Related papers: Heavy QCD Axion at Belle II: Displaced and Prompt …
The HyperCP experiment reported the observation of three events for the $\Sigma^+ \rightarrow p \mu^+\mu^-$ decay. The dimuon masses of the observed events are clustered within the detector resolution of 1 MeV/$c^2$. These decays might be…
Belle II is an experiment designed to study billions of $\tau$-lepton, $b$- and $c$-quark decays observed with low background in asymmetric-energy electron-positron collisions at the SuperKEKB $B$-factory. In March 2019, the newly completed…
Using data recorded with the Belle detector, we observe a new excited hyperon, an $\Omega^{*-}$ candidate decaying into $\Xi^0K^-$ and $\Xi^-K^0_S$ with a mass of $2012.4\pm0.7\ {\rm (stat)\pm\ 0.6\ (\rm syst)}\ {\rm MeV}/c^2$ and a width…
We search for lepton-flavor-violating $\tau^-\to e^-\alpha$ and $\tau^-\to\mu^-\alpha$ decays, where $\alpha$ is an invisible spin-0 boson. The search uses electron-positron collisions at $10.58$ GeV center-of-mass energy with an integrated…
We report results of a search for tau lepton decays strongly suppressed in the Standard Model based on the world-largest data sample accumulated with the Belle detector at the KEKB asymmetric-energy e+e- collider. The decays include: lepton…
The decay constant of the QCD axion is required by observation to be small compared to the Planck scale. In theories of "natural inflation," and certain proposed anthropic solutions of the cosmological constant problem, it would be…
Two-body decays like $K \to \pi a$ rank among the most constraining collider probes for new, low-mass, feebly interacting pseudoscalar particles $a$. We explore an alternative class of kaon decay modes, specifically three-body decays to…
The Belle II experiment's ability to identify particles critically affects the sensitivity of its measurements. We describe Belle II's algorithms for identifying charged particles and evaluate their performance in separating pions, kaons,…
Considerable theoretical efforts have gone into expanding the reach of the QCD axion beyond its canonical mass--decay-constant relation. The $Z_\mathcal{N}$ QCD axion model reduces the QCD axion mass naturally, by invoking a discrete…
We perform an angular analysis of the $B\to K^* e^+ e^-$ decay for the dielectron mass squared, $q^2$, range of $0.0008$ to $1.1200 ~\text{GeV}^2 /c^4$ using the full Belle data set in the $K^{*0} \to K^+ \pi^-$ and $K^{*+} \to K_S^0 \pi^+$…
We consider the class of effective supergravity theories from the weakly coupled heterotic string in which local supersymmetry is broken by gaugino condensation in a hidden sector, with dilaton stabilization achieved through corrections to…
The decays and mixing of $K$ mesons are remarkably sensitive to the weak interactions of quarks and leptons at high energies. They provide important tests of the standard model at both first and second order in the Fermi constant $G_F$ and…
Heavy vector-like quarks of charge $-1/3$, $B$, have been searched for at the LHC through the decays $B\rightarrow bZ,\, bh,\,tW$. In models where the $B$ quark also carries charge under a new gauge group, new decay channels may dominate.…
We present a QCD axion model where the couplings of the axion to nucleons, electrons, and muons are naturally suppressed because of the appropriate choice of the Peccei-Quinn charges of the Standard Model fermions. We reexamine…
We propose a search for $B$ meson decays to a baryon plus missing energy at the Belle II experiment to probe supersymmetry with a GeV-scale lightest neutralino ${\tilde{\chi}_1^0}$ and $R$-parity violation (RPV). We perform analytic…
We present a connection between two known solutions to the strong-CP problem: the standard introduction of axions and the extra-dimensional one, relying on topological arguments. Using an equivalent lower-dimensional set-up with a warped…
We present a lattice-QCD calculation of the masses and decay constants of the positive-parity heavy-strange mesons $D^*_{s0}$, $D_{s1}$, $B^*_{s0}$, and $B_{s1}$. The calculations are performed with domain-wall fermions for the light and…
Semileptonic decays of $B$ mesons that proceed via $b\rightarrow u$ and $b\rightarrow c$ transitions, as well as rare leptonic $B$ decays, are fertile grounds for probing new physics beyond the Standard Model. The Belle II experiment…
The QCD axion serves as a well-motivated dark matter candidate and the misalignment mechanism is known to reproduce the observed abundance with a decay constant $f_a \simeq \mathcal{O}(10^{12})$ GeV for a misalignment angle $\theta_{\rm…
In the past twenty years, many new hadrons that are difficult to be explained within the conventional quark model have been discovered in the quarkonium region, which are called exotic hadrons. Belle II experiment, as the next-generation…