New experiments show that antimatter has the same gravitational pull as ordinary matter

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The Standard Model of particle physics, while incredibly successful, is clearly imperfect. One of the unanswered questions is the astonishing imbalance between matter and antimatter in the universe, which requires further experiments to compare the basic properties of matter/antimatter conjugate with high precision. A new experiment by cernion-centre-of-Cernation 's Baryonic AntibarIan Symmetry Experiment (BASE) directly studies the fundamental properties of protons and antiprotons.

According to the Standard Model, matter and antimatter particles can be different, for example, they are converted into other particles in different ways, but most of their properties, including their mass, should be the same.

Discovering any slight difference between the masses of protons and antiprotons, or between their charge and mass, would break the basic symmetry of the Standard Model, the CPT symmetry, and point to new physical phenomena outside that model.

This discrepancy could also explain why the universe is made up almost entirely of ordinary matter, although an equal amount of antimatter should have been produced in the Big Bang.

The difference between ordinary matter and antimatter particles consistent with the Standard Model is orders of magnitude smaller, enabling an explanation of the observed cosmic imbalance.

To measure protons and antiprotons, physicists at the BASE collaboration confine antiprotons and negatively charged hydrogen ions (representatives of negatively charged protons) to a state-of-the-art particle trap called Penning. (Translator's note: Ordinary hydrogen ions lose their extranuclear electrons, so only positively charged protons remain)

In this device, particles move in a periodic trajectory close to the cyclotron frequency, which is proportional to the magnetic field strength of the trap and the particle's charge-to-mass ratio.

Alternating antiprotons and negatively charged hydrogen ions were injected into the well, under the same conditions, the researchers measured the gyratory frequencies of the two particles and compared their charge-to-mass ratios. Four measurements were taken between December 2017 and May 2019, and these measurements yielded more than 24,000 swing frequency comparisons for 260 seconds each.

Through these comparisons, coupled with the difference between protons and negatively charged hydrogen ions, the BASE team found that the charge-to-mass ratio of protons and antiprotons was within 16 parts per trillion.

Dr. Stefan Ulmer, a spokesman for the BASE partnership, said: "This result is four times more accurate than the best results before, using the most accurate method of measuring the properties of antiprotons today."

"To achieve this precision, we made a considerable upgrade to the experiment and measured it when the antimatter plant was closed, using our antiproton library, which can store antiprotons for several years."

In addition to comparing protons and antiprotons with unprecedented precision, the scientists used their measurements to impose strict limits on models other than the Standard Model that violateSP symmetry and tested a fundamental law of physics known as the principle of weak equivalence.

According to this principle, in the same gravitational field, different objects have the same acceleration without friction.

Since the BASE experiment is placed on the Earth's surface, its proton and antiproton gyrotron frequency measurements are performed in the earth's surface gravitational field.

Any difference between the gravitational action of protons and antiprotons can lead to a difference between the frequency of proton and antiproton rotation.

When sampling the gravitational field that changes as the Earth orbits the Sun, the BASE team found no such difference and set the maximum value of this difference measurement to one-third.

"This limit is comparable to the initial precise targets of experiments designed to place antihydrogen in Earth's gravitational field," Dr. Ulmer said.

"BASE does not directly place antimatter in Earth's gravitational field, but our measurements of the effect of gravity on baryonic antimatter particles are conceptually very similar, suggesting that there is no anomalous interaction between antimatter and gravity at the level of uncertainty reached."

The team's findings were published in the journal Nature.

Original: http://www.sci-news.com/physics/antiproton-proton-charge-mass-ratio-10437.html