119535783
A dynamical mechanism for the hairpin diagram
SummaryBased on the nonvalence quark-antiquark and gluon constituent structure of mesons we give a reasonable dynamical mechanism which can induce the hairpin diagram without violating the well-observed OZI rule. We calculate the hairpin amplitudes of
$$D^0 \to \overline K ^0 \eta $$
 and
$$\overline K ^0 \eta '$$
 normalized by
$$D^0 \to \overline K ^0 \pi ^0 $$
 and have found that the hairpin diagram can give rise to substantial contributions to the decays where a meson with aSU(3) flavor singlet component is involved in the final state. In this scenario, we also obtain the branching ratio of
$$D^0 \to \overline K ^0 \phi $$
 as 0.55% in comparison with the experimental data of 0.83%.
120276294
Studies of heavy hadron physics
In the diquark picture, we establish Bethe-Salpeter equations for ground states of heavy baryons containing one heavy quark and two heavy quarks in the heavy quark limit, respectively. The Bethe-Salpeter equations for both heavy and light diquarks are also established. Assuming kernels to consist of a scalar confinement term and a one-gluon-exchange term we solve Bethe-Salpeter wave functions numerically in the covariant instantaneous approximation and give some applications including semileptonic and nonleptonic decay widths of heavy baryons, the average kinetic energy of the heavy quark in {Lambda}{sub Q}, {Sigma}{sub Q}{sup (*)}{yields}{Lambda}{sub Q}+{pi} decay widths, and heavy quark distribution functions. We also study possible molecular heavy bound states in the Bethe-Salpeter approach. Proof of QCD factorization for {Lambda}{sub b}{yields}{Lambda}{sub c}{pi} is presented in the framework of QCD factorization.
1763711
Electromagnetic radiation of baryons containing two heavy quarks
The two heavy quarks in a baryon which contains two heavy quarks and a light one can constitute a scalar or axial vector diquark. We study the electromagnetic radiation of such baryons: (i) ${\ensuremath{\Xi}}_{{(\mathrm{bc})}_{1}}\ensuremath{\rightarrow}{\ensuremath{\Xi}}_{{(\mathrm{bc})}_{0}}+\ensuremath{\gamma},$ (ii) ${\ensuremath{\Xi}}_{{(\mathrm{bc})}_{1}}^{*}\ensuremath{\rightarrow}{\ensuremath{\Xi}}_{{(\mathrm{bc})}_{0}}+\ensuremath{\gamma},$ (iii) ${\ensuremath{\Xi}}_{{(\mathrm{bc})}_{0}}^{**}(1/2,l=1)\ensuremath{\rightarrow}{\ensuremath{\Xi}}_{{(\mathrm{bc})}_{0}}+\ensuremath{\gamma},$ (iv) ${\ensuremath{\Xi}}_{{(\mathrm{bc})}_{0}}^{**}(3/2,l=1)\ensuremath{\rightarrow}{\ensuremath{\Xi}}_{{(\mathrm{bc})}_{0}}+\ensuremath{\gamma},$ and (v) ${\ensuremath{\Xi}}_{{(\mathrm{bc})}_{0}}^{**}(3/2,l=2)\ensuremath{\rightarrow}{\ensuremath{\Xi}}_{{(\mathrm{bc})}_{0}}+\ensuremath{\gamma},$ where ${\ensuremath{\Xi}}_{{(\mathrm{bc})}_{0(1)}},{\ensuremath{\Xi}}_{{(\mathrm{bc})}_{1}}^{*}$ are S-wave bound states of a heavy scalar or axial vector diquark and a light quark, and ${\ensuremath{\Xi}}_{{(\mathrm{bc})}_{0}}^{**}(lg~1)$ are P- or D-wave bound states of a heavy scalar diquark and a light quark. The analysis indicates that these processes can be attributed to two categories and the physical mechanisms which are responsible for them are completely distinct. Measurements can provide good judgment for the diquark structure and a better understanding of the physical picture.
1511951
Applications of the superflavor symmetry to heavy baryon-antibaryon pair production in electron-positron collision.
Baryons containing two heavy quarks and a light quark are believed to have the diquark-quark structure and the diquark is composed of two heavy quarks which is a spin-0 or spin-1 object. The superflavor symmetry can associate production of such a heavy baryon-antibaryon pair with heavy meson production. The whole scenario is presented in some detail in this work, and the prospect of observation in future experiments is discussed. {copyright} {ital 1996 The American Physical Society.}
16523443
Heavy to light baryon transition form factors.
Recently, Stech found form factor relations for heavy to light transitions based on two simple dynamical assumptions for a spectator particle. In this paper we generalize his approach to the case of baryons and find that for ${\mathrm{\ensuremath{\Lambda}}}_{\mathit{Q}}$\ensuremath{\rightarrow}\ensuremath{\Lambda} (Q=b or c) only one independent form factor remains in the limit ${\mathit{m}}_{\mathit{Q}}$\ensuremath{\rightarrow}\ensuremath{\infty}. Furthermore, combining with the model of Guo and Kroll we determine both of the two form factors for ${\mathrm{\ensuremath{\Lambda}}}_{\mathit{Q}}$\ensuremath{\rightarrow}\ensuremath{\Lambda} in the heavy quark limit. The results are applied to ${\mathrm{\ensuremath{\Lambda}}}_{\mathit{b}}$\ensuremath{\rightarrow}\ensuremath{\Lambda}+J/\ensuremath{\psi} which is not clarified both theoretically and experimentally. It is found that the branching ratio of ${\mathrm{\ensuremath{\Lambda}}}_{\mathit{b}}$\ensuremath{\rightarrow}\ensuremath{\Lambda}+J/\ensuremath{\psi} is of order ${10}^{\mathrm{\ensuremath{-}}5}$. \textcopyright{} 1996 The American Physical Society.
55378666
Analysis of chiral symmetry breaking mechanism
— The renormalization group invariant quark condensate m× is determined both from the consistent equation for quark condensate in the chiral limit and from the Schwinger-Dyson (SD) equation improved by the intermediate range QCD force singular like d(q) which is associated with the gluon condensate. The solutions of m× in these two equations are consistent. We also obtain the critical strong coupling constant a c above which chiral symmetry breaks in these two approaches. The nonperturbative kernel of the SD equation makes a c smaller and m× bigger. An intuitive picture of the condensation above a c is discussed. In addition, with the help of the Slavnov-Taylor-Ward (STW) identity we derive the equations for the nonperturbative quark propagator from the SD equation in the presence of the intermediate range force and find that the intermediate-range force is also responsible for dynamical chiral symmetry breaking.
16134313
The Leading power corrections to the structure functions
We show that when Bjorken $x_B$ is large, the leading order twist-four contributions to the structure functions can be expressed in terms of the derivatives of the normal twist-two parton distributions. Our analytical results are not only consistent with the parameterized power corrections extracted from the data, but also predict the flavor dependence of the power corrections. We also discuss the impact of our analytical results on the extraction and the flavor separation of the parton distributions at large $x$.
118936305
Multiple scattering and energy loss in semi-inclusive deeply inelastic eA scattering
We calculate the multiple scattering effect on single hadron production in semi-inclusive lepton-nucleus deeply inelastic scattering. We show that the quantum interference of multiple scattering amplitudes leads to suppression in hadron productions. At the leading power in medium length, the suppression can be approximately expressed in terms of a shift in $z$ of the fragmentation function $D(z)$, and could be therefore interpreted as the collisional energy loss. We compare our calculation with existing experimental data. We also discuss the effect of quark mass on the suppression. Our approach can be extended to other observables in hadronic collisions.
14098391
Probing quark-gluon correlation functions
We review the applicability of the QCD factorization theorem to multiple scattering in deeply inelastic lepton-nucleus scattering. We show why an A{sup 1/3}-type nuclear enhancement can be calculated consistently in perturbative QCD. We derive the transverse momentum broadening of the leading pions in deeply inelastic lepton-nucleus collisions. We argue that the measurement of such transverse momentum broadening can provide direct information on the multiple-parton correlation functions inside a nucleus. We also estimate the numerical values of the broadening at different values of x{sub B} and Q{sup 2}. (c) 2000 The American Physical Society.
19032960
Transverse momentum broadening due to the multiple scattering
Using the Drell-Yan process in hadron-nucleus collisions and deeply inelastic lepton-nucleus scattering (DIS) as examples, I show that the transverse momentum broadening can be expressed in terms of four-parton correlation functions. I argue that jet broadening in DIS provide an excellent measurement of the four-parton correlation functions and a test of QCD treatment of the multiple scattering.
12485364
Jet broadening in deeply inelastic scattering
In deeply inelastic lepton-nucleus scattering (DIS), the average jet transverse momentum is broadened because of the multiple scattering in the nuclear medium. The size of jet broadening is proportional to the multi-parton correlation functions inside nuclei. We show that at leading order, jet broadening in DIS and nulcear enhancement in di-jet momentum imbalance and Drell-Yan $ $ share the same four-parton correlation functions. We argue that jet broadening in DIS provide an indenpendent measurement of the four-parton correlation functions and a test of QCD treatment of multiple scattering.