Search for an Invisibly Decaying Z^{'} Boson at Belle II in e^{+}e^{-}→μ^{+}μ^{-}(e^{±}μ^{∓}) Plus Missing Energy Final States

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}.

Observation of the Radiative Decays of ϒ(1S) to χ_{c1}

We report the first observation of the radiative decay of the ϒ(1S) into a charmonium state. The significance of the observed signal of ϒ(1S)→γχ_{c1} is 6.3 standard deviations including systematics. The branching fraction is calculated to be B[ϒ(1S)→γχ_{c1}]=[4.7_{-1.8}^{+2.4}(stat)_{-0.5}^{+0.4}(sys)×10^{-5}]. We also searched for ϒ(1S) radiative decays into χ_{c0,2} and η_{c}(1S,2S), and set upper limits on their branching fractions. These results are obtained from a 24.9  fb^{-1} data sample collected with the Belle detector at the KEKB asymmetric-energy e^{+}e^{-} collider at a center-of-mass energy equal to the ϒ(2S) mass using ϒ(1S) tagging by the ϒ(2S)→ϒ(1S)π^{+}π^{-} transitions.

First Measurements of Absolute Branching Fractions of the Ξ_{c}^{0} Baryon at Belle

We present the first measurements of absolute branching fractions of Ξ_{c}^{0} decays into Ξ^{-}π^{+}, ΛK^{-}π^{+}, and pK^{-}K^{-}π^{+} final states. The measurements are made using a dataset comprising (772±11)×10^{6} BB[over ¯] pairs collected at the ϒ(4S) resonance with the Belle detector at the KEKB e^{+}e^{-} collider. We first measure the absolute branching fraction for B^{-}→Λ[over ¯]_{c}^{-}Ξ_{c}^{0} using a missing-mass technique; the result is B(B^{-}→Λ[over ¯]_{c}^{-}Ξ_{c}^{0})=(9.51±2.10±0.88)×10^{-4}. We subsequently measure the product branching fractions B(B^{-}→Λ[over ¯]_{c}^{-}Ξ_{c}^{0})B(Ξ_{c}^{0}→Ξ^{-}π^{+}), B(B^{-}→Λ[over ¯]_{c}^{-}Ξ_{c}^{0})B(Ξ_{c}^{0}→ΛK^{-}π^{+}), and B(B^{-}→Λ[over ¯]_{c}^{-}Ξ_{c}^{0})B(Ξ_{c}^{0}→pK^{-}K^{-}π^{+}) with improved precision. Dividing these product branching fractions by the result for B^{-}→Λ[over ¯]_{c}^{-}Ξ_{c}^{0} yields the following branching fractions: B(Ξ_{c}^{0}→Ξ^{-}π^{+})=(1.80±0.50±0.14)%, B(Ξ_{c}^{0}→ΛK^{-}π^{+})=(1.17±0.37±0.09)%, and B(Ξ_{c}^{0}→pK^{-}K^{-}π^{+})=(0.58±0.23±0.05)%. For the above branching fractions, the first uncertainties are statistical and the second are systematic. Our result for B(Ξ_{c}^{0}→Ξ^{-}π^{+}) can be combined with Ξ_{c}^{0} branching fractions measured relative to Ξ_{c}^{0}→Ξ^{-}π^{+} to yield other absolute Ξ_{c}^{0} branching fractions.

Observation of Transverse Λ/Λ[over ¯] Hyperon Polarization in e^{+}e^{-} Annihilation at Belle

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.

Search for a Light CP-odd Higgs Boson and Low-Mass Dark Matter at the Belle Experiment

We report on the first Belle search for a light CP-odd Higgs boson, A^{0}, that decays into low mass dark matter, χ, in final states with a single photon and missing energy. We search for events produced via the dipion transition ϒ(2S)→ϒ(1S)π^{+}π^{-}, followed by the on-shell process ϒ(1S)→γA^{0} with A^{0}→χχ, or by the off-shell process ϒ(1S)→γχχ. Utilizing a data sample of 157.3×10^{6} ϒ(2S) decays, we find no evidence for a signal. We set limits on the branching fractions of such processes in the mass ranges M_{A^{0}}<8.97  GeV/c^{2} and M_{χ}<4.44  GeV/c^{2}. We then use the limits on the off-shell process to set competitive limits on WIMP-nucleon scattering in the WIMP mass range below 5  GeV/c^{2}.

Observation of ϒ(2S)→γη_{b}(1S) Decay

We report the observation of ϒ(2S)→γη_{b}(1S) decay based on an analysis of the inclusive photon spectrum of 24.7  fb^{-1} of e^{+}e^{-} collisions at the ϒ(2S) center-of-mass energy collected with the Belle detector at the KEKB asymmetric-energy e^{+}e^{-} collider. We measure a branching fraction of B[ϒ(2S)→γη_{b}(1S)]=(6.1_{-0.7-0.6}^{+0.6+0.9})×10^{-4} and derive an η_{b}(1S) mass of 9394.8_{-3.1-2.7}^{+2.7+4.5}  MeV/c^{2}, where the uncertainties are statistical and systematic, respectively. The significance of our measurement is greater than 7 standard deviations, constituting the first observation of this decay mode.

Search for B^{-}→μ^{-}ν[over ¯]_{μ} Decays at the Belle Experiment

We report the results of a search for the rare, purely leptonic decay B^{-}→μ^{-}ν[over ¯]_{μ} performed with a 711  fb^{-1} data sample that contains 772×10^{6}  BB[over ¯] pairs, collected near the ϒ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e^{+}e^{-} collider. The signal events are selected based on the presence of a high momentum muon and the topology of the rest of the event showing properties of a generic B-meson decay, as well as the missing energy and momentum being consistent with the hypothesis of a neutrino from the signal decay. We find a 2.4 standard deviation excess above background including systematic uncertainties, which corresponds to a branching fraction of B(B^{-}→μ^{-}ν[over ¯]_{μ})=(6.46±2.22±1.60)×10^{-7} or a frequentist 90% confidence level interval on the B^{-}→μ^{-}ν[over ¯]_{μ} branching fraction of [2.9,10.7]×10^{-7}.

Evidence for Isospin Violation and Measurement of CP Asymmetries in B→K^{*}(892)γ

We report the first evidence for isospin violation in B→K^{*}γ and the first measurement of the difference of CP asymmetries between B^{+}→K^{*+}γ and B^{0}→K^{*0}γ. This analysis is based on the data sample containing 772×10^{6}BB[over ¯] pairs that was collected with the Belle detector at the KEKB energy-asymmetric e^{+}e^{-} collider. We find evidence for the isospin violation with a significance of 3.1σ, Δ_{0+}=[+6.2±1.5(stat)±0.6(syst)±1.2(f_{+-}/f_{00})]%, where the third uncertainty is due to the uncertainty on the fraction of B^{+}B^{-} to B^{0}B[over ¯]^{0} production in ϒ(4S) decays. The measured value is consistent with predictions of the standard model. The result for the difference of CP asymmetries is ΔA_{CP}=[+2.4±2.8(stat)±0.5(syst)]%, consistent with zero. The measured branching fractions and CP asymmetries for charged and neutral B meson decays are the most precise to date. We also calculate the ratio of branching fractions of B^{0}→K^{*0}γ to B_{s}^{0}→ϕγ.

Search for CP Violation and Measurement of the Branching Fraction in the Decay D^{0}→K_{S}^{0}K_{S}^{0}

We report a study of the decay D^{0}→K_{S}^{0}K_{S}^{0} using 921  fb^{-1} of data collected at or near the ϒ(4S) and ϒ(5S) resonances with the Belle detector at the KEKB asymmetric energy e^{+}e^{-} collider. The measured time-integrated CP asymmetry is A_{CP}(D^{0}→K_{S}^{0}K_{S}^{0})=(-0.02±1.53±0.02±0.17)%, and the branching fraction is B(D^{0}→K_{S}^{0}K_{S}^{0})=(1.321±0.023±0.036±0.044)×10^{-4}, where the first uncertainty is statistical, the second is systematic, and the third is due to the normalization mode (D^{0}→K_{S}^{0}π^{0}). These results are significantly more precise than previous measurements available for this mode. The A_{CP} measurement is consistent with the standard model expectation.

Preceding haemorrhagic shock as a detrimental risk factor for respiratory distress after excessive allogeneic blood transfusion

BACKGROUND AND OBJECTIVES

Whether transfusion-associated circulatory overload arises as a simple result of over-transfusion or requires another trigger remains unclear. Here, we examined whether respiratory distress could be reproduced by massive transfusion alone in an animal model.

MATERIALS AND METHODS

A total of 20 anaesthetized swine were equipped with monitors. Allogeneic blood was obtained from 10 donor swine. A 4-stage loading protocol with each stage equivalent to 25% of the blood volume (BV) in the recipient swine was then used to infuse crystalloid (CR), hydroxyethyl starch (HES) or allogeneic blood (TR) (n = 5 each). The five remaining animals were subjected to a haemorrhagic shock (HS) prior to an allogeneic blood transfusion (TRS).

RESULTS

The PaO₂ /FiO₂ (P/F) ratio did not decrease to the level of respiratory distress in either the CR group or the HES group after loading with a volume corresponding to 100% of the recipient BV. However, the TRS and TR groups exhibited significant reductions in the P/F ratio after fluid overloading (227 ± 29 and 267 ± 133, respectively). Blood transfusion after HS expanded the blood volume, but over-transfusion alone did not. HS was accompanied by an increase in the white blood cell count.

CONCLUSION

The lung and the heart can tolerate volume overloads with HES, CR and even transfused blood. However, a preceding HS may induce an inflammatory response, making the lung vulnerable to subsequent blood overloads. In this study, a preceding haemorrhagic shock mediated respiratory distress following massive transfusion in a swine model. (247 words).

Measurement of the τ Lepton Polarization and R(D^{*}) in the Decay B[over ¯]→D^{*}τ^{-}ν[over ¯]_{τ}

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.

Lepton-Flavor-Dependent Angular Analysis of B→K^{*}ℓ^{+}ℓ^{-}

We present a measurement of angular observables and a test of lepton flavor universality in the B→K^{*}ℓ^{+}ℓ^{-} decay, where ℓ is either e or μ. The analysis is performed on a data sample corresponding to an integrated luminosity of 711  fb^{-1} containing 772×10^{6} BB[over ¯] pairs, collected at the ϒ(4S) resonance with the Belle detector at the asymmetric-energy e^{+}e^{-} collider KEKB. The result is consistent with standard model (SM) expectations, where the largest discrepancy from a SM prediction is observed in the muon modes with a local significance of 2.6σ.

Observation of D^{0}→ρ^{0}γ and Search for CP Violation in Radiative Charm Decays

We report the first observation of the radiative charm decay D^{0}→ρ^{0}γ and the first search for CP violation in decays D^{0}→ρ^{0}γ, ϕγ, and K[over ¯]^{*0}(892)γ, using a data sample of 943  fb^{-1} collected with the Belle detector at the KEKB asymmetric-energy e^{+}e^{-} collider. The branching fraction is measured to be B(D^{0}→ρ^{0}γ)=(1.77±0.30±0.07)×10^{-5}, where the first uncertainty is statistical and the second is systematic. The obtained CP asymmetries A_{CP}(D^{0}→ρ^{0}γ)=+0.056±0.152±0.006, A_{CP}(D^{0}→ϕγ)=-0.094±0.066±0.001, and A_{CP}(D^{0}→K[over ¯]^{*0}γ)=-0.003±0.020±0.000 are consistent with no CP violation. We also present an improved measurement of the branching fractions B(D^{0}→ϕγ)=(2.76±0.19±0.10)×10^{-5} and B(D^{0}→K[over ¯]^{*0}γ)=(4.66±0.21±0.21)×10^{-4}.

Effects of Static Magnetic Fields on Bone Formation in Rat Osteoblast Cultures

Although the promotional effects on osteoblasts of pulsed electromagnetic fields have been well-demonstrated, the effects of static magnetic fields (SMF) remain unclear; nevertheless, magnets have been clinically used as a ’force source’ in various orthodontic treatments. We undertook the present investigation to study the effects of SMF on osteoblastic differentiation, proliferation, and bone nodule formation using a rat calvaria cell culture. During a 20-day culture, the values of the total area and the number and average size of bone nodules showed high levels in the presence of SMF. In the matrix development and mineralization stages, the calcium content in the matrix and two markers of osteoblastic phenotype (alkaline phosphatase and osteocalcin) also showed a significant increase. Accordingly, these findings suggest that SMF stimulates bone formation by promoting osteoblastic differentiation and/or activation.

Cooperative Self-Assembly of Carbazole Derivatives Driven by Multiple Dipole-Dipole Interactions

Carbazole possessing phenylisoxazoles self-assembled in a cooperative manner in decalin. X-ray crystal structure analysis revealed that the isoxazole dipoles align in a head-to-tail fashion. DFT calculations suggested that the linear array of dipoles induced the polarization of each dipole, leading to an increase in dipole-dipole interactions. This dipole polarization resulted in cooperative assembly.

First Observation of the Doubly Cabibbo-Suppressed Decay of a Charmed Baryon: Λ_{c}^{+}→pK^{+}π^{-}

We report the first observation of the decay Λ_{c}^{+}→pK^{+}π^{-} using a 980  fb^{-1} data sample collected by the Belle detector at the KEKB asymmetric-energy e^{+}e^{-} collider. This is the first observation of a doubly Cabibbo-suppressed decay of a charmed baryon. We measure the branching ratio of this decay with respect to its Cabibbo-favored counterpart to be B(Λ_{c}^{+}→pK^{+}π^{-})/B(Λ_{c}^{+}→pK^{-}π^{+})=(2.35±0.27±0.21)×10^{-3}, where the uncertainties are statistical and systematic, respectively.

Observation of Z_{b}(10610) and Z_{b}(10650) Decaying to B Mesons

We report the analysis of the three-body e^{+}e^{-}→BB[over ¯]π^{±}, BB[over ¯]^{*}π^{±}, and B^{*}B[over ¯]^{*}π^{±} processes, including the first observations of the Z_{b}^{±}(10610)→[BB[over ¯]^{*}+c.c.]^{±} and Z_{b}^{±}(10650)→[B^{*}B[over ¯]^{*}]^{±} transitions that are found to dominate the corresponding final states. We measure Born cross sections for the three-body production of σ(e^{+}e^{-}→[BB[over ¯]^{*}+c.c.]^{±}π^{∓})=[17.4±1.6(stat)±1.9(syst)]  pb and σ(e^{+}e^{-}→[B^{*}B[over ¯]^{*}]^{±}π^{∓})=[8.75±1.15(stat)±1.04(syst)]  pb and set a 90% C.L. upper limit of σ(e^{+}e^{-}→[BB[over ¯]]^{±}π^{∓})<2.9  pb. The results are based on a 121.4  fb^{-1} data sample collected with the Belle detector at a center-of-mass energy near the ϒ(10860) peak.

Sitagliptin, a dipeptidyl peptidase-4 inhibitor, increases the number of circulating CD34⁺CXCR4⁺ cells in patients with type 2 diabetes

We investigated the effects of sitagliptin, a dipeptidyl peptidase (DPP)-4 inhibitor, on the number of circulating CD34(+)CXCR4(+)cells, a candidate for endothelial progenitor cells (EPCs), plasma levels of stromal cell-derived factor (SDF)-1α, a ligand for CXCR4 receptor and a substrate for DPP-4, and plasma levels of interferon-inducible protein (IP)-10, for a substrate for DPP-4, in patients with type 2 diabetes. We studied 30 consecutive patients with type 2 diabetes who had poor glycemic control despite treatment with metformin and/or sulfonylurea. Thirty diabetic patients were randomized in a 2:1 ratio into a sitagliptin (50 mg/day) treatment group or an active placebo group (glimepiride 1 mg/day) for 12 weeks. Both groups showed similar improvements in glycemic control. The number of circulating CD34(+)CXCR4(+) cells was increased from 30.5 (20.0, 47.0)/10(6) cells at baseline to 55.5 (31.5, 80.5)/10(6) cells at 12 weeks of treatment with 50 mg/day sitagliptin (P = 0.0014), while showing no significant changes in patients treated with glimepiride. Plasma levels of SDF-1α and IP-10, both physiological substrates of endogenous DPP-4 and chemokines, were significantly decreased at 12 weeks of sitagliptin treatment. In conclusion, treatment with sitagliptin increased the number of circulating CD34(+)CXCR4(+) cells by approximately 2-fold in patients with type 2 diabetes.