Observation of the 1S-2S Transition in Antihydrogen
ALPHA
Dirk van der WerfSwansea University
CEA-Saclay
D P van der Werf Seoul, 9 February 2017Observation of the 1S-2S Transition in Antihydrogen 2
Check CPT conservation
Baryon asymmetry
What do we want to do
Standard model extension (SME):
Assume some violation, i.e. Lorentz symmetry is broken in a particular way, then in a number of cases there will be a difference between the some of the properties between matter and antimatter (see e.g. V.A. Kostelecký and S. Samuel, Phys. Rev. D 39 (1989) 683)
D P van der Werf Seoul, 9 February 2017Observation of the 1S-2S Transition in Antihydrogen 3
Borrowed from Stefan Ulmer
D P van der Werf Seoul, 9 February 2017Observation of the 1S-2S Transition in Antihydrogen 4
Goals
• Compare the spectra of H and , testing CPT.
‣ Records for Hydrogen- 1S-2S transition known to 4.2 parts in 1015.
C.G. Parthey et al. Phys. Rev. Lett. 107, 203001 (2011)- Ground state hyperfine transition known to 1.4 parts in 1012.
H. Hellwig et al. Instrumentation and Measurement, IEEE Transactions 19, 200 (1970).
CPT theorem -> particles and antiparticles must have equal energy levels of bound states
D P van der Werf Seoul, 9 February 2017Observation of the 1S-2S Transition in Antihydrogen 5
Penning Trap
Trap for charged particles
D P van der Werf Seoul, 9 February 2017Observation of the 1S-2S Transition in Antihydrogen
Magnetic Field [T]
0 0.2 0.4 0.6 0.8 1 1.2 1.4
rela
tive e
nerg
y in fre
quency u
nits [G
Hz]
-20
-15
-10
-5
0
5
10
15
20
〉a|
〉b|
〉c|
〉d|
adfbcf
trappable 'low-field seeking' states
〉⇓↓ = |〉d |〉⇑↓ = |〉c|
untrappable 'high-field seeking' states
〉⇑↑ = |〉b |〉⇓↑ = |〉a|
spin flip frequencies
6
Breit-Rabi Diagram
To measure accurately electronic transition a trap for neutral atoms is necessary:use the spin state of the antihydrogen atom
D P van der Werf Seoul, 9 February 2017Observation of the 1S-2S Transition in Antihydrogen 7
Magnetic trap
0
0.2
0.4
0.6
0.8
1
0 0.2 0.4 0.6 0.8 1
B/B
w
r/rw
Quadrupole
Sextapole
Octupole
DecapoleB/Bw = 0.025
D P van der Werf Seoul, 9 February 2017Observation of the 1S-2S Transition in Antihydrogen 8
Magnetic field measurements
Cyclotron excitation
Heat non-neutral electron plasma
Change quadrupole mode frequency f2
Typical measurement
D P van der Werf Seoul, 9 February 2017Observation of the 1S-2S Transition in Antihydrogen 9
catch and accumulation
Installed: ~150k p/shot, >10h lifetimeh
Entries 209
Mean 1.827
RMS 3.653
-20 -15 -10 -5 0 5 10 15 200
2
4
6
8
10
12
14
16
18
20
hEntries 209
Mean 1.827
RMS 3.653
h
SiliconEvent.RunTime308 308.2308.4308.6308.8 309 309.2309.4309.6309.8 310
Silic
onEv
ent.V
F48T
imes
tam
p
308
308.5
309
309.5
310
SiliconEvent.VF48Timestamp:SiliconEvent.RunTime {SiliconEvent.RunTime > 308.0892 && SiliconEvent.RunTime < 310.0886 && SiliconEvent.NVertices >0}
SisEvent.RunTime308 308.5 309 309.5 310
0
5
10
15
20
25
30
35
SisEvent.RunTime {SisEvent.CountsInChannel*(SisEvent.RunTime > 308.0842 && SisEvent.RunTime < 310.0936) }
htempEntries 456
Mean 308.5
RMS 0.3829
SisEvent.RunTime {SisEvent.CountsInChannel*(SisEvent.RunTime > 308.0842 && SisEvent.RunTime < 310.0936) }
-5 -4 -3 -2 -1 0 1 2 3 4 5-5
-4
-3
-2
-1
0
1
2
3
4
5 hxyEntries 209
Mean x -0.03025
Mean y 0.1054
RMS x 1.448
RMS y 1.362
0
0.5
1
1.5
2
2.5
3
3.5
4hxyEntries 209
Mean x -0.03025
Mean y 0.1054
RMS x 1.448
RMS y 1.362
hxy
SiliconEvent.NTracks1 2 3 4 5 6 7 8 9
0
10
20
30
40
50
60
70
SiliconEvent.NTracks {SiliconEvent.RunTime > 308.0892 && SiliconEvent.RunTime < 310.0886 && SiliconEvent.NVertices >0}
htempEntries 209
Mean 3.292
RMS 1.304
SiliconEvent.NTracks {SiliconEvent.RunTime > 308.0892 && SiliconEvent.RunTime < 310.0886 && SiliconEvent.NVertices >0}
SisEvent.RunTime308 308.5 309 309.5 310
0
1
2
3
4
5
6
7
8
SisEvent.RunTime {SisEvent.CountsInChannel*(SisEvent.RunTime > 308.0842 && SisEvent.RunTime < 310.0936) }
htempEntries 254
Mean 308.7
RMS 0.4308
SisEvent.RunTime {SisEvent.CountsInChannel*(SisEvent.RunTime > 308.0842 && SisEvent.RunTime < 310.0936) }
ALPHA
formation, trap and spectroscopy
D P van der Werf Seoul, 9 February 2017Observation of the 1S-2S Transition in Antihydrogen 10
D P van der Werf Seoul, 9 February 2017Observation of the 1S-2S Transition in Antihydrogen 11
Laser Paths
D P van der Werf Seoul, 9 February 2017Observation of the 1S-2S Transition in Antihydrogen 12
D P van der Werf Seoul, 9 February 2017Observation of the 1S-2S Transition in Antihydrogen 13
Cosmic
D P van der Werf Seoul, 9 February 2017Observation of the 1S-2S Transition in Antihydrogen 14
Two track
D P van der Werf Seoul, 9 February 2017Observation of the 1S-2S Transition in Antihydrogen 15
Three Track
D P van der Werf Seoul, 9 February 2017Observation of the 1S-2S Transition in Antihydrogen 16
Schematic Overview
D P van der Werf Seoul, 9 February 2017Observation of the 1S-2S Transition in Antihydrogen 17
Laser Setup
The long-term average laser frequency at 972 nm is determined to a relative accuracy of 8 × 10-13
D P van der Werf Seoul, 9 February 2017Observation of the 1S-2S Transition in Antihydrogen 18
Procedure:
1. Make and Trap antihydrogen2. Pulsing axial electric fields to remove
antiprotons 3. Holding the trapped anti-atoms for 600 s4. ramping down the trapping fields
Experiment
Three types of trials
1. ‘On resonance’: d–d transition and then the c–c transition are driven for 300 s each.
2. ‘Off resonance’: same as above, but the laser is detuned 200 kHz down
3. ‘No laser’: no laser radiation is present during the 600-s hold time.
During hold times, electrostatic blocking potentials so that anti- protons can only radially escape.
11 sets, change of measurement order between sets.fc−c = 2,466,061,707,104(2) kHz
fd−d = 2,466,061,103,064(2) kHz
D P van der Werf Seoul, 9 February 2017Observation of the 1S-2S Transition in Antihydrogen 19
Simulation for 1 W laser power
D P van der Werf Seoul, 9 February 2017Observation of the 1S-2S Transition in Antihydrogen 20
Result 1
The MVA used for the 1.5-s shutdown window yields a cosmic ray background rate of 0.042 ± 0.001 s−1
Reconstruction efficiency: 0.688 ± 0.002
D P van der Werf Seoul, 9 February 2017Observation of the 1S-2S Transition in Antihydrogen 21
Result 2
The MVA used for the 1.5-s shutdown window yields a cosmic ray background rate of 0.0043 ± 0.0003 s−1
Reconstruction efficiency: 0.376 ± 0.002
D P van der Werf Seoul, 9 February 2017Observation of the 1S-2S Transition in Antihydrogen 22
Time evolution of the dataset.
D P van der Werf Seoul, 9 February 2017Observation of the 1S-2S Transition in Antihydrogen 23
• The difference between the on- and off-resonance totals of 52 ± 10 (C-test19, one-sided P value of 2.2 × 10−7).
• Our result is consistent with CPT invariance at a relative precision of about 2 × 10−10,assuming the same line shape as for hydrogen
• Sensitivity ~ 2 × 10−18 GeV
• Next year full line shape measurement
Conclusion + Outlook
D P van der Werf Seoul, 9 February 2017Observation of the 1S-2S Transition in Antihydrogen 24
Funding
D P van der Werf Seoul, 9 February 2017Observation of the 1S-2S Transition in Antihydrogen 25
ALPHA
TRIUMF
D E N M A R KD E N M A R K
Universidade Federal do Rio de JaneiroBRASIL
NRCN
Nuclear Research Center Negev