Showing papers by "F. Blanc published in 2001"

Observation of new states decaying into Lambda+(c)pi(-)pi(+).

Abstract: Using 13.7 fb(-1) of data recorded by the CLEO detector at the Cornell Electron Storage Ring, we investigate the spectrum of charmed baryons which decay into Lambda+(c)pi(-)pi(+) and are more massive than the Lambda+(c)(2625) baryon. We find evidence for two new states: one is broad and has an invariant mass roughly 480 MeV above that of the Lambda+(c) baryon; the other is narrow with an invariant mass of 596+/-1+/-2 MeV above the Lambda+(c) mass.

Dalitz analysis of the decay D0→K-π+π0

Abstract: We use data collected with the CLEO II detector to perform a high-statistics measurement of the resonant substructure in ${D}^{0}\ensuremath{\rightarrow}{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{0}$ decays. We find that the Dalitz plot is well represented by a combination of seven quasi-two-body decay channels $[{K}^{*0}{\ensuremath{\pi}}^{0},{K}^{\ensuremath{-}}\ensuremath{\rho},{K}^{*\ensuremath{-}}{\ensuremath{\pi}}^{+},{K}_{0}{(1430)}^{\ensuremath{-}}{\ensuremath{\pi}}^{+},{K}_{0}{(1430)}^{0}{\ensuremath{\pi}}^{0},{K}^{\ensuremath{-}}{\ensuremath{\rho}}^{+}(1700),$ and ${K}^{*}{(1680)}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}],$ plus a small non-resonant component. We see no evidence of a scalar $\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\kappa}}{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}$ resonance in the mass range recently reported by other groups. Using the amplitudes and phases from this analysis, we calculate an integrated $\mathrm{CP}$ asymmetry of $\ensuremath{-}0.031\ifmmode\pm\else\textpm\fi{}0.086.$

Bounds on the CP asymmetry in b→ sγ decays

Abstract: We have measured the CP asymmetry A(CP) identical with[gamma(b-->sgamma)-gammab-->sgamma)]/[gamma(b-->sgamma)+gamma(b-->sgamma)] to be A(CP) = (-0.079+/-0.108+/-0.022) (1.0+/-0.030), implying that, at 90% confidence level, A(CP) lies between -0.27 and +0.10. These limits rule out some extreme non-standard-model predictions, but are consistent with most, as well as with the standard model.

Observation of B → φK and B → φK

Abstract: We have studied two-body charmless hadronic decays of B mesons into the final states straight phiK and phiK(*). Using 9.7 million BB pairs collected with the CLEO II detector, we observe the decays B- --> phiK- and B0--> phiK(*0) with the following branching fractions: B(B--->phiK-) = (5.5(+2.1)(-1.8)+/-0.6)x10(-6) and B(B0--> phiK(*0)) = (11.5(+4.5+1.8)(-3.7-1.7))x10(-6). We also see evidence for the decays B0-->phiK0 and B---> phiK(*-). However, since the statistical significance is not overwhelming for these modes, we determine upper limits of <12.3x10(-6) and <22.5x10(-6) ( 90% confidence level), respectively.

Bounds on the CP asymmetry in like-sign dileptons from B(0)B*(0) meson decays.

Abstract: We have measured the charge asymmetry in like-sign dilepton yields from B(0)B*(0) meson decays using the CLEO detector at the Cornell Electron Storage Ring. We find a(0)(ll) identical with[N(l(+)l(+))-N(l(-)l(-))]/[N(l(+)l(+))+N(l(-)l(-))] = +0.013+/-0.050+/-0.005. We combine this result with a previous, independent measurement and obtain Re(epsilon(B))/(1+ the absolute value of epsilon(B)(2)) = +0.0035+/-0.0103+/-0.0015 (uncertainties are statistical and systematic, respectively) for the CP impurity parameter, epsilon(B).

Search for the familon via B(+/-) --> pi+/-X(0), B(+/-) --> K(+/-)X(0), and B(0) --> K(0)(S)X(0) decays.

Abstract: We have searched for the two-body decay of the B meson to a light pseudoscalar meson h = pi(+/-),K+/-,K(0)(S) and a massless neutral feebly interacting particle X(0) such as the familon, the Nambu-Goldstone boson associated with a spontaneously broken global family symmetry. We find no significant signal by analyzing a data sample containing 9.7x10(6) BBbar mesons collected with the CLEO detector at the Cornell Electron Storage Ring, and set 90% C.L. upper limits italicB(B(+/-) --> h(+/-)X(0)) = 4.9x10(-5) and italicB(B(0) --> K(0)(S)X(0)) = 5.3x10(-5). These limits correspond to a lower bound of approximately 10(8) GeV on the family symmetry breaking scale with vector coupling involving the third generation of quarks.

Study of B decays to charmonium states: B → ηcK and B → χc0K

Abstract: In a sample of 9.66x10(6)BB pairs collected with the CLEO detector we make the first observation of B decays to an eta(c) and a kaon. We measure branching fractions B(B+-->eta(c)K+) = (0.69(+0.26)(-0.21)+/-0.08+/-0.20)x10(-3) and B(B degrees -->eta(c)K degrees ) = (1.09(+0.55)(-0.42)+/-0.12+/-0.31)x10(-3), where the first error is statistical, the second is systematic, and the third is from the eta(c) branching fraction uncertainty. From these we extract the eta(c) decay constant in the factorization approximation, f(eta(c)) = 335+/-75 MeV. We also search for B decays to a chi(c0) and a kaon. No evidence for a signal is found and we set 90% C.L. upper limits: B(B+-->chi(c0)K+) chi(c0)K degrees )<5.0x10(-4).

Measurement of the relative branching fraction of Y(4S) to charged and neutral B-meson pairs

Abstract: We analyze 9.7x10(6) B_B pairs recorded with the CLEO detector to determine the production ratio of charged to neutral B-meson pairs produced at the Upsilon(4S) resonance. We measure the rates for B0-->J/psiK((*)0) and B+-->J/psiK((*)+) decays and use the world-average B-meson lifetime ratio to extract the relative widths f(+-) / f(00) = gamma(Upsilon(4S)-->B+B-) / gamma(Upsilon(4S)-->B0 B-0)) = 1.04+/-0.07(stat)+/-0.04(syst). With the assumption that f(+-)+f(00) = 1, we obtain f(00) = 0.49+/-0.02(stat)+/-0.01(syst) and f(+-) = 0.51+/-0.02(stat)+/-0.01(syst). This production ratio and its uncertainty apply to all exclusive B-meson branching fractions measured at the Upsilon(4S) resonance.

Experimental investigation of the two-photon widths of the chi(c0) and the chi(c2) mesons.

Abstract: Using $12.7{\mathrm{fb}}^{\ensuremath{-}1}$ of data collected with the CLEO detector at CESR, we observed two-photon production of the $c\overline{c}$ states ${\ensuremath{\chi}}_{c0}$ and ${\ensuremath{\chi}}_{c2}$ in their decay to ${\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$. We measured ${\ensuremath{\Gamma}}_{\ensuremath{\gamma}\ensuremath{\gamma}}({\ensuremath{\chi}}_{c})\ifmmode\times\else\texttimes\fi{}B({\ensuremath{\chi}}_{c}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}})$ to be $75\ifmmode\pm\else\textpm\fi{}13(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}8(\mathrm{syst})\mathrm{eV}$ for the ${\ensuremath{\chi}}_{c0}$ and $6.4\ifmmode\pm\else\textpm\fi{}1.8(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.8(\mathrm{syst})\mathrm{eV}$ for the ${\ensuremath{\chi}}_{c2}$, implying ${\ensuremath{\Gamma}}_{\ensuremath{\gamma}\ensuremath{\gamma}}({\ensuremath{\chi}}_{c0})\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}3.76\ifmmode\pm\else\textpm\fi{}0.65(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.41(\mathrm{syst})\ifmmode\pm\else\textpm\fi{}1.69(\mathrm{br})\mathrm{keV}$ and ${\ensuremath{\Gamma}}_{\ensuremath{\gamma}\ensuremath{\gamma}}({\ensuremath{\chi}}_{c2})\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.53\ifmmode\pm\else\textpm\fi{}0.15(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.06(\mathrm{syst})\ifmmode\pm\else\textpm\fi{}0.22(\mathrm{br})\mathrm{keV}$. Also, cancellation of dominant experimental and theoretical uncertainties permits a precise comparison of ${\ensuremath{\Gamma}}_{\ensuremath{\gamma}\ensuremath{\gamma}}({\ensuremath{\chi}}_{c0})/{\ensuremath{\Gamma}}_{\ensuremath{\gamma}\ensuremath{\gamma}}({\ensuremath{\chi}}_{c2})$, evaluated to be $7.4\ifmmode\pm\else\textpm\fi{}2.4(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.5(\mathrm{syst})\ifmmode\pm\else\textpm\fi{}0.9(\mathrm{br})$, with QCD-based predictions.

First observation of the decays B0 → D*- p̄π+ and B0 → D*-pn̄

Abstract: We report the first observation of exclusive decays of the type B-->D(*)N_NX, where N is a nucleon Using a sample of 97x10(6)B_B pairs collected with the CLEO detector operating at the Cornell Electron Storage Ring, we measure the branching fractions B(B0-->D(*-)p_p pi(+)) = (65(+13)(-12)+/-10)x10(-4) and B(B0-->D(*-)p_n) = (145(+34)(-30)+/-27)x10(-4) Antineutrons are identified by their annihilation in the CsI electromagnetic calorimeter

Study of τ decays to six pions and a neutrino

Abstract: The tau decays to six-pion final states have been studied with the CLEO detector at the Cornell Electron Storage Ring. The measured branching fractions are B(tau(-)-->2pi(-)pi(+)3pi(0)nu(tau)) = (2.2+/-0.3+/-0.4)x10(-4) and B(tau(-)-->3pi(-)2pi(+)pi(0)nu(tau)) = (1.7+/-0.2+/-0.2)x10(-4). A search for substructure in these decays shows that they are saturated by intermediate states with eta or omega mesons. We present the first observation of the decay tau(-)-->2pi(-)pi(+)omega(nu)tau and the branching fraction is measured to be (1.2+/-0.2+/-0.1)x10(-4). The measured branching fractions are in good agreement with the isospin expectations but somewhat below the conserved-vector-current predictions.

Observation of the Ωc0 charmed baryon at CLEO

Abstract: The CLEO experiment at the CESR collider has used 13.7 fb(-1) of data to search for the production of the Omega(0)(c) (css ground state) in e(+)e(-) collisions at square root of (s) approximately 10.6 GeV. The modes used to study the Omega(0)(c) are Omega(-)pi(+), Omega(-)pi(+)pi(0), Xi-K-pi(+)pi(+), Xi0K-pi(+), and Omega(-)pi(+)pi(+)pi(-). We observe a signal of 40.4+/-9.0(stat) events at a mass of 2694.6+/-2.6(stat)+/-1.9(syst) MeV/c(2), for all modes combined.

Improved Upper Limits on the Flavor-Changing Neutral Current Decays B --> Kl + l - and B --> K * (892)l + l -

Abstract: We have searched a sample of 9.6 million BBbar events for the flavor-changing neutral current decays B -> K l^+ l^- and B -> K^*(892) l^+ l^-. We subject the latter decay to the requirement that the dilepton mass exceed 0.5 GeV. There is no indication of a signal. We obtain the 90% confidence level upper limits on the branching fractions Br(B -> K l^+ l^-) K^*(892) l^+ l^-) K l^+ l^-) + 0.35 Br(B -> K^*(892) l^+ l^-) < 1.5 \times 10^{-6}. The weighted-average limit is only 50% above the Standard Model prediction.

First observation of the sigma(*+)(c) baryon and a new measurement of the sigma(*+)(c) mass.

Abstract: Using data recorded with the CLEO II and CLEO II.V detector configurations at the Cornell Electron Storage Rings, we report the first observation and mass measurement of the ${\ensuremath{\Sigma}}_{c}^{*+}$ charmed baryon, and an updated measurement of the mass of the ${\ensuremath{\Sigma}}_{c}^{+}$ baryon. We find $M({\ensuremath{\Sigma}}_{c}^{*+})\ensuremath{-}M({\ensuremath{\Lambda}}_{c}^{+})\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}(231.0\ifmmode\pm\else\textpm\fi{}1.1\ifmmode\pm\else\textpm\fi{}2.0)\phantom{\rule{0ex}{0ex}}\mathrm{MeV}$, and $M({\ensuremath{\Sigma}}_{c}^{+})\ensuremath{-}M({\ensuremath{\Lambda}}_{c}^{+})\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}(166.4\ifmmode\pm\else\textpm\fi{}0.2\ifmmode\pm\else\textpm\fi{}0.3)\phantom{\rule{0ex}{0ex}}\mathrm{MeV}$, where the errors are statistical and systematic, respectively.

Search for the familon via B± → π±X0, B± → K±X0, and B0 → Ks0X0 decays

Abstract: We have searched for the two-body decay of the B meson to a light pseudoscalar meson h = π γ , K γ , K 0 S and a massless neutral feebly interacting particle X° such as the familon, the Nambu-Goldstone boson associated witha spontaneously broken global family symmetry. We find no significant signal by analyzing a data sample containing 9.7 X 10 6 BB mesons collected with the CLEO detector at the Cornell Electron Storage Ring, and set 90% C.L. upper limits B(B γ → h γ X 0 ) = 4.9 X 10 - 5 and B(B 0 → K 0 S X 0 ) = 5.3 × 10 - 5 . These limits correspond to a lower bound of approximately 10 8 GeV on the family symmetry breaking scale with vector coupling involving the third generation of quarks.

Rate measurement of D0 → K+ π-π0 and constraints on D0 - D0̄ mixing

Abstract: We present an observation and time-integrated rate measurement of the decay D{sup 0}{yields}K{sup +}{pi}{sup -}{pi}{sup 0} produced in 9 fb{sup -1} of e{sup +}e{sup -} collisions near the {Upsilon}(4S) resonance. The signal is inconsistent with an upward fluctuation of the background by 4.9 standard deviations. We measured the time-integrated rate of D{sup 0}{yields}K{sup +}{pi}{sup -}{pi}{sup 0} normalized to the rate of {ovr D{sup 0}}{yields}K{sup +}{pi}{sup -} {pi}{sup 0} to be 0.0043{sup +0.0011}{sub -0.0010} ( stat){+-}0.0007 (syst ). This decay can be produced by doubly Cabibbo-suppressed decays or by the D{sup 0} evolving into a {ovr D{sup 0}} through mixing, followed by a Cabibbo-favored decay to K{sup +}{pi}{sup -}{pi}{sup 0}. We also found the CP asymmetry A=(9{sup +25}{sub -22})% be consistent with zero.

Search for CP violation in τ → ππ0ντ decay

Abstract: We search for CP non-conservation in the decays of tau leptons produced via $e^+ e^-$ annihilation at $\sqrt{s}\sim$ 10.6 GeV. The method uses correlated decays of pairs of tau leptons, each decaying to the $\pi \pi^0 u_{\tau}$ final state. The search is done within the framework of a model with a scalar boson exchange. In an analysis of a data sample corresponding to 12.2 million produced tau pairs collected with the CLEO detector, we find no evidence of violation of CP symmetry. We obtain a limit on the imaginary part of the coupling constant parameterizing the relative contribution of diagrams that would lead to CP violation to be $-0.046 <\Im(\Lambda) < 0.022$ at 90% C.L. This result provides a restriction on CP non-conservation in the tau lepton decays. As a cross check, we study the decay angular distribution and perform a model-independent search for a CP violation effect of a scalar exchange in single $\tau\to \pi\pi^0 u_\tau$ decays. The limit on the imaginary part of the $\tau$ scalar coupling is $-0.033 < \Im(\Lambda) < 0.089$ at 90% C.L.

Measurement of the Λc+ lifetime

Abstract: A precise measurement of the Λ c + lifetime using approximately 1340 fully reconstructed Λ c + →pK - π + and charge conjugate decays is presented. The data were accumulated by the Fermilab high energy photoproduction experiment E687. The lifetime of the Λ c + is measured to be 0.215±0.016±0.008 ps

Design and initial performance of the CLEO III silicon tracker

Abstract: CLEO III is the new experimental phase of the CLEO experiment at the CESR accelerator. Both the accelerator and the detector have recently been upgraded. A new charged particle tracking system with the addition of a ring imaging Cherenkov particle identification system has been installed. A major part of the tracking system upgrade was the construction of a new four-layer double-sided silicon tracker with 93% solid angle coverage and new readout electronics. The CLEO III upgrade was completed in February 2000 with the installation of the silicon detector. CLEO III has finished the commissioning phase and is now taking data. The design of the detector and first performance results are presented here.

First observation of B̄→D(*) ρ′-, ρ′-→ωπ-

Abstract: We report on the observation of $\overline{B}\ensuremath{\rightarrow}{D}^{*}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}$ decays. The branching ratios for ${D}^{*+}$ and ${D}^{*0}$ are $(1.72\ifmmode\pm\else\textpm\fi{}0.14\ifmmode\pm\else\textpm\fi{}0.24)%$ and $(1.80\ifmmode\pm\else\textpm\fi{}0.24\ifmmode\pm\else\textpm\fi{}0.27)%,$ respectively. Each final state has a ${D}^{*}\ensuremath{\omega}{\ensuremath{\pi}}^{\ensuremath{-}}$ component, with branching ratios $(0.29\ifmmode\pm\else\textpm\fi{}0.03\ifmmode\pm\else\textpm\fi{}0.04)%$ and $(0.45\ifmmode\pm\else\textpm\fi{}0.10\ifmmode\pm\else\textpm\fi{}0.07)%$ for the ${D}^{*+}$ and ${D}^{*0}$ modes, respectively. We also observe $\overline{B}\ensuremath{\rightarrow}D\ensuremath{\omega}{\ensuremath{\pi}}^{\ensuremath{-}}$ decays. The branching ratios for ${D}^{+}$ and ${D}^{0}$ are $(0.28\ifmmode\pm\else\textpm\fi{}0.05\ifmmode\pm\else\textpm\fi{}0.04)%$ and $(0.41\ifmmode\pm\else\textpm\fi{}0.07\ifmmode\pm\else\textpm\fi{}0.06)%,$ respectively. A spin parity analysis of the $\ensuremath{\omega}{\ensuremath{\pi}}^{\ensuremath{-}}$ system in the $D\ensuremath{\omega}{\ensuremath{\pi}}^{\ensuremath{-}}$ final state shows a preference for a wide ${1}^{\ensuremath{-}}$ resonance. A fit to the $\ensuremath{\omega}{\ensuremath{\pi}}^{\ensuremath{-}}$ mass spectrum finds a central mass of $(1349\ifmmode\pm\else\textpm\fi{}{25}_{\ensuremath{-}5}^{+10})$ MeV and width of $(547\ifmmode\pm\else\textpm\fi{}{86}_{\ensuremath{-}45}^{+46})$ MeV. We identify this object as the $\ensuremath{\rho}(1450)$ or the ${\ensuremath{\rho}}^{\ensuremath{'}}.$

Search for B → τv and B → Kvv̄

Abstract: We report results of a search for B-->tau(nu) in a sample of 9.7 x 10(6) charged B meson decays. We exclusively reconstruct the companion B decay to suppress background. We set an upper limit on the branching fraction B(B-->tau(nu)) K+/-nu(nu))<2.4 x 10(-4) at 90% confidence level.

Search for the decay B+→D*+Ks 0

Abstract: We report on a search for the decay B+ -> D*+ K0_S and its charge conjugate with the CLEO detector at the Cornell Electron Storage Ring (CESR). No candidates are found in 9.10/fb of data. The background is estimated to be 0.29 +- 0.05 leading to an upper limit BF(B+ -> D*+ K0_S) = 9.5 x 10^{-5} (90% C.L.).

Search for the decay Y(1S) → γη′

Abstract: We report on a search for the radiative decay Upsilon(1S)-->gammaeta(') in 61.3 pb(-1) of data taken with the CLEO II detector at the Cornell Electron Storage Ring. Three decay chains were investigated, all involving eta(')-->pi(+)pi(-)eta, followed by eta-->gammagamma, eta-->pi(0)pi(0)pi(0), or eta-->pi(+)pi(-)pi(0). We find no candidate events in any of the three cases and set a combined upper limit of 1.6x10(-5) at 90% C.L., significantly smaller than the previous limit. We compare our result to other radiative Upsilon decays, to radiative J/psi decays, and to theoretical predictions.

Correlated Λc+Λ̄c- production in e+e- annihilations at √s∼10.5 GeV

Abstract: Using 13.6/fb of continuum two-jet e+e- -> ccbar events collected with the CLEO detector, we have searched for baryon number correlations at the primary quark level. We have measured the likelihood for a /\c+ charmed baryon to be produced in the hemisphere opposite a /\c- relative to the likelihood for a /\c+ charmed baryon to be produced opposite an anticharmed meson Dbar; in all cases, the reconstructed hadrons must have momentum greater than 2.3 GeV/c. We find that, given a /\c- (reconstructed in five different decay modes), a /\c+ is observed in the opposite hemisphere (0.72+/-0.11)% of the time (not corrected for efficiency). By contrast, given a Dbar in one hemisphere, a /\c+ is observed in the opposite hemisphere only (0.21+/-0.02)% of the time. Normalized to the total number of either /\c- or Dbar ``tags'', it is therefore 3.52+/-0.45+/-0.42 times more likely to find a /\c+ opposite a /\c- than a Dbar meson. This enhancement is not observed in the JETSET 7.3 e+e- -> ccbar Monte Carlo simulation.