First Measurement of R(X_{τ/ℓ}) as an Inclusive Test of the b→cτν Anomaly.

We measure the tau-to-light-lepton ratio of inclusive B-meson branching fractions R(X_{τ/ℓ})≡B(B→Xτν)/B(B→Xℓν), where ℓ indicates an electron or muon, and thereby test the universality of charged-current weak interactions. We select events that have one fully reconstructed B meson and a charged lepton candidate from 189 fb^{-1} of electron-positron collision data collected with the Belle II detector. We find R(X_{τ/ℓ})=0.228±0.016(stat)±0.036(syst), in agreement with standard-model expectations. This is the first direct measurement of R(X_{τ/ℓ}).

Search for a τ

We report the first search for a nonstandard-model resonance decaying into τ pairs in e^{+}e^{-}→µ^{+}µ^{-}τ^{+}τ^{-} events in the 3.6-10 GeV/c^{2} mass range. We use a 62.8 fb^{-1} sample of e^{+}e^{-} collisions collected at a center-of-mass energy of 10.58 GeV by the Belle II experiment at the SuperKEKB collider. The analysis probes three different models predicting a spin-1 particle coupling only to the heavier lepton families, a Higgs-like spin-0 particle that couples preferentially to charged leptons (leptophilic scalar), and an axionlike particle, respectively. We observe no evidence for a signal and set exclusion limits at 90% confidence level on the product of cross section and branching fraction into τ pairs, ranging from 0.7 to 24 fb, and on the couplings of these processes. We obtain world-leading constraints on the couplings for the leptophilic scalar model for masses above 6.5 GeV/c^{2} and for the axionlike particle model over the entire mass range.

Measurement of CP Violation in B

We report a measurement of the CP-violating parameters C and S in B^{0}→K_{S}^{0}π^{0} decays at Belle II using a sample of 387×10^{6} BB[over ¯] events recorded in e^{+}e^{-} collisions at a center-of-mass energy corresponding to the ϒ(4S) resonance. These parameters are determined by fitting the proper decay-time distribution of a sample of 415 signal events. We obtain C=-0.04_{-0.15}^{+0.14}±0.05 and S=0.75_{-0.23}^{+0.20}±0.04, where the first uncertainties are statistical and the second are systematic.

Search for Lepton-Flavor-Violating τ Decays to a Lepton and an Invisible Boson at Belle II.

We search for lepton-flavor-violating τ^{-}→e^{-}α and τ^{-}→µ^{-}α decays, where α is an invisible spin-0 boson. The search uses electron-positron collisions at 10.58 GeV center-of-mass energy with an integrated luminosity of 62.8 fb^{-1}, produced by the SuperKEKB collider and collected with the Belle II detector. We search for an excess in the lepton-energy spectrum of the known τ^{-}→e^{-}ν[over ¯]_{e}ν_{τ} and τ^{-}→µ^{-}ν[over ¯]_{µ}ν_{τ} decays. We report 95% confidence-level upper limits on the branching-fraction ratio B(τ^{-}→e^{-}α)/B(τ^{-}→e^{-}ν[over ¯]_{e}ν_{τ}) in the range (1.1-9.7)×10^{-3} and on B(τ^{-}→µ^{-}α)/B(τ^{-}→µ^{-}ν[over ¯]_{µ}ν_{τ}) in the range (0.7-12.2)×10^{-3} for α masses between 0 and 1.6 GeV/c^{2}. These results provide the most stringent bounds on invisible boson production from τ decays.

Search for an Invisible Z

The L_{µ}-L_{τ} extension of the standard model predicts the existence of a lepton-flavor-universality-violating Z^{'} boson that couples only to the heavier lepton families. We search for such a Z^{'} through its invisible decay in the process e^{+}e^{-}→µ^{+}µ^{-}Z^{'}. We use a sample of electron-positron collisions at a center-of-mass energy of 10.58 GeV collected by the Belle II experiment in 2019-2020, corresponding to an integrated luminosity of 79.7 fb^{-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 3×10^{-3} at low Z^{'} masses to 1 at Z^{'} masses of 8 GeV/c^{2}.

Tests of Light-Lepton Universality in Angular Asymmetries of B

We present the first comprehensive tests of the universality of the light leptons in the angular distributions of semileptonic B^{0}-meson decays to charged spin-1 charmed mesons. We measure five angular-asymmetry observables as functions of the decay recoil that are sensitive to lepton-universality-violating contributions. We use events where one neutral B is fully reconstructed in ϒ(4S)→BB[over ¯] decays in data corresponding to 189 fb^{-1} integrated luminosity from electron-positron collisions collected with the Belle II detector. We find no significant deviation from the standard model expectations.

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.

Measurements of the Branching Fractions of the Semileptonic Decays Ξ_{c}

Using data samples of 89.5 and 711 fb^{-1} recorded at energies of sqrt[s]=10.52 and 10.58 GeV, respectively, with the Belle detector at the KEKB e^{+}e^{-} collider, we report measurements of branching fractions of semileptonic decays Ξ_{c}^{0}→Ξ^{-}ℓ^{+}ν_{ℓ} (ℓ=e or µ) and the CP-asymmetry parameter of Ξ_{c}^{0}→Ξ^{-}π^{+} decay. The branching fractions are measured to be B(Ξ_{c}^{0}→Ξ^{-}e^{+}ν_{e})=(1.31±0.04±0.07±0.38)% and B(Ξ_{c}^{0}→Ξ^{-}µ^{+}ν_{µ})=(1.27±0.06±0.10±0.37)%, and the decay parameter α_{Ξπ} is measured to be 0.63±0.03±0.01 with much improved precision compared with the current world average. The corresponding ratio B(Ξ_{c}^{0}→Ξ^{-}e^{+}ν_{e})/B(Ξ_{c}^{0}→Ξ^{-}µ^{+}ν_{µ}) is 1.03±0.05±0.07, which is consistent with the expectation of lepton flavor universality. The first measured asymmetry parameter A_{CP}=(α_{Ξ^{-}π^{+}}+α_{Ξ[over ¯]^{+}π^{-}})/(α_{Ξ^{-}π^{+}}-α_{Ξ[over ¯]^{+}π^{-}})=0.024±0.052±0.014 is found to be consistent with zero. The first and the second uncertainties above are statistical and systematic, respectively, while the third ones arise due to the uncertainty of the Ξ_{c}^{0}→Ξ^{-}π^{+} branching fraction.

Test of Lepton-Flavor Universality in B→K

We present a measurement of R_{K^{*}}, the branching fraction ratio B(B→K^{*}µ^{+}µ^{-})/B(B→K^{*}e^{+}e^{-}), for both charged and neutral B mesons. The ratio for the charged case R_{K^{*+}} is the first measurement ever performed. In addition, we report absolute branching fractions for the individual modes in bins of the squared dilepton invariant mass q^{2}. The analysis is based on a data sample of 711 fb^{-1}, containing 772×10^{6} BB[over ¯] events, recorded at the ϒ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e^{+}e^{-} collider. The obtained results are consistent with standard model expectations.

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.

Delayed neutrophil apoptosis in granulomatosis with polyangiitis: dysregulation of neutrophil gene signature and circulating apoptosis-related proteins.

Objectives: Neutrophil apoptosis is mandatory for resolving inflammation and is regulated by expression of pro- and anti-apoptotic genes. We studied neutrophils isolated from patients with granulomatosis with polyangiitis (GPA) to investigate apoptosis alterations and to identify transcriptional and circulating factors affecting this process.Method: We enrolled 36 patients (18 in active stage, 18 in remission) and 18 healthy controls. Circulating levels of tumour necrosis factor-α (TNF-α), granulocyte-macrophage colony-stimulating factor (GM-CSF), macrophage migration inhibitory factor, plasminogen activator inhibitor-1, interferon-γ, vascular cell adhesion molecule-1, intercellular adhesion molecule-1, platelet endothelial cell adhesion molecule-1, soluble Fas (sFas), sFas ligand, survivin, and pentraxin-3 (PTX3) were evaluated by enzyme-linked immunosorbent assay/Luminex; circulating apoptotic neutrophils by flow cytometry; and apoptosis-related gene transcripts by real-time polymerase chain reaction.Results: Patients had decreased fractions of circulating apoptotic neutrophils and delayed neutrophil apoptosis was present in vitro. Circulating levels of TNF-α, GM-CSF, sFas, and PTX3 were higher in GPA. Delayed neutrophil apoptosis was accompanied by decreased mRNA of pro-apoptotic genes and transcription factors (DIABLO, PMAIP1, BAX, CASP3, CASP7, RUNX3, E2F1, TP53) and increased anti-apoptotic CFLAR and BCL2A1 mRNA. TNF-α and sFas levels correlated with circulating apoptotic neutrophils and expression of apoptosis genes. Stimulation with TNF-α of neutrophils from controls significantly down-regulated E2F1 and CASP3 expression.Conclusions: Circulating neutrophils in GPA have anti-apoptotic phenotype involving both intrinsic and extrinsic pathways of apoptosis. This is accompanied by increased levels of circulating pro-survival factors (GM-CSF, TNF-α, sFas), independent of disease activity. Anti-apoptotic phenotype of neutrophils in GPA is reproduced by exposure to low concentrations of TNF-α.

Observation of Transverse Λ/Λ[over ¯] Hyperon Polarization in e

We report the first observation of the spontaneous polarization of Λ and Λ[over ¯] hyperons transverse to the production plane in e^{+}e^{-} annihilation, which is attributed to the effect arising from a polarizing fragmentation function. For inclusive Λ/Λ[over ¯] production, we also report results with subtracted feed-down contributions from Σ^{0} and charm. This measurement uses a dataset of 800.4 fb^{-1} collected by the Belle experiment at or near a center-of-mass energy of 10.58 GeV. We observe a significant polarization that rises with the fractional energy carried by the Λ/Λ[over ¯] hyperon.

Prevalence of Sleep Apnea in Patients with Carotid Artery Stenosis.

Obstructive sleep apnea (OSA) is a common disease affecting about 13% of men and 6% of women, usually having severe cardiovascular sequalae. OSA is responsible for the systemic inflammatory response and oxidative stress and results in endothelial injury being a risk factor for atherosclerosis. The aim of this study was to estimate the prevalence of OSA among patients with severe carotid artery stenosis. Fifty-five patients (F/M-24/31, mean age 70 ± 7 years, body mass index 28.3 ± 6.3 kg/m2) were enrolled into the study. The patients were qualified for elective surgical treatment of carotid artery stenosis. Polysomnography was performed in all patients the night before surgery. Thirty-six patients underwent surgical endarterectomy and nineteen patients underwent carotid artery stenting. Sleep apnea was diagnosed in 44 (80%) of all patients. The mean apnea-hypopnea index (AHI) was 14.5 ± 12.9. The OSA severity distribution was as follows: 22 mild, 16 moderate, and 6 severe cases. We found that the percentage of carotid endarterectomies was the greatest in mild and moderate OSA. It was approximately twofold greater than that in non-OSA patients. Carotid artery stenting was performed in nearly half of the patients in each of these groups. We conclude that OSA is highly prevalent in patients with carotid artery stenosis scheduled for carotid surgery. Nonetheless, the exact pathogenetic mechanisms underlying mutual interaction between OSA and vascular wall damage remain elusive. OSA is not routinely diagnosed among patients with advanced atherosclerosis. The study results might be an argument for performing polysomnography in patients with carotid artery stenosis.

Measurement of the τ Lepton Polarization and R(D

We report the first measurement of the τ lepton polarization P_{τ}(D^{*}) in the decay B[over ¯]→D^{*}τ^{-}ν[over ¯]_{τ} as well as a new measurement of the ratio of the branching fractions R(D^{*})=B(B[over ¯]→D^{*}τ^{-}ν[over ¯]_{τ})/B(B[over ¯]→D^{*}ℓ^{-}ν[over ¯]_{ℓ}), where ℓ^{-} denotes an electron or a muon, and the τ is reconstructed in the modes τ^{-}→π^{-}ν_{τ} and τ^{-}→ρ^{-}ν_{τ}. We use the full data sample of 772×10^{6} BB[over ¯] pairs recorded with the Belle detector at the KEKB electron-positron collider. Our results, P_{τ}(D^{*})=-0.38±0.51(stat)_{-0.16}^{+0.21}(syst) and R(D^{*})=0.270±0.035(stat)_{-0.025}^{+0.028}(syst), are consistent with the theoretical predictions of the standard model.

Circulating mitochondrial DNA in serum of patients with granulomatosis with polyangiitis.

Neutrophil is a key cell in pathophysiology of granulomatosis with polyangiitis. Recently, neutrophil extracellular traps were described in this disease. Mitochondrial DNA is also released during traps formation. We measured circulating cell-free mitochondrial and genomic DNA in serum of patients with granulomatosis with polyangiitis. Subjects with the disease (14 active and 11 in remission stage) and 10 healthy controls were enrolled. Quantitative real-time polymerase chain reaction (PCR) was used to measure 79 base pairs (bp) and 230 bp mtDNA fragments. Alu repeats were quantified to evaluate abundance of nuclear DNA in serum at the presence of plasmid control. Both fragments of mtDNA (79 bp and 230 bp) and genomic DNA were elevated significantly in granulomatosis with polyangiitis compared to controls. Only the shorter 79 bp mtDNA correlated with active stage of granulomatosis with polyangiitis and clinical symptoms. A mechanism of extracellular release of mitochondrial DNA accompanies the active stage of the disease. Circulating mtDNA is extremely high in untreated patients. This suggests that biomarker properties of mtDNA are useful for monitoring of treatment.

Observation of B

We report the first observation of the decays B^{0}→pΛ[over ¯]D^{(*)-}. The data sample of 711 fb^{-1} used in this analysis corresponds to 772×10^{6} BB[over ¯] pairs, collected at the ϒ(4S) resonance by the Belle detector at the KEKB asymmetric-energy e^{+}e^{-} collider. We observe 19.8σ and 10.8σ excesses of events for the two decay modes and measure the branching fractions of B^{0}→pΛ[over ¯]D^{-} and B^{0}→pΛ[over ¯]D^{*-} to be (25.1±2.6±3.5)×10^{-6} and (33.6±6.3±4.4)×10^{-6}, respectively, where the first uncertainties are statistical and the second are systematic. These results are not compatible with the predictions based on the generalized factorization approach. In addition, a threshold enhancement in the dibaryon (pΛ[over ¯]) system is observed, consistent with that observed in similar B decays.

Measurement of the Direct CP Asymmetry in B¯â†’X(s+dγ) Decays with a Lepton Tag.

We report the measurement of the direct CP asymmetry in the radiative B¯â†’X(s+dγ) decay using a data sample of (772 ± 11)×10(6) BB[over ¯] pairs collected at the ϒ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. The CP asymmetry is measured as a function of the photon energy threshold. For Eγ*≥2.1 GeV, where Eγ* is the photon energy in the center-of-mass frame, we obtain A(CP)(B¯â†’X(s+dγ))=(2.2±3.9±0.9)%, consistent with the standard model prediction.

Search for CP violation in τ±â†’K(S)0π±ντ decays at Belle.

We report on a search for CP violation in τ(±)→K(S)(0)π(±)ν(τ) decays using a data sample of 699 fb(-1) collected by the Belle experiment at the KEKB electron-positron asymmetric-energy collider. The CP asymmetry is measured in four bins of the invariant mass of the K(S)(0)π(±) system and found to be compatible with zero with a precision of O(10(-3)) in each mass bin. Limits for the CP violation parameter Im(η(S)) are given at the 90% confidence level. These limits are |Im(η(S))| < 0.026 or better, depending on the parametrization used to describe the hadronic form factors, and improve upon previous limits by 1 order of magnitude.

Observation of X(3872)→J/ψγ and search for X(3872)→ψ'γ in B decays.

We report a study of B→(J/ψγ)K and B→(ψ'γ)K decay modes using 772×106 B ̅B events collected at the Υ(4S) resonance with the Belle detector at the KEKB energy-asymmetric e(+)e(-) collider. We observe X(3872)→J/ψγ and report the first evidence for χ(c2)→J/ψγ in B→(X_{c ̅cγ)K decays, while in a search for X(3872)→ψ'γ no significant signal is found. We measure the branching fractions, B(B(±)→X(3872)K(±))B(X(3872)→J/ψγ)=(1.78(-0.44)(+0.48)±0.12)×10(-6), B(B(±)→χ(c2)K(±))=(1.11(-0.34)(+0.36)±0.09)×10(-5), B(B(±)→X(3872)K(±))B(X(3872)→ψ'γ)<3.45×106 (upper limit at 90% C.L.), and also provide upper limits for other searches.