First observation of the charmless beauty decay \(\lambda\frac{0}{b}\)→pKη'

Williams, Timothy (2018). First observation of the charmless beauty decay \(\lambda\frac{0}{b}\)→pKη'. University of Birmingham. Ph.D.

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Abstract

A search is performed for the decay \(\lambda\frac{0}{b}\)→pKη' using pp collision data collected with the LHCb detector at centre-of-mass energies of \(\sqrt{s}\) = 7TeV and \(\sqrt{s}\) = 8TeV, corresponding to an integrated luminosity of 3 fb\(^-\)\(^1\). The search is performed in two decay channels; the η' is reconstructed through the decays η'→\(\pi^+\pi^-\gamma\) and η'→\(\pi^+\pi^-\eta\). In the η'→\(\pi^+\pi^-\gamma\) decay channel 117 ± 15(stat.) ± 10(sys.) signal events are observed and 45 ± 8(stat.) ± 2(sys.) signal events are observed in the η'→\(\pi^+\pi^-\eta\) decay channel. The combined statistical significance of these signals is 12.0σ, therefore this is the first observation of the decay \(\lambda\frac{0}{b}\)→pKη' . The branching fraction of the decay \(\lambda\frac{0}{b}\)→pKη' is measured relative to the decay B\(^+\)→K\(^+\)η'.
The ratio of branching fractions is measured to be

\(\frac{\beta(\lambda\frac{0}{b}→pKη')}{\beta(B^+→K^+η'}\)= 0.120 ± 0.013(stat.) ± 0.013(sys.).

Using the world average value for the branching fraction of the decay B\(^+\)→K\(^+\)η', the branching fraction of \(\lambda\frac{0}{b}\)→pKη' is measured to be,
\(\beta\)\((\lambda\frac{0}{b}→pKη')\) = 8.48 ± 0.88(stat.) ± 0.97(sys.) x 10\(^-\)\(^6\)
.
This is the first observation of a b-baryon decaying to an η.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):