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Publication

Observation of a Resonance in B+ -> K+mu(+)mu(-) Decays at Low Recoil

Abstract

A broad peaking structure is observed in the dimuon spectrum of B+ -> K+mu(+)mu(-) decays in the kinematic region where the kaon has a low recoil against the dimuon system. The structure is consistent with interference between the B+ -> K+mu(+)mu(-) decay and a resonance and has a statistical significance exceeding six standard deviations. The mean and width of the resonance are measured to be 4191(-8)(+9) MeV/c(2) and 65(-16)(+22) MeV/c(2), respectively, where the uncertainties include statistical and systematic contributions. These measurements are compatible with the properties of the psi(4160) meson. First observations of both the decay B+ -> psi(4160)K+ and the subsequent decay psi(4160) -> mu(+)mu(-) are reported. The resonant decay and the interference contribution make up 20% of the yield for dimuon masses above 3770 MeV/c(2). This contribution is larger than theoretical estimates.

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Abstract

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Related concepts (32)

Beta decay

In nuclear physics, beta decay (β-decay) is a type of radioactive decay in which an atomic nucleus emits a beta particle (fast energetic electron or positron), transforming into an isobar of that nuclide. For example, beta decay of a neutron transforms it into a proton by the emission of an electron accompanied by an antineutrino; or, conversely a proton is converted into a neutron by the emission of a positron with a neutrino in so-called positron emission.

J/psi meson

The _J/psi (J/psi) meson ˈdʒeɪ_ˈsaɪ_ˈmiːzɒn is a subatomic particle, a flavor-neutral meson consisting of a charm quark and a charm antiquark. Mesons formed by a bound state of a charm quark and a charm anti-quark are generally known as "charmonium" or psions. The _J/Psi is the most common form of charmonium, due to its spin of 1 and its low rest mass. The _J/Psi has a rest mass of 3.0969GeV/c2, just above that of the _charmed eta (2.9836GeV/c2), and a mean lifetime of 7.2e-21s.

Radioactive decay

Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is considered radioactive. Three of the most common types of decay are alpha, beta, and gamma decay, all of which involve emitting particles. The weak force is the mechanism that is responsible for beta decay, while the other two are governed by the electromagnetism and nuclear force.

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