Search

Using (9.32, 5.88) million ${\rm Y}(2S,3S)$ decays taken with the CLEO III detector, we obtain five product branching fractions for the exclusive processes ${\rm Y}(2S)\to \gamma {\chi }_{b0,1,2}(1P)\to \gamma \gamma {\rm Y}(1S)$ and ${\rm Y}(3S)\to \gamma {\chi }_{b1,2}(1P)\to \gamma \gamma {\rm Y}(1S)$. We observe the transition ${\chi }_{b0}(1P)\to \gamma {\rm Y}(1S)$ for the first time. Using the known branching fractions for $\mathcal{B}[{\rm Y}(2S)\to \gamma {\chi }_{bJ}(1P)]$, we extract values for $\mathcal{B}[{\chi }_{bJ}(1P)\to \gamma {\rm Y}(1S)]$ for $J=0$, 1, 2. In turn, these values can be used to unfold the ${\rm Y}(3S)$ product branching fractions to obtain values for $\mathcal{B}[{\rm Y}(3S)\to \gamma {\chi }_{b1,2}(1P)]$ for the first time individually. Comparison of these with each other and with the branching fraction $\mathcal{B}[{\rm Y}(3S)\to \gamma {\chi }_{b0}]$ previously measured by CLEO provides tests of relativistic corrections to electric dipole matrix elements.

We study the inclusive decays of $D_s^{+}$ mesons, using data collected near the $D_s^{*\pm }{D}_s^{\mp }$ peak production energy $E_{\mathrm{cm}}=4170\mathrm{MeV}$ by the CLEO-c detector. We report the inclusive yields of $D_s^{+}$ decays to $K^{+}X$, $K^{-}X$, $K_S^{0}X$, ${\pi }^{+}X$, ${\pi }^{-}X$, ${\pi }^{0}X$, $\eta X$, ${\eta }^{\prime }X$, $\varphi X$, $\omega X$, and $f_0(980)X$, and also decays into pairs of kaons, $D_s^{+}\to K\overline{K}X$. Using these measurements, we obtain an overview of $D_s^{+}$ decays.

We present measurements of the inclusive branching fractions for the decays $D^{+}\to X{e}^{+}{\nu }_e$ and $D^0\to X{e}^{+}{\nu }_e$, using $281{\mathrm{pb}}^{-1}$ of data collected on the $\psi (3770)$ resonance with the CLEO-c detector. We find $\mathcal{B}(D^0\to X{e}^{+}{\nu }_e)=(6.46\pm 0.17\pm 0.13)\%$ and $\mathcal{B}(D^{+}\to X{e}^{+}{\nu }_e)=(16.13\pm 0.20\pm 0.33)\%$. Using the known $D$ meson lifetimes, we obtain the ratio ${\Gamma }_{D^{+}}^{\mathrm{sl}}/{\Gamma }_{D^0}^{\mathrm{sl}}=0.985\pm 0.028\pm 0.015$, confirming isospin invariance at the level of 3%. The positron momentum spectra from $D^{+}$ and $D^0$ have consistent shapes.

Using a sample of $3.08\times {10}^6$ $\psi (2S)$ decays collected at $\sqrt{s}=3.686\mathrm{GeV}$ with the CLEO detector at the Cornell Electron Storage Ring, we have measured the branching fractions for $\psi (2S)$ decays to pseudoscalar pairs ${\pi }^{+}{\pi }^{-}$, $K^{+}{K}^{-}$ and $K_S^0{K}_L^0$. We obtain $\mathcal{B}(\psi (2S)\to {\pi }^{+}{\pi }^{-})<2.1\times {10}^{-5}$ (90% C.L.), $\mathcal{B}(\psi (2S)\to K^{+}{K}^{-})=(6.3\pm 0.6(\mathrm{stat})\pm 0.3(\mathrm{syst}))\times {10}^{-5}$, and $\mathcal{B}(\psi (2S)\to K_S^0{K}_L^0)=(5.8\pm 0.8(\mathrm{stat})\pm 0.4(\mathrm{syst}))\times {10}^{-5}$. The branching fractions allow extraction of the relative phase $\Delta =(95\pm 15)°$ and strength ratio $R=(2.5\pm 0.4)$ of the three-gluon and one-photon amplitudes for these modes.

This paper presents a measurement of the charged current interaction rate of the electron neutrino beam component of the beam above 1.5 GeV using the large fiducial mass of the T2K ${\pi }^0$ detector. The predominant portion of the ${\nu }_e$ flux ($\sim 85\%$) at these energies comes from kaon decays. The measured ratio of the observed beam interaction rate to the predicted rate in the detector with water targets filled is $0.89\pm 0.08(\text{stat})\pm 0.11(\text{sys})$, and with the water targets emptied is $0.90\pm 0.09(\text{stat})\pm 0.13(\text{sys})$. The ratio obtained for the interactions on water only from an event subtraction method is $0.87\pm 0.33(\text{stat})\pm 0.21(\text{sys})$. This is the first measurement of the interaction rate of electron neutrinos on water, which is particularly of interest to experiments with water Cherenkov detectors.

Using $586{\mathrm{pb}}^{-1}$ of $e^{+}{e}^{-}$ collision data at $E_{\mathrm{c}.\mathrm{m}.}=4170\mathrm{MeV}$, produced at the Cornell Electron Storage Ring collider and collected with the CLEO-c detector, we observe the process $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}{h}_c(1P)$. We measure its cross section to be $15.6\pm 2.3\pm 1.9\pm 3.0\mathrm{pb}$, where the third error is due to the external uncertainty on the branching fraction of $\psi (2S)\to {\pi }^0{h}_c(1P)$, which we use for normalization. We also find evidence for $e^{+}{e}^{-}\to \eta h_c(1P)$ at 4170 MeV at the $3\sigma$ level and see hints of a rise in the $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}{h}_c(1P)$ cross section at 4260 MeV.

A class of extensions of the Standard Model allows Lorentz and $CPT$ violations, which can be identified by the observation of sidereal modulations in the neutrino interaction rate. A search for such modulations was performed using the T2K on-axis near detector. Two complementary methods were used in this study, both of which resulted in no evidence of a signal. Limits on associated Lorentz and $CPT$-violating terms from the Standard Model extension have been derived by taking into account their correlations in this model for the first time. These results imply such symmetry violations are suppressed by a factor of more than $10^{20}$ at the GeV scale.

The T2K Collaboration reports a precision measurement of muon neutrino disappearance with an off-axis neutrino beam with a peak energy of 0.6 GeV. Near detector measurements are used to constrain the neutrino flux and cross section parameters. The Super-Kamiokande far detector, which is 295 km downstream of the neutrino production target, collected data corresponding to $3.01\times {10}^{20}$ protons on target. In the absence of neutrino oscillations, $205\pm 17$ (syst) events are expected to be detected while only 58 muon neutrino event candidates are observed. A fit to the neutrino rate and energy spectrum, assuming three neutrino flavors and normal mass hierarchy yields a best-fit mixing angle ${sin}^2({\theta }_{23})=0.514\pm 0.082$ and mass splitting $|\Delta m_{32}^2|={2.44}_{-0.15}^{+0.17}\times {10}^{-3}{\mathrm{eV}}^2/c^4$. Our result corresponds to the maximal oscillation disappearance probability.

The first flavor-tagged amplitude analysis of the decay $D^0$ to the self-conjugate final state $K^{+}{K}^{-}{\pi }^{+}{\pi }^{-}$ is presented. Approximately 3000 signal decays are selected from data acquired by the CLEO II.V, CLEO III, and CLEO-c detectors. The three most significant amplitudes, which contribute to the model that best fits the data, are $\varphi {\rho }^0$, $K_1(1270{)}^{\pm }{K}^{\mp }$, and nonresonant $K^{+}{K}^{-}{\pi }^{+}{\pi }^{-}$. Separate amplitude analyses of $D^0$ and ${\overline{D}}^0$ candidates indicate no $CP$ violation among the amplitudes at the level of 5% to 30% depending on the mode. In addition, the sensitivity to the $CP$-violating parameter $\gamma /{\varphi }_3$ from a sample of 2000 $B^{+}\to {\tilde{D}}^0(K^{+}{K}^{-}{\pi }^{+}{\pi }^{-})K^{+}$ decays, where $\tilde{D}$ is a $D^0$ or ${\overline{D}}^0$, collected at LHCb or a future flavor facility, is estimated to be $(11.3\pm 0.3)°$ using the favored model.

We report the first observation of ${\rm Y}(2S)\to \eta {\rm Y}(1S)$, with a branching fraction $\mathcal{B}=\mathbf{(}{2.1}_{-0.6}^{+0.7}(\mathrm{stat})\pm 0.3(\mathrm{syst})\mathbf{)}\times {10}^{-4}$ and a statistical significance $5.3\sigma$. Data were acquired with the CLEO III detector at the CESR $e^{+}{e}^{-}$ symmetric collider. This is the first process observed involving a $b$-quark spin flip. For related transitions, 90% confidence limits in units of ${10}^{-4}$ are $\mathcal{B}\mathbf{(}{\rm Y}(2S)\to {\pi }^0{\rm Y}(1S)\mathbf{)}<1.8$, $\mathcal{B}\mathbf{(}{\rm Y}(3S)\to \eta {\rm Y}(1S)\mathbf{)}<1.8$, $\mathcal{B}\mathbf{(}{\rm Y}(3S)\to {\pi }^0{\rm Y}(1S)\mathbf{)}<0.7$, and $\mathcal{B}\mathbf{(}{\rm Y}(3S)\to {\pi }^0{\rm Y}(2S)\mathbf{)}<5.1$.

Using data acquired with the CLEO-c detector at the CESR $e^{+}{e}^{-}$ collider, we measure branching fractions for $J/\psi$, $\psi (2S)$, and $\psi (3770)$ decays to $\gamma {\pi }^0$, $\gamma \eta$, and $\gamma {\eta }^{\prime }$. Defining $R_n\equiv \mathcal{B}[\psi (nS)\to \gamma \eta ]/\mathcal{B}[\psi (nS)\to \gamma {\eta }^{\prime }]$, we obtain $R_1=(21.1\pm 0.9)\%$ and, unexpectedly, an order of magnitude smaller limit, $R_2<1.8\%$ at 90% C.L. We also use $J/\psi \to \gamma {\eta }^{\prime }$ events to determine branching fractions of improved precision for the five most copious ${\eta }^{\prime }$ decay modes.

We report the first determination of the relative strong-phase difference between $D^0\to K_{S,L}^0{K}^{+}{K}^{-}$ and ${\overline{D}}^0\to K_{S,L}^0{K}^{+}{K}^{-}$. In addition, we present updated measurements of the relative strong-phase difference between $D^0\to K_{S,L}^0{\pi }^{+}{\pi }^{-}$ and ${\overline{D}}^0\to K_{S,L}^0{\pi }^{+}{\pi }^{-}$. Both measurements exploit the quantum coherence between a pair of $D^0$ and ${\overline{D}}^0$ mesons produced from $\psi (3770)$ decays. The strong-phase differences measured are important for determining the Cabibbo-Kobayashi-Maskawa angle $\gamma /{\varphi }_3$ in $B^{-}\to K^{-}{\tilde{D}}^0$ decays, where ${\tilde{D}}^0$ is a $D^0$ or ${\overline{D}}^0$ meson decaying to $K_S^0{h}^{+}{h}^{-}$ ($h=\pi$, $K$), in a manner independent of the model assumed to describe the $D^0\to K_S^0{h}^{+}{h}^{-}$ decay. Using our results, the uncertainty in $\gamma /{\varphi }_3$ due to the error on the strong-phase difference is expected to be between 1.7° and 3.9° for an analysis using $B^{-}\to K^{-}{\tilde{D}}^0$, ${\tilde{D}}^0\to K_S^0{\pi }^{+}{\pi }^{-}$ decays, and between 3.2° and 3.9° for an analysis based on $B^{-}\to K^{-}{\tilde{D}}^0$, ${\tilde{D}}^0\to K_S^0{K}^{+}{K}^{-}$ decays. A measurement is also presented of the $CP$-odd fraction, ${\mathcal{F}}_{-}$, of the decay $D^0\to K_S^0{K}^{+}{K}^{-}$ in the region of the $\varphi \to K^{+}{K}^{-}$ resonance. We find that in a region within $0.01{\mathrm{GeV}}^2/c^4$ of the nominal $\varphi$ mass squared ${\mathcal{F}}_{-}>0.91$ at the 90% confidence level.

We search for a non-SM-like $CP$-odd Higgs boson ($a_1^0$) decaying to ${\tau }^{+}{\tau }^{-}$ or ${\mu }^{+}{\mu }^{-}$ in radiative decays of the ${\rm Y}(1S)$. No significant signal is found, and upper limits on the product branching ratios are set. Our ${\tau }^{+}{\tau }^{-}$ results are almost 2 orders of magnitude more stringent than previous upper limits. Our data provide no evidence for a Higgs state with a mass of 214 MeV decaying to ${\mu }^{+}{\mu }^{-}$, previously proposed as an explanation for 3 ${\Sigma }^{+}\to p{\mu }^{+}{\mu }^{-}$ events observed by the HyperCP experiment. Our results constrain NMSSM models.

A precision measurement of the $D^0$ meson mass has been made using $\sim 281{\mathrm{pb}}^{-1}$ of $e^{+}{e}^{-}$ annihilation data taken with the CLEO-c detector at the $\psi (3770)$ resonance. The exclusive decay $D^0\to K_S\varphi$ has been used to obtain $M(D^0)=1864.847\pm 0.150(\mathrm{stat})\pm 0.095(\mathrm{syst})\mathrm{MeV}$. This corresponds to $M(D^0{\overline{D}}^{*0})=3871.81\pm 0.36\mathrm{MeV}$, and leads to a well-constrained determination of the binding energy of the proposed $D^0{\overline{D}}^{*0}$ molecule $X(3872)$, as $E_b=0.6\pm 0.6\mathrm{MeV}$.

The T2K off-axis near detector, ND280, is used to make the first differential cross section measurements of muon neutrino charged current single positive pion production on a water target at energies $\sim 0.8\mathrm{GeV}$. The differential measurements are presented as a function of the muon and pion kinematics, in the restricted phase space defined by $p_{{\pi }^{+}}>200\mathrm{MeV}/c$, $p_{\mu }>200\mathrm{MeV}/c$, $\cos ({\theta }_{{\pi }^{+}})>0.3$ and $\cos ({\theta }_{\mu })>0.3$. The total flux integrated ${\nu }_{\mu }$ charged current single positive pion production cross section on water in the restricted phase space is measured to be $⟨\sigma {⟩}_{\varphi }=4.25\pm 0.48(\mathrm{stat})\pm 1.56(\mathrm{syst})\times {10}^{-40}{\mathrm{cm}}^2/\text{nucleon}$. The total cross section is consistent with the NEUT prediction ($5.03\times {10}^{-40}{\mathrm{cm}}^2/\text{nucleon}$) and $2\sigma$ lower than the GENIE prediction ($7.68\times {10}^{-40}{\mathrm{cm}}^2/\text{nucleon}$). The differential cross sections are in good agreement with the NEUT generator. The GENIE simulation reproduces well the shapes of the distributions, but overestimates the overall cross section normalization.

This Letter reports the first scientific results from the observation of antineutrinos emitted by fission products of ${}^{235}\mathrm{U}$ at the High Flux Isotope Reactor. PROSPECT, the Precision Reactor Oscillation and Spectrum Experiment, consists of a segmented 4 ton ${}^6\mathrm{Li}$-doped liquid scintillator detector covering a baseline range of 7–9 m from the reactor and operating under less than 1 m water equivalent overburden. Data collected during 33 live days of reactor operation at a nominal power of 85 MW yield a detection of $25461\pm 283(\mathrm{stat})$ inverse beta decays. Observation of reactor antineutrinos can be achieved in PROSPECT at $5\sigma$ statistical significance within 2 h of on-surface reactor-on data taking. A reactor model independent analysis of the inverse beta decay prompt energy spectrum as a function of baseline constrains significant portions of the previously allowed sterile neutrino oscillation parameter space at 95% confidence level and disfavors the best fit of the reactor antineutrino anomaly at $2.2\sigma$ confidence level.

T2K reports its first results in the search for $CP$ violation in neutrino oscillations using appearance and disappearance channels for neutrino- and antineutrino-mode beams. The data include all runs from January 2010 to May 2016 and comprise $7.482\times 10^{20}$ protons on target in neutrino mode, which yielded in the far detector 32 $e$-like and $135\mu$-like events, and $7.471\times 10^{20}$ protons on target in antineutrino mode, which yielded 4 $e$-like and $66\mu$-like events. Reactor measurements of ${\sin }^{2}2{\theta }_{13}$ have been used as an additional constraint. The one-dimensional confidence interval at 90% for the phase ${\delta }_{CP}$ spans the range ($-3.13$, $-0.39$) for normal mass ordering. The $CP$ conservation hypothesis (${\delta }_{CP}=0$, $\pi$) is excluded at 90% C.L.