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