A method to determine |V cb | at the weak scale in top decays at the LHC

• Published in: The journal of high energy physics Vol. 2019; no. 1; pp. 1 - 15
• Main Authors: Harrison, P F, Vladimirov, V E
• Format: Journal Article
• Language: English
• Published: Heidelberg Springer Nature B.V 01.01.2019; SpringerOpen
• Subjects: B physics; Branching fraction; Decay; Flavor physics; Hadron-Hadron scattering (experiments); High energy physics; Large Hadron Collider; Top physics
• ISSN: 1029-8479
• DOI: 10.1007/JHEP01(2019)191

Until now, the Cabibbo Kobayashi Maskawa matrix element, |Vcb|, has always been measured in B decays, i.e. at an energy scale qb∼mb2\[ {q}_b\sim \frac{m_b}{2} \], far below the weak scale. We consider here the possibility of measuring it close to the weak scale, at qW ∼ mW, in top decays at the Large Hadron Collider (LHC). Our proposed method would use data from the LHC experiments in hadronic top decays t→bW+→bb¯c\[ t\to b{W}^{+}\to b\overline{b}c \], tagged by the semileptonic decay of the associated top. We estimate the uncertainty of such a measurement, as a function of present and potential future experimental jet flavour-tagging performances, and conclude that first measurements using the data collected during 2016-2018 could yield a fractional error on |Vcb| of order 7% per experiment. We also give projected performances at higher luminosities, representative of those anticipated at LHC Run 3 and HL-LHC.