0000000000140193

AUTHOR

M. Watanabe

showing 4 related works from this author

Search for an Invisibly Decaying Z′ Boson at Belle II in e+e−→μ+μ−(e±μ∓) Plus Missing Energy Final States

2020

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±μZ′. 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 Lμ-Lτ theory, into upper limits on the Z′ coupling constant at the level of 5×10-2-1 for MZ′≤6 GeV/c2.

PhysicsCoupling constantParticle physicsMissing energyPhysics beyond the Standard ModelGeneral Physics and Astronomy01 natural scienceslaw.inventionlaw0103 physical sciencesHigh Energy Physics::Experiment010306 general physicsColliderBosonPhysical Review Letters
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Search for Axionlike Particles Produced in e+e− Collisions at Belle II

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-→γa, a→γγ in the mass range 0.2<ma<9.7 GeV/c2 using data corresponding to an integrated luminosity of (445±3) pb-1. Light pseudoscalars interacting predominantly with standard model gauge bosons (so-called axionlike 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 gaγγ of ALPs to photons at the level of 10-3 GeV-1. The limits are the most restrictive to date for 0.2<ma<1 GeV/c2.

PhysicsRange (particle radiation)Particle physicsGauge bosonLuminosity (scattering theory)Photon010308 nuclear & particles physicsGeneral Physics and Astronomy01 natural scienceslaw.inventionStandard ModelPseudoscalarDirect productionlaw0103 physical sciencesHigh Energy Physics::Experiment010306 general physicsColliderPhysical Review Letters
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The Belle II vertex detector integration

2019

Belle II DEPFET, PXD, and SVD Collaborations: et al.

Nuclear and High Energy PhysicsPhysics::Instrumentation and DetectorsSilicon sensorPhase (waves)Computer Science::Computational Geometry7. Clean energy01 natural scienceslaw.inventionNuclear physicsBelle II; Data acquisition; Pixel detector; Silicon sensor; Strip detector; Vertex detector; Nuclear and High Energy Physics; InstrumentationData acquisitionlaw0103 physical sciencesVertex detectorBelle IIStrip detectorColliderInstrumentationNuclear and High Energy PhysicPhysicsInterconnectionPixel010308 nuclear & particles physicsDetectorBelle II; data acquisition; pixel detector; silicon sensor; strip detector; vertex detectorData acquisitionPixel detectorUpgradeHigh Energy Physics::ExperimentFocus (optics)Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
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Precise Measurement of the D0 and D+ Lifetimes at Belle II

2021

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.

PhysicsParticle physics010308 nuclear & particles physicslaw0103 physical sciencesGeneral Physics and AstronomyResonance010306 general physicsCollider01 natural scienceslaw.inventionLuminosityPhysical Review Letters
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