Challenging the Standard Model by the precise comparisons of the fundamental properties of protons and antiprotons.
Dr Stefan Ulmer, RIKEN, Japan
The Standard Model (SM) of particle physics is known to be incomplete. This inspires various searches for physics beyond, among them are tests of charge, parity, time (CPT) invariance that compare the fundamental properties of matter/antimatter conjugates at low energy and with high precision.
The Japanese/German BASE collaboration at the antiproton decelerator of CERN targets high-precision comparisons of the fundamental properties of antiprotons and protons, namely, charge-to-mass ratios and magnetic moments. To perform these tests we have developed an advanced Penning trap spectrometer which enabled the most precise measurement of the proton magnetic moment with a fractional precision of 3.3 parts in a billion, the most precise comparison of the proton-to-antiproton charge-to-mass ratio, with a fractional precision of 69 parts in a trillion, as well as the most precise measurement of the magnetic moment of the antiproton (0.8 p.p.m). Recent improvements in the stability of the apparatus enabled us to observe single antiproton spin transitions, based on this achievement a 100-fold improved measurement of the antiproton magnetic moment will become possible. This talk will summarise our most recent results and give an overview on the perspectives of BASE in the ELENA era.
GBAR: leading the dance with ELENA's antiprotons
Dr Pauline Comini, ETH Zürich, Switzerland
In order to observe the free fall of antihydrogen atoms, hence measuring the gravitational acceleration of antimatter on Earth, the GBAR experiment aims at producing these antiatoms with velocity of a few m.s-1. This will be achieved by implementing the sympathetic cooling of antihydrogen positive ions, an original idea proposed by J. Walz & T. Hänsch.
In its race toward ultracold antihydrogen atoms, GBAR has found a precious and necessary partner in the new antiproton decelerator ring, ELENA. This talk begins with a review of the different stages allowing GBAR to transform the 100 keV ELENA antiprotons into neV antihydrogen atoms, with particular attention to the ELENA parameters that influence most the design of the experiment.
As ELENA’s first user, GBAR is currently getting ready to receive the first 100 keV antiprotons. The present status of the installation in the AD hall and the planning of the coming years are then detailed. The recording of GBAR’s first antihydrogen free falls will provide a 1% precision on the measurement of g ̅; in order to further improve this precision to 0.01%, a future upgrade of the experiment is already being studied.
Finally, it is worth noting that each antiproton bunch delivered by ELENA to GBAR also bears the potentiality of a few hundreds of antihydrogen atoms, while a large part of the antiprotons remains untouched. Ideas proposed to exploit these beams are also sketched.
The ELENA facility
Dr Christian Carli, CERN, Switzerland
The CERN Antiproton Decelerator AD provides antiproton beams with a kinetic energy of 5.3 MeV to an active users community. This extraction energy is the lowest one possible under good conditions with the given circumference of the AD.
The Extra Low Energy Antiproton ring (ELENA) is a small synchrotron with a circumference a factor 6 smaller than the AD to further decelerate antiprotons from the AD from 5.3 MeV to 100 keV. Controlled deceleration in a synchrotron equipped with an electron cooler to reduce emittances in all three planes will allow the existing AD experiments to increase substantially their antiproton capture efficiencies and render new experiments possible.
ELENA ring commissioning is taking place at present and first beams to a new experiment installed in a new experimental area are foreseen this year. The transfer lines from ELENA to existing experiments in the old experimental area will be installed during CERN long Shutdown 2 (LS2) in 2019 and 2020. The status of the project and ring commissioning will be reported.