Constraints on New Physics in Electron <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>g</mml:mi><mml:mo>−</mml:mo><mml:mn>2</mml:mn></mml:math> from a Search for Invisible Decays of a Scalar, Pseudoscalar, Vector, and Axial Vector
Yu. M. Andreev, D. Banerjee, J. Bernhard, V.E. Burtsev, А. Г. Чумаков, D. Cooke, P. Crivelli, E. Depero, A. Dermenev, S.V. Donskov, R. R. Dusaev, T. Enik, N. Charitonidis, A. A. Feshchenko, V. Frolov, A. Gardikiotis, S. Gerassimov, S. Gninenko, M. Hösgen, Vassili Kachanov, A. Karneyeu, G. D. Kekelidze, B. Ketzer, D. Kirpichnikov, M. Kirsanov, V. N. Kolosov, I. Konorov, S. G. Kovalenko, V. A. Kramarenko, L. Kravchuk, Nikolai Krasnikov, S. Kuleshov, Valery E. Lyubovitskij, V. Lysan, V. Matveev, Yu.V. Mikhailov, L. Molina Bueno, D. V. Peshekhonov, V. A. Polyakov, B. Radics, R. A. Rojas, A. Rubbia, V. D. Samoylenko, H. Sieber, Dmitry G. Shchukin, V. O. Tikhomirov, I. Tlisova, A. Toropin, A. Yu. Trifonov, B. I. Vasilishin, P. Volkov, V. Yu. Volkov
Abstract
We performed a search for a new generic $X$ boson, which could be a scalar ($S$), pseudoscalar ($P$), vector ($V$), or an axial vector ($A$) particle produced in the 100 GeV electron scattering off nuclei, ${e}^{\ensuremath{-}}Z\ensuremath{\rightarrow}{e}^{\ensuremath{-}}ZX$, followed by its invisible decay in the NA64 experiment at CERN. No evidence for such a process was found in the full NA64 dataset of $2.84\ifmmode\times\else\texttimes\fi{}{10}^{11}$ electrons on target. We place new bounds on the $S$, $P$, $V$, $A$ coupling strengths to electrons, and set constraints on their contributions to the electron anomalous magnetic moment ${a}_{e}$, $|\mathrm{\ensuremath{\Delta}}{a}_{X}|\ensuremath{\lesssim}{10}^{\ensuremath{-}15}--{10}^{\ensuremath{-}13}$ for the $X$ mass region $1\text{ }\text{ }\mathrm{MeV}\ensuremath{\lesssim}{m}_{X}\ensuremath{\lesssim}1\text{ }\text{ }\mathrm{GeV}$. These results are an order of magnitude more sensitive compared to the current accuracy on ${a}_{e}$ from the electron $g\ensuremath{-}2$ experiments and recent high-precision determination of the fine structure constant.