First Observation of the Doubly Charmed Baryon Decay Ξ_{cc}^{++}→Ξ_{c}^{+}π^{+}

Area of Science:

• Particle Physics
• High Energy Physics
• Hadron Spectroscopy

Background:

• Doubly charmed baryons are exotic hadrons containing two charm quarks.
• Understanding their decays provides insights into the strong nuclear force and quantum chromodynamics.
• Previous observations hinted at the existence of the Ξ_{cc}^{++} baryon.

Purpose of the Study:

• To report the first observation of the decay Ξ_{cc}^{++}→Ξ_{c}^{+}π^{+}.
• To measure the mass of the Ξ_{cc}^{++} baryon.
• To determine the ratio of branching fractions for different decay modes of the Ξ_{cc}^{++} baryon.

Main Methods:

• Analysis of proton-proton collision data collected by the LHCb experiment at a center-of-mass energy of 13 TeV.
• Statistical analysis to establish the significance of the observed decay signal.
• Reconstruction of decay products to identify the Ξ_{cc}^{++} and Ξ_{c}^{+} baryons.

Main Results:

• Observation of the decay Ξ_{cc}^{++}→Ξ_{c}^{+}π^{+} with a statistical significance of 5.9σ.
• Measurement of the Ξ_{cc}^{++} mass as 3620.6±1.5(stat)±0.4(syst)±0.3(Ξ_{c}^{+}) MeV/c².
• Determination of the ratio of branching fractions [B(Ξ_{cc}^{++}→Ξ_{c}^{+}π^{+})×B(Ξ_{c}^{+}→pK^{-}π^{+})]/[B(Ξ_{cc}^{++}→Λ_{c}^{+}K^{-}π^{+}π^{+})×B(Λ_{c}^{+}→pK^{-}π^{+})] = 0.035±0.009(stat)±0.003(syst).

Conclusions:

• The first observation of the Ξ_{cc}^{++}→Ξ_{c}^{+}π^{+} decay provides strong evidence for the existence of the doubly charmed baryon Ξ_{cc}^{++}.
• The measured mass is consistent with previous results, further solidifying the Ξ_{cc}^{++} baryon's properties.
• The branching fraction ratio offers valuable data for theoretical models of baryon decays.