Evidence for B^{-}→D^{**0}τ^{-}ν_{τ}[over ¯] Decays

Area of Science:

• High Energy Physics
• Particle Physics
• Experimental Physics

Background:

• B-meson decays are crucial for testing the Standard Model of particle physics.
• Understanding rare B-meson decays can reveal new physics phenomena.
• Previous studies have focused on decays involving lighter leptons, leaving tauonic decays less explored.

Purpose of the Study:

• To search for and provide the first evidence of the B-meson decay B^{-}→D^{**0}τ^{-}ν[over ¯]_{τ}.
• To measure the branching fraction of this decay mode.
• To investigate the ratio of tauonic to muonic B-meson decays.

Main Methods:

• Analysis of proton-proton collision data collected by the LHCb experiment at 7, 8, and 13 TeV.
• Identification of D^{**0} mesons, which include D_{1}(2420)^{0}, D_{2}^{*}(2460)^{0}, and D_{1}^{'}(2400)^{0} states.
• Statistical analysis to establish the significance of the observed signal and measure branching fractions.

Main Results:

• First evidence for the decay B^{-}→D^{**0}τ^{-}ν[over ¯]_{τ} observed with a 3.5σ significance.
• Combined branching fraction B(B^{-}→D_{1,2}^{**0}τ^{-}ν[over ¯]_{τ})×B(D_{1,2}^{**0}→D^{*+}π^{-}) measured as [0.051±0.013(stat)±0.006(syst)±0.009(ext)]%.
• Ratio of tauonic to muonic decays R(D_{1,2}^{**0}) determined to be 0.13±0.03(stat)±0.01(syst)±0.02(ext).

Conclusions:

• The observation of B^{-}→D^{**0}τ^{-}ν[over ¯]_{τ} provides crucial experimental data for B-physics.
• The measured branching fraction and ratio R(D_{1,2}^{**0}) can be used to test theoretical models of New Physics.
• This result contributes to a more comprehensive understanding of semileptonic B-decays involving tau leptons.