Publication

Search for the Lepton Number Violating Process j/ψ = k Plus k Plus e- e- Plus c.c.*

2026

Abstract

Based on (10087 +/- 44) x 10(6) J/psi events collected with the BESIII detector, we search for the lepton number violating decay J/psi = K+ K+ e(-) e(-) + c.c. for the first time. The upper limit on the branching fraction of this decay is set to at the 90% confidence level with a frequentist method. This is the first search for J/psi decays with a lepton number change by two, offering valuable insights into the underlying physical processes.

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2026

Abstract

Official source

Related concepts (32)

Lepton

In particle physics, a lepton is an elementary particle of half-integer spin (spin ) that does not undergo strong interactions. Two main classes of leptons exist: charged leptons (also known as the electron-like leptons or muons), and neutral leptons (better known as neutrinos). Charged leptons can combine with other particles to form various composite particles such as atoms and positronium, while neutrinos rarely interact with anything, and are consequently rarely observed. The best known of all leptons is the electron.

Baryon number

In particle physics, the baryon number is a strictly conserved additive quantum number of a system. It is defined as where n_{\rm q} is the number of quarks, and n_{\rm \overline q} is the number of antiquarks. Baryons (three quarks) have a baryon number of +1, mesons (one quark, one antiquark) have a baryon number of 0, and antibaryons (three antiquarks) have a baryon number of −1. Exotic hadrons like pentaquarks (four quarks, one antiquark) and tetraquarks (two quarks, two antiquarks) are also classified as baryons and mesons depending on their baryon number.

Lepton number

In particle physics, lepton number (historically also called lepton charge) is a conserved quantum number representing the difference between the number of leptons and the number of antileptons in an elementary particle reaction. Lepton number is an additive quantum number, so its sum is preserved in interactions (as opposed to multiplicative quantum numbers such as parity, where the product is preserved instead). The lepton number is defined by where is the number of leptons and is the number of antileptons.

Search for the Lepton Number Violating Process <i>j</i>/ψ = <i>k</i> Plus <i>k</i> Plus <i>e</i>- <i>e</i>- Plus <i>c</i>.<i>c</i>.*

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