We present measurements of the first six hadronic mass moments in
semileptonic $B \rightarrow X_c \ell \nu $ decays. The hadronic mass moments,
together with other observables of inclusive $B$ ...decays, can be used to
determine the CKM matrix element $|{V_{cb}}|$ and mass of the $b$-quark $m_b$
in the context of Heavy Quark Expansions of QCD. The Belle~II data recorded at
the $\Upsilon (4S)$ resonance in 2019 and 2020 (March-July), corresponding to
an integrated luminosity of $34.6\;\mathrm{fb}^{-1}$, is used for this
measurement. The decay $\Upsilon (4S) \rightarrow B \overline{B}$ is
reconstructed by applying the hadronic tagging algorithm provided by the Full
Event Interpretation to fully reconstruct one $B$ meson. The second $B$ meson
is reconstructed inclusively by selecting a high-momentum lepton. The $X_c$
system is identified by the remaining reconstructed tracks and clusters in the
electromagnetic calorimeter. We report preliminary results for the hadronic
mass moments $\langle M_X^n \rangle $ with $n=1,\dots,6$, measured as a
function of a lower cut on the lepton momentum in the signal $B$ rest frame.
A case study on climate models intercomparison data analysis addressing several classes of multi-model experiments is being implemented in the context of the EU H2020 INDIGO-DataCloud project. Such ...experiments require the availability of large amount of data (multi-terabyte order) related to the output of several climate models simulations as well as the exploitation of scientific data management tools for large-scale data analytics. More specifically, the paper discusses in detail a use case on precipitation trend analysis in terms of requirements, architectural design solution, and infrastructural implementation. The experiment has been tested and validated on CMIP5 datasets, in the context of a large scale distributed testbed across EU and US involving three ESGF sites (LLNL, ORNL, and CMCC) and one central orchestrator site (PSNC).
We present a first measurement of the $\bar{B^{0}} \rightarrow D^{*+}
\ell^{-} \nu_{\ell}$ branching fraction using fully reconstructed $B$ meson
decays employing the Full Event Interpretation ...algorithm. Collision events
corresponding to an integrated luminosity of \lumi are analyzed, which were
recorded by the Belle~II detector operated at the SuperKEKB accelerator
complex. We measure$\cal{B}(\bar{B^{0}} \rightarrow D^{*+} \ell^{-} \nu_{\ell})
=4.51 \pm 0.41_{stat}\pm0.27_{syst} \pm0.45_{\pi_s}$, with the first and second
error denoting the statistical and systematic uncertainty, respectively, and
the third dominant uncertainty is from the slow pion reconstruction efficiency.
We present the results of the re-discovery of the decay $B^0 \to \pi^- \ell^+
\nu_\ell$ in 34.6 fb$^{-1}$ of Belle II data using hadronic $B$-tagging via the
Full Event Interpretation algorithm. We ...observe 21 signal events on a
background of 155 in a fit to the distribution of the square of the missing
mass, $M_{\mathrm{miss}}^2$, with a significance of 5.69$\sigma$, and determine
a total branching fraction of (1.58 $\pm$ 0.43$_{\mathrm{stat}}$ $\pm$
0.07$_{\mathrm{sys}}$) $\times 10^{-4}$.
We report measurements of the $\bar{B}^0 \to D^{*+} \ell^{-} \bar{\nu}_l$ and
$B^- \to D^{0} \ell^{-} \bar{\nu}_l$ processes using 34.6 fb$^{-1}$ of
collision events recorded by the Belle II ...experiment at the SuperKEKB
asymmetric-energy $e^+ e^-$ collider. For the $B^-\to D^{0}\ell^-\bar\nu_\ell$
channel, we present first studies that isolate this decay from other
semileptonic processes and backgrounds. We report a measurement of the
$\bar{B}^0 \to D^{*+} \ell^{-} \bar{\nu}_l$ branching fraction and obtain
${\cal B}(\bar{B}^0 \to D^{*+} \ell^{-} \bar{\nu}_l) = \left(4.60 \pm
0.05_{\mathrm{stat}}\pm0.17_{\mathrm{syst}} \pm 0.45_{\pi_s}\right) \%$, in
agreement with the world average. Here, the uncertainties are statistical,
systematic, and related to slow pion reconstruction, respectively. The
systematic uncertainties are limited by the statistics of auxiliary
measurements and will improve in the future. We also report differential
branching fractions in five bins of the hadronic recoil parameter $w$ for
$\bar{B}^0 \to D^{*+} \ell^{-} \bar{\nu}_l$, unfolded to account for resolution
and efficiency effects.
Tag-side reconstruction is an important method for reconstructing $B$ meson
decays with missing energy. The Belle II tag-side reconstruction algorithm,
Full Event Interpretation, relies on a ...hierarchical reconstruction of $B$ meson
decays with multivariate classification employed at each stage of
reconstruction. Given the large numbers of classifiers employed and decay
chains reconstructed, the performance of the algorithm on data and simulation
differs significantly. Here, calibration factors are derived for hadronic
tag-side $B$ decays by measuring a signal side decay, $B \rightarrow X\ell
\nu$, in $34.6$ fb$^{-1}$ of Belle II data. For a very loose selection on the
tag-side $B$ multivariate classifier, the calibration factors are $0.65 \pm
0.02$ and $0.83 \pm 0.03$ for tag-side $B^{+}$ and $B^{0}$ mesons,
respectively.
The reconstruction of tau-pair production, $e^{+}e^{-} \to \tau^{+}\tau^{-}$,
from the subsequent 3-prong ($\tau^{+} \rightarrow \pi^{+} \pi^{-} \pi^{+}
\bar{\nu}_{\tau}$) and 1-prong ($\tau^{-} \to ...\ell^{-} \bar{\nu}_{\ell}
\nu_{\tau}$, $\tau^{-} \to h^{-} \nu_{\tau}$ or $\tau^{-} \to \pi^{-} \pi^0
\nu_{\tau}$) decays, is presented using 8.8 fb$^{-1}$ of $e^{+}e^{-}$ collision
data of Belle II at the center-of-mass energy $\sqrt{s} = m_{\Upsilon(4S)}$.
The pseudomass technique developed by the ARGUS experiment is used to measure
the $\tau$-lepton mass $m_{\tau}$ in the 3-prong $\tau^{+} \to \pi^{+} \pi^{-}
\pi^{+} \bar{\nu}_{\tau} $ decay, resulting in $m_{\tau} = 1777.28 \pm
0.75~{\rm (stat.)} \pm 0.33 ~{\rm (sys.)}~{\rm{MeV}/\rm{c}^2}$.
We utilize a sample of 34.6 fb$^{-1}$, collected by the Belle II experiment
at the SuperKEKB asymmetric energy $e^+e^-$ collider, to search for the $B^+
\to \phi K^+$, $B^+ \to \phi K^{*+}$, $B^0 \to ...\phi K^0_S$, and $B^0 \to \phi
K^{*0}$ decays. Charmless hadronic $B$ decays represent an important part of
the Belle II physics program, and are an ideal benchmark to test the detector
capabilities in terms of tracking efficiency, charged particle identification,
vertexing, and advanced analysis techniques. Each channel is observed with a
significance that exceeds 5 standard deviations, and we obtain measurements of
their branching ratios that are in good agreement with the world averages. For
the $B \to \phi K^*$ modes, we also perform a measurement of the longitudinal
polarization fraction $f_L$.
We report on the first calibration of the standard Belle II \(B\)-flavor tagger using the full data set collected at the \(\Upsilon(4{\rm S})\) resonance in 2019 with the Belle II detector at the ...SuperKEKB collider, corresponding to 8.7 fb\(^{-1}\) of integrated luminosity. The calibration is performed by reconstructing various hadronic charmed \(B\)-meson decays with flavor-specific final states. We use simulation to optimize our event selection criteria and to train the flavor tagging algorithm. We determine the tagging efficiency and the fraction of wrongly identified tag-side \(B\)~candidates from a measurement of the time-integrated \(B^0-\overline{B}^0\) mixing probability. The total effective efficiency is measured to be \(\varepsilon_{\rm eff} = \big(33.8 \pm 3.6(\text{stat}) \pm 1.6(\text{sys})\big)\%\), which is in good agreement with the predictions from simulation and comparable with the best one obtained by the Belle experiment. The results show a good understanding of the detector performance and offer a basis for future calibrations.
Phys. Rev. Lett. 125, 161806 (2020) We present a search for the direct production of a light pseudoscalar $a$
decaying into two photons with the Belle II detector at the SuperKEKB collider.
We search ...for the process ${e^+e^-\to\gamma a, a \to\gamma\gamma}$ in the mass
range ${0.2} \,< m_a < {9.7}\,{\text{GeV/$c$}^2}$ using data corresponding to
an integrated luminosity of $(445\pm 3)\,\text{pb}^{-1}$. Light pseudoscalars
interacting predominantly with standard model gauge bosons (so-called
axion-like particles or ALPs) are frequently postulated in extensions of the
standard model. We find no evidence for ALPs and set 95% confidence level upper
limits on the coupling strength $g_{a\gamma\gamma}$ of ALPs to photons at the
level of $10^{-3}\,{\text{GeV}^{-1}}$. The limits are the most restrictive to
date for $0.2\,<\,m_a\,<\,1\,{\text{GeV/$c$}^2}$.
