9th Pioneer project seminar

Wednesday 25 Feb 2015, 11:00 → 12:00 Asia/Tokyo

seminar room (435,437) (Main building)

Title:The magnetic moments of the proton and the antiproton Speaker: Dr. A. Mooser Affiliation: RIKEN　Ulmer Initiative Research Unit Schedule: Wed 25th Feb 2015, AM11:00-12:00 Place: main building seminar room (435,437)　RIKEN Language: English Abstract: One of the fundamental properties of the proton/antiproton is the spin magnetic moment /µ/*/_p /*_, */_pbar /*. In case of the proton the most precise value of /µ/*/_p /*was based on spectroscopy of atomic hydrogen conducted 42 years ago. Significant theoretical bound-state corrections had to be applied to indirectly determine /µ/*/_p /*with a relative precision of 9 ppb [1]. Very recently, we improved this value by a factor of 2.5 by directly measuring /µ/*/_p /*with a single proton in a Penning trap [2]. In case of the antiproton /µ/*/_pbar /*is known with a relative precision at the ppm level [3]. By applying our methods to the antiproton, we aim at a thousandfold improved measurement of /µ/*/_pbar /*. To this end, we are setting up the BASE experiment at the antiproton decelerator of CERN [4], to eventually provide a stringent test of CPT-invariance with baryons. In a Penning trap the measurement of /µ/*/_p /*_, */_pbar /*is based on the determination of the two frequencies of a single proton/antiproton, the Larmor and the cyclotron frequency. Based on a statistical detection of spin transitions we measured the Larmor frequency of a single proton for the first time [5], which resulted in a direct determination of /µ/with a fractional precision at the ppm level [6]. The precision was improved significantly by using a double Penning-trap technique. This required the detection of single spin flips, which was achieved with an improved apparatus and by using Bayesian data analysis [7]. Our developments ultimately culminated in the most precise and first direct measurement of/µ/*/_p /*. For BASE a significantly improved setup using a state of the art trapping system has been developed. After a construction phase of about 1.5 years, we successfully commissioned our four-Penning trap system with antiprotons provided by the antiproton decelerator of CERN. Within our first experiments we were able to demonstrate cyclotron frequency measurements at the 100ppt level, which is precise enough to perform the aimed antiproton magnetic moment measurement. A detailed status update will be presented. *References*** [1] S. G. Karshenboim and V. G. Ivanov, Phys. Lett. B 566, 27 (2003). [2] A. Mooser et al., Nature 509, 59 (2014.). [3] J. DiSciacca et al., Phys. Rev. Lett. 110, 130801 (2013). [4] C. Smorra /et al./ Hyperfine Interact. DOI: 10.1007/s10751-014-1018-7 (2014). [5] S. Ulmer et al., Phys. Rev. Lett. 106, 253001 (2011). [6] C. C. Rodegheri et al., New J. Phys. 14, 063011 (2012). [7] A. Mooser et al., Phys. Rev. Lett. 110, 140405 (2013).