Search Results (523 total)

Using e⁺e^- collision data taken with the CLEO-c detector at the Cornell Electron Storage Ring, we have investigated the direct photon spectrum in the decay ψ(2S)→γgg. We determine the ratio of the inclusive direct photon decay rate to that of the dominant three-gluon decay rate ψ(2S)→ggg (R_γ≡Γ(γgg)/Γ(ggg)) to be R_γ(z_γ>0.4)=0.070±0.002±0.019±0.011, with z_γ defined as the scaled photon energy relative to the beam energy. The errors shown are statistical, systematic, and that due to the uncertainty in the input branching fractions used to extract the ratio, respectively.

Using the CLEO-c detector at the Cornell Electron Storage Ring, we have measured inclusive and exclusive cross sections for the production of D⁺, D⁰ and D_s⁺ mesons in e⁺e^- annihilations at 13 center-of-mass energies between 3.97 and 4.26 GeV. Exclusive cross sections are presented for final states consisting of two charm mesons (DD̅ , D^*D̅ , D^*D̅ ^*, D_s⁺D_s^-, D_s^*+D_s^-, and D_s^*+D_s^*-) and for processes in which the charm-meson pair is accompanied by a pion. No enhancement in any final state is observed at the energy of the Y(4260).

Using e⁺e^-→D_s^-D_s^*+ and D_s^*-D_s⁺ interactions at 4170 MeV collected with the CLEO-c detector, we investigate the semileptonic decays D_s⁺→f₀(980)e⁺ν and D_s⁺→ϕe⁺ν. By examining the decay rates as functions of the four-momentum transfer squared q², we measure the ratio [dB / dq²(D_s⁺→f₀(980)e⁺ν)B(f₀→π⁺π^-)]/[dB / dq²(D_s⁺→ϕe⁺ν)B(ϕ→K⁺K^-)] at q² of zero to be (42±11)%. This ratio has been predicted to equal the rate ratio [B(B_s→J/ψf₀)B(f₀→π⁺π^-)]/[B(B_s→J/ψϕ)B(ϕ→K⁺K^-)], thus indicating that the CP eigenstate J/ψf₀ could be useful for measuring CP violation via B_s mixing. Assuming a simple pole model for the form factor |f₊(q²)| in the f₀e⁺ν decay, we find a pole mass of (1.7_-0.7^+4.5±0.2)  GeV. We also determine the f₀ mass and width as (977_-9⁺¹¹±1) and (91_-22⁺³⁰±3)  MeV, respectively. In addition, we present updated results for B(D_s⁺→f₀(980)e⁺ν)B(f₀→π⁺π^-)=(0.20±0.03±0.01)% and B(D_s⁺→ϕe⁺ν)=(2.36±0.23±0.13)%. Assuming that the f₀ wave function is a combination of strange and nonstrange quark-antiquark components, we use our measurement for B(D_s⁺→f₀(980)e⁺ν) to extract a value of the mixing angle that we find consistent with ∣s̅ s⟩ dominance, adding to the mystery as to why the f₀ decays predominantly to two pions rather than two kaons.

We measure the absolute branching fractions of D_s semileptonic decays where the hadron in the final state is one of ϕ, η, η^′, K_S⁰, K^⋆0, and f₀, using 2.8×10⁵ e⁺e^-→D_sD_s^⋆ decays collected in the CLEO-c detector at a center-of-mass energy close to 4170 MeV. We obtain B(D_s⁺→ϕe⁺ν_e)=(2.29±0.37±0.11)%, B(D_s⁺→ηe⁺ν_e)=(2.48±0.29±0.13)%, B(D_s⁺→η^′e⁺ν_e)=(0.91±0.33±0.05)%, where the first uncertainties are statistical and the second are systematic. We also obtain B(D_s⁺→K⁰e⁺ν_e)=(0.37±0.10±0.02)%, and B(D_s⁺→K^⋆0e⁺ν_e)=(0.18±0.07±0.01)%, which are the first measurements of Cabibbo suppressed exclusive D_s semileptonic decays, and, B(D_s⁺→f₀e⁺ν_e)×B(f₀→π⁺π^-)=(0.13±0.04±0.01)%. This is the first absolute product branching fraction determination for a semileptonic decay including a scalar meson in the final state.

Using a sample of 2.59×10⁷ ψ(2S) decays collected by the CLEO-c detector, we present results of a search for the decay chain ψ(2S)→π⁰h_c, h_c→n(π⁺π^-)π⁰, n=1, 2, 3. We observe no significant signals for n=1 and n=3 and set upper limits for the corresponding decay rates. First evidence for the decay h_c→π⁺π^-π⁺π^-π⁰ is presented, and a product branching fraction of B(ψ(2S)→h_cπ⁰)×B(h_c→2(π⁺π^-)π⁰)=1.88_-0.45-0.30^+0.48+0.47×10^-5 is measured. This result implies that h_c→hadrons and h_c→γη_c have comparable rates, in agreement with expectations.

Using data collected near the D_s^*±D_s^∓ peak production energy E_cm=4170  MeV by the CLEO-c detector, we search for D_s⁺ exclusive hadronic decays involving ω. We find B(D_s⁺→π⁺ω)=(0.21±0.09±0.01)%, B(D_s⁺→π⁺π⁰ω)=(2.78±0.65±0.25)%, B(D_s⁺→π⁺π⁺π^-ω)=(1.58±0.45±0.09)%, B(D_s⁺→π⁺ηω)=(0.85±0.54±0.06)%, B(D_s⁺→K⁺ω)<0.24%, B(D_s⁺→K⁺π⁰ω)<0.82%, B(D_s⁺→K⁺π⁺π^-ω)<0.54%, and B(D_s⁺→K⁺ηω)<0.79%. The upper limits are at 90% confidence level.

The first measurements of the coherence factors (R_Kππ⁰ and R_K3π) and the average strong-phase differences (δ_D^Kππ0 and δ_D^K3π) for D⁰→K^-π⁺π⁰ and D⁰→K^-π⁺π⁺π^- are presented. These parameters can be used to improve the determination of the unitarity triangle angle γ in B^-→DK^- decays, where D is a D⁰ or D̅ ⁰ meson decaying to the same final state. The measurements are made using quantum-correlated, fully reconstructed D⁰D̅ ⁰ pairs produced in e⁺e^- collisions at the ψ(3770) resonance. The measured values are: R_Kππ⁰=0.84±0.07, δ_D^Kππ0=(227_-17⁺¹⁴)°, R_K3π=0.33_-0.23^+0.20, and δ_D^K3π=(114_-23⁺²⁶)°. These results indicate significant coherence in the decay D⁰→K^-π⁺π⁰, whereas lower coherence is observed in the decay D⁰→K^-π⁺π⁺π^-. The analysis also results in a small improvement in the knowledge of other D-meson parameters, in particular, the strong-phase difference for D⁰→K^-π⁺, δ_D^Kπ, and the mixing parameter y.

Using the entire CLEO-c ψ(3770)→DD̅ event sample, corresponding to an integrated luminosity of 818  pb^-1 and approximately 5.4×10⁶ DD̅ events, we present a study of the decays D⁰→π^-e⁺ν_e, D⁰→K^-e⁺ν_e, D⁺→π⁰e⁺ν_e, and D⁺→K̅ ⁰e⁺ν_e. Via a tagged analysis technique, in which one D is fully reconstructed in a hadronic mode, partial rates for semileptonic decays by the other D are measured in several q² bins. We fit these rates using several form factor parametrizations and report the results, including form factor shape parameters and the branching fractions B(D⁰→π^-e⁺ν_e)=(0.288±0.008±0.003)%, B(D⁰→K^-e⁺ν_e)=(3.50±0.03±0.04)%, B(D⁺→π⁰e⁺ν_e)=(0.405±0.016±0.009)%, and B(D⁺→K̅ ⁰e⁺ν_e)=(8.83±0.10±0.20)%, where the first uncertainties are statistical and the second are systematic. Taking input from lattice quantum chromodynamics, we also find |V_cd|=0.234±0.007±0.002±0.025 and |V_cs|=0.985±0.009±0.006±0.103, where the third uncertainties are from lattice quantum chromodynamics.

We exploit the quantum coherence between pair-produced D⁰ and D̅ ⁰ in ψ(3770) decays to make a first determination of the relative strong phase differences between D⁰→K_S⁰π⁺π^- and D̅ ⁰→K_S⁰π⁺π^-, which are of great importance in determining the Cabibbo-Kobayashi-Maskawa angle γ/ϕ₃ in B^-→D⁰(D̅ ⁰)K^- decays. Using 818  pb^-1 of e⁺e^- collision data collected with the CLEO-c detector at E_cm=3.77  GeV, we employ a binned Dalitz-plot analysis of K_S⁰π⁺π^- and K_L⁰π⁺π^- decays recoiling against flavor-tagged, CP-tagged, and K_S⁰π⁺π^--tagged events to determine these strong phase differences.

We study the inclusive decays of D_s⁺ mesons, using data collected near the D_s^*±D_s^∓ peak production energy E_cm=4170  MeV by the CLEO-c detector. We report the inclusive yields of D_s⁺ decays to K⁺X, K^-X, K_S⁰X, π⁺X, π^-X, π⁰X, ηX, η^′X, ϕX, ωX, and f₀(980)X, and also decays into pairs of kaons, D_s⁺→KK̅ X. Using these measurements, we obtain an overview of D_s⁺ decays.

Using data acquired with the CLEO-c detector at the CESR e⁺e^- collider, we measure branching fractions for J/ψ, ψ(2S), and ψ(3770) decays to γπ⁰, γη, and γη^′. Defining R_n≡B[ψ(nS)→γη]/B[ψ(nS)→γη^′], we obtain R₁=(21.1±0.9)% and, unexpectedly, an order of magnitude smaller limit, R₂<1.8% at 90% C.L. We also use J/ψ→γη^′ events to determine branching fractions of improved precision for the five most copious η^′ decay modes.

We search for simultaneous baryon and lepton number violating decays of the D⁰ meson. Specifically, we use 281  pb^-1 of data taken on the ψ(3770) resonance with the CLEO-c detector at the CESR collider to look for decays D⁰→p̅ e⁺, D̅ ⁰→p̅ e⁺, D⁰→pe^-, and D̅ ⁰→pe^-. We find no significant signals and set the following branching fraction upper limits: D⁰→p̅ e⁺(D̅ ⁰→p̅ e⁺)<1.1×10^-5 and D⁰→pe^-(D̅ ⁰→pe^-)<1.0×10^-5, both at the 90% confidence level.

We perform a Dalitz plot analysis of the decay D_s⁺→K⁺K^-π⁺ with the CLEO-c data set of 586  pb^-1 of e⁺e^- collisions accumulated at sqrt[s]=4.17  GeV. This corresponds to about 0.57×10⁶ D_s^±D_s^*∓ pairs from which we select 14 400 candidates with a background of roughly 15%. In contrast to previous measurements we find good agreement with our data only by including an additional f₀(1370)π⁺ contribution. We measure the magnitude, phase, and fit fraction of K^*(892)⁰K⁺, ϕ(1020)π⁺, K₀^*(1430)K⁺, f₀(980)π⁺, f₀(1710)π⁺, and f₀(1370)π⁺ contributions and limit the possible contributions of other KK and Kπ resonances that could appear in this decay.

Using a sample of 2.59×10⁷ ψ(2S) decays collected by the CLEO-c detector, we present results of a study of χ_c0 and χ_c2 decays into two-meson final states. We present the world’s most precise measurements of the χ_cJ,(J=0,2)→π⁺π^-, π⁰π⁰, K⁺K^-, K_S⁰K_S⁰, ηη, and η^′η^′ branching fractions, and a search for χ_c decays into ηη^′. These results shed light on the mechanism of charmonium decays into pseudoscalar mesons.

Using ψ(3770)→DD̅ events collected with the CLEO-c detector at the Cornell e⁺e^- storage ring, tagged by fully reconstructing one D meson in a hadronic decay mode, we measure absolute branching fractions and differential decay rates for D⁰→π^-e⁺ν_e, D⁺→π⁰e⁺ν_e, D⁰→K^-e⁺ν_e, and D⁺→K̅ ⁰e⁺ν_e. The measured decay rates are used to study semileptonic form factors governing these transitions and to test unquenched Lattice QCD (LQCD) calculations. We average our results with previously published CLEO-c measurements of the same quantities using a neutrino reconstruction technique. Combining LQCD calculations of form factor absolute normalizations f₊(0) and measurements of f₊^π(0)|V_cd| and f₊^K(0)|V_cs|, we find |V_cd|=0.222(8)(3)(23) and |V_cs|=1.018(10)(8)(106), where the uncertainties are statistical, experimental systematic, and from LQCD, respectively.

We have studied the leptonic decay D_s⁺→τ⁺ν_τ, via the decay channel τ⁺→e⁺ν_eν̅ _τ, using a sample of tagged D_s⁺ decays collected near the D_s^*±D_s^∓ peak production energy in e⁺e^- collisions with the CLEO-c detector. We obtain B(D_s⁺→τ⁺ν_τ)=(5.30±0.47±0.22)% and determine the decay constant f_Ds=(252.5±11.1±5.2)  MeV, where the first uncertainties are statistical and the second are systematic.

We examine e⁺e^-→D_s^-D_s^*+ and D_s^*-D_s⁺ interactions at 4170 MeV using the CLEO-c detector in order to measure the decay constant f_Ds⁺ with good precision. Previously our measurements were substantially higher than the most precise lattice based QCD calculation of (241±3)  MeV. Here we use the D_s⁺→ℓ⁺ν channel, where the ℓ⁺ designates either a μ⁺ or a τ⁺, when the τ⁺→π⁺ν̅ . Analyzing both modes independently, we determine B(D_s⁺→μ⁺ν)=(0.565±0.045±0.017)%, and B(D_s⁺→τ⁺ν)=(6.42±0.81±0.18)%. We also analyze them simultaneously to find an effective value of B^eff(D_s⁺→μ⁺ν)=(0.591±0.037±0.018)% and f_Ds⁺=(263.3±8.2±3.9)  MeV. Combining with the CLEO-c value determined independently using D_s⁺→τ⁺ν, τ⁺→e⁺νν̅ decays, we extract f_Ds⁺=(259.5±6.6±3.1)  MeV. Combining with our previous determination of B(D⁺→μ⁺ν), we extract the ratio f_Ds⁺/f_D⁺=1.26±0.06±0.02. No evidence is found for a CP asymmetry between Γ(D_s⁺→μ⁺ν) and Γ(D_s^-→μ^-ν); specifically the fractional difference in rates is measured to be (4.8±6.1)%. Finally, we find B(D_s⁺→e⁺ν)<1.2×10^-4 at 90% confidence level.

Using a 281  pb^-1 data sample collected at the ψ(3770) resonance with the CLEO-c detector at the Cornell Electron Storage Ring, we report the first observation of D⁺→ηe⁺ν_e. We also set upper limits for D⁺→η^′e⁺ν_e and D⁺→ϕe⁺ν_e that are about 2 orders of magnitude more restrictive than those obtained by previous experiments.

Using ψ(2S)→π⁺π^-J/ψ, J/ψ→γη^′ events acquired with the CLEO-c detector at the CESR e⁺e^- collider, we make the first observations of the decays η^′→π⁺π^-π⁰ and η^′→π⁺π^-e⁺e^-, measuring absolute branching fractions (37_-9⁺¹¹±4)×10^-4 and (25_-9⁺¹²±5)×10^-4, respectively. For η^′→π⁺π^-π⁰, this result probes the mechanism of isospin violation and the roles of π⁰/η/η^′-mixing and final state rescattering in strong decays. We also set upper limits on branching fractions for η^′ decays to π⁺π^-μ⁺μ^-, 2(π⁺π^-), π⁺π^-2π⁰, 2(π⁺π^-)π⁰, 3(π⁺π^-), and invisible final states.

Using samples of (5.93±0.10)×10⁶ Υ(3S) decays and (9.11±0.14)×10⁶ Υ(2S) decays collected with the CLEO detector, we report improved measurements of the following branching fractions: B(Υ(3S)→Υ(1S)π⁺π^-)=(4.46±0.01±0.13)%, B(Υ(2S)→Υ(1S)π⁺π^-)=(18.02±0.02±0.61)%, B(Υ(3S)→Υ(1S)π⁰π⁰)=(2.24±0.09±0.11)%, B(Υ(2S)→  Υ(1S)π⁰π⁰)=(8.43±0.16±0.42)%, and B(Υ(3S)→Υ(2S)π⁰π⁰)=(1.82±0.09±0.12)%. In each case, the first uncertainty reported is statistical, while the second is systematic.

Using 2.45×10⁷ ψ(2S) decays collected with the CLEO-c detector at the Cornell Electron Storage Ring we present the most precise measurements of magnetic dipole transitions in the charmonium system. We measure B(ψ(2S)→γη_c)=(4.32±0.16±0.60)×10^-3, B(J/ψ→γη_c)/B(ψ(2S)→γη_c)=4.59±0.23±0.64, and B(J/ψ→γη_c)=(1.98±0.09±0.30)%. We observe a distortion in the η_c line shape due to the photon-energy dependence of the magnetic dipole transition rate. We find that measurements of the η_c mass are sensitive to the line shape, suggesting an explanation for the discrepancy between measurements of the η_c mass in radiative transitions and other production mechanisms.

Using a data sample of 24.5×10⁶ ψ(2S) the reactions ψ(2S)→γχ_cJ, χ_cJ→γγ have been studied for the first time to determine the two-photon widths of the χ_cJ states of charmonium in their decay into two photons. The measured quantities are B(ψ(2S)→γχ_c0)×B(χ_c0→γγ)=(2.17±0.32±0.10)×10^-5 and B(ψ(2S)→γχ_c2)×B(χ_c2→γγ)=(2.68±0.28±0.15)×10^-5. Using values for B(ψ(2S)→γχ_c0,c2) and Γ(χ_c0,c2) from the literature the two-photon widths are derived to be Γ_γγ(χ_c0)=(2.36±0.35±0.22)  keV, Γ_γγ(χ_c2)=(0.66±0.07±0.06)  keV, and R≡Γ_γγ(χ_c2)/Γ_γγ(χ_c0)=0.278±0.050±0.036. The importance of the measurement of R is emphasized. For the forbidden transition, χ_c1→γγ, an upper limit of Γ_γγ(χ_c1)<0.03  keV is established.

In this Letter, we describe a search for lepton flavor violation (LFV) in the bottomonium system. We search for leptonic decays Υ(nS)→μτ (n=1, 2, and 3) using the data collected with the CLEO III detector. We identify the τ lepton using its leptonic decay ν_τν̅ _ee and utilize multidimensional likelihood fitting with probability density function shapes measured from independent data samples. We report our estimates of 95% C.L. upper limits on LFV branching fractions of Υ mesons. We interpret our results in terms of the exclusion plot for the energy scale of a hypothetical new interaction versus its effective LFV coupling in the framework of effective field theory.

Using Υ(2S) and Υ(3S) data collected with the CLEO III detector we have searched for decays of χ_bJ to final states with open charm. We fully reconstruct D⁰ mesons with p_D⁰>2.5  GeV/c in three decay modes (K^-π⁺, K^-π⁺π⁰, and K^-π^-π⁺π⁺) in coincidence with radiative transition photons that tag the production of one of the χ_bJ(nP) states. Significant signals are obtained for the two J=1 states. Recent nonrelativistic QCD (NRQCD) calculations of χ_bJ(nP)→cc̅ X depend on one nonperturbative parameter per χ_bJ triplet. The extrapolation from the observed D⁰X rate over a limited momentum range to a full cc̅ X rate also depends on these same parameters. Using our data to fit for these parameters, we extract results which agree well with NRQCD predictions, confirming the expectation that charm production is largest for the J=1 states. In particular, for J=1, our results are consistent with cc̅ g accounting for about one-quarter of all hadronic decays.

We study exclusive χ_c0,1,2 decays to four-hadron final states involving two charged and two neutral hadrons: π⁺π^-π⁰π⁰, K⁺K^-π⁰π⁰, pp̅ π⁰π⁰, K⁺K^-ηπ⁰, and K^±π^∓K⁰π⁰. The χ_c states are produced in radiative decays of 3.08×10⁶ ψ(2S) resonance decays and observed in the CLEO detector. We also measure the largest substructure contributions to the modes π⁺π^-π⁰π⁰ and K^±π^∓K⁰π⁰.