Search Results (406 total)

We report on a study of exclusive radiative decays of the Υ(1S) resonance into the final states γπ⁰π⁰, γηη and γπ⁰η, using 1.13  fb^-1 of e⁺e^- annihilation data collected at sqrt[s]=9.46  GeV with the CLEO III detector operating at the Cornell Electron Storage Ring. In the channel γπ⁰π⁰, we measure the branching ratio for the decay mode Υ(1S)→γf₂(1270) to be (10.5±1.6(stat)_-1.8^+1.9(syst))×10^-5. We place upper limits on the product branching ratios for the isoscalar resonances f₀(1500) and f₀(1710) for the π⁰π⁰ and ηη decay channels. We also set an upper limit on the Υ(1S) radiative decay into π⁰η.

Using CLEO data, we study the production of the antideuteron, d̅ , in Υ(nS) resonance decays and the nearby continuum. The branching ratios obtained are B^dir(Υ(1S)→d̅ X)=(3.36±0.23±0.25)×10^-5, B(Υ(1S)→d̅ X)=(2.86±0.19±0.21)×10^-5, and B(Υ(2S)→d̅ X)=(3.37±0.50±0.25)×10^-5, where the “dir” superscript indicates that decays produced via reannihilation of the bb̅ pair to a γ^* are removed from both the signal and the normalizing number of Υ(1S) decays in order to isolate direct decays of the Υ(1S) to ggg, ggγ. Upper limits at 90% C.L. are given for B(Υ(4S)→d̅ X)<1.3×10^-5, and continuum production σ(e⁺e^-→d̅ X)<0.031  pb. The Υ(2S) data is also used to extract a limit on χ_bJ→d̅ X. The results indicate enhanced deuteron production in ggg, ggγ hadronization compared to γ^*→qq̅ . Baryon number compensation is also investigated with the large Υ(1S)→d̅ X sample.

Using the current world’s largest data sample of ψ(3770) decays, we present results of a search for the non-DD̅ decay ψ(3770)→K_S⁰K_L⁰. We find no signal, and obtain an upper limit of σ(e⁺e^-→ψ(3770)→K_S⁰K_L⁰)<0.07  pb at 90% confidence level (CL). Our result tests a theoretical prediction for the upper bound on B(ψ(3770)→K_S⁰K_L⁰) based on a charmonia-mixing model.

Using a sample of 3.08×10⁶ ψ(2S) decays collected at sqrt[s]=3.686  GeV with the CLEO detector at the Cornell Electron Storage Ring, we have measured the branching fractions for ψ(2S) decays to pseudoscalar pairs π⁺π^-, K⁺K^- and K_S⁰K_L⁰. We obtain B(ψ(2S)→π⁺π^-)<2.1×10^-5 (90% C.L.), B(ψ(2S)→K⁺K^-)=(6.3±0.6(stat)±0.3(syst))×10^-5, and B(ψ(2S)→K_S⁰K_L⁰)=(5.8±0.8(stat)±0.4(syst))×10^-5. The branching fractions allow extraction of the relative phase Δ=(95±15)° and strength ratio R=(2.5±0.4) of the three-gluon and one-photon amplitudes for these modes.

Using data taken with the CLEO III detector at the Cornell Electron Storage Ring, we have investigated the direct photon spectrum in the decays Υ(1S)→γgg, Υ(2S)→γgg, Υ(3S)→γgg. The latter two of these are first measurements. Our analysis procedures differ from previous ones in the following ways: (a) background estimates (primarily from π⁰ decays) are based on isospin symmetry rather than a determination of the π⁰ spectrum, which permits measurement of the Υ(2S) and Υ(3S) direct photon spectra without explicit corrections for π⁰ backgrounds from, e.g., χ_bJ states, (b) we estimate the branching fractions with a parametrized functional form (exponential) used for the background, and c) we use the high-statistics sample of Υ(2S)→ππΥ(1S) to obtain a tagged sample of Υ(1S)→γ+X events, for which there are no QED backgrounds. We determine values for the ratio of the inclusive direct photon decay rate to that of the dominant three-gluon decay Υ→ggg  (R_γ=B(ggγ)/B(ggg)) to be R_γ(1S)=(2.70±0.01±0.13±0.24)%, R_γ(2S)=(3.18±0.04±0.22±0.41)%, and R_γ(3S)=(2.72±0.06±0.32±0.37)%, where the errors shown are statistical, systematic, and theoretical model dependent, respectively. Given a value of Q², one can estimate a value for the strong coupling constant α_s(Q²) from R_γ.

From e⁺e^- collision data acquired with the CLEO detector at the Cornell Electron Storage Ring, we observe the non-DD̅ decay ψ(3770)→γχ_c1 with a statistical significance of 6.6 standard deviations, using the two-photon cascades to J/ψ and J/ψ→ℓ⁺ℓ^-. We determine σ(e⁺e^-→ψ(3770))×B(ψ(3770)→γχ_c1)=(18.0±3.3±2.5)  pb and branching fraction B(ψ(3770)→γχ_c1)=(2.8±0.5±0.4)×10^-3. We set 90% C.L. upper limits for the transition to χ_c2 (χ_c0): σ×B<5.7  pb (<282  pb) and B<0.9×10^-3 (<44×10^-3). We also determine Γ(ψ(3770)→γχ_c1)/Γ(ψ(3770)→π⁺π^-J/ψ)=1.5±0.3±0.3 (>1.0 at 90% C.L.), which bears upon the interpretation of X(3872).

Using data collected with the CLEO detector operating at the CESR e⁺e^- collider at sqrt[s]=3.97–4.26  GeV, we investigate 15 charmonium decay modes of the ψ(4040), ψ(4160), and Y(4260) resonances. We confirm, at 11σ significance, the BABAR Y(4260)→π⁺π^-J/ψ discovery, make the first observation of Y(4260)→π⁰π⁰J/ψ (5.1σ), and find the first evidence for Y(4260)→K⁺K^-J/ψ (3.7σ). We measure e⁺e^- cross sections at sqrt[s]=4.26  GeV as σ(π⁺π^-J/ψ)=58_-10⁺¹²±4  pb, σ(π⁰π⁰J/ψ)=23_-8⁺¹²±1  pb, and σ(K⁺K^-J/ψ)=9_-5⁺⁹±1  pb, in which the uncertainties are statistical and systematic, respectively. Upper limits are placed on other decay rates from all three resonances.

Using 420  pb^-1 of data collected on the Υ(5S) resonance with the CLEO III detector, we reconstruct B mesons in 25 exclusive decay channels to measure or set upper limits on the decay rate of Υ(5S) into B meson final states. We measure the inclusive B cross section to be σ(Υ(5S)→BB̅ (X))=(0.177±0.030±0.016)  nb and make the first measurements of the production rates of σ(Υ(5S)→B^*B̅ ^*)=(0.131±0.025±0.014)  nb and σ(Υ(5S)→BB̅ ^*)=(0.043±0.016±0.006)  nb, respectively. We set 90% confidence level limits of σ(Υ(5S)→BB̅ )<0.038  nb, σ(Υ(5S)→B^(*)B̅ ^(*)π)<0.055  nb and σ(Υ(5S)→BB̅ ππ)<0.024  nb. We also extract the most precise value of the B_s^* mass to date, M(B_s^*)=(5411.7±1.6±0.6)  MeV/c².

The two-photon width of χ_c2(³P₂) state of charmonium has been measured using 14.4  fb^-1 of e⁺e^- data taken at sqrt[s]=9.46–11.30  GeV with the CLEO III detector. The γγ-fusion reaction studied is e⁺e^-→e⁺e^-γγ, γγ→χ_c2→γJ/ψ→γe⁺e^-(μ⁺μ^-). We measure Γ_γγ(χ_c2)B(χ_c2→γJ/ψ)B(J/ψ→e⁺e^-+μ⁺μ^-)=13.2±1.4(stat)±1.1(syst)  eV, and obtain Γ_γγ(χ_c2)=559±57(stat)±48(syst)±36(br)  eV. This result is in excellent agreement with the result of γγ-fusion measurement by Belle and is consistent with that of the p̅ p→χ_c2→γγ measurement, when they are both reevaluated using the recent CLEO result for the radiative decay χ_c2→γJ/ψ.

We present the first experimental limits on high-q² contributions to charmless semileptonic B decays of the form expected from the weak annihilation (WA) decay mechanism. Such contributions could bias determinations of |V_ub| from inclusive measurements of B→X_ulν. Using a wide range of models based on available theoretical input we set a limit of Γ_WA/Γ_b→u<7.4% (90% confidence level) on the WA fraction, and assess the impact on previous inclusive determinations of |V_ub|.

We determine the dielectron widths of the Υ(1S), Υ(2S), and Υ(3S) resonances with better than 2% precision by integrating the cross section of e⁺e^-→Υ over the e⁺e^- center-of-mass energy. Using e⁺e^- energy scans of the Υ resonances at the Cornell Electron Storage Ring and measuring Υ production with the CLEO detector, we find dielectron widths of 1.252±0.004(σ_stat)±0.019(σ_syst)  keV, 0.581±0.004±0.009  keV, and 0.413±0.004±0.006  keV for the Υ(1S), Υ(2S), and Υ(3S), respectively.

We measure the cross section for e⁺e^-→ψ(3770)→hadrons at E_c.m.=3773  MeV to be (6.38±0.08_-0.30^+0.41)  nb using the CLEO detector at the CESR e⁺e^- collider. The difference between this and the e⁺e^-→ψ(3770)→DD̅ cross section at the same energy is found to be (-0.01±0.08_-0.30^+0.41)  nb. With the observed total cross section, we extract Γ_ee(ψ(3770))=(0.204±0.003_-0.027^+0.041)  keV. Uncertainties shown are statistical and systematic, respectively.

We observe signals for the decays ψ(3770)→XJ/ψ from data acquired with the CLEO detector operating at the CESR e⁺e^- collider with sqrt[s]=3773  MeV. We measure the following branching fractions B(ψ(3770)→XJ/ψ) and significances: (189±20±20)×10^-5 (11.6σ) for X=π⁺π^-, (80±25±16)×10^-5 (3.4σ) for X=π⁰π⁰, and (87±33±22)×10^-5 (3.5σ) for X=η, where the errors are statistical and systematic, respectively. The radiative return process e⁺e^-→γψ(2S) populates the same event sample and is used to measure Γ_ee[ψ(2S)]=(2.54±0.03±0.11)  keV.

Using data acquired with the CLEO detector at the CESR e⁺e^- collider at sqrt[s]=3.773  GeV, we measure the cross section for the radiative return process e⁺e^-→γJ/ψ, J/ψ→μ⁺μ^-, resulting in B(J/ψ→μ⁺μ^-)×Γ_ee(J/ψ)=0.3384±0.0058±0.0071  keV, Γ_ee(J/ψ)=5.68±0.11±0.13  keV, and Γ_tot(J/ψ)=95.5±2.4±2.4  keV, in which the errors are statistical and systematic, respectively. We also determine the ratio Γ_ee[ψ(2S)]/Γ_ee(J/ψ)=0.45±0.01±0.02.

Using 281  pb^-1 of data collected with the CLEO-c detector, we report on first observations and measurements of Cabibbo-suppressed decays of D mesons in the following six decay modes: π⁺π^-π⁰π⁰, π⁺π⁺π^-π^-π⁰, π⁺π⁰π⁰, π⁺π⁺π^-π⁰, ηπ⁰, and ωπ⁺π^-. Improved branching fraction measurements in eight other multipion decay modes are also presented. The measured D→ππ rates allow us to extract the ratio of isospin amplitudes A(ΔI=3/2)/A(ΔI=1/2)=0.420±0.014(stat)±0.016(syst) and the strong phase shift of δ_I=(86.4±2.8±3.3)°, which is quite large and now more precisely determined.

Using data obtained with the CLEO III detector, running at the Cornell Electron Storage Ring (CESR), we report on a new study of exclusive radiative Υ(1S) decays into the final states γπ⁺π^-, γK⁺K^-, and γpp̅ . We present branching ratio measurements for the decay modes Υ(1S)→γf₂(1270), Υ(1S)→γf₂^′(1525), and Υ(1S)→γK⁺K^-; helicity production ratios for f₂(1270) and f₂^′(1525); upper limits for the decay Υ(1S)→γf_J(2200), with f_J(2220)→π⁺π^-, K⁺K^-, pp̅ ; and an upper limit for the decay Υ(1S)→γX(1860), with X(1860)→γpp̅ .

Using data collected at the ψ(3770) resonance with the CLEO-c detector at the Cornell e⁺e^- storage ring, we present searches for 25 charmless decay modes of the ψ(3770), mostly multibody final states. No evidence for charmless decays is found.

We have searched for the di-pion transition χ_b(2P)→ππχ_b(1P) in the CLEO III sample of Υ(3S) decays in the exclusive decay chain: Υ(3S)→γχ_b(2P), χ_b(2P)→ππχ_b(1P), χ_b(1P)→γΥ(1S), Υ(1S)→ℓ⁺ℓ^-. Our studies include both π⁺π^- and π⁰π⁰, each analyzed both in fully-reconstructed events and in events with one pion undetected. We show that the null hypothesis is not substantiated. Under reasonable assumptions, we find the partial decay width to be Γ(χ_b(2P)→ππχ_b(1P))=(0.83±0.22±0.08±0.19)  keV, with the uncertainties being statistical, internal CLEO systematics, and common systematics from outside sources.