High-precision measurements of the fundamental properties of the

antiprotonHiroki Nagahama

on behalf of the BASE collaboration

PSAS’ 2016, Jerusalem 26/May

Table of contents

• Goal of BASE

• Principle of CPT invariance

• Result from 2014 beamtime(High-precision comparison of the antiproton-to-proton charge-to-mass ratio)

• Update on 2015 beamtime(Statistical spinflips of a single trapped antiproton) <-Main topic of this talk

Our goal

25 GeV/c protons

3.5 GeV/c antiprotons

5.3 MeV antiprotons

BASE aims at stringent tests of CPT invariance in the ADTheory: fundamental properties of matter/antimatter identical. Experiment: We should test that!

Different CPT tests

10-21

10-18

10-15

10-12

10-9

10-6

10-3

100

relative precision

positron g

muon g

antiproton q/m

antiproton g

kaon m

antihydrogen 1S/2S

antihydrogen GS HFS

antideuteron m/q

antihelium m/q

CERNAD

CERNALICE

RecentPastPlanned

muon g

Nature Physics(10.1038/nphys3432)

S. Ulmer et al., Nature 524 196 (2015)

Already up to a relative precision of 10−18 CPT test was succeeded… why do we still want to measure?=> Necessary to think about a concept of CPT violation

Concept of CPT violation

Add CPT violating term to a Hamiltonian based on Standard Model

Absolute energy change ∆𝐸 will be derived

𝐻′ = 𝐻𝑆𝑀 + ∆𝑉

CPT violating termSystem based on SM

Absolute energy resolution (normalized to m-scale) is the relevant measure to characterize sensitivity of an experiment to CPT violation.Single-particle measurements in Penning traps give high energy resolution.

< ψ∗|∆𝑉|ψ >= ∆𝐸

Relative precision Energy resolution

Kaon ∆𝑚 ~10−18 ~10−9 eV

p- p q/m ~10−11 ~10−18 eV

p- p g-factor ~10−6 ~10−12 eV

BASE aims to improve with 10−9 relativeprecision

Kostelecky et al.

different C’s

Main Tool: Penning Trap

Axial

Magnetron

Modified Cyclotron

22

0 2( , )2

z V c z

0ˆB B z

axial confinement:

radial confinement:

B

0

k

k

V

V

V

( )z

680kHz

8kHz

28,9MHz

z

2 2 2

c z

Invariance-Relation

Axial MotionModified Cyclotron Motion

Magnetron Motion

B

z

L. S. Brown and G. Gabrielse,Phys. Rev. A 25, 2423 (1982).

Frequency Measurements

Rp

Resonator

Low noiseamp

FFT

Measurement of tiny image currents induced in trap electrodes

645300 645400 645500 645600 645700

-130

-125

-120

-115

-110

-105

-100

-95

Sig

na

l (d

Bm

)

Frequency (Hz)

Axially excited, trapped

antiprotons

In thermal equilibrium:– Particles short noise in parallel

– Appear as a dip in detector spectrum

– Width of the dip number of particles

Measurements in thermal equilibrium tiny volumina / homogeneous condititions

793100 793200 793300 793400 793500 793600

-125

-120

-115

-110

-105

-100

-95

-90

Sig

nal (d

Bm

)

Frequency (Hz)

ND

q

m

R

2

2

1

Enables cyclotron frequency measurement at 1 ppb

The BASE Trap

Access to beamlineParticles not continuously

available

Reservoir Trap: Stores a cloud of antiprotons, suspends single antiprotons for measurements. Trap is “power failure save”.

Precision Trap: Homogeneous field for frequency measurements, B2 < 0.5 mT / mm2

Cooling Trap: Fast cooling of the cyclotron motion, 1/g < 4 s (10 x improved)

Analysis Trap: Inhomogeneous field for the detection of antiproton spin flips, B2 = 300 mT / mm2

Double Trap

Single particle extraction from the reservoir

• Superimpose a constant electric field over the Penning trap potential

Measurement with an antiprotoncloud

200 particle/50 cyclesNo particle loss

• Count particles by measuring line-width of the particle dip.

0 2 4 6 8 10

0

2

4

6

8

10

12

14

16

18

Reservoir Trap

3d

B W

idth

(H

z)

Number of Particles

Theoretical: 1.68 Hz

Experimental: 1.65(09) Hz

645200 645220 645240 645260 645280 645300

-140

-135

-130

-125

-120

-115

-110

Sig

nal (d

Bm

)

Frequency (Hz)

C. Smorra, et al., Int. J. Mass Spectrom. (2015), http://dx.doi.org/10.1016/j.ijms.2015.08.007

Antiprotons in the BASE trap stack

Beamtime 2015: Shuttling along entire trap stack (20cm/5s) established.

Current situation

5 antiprotons in reservoir trap Single antiproton in precision trap Single antiproton in analysis trap

The experiment using antiprotons is still ongoing in the AD!!!!

Measurement 1 (q/m)

B

B

BASE is an experiment using an advanced Penning trap.Single particle sensitivity, confines particle within ~μm3

ν𝑐, 𝑝ν𝑐,𝑝

=𝑞 𝑝/𝑚 𝑝

𝑞𝑝/𝑚𝑝B

m

qc

2

1

Ratio of cyclotron frequencies leads to CPT test of charge-to-mass ratio comparison

S. Ulmer et al., Nature 524 196 (2015)G. Gabrielse et al., Phys. Rev. Lett. 82 3198 (1999)

Measurement cycle is triggered by the antiproton injection into the ADOne BASE charge-to-mass ratio measurement is by 50 times faster than achieved in previous proton/antiproton measurements.

AD cycle

2222

zc

First high-precision mass spectrometer which applies this fast shuttling technique

Measurement

Most precise q/m comparison for proton and antiproton

(𝑞/𝑚) p

(𝑞/𝑚)p−1 = 1 69 × 10−12

• In agreement with CPT conservation• Exceeds the energy resolution of

previous result by a factor of 4*.

Final result

*S. Ulmer et al., Nature 524 196 (2015)G. Gabrielse et al., Phys. Rev. Lett. 82 3198 (1999)

6521 frequency ratios

Measurement 2 (g-factor)

2L

p

eg B

m

L

B

c

p

eB

m

Larmor Precession

g-factor measurement reduces to measurement of a frequency ratio

g: magnetic Moment in units of

nuclear magneton

S. Ulmer, A. Mooser et al. PRL 106, 253001 (2011)

S. Ulmer, A. Mooser et al. PRL 107, 103002 (2011)

simple difficult

Cyclotron Motion

Larmor Frequency

Energy of magnetic dipole in magnetic field Φ𝑀 = −(μ𝑝 ⋅ 𝐵)

𝐵𝑧 = 𝐵0 + 𝐵2 (𝑧2 −

ρ2

2)Leading order

magnetic field correction

Spin dependent quadratic axial potential Axial frequency becomes function of spin state

Δν𝑧~μ𝑝𝐵2𝑚𝑝ν𝑧

: = α𝑝𝐵2ν𝑧

Very difficult for the proton/antiproton system:

𝐵2~300000 T/m2

Most extreme magnetic conditions ever applied to single particle. ∆𝜈𝑧~170 mHz

Measurement based on continuous Stern Gerlach effect.

The Challenge

Typical axial frequency: 700 kHz

Δν𝑧~μ𝑝𝐵2𝑚𝑝ν𝑧

≔ 0.4 ∙ 𝜇𝐻𝑧 ∙ 𝐵2

We use: 𝐵2 = 300000 𝑇/𝑚2

170 mHz out of 700 kHz

Magnetic bottle coupling: -> 1 Hz/μeV

One cyclotron quantum jump (70 neV) shifts axial frequency by 70mHz

Tiny heating of the radial mode results in significant fluctuation of the axial oscillation frequency

Heating rates scale with the cyclotron quantum number!

Our heating rates correspond to noise on electrodes of some pV/Hz1/2.

For further details, see talk by A. Mooser tomorrow

𝑑𝑛+𝑑𝑡

∝ 𝑛+Γ𝑖→𝑓2

Progress Analysis Trap 2015

-4 -3 -2 -1 0 1 2 3 4

0

5

10

15

20

25

30

35

40

Co

unts

Frequency Fluctuation (Hz)

First Particle

Intermediate

Recent Status

0 20 40 60 80 100 120 140 160

-10

-8

-6

-4

-2

0

2

4

6

8

10

Axia

l F

req

ue

ncy -

67

485

0 (

Hz)

Time (min)

First Particle

Intermediate

Current Status

20 40 60 80 100 120 140 160

100

150

200

250

300

350

400

Axia

l F

requency J

itte

r (m

Hz)

Averaging Time (s)

20151123 (NC)

20151126 (NC)

20151127 (NC)

20151128 (NC)

20151129 (AC)

20151105(NC, proton)

20151202

20151202(FBAxOFF)

20151206(after ground cleaning)

Cyclotron heating rate:< 1 quantum transition in 240sIn this case: Single spin flip resolution

In the magnetic bottle: need to resolve spin flip induced axial frequency jumps of 180 mHz:

- Trap cleaning- Proper grounding- Temperature of the cyclotron detector

3 weeks

Statistical Detection of Spin Flips

Measure axial frequency stability:

1) reference measurement with detuned drive on

2) measurement with resonant drive on.

Spin flips add up

-20 0 20 40 60 80 100 120 140 160 180 200

-0.02

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

0.22

0.24

0.26

0.28

0.30

0.32

0.34

Axia

l Jitte

r (H

z)

Measurement

Resonant

Off-Resonant

Cumulative measurement:

Black – frequency stability with superimposed spin flips.

Red – background stability

ΞSF = Ξref2 + 𝑃𝑆𝐹Δ𝜈𝑧,𝑆𝐹

2

S. Ulmer, et al., Phys. Rev. Lett 106, 253001 (2011)

ΞSF

Ξref

Blue dash line - Axial frequency changedue to spinflips

Resonances

CyclotronLarmor

Work in progress, experiment is still ongoing

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

0.6

Sp

in F

lip

Pro

ba

bility

Drive Frequency -L (Hz)

0.0

0.3

0.6

0.9

1.2

Axia

l F

luctu

ation (

Hz)

Drive Frequency - + (Hz)

Summary

• In 2014, we compared the charge-to-mass ratio of antiproton-to-proton with unprecedented precision of 69 ppt. It has a factor of 4 higher energy resolution than the previous result.

• In 2015, we succeeded to observe spinflips of a single antiproton in the analysis trap.

• We still have in total 7 antiprotons in our trap system.

• Measurement of 𝑔 𝑝 is ongoing.

K. Blaum, Y. Matsuda, C. Ospelkaus, W. Quint, J. Walz, Y. Yamazaki

Thank you for your attention!

Measurement scheme

• After the antiproton injection by the AD, a cloud which consists of manyantiprotons and H−ions is prepared.

• Extracted a single antiproton and a single H−ion from the cloud.• Cyclotron frequency of a single particle is measured in Measurement trap, while

the other one is parked in Upstream/Downstream park electrode.

H- ions: perfect proxies for protons • Measure free cyclotron frequencies

of antiproton and H- ion.

B B

antiproton H- ion

𝑅 =νc p

νcH−=

(𝑞/𝑚) p

(𝑞/𝑚)H−x𝐵/2π

𝐵/2π=

(𝑞/𝑚) p

(𝑞/𝑚)H−

• Take a ratio of measured cyclotron frequency of antiproton

νc p to H- ion νcH− => reduces to antiproton to proton charge-to-

mass ratio

𝑚H− = 𝑚p(1 + 2𝑚e

𝑚p−𝐸b𝑚p

−𝐸a𝑚p

+𝛼pol,H− 𝐵0

2

𝑚p)

Magnetic field cancels out!

*using proton=>opposite charge=>position in the trap changes

Rtheo = 1.0010892187542(2)

Comparable measurements were carried out by the TRAP collaboration in 1990 to 1998

TRAP Collaboration, Phys. Rev. Lett. 82, 3198 (1999).

Larmor Frequency Measurement

Spin is detected and analyzed via an axial frequency measurement

Larmor Frequency is measured by repetition and evaluating the spin flip probabilityTogether with cyclotron frequency measurement:

S. Ulmer et al., Phys. Rev. Lett 106, 253001 (2011)

g/2 = 2.792 848 (24) Rodegheri et al., NJP 14, 063011, (2012)

g/2 = 2.792 846 (7) di Sciacca et al., PRL 108, 153001 (2012)

Statistical Method:Limited to the ppm level due to the strong magnetic bottle.

Statistical Method