CLEO Data Research Articles

Photon-pion transition form factor at high photon virtualities within the nonlocal chiral quark model

Recently, the BABAR collaboration reported the measurements of the photon-pion transition form factor Fπγγ*(Q2), which are in strong contradiction to the predictions of the standard factorization approach to perturbative QCD. In the present work, based on a nonperturbative approach to the QCD vacuum and on rather universal assumptions, we show that there exist two asymptotic regimes for the pion transition form factor. One regime with the asymptotic behavior Fπγ*γ(Q2) ∼ 1/Q2 corresponds to the result of the standard QCD factorization approach, while other violates the standard factorization and leads to asymptotic behavior as Fπγ*γ(Q2) ∼ ln(Q2)/Q2. Furthermore, considering specific nonlocal chiral quark models, we find the region of parameters, where the existing CELLO, CLEO and BABAR data for the pion transition form factor are successfully described.

Long-distant contribution and χ c1 radiative decays to light vector meson

The discrepancy between the PQCD calculation and the CLEO data for χ c1→γ V (V=ρ 0, ω, φ) stimulates our interest in exploring other mechanisms of χ c1 decay. In this work, we apply an important non-perturbative QCD effect, i.e., the hadronic loop mechanism, to study χ c1→γ V radiative decay. Our numerical result shows that the theoretical results including the hadronic loop contribution and the PQCD calculation of χ c1→γ V are consistent with the corresponding CLEO data of χ c1→γ V. We expect further experimental measurement of χ c1→γ V, which will be helpful to test the hadronic loop effect on χ c1 decay.

Lepton energy moments in semileptonic charm decays

We search for signals of Weak Annihilation in inclusive semileptonic D decays. We consider both the widths and the lepton energy moments, which are quite sensitive probes. Our analysis of Cleo data shows no clear evidence of Weak Annihilation, and allows us to put bounds on their relevance in charmless B semileptonic decays.

A global treatment of VMD physics up to the φ: II. τ decay and hadronic contributions to g−2

Relying on the Hidden Local Symmetry (HLS) model equipped with a mechanism breaking the U(3)/SU(3)/SU(2) symmetries and generating a dynamical vector meson mixing, it has been shown that a global fit successfully describes the cross sections for the e + e −→π + π −, e + e −→(π 0/η)γ and e + e −→π 0 π + π − annihilation channels. One extends this global fit in order to include also the dipion spectra from the τ decay, taking into account all reported information on their statistical and systematic errors. A model accounting for lineshape distortions of the ρ ± spectrum relative to ρ 0 is also examined when analyzing the τ data behavior within the global fit framework. One shows that a successful account for e + e − annihilation data and τ spectra can be simultaneously reached. Then, issues related with non-perturbative hadronic contributions to the muon g−2 are examined in details. It is shown that all e + e − data considered together allow for improved and motivated estimates for the a μ (π + π −), the π + π − loop contribution to the muon g−2; for instance, integrated between 0.630 and 0.958 GeV, we find a μ (π + π −)=359.62±1.62 (in units of 10−10), a 40% improvement of the current uncertainty. The effects of the various τ samples in the context of a global fit procedure leads to conclude that different lineshape distortions are revealed by the ALEPH, BELLE and CLEO data samples. Relying on global fits to the data quoted above, one also provides motivated estimates of the π + π −, π 0 γ, η γ and π 0 π + π − contributions to a μ up to 1 GeV with the smallest possible uncertainties. These estimates are based on various global fit configurations, each yielding a good probability.

Two-loop contribution to the pion transition form factor vs. experimental data

We present predictions for the pion-photon transition form factor, which is derived with the help of light-cone sum rules and including the main part of the NNLO radiative corrections. We show that, when the Bakulev-Mikhailov-Stefanis (BMS) pion distribution amplitude is used, the obtained predictions agree well with the CELLO and the CLEO data. We found that no model distribution amplitude can reproduce the observed Q2 growth of the new BaBar data, though the BMS model complies with several BaBar data points.

Dielectron widths of the S-, D-vector bottomonium states

The dielectron widths of Y(nS)(n = 1, …, 7) and vector decay constants are calculated using the relativistic string Hamiltonian with a universal interaction. For Y(nS) (n = 1, 2, 3) the dielectron widths and their ratios are obtained in full agreement with the latest CLEO data. For Y(10580) and Y(11020) a good agreement with experiment is reached only if the 4S-3D mixing (with a mixing angle θ = 27°± 4°) and 6S-5D mixing (with θ = 40°±5°) are taken into account. The possibility to observe higher “mixed D-wave” resonances, \( \tilde \Upsilon \)(n 3 D 1) with n = 3, 4, 5 is discussed. In particular, \( \tilde \Upsilon \)(≈11120), originating from the pure 53 D 1 state, can acquire a rather large dielectron width, ∼130 eV, so that this resonance may become manifest in the e + e − experiments. On the contrary, the widths of pure D-wave states are very small, Γ ee (n 3 D 1)≤ 2 eV.

Constraining light bosons with radiativeΥ(1S)decays

Light bosons can be found in large classes of theories beyond the standard model. These light bosons may not be ruled out by current experiments and, indeed, may even provide an explanation for some anomalous experimental results. The radiative decays of quarkonium ($c\overline{c}$, $b\overline{b}$) states offer a promising opportunity to investigate such light bosons. Specifically, we investigate the reach that current CLEO data can have on models with light scalar and pseudoscalar bosons.

Signatures of extra dimensions from upsilon decays with a light gaugephobic Higgs boson

We explore non-standard Higgs phenomenology in the gaugephobic Higgs model in which the Higgs can be lighter than the usually quoted current experimental bound. The Higgs propagates in the bulk of a 5D space–time and Electroweak Symmetry Breaking occurs by a combination of boundary conditions in the extra dimension and an elementary Higgs. The Higgs can thus have a significantly suppressed coupling to the other Standard Model fields. A large enough suppression can be found to escape all limits and allow for a Higgs of any mass, which would be associated with the discovery of W′ and Z′ Kaluza–Klein resonances at the LHC. The Higgs can be precisely discovered at B-factories while the LHC would be insensitive to it due to high backgrounds. In this Letter we study the Higgs discovery mode in ϒ(3S), ϒ(2S), and ϒ(1S) decays, and the model parameter space that will be probed by BaBar, Belle, and CLEO data. In the absence of an early discovery of a heavy Higgs at the LHC, A Super-B factory would be an excellent option to further probe this region.

HIGHER TWIST EFFECTS IN PHOTON–PHOTON COLLISIONS

In this article, we investigate the contribution of the high twist Feynman diagrams to the large-pT single pseudoscalar and vector mesons inclusive production cross section in two-photon collisions and we present the general formulae for the high and leading twist differential cross sections. The pion wave function where two non-trivial Gegenbauer coefficients a2 and a4 have been extracted from the CLEO data, Braun–Filyanov pion wave function, the asymptotic and the Chernyak–Zhitnitsky wave functions are all used in the calculations. For ρ-meson we used the Ball–Braun wave function. The results of the calculations reveal that the high twist cross sections, the ratio R, the dependence transverse momentum pT and the rapidity y of meson in the Φ CLEO (x, Q2) wave function case is very close to the Φ asy (x) asymptotic wave function case. It is shown that the high twist contribution to the cross section depends on the choice of the meson wave functions.

A COMPREHENSIVE ANALYSIS OF THE PION–PHOTON TRANSITION FORM FACTOR IN THE LEADING ORDER APPROXIMATION

We perform a comprehensive analysis of the pion–photon transition form factor Fπγ(Q2) involving the transverse momentum corrections in the leading order approximation with the present CLEO experimental data, in which the contributions beyond the leading Fock state have been taken into consideration. As is well known, the leading Fock-state contribution dominates of Fπγ(Q2) at large momentum transfer (Q2) region. One should include the contributions beyond the leading Fock state in small Q2 region. In this paper, we construct a phenomenological expression to estimate the contributions beyond the leading Fock state based on its asymptotic behavior at Q2→0. Our present theoretical results agree well with the experimental data in the whole Q2 region. Then, we extract some useful information of the pionic leading twist-2 distribution amplitude (DA) by comparing our results of Fπγ(Q2) with the CLEO data. By taking best fit, we have the distribution amplitude moments, [Formula: see text] and all of higher moments, which are closed to the asymptotic-like behavior of the pion wave function.

Rare decayπ0→e+e−: Theory confronts KTeV data

Within the dispersive approach to the amplitude of the rare decay ${\ensuremath{\pi}}^{0}\ensuremath{\rightarrow}{e}^{+}{e}^{\ensuremath{-}}$ the nontrivial dynamics is contained only in the subtraction constant. We express this constant, in the leading order in $({m}_{e}/\ensuremath{\Lambda}{)}^{2}$ perturbative series, in terms of the inverse moment of the pion transition form factor given in symmetric kinematics. By using the CELLO and CLEO data on the pion transition form factor given in asymmetric kinematics, the lower bound of the decay branching ratio is found. The restrictions following from QCD allow us to make a quantitative prediction for the branching $B({\ensuremath{\pi}}^{0}\ensuremath{\rightarrow}{e}^{+}{e}^{\ensuremath{-}})=(6.2\ifmmode\pm\else\textpm\fi{}0.1)\ifmmode\cdot\else\textperiodcentered\fi{}{10}^{\ensuremath{-}8}$ which is $3\ensuremath{\sigma}$ below the recent KTeV measurement. We confirm our prediction by using the quark models and phenomenological approaches based on the vector meson dominance. The decays $\ensuremath{\eta}\ensuremath{\rightarrow}{l}^{+}{l}^{\ensuremath{-}}$ are also discussed.

Publisher’s Note: Observation of a narrow resonance of mass2.46 GeV/c2decaying toDs*+π0and confirmation of theDsJ*(2317)state [Phys. Rev. D68, 032002 (2003)

Using 13.5 inverse fb of e+e- annihilation data collected with the CLEO II detector we have observed a narrow resonance in the Ds*+pi0 final state, with a mass near 2.46 GeV. The search for such a state was motivated by the recent discovery by the BaBar Collaboration of a narrow state at 2.32 GeV, the DsJ*(2317)+ that decays to Ds+pi0. Reconstructing the Ds+pi0 and Ds*+pi0 final states in CLEO data, we observe peaks in both of the corresponding reconstructed mass difference distributions, dM(Dspi0)=M(Dspi0)-M(Ds) and dM(Ds*pi0)=M(Ds*pi0)-M(Ds*), both of them at values near 350 MeV. We interpret these peaks as signatures of two distinct states, the DsJ*(2317)+ plus a new state, designated as the DsJ(2463)+. Because of the similar dM values, each of these states represents a source of background for the other if photons are lost, ignored or added. A quantitative accounting of these reflections confirms that both states exist. We have measured the mean mass differences <dM(Dspi0)> = 350.0 +/- 1.2 [stat] +/- 1.0 [syst] MeV for the DsJ*(2317) state, and <dM(Ds*pi0)> = 351.2 +/- 1.7 [stat] +/- 1.0 [syst] MeV for the new DsJ(2463)+ state. We have also searched, but find no evidence, for decays of the two states via the channels Ds*+gamma, Ds+gamma, and Ds+pi+pi-. The observations of the two states at 2.32 and 2.46 GeV, in the Ds+pi0 and Ds*+pi0 decay channels respectively, are consistent with their interpretations as (c anti-strange) mesons with orbital angular momentum L=1, and spin-parities of 0+ and 1+.

PION QUARK STRUCTURE IN QCD

We describe the present status of the pion distribution amplitude as it originated from two sources: (i) a nonperturbative approach, based on QCD sum rules with nonlocal condensates and (ii) a NLO QCD analysis of the CLEO data on Fγγ*π(Q2), supplemented by the recent high-precision lattice calculations of the second moment of the pion distribution amplitude.

Antideuteron production inΥ(nS)decays and the nearby continuum

Using CLEO data, we study the production of the anti-deuteron, d-bar, in Upsilon(nS) resonance decays and the nearby continuum. The branching ratios obtained are B^dir(Upsilon(1S) --> d-bar X) = (3.36 +- 0.23 +- 0.25) x 10^-5, B(Upsilon(1S) --> d-bar X) = (2.86 +- 0.19 +- 0.21) x 10^-5, and B(Upsilon(2S) --> d-bar X) = (3.37 +- 0.50 +- 0.25) x 10^-5, where the `dir' superscript indicates that decays produced via re-annihilation of the b bbar pair to a gamma* are removed from both the signal and the normalizing number of Upsilon(1S) decays in order to isolate direct decays of the Upsilon(1S) to ggg, gg gamma. Upper limits at 90% CL are given for B(Upsilon(4S) --> d-bar X) < 1.3 x 10^-5, and continuum production \sigma(e^+e^- --> d-bar X) < 0.031 pb. The Upsilon(2S) data is also used to extract a limit on chi_bJ --> d-bar X. The results indicate enhanced deuteron production in ggg, gg gamma hadronization compared to gamma* --> q qbar. Baryon number compensation is also investigated with the large Upsilon(1S) --> d-bar X sample.

Leading-twist pion and kaon distribution amplitudes in the gauge-invariant nonlocal chiral quark model from the instanton vacuum

We investigate the leading-twist light-cone distribution amplitudes for the pion and kaon based on the gauge-invariant nonlocal chiral quark model from the instanton vacuum in the presence of external axial-vector currents. We find that the nonlocal contribution from the gauge invariance has much effects on the pion distribution amplitudes, while it changes mildly the kaon ones. We also study the Gegenbauer moments of the distribution amplitudes and compare them with the empirical analysis of the CLEO data.

HIGHER TWIST EFFECTS IN PROTON-PROTON COLLISIONS

In this article, we investigate the contribution of the high twist Feynman diagrams to the large-pT pion production cross section in proton-proton collisions and we present the general formulae for the high and leading twist differential cross sections. The pion wave function where two non-trivial Gegenbauer coefficients a2 and a4 have been extracted from the CLEO data, two other pion model wave functions, P2, P3, the asymptotic and the Chernyak-Zhitnitsky wave functions are used in the calculations. The results of all the calculations reveal that the high twist cross sections, the ratios R, r, the dependence transverse momentum pT and the rapidity y of pion in the Φ CLEO (x,Q2) wave function case is very close to the Φ asy (x) asymptotic wave function case. It is shown that the high twist contribution to the cross section depends on the choice of the meson wave functions.

A study of heavy flavoured meson fragmentation functions ine+e−annihilation

We compare QCD theoretical predictions for heavy flavoured mesons fragmentation spectra in e+ e- annihilation with data from CLEO, BELLE and LEP. We include several effects in our calculation: next-to-leading order initial conditions, evolution and coefficient functions. Soft-gluon effects are resummed at next-to-leading-log accuracy. A matching condition for the crossing of the bottom threshold in evolution is also implemented at next-to-leading order accuracy. Important initial-state electromagnetic radiation effects in the CLEO and BELLE data are accounted for. We find that, with reasonably simple choices of a non-perturbative correction to the fixed-order initial condition for the evolution, the data from CLEO and BELLE can be fitted with remarkable accuracy. The fitted fragmentation function, when evolved to LEP energies, does not however represent fairly the D* fragmentation spectrum measured by ALEPH. Large non-perturbative corrections to the coefficient functions of the meson spectrum are needed in order to reconcile CLEO/BELLE and ALEPH results. Non-perturbative parameters extracted from the fits to e+ e- fragmentation data for D/D* and B mesons are tabulated. They can be employed in the theoretical predictions for the production of charmed and bottomed mesons in hadron-hadron, photon-hadron and photon-photon collisions.

Radiative Decays and the Nature of Heavy Quarkonia

We argue that the photon spectra in radiative decays of various heavy quarkonium states provide important information on their nature. If two of these states are in the strong coupling regime, we are able to produce a parameter-free model-independent formula, which holds at next-to-leading order and includes both direct and fragmentation contributions. When the formula is checked against recent CLEO data it favors Y(2S) and Y(3S) in the strong coupling regime and disfavors Y(1S) in it.

Pion form factor analysis using NLO analytic perturbation theory

I present results for the pion's electromagnetic form factor in the spacelike region, which implement the most advanced perturbative information currently available for this observable in conjunction with a pion distribution amplitude that agrees with the CLEO data on the pion-photon transition form factor at the 1σ level. I show that using for the running strong coupling and its powers their analytic versions in the sense of Shirkov and Solovtsov, the obtained predictions become insensitive to the renormalization scheme and scale setting adopted. Joining the hard contribution with the soft part on account of local duality and respecting the Ward identity at Q 2 = 0, the agreement with the available experimental data, including expectations from planned experiments at JLab, is remarkable both in trend and magnitude. I also comment on Sudakov resummation within the analytic approach.

Impact of the higher twist effects on theγγ*→π0transition form factor

We reanalyze the $\ensuremath{\gamma}{\ensuremath{\gamma}}^{*}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}$ transition form factor ${F}_{\ensuremath{\pi}\ensuremath{\gamma}}({Q}^{2})$ within the QCD light-cone sum rules method with the twist-4 accuracy. In computations, the pion leading twist distribution amplitude (DA) with two nonasymptotic terms and the renormalon method-inspired twist-4 DAs are used. The latters allow us to estimate the impact of effects due to higher conformal spin components in the pion twist-4 DAs on the form factor ${F}_{\ensuremath{\pi}\ensuremath{\gamma}}({Q}^{2})$. Obtained theoretical predictions are employed to deduce constraints on the pion DAs from CELLO and CLEO data.