Search for: All records

Plant wax n-alkanes serve as reliable biomarkers given their abundance, stability, and distribution in the sedimentary record. As a result, their utility as isotopic indicators of vegetation and hydroclimate is well-established. A less well studied aspect of plant n-alkanes is the use of their molecular distributions, or differences in the relative abundances of homologues, for chemotaxonomy. Limited plant n-alkane datasets from southern and western Africa suggest molecular distributions can differentiate C4 grasses from C3 woody vegetation. Here we examine a suite of plants from East Africa, where almost no plant biomarkers data exists from modern plants. In this study, over 100 samples of 19 species of plants were collected monthly from the Samburu National Reserve in Kenya from October 2001 to March 2003, across multiple growing seasons; n-alkane distributions and concentrations from both individual species and designated plant functional types (PFTs) - based on both photosynthetic pathway and growth form - were investigated. Previously published n-alkane data from western and southern Africa, or the "All Africa" dataset, were examined to further understand potential spatial differences in biomarker distributions. n-alkane distributions in both datasets vary in both individual species and within PFTs. Principal Components Analysis (PCA) was used to analyze distributions of n-alkanes in individual species and in PFTs, to determine the primary sources of variability. Results indicate that n-alkane distributions can be used to separate some individual species - namely, C4 grasses - and can be used to separate PFTs. C4 grasses and C3 woody vegetation were successfully separated in both datasets. Additionally, we found that n-alkane concentrations vary by four orders of magnitude across homologues and PFTs. A compiled African plant data set shows that C31 concentration is the most representative of the plant community for C4 grasses, C3 shrubs, and C3 trees and thus, is most ideal for stable isotope vegetation reconstructions. These data suggest that an organic geochemical approach to plant taxonomy is crucial to future biomarker applications for reconstructing vegetation distribution and structure in past ecosystems. 

Neogene ocean temperatures are characterized by sustained warmth during the mid-Miocene Climatic Optimum followed by gradual cooling through the late Miocene culminating in Northern Hemisphere glaciation in the early Pleistocene. While the magnitude of sea surface temperature (SST) cooling is enhanced at higher latitudes, existing records suggest that the timing is nearly synchronous across the world's oceans. However, the Nordic Seas, north of the Greenland-Scotland Ridge (GSR), experienced rapid cooling steps (14.5-14 Ma, 12.5-12 Ma, 8-6 Ma) that are out of sync with the global SST cooling trend. Here we present a new alkenone paleo-SST record from Ocean Drilling Program (ODP) site 985 in the western Norwegian Sea (66°56' N, 6°27' W) and investigate the relationships between rapid SST change, depth of the GSR, ocean circulation, and deep-water formation using proxy and model data. We find significant (p < 0.01) inverse relationships between the depth of the GSR and SSTs at ODP sites north of the ridge (985 and 907), positive relationships between GSR depth and the SST gradient across the ridge, and inverse relationships between deep water production and SST at ODP sites 985 and 907. In sum, these observations suggest that during global Miocene cooling, intervals of GSR deepening allowed for increased sea water exchange and an invigoration of deep-water production in the North Atlantic. We posit that enhanced surficial cyclonic flow in the Nordic Seas and a strengthened East Greenland Current caused rapid cooling in the western Nordic Seas. This cooling is consistent with Pliocene coupled climate model runs with altered tectonic boundary conditions simulating a deeper GSR, implying that this SST response to changes to GSR depth may be an important mechanism in high latitude Neogene climate. Furthermore, a strong linear relationship (r2 = 0.84) between ODP 985 SST and global deep ocean δ13C suggests that ocean circulation responses to tectonically forced variability in the GSR may have had an important impact on the Neogene carbon cycle. 

We report the first observation of the radiative decay $D_{s0}^{*}(2317{)}^{+}\to D_s^{*+}\gamma$ with a statistical significance exceeding 10 standard deviations. The signal is observed in the continuum $e^{+}{e}^{-}\to c\overline{c}$ process, using combined data samples of $980.4{\mathrm{fb}}^{-1}$ from Belle and $427.9{\mathrm{fb}}^{-1}$ from Belle II, collected at the KEKB and SuperKEKB asymmetric-energy $e^{+}{e}^{-}$ colliders, respectively. The branching fraction ratio $\mathcal{B}\left[D_{s0}^{*}\right(2317{)}^{+}\to D_s^{*+}\gamma ]/\mathcal{B}[D_{s0}^{*}(2317{)}^{+}\to D_s^{+}{\pi }^0]$ is measured to be $[7.13\pm 0.70(\mathrm{stat})\pm 0.26(\mathrm{syst}\left)\right]\%$ . This result provides crucial discrimination between theoretical models of the $D_{s0}^{*}(2317{)}^{+}$ structure. 

Using a data sample of $427.9{\mathrm{fb}}^{-1}$ collected by the Belle II detector at or near the $\mathrm{\Upsilon }\left(4S\right)$ and $\mathrm{\Upsilon }\left(10753\right)$ resonances, the cross sections for $e^{+}{e}^{-}\to h^{+}{h}^{-}J/\psi (h=\pi /K/p)$ at center-of-mass energies ranging from 3.8 GeV or the production threshold to $5.5/6.0/7.0\mathrm{GeV}$ have been measured via initial-state radiation. The cross sections for the processes $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}J/\psi$ and $e^{+}{e}^{-}\to K^{+}{K}^{-}J/\psi$ are consistent with previously published results. The cross sections for these channels obtained by combining with previous Belle results are also given. The process $e^{+}{e}^{-}\to p\overline{p}J/\psi$ is investigated for the first time. The yields are small and no significant structure is observed in the cross section versus energy. Searches for vector charmoniumlike states in the $h^{+}{h}^{-}J/\psi$ systems, and for associated intermediate states in the $h^{\pm }J/\psi$ systems, are also presented. 

We report a measurement of the branching fraction for the leptonic decay $B^{+}\to {\mu }^{+}{\nu }_{\mu }$ . This work presents the first $B^{+}\to {\mu }^{+}{\nu }_{\mu }$ result using Belle II data, an updated Belle measurement that supersedes the previous result, and their combination, which yields the most precise search to date. The analysis is based on $1076{\mathrm{fb}}^{-1}$ of $e^{+}{e}^{-}$ collision data collected at a center-of-mass energy of 10.58 GeV with the Belle and Belle II detectors at the KEKB and SuperKEKB colliders, respectively. We measure $\mathcal{B}(B^{+}\to {\mu }^{+}{\nu }_{\mu })=(4.4\pm 1.9\pm 1.0)\times {10}^{-7}$ , where the first uncertainty is statistical and the second systematic. The observed significance relative to the background-only hypothesis is 2.4 standard deviations. We set a 90% confidence level upper limit of $\mathcal{B}(B^{+}\to {\mu }^{+}{\nu }_{\mu })<6.7\times {10}^{-7}$ using a frequentist approach and a 90% credibility level upper limit of $\mathcal{B}(B^{+}\to {\mu }^{+}{\nu }_{\mu })<7.2\times {10}^{-7}$ using a Bayesian approach. These are the most stringent limits to date. The result is interpreted as an exclusion region in the parameter space of type II and type III two-Higgs-doublet models. We search for stable sterile neutrinos with masses $m_N\in [0,1.5]\mathrm{GeV}$ . No signal is observed, and the resulting exclusion on the squared mixing parameter $|U_{\mu N}{|}^2$ provides improvement over previous limits. We report a measurement of the partial branching fraction of semileptonic $B\to X_u\ell {\nu }_{\ell }$ decays with $p_{\mu }^B>2.2\mathrm{GeV}$ , obtaining $\mathrm{\Delta }\mathcal{B}(B\to X_u\ell {\nu }_{\ell })=(2.72\pm 0.05\pm 0.29)\times {10}^{-4}$ . We present a model-dependent study of weak annihilation decays using the muon momentum spectrum. We observe a signal of 2.4 standard deviations above the background-only hypothesis in regions where the distribution resembles that of $B\to X_u\ell {\nu }_{\ell }$ decays. 

We report the first search for the flavor-changing neutral-current decays $B\to X_s\nu \overline{\nu }$ , where $X_s$ is a hadronic system with strangeness equal to 1, in data collected with the Belle II detector at the SuperKEKB asymmetric-energy $e^{+}{e}^{-}$ collider. The data sample corresponds to an integrated luminosity of $365{\mathrm{fb}}^{-1}$ collected at the $\mathrm{\Upsilon }\left(4S\right)$ resonance and $43{\mathrm{fb}}^{-1}$ collected at a center-of-mass energy 60 MeV below resonance for estimation of $e^{+}{e}^{-}\to q\overline{q}$ continuum background. One of the $B$ mesons from the $\mathrm{\Upsilon }\left(4S\right)\to B\overline{B}$ decay is fully reconstructed in a hadronic decay mode. The $B\to X_s\nu \overline{\nu }$ decay is reconstructed with a sum-of-exclusives approach that uses 30 $X_s$ decay modes. This approach provides high sensitivity to the inclusive decay, despite the presence of two undetected neutrinos. The search is performed in three regions of the $X_s$ mass, $M_{X_s}^{\mathrm{true}}$ , chosen to separate contributions from $K$ , $K^{*}\left(892\right)$ , and heavier strange final states. We do not observe a significant signal and set upper limits at 90% confidence level on the partial branching fractions for the regions $0.0<M_{X_s}^{\mathrm{true}}<0.6\mathrm{GeV}/c^2$ , $0.6<M_{X_s}^{\mathrm{true}}<1.0\mathrm{GeV}/c^2$ , and $1.0\mathrm{GeV}/c^2<M_{X_s}^{\mathrm{true}}$ of $2.2\times {10}^{-5}$ , $9.3\times {10}^{-5}$ , and $30.9\times {10}^{-5}$ , respectively. Combining the three mass regions, we obtain the upper limit on the branching fraction, $B(B\to X_s\nu \overline{\nu })<3.3\times {10}^{-4}$ . 

A<sc>bstract</sc> Using data samples collected by the Belle and Belle II experiments at the Υ(4S) resonance with integrated luminosities of 571 fb⁻¹and 365 fb⁻¹, respectively, we measure the pseudoscalarB-meson mass difference to bem(B⁰) −m(B⁺) = (0.495 ± 0.024 ± 0.005) MeV/c². The results are based on a simultaneous fit to the variable$${\overline{M} }_{bc}$$, which is related to theBmomentum, forB⁰andB⁺candidates; and to the energy dependence of$$\mathcal{R}=\sigma ({e}^{+}{e}^{-}\to {B}^{0}{\overline{B} }^{0}) / \sigma ({e}^{+}{e}^{-}\to {B}^{+}{B}^{-})$$, which is measured using changes in the average center-of-mass energy over the data taking periods. The phase-space hypothesis$$\mathcal{R}={({p}_{{B}^{0}} /{p}_{{B}^{+}})}^{3}$$, upon which previous measurements rely, is strongly disfavored by our fit; the measured mass-difference value for the phase-space hypothesis also differs significantly from our measurement. We constrain$$\mathcal{R}$$in a broader energy range than covered by the direct measurement and extract the energy dependence of$$\mathcal{R}$$in the range from the$$B\overline{B }$$threshold up to 10.59 GeV. We interpret the results using a phenomenological model and constrain the parameters of the$$B\overline{B }$$potential in the isovector channel. 

A<sc>bstract</sc> We report a search for the lepton-flavor-violating decaysτ^±→ℓ^±α(ℓ=e,μ), whereαis an undetected spin-0 particle, such as an axion-like particle using 736 × 10⁶tau lepton pairs collected by the Belle detector at the KEKB asymmetric-energye⁺e⁻collider. We find no evidence of signal and obtain the most stringent upper limits on the branching fractions at 95% confidence level:$$\mathcal{B}$$(τ^±→ e^±α) < (0.4–6.4)×10⁻⁴and$$\mathcal{B}$$(τ^±→ μ^±α) < (0.2–3.5)×10⁻⁴at 95% confidence level for anαmass in the range 0.0≤ m_α≤1.6 GeV/c². 

A<sc>bstract</sc> We study the processesχ_bJωandχ_bJ(π⁺π⁻π⁰)_non−ω(J= 0, 1, 2) at center-of-mass energies$$\sqrt{s}$$from 10.73 to 11.02 GeV using a 142.5 fb⁻¹data sample collected with the Belle detector at the KEKB asymmetric-energye⁺e⁻collider; and at$$\sqrt{s}\sim 10.75$$GeV using a 19.8 fb⁻¹sample collected with Belle II at SuperKEKB. We find that the Υ(10753) state decays intoχ_bJωbut not intoχ_bJ(π⁺π⁻π⁰)_non−ω, while the Υ(10860) state, in contrast, decays intoχ_bJ(π⁺π⁻π⁰)_non−ωbut not intoχ_bJω. The mass and width of the Υ(10753) state are measured to be (10756.1 ± 3.4(stat.) ± 2.7(syst.)) MeV/c²and (32.2 ± 11.3(stat.) ± 14.9(syst.)) MeV. The products of the partial width toe⁺e⁻and branching fractions for Υ(10753)→ χ_b1ωand Υ(10753)→ χ_b2ωare (1.57±0.27(stat.)±0.22(syst.)) eV and (1.39±0.41(stat.)±0.33(syst.)) eV. 

We measure the time- and phase-space-integrated $CP$ asymmetry ${\mathcal{A}}_{CP}$ in $D^0\to {\pi }^{+}{\pi }^{-}{\pi }^0$ decays reconstructed in $e^{+}{e}^{-}\to c\overline{c}$ events collected by the Belle II experiment from 2019 to 2022. This sample corresponds to an integrated luminosity of $428{\mathrm{fb}}^{-1}$ . We require $D^0$ mesons to be produced in $D^{*+}\to D^0{\pi }^{+}$ decays to determine their flavor at production. Control samples of $D^0\to K^{-}{\pi }^{+}$ decays are used to correct for reconstruction-induced asymmetries. The result, ${\mathcal{A}}_{CP}\left(D^0\to {\pi }^{+}{\pi }^{-}{\pi }^0\right)=(0.29\pm 0.27\pm 0.13)\%$ , where the first uncertainty is statistical and the second systematic, is the most precise result to date and is consistent with $CP$ conservation.