BASE (Baryon Antibaryon Symmetry Experiment), AD-8, is a multinational collaboration at the

Antiproton Decelerator The Antiproton Decelerator (AD) is a storage ring at the CERN laboratory near Geneva. It was built from the Antiproton Collector (AC) to be a successor to the Low Energy Antiproton Ring (LEAR) and started operation in the year 2000. Antipro ...

facility at CERN, Geneva. The goal of the Japanese and German BASE collaboration are high-precision investigations of the fundamental properties of the

antiproton The antiproton, , (pronounced ''p-bar'') is the antiparticle of the proton. Antiprotons are stable, but they are typically short-lived, since any collision with a proton will cause both particles to be annihilated in a burst of energy. The exi ...

, namely the

charge-to-mass ratio The mass-to-charge ratio (''m''/''Q'') is a physical quantity relating the ''mass'' (quantity of matter) and the ''electric charge'' of a given particle, expressed in units of kilograms per coulomb (kg/C). It is most widely used in the electrod ...

and the

magnetic moment In electromagnetism, the magnetic moment is the magnetic strength and orientation of a magnet or other object that produces a magnetic field. Examples of objects that have magnetic moments include loops of electric current (such as electromagnets ...

Experimental setup

The single antiprotons are stored in an advanced

Penning trap A Penning trap is a device for the storage of charged particles using a homogeneous axial magnetic field and an inhomogeneous quadrupole electric field. This kind of trap is particularly well suited to precision measurements of properties of i ...

system, which has a multi-trap system at its core. It consists of a reservoir trap, a precision trap, an analysis trap and a cooling trap. The reservoir trap has the capability to store antiprotons for several years and allows BASE to operate experiments independent from accelerator cycles. The precision trap is for high precision frequency measurements, and the analysis trap has a strong magnetic field inhomogeneity superimposed, which is used for single particle

spin flip A black hole spin-flip occurs when the spin axis of a rotating black hole undergoes a sudden change in orientation due to absorption of a second (smaller) black hole. Spin-flips are believed to be a consequence of galaxy mergers, when two sup ...

spectroscopy Spectroscopy is the field of study that measures and interprets the electromagnetic spectra that result from the interaction between electromagnetic radiation and matter as a function of the wavelength or frequency of the radiation. Matter ...

. By measuring the

rate as a function of the frequency of an externally applied magnetic-drive, a resonance curve is obtained. Together with a measurement of the

cyclotron frequency Cyclotron resonance describes the interaction of external forces with charged particles experiencing a magnetic field, thus already moving on a circular path. It is named after the cyclotron, a cyclic particle accelerator that utilizes an oscillati ...

, the magnetic moment is extracted.

BASE physics

The BASE collaboration developed techniques to observe the first spin flips of a single trapped proton and applied the double-trap technique to measure the magnetic moment of the proton with a fractional precision of three parts in a billion, later improved to a precision of 300 parts in a trillion, being the most precise measurement of this fundamental property of the proton. With the invention of a two particle/three trap technique BASE measured the antiproton magnetic moment with a fractional accuracy of 1.5 parts in a billion, which improved the previous most precise proton/antiproton comparison in that sector by more than a factor of 3000. This measurement constitutes one of the most stringent tests of CPT invariance with baryons to date, and sets the most stringent limits on antimatter/dark matter interaction to date. Inspired by this work BASE has also used Penning trap detectors as axion haloscopes, and derived stringent narrow-band laboratory limits on the conversion of axions to photons. In 2022 BASE measured that the charge-to-mass ratios of protons and antiprotons are equal within a precision of 16 parts per trillion. This measurement constitutes the most precise test of CPT invariance in the baryon sector and sets the first differential constraints on the clock weak equivalence principle using baryonic antimatter.

BASE collaboration

The BASE collaboration comprises the following institutions:

References

{{Reflist

External Links

Record fo
BASE Experiment
on

INSPIRE-HEP INSPIRE-HEP is an open access digital library for the field of high energy physics (HEP). It is the successor of the Stanford Physics Information Retrieval System (SPIRES) database, the main literature database for high energy physics since the 1970 ...

Particle experiments CERN experiments

Experimental setup

BASE physics

BASE collaboration

See also

References

External Links