PSAS2016, JERUSALEM
23 MAY 2016
Prospects of in-flight hyperfine
spectroscopy of (anti)hydrogen
for tests of CPT symmetryE. WIDMANN
STEFAN MEYER INSTITUTE FOR SUBATOMIC PHYSICS, VIENNA
AUSTRIAN ACADEMY OF SCIENCES
E. Widmann
Antiproton Decelerator @ CERN
All• -in-one machine:
Antiproton capture•
deceleration & cooling•
100 • MeV/c (5.3 MeV)
Pulsed extraction•
• 2-4 x 107 antiprotons per pulse of 100
ns length
1 • pulse / 85−120 seconds
2
Antiproton
production
ASACUSA
E. Widmann
ASACUSA COLLABORATION
3
tomic
pectroscopy
nd
ollisions
sing
low
ntiprotons
A
S
A
C
U
S
A
ASACUSA Scientific project
(1) Spectroscopy of pH̄e
(2) p̄ annihilation cross-section
(3) H̅ production and spectroscopy
The H̅ team
University of Tokyo, Komaba: K. Fujii, N. Kuroda, Y. Matsuda, M. Ohtsuka, S.
Takaki, K. Tanaka, H.A. Torii
RIKEN: Y. Kanai, A. Mohri, D. Murtagh, Y. Nagata, B. Radics, S. Ulmer, S. Van
Gorp, Y. Yamazaki
Tokyo University of Science: K. Michishio, Y. Nagashima
Hiroshima University: H. Higaki, S. Sakurai
Univerita di Brescia: M. Leali, E. Lodi-Rizzini, V. Mascagna, L. Venturelli, N.
Zurlo
Stefan Meyer Institut für Subatomare Physik: P. Caradonna, M. Diermaier, S.
Friedreich, C. Malbrunot, O. Massiczek, C. Sauerzopf, K. Suzuki, E. Widmann,
M. Wolf, J. Zmeskal
Antiproton decelerator CERN-AD
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AD & ELENA area and experiments
4
ELENA
GBAR
ASACUSA
ALPHA
ATRAP
AEgISBASE
ELENA operation from 2017
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Matter-antimatter symmetry
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• Cosmological scale:
• Asymmetry
• CPT
• Microscopic:
symmetry?
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CPT tests - relative & absolute precision
Atomic physics experiments, especially antihydrogen offer the most •
sensitive experimental verifications of CPT
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maser
atomicfountain
atomicbeam
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HFS and Standard Model Extension
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CPT & Lorentz violation
Lorentz violation
D. Colladay and V. A. Kostelecky, PRD 55 (1997)
6760.
no CPT effect on 1S-2S transition
allows to compare different quantities in different sectors
Minimal SME
E. Widmann
Antihydrogen spectroscopy
1s-2s
2 photon
λ=243 nm
Δf/f=10-14
Ground state
hyperfine splitting
f = 1.4 GHz
Δf/f=10-12
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E. Widmann
Ground-State Hyperfine Splitting of H/H–
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spin• -spin interaction
positron - antiproton
Leading: •
Fermi contact term
magnetic moment of • p ̄previously known to • 0.3%, 2012 Gabrielse Penning trap 4.4 ppm PRL 110,130801 (2013)
H: deviation from Fermi contact term: • −32.77±0.01 ppm
finite electric & magnetic radius (Zemach corrections): −41.43±0.44 ppm
polarizability of p/p ̄ (g1,g2, PRA 78, 022517 (2008)): 1.88±0.64 ppm
remaining deviation th-exp: 0.86±0.78 ppm
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HFS measurement in an atomic beam
• atoms evaporate - no trapping needed
• cusp trap provides polarized beam
• spin-flip by microwave
• spin analysis by sextupole magnet
• low-background high-efficiency
detection of antihydrogen
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E.W. et al. ASACUSA proposal addendum
CERN-SPSC 2005-002
achievable resolutionbetter • 10–6 for T ≤ 100 K
> • 100 H ̄/s in 1S state into 4π needed
event rate • 1 / minute: background from cosmics, annihilations uptsreams
σ1π1
const. B
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Experimental setup HFS line
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Hbar production
1st time achieved
in 2010 in
nested Penning trap
B
U
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First observation of „beam“ 2012
• Hbar beam observed with
5σ significance
• n≲43 (field ionization)
• 6 events / 15 min
• significant fraction in lower n
• n≲29: 3σ
• 4 events / 15 min
• τ ~ few ms
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p̄ + e+
p̄ + e−
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Compact pion tracking detector (2015)
13
36 cm
• Central calorimeter: BGO plate
• Position sensitive read out
• 2 layer hodoscope with SiPM readout
• Time resolution 840ps FWHM
• Bayes analysis due to low rate
Antiproton Cosmic shower
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Hydrogen beam setup
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Hydroen beam line test
setup@CERN
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beam focussing by superconducting
sextuple observed
polarized H source
cavity
SC sextupole
Qmass
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Spin-flip resonator
• f = 1.420 GHz, Δf = few MHz, ~ W power
• challenge: homogeneity over 10x10x10cm3@ λ=21cm
• solution: strip line
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Line shape by
optical Bloch equations
transverse field:
homogeneouslongitudinal field:
cos(z)
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H beam HFS: 1 transition
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• σ1(B), extrapolate B 0
• Fit the data with numerically
simulated line shape
shift of resonances in magn. field(a) 100 mA (b) 300 mA (c) 500 mA
H maser: Δν/ν ~10−12
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H-beam HFS result 1 transition
10 • extrapolations
Systematic• errors
Limitation•
Beam • velocity: broadening
1 • km/s 50 K
Err 2.9 ppb: 12x improvment over Kush et al.
Deviation from maser: 3 Hz < 1 error
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Outlook for H-beam
Also • 1 transition needed
Better• field homogeneity
SME: • effect only in 1
Improve• resolution
Statistics• still possible
Ramsey • method
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(Far) future experiments
Phase • 3: trapped H ̅
Hyperfine spectroscopy•
in an atomic fountain of
antihydrogen
needs trapping and laser •
cooling outside of
formation magnet
slow beam & capture in •
measurement trap
Ramsey method with •
d=1m
• Δf ~3 Hz, Δf/f ~ 2x10−9
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M. Kasevich, E. Riis, S. Chu, R. DeVoe,
PRL 63, 612–615 (1989)
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Non-minimal SME
• Operators of arbitrary
dimensions
• Non-relativisitc spherical
coefficients
• Shift only for -transition
(mF0)
• B direction dependence
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SummaryPrecise measurement of the hyperfine structure of •
antihydrogen promises one of the most sensitive tests of
CPT symmetry
First • “beam” of Hbar observed in field-free region
Next steps: optimize rate, check polarization, velocity•
HFS • in H-beam measured at 2.9 ppb for 1 transition
• 1 transition measurement in preparation
Proof• -of-principle for antihydrogen experiment
Potential • within non-minimal SME: access to transitions which
are not possible for maser
Higher • precision possible with dedicated hydrogen setup
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ERC Advanced Grant
291242
HbarHFS
www.antimatter.at
PI EW
THANK YOU FOR YOUR
ATTENTION
E. Widmann
Experiments in an atomic beam
Phase • 1 (ongoing): Rabi method
Phase • 2: Ramsey separated oscillatory fields
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Linewidth reduced by D/L
Δν/ν ~10−7
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Optical Bloch Equation solution
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10cm RF
10cm free
10cm RF
10cm RF
1 m free
10cm RF
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theoretical line shape
numerical •
solution of
optical Bloch
equation
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C. Sauerzopf, B. Kolbinger
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History of SMI• 1910 „Institut für Radiumforschung“
• 1st institute of “Kaiserliche Akademie
der Wissenschaften”
• Stefan Meyer was first director
• 2 Nobel prizes
• V. Hess (physics): cosmic rays
• G.v. Hevesy (chemistry): tracer
method
• 1987 Renamed to „Institute for
Medium Energy Physics“
• 2004: Renamed to “Stefan Meyer
Institute for Subatomic Physics”
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E. Widmann
CPT symmetry & cosmology
mathematical theorem, not valid e.g. in string theory, •
quantum gravity
possible hint: antimatter absence in the universe•
Big Bang • -> if CPT holds: equal amounts matter/antimatter
Standard scenario for • Baryogenesis (Sakharov 1967)
Baryon• -number non-conservation
C and CP violation•
Deviation from thermal equilibrium•
Currently known CPV •
not large enough
Other source of baryon •
asymmetry?
CPT non-conservation?
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E. Widmann
ELENA @ CERN-AD
Decelerator after AD • 5 MeV → 100 keV
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Energy range, MeV 5.3 - 0.1
Intensity of ejected beam 1.8 × 107
εx,y of extracted beam, π·mm·mrad, [95%],
standard
4 / 4
∆p/p of extracted beam, [95%], standard 8·10−3
Operation from 2017
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Other possibility:
foam and unitarity violation
10-35 m
After Weinberg 99
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Fundamental symmetries C,P,T
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•C: charge conjugation particle
↔ antiparticle
•P: parity: spatial mirror
•T: time reversal
CPT• theorem: consequence
of
Lorentz• -invariance
local interactions•
unitarity•
Lüders, Pauli, Bell, Jost • 1955
all QFT of SM obey CPT•
not necessarily true for string •
theory
CTP → particle/anitparticle: same masses, lifetimes, g-factors, |charge|,...
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Violations of fundamental symmetries
Historically it was believed that nature would conserve •
symmetries of space
Observed symmetry violations in weak interaction:•
Size of effect
Parity
violation
1956 Theory: Lee & Yang1957 ß-decay Wu et al.
π -> µ -> e decay100%
CP violation
1964 K0 decays: Cronin & Fitch2001 B decays: BELLE, BaBar
ε ~2.3 x 10–3
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“Model” for CPTV:
Standard Model Extension SME
• Spontaneous Lorentz symmetry breaking by (exotic) string vacua
• Note: there is a preferred frame, sidereal variation due to earth
rotation may be detectable
CPT & LORENTZ VIOLATION
LORENTZ VIOLATION
Modified Dirac eq. in SME
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Polarized H̅ beam from “cusp”
First antihydrogen production in • 2010
A. Mohri & Y. Yamazaki,
Europhysics Letters 63, 207
(2003).
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Y. Enomoto et al.
Phys. Rev. Lett 243401, 2010
achievable resolutionbetter • 10–6 for T ≤ 100 K
> • 100 H̄/s in 1S state into 4π needed
event rate • 1 / minute: background from cosmics, annihilations upstreams
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ASACUSA H̄ production
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B
U
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Full setup 2014
double cusp•
field ioniser•
•H ̄ detector
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new 2-layer hodoscope
with central BGO detector
MUSASHI p̄ trap
CUSP
Sextupole
Hodoscope
e+ trap
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H̅ formation setup 2012
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Nested Penning
trap
BGO detector
(calorimeter)
plastic scintillator (pions)
Cosmic rays in BGO
simulation vs. data
Hbar
π π
π
Fieldionization electrode
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H̄ HFS beam line 2012
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cusp trapcavity with
Helmholtz
coilssextupole
antihydrogen
detector
4.4 m
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H̄ HFS beam line 2014
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cusp trap
cavity with
Helmholtz
coilssextupole antihydrogen
detector
4.4 m
field
ionizer
±8.7 kV
→ 17.4 kV/cm
→n≧12 ionized
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Full setup 2014
45
new 2-layer
hodoscope
with central BGO
detector
MUSASHI p̄ trap
CUSP
Sextupole
Hodoscope
e+ trap
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Constant B-field inside cavity
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Helmholtz coils
Fluxgate sensors
magnetic shielding
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CPT detector
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Hodoscope 8 cm diameter
30 plastic scintillators
5x10 mm2
length 15 cm
2x SiPM readout
π
π
Hbar counter: 64 scint. + multi channel PMT
cosmic ray
Charged Pion Tracker
double-layer version under construction
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Simulation and data
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G4 studies:
simulation of H̅
trajectories in field
background creation
cosmics
estimation of transition
probabilities
effect of homogeneities
CUSP trap
Cavity
Sextupole
CPTdetector:
cosmic events in the
CPT detector (2012)simulation done at 2G, T=50K
needed: 2000 evts per scan C. Malbrunot
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Setup testing during LS1
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hydrogen beamline
developed at SMI
permanent sextupole for initial
polarization developed at CERN
1.4 T integrated field
10mm inner diameter
Permendur/permanent magnet
Polarized cold hydrogen beam:
Source of atomic hydrogen (microwave discharge)•Permanent sextupoles create polarized hydrogen beam•QMS detect GS hydrogen•Choppers connected to a lock• -in amplifier for noise reduction
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ASACUSA H̅ production
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p
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B beam source schematic
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ASACUSA Hbar production
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Recent results
Background•
• e− cooling of p ̄
mix • e− and p ̄
Scheme • 1
• e− cooling of p ̄
mix • e+ and p ̄
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1st H resonance scan: σ1
No magnetic shielding•
Earth magnetic field of •
30 μT
Cavity L=• 10.5 cm
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ν(MHz) Error (Hz)/
deviation
Rel error/
deviation
Resonance
center
1 420.406 354 133 9E-08
νHF (B=0) 1 420.405 751 768 603 4E-07
Simulated spectra
σ1
10 kHz = 7 ppm
28.04.2014Hydrogen
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H beam setup
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Antihydrogen setup
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PR E P A R A T IO N S F O R π1
MEASUREMENT
SME: sensitive to CPTV•
better field homogeneity needed•
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