Observation of new excited ${B} ^0_{s} $ B s 0 states
The European Physical Journal C(2021)
摘要
A structure is observed in the
${B} ^{\pm }{K} ^{\mp }$
mass spectrum in a sample of proton–proton collisions at centre-of-mass energies of 7, 8, and 13 TeV, collected with the LHCb detector and corresponding to a total integrated luminosity of 9
$\,\text {fb} ^{-1}$
. The structure is interpreted as the result of overlapping excited
${B} ^0_{s} $
states. With high significance, a two-peak hypothesis provides a better description of the data than a single resonance. Under this hypothesis the masses and widths of the two states, assuming they decay directly to
${B} ^{\pm }{K} ^{\mp }$
, are determined to be
$\begin{aligned} m_1&= 6063.5 \pm 1.2 \text { (stat)} \pm 0.8\text { (syst)}\,\text {Me}\text {V}, \\ \Gamma _1&= 26 \pm 4 \text { (stat)} \pm 4\text { (syst)}\,\text {Me}\text {V}, \\ m_2&= 6114 \pm 3 \text { (stat)} \pm 5\text { (syst)}\,\text {Me}\text {V}, \\ \Gamma _2&= 66 \pm 18 \text { (stat)} \pm 21\text { (syst)}\,\text {Me}\text {V}. \end{aligned}$
Alternative values assuming a decay through
${B} ^{*\pm }{K} ^{\mp }$
, with a missing photon from the
$B^{*\pm } \rightarrow B^{\pm }\gamma $
decay, which are shifted by approximately 45
$\,\text {Me}$
V, are also determined. The possibility of a single state decaying in both channels is also considered. The ratio of the total production cross-section times branching fraction of the new states relative to the previously observed
$B_{s2}^{*0}$
state is determined to be
$0.87 \pm 0.15 \text { (stat)} \pm 0.19 \text { (syst)}$
.
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