Space-time segmentation method for study of the vertical structure and evolution of solar supergranulation from data provided by local helioseismology

Solar supergranulation remains a mystery in spite of decades of intensive studies. Most of the papers about supergranulation deal with its surface properties. Local helioseismology provides an opportunity to look below the surface and see the vertical structure of this convective structure. We present a concept of a (3+1)-D segmentation algorithm capable of recognising individual supergranules in a sequence of helioseismic 3-D flow maps. As an example, we applied this method to the state-of-the-art data and derived descriptive statistical properties of segmented supergranules -- typical size of 20--30 Mm, characteristic lifetime of 18.7 hours, and estimated depth of 15--20 Mm. We present preliminary results obtained on the topic of the three-dimensional structure and evolution of supergranulation. The method has a great potential in analysing the better data expected from the helioseismic inversions, which are being developed.Comment: 6 pages, 4 figures, accepted in New Astronom

B-flavor tagging at Belle II

We report on new flavor tagging algorithms developed to determine the quark-flavor content of bottom ( ) mesons at Belle II. The algorithms provide essential inputs for measurements of quark-flavor mixing and charge-parity violation. We validate and evaluate the performance of the algorithms using hadronic decays with flavor-specific final states reconstructed in a data set corresponding to an integrated luminosity of 62.8 fb−1 , collected at the resonance with the Belle II detector at the SuperKEKB collider. We measure the total effective tagging efficiency to be εeff=(30.0±1.2(stat)±0.4(syst))% for a category-based algorithm and εeff=(28.8±1.2(stat)±0.4(syst))% for a deep-learning-based algorithm

Unbinned Deep Learning Jet Substructure Measurement in High Q2Q^2 ep collisions at HERA

The radiation pattern within high energy quark- and gluon-initiated jets (jet substructure) is used extensively as a precision probe of the strong force as well as an environment for optimizing event generators with numerous applications in high energy particle and nuclear physics. Looking at electron-proton collisions is of particular interest as many of the complications present at hadron colliders are absent. A detailed study of modern jet substructure observables, jet angularities, in electron-proton collisions is presented using data recorded using the H1 detector at HERA. The measurement is unbinned and multi-dimensional, using machine learning to correct for detector effects. All of the available reconstructed object information of the respective jets is interpreted by a graph neural network, achieving superior precision on a selected set of jet angularities. Training these networks was enabled by the use of a large number of GPUs in the Perlmutter supercomputer at Berkeley Lab. The particle jets are reconstructed in the laboratory frame, using the $k_{\mathrm{T}}$ jet clustering algorithm. Results are reported at high transverse momentum transfer $Q^2>150$ GeV${}^2$, and inelasticity $0.2 < y < 0.7$. The analysis is also performed in sub-regions of $Q^2$, thus probing scale dependencies of the substructure variables. The data are compared with a variety of predictions and point towards possible improvements of such models.Comment: 33 pages, 10 figures, 8 table

Measurement of the Λc+\Lambda_c^+ lifetime

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.Comment: Accepted for publication in PR

Precise measurement of the Ds+D^+_s lifetime at Belle II

We measure the lifetime of the $D_s^+$ meson using a data sample of 207 fb$^{-1}$ collected by the Belle II experiment running at the SuperKEKB asymmetric-energy $e^+ e^-$ collider. The lifetime is determined by fitting the decay-time distribution of a sample of $116\times 10^3$ $D_s^+\rightarrow\phi\pi^+$ decays. Our result is \tau^{}_{D^+_s} = (498.7\pm 1.7\,^{+1.1}_{-0.8}) fs, where the first uncertainty is statistical and the second is systematic. This result is significantly more precise than previous measurements.Comment: 7 pages, 4 figures, to be submitted to Physical Review Letter

Search for an invisible Z′Z^\prime in a final state with two muons and missing energy at Belle II

The $L_{\mu}-L_{\tau}$ extension of the standard model predicts the existence of a lepton-flavor-universality-violating $Z^{\prime}$ boson that couples only to the heavier lepton families. We search for such a $Z^\prime$ through its invisible decay in the process $e^+ e^- \to \mu^+ \mu^- Z^{\prime}$. We use a sample of electron-positron collisions at a center-of-mass energy of 10.58GeV collected by the Belle II experiment in 2019-2020, corresponding to an integrated luminosity of 79.7fb$^{-1}$. We find no excess over the expected standard-model background. We set 90$\%$-confidence-level upper limits on the cross section for this process as well as on the coupling of the model, which ranges from $3 \times 10^{-3}$ at low $Z^{\prime}$ masses to 1 at $Z^{\prime}$ masses of 8$GeV/c^{2}$

Measurement of branching fractions and direct CPCP asymmetries for B→KπB \to K\pi and B→ππB\to\pi\pi decays at Belle II

We report measurements of the branching fractions and direct $\it{CP}$ asymmetries of the decays $B^0 \to K^+ \pi^-$, $B^+ \to K^+ \pi^0$, $B^+ \to K^0 \pi^+$, and $B^0 \to K^0 \pi^0$, and use these for testing the standard model through an isospin-based sum rule. In addition, we measure the branching fraction and direct $\it{CP}$ asymmetry of the decay $B^+ \to \pi^+\pi^0$ and the branching fraction of the decay $B^0 \to \pi^+\pi^-$. The data are collected with the Belle II detector from $e^+e^-$ collisions at the $\Upsilon(4S)$ resonance produced by the SuperKEKB asymmetric-energy collider and contain $387\times 10^6$ bottom-antibottom meson pairs. Signal yields are determined in two-dimensional fits to background-discriminating variables, and range from 500 to 3900 decays, depending on the channel. We obtain $-0.03 \pm 0.13 \pm 0.04$ for the sum rule, in agreement with the standard model expectation of zero and with a precision comparable to the best existing determinations

Measurement of C ⁣PC\!P asymmetries and branching-fraction ratios for B±→DK±B^\pm \to DK^\pm and Dπ±D\pi^\pm with D→KS0K±π∓D\to K^0_{\rm S} K^\pm\pi^\mp using Belle and Belle II data

We measure $C\!P$ asymmetries and branching-fraction ratios for $B^\pm \to DK^\pm$ and $D\pi^\pm$ decays with $D\to K^0_{\rm S} K^\pm\pi^\mp$, where $D$ is a superposition of $D^0$ and $\bar{D}^0$. We use the full data set of the Belle experiment, containing $772\times 10^6~B\bar{B}$ pairs, and data from the Belle~II experiment, containing $387\times 10^6~B\bar{B}$ pairs, both collected in electron-positron collisions at the $\Upsilon(4S)$ resonance. Our results provide model-independent information on the unitarity triangle angle $\phi_3$.Comment: 26 pages, 8 figure