Target mass corrections to proton spin structure functions and quark–hadron duality

AbstractTarget mass corrections to proton spin structure functions in deep inelastic scattering region are analysed. Moreover, Bloom–Gilman quark–hadron dualities of proton spin structure functions g1 and g2, in inelastic resonance region, are studied. The onsets of the dualities are discussed

Long-distant contribution and χc1\chi_{c1} radiative decays to light vector meson

The discrepancy between the PQCD calculation and the CLEO data for $\chi_{c1}\to \gamma V$ ($V=\rho^0,\,\omega,\,\phi$) stimulates our interest in exploring extra mechanism of $\chi_{c1}$ decay. In this work, we apply an important non-perturbative QCD effect, i.e., hadronic loop mechanism, to study $\chi_{c1}\to \gamma V$ radiative decay. Our numerical result shows that the theoretical results including the hadronic loop contribution and the PQCD calculation of $\chi_{c1}\to \gamma V$ are consistent with the corresponding CLEO data of $\chi_{c1}\to \gamma V$. We expect further experimental measurement of $\chi_{c1}\to \gamma V$ at BES-III, which will be helpful to test the hadronic loop effect on $\chi_{c1}$ decay.Comment: 7 pages, 2 figures. Accepted for publication in Eur. Phys. J.

Target mass corrections and twist-3 in the nucleon spin structure functions

The Nachtmann moment is employed to study the contribution of twist-3 operator to the nucleon spin structure functions. Target mass corrections to the Cornwall-Norton moments of the spin structure functions $g_{1,2}$ are discussed. It is found that the corrections play a sizeable role to the contribution of the twist-3 $\tilde d_2$ extracted from the Cornwall-Norton moments.Comment: 11 pages, 1 figure

Modeling quark-hadron duality for relativistic, confined fermions

We discuss a model for the study of quark-hadron duality in inclusive electron scattering based on solving the Dirac equation numerically for a scalar confining linear potential and a vector color Coulomb potential. We qualitatively reproduce the features of quark-hadron duality for all potentials considered, and discuss similarities and differences to previous models that simplified the situation by treating either the quarks or all particles as scalars. We discuss the scaling results for PWIA and FSI, and the approach to scaling using the analog of the Callan-Gross relation for y-scaling.Comment: 38 pages, 21 figure

Electromagnetic nucleon-delta transition in the perturbative chiral quark model

We apply the perturbative chiral quark model to the gamma N -> Delta transition. The four momentum dependence of the respective transverse helicity amplitudes A(1/2) and A(3/2) is determined at one loop in the pseudoscalar Goldstone boson fluctuations. Inclusion of excited states in the quark propagator is shown to result in a reasonable description of the experimental values for the helicity amplitudes at the real photon point.Comment: 25 page

Search for Invisible Decays of η\eta and η′\eta^\prime in J/ψ→ϕηJ/\psi \to \phi\eta and ϕη′\phi \eta^\prime

Using a data sample of $58\times 10^6$ $J/\psi$ decays collected with the BES II detector at the BEPC, searches for invisible decays of $\eta$ and $\eta^\prime$ in $J/\psi$ to $\phi\eta$ and $\phi\eta^\prime$ are performed. The $\phi$ signals, which are reconstructed in $K^+K^-$ final states, are used to tag the $\eta$ and $\eta^\prime$ decays. No signals are found for the invisible decays of either $\eta$ or $\eta^\prime$, and upper limits at the 90% confidence level are determined to be $1.65 \times 10^{-3}$ for the ratio $\frac{B(\eta\to \text{invisible})}{B(\eta\to\gamma\gamma)}$ and $6.69\times 10^{-2}$ for $\frac{B(\eta^\prime\to \text{invisible})}{B(\eta^\prime\to\gamma\gamma)}$. These are the first searches for $\eta$ and $\eta^\prime$ decays into invisible final states.Comment: 5 pages, 4 figures; Added references, Corrected typo

Observation of Two New N* Peaks in J/psi -> ppi−nˉp pi^- \bar n and pˉπ+n\bar p\pi^+n Decays

The $\pi N$ system in decays of $J/\psi\to\bar NN\pi$ is limited to be isospin 1/2 by isospin conservation. This provides a big advantage in studying $N^*\to \pi N$ compared with $\pi N$ and $\gamma N$ experiments which mix isospin 1/2 and 3/2 for the $\pi N$ system. Using 58 million $J/\psi$ decays collected with the Beijing Electron Positron Collider, more than 100 thousand $J/\psi \to p \pi^- \bar n + c.c.$ events are obtained. Besides two well known $N^*$ peaks at 1500 MeV and 1670 MeV, there are two new, clear $N^*$ peaks in the $p\pi$ invariant mass spectrum around 1360 MeV and 2030 MeV. They are the first direct observation of the $N^*(1440)$ peak and a long-sought "missing" $N^*$ peak above 2 GeV in the $\pi N$ invariant mass spectrum. A simple Breit-Wigner fit gives the mass and width for the $N^*(1440)$ peak as $1358\pm 6 \pm 16$ MeV and $179\pm 26\pm 50$ MeV, and for the new $N^*$ peak above 2 GeV as $2068\pm 3^{+15}_{-40}$ MeV and $165\pm 14\pm 40$ MeV, respectively

Dynamically generated resonances from the vector octet-baryon decuplet interaction

We study the interaction of the octet of vector mesons with the decuplet of baryons using Lagrangians of the hidden gauge theory for vector interactions. The unitary amplitudes in coupled channels develop poles that can be associated with some known baryonic resonances, while there are predictions for new ones at the energy frontier of the experimental research. The work offers guidelines on how to search for these resonances

Octet magnetic moments and the Coleman-Glashow sum rule violation in the chiral quark model

Baryon octet magnetic moments when calculated within the chiral quark model, incorporating the orbital angular momentum as well as the quark sea contribution through the Cheng-Li mechanism, not only show improvement over the non relativistic quark model results but also gives a non zero value for the right hand side of Coleman-Glashow sum rule. When effects due to spin-spin forces between constituent quarks as well as `mass adjustments' due to confinement are added, it leads to an excellent fit for the case of p, \Sigma^+, \Xi^o and violation of Coleman-Glashow sum rule, whereas in almost all the other cases the results are within 5% of the data.Comment: 5 RevTeX pages, accepted for publication in PRD(Rapid Communication

Measurements of J/psi Decays into 2(pi+pi-)eta and 3(pi+pi-)eta

Based on a sample of 5.8X 10^7 J/psi events taken with the BESII detector, the branching fractions of J/psi--> 2(pi+pi-)eta and J/psi-->3(pi+pi-)eta are measured for the first time to be (2.26+-0.08+-0.27)X10^{-3} and (7.24+-0.96+-1.11)X10^{-4}, respectively.Comment: 11 pages, 6 figure