Study of the rare decay J/ψ → μ+μ−μ+μ−

R. Aaij, A. S. W. Abdelmotteleb, Carlos Abellán Beteta, F. Abudinén, T. Ackernley, A. A. Adefisoye, B. Adeva, M. Adinolfi, P. Adlarson, C. Agapopoulou

Abstract

A bstract The rare electromagnetic J/ψ → μ + μ − μ + μ − decay is observed with a significance greatly exceeding the discovery threshold, using proton-proton collision data collected by the LHCb experiment during 2016–2018 at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5 . 4 fb − 1 . The rate of this decay is measured relative to that of the J/ψ → μ + μ − mode. Using the QED model for the four-muon decay in the efficiency estimation, its branching fraction is determined to be $$ \mathcal{B}\left(J/\psi \to {\mu}^{+}{\mu}^{-}{\mu}^{+}{\mu}^{-}\right)=\left(1.13\pm 0.10\pm 0.05\pm 0.01\right)\times {10}^{-6}, $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>B</mml:mi> <mml:mfenced> <mml:mrow> <mml:mi>J</mml:mi> <mml:mo>/</mml:mo> <mml:mi>ψ</mml:mi> <mml:mo>→</mml:mo> <mml:msup> <mml:mi>μ</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msup> <mml:mi>μ</mml:mi> <mml:mo>−</mml:mo> </mml:msup> <mml:msup> <mml:mi>μ</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msup> <mml:mi>μ</mml:mi> <mml:mo>−</mml:mo> </mml:msup> </mml:mrow> </mml:mfenced> <mml:mo>=</mml:mo> <mml:mfenced> <mml:mrow> <mml:mn>1.13</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.10</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.05</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.01</mml:mn> </mml:mrow> </mml:mfenced> <mml:mo>×</mml:mo> <mml:msup> <mml:mn>10</mml:mn> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>6</mml:mn> </mml:mrow> </mml:msup> <mml:mo>,</mml:mo> </mml:math> where the uncertainties are statistical, systematic and due to the uncertainty on the branching fraction of the J/ψ → μ + μ − decay.

Locations

• Journal of High Energy Physics - View - PDF