Measurement of the CP asymmetry in D+→π+π0D^+ \to \pi^+ \pi^0 decays at Belle II

We measure the CP asymmetry in $D^+ \to \pi^+ \pi^0$ decays reconstructed in $e^+ e^-$ collisions at the Belle II experiment using a data set corresponding to an integrated luminosity of 428 fb$^{-1}$. A control sample of $D^+ \to \pi^+ K_{S}$ decays is used to correct for detection and production asymmetries. The result, $A_{CP}(D^+ \to \pi^+\pi^0) =(-1.8 \pm 0.9 \pm 0.1)\%$, where the first uncertainty is statistical and the second systematic, is the most precise determination to date. It agrees with the prediction of CP symmetry from the standard model, and with results of previous measurements

Measurement of the branching fractions of Bˉ→D(∗)K−K(S)(∗)0\bar{B}\to D^{(*)} K^- K^{(*)0}_{(S)} and Bˉ→D(∗)Ds−\bar{B}\to D^{(*)}D_s^{-} decays at Belle II

International audienceWe present measurements of the branching fractions of eight $\overline B{}^0\to D^{(*)+} K^- K^{(*)0}_{(S)}$, $B^{-}\to D^{(*)0} K^- K^{(*)0}_{(S)}$ decay channels. The results are based on data from SuperKEKB electron-positron collisions at the $\Upsilon(4S)$ resonance collected with the Belle II detector, corresponding to an integrated luminosity of $362~\text{fb}^{-1}$. The event yields are extracted from fits to the distributions of the difference between expected and observed $B$ meson energy, and are efficiency-corrected as a function of $m(K^-K^{(*)0}_{(S)})$ and $m(D^{(*)}K^{(*)0}_{(S)})$ in order to avoid dependence on the decay model. These results include the first observation of $\overline B{}^0\to D^+K^-K_S^0$, $B^-\to D^{*0}K^-K_S^0$, and $\overline B{}^0\to D^{*+}K^-K_S^0$ decays and a significant improvement in the precision of the other channels compared to previous measurements. The helicity-angle distributions and the invariant mass distributions of the $K^- K^{(*)0}_{(S)}$ systems are compatible with quasi-two-body decays via a resonant transition with spin-parity $J^P=1^-$ for the $K^-K_S^0$ systems and $J^P= 1^+$ for the $K^-K^{*0}$ systems. We also present measurements of the branching fractions of four $\overline B{}^0\to D^{(*)+} D_s^-$, $B^{-}\to D^{(*)0} D_s^-$ decay channels with a precision compatible to the current world averages

Measurement of the branching fractions of B‾ \overline{B} → D(∗)^{(*)}K−K(S)(∗)0^{−} {K}_{(S)}^{\left(\ast \right)0} and B‾ \overline{B} → D(∗)Ds−^{(*)} {D}_s^{-} decays at Belle II

We present measurements of the branching fractions of eight ${\overline{B}}^0$ → D$^{(*)+}$K$^{−} {K}_{(S)}^{\left(\ast \right)0}$, B$^{−}$ → D$^{(*)0}$K$^{−} {K}_{(S)}^{\left(\ast \right)0}$ decay channels. The results are based on data from SuperKEKB electron-positron collisions at the Υ(4S) resonance collected with the Belle II detector, corresponding to an integrated luminosity of 362 fb$^{−1}$. The event yields are extracted from fits to the distributions of the difference between expected and observed B meson energy, and are efficiency-corrected as a function of m(K$^{−} {K}_{(S)}^{\left(\ast \right)0}$) and m(D$^{(*)} {K}_{(S)}^{\left(\ast \right)0}$) in order to avoid dependence on the decay model. These results include the first observation of ${\overline{B}}^0$ → D$^{+}$K$^{−} {K}_S^0$, B$^{−}$ → D*$^{0}$K$^{−} {K}_S^0$, and ${\overline{B}}^0$ → D*$^{+}$K$^{−} {K}_S^0$ decays and a significant improvement in the precision of the other channels compared to previous measurements. The helicity-angle distributions and the invariant mass distributions of the K$^{−} {K}_{(S)}^{\left(\ast \right)0}$ systems are compatible with quasi-two-body decays via a resonant transition with spin-parity J$^{P}$ = 1$^{−}$ for the K$^{−} {K}_S^0$ systems and J$^{P}$ = 1$^{+}$ for the K$^{−}$K*$^{0}$ systems. We also present measurements of the branching fractions of four ${\overline{B}}^0$ → D$^{(*)+} {D}_s^{-}$, B$^{−}$ → D$^{(*)0} {D}_s^{-}$ decay channels with a precision compatible to the current world averages.[graphic not available: see fulltext

Measurement of the electron charge asymmetry in ppˉ→W+X→eν+X\boldsymbol{p\bar{p}\rightarrow W+X \rightarrow e\nu +X} decays in ppˉ\boldsymbol{p\bar{p}} collisions at s=1.96\boldsymbol{\sqrt{s}=1.96}~TeV

We present a measurement of the electron charge asymmetry in $p\bar{p}\rightarrow W+X \rightarrow e\nu +X$ events at a center-of-mass energy of 1.96 TeV, using data corresponding to 9.7~fb$^{-1}$ of integrated luminosity collected with the D0 detector at the Fermilab Tevatron Collider. The asymmetry is measured as a function of the electron pseudorapidity and is presented in five kinematic bins based on the electron transverse energy and the missing transverse energy in the event. The measured asymmetry is compared with next-to-leading-order predictions in perturbative quantum chromodynamics and provides accurate information for the determination of parton distribution functions of the proton. This is the most precise lepton charge asymmetry measurement to date.We present a measurement of the electron charge asymmetry in pp¯→W+X→eν+X events at a center-of-mass energy of 1.96 TeV, using data corresponding to 9.7  fb−1 of integrated luminosity collected with the D0 detector at the Fermilab Tevatron Collider. The asymmetry is measured as a function of the electron pseudorapidity and is presented in five kinematic bins based on the electron transverse energy and the missing transverse energy in the event. The measured asymmetry is compared with next-to-leading-order predictions in perturbative quantum chromodynamics and provides accurate information for the determination of parton distribution functions of the proton. This is the most precise lepton charge asymmetry measurement to date.We present a measurement of the electron charge asymmetry in $p\bar{p}\rightarrow W+X \rightarrow e\nu +X$ events at a center-of-mass energy of 1.96 TeV, using data corresponding to 9.7~fb$^{-1}$ of integrated luminosity collected with the D0 detector at the Fermilab Tevatron Collider. The asymmetry is measured as a function of the electron pseudorapidity and is presented in five kinematic bins based on the electron transverse energy and the missing transverse energy in the event. The measured asymmetry is compared with next-to-leading-order predictions in perturbative quantum chromodynamics and provides accurate information for the determination of parton distribution functions of the proton. This is the most precise lepton charge asymmetry measurement to date

Measurement of the ϕη∗\phi^*_\eta distribution of muon pairs with masses between 30 and 500 GeV in 10.4 fb−1^{-1} of ppˉp\bar{p} collisions

We present a measurement of the distribution of the variable $\phi^*_\eta$ for muon pairs with masses between 30 and 500 GeV, using the complete Run II data set collected by the D0 detector at the Fermilab Tevatron proton-antiproton collider. This corresponds to an integrated luminosity of 10.4 fb$^{-1}$ at $\sqrt{s}$ = 1.96 TeV. The data are corrected for detector effects and presented in bins of dimuon rapidity and mass. The variable $\phi^*_\eta$ probes the same physical effects as the $Z/\gamma^*$ boson transverse momentum, but is less susceptible to the effects of experimental resolution and efficiency. These are the first measurements at any collider of the $\phi^*_\eta$ distributions for dilepton masses away from the $Z\rightarrow \ell^+\ell^-$ boson mass peak. The data are compared to QCD predictions based on the resummation of multiple soft gluons.We present a measurement of the distribution of the variable ϕη* for muon pairs with masses between 30 and 500 GeV, using the complete run II data set collected by the D0 detector at the Fermilab Tevatron proton-antiproton collider. This corresponds to an integrated luminosity of 10.4  fb−1 at s=1.96  TeV. The data are corrected for detector effects and presented in bins of dimuon rapidity and mass. The variable ϕη* probes the same physical effects as the Z/γ* boson transverse momentum, but is less susceptible to the effects of experimental resolution and efficiency. These are the first measurements at any collider of the ϕη* distributions for dilepton masses away from the Z→ℓ+ℓ- boson mass peak. The data are compared to QCD predictions based on the resummation of multiple soft gluons.We present a measurement of the distribution of the variable $\phi^*_\eta$ for muon pairs with masses between 30 and 500 GeV, using the complete Run II data set collected by the D0 detector at the Fermilab Tevatron proton-antiproton collider. This corresponds to an integrated luminosity of 10.4 fb$^{-1}$ at $\sqrt{s}$ = 1.96 TeV. The data are corrected for detector effects and presented in bins of dimuon rapidity and mass. The variable $\phi^*_\eta$ probes the same physical effects as the $Z/\gamma^*$ boson transverse momentum, but is less susceptible to the effects of experimental resolution and efficiency. These are the first measurements at any collider of the $\phi^*_\eta$ distributions for dilepton masses away from the $Z\rightarrow \ell^+\ell^-$ boson mass peak. The data are compared to QCD predictions based on the resummation of multiple soft gluons

Test of light-lepton universality in τ\tau decays with the Belle II experiment

International audienceWe present a measurement of the ratio $R_\mu = \mathcal{B}(\tau^-\to \mu^-\bar\nu_\mu\nu_\tau) / \mathcal{B}(\tau^-\to e^-\bar\nu_e\nu_\tau)$ of branching fractions $\mathcal{B}$ of the $\tau$ lepton decaying to muons or electrons using data collected with the Belle II detector at the SuperKEKB $e^+e^-$ collider. The sample has an integrated luminosity of 362 fb$^{-1}$ at a centre-of-mass energy of 10.58 GeV. Using an optimised event selection, a binned maximum likelihood fit is performed using the momentum spectra of the electron and muon candidates. The result, $R_\mu = 0.9675 \pm 0.0007 \pm 0.0036$, where the first uncertainty is statistical and the second is systematic, is the most precise to date. It provides a stringent test of the light-lepton universality, translating to a ratio of the couplings of the muon and electron to the $W$ boson in $\tau$ decays of $0.9974 \pm 0.0019$, in agreement with the standard model expectation of unity