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Penning trap measurement of the magnetic moment of the antiproton. Wolfgang Quint (w.quint@gsi.de). GSI Darmstadt, Germany. Villars Meeting, Sept. 25, 2004. m p : magnetic moment g p : g-factor s: spin m N : nuclear magneton. B. g-Factor of the antiproton.
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Penning trap measurement of the magnetic moment of the antiproton Wolfgang Quint (w.quint@gsi.de) GSI Darmstadt, Germany Villars Meeting, Sept. 25, 2004
mp: magnetic moment gp: g-factor s: spin mN: nuclear magneton B g-Factor of the antiproton proton: gp = 2×2.792847337(29)* accuracy: 10-8 antiproton: gpbar = 2×2.800(8)* accuracy: 10-3 *Particle Data Group
cyclotron frequency: g-Factor of the antiproton B: magnetic field in Penning trap Larmor precession frequency:
Positron (nc , ) (nc , ) (1 , ) (2 , ) CPT (0 , ) (1 , ) (0 , ) anomaly transition Figure of merit for CPT violation (Bluhm, Kostelecky, Russell): + - - w - w £ × 2 21 ( ) / 2 m c 1 , 2 10 h a a e Geonium: Single electron in a Penning trap Electron (nc , ) (nc , ) (1 , ) (2 , ) (0 , ) (1 , ) (0 , ) anomaly transition (nc: cyclotron quantum number) (Dehmelt, Van Dyck)
Antiproton (nc , ) (nc , ) CPT (nc , ) spinflip transition spinflip transition (nc , ) Figure of merit for CPT violation (Bluhm, Kostelecky, Russell): Single antiproton in a Penning trap Proton (expected accuracy)
z = 1 MHz B C R L U = I R end cap dEp/dt = Pcool = -I2R cooling compensation electrode ring electrode compensation electrode end cap Electronic detection of a single antiproton c2-2z2+2
Cyclotron resonance of a single antiproton measured at LEAR, 1993 (G. Gabrielse, D. Phillips, W. Quint)
Ion cyclotron frequency: G-Factor of the bound electron in H-like ions B Larmor precession fre- quency of bound electron: new value for the electron mass
Quantum jumps of a single hydrogen-like ion • Axial frequency depends on spin direction due to continuous Stern-Gerlach effect
Continuous Stern-Gerlach effect spin has magnetic moment magnetic bottle: B(z) = B0 + B2z2 magnetic energy: Emagn(z) = B0B2z2 attractive or repulsive force axial frequency = f (spin direction
s e E n l i e l c d t r l i e c i f p c o i t t e e n n t g i a a l M s h a p e Double-Trap Technique for g-Factor Measurements • Principle: • Excitation of spin-flip in precision trap (homogeneous magnetic field) • Detection of spin-flip in analysis trap (inhomogeneous magnetic field for spin-flip detection) analysis trap precision trap
G-Factor of bound electron in highly charged ions experiment: g(12C5+) = 2.001 041 596(1)(4) theory: g(12C5+) = 2.001 041 591(7) statisitical error: dg/g = 2·10-9 total error: dg/g = 2·10-9 (limited by the knowledge of me) • Measurement of the g-factor of the bound electron • with an accuracy of 7 x 10-10 T. Beier et al., PRL 88, 011603 (2002) V. Yerokhin et al., PRL 89, 143001 (2002)
Conclusions • Measurement of the magnetic moment of the • bound electron with an accuracy of 7 x 10-10. • This experimental technique can be employed for • the measurement of the magnetic moment of the • antiproton. Improvement of accuracy in gpbar by six orders of magnitude Important test of CPT invariance for baryons