1,211 research outputs found

    Measurement of branching fractions and direct CP asymmetries for B→Kπ and B→ππ decays at Belle II

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    We report measurements of the branching fractions and direct CP asymmetries of the decays B0→K+π−, B+→K+π0, B+→K0π+, and B0→K0π0, and use these for testing the standard model through an isospin-based sum rule. In addition, we measure the branching fraction and direct CP asymmetry of the decay B+→π+π0 and the branching fraction of the decay B0→π+π−. The data are collected with the Belle II detector from e+e− collisions at the Υ(4S) resonance produced by the SuperKEKB asymmetric-energy collider and contain 387×106 bottom-antibottom meson pairs. Signal yields are determined in two-dimensional fits to background-discriminating variables, and range from 500 to 3900 decays, depending on the channel. We obtain −0.03±0.13±0.04 for the sum rule in agreement with the standard model expectation of zero and with a precision comparable to the best existing determinations

    Measurement of the τ\tau-lepton mass with the Belle II experiment

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    We present a measurement of the τ\tau-lepton mass using a sample of about 175 million e+eτ+τe^+e^- \to \tau^+\tau^- events collected with the Belle II detector at the SuperKEKB e+ee^+e^- collider at a center-of-mass energy of 10.579GeV10.579\,\mathrm{Ge\kern -0.1em V}. This sample corresponds to an integrated luminosity of 190fb1190\,\mathrm{fb^{-1}}. We use the kinematic edge of the τ\tau pseudomass distribution in the decay τππ+πντ{\tau^-\to\pi^-\pi^+\pi^-\nu_\tau} and measure the τ\tau mass to be 1777.09±0.08±0.11MeV ⁣/c21777.09 \pm 0.08 \pm 0.11 \,\mathrm{Me\kern -0.1em V\!/c^2}, where the first uncertainty is statistical and the second systematic. This result is the most precise to date

    Precise measurement of the Ds+D^+_s lifetime at Belle II

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    7 pages, 4 figures, to be submitted to Physical Review LettersInternational audienceWe measure the lifetime of the Ds+D_s^+ meson using a data sample of 207 fb1^{-1} collected by the Belle II experiment running at the SuperKEKB asymmetric-energy e+ee^+ e^- collider. The lifetime is determined by fitting the decay-time distribution of a sample of 116×103116\times 10^3 Ds+ϕπ+D_s^+\rightarrow\phi\pi^+ decays. Our result is \tau^{}_{D^+_s} = (498.7\pm 1.7\,^{+1.1}_{-0.8}) fs, where the first uncertainty is statistical and the second is systematic. This result is significantly more precise than previous measurements

    ALMA-IMF. VII. First release of the full spectral line cubes: Core kinematics traced by DCN J=(3-2)

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    ALMA-IMF is an Atacama Large Millimeter/submillimeter Array (ALMA) Large Program designed to measure the core mass function (CMF) of 15 protoclusters chosen to span their early evolutionary stages. It further aims to understand their kinematics, chemistry, and the impact of gas inflow, accretion, and dynamics on the CMF. We present here the first release of the ALMA-IMF line data cubes (DR1), produced from the combination of two ALMA 12m-array configurations. The data include 12 spectral windows, with eight at 1.3mm and four at 3mm. The broad spectral coverage of ALMA-IMF (~6.7 GHz bandwidth coverage per field) hosts a wealth of simple atomic, molecular, ionised, and complex organic molecular lines. We describe the line cube calibration done by ALMA and the subsequent calibration and imaging we performed. We discuss our choice of calibration parameters and optimisation of the cleaning parameters, and we demonstrate the utility and necessity of additional processing compared to the ALMA archive pipeline. As a demonstration of the scientific potential of these data, we present a first analysis of the DCN (3-2) line. We find that DCN traces a diversity of morphologies and complex velocity structures, which tend to be more filamentary and widespread in evolved regions and are more compact in the young and intermediate-stage protoclusters. Furthermore, we used the DCN (3-2) emission as a tracer of the gas associated with 595 continuum cores across the 15 protoclusters, providing the first estimates of the core systemic velocities and linewidths within the sample. We find that DCN (3-2) is detected towards a higher percentage of cores in evolved regions than the young and intermediate-stage protoclusters and is likely a more complete tracer of the core population in more evolved protoclusters. The full ALMA 12m-array cubes for the ALMA-IMF Large Program are provided with this DR1 release.Comment: 75 pages (21 main body; 54 appendix), 37 figures. The ALMA-IMF DR1 line release is hosted at https://dataverse.harvard.edu/dataverse/alma-im

    ALMA-IMF IX: Catalog and Physical Properties of 315 SiO Outflow Candidates in 15 Massive Protoclusters

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    We present a catalog of 315 protostellar outflow candidates detected in SiO J=5-4 in the ALMA-IMF Large Program, observed with ~2000 au spatial resolution, 0.339 km/s velocity resolution, and 2-12 mJy/beam (0.18-0.8 K) sensitivity. We find median outflow masses, momenta, and kinetic energies of ~0.3 M_{\odot}, 4 M_{\odot} km/s, and 1045^{45} erg, respectively. Median outflow lifetimes are 6,000 years, yielding median mass, momentum, and energy rates of M˙\dot{M} = 104.4^{-4.4} M_{\odot} yr1^{-1}, P˙\dot{P} = 103.2^{-3.2} M_{\odot} km/s yr1^{-1}, and E˙\dot{E} = 1 L_{\odot}. We analyze these outflow properties in the aggregate in each field. We find correlations between field-aggregated SiO outflow properties and total mass in cores (~3-5σ\sigma), and no correlations above 3σ\sigma with clump mass, clump luminosity, or clump luminosity-to-mass ratio. We perform a linear regression analysis and find that the correlation between field-aggregated outflow mass and total clump mass - which has been previously described in the literature - may actually be mediated by the relationship between outflow mass and total mass in cores. We also find that the most massive SiO outflow in each field is typically responsible for only 15-30% of the total outflow mass (60% upper limit). Our data agree well with the established mechanical force-bolometric luminosity relationship in the literature, and our data extend this relationship up to L \geq 106^6 L_{\odot} and P˙\dot{P} \geq 1 M_{\odot} km/s yr1^{-1}. Our lack of correlation with clump L/M is inconsistent with models of protocluster formation in which all protostars start forming at the same time.Comment: 46 pages, 14 figures, 10 tables. This publication has an associated Zenodo entry, which can be found here: https://zenodo.org/records/835059

    Search for a long-lived spin-0 mediator in b→s transitions at the Belle II experiment

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    Additional spin-0 particles appear in many extensions of the standard model. We search for long-lived spin-0 particles S in B-meson decays mediated by a b→s quark transition in e+e− collisions at the Υ(4S) resonance at the Belle II experiment. Based on a sample corresponding to an integrated luminosity of 189  fb−1, we observe no evidence for signal. We set model-independent upper limits on the product of branching fractions B(B0→K∗(892)0(→K+π−)S)×B(S→x+x−) and B(B+→K+S)×B(S→x+x−), where x+x− indicates e+e−,μ+μ−,π+π−, or K+K−, as functions of S mass and lifetime at the level of 10−7

    Measurement of branching-fraction ratios and CPCP asymmetries in B±DCP±K±B^{\pm} \to D_{CP\pm}K^{\pm} decays at Belle and Belle II

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    We report results from a study of B±DK±B^\pm \rightarrow DK^\pm decays followed by DD decaying to CPCP~eigenstates, where DD indicates a D0D^0 or Dˉ0\bar{D}^{0} meson. These decays are sensitive to the Cabibbo-Kobayashi-Maskawa unitarity-triangle angle ϕ3\phi_{3}. The results are based on a combined analysis of the final data set of 772×106 BBˉ772 \times 10^6~B\bar{B} pairs collected by the Belle experiment and a data set of 198×106 BBˉ198 \times 10^6~B\bar{B} pairs collected by the Belle~II experiment, both in electron-positron collisions at the Υ(4S)\Upsilon(4S) resonance. We measure the CPCP asymmetries to be ACP+= (+12.5±5.8±1.4)%\mathcal{ A}_{CP +} =~(+12.5 \pm 5.8 \pm 1.4)\% and ACP= (16.7±5.7±0.6)%\mathcal{ A}_{CP -} =~(-16.7 \pm 5.7 \pm 0.6)\%, and the ratios of branching fractions to be RCP+= 1.164±0.081±0.036\mathcal{ R}_{CP+}=~1.164 \pm 0.081 \pm 0.036 and RCP= 1.151±0.074±0.019\mathcal{ R}_{CP-} =~1.151 \pm 0.074 \pm 0.019. The first contribution to the uncertainties is statistical, and the second is systematic. The asymmetries ACP+\mathcal{A}_{CP +} and ACP\mathcal{A}_{CP -} have similar magnitudes and opposite signs; their difference corresponds to 3.5~standard deviations. From these values we calculate 68.3% confidence intervals of (8.5<ϕ3<16.58.5^{\circ}<\phi_{3}<16.5^{\circ}) or (84.5<ϕ3<95.584.5^{\circ}<\phi_{3}<95.5^{\circ}) or (163.3<ϕ3<171.5163.3^{\circ}<\phi_{3}<171.5^{\circ}) and 0.321<rB<0.4650.321<r_{B}<0.465

    Observation of e+e−→ωχbJ(1P) and Search for Xb→ωϒ(1S) at s near 10.75 GeV

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    We study the processes eþ e− → ωχ bJ ð1PÞ (J ¼ 0, 1, or 2) using samples at center-of-mass energies pffiffiffi s ¼ 10.701, 10.745, and 10.805 GeV, corresponding to 1.6, 9.8, and 4.7 fb−1 of integrated luminosity, respectively. These data were collected with the Belle II detector during special operations of the SuperKEKB collider above the ϒð4SÞ resonance. We report the first observation of ωχ bJ ð1PÞ signals at pffiffiffi pffiffiffi s ¼ 10.745 GeV. By combining Belle II data with Belle results at s ¼ 10.867 GeV, we find energy dependencies of the Born cross sections for eþ e− → ωχ b1;b2 ð1PÞ to be consistent with the shape of the ϒð10753Þ state. These data indicate that the internal structures of the ϒð10753Þ and ϒð10860Þ states may pffiffiffi differ. Including data at s ¼ 10.653 GeV, we also search for the bottomonium equivalent of the Xð3872Þ state decaying into ωϒð1SÞ. No significant signal is observed for masses between 10.45 and 10.65 GeV=c2

    A test of light-lepton universality in the rates of inclusive semileptonic BB-meson decays at Belle II

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    We present the first measurement of the ratio of branching fractions of inclusive semileptonic BB-meson decays, R(Xe/μ)=B(BXeν)/B(BXμν)R(X_{e/\mu}) = \mathcal{B}(B\to X \, e \, \nu) / \mathcal{B}(B\to X \, \mu \, \nu), a precision test of electron-muon universality, using data corresponding to 189fb1189\,\mathrm{fb}^{-1} from electron-positron collisions collected with the Belle II detector. In events where the partner BB meson is fully reconstructed, we use fits to the lepton momentum spectra above 1.3GeV/c1.3\,\mathrm{GeV}/c to obtain R(Xe/μ)=1.033±0.010 (stat)±0.019 (syst)R(X_{e/\mu}) = 1.033 \pm 0.010~(\mathrm{stat}) \pm 0.019~(\mathrm{syst}), which is the most precise lepton-universality test of its kind and agrees with the standard-model expectation

    ALMA-IMF IX: Catalog and Physical Properties of 315 SiO Outflow Candidates in 15 Massive Protoclusters

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    We present a catalog of 315 protostellar outflow candidates detected in SiO J=5-4 in the ALMA-IMF Large Program, observed with ~2000 au spatial resolution, 0.339 km/s velocity resolution, and 2-12 mJy/beam (0.18-0.8 K) sensitivity. We find median outflow masses, momenta, and kinetic energies of ~0.3 M_{\odot}, 4 M_{\odot} km/s, and 1045^{45} erg, respectively. Median outflow lifetimes are 6,000 years, yielding median mass, momentum, and energy rates of M˙\dot{M} = 104.4^{-4.4} M_{\odot} yr1^{-1}, P˙\dot{P} = 103.2^{-3.2} M_{\odot} km/s yr1^{-1}, and E˙\dot{E} = 1 L_{\odot}. We analyze these outflow properties in the aggregate in each field. We find correlations between field-aggregated SiO outflow properties and total mass in cores (~3-5σσ), and no correlations above 3σσ with clump mass, clump luminosity, or clump luminosity-to-mass ratio. We perform a linear regression analysis and find that the correlation between field-aggregated outflow mass and total clump mass - which has been previously described in the literature - may actually be mediated by the relationship between outflow mass and total mass in cores. We also find that the most massive SiO outflow in each field is typically responsible for only 15-30% of the total outflow mass (60% upper limit). Our data agree well with the established mechanical force-bolometric luminosity relationship in the literature, and our data extend this relationship up to L \geq 106^6 L_{\odot} and P˙\dot{P} \geq 1 M_{\odot} km/s yr1^{-1}. Our lack of correlation with clump L/M is inconsistent with models of protocluster formation in which all protostars start forming at the same time
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