arXiv subjects

S. Bernet Andres

Publications and source records attributed to S. Bernet Andres.

188 records · Page 11Linked to original sources

arXiv2023

Study of charmonium decays to $K^0_S K π$ in the $B \to (K^0_S K π) K$ channels

A study of the $B^+\to K^0_SK^+K^-π^+$ and $B^+\to K^0_SK^+K^+π^-$ decays is performed using proton-proton collisions at center-of-mass energies of 7, 8 and 13 TeV at the LHCb experiment. The $K^0_SK π$ invariant mass spectra from both decay modes reveal a rich content of charmonium resonances. New precise measurements of the $η_c$ and $η_c(2S)$ resonance parameters are performed and branching fraction measurements are obtained for $B^+$ decays to $η_c$, $J/ψ$, $η_c(2S)$ and $χ_{c1}$ resonances. In particular, the first observation and branching fraction measurement of $B^+ \to χ_{c0} K^0 π^+$ is reported as well as first measurements of the $B^+\to K^0K^+K^-π^+$ and $B^+\to K^0K^+K^+π^-$ branching fractions. Dalitz plot analyses of $η_c \to K^0_SKπ$ and $η_c(2S) \to K^0_SKπ$ decays are performed. A new measurement of the amplitude and phase of the $K π$ $S$-wave as functions of the $K π$ mass is performed, together with measurements of the $K^*_0(1430)$, $K^*_0(1950)$ and $a_0(1700)$ parameters. Finally, the branching fractions of $χ_{c1}$ decays to $K^*$ resonances are also measured.

hep-ex↗

arXiv2023

Observation of a resonant structure near the $D_s^+ D_s^-$ threshold in the $B^+\to D_s^+ D_s^- K^+$ decay

An amplitude analysis of the $B^+\to D_s^+ D_s^- K^+$ decay is carried out to study for the first time its intermediate resonant contributions, using proton-proton collision data collected with the LHCb detector at centre-of-mass energies of 7, 8 and 13 TeV. A near-threshold peaking structure, referred to as $X(3960)$, is observed in the $D_s^+ D_s^-$ invariant-mass spectrum with significance greater than 12 standard deviations. The mass, width and the quantum numbers of the structure are measured to be $3956\pm5\pm10$ MeV, $43\pm13\pm8$ MeV and $J^{PC}=0^{++}$, respectively, where the first uncertainties are statistical and the second systematic. The properties of the new structure are consistent with recent theoretical predictions for a state composed of $c\bar{c}s\bar{s}$ quarks. Evidence for an additional structure is found around 4140 MeV in the $D_s^+ D_s^-$ invariant mass, which might be caused either by a new resonance with the $0^{++}$ assignment or by a $J/ψϕ\leftrightarrow D_s^+ D_s^-$ coupled-channel effect.

hep-ex↗

arXiv2023

Search for $D^{*}(2007)^0\toμ^+μ^-$ in $B^-\toπ^-μ^+μ^-$ decays

The very rare $D^{*}(2007)^0\toμ^+μ^-$ decay is searched for by analysing $B^-\toπ^-μ^+μ^-$ decays. The analysis uses a sample of beauty mesons produced in proton-proton collisions collected with the LHCb detector between 2011 and 2018, corresponding to an integrated luminosity of 9 fb$^{-1}$. The signal signature corresponds to simultaneous peaks in the $μ^+μ^-$ and $π^-μ^+μ^-$ invariant masses. No evidence for an excess of events over background is observed and an upper limit is set on the branching fraction of the decay at ${\cal B}(D^{*}(2007)^0\toμ^+μ^-) < 2.6\times 10^{-8}$ at $90\%$ confidence level. This is the first limit on the branching fraction of $D^{*}(2007)^0\toμ^+μ^-$ decays and the most stringent limit on $D^{*}(2007)^0$ decays to leptonic final states. The analysis is the first search for a rare charm-meson decay exploiting production via beauty decays.

hep-ex↗

arXiv2023

Amplitude analysis of $B^0 \rightarrow \overline{D}^0 D_s^+ π^-$ and $B^+ \rightarrow D^- D_s^+ π^+$ decays

Resonant contributions in $B^0 \rightarrow \overline{D}^0 D^+_sπ^-$ and $B^+\rightarrow D^- D^+_sπ^+$ decays are determined with an amplitude analysis, which is performed both separately and simultaneously, where in the latter case isospin symmetry between the decays is assumed. The analysis is based on data collected by the LHCb detector in proton-proton collisions at center-of-mass energies of 7, 8 and 13 $\rm{TeV}$. The full data sample corresponds to an integrated luminosity of 9 $\rm fb^{-1}$. A doubly charged spin-0 open-charm tetraquark candidate together with a neutral partner, both with masses near $2.9\,\rm{GeV}$, are observed in the $D_sπ$ decay channel.

hep-ex↗

arXiv2023

First observation of a doubly charged tetraquark and its neutral partner

A combined amplitude analysis is performed for the decays $B^0 \rightarrow \overline{D}^0 D^+_sπ^-$ and $B^+\rightarrow D^- D^+_sπ^+$, which are related by isospin symmetry. The analysis is based on data collected by the LHCb detector in proton-proton collisions at center-of-mass energies of 7, 8 and 13$\,\rm{TeV}$. The full data sample corresponds to an integrated luminosity of 9$\,\rm{fb^{-1}}$. Two new resonant states with masses of $2.908\pm0.011\pm0.020\,\rm{GeV}$ and widths of $0.136\pm0.023\pm0.011\,\rm{GeV}$ are observed, which decay to $D^+_sπ^+$ and $D^+_sπ^-$ respectively. The former state indicates the first observation of a doubly charged open-charm tetraquark state with minimal quark content $[c\bar{s}u\bar{d}]$, and the latter state is a neutral tetraquark composed of $[c\bar{s}\bar{u}d]$ quarks. Both states are found to have spin-parity $0^+$, and their resonant parameters are consistent with each other, which suggests that they belong to an isospin triplet.

hep-ex↗

arXiv2023

Measurement of the ratio of branching fractions $\mathcal{B}(B_c^+ \to B_s^0 π^+)/\mathcal{B}(B_c^+ \to J/ψπ^+)$

The ratio of branching fractions of $B_c^+ \to B_s^0 π^+$ and $B_c^+ \to J/ψπ^+$ decays is measured with proton-proton collision data of a centre-of-mass energy of $13\text{TeV}$. The data were collected with the LHCb experiment during 2016--2018, corresponding to an integrated luminosity of $5.4 \text{fb}^{-1}$. The $B_s^0$ mesons are reconstructed via the decays $B_s^0 \to J/ψϕ$ and $B_s^0 \to D_s^- π^+$. The ratio of branching fractions is measured to be $\mathcal{B}(B_c^+ \to B_s^0 π^+)/\mathcal{B}(B_c^+ \to J/ψπ^+) = 91 \pm 10 \pm 8 \pm 3$ where the first uncertainty is statistical, the second is systematic and the third is due to the knowledge of the branching fractions of the intermediate state decays.

hep-ex↗

arXiv2023

First observation and branching fraction measurement of the $Λ_b^0\to D_s^- p$ decay

The first observation of the $Λ_b^0\to D_s^- p$ decay is presented using proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of ${\sqrt{s}=13 \,\textrm{TeV}}$, corresponding to a total integrated luminosity of $6\,\textrm{fb}^{-1}$. Using the $Λ_b^0\toΛ_c^+π^-$ decay as the normalisation mode, the branching fraction of the $Λ_b^0\to D_s^- p$ decay is measured to be ${\mathcal{B}(Λ_b^0\to D_s^- p)=(12.6 \pm 0.5 \pm 0.3 \pm 1.2 )\times 10^{-6}}$, where the first uncertainty is statistical, the second systematic and the third due to uncertainties in the branching fractions of the $Λ_b^0\toΛ_c^+π^-$, $D_s^- \to K^-K^+π^-$ and $Λ_c^+\to p K^- π^+$ decays.

hep-ex↗

arXiv2023

Observation of the $B^0_s\!\to D^{+}D^{-}$ decay

The first observation of the $B^0_s\!\to D^{*+}D^{*-}$ decay and the measurement of its branching ratio relative to the $B^0\!\to D^{*+}D^{*-}$ decay are presented. The data sample used corresponds to an integrated luminosity of $9\,\text{fb}^{-1}$ of proton-proton collisions recorded by the LHCb experiment at centre-of-mass energies of 7, 8 and $13\,\text{TeV}$ between 2011 and 2018. The decay is observed with more than $10$ standard deviations and the time-integrated ratio of branching fractions is determined to be \begin{align*} \frac{\mathcal{B}(B^0_s\!\to D^{*+}D^{*-})}{\mathcal{B}(B^0\!\to D^{*+}D^{*-})} = 0.269 \pm 0.032 \pm 0.011 \pm 0.008\, , \end{align*} where the first uncertainty is statistical, the second systematic and the third due to the uncertainty of the fragmentation fraction ratio $f_s/f_d$. The $B^0_s\!\to D^{*+}D^{*-}$ branching fraction is calculated to be \begin{align*} \mathcal{B}(B^0_s\!\to D^{*+}D^{*-}) = (2.15 \pm 0.26 \pm 0.09 \pm 0.06 \pm 0.16)\times 10^{-4} \,, \end{align*} where the fourth uncertainty is due to the $B^0\!\to D^{*+}D^{*-}$branching fraction. These results are calculated using the average $B^0_s$ meson lifetime in simulation. Correction factors are reported for scenarios where either a purely heavy or a purely light $B^0_s$ eigenstate is considered.

hep-ex↗