Related papers: First data at Belle II and Dark Sector physics

The Belle experiment has given a substantial contribution in the field of heavy quarkonia. Several new states were announced by Belle for the first time, in both charmonium and bottomonium spectrum, or the confirmation from Belle…

The silicon vertex detector of the Belle experiment has been built to provide the vertex information of $B$ meson decays at the KEKB accelerator. Performance during the initial data taking period and a brief description of the upgrade plan…

We report preliminary measurements of the first (mean) and second moment (variance) of the inclusive photon energy spectrum in $B\to X_s\gamma$ decays, for threshold values of the photon energy in the range 1.8--2.3 GeV as measured in the…

Analyses of $B$ meson decays to charmless hadronic final states are an important part of the Belle II program. They are sensitive to effects from non-standard model physics and provide experimentally precise constraints on the weak…

We report on the first measurements of branching fractions, CP-violating charge asymmetries, and longitudinal polarization fractions in charmless $B$ decays at the Belle II experiment. We use a sample of electron-positron collisions…

The Belle II experiment, operating at the asymmetric SuperKEKB $e^+e^-$ collider, is preparing an upgrade of its vertex detector to cope with an increased luminosity of $6 \times 10^{35}$ cm$^{-2}$s$^{-1}$. The upgraded vertex detector…

We investigate a new production mechanism of axion-like particle (ALP) from $B$ meson annihilation decays and its observation potential at the Belle and Belle II experiments. This mechanism allows for the production of ALP from $B$ meson…

The data sample recorded with the Belle detector at the KEKB B factory (Tsukuba, Japan) operating at the Y(5S) energy provides interesting and new results about the Bs0 mesons and the Y(5S) resonance. Recent analyses, based on data samples…

This proceeding summarizes the recent measurements of semileptonic $b\to u$ decays from the Belle experiment. These analyses use the full data set collected at the $\Upsilon(4S)$ resonance at KEKB accelerator complex with a center-of-mass…

The Belle II detector at the SuperKEKB accelerator observed the first collisions in April this year. Until mid-summer, the first commissioning run uses a reduced version of the full vertex detector. Nevertheless, this phase is an excellent…

This contribution illustrates a new search for the flavor-changing neutral-current decay ${B^+ \to K^+ \nu \bar \nu}$ performed by the Belle II experiment at the SuperKEKB asymmetric-energy electron-positron collider. In this study, a…

We present a measurement of the $\tau$-lepton mass using a sample of about 175 million $e^+e^- \to \tau^+\tau^-$ events collected with the Belle II detector at the SuperKEKB $e^+e^-$ collider at a center-of-mass energy of…

We present measurements of the branching fractions of eight $\overline B{}^0\to D^{(*)+} K^- K^{(*)0}_{(S)}$, $B^{-}\to D^{(*)0} K^- K^{(*)0}_{(S)}$ decay channels. The results are based on data from SuperKEKB electron-positron collisions…

The Belle II experiment at the SuperKEKB collider is preparing for an upgrade after 2027-2028 to handle higher luminosity and increased background rates. A Radio Frequency System-on-Chip (RFSoC) has been identified as a potential candidate…

Recently, the Belle II collaboration announced the first measurement of $\mathcal B(B^+\to K^+\nu\bar\nu)$, which is found to be about $2.7\sigma$ higher than the SM prediction. We decipher the data with two new physics scenarios: the…

We report on preliminary measurements of branching fractions, charge-parity-violating asymmetries, and longitudinal polarization fractions in charmless bottom-meson decays from the Belle~II experiment. We use samples of electron-positron…

Belle II measurement of the branching fraction for $B^{+} \to K^{+} \nu \bar{\nu}$ shows a $2.7\sigma$ excess over the Standard Model prediction and motivates new-physics explanations such as axion-like particles, Higgs-like scalars, or…

We report on the first measurement of the direct $CP$-violating asymmetry ($\mathcal{A}$) in the charmless decay $B^0 \to K^0\pi^0$ at Belle II and an updated measurement of its branching fraction ($\mathcal{B}$). We use a sample of…

The Belle II detector operating at the future upgrade to the KEKB accelerator will perform high-statistics precision investigations into the flavor sector of the Standard Model. As charged hadron identification is a vital element of the…

This paper describes the track-finding algorithm that is used for event reconstruction in the Belle II experiment operating at the SuperKEKB B-factory in Tsukuba, Japan. The algorithm is designed to balance the requirements of a high…