High precision measurement of the antiproton g-factor Toya - - PowerPoint PPT Presentation

High precision measurement

• f the antiproton g-factor

Toya Tanaka,U-Tokyo
 for the BASE collaboration

2/3/2016 ICEPP winter school

Outline

• Motivation
• penning trap and Measurements
• BASE apparatus and current

situation

• Ground loop detection
• Summery

Why should we test CPT invariance?

Experiment : Measure the fundamental properties of matter/antimatter in high precision. Aim of BASE

• precise measurement of proton-antiproton g-factor

by penning trap method

~ µ = g q 2m ~ S

g: magnetic Moment in units of nuclear magneton

CPT invariance matter/antimatter assymmetry

CPT tests

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relative precision positron g muon g antiproton q/m antiproton g kaon m Δ antihydrogen 1S/2S antihydrogen GS HFS

Recent Past Planned

S.Ulmer et al.., Nature. 2015;524:196-199 (2015)

Measurements

B

Larmor Precession g-factor measurement reduces to measurement of a frequency ratio
 In principle a very simple experiment –> full control, no theoretical corrections

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)

Cyclotron Motion

ωL

g: dimensionless

νc = 1 2π q mB

νL = g 4π q mB

g 2 = νL νc

Cyclotron frequency and penning trap

2 2 0 2

( , ) 2 ρ ρ " # Φ = − & ' ( ) z V c z

0 ˆ

= B B z

axial confinement:

radial confinement:

k k

V V V

B

( ) z Φ

2 2 2 c z

ν ν ν ν

+ −

= + +

• L. S. Brown and G. Gabrielse,

• Phys. Rev. A 25, 2423 (1982).

Invariance-Relation:

3 eigenfrequencies of cyclotron frequency

• axial frequency
• modified cyclotron and magnetron frequency

νz = r 2qC2 m V0

ν± = 1 2(νc ± p νc2 − 2νz2)

Axial(軸方向) Magnetron(マグネトロン) Modified Cyclotron(トラップサイクロトロン)

680kHz 8kHz 28,9MHz

z

ν ν ν

− +

= = =

Frequency Measurements

Measurement of tiny image currents induced in trap electrodes

645300 645400 645500 645600 645700

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Signal (dBm) 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

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Signal (dBm) Frequency (Hz)

N D q m R ⋅ " # $ % & ' = Δ

2

2 1 π ν Enables cyclotron frequency measurement at ̴̴1 ppb

Larmor Frequency

Energy of magnetic dipole in magnetic field Leading order
 magnetic field correction Spin dependent quadratic axial potential


Axial frequency becomes function of spin

state Very difficult for the proton/antiproton system

Most extreme magnetic conditions ever applied to single particle. Measurement based on continuous Stern Gerlach effect

∆νz ∼ 170mHz(νz ∼ 660kHz)

Larmor Frequency Measurement

Larmor Frequency is measured by repetition and evaluating the spin flip probability

• 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

Spin is detected and analyzed via an axial frequency measurement

Together with cyclotron frequency measurement:

BASE apparatus

Picture of BASE apparatus

BASE double penning trap

BASE double penning trap

Signals observed in all trap and g-factor measurement is still ongoing.

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

RT PT AT

Ground loop detection

• By ground loop, extra low signal will be on the

background and the voltage fluctuation directly affects to the axial frequency!

• To avoid it, we should plug out suspect cables or

detect the ground loop.

νz = r 2qC2 m V0

∆V V0 < 10−6

∆νz ∼ 170mHz(νz ∼ 660kHz)

• P. M. Bellan, Simple system for locating ground loops, Rev. Sci.
• Instrum. 78, Art. No. 065104 (2007)

Making prototype

• Under Construction…

Summery

• For measuring g-factor, only Cyclotron and

Lamour frequency should be measured. Principally simple but practically difficult.

• By Double penning trap method, the

antiproton g-factor measurement is now

• ngoing even off beam time.
• For further measurement, there are many

things to be improved, e.g ground loop detector.

The BASE Team

• K. Blaum, Y

. Matsuda,

• C. Ospelkaus, W. Quint,
• J. Walz, Y

. Yamazaki

• S. Ulmer

RIKEN

• C. Smorra

CERN / RIKEN

• A. Mooser

RIKEN

• S. Sellner

RIKEN

• T. Tanaka

RIKEN / Tokyo

• T. Higuchi

RIKEN / Tokyo

• H. Nagahma

RIKEN / Tokyo

• G. Schneider

U - Mainz

Thanks for your attention!

• M. Besirli

RIKEN

• M. Borchert

U - Hannover

• J. A. Harrington

RIKEN

Appendix:results of the proton & antiproton g-factor

Appendix: Concept of CPT violation

• CPT violating term

System 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.

Relative precision Energy resolution

Kostelecky et al.

different C’s

Appendix: How to measure ν±

νl

νr

ν+ = νrf + νl + νr − νz

ν− = νz2 2ν+ (ν+ << νz << ν−)