3,186 research outputs found
Phase Difference Between the Electromagnetic and Strong Amplitudes for psi(2S) and J/psi Decays into Pairs of Pseudoscalar Mesons
Using the data for 24.5x10^6 psi(2S) produced in e^+e^- annihilations at
sqrt{s}=3686 MeV at the CESR-c e^+e^- collider and 8.6x10^6 J/psi produced in
the decay psi(2S)->pi^+pi^-J/psi, the branching fractions for psi(2S) and J/psi
decays to pairs of pseudoscalar mesons, pi^+pi^-, K^+K^-, and K_S K_L, have
been measured using the CLEO-c detector. We obtain branching fractions
Br(psi(2S)->pi^+pi^-)=(7.6+-2.5+-0.6)x10^-6,
Br(psi(2S)->K^+K^-)=(74.8+-2.3+-3.9)x10^-6, Br(psi(2S)->K_S
K_L)=(52.8+-2.5+-3.4)x10^-6, and Br(J/psi->pi^+pi^-)=(1.47+-0.13+-0.13)x10^-4,
Br(J/psi->K^+K^-)=(2.86+-0.09+-0.19)x10^-4, Br(J/psi+-K_S
K_L)=(2.62+-0.15+-0.14)x10^-4, where the first errors are statistical and the
second errors are systematic. The phase differences between the amplitudes for
electromagnetic and strong decays of psi(2S) and J/psi to 0^{-+} pseudoscalar
pairs are determined by a Monte Carlo method to be
\delta(psi(2S)_{PP}=(110.5^{+16.0}_{-9.5})^o and
\delta(J/psi)_{PP}=(73.5^{+5.0}_{-4.5})^o. The difference between the two is
\Delta\delta = \delta(psi(2S))_{PP}-\delta(J/psi)_{PP}
=(37.0^{+16.5}_{-10.5})^o.Comment: 16 pages, 5 figures, submitted to PR
Phonon downconversion to suppress correlated errors in superconducting qubits
Quantum error correction can preserve quantum information in the presence of
local errors, but correlated errors are fatal. For superconducting qubits,
high-energy particle impacts from background radioactivity produce energetic
phonons that travel throughout the substrate and create excitations above the
superconducting ground state, known as quasiparticles, which can poison all
qubits on the chip. We use normal metal reservoirs on the chip back side to
downconvert phonons to low energies where they can no longer poison qubits. We
introduce a pump-probe scheme involving controlled injection of pair-breaking
phonons into the qubit chips. We examine quasiparticle poisoning on chips with
and without back-side metallization and demonstrate a reduction in the flux of
pair-breaking phonons by over a factor of 20. We use a Ramsey interferometer
scheme to simultaneously monitor quasiparticle parity on three qubits for each
chip and observe a two-order of magnitude reduction in correlated poisoning due
to background radiation.Comment: 24 pages, 17 figures, 5 table
Threshold effects in excited charmed baryon decays
Motivated by recent results on charmed baryons from CLEO and FOCUS, we
reexamine the couplings of the orbitally excited charmed baryons. Due to its
proximity to the [Sigma_c pi] threshold, the strong decays of the
Lambda_c(2593) are sensitive to finite width effects. This distorts the shape
of the invariant mass spectrum in Lambda_{c1}-> Lambda_c pi^+pi^- from a simple
Breit-Wigner resonance, which has implications for the experimental extraction
of the Lambda_c(2593) mass and couplings. We perform a fit to unpublished CLEO
data which gives M(Lambda_c(2593)) - M(Lambda_c) = 305.6 +- 0.3 MeV and h2^2 =
0.24^{+0.23}_{-0.11}, with h2 the Lambda_{c1}-> Sigma_c pi strong coupling in
the chiral Lagrangian. We also comment on the new orbitally excited states
recently observed by CLEO.Comment: 9 pages, 3 figure
Studies of the decays D^0 \rightarrow K_S^0K^-\pi^+ and D^0 \rightarrow K_S^0K^+\pi^-
The first measurements of the coherence factor R_{K_S^0K\pi} and the average
strong--phase difference \delta^{K_S^0K\pi} in D^0 \to K_S^0 K^\mp\pi^\pm
decays are reported. These parameters can be used to improve the determination
of the unitary triangle angle \gamma\ in B^- \rightarrow
decays, where is either a D^0 or a D^0-bar meson decaying to
the same final state, and also in studies of charm mixing. The measurements of
the coherence factor and strong-phase difference are made using
quantum-correlated, fully-reconstructed D^0D^0-bar pairs produced in e^+e^-
collisions at the \psi(3770) resonance. The measured values are R_{K_S^0K\pi} =
0.70 \pm 0.08 and \delta^{K_S^0K\pi} = (0.1 \pm 15.7) for an
unrestricted kinematic region and R_{K*K} = 0.94 \pm 0.12 and \delta^{K*K} =
(-16.6 \pm 18.4) for a region where the combined K_S^0 \pi^\pm
invariant mass is within 100 MeV/c^2 of the K^{*}(892)^\pm mass. These results
indicate a significant level of coherence in the decay. In addition, isobar
models are presented for the two decays, which show the dominance of the
K^*(892)^\pm resonance. The branching ratio {B}(D^0 \rightarrow
K_S^0K^+\pi^-)/{B}(D^0 \rightarrow K_S^0K^-\pi^+) is determined to be 0.592 \pm
0.044 (stat.) \pm 0.018 (syst.), which is more precise than previous
measurements.Comment: 38 pages. Version 3 updated to include the erratum information.
Errors corrected in Eqs (25), (26), 28). Fit results updated accordingly, and
external inputs updated to latest best known values. Typo corrected in Eq(3)-
no other consequence
Observation of the Dalitz Decay
Using 586 of collision data acquired at
GeV with the CLEO-c detector at the Cornell Electron Storage
Ring, we report the first observation of
with a significance of . The ratio of branching fractions
\calB(D_{s}^{*+} \to D_{s}^{+} e^{+} e^{-}) / \calB(D_{s}^{*+} \to D_{s}^{+}
\gamma) is measured to be , which is consistent with theoretical expectations
Search for rare and forbidden decays of charm and charmed-strange mesons to final states h^+- e^-+ e^+
We have searched for flavor-changing neutral current decays and
lepton-number-violating decays of D^+ and D^+_s mesons to final states of the
form h^+- e^-+ e^+, where h is either \pi or K. We use the complete samples of
CLEO-c open-charm data, corresponding to integrated luminosities of 818 pb^-1
at the center-of-mass energy E_CM = 3.774 GeV containing 2.4 x 10^6 D^+D^-
pairs and 602 pb^-1 at E_CM = 4.170 GeV containing 0.6 x 10^6 D^*+-_s D^-+_s
pairs. No signal is observed in any channel, and we obtain 90% confidence level
upper limits on branching fractions B(D^+ --> \pi^+ e^+ e^-) < 5.9 x 10^-6,
B(D^+ --> \pi^- e^+ e^+) K^+ e^+ e^-) < 3.0 x 10^-6,
B(D^+ --> K^- e^+ e^+) \pi^+ e^+ e^-) < 2.2 x 10^-5,
B(D^+_s --> \pi^- e^+ e^+) K^+ e^+ e^-) < 5.2 x
10^-5, and B(D^+_s --> K^- e^+ e^+) < 1.7 x 10^-5.Comment: 9 pages, available through http://www.lns.cornell.edu/public/CLNS
Branching fractions for Y(3S) -> pi^0 h_b and psi(2S) -> pi^0 h_c
Using e^+e^- collision data corresponding to 5.88M Y(3S) [25.9M psi(2S)]
decays and acquired by the CLEO III [CLEO-c] detectors operating at CESR, we
study the single-pion transitions from Y(3S) [psi(2S)] to the respective
spin-singlet states h_{b[c]}. Utilizing only the momentum of suitably selected
transition-pi^0 candidates, we obtain the upper limit B(Y(3S) -> pi^0 h_b) <
1.2\times 10^{-3} at 90% confidence level, and measure B(psi(2S) -> pi^0 h_c) =
(9.0+-1.5+-1.3)\times 10^{-4}. Signal sensitivities are enhanced by excluding
very asymmetric pi^0 -> gamma gamma candidates.Comment: 12 pages 4 figures, version published in Physical Review
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