The Full Event Interpretation Keck, T.; Abudinén, F.; Bernlochner, Florian U. ...
Computing and software for big science,
12/2019, Letnik:
3, Številka:
1
Journal Article
Odprti dostop
The full event interpretation is presented: a new exclusive tagging algorithm used by the high-energy physics experiment Belle II. The experimental setup of Belle II allows the precise measurement of ...otherwise inaccessible
B
meson decay modes. The Full Event Interpretation algorithm enables many of these measurements. The algorithm relies on machine learning to automatically identify plausible
B
meson decay chains based on the data recorded by the detector. Compared to similar algorithms employed by previous experiments, the Full Event Interpretation provides a greater efficiency, yielding a larger effective sample size usable in the measurement.
We study the processes e^{+}e^{-}→ωχ_{bJ}(1P) (J=0, 1, or 2) using samples at center-of-mass energies sqrts=10.701, 10.745, and 10.805 GeV, corresponding to 1.6, 9.8, and 4.7 fb^{-1} of integrated ...luminosity, respectively. These data were collected with the Belle II detector during special operations of the SuperKEKB collider above the ϒ(4S) resonance. We report the first observation of ωχ_{bJ}(1P) signals at sqrts=10.745 GeV. By combining Belle II data with Belle results at sqrts=10.867 GeV, we find energy dependencies of the Born cross sections for e^{+}e^{-}→ωχ_{b1,b2}(1P) to be consistent with the shape of the ϒ(10753) state. These data indicate that the internal structures of the ϒ(10753) and ϒ(10860) states may differ. Including data at sqrts=10.653 GeV, we also search for the bottomonium equivalent of the X(3872) state decaying into ωϒ(1S). No significant signal is observed for masses between 10.45 and 10.65 GeV/c^{2}.
Measurement of the Λ_{c}^{+} Lifetime Ahmed, H; Ahn, J K; Aloisio, A ...
Physical review letters,
2023-Feb-17, 20230217, Letnik:
130, Številka:
7
Journal Article
Recenzirano
An absolute measurement of the Λ_{c}^{+} lifetime is reported using Λ_{c}^{+}→pK^{-}π^{+} decays in events reconstructed from data collected by the Belle II experiment at the SuperKEKB ...asymmetric-energy electron-positron collider. The total integrated luminosity of the data sample, which was collected at center-of-mass energies at or near the ϒ(4S) resonance, is 207.2 fb^{-1}. The result, τ(Λ_{c}^{+})=203.20±0.89±0.77 fs, where the first uncertainty is statistical and the second systematic, is the most precise measurement to date and is consistent with previous determinations.
Physical Review Letters 130, 091902 (2023) We study the processes $e^+e^-\to\omega\chi_{bJ}(1P)$ ($J$ = 0, 1, or 2)
using samples at center-of-mass energies $\sqrt{s}$ = 10.701, 10.745, and
10.805 ...GeV, corresponding to 1.6, 9.8, and 4.7 fb$^{-1}$ of integrated
luminosity, respectively. These data were collected with the Belle II detector
during special operations of the SuperKEKB collider above the $\Upsilon(4S)$
resonance. We report the first observation of $\omega\chi_{bJ}(1P)$ signals at
$\sqrt{s}$ = 10.745 GeV. By combining Belle II data with Belle results at
$\sqrt{s}$ = 10.867 GeV, we find energy dependencies of the Born cross sections
for $e^+e^-\to \omega\chi_{b1,b2}(1P)$ to be consistent with the shape of the
$\Upsilon(10753)$ state. These data indicate that the internal structures of
the $\Upsilon(10753)$ and $\Upsilon(10860)$ states may differ. Including data
at $\sqrt{s}$ = 10.653 GeV, we also search for the bottomonium equivalent of
the $X(3872)$ state decaying into $\omega\Upsilon(1S)$. No significant signal
is observed for masses between 10.45 and 10.65 GeV/$c^2$.
Phys. Rev. D 107, L031103 (2023) We report on a measurement of the $\Omega_c^0$ lifetime using $\Omega_c^0 \to
\Omega^-\pi^+$ decays reconstructed in $e^+e^-\to c\bar{c}$ data collected by
the Belle ...II experiment and corresponding to $207~{\rm fb^{-1}}$ of integrated
luminosity. The result, $\rm\tau(\Omega_c^0)=243\pm48( stat)\pm11(syst)~fs$,
agrees with recent measurements indicating that the $\Omega_c^0$ is not the
shortest-lived weakly decaying charmed baryon.
Phys. Rev. Lett. 130, 071804 (2023) The dark photon $A^\prime$ and the dark Higgs boson $h^\prime$ are
hypothetical particles predicted in many dark sector models. We search for the
simultaneous ...production of $A^\prime$ and $h^\prime$ in the dark Higgsstrahlung
process $e^{+}e^{-}\rightarrow A^\prime \, h^\prime$ with $A^\prime \rightarrow
\mu^+\mu^-$ and $ h^\prime$ invisible in electron-positron collisions at a
center-of-mass energy of 10.58 GeV collected by the Belle II experiment in
2019. With an integrated luminosity of 8.34 fb$^{-1}$, we observe no evidence
for signal. We obtain exclusion limits at 90% Bayesian credibility in the range
of 1.7--5.0 fb on the cross section and in the range of $1.7
\times10^{-8}$--$200 \times10^{-8}$ on the effective coupling $\varepsilon^2
\times \alpha_D$ for the $A^\prime$ mass in the range of 4.0 GeV/$c^2$ $<
M_{A^\prime}< 9.7$ GeV/$c^2$ and for the $h^\prime$ mass $M_{h^\prime} <
M_{A^\prime}$, where $\varepsilon$ is the mixing strength between the standard
model and the dark photon and $\alpha_D$ is the coupling of the dark photon to
the dark Higgs boson. Our limits are the first in this mass range.
Phys. Rev. Lett. 130, 071802 (2023) An absolute measurement of the $\Lambda^{+}_c$ lifetime is reported using
$\Lambda_c^+\rightarrow pK^-\pi^+$ decays in events reconstructed from data
collected by ...the Belle II experiment at the SuperKEKB asymmetric-energy
electron-positron collider. The total integrated luminosity of the data sample,
which was collected at center-of-mass energies at or near the $\Upsilon(4S)$
resonance, is $207.2~\mbox{fb}^{-1}$. The result, $\tau(\Lambda^{+}_c) = 203.20
\pm 0.89 \,\mathrm{(stat)} \pm 0.77 \,\mathrm{(syst)}$ fs, is the most precise
measurement to date and is consistent with previous determinations.
Phys. Rev. Lett. 127, 181802 (2021) A search for the flavor-changing neutral-current decay $B^{+}\to
K^{+}\nu\bar{\nu}$ is performed at the Belle II experiment at the SuperKEKB
asymmetric energy ...electron-positron collider. The results are based on a data
sample corresponding to an integrated luminosity of $63\,\mbox{fb}^{-1}$
collected at the $\Upsilon{(4S)}$ resonance and a sample of $9\,\mbox{fb}^{-1}$
collected at an energy $60\mathrm{\,Me\kern -0.1em V}$ below the resonance. A
novel measurement method is employed, which exploits topological properties of
the $B^{+}\to K^{+}\nu\bar{\nu}$ decay that differ from both generic
bottom-meson decays and light-quark pair production. This inclusive tagging
approach offers a higher signal efficiency compared to previous searches. No
significant signal is observed. An upper limit on the branching fraction of
$B^{+}\to K^{+}\nu\bar{\nu}$ of $4.1 \times 10^{-5}$ is set at the 90%
confidence level.
The dark photon \(A^\prime\) and the dark Higgs boson \(h^\prime\) are hypothetical particles predicted in many dark sector models. We search for the simultaneous production of \(A^\prime\) and ...\(h^\prime\) in the dark Higgsstrahlung process \(e^{+}e^{-}\rightarrow A^\prime \, h^\prime\) with \(A^\prime \rightarrow \mu^+\mu^-\) and \( h^\prime\) invisible in electron-positron collisions at a center-of-mass energy of 10.58 GeV collected by the Belle II experiment in 2019. With an integrated luminosity of 8.34 fb\(^{-1}\), we observe no evidence for signal. We obtain exclusion limits at 90% Bayesian credibility in the range of 1.7--5.0 fb on the cross section and in the range of \(1.7 \times10^{-8}\)--\(200 \times10^{-8}\) on the effective coupling \(\varepsilon^2 \times \alpha_D\) for the \(A^\prime\) mass in the range of 4.0 GeV/\(c^2\) \(< M_{A^\prime}< 9.7\) GeV/\(c^2\) and for the \(h^\prime\) mass \(M_{h^\prime} < M_{A^\prime}\), where \(\varepsilon\) is the mixing strength between the standard model and the dark photon and \(\alpha_D\) is the coupling of the dark photon to the dark Higgs boson. Our limits are the first in this mass range.
We report on a measurement of the \(\Omega_c^0\) lifetime using \(\Omega_c^0 \to \Omega^-\pi^+\) decays reconstructed in \(e^+e^-\to c\bar{c}\) data collected by the Belle II experiment and ...corresponding to \(207~{\rm fb^{-1}}\) of integrated luminosity. The result, \(\rm\tau(\Omega_c^0)=243\pm48( stat)\pm11(syst)~fs\), agrees with recent measurements indicating that the \(\Omega_c^0\) is not the shortest-lived weakly decaying charmed baryon.
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