Precision measurement of the mass difference between light nuclei and anti-nuclei

Adam, J. and Adamova, D. and Aggarwal, M. M. and Rinella, G. A. and Agnello, M. and Barnaföldi, Gergely Gábor and Bencédi, Gyula and Berényi, Dániel and Boldizsár, László and Dénes, Ervin and Hamar, Gergő and Kiss, Gábor and Varga-Kőfaragó, Mónika and Lévai, Péter and Oláh, László and Pochybova, Sona (2015) Precision measurement of the mass difference between light nuclei and anti-nuclei. NATURE PHYSICS, 11 (10). pp. 811-814. ISSN 1745-2473

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Abstract

The measurement of the mass differences for systems bound by the strong force has reached a very high precision with protons and anti-protons. The extension of such measurement from (anti-)baryons to (anti-)nuclei allows one to probe any difference in the interactions between nucleons and anti- nucleons encoded in the (anti-)nuclei masses. This force is a remnant of the underlying strong in- teraction among quarks and gluons and can be described by effective theories, but cannot yet be directly derived from quantum chromodynamics. Here we report a measurement of the difference between the ratios of the mass and charge of deuterons (d) and anti-deuterons (d), and 3He and 3He nuclei carried out with the ALICE (A Large Ion Collider Experiment) detector in Pb-Pb colli- sions at a centre-of-mass energy per nucleon pair of 2.76 TeV. Our direct measurement of the mass- over-charge differences confirm CPT invariance to an unprecedented precision in the sector of light nuclei. This fundamental symmetry of nature, which exchanges particles with anti-particles, implies that all physics laws are the same under the simultaneous reversal of charge(s) (charge conjugation C), reflection of spatial coordinates (parity transformation P) and time inversion (T).

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