Precise Measurement of the D

We report a measurement of the D^{0} and D^{+} lifetimes using D^{0}→K^{-}π^{+} and D^{+}→K^{-}π^{+}π^{+} decays reconstructed in e^{+}e^{-}→cc[over ¯] data recorded by the Belle II experiment at the SuperKEKB asymmetric-energy e^{+}e^{-} collider. The data, collected at center-of-mass energies at or near the ϒ(4S) resonance, correspond to an integrated luminosity of 72 fb^{-1}. The results, τ(D^{0})=410.5±1.1(stat)±0.8(syst) fs and τ(D^{+})=1030.4±4.7(stat)±3.1(syst) fs, are the most precise to date and are consistent with previous determinations.

Search for B

A search for the flavor-changing neutral-current decay B^{+}→K^{+}νν[over ¯] is performed at the Belle II experiment at the SuperKEKB asymmetric energy electron-positron collider. The data sample corresponds to an integrated luminosity of 63 fb^{-1} collected at the ϒ(4S) resonance and a sample of 9 fb^{-1} collected at an energy 60 MeV below the resonance. Because the measurable decay signature involves only a single charged kaon, a novel measurement approach is used that exploits not only the properties of the B^{+}→K^{+}νν[over ¯] decay, but also the inclusive properties of the other B meson in the ϒ(4S)→BB[over ¯] event, to suppress the background from other B 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^{+}→K^{+}νν[over ¯] of 4.1×10^{-5} is set at the 90% confidence level.

Search for Axionlike Particles Produced in e

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^{-}→γa, a→γγ in the mass range 0.2

Search for an Invisibly Decaying Z

Theories beyond the standard model often predict the existence of an additional neutral boson, the Z^{'}. Using data collected by the Belle II experiment during 2018 at the SuperKEKB collider, we perform the first searches for the invisible decay of a Z^{'} in the process e^{+}e^{-}→µ^{+}µ^{-}Z^{'} and of a lepton-flavor-violating Z^{'} in e^{+}e^{-}→e^{±}µ^{∓}Z^{'}. We do not find any excess of events and set 90% credibility level upper limits on the cross sections of these processes. We translate the former, in the framework of an L_{µ}-L_{τ} theory, into upper limits on the Z^{'} coupling constant at the level of 5×10^{-2}-1 for M_{Z^{'}}≤6 GeV/c^{2}.