 131801 (2006)
P. Geltenbort(P. Harris) Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 21 CryoEDM – the new generation
New technology: • More neutrons •Higher E field • Better polarisation • Longer NMR coherence time 100-fold improvement in sensitivity
P. Geltenbort(courtesy of H. Kraus) Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 22 Ultra-cold Neutron Production phonon
cold neutron
ultra-cold neutron
λn = 8.9Å; E = 1.03meV
1.03 meV (11K) neutrons down-scatter by emission of phonons in superfluid helium at 0.5K Up-scattering suppressed: hardly any 11K phonons
P. Geltenbort(courtesy of H. Kraus) Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 23 Ultra-cold Neutron Production
phonon Single-phonon production cold neutron
ultra-cold neutron Multi-phonon production
1.19 ± 0.18 UCN cm−3 s−1 expected 0.91 ± 0.13 UCN cm−3 s−1 observed C A Baker et al., Phys. Lett. A 308 (2002) 67 P. Geltenbort(courtesy of H. Kraus) Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 24 Ultra-cold Neutron Detection • ORTEC ULTRA at 430mK temperature. • Equipped with thin surface layer of 6Li. • Using: n + 6Li →α+ 3H
2.73 MeV Triton peak
Alpha peak
C.A.Baker et al., NIM A487 (2002) 511 P. Geltenbort(courtesy of H. Kraus) Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 25 The Cryogenic Setup Neutron beam input
Cryogenic Ramsey chamber
Transfer section Superconducting shield
P. Geltenbort(courtesy of H. Kraus) Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 26 Superconducting Lead Shield
P. Geltenbort(M. van der Grinten) Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 27 Improvements on Statistics σ = h /2 D αET N Parameter RT Expt Sensitivity • Polarisation+detection α = 0.75 x 1.2 • Electric field: E = 106 V/m x 4 • Precession period: T = 130 s x 2 • Neutrons counted: N = 6 x 106 /day x 4.5 (with new beamline) x 2.6
Total improvement: appr. x 100
P. Geltenbort(courtesy of H. Kraus) Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 28 SQUIDS from CRESST
SQUIDs for Magnetometry
P. Geltenbort(courtesy of H. Kraus) Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 29 Magnetometry Tests 6
5
4 SQUID 4 Pickup Loop
3
Squid OP [V] Squid 2 SQUID 5 1 SQUIDs
0 0481216 4 5 Time [s]
0.02 0.015 SQUID 4 + SQUID 5 0.01 0.005 0 Resolution 0.16 pT -0.005 -0.01 (1.6nG) @ 1Hz Squid 4 + Squid 5 [V] 5 Squid + 4 Squid -0.015 -0.02 0481216 Time [s] P. Geltenbort(courtesy of H. Kraus) Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 30 Ramsey Cell and HV Stack
P. Geltenbort(courtesy of H. Kraus) Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 31 Summary
• After half a century, no sign of an EDM … • SUSY being squeezed. Ever-tighter limits continue to constrain physics beyond SM. • Room-temperature experiment finished. • CryoEDM: under way with aim of ~100 improvement in sensitivity.
P. Geltenbort(courtesy of H. Kraus) Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 32 Neutron EDM measurement apparatus for SNS
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 33 PNPI multi-chamber EDM spectrometer at the UCN facility PF2 of the ILL
see after next talk by A. Serebrov
P. Geltenbort (A. Serebrov) Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 34 H17 for FIGARO and Cryo-EDM; general setup; top view
H171: 15× 80 for H172 80× 80 for Cryo-EDM absorber FIGARO T GRANI H171 15× 80 for FIGARO -EDM Cryo 2 ≈ 100 m Area For completeness: D3 There is also a 18 D9 H H17 crystalnEDM project (PNPI/ILL) for PF1B see next talk by V. Fedorov requirement for He source: λ = 8.93 Å ± 1% Crystal: Intercalated graphite K-IHOPG stage 1 reflected beam crosses above H18 beam stop for CRYO-EDM Axial separation to H16 and H18 ≈ 70 cm
P. Geltenbort(R. Gähler) Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 35 Thanks for your attention!
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 36