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Bertella, C.

Publications and source records attributed to Bertella, C..

77 records · Page 5
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DOE OSTI2021

Search for the doubly heavy baryons $ {{{{\varOmega}_{bc}^{0}}}} $ and $ {{{{\varXi}_{bc}^{0}}}} $ decaying to $ {{{{\varLambda}^+_c}}} {{{{\pi}^-}}} $ and $ {{{{\varXi}^+_c}}} {{{{\pi}^-}}} $ *

The first search for the doubly heavy $ {{{{\varOmega}_{bc}^{0}}}} $ baryon and a search for the $ {{{{\varXi}_{bc}^{0}}}} $ baryon are performed using $ pp $ collision data collected via the $ {\rm{LHCb}} $ experiment from 2016 to 2018 at a centre-of-mass energy of $ 13 \;{\rm{TeV}} $, corresponding to an integrated luminosity of 5.2 $ \;{\rm{f}}{{\rm{b}}^{ - 1}} $. The baryons are reconstructed via their decays to $ {{{{\varLambda}^+_c}}} {{{{\pi}^-}}} $ and $ {{{{\varXi}^+_c}}} {{{{\pi}^-}}} $. No significant excess is found for invariant masses between 6700 and 7300 $ \;{\rm{MeV}}/{c^2} $, in a rapidity range from 2.0 to 4.5 and a transverse momentum range from 2 to 20 $ \;{\rm{MeV}}/{c} $. Upper limits are set on the ratio of the $ {{{{\varOmega}_{bc}^{0}}}} $ and $ {{{{\varXi}_{bc}^{0}}}} $ production cross-section times the branching fraction to $ {{{{\varLambda}^+_c}}}{{{{\pi}^-}}} $ ( $ {{{{\varXi}^+_c}}}{{{{\pi}^-}}} $) relative to that of the $ {{{{\varLambda}^0_b}}} $ ( $ {{{{\varXi}_{b}^{0}}}} $) baryon, for different lifetime hypotheses, at 95% confidence level. The upper limits range from $ 0.5\times10^{-4} $ to $ 2.5\times10^{-4} $ for the $ {{{{{{{{\varOmega}_{bc}^{0}}}}{{\rightarrow }}{{{{\varLambda}^+_c}}}{{{{\pi}^-}}}}}}} $ ( $ {{{{{{{{\varXi}_{bc}^{0}}}}{{\rightarrow }}{{{{\varLambda}^+_c}}}{{{{\pi}^-}}}}}}} $) decay, and from $ 1.4\times10^{-3} $ to $ 6.9\times10^{-3} $ for the $ {{{{{{{{\varOmega}_{bc}^{0}}}}{{\rightarrow }}{{{{\varXi}^+_c}}}{{{{\pi}^-}}}}}}} $ ( $ {{{{{{{{\varXi}_{bc}^{0}}}}{{\rightarrow }}{{{{\varXi}^+_c}}}{{{{\pi}^-}}}}}}} $) decay, depending on the considered mass and lifetime of the $ {{{{\varOmega}_{bc}^{0}}}} $ ( $ {{{{\varXi}_{bc}^{0}}}} $) baryon.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Observation of new excited ${B} ^0_{s}$ states

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 $0.87 \pm 0.15 \text { (stat)} \pm 0.19 \text { (syst)}$.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗