First Observation of the Doubly Charmed Baryon Decay Ξcc++→Ξc+π+<

Abstract

The doubly charmed baryon decay Ξ þþ cc → Ξ þ c π þ is observed for the first time, with a statistical significance of 5.9σ, confirming a recent observation of the baryon in the Λ þ c K − π þ π þ final state. The data sample used corresponds to an integrated luminosity of 1.7 fb −1 , collected by the LHCb experiment in pp collisions at a center-of-mass energy of 13 TeV. The Ξ þþ cc mass is measured to be 3620.6 AE 1.5ðstatÞ AE 0.4ðsystÞ AE 0.3ðΞ þ c Þ MeV=c 2 and is consistent with the previous result. The ratio of branching fractions between the decay modes is measured to be ½BðΞ þþ cc → Ξ þ c π þ Þ × BðΞ þ c → pK − π þ Þ=½BðΞ þþ cc → Λ þ c K − π þ π þ Þ × BðΛ þ c → pK − π þ Þ ¼ 0.035 AE 0.009ðstatÞ AE 0.003ðsystÞ.

Two-body weak decays of doubly charmed baryons

“…As the first two-body weak decay Ξ + c π + of the doubly charmed baryon Ξ ++ cc was reported by the LHCb with the result [2]…”

“…The doubly charmed baryon state Ξ ++ cc was first discovered by the LHCb in the weak decay mode Λ + c K − π + π + [1] and subsequently confirmed in another mode Ξ + c π + [2]. Its lifetime was also measured by the LHCb to be [3] τ Ξ ++ cc = 0.256 +0.024 −0.022 (stat.)…”

“…It is known that the estimate of the S-wave amplitudes in the pole model is a difficult and nontrivial task as it involves the matrix elements and strong coupling constants of 1/2 − baryon resonances which we know very little [22]. 2 Nevertheless, if the emitted pseudoscalar meson is soft, then the intermediate excited baryons can be summed up, leading to a commutator term…”

A comprehensive analysis of weak transition form factors for doubly heavy baryons in the light front approach

“…• A reasonable modification with momentum-space wave function Ψ SSz in the case of an axial-vector diquark involved is performed in this work in Eqs. (2) and (3). While, in Refs.…”

“…[2]. This discovery is subsequently confirmed in 2018 in the Ξ ++ cc → Ξ + c π + decay [3], and meanwhile triggered a series of experimental investigations [4][5][6][7]. Now studies of doubly-heavy baryons now open a window to study the hadron spectroscopy and strong interactions in a baryonic system in the presence of two heavy constituent quarks.…”