7506859
Light quark dependence of the Isgur-Wise function from QCD sum rules.
We study the light quark dependence of the Isgur-Wise function for ${\mathit{B}}_{\mathit{a}}$\ensuremath{\rightarrow}${\mathit{D}}_{\mathit{a}}$ and ${\mathit{B}}_{\mathit{a}}$\ensuremath{\rightarrow}${\mathit{D}}_{\mathit{a}}^{\mathrm{*}}$ in the framework of QCD sum rules. At zero recoil all the Isgur-Wise functions are equal, as required by heavy quark symmetry, and at nonzero recoil the Isgur-Wise function for ${\mathit{B}}_{\mathit{s}}$ decay falls faster than that for ${\mathit{B}}_{\mathit{u},}$d decay, which is just contrary to the recent prediction of the heavy meson chiral perturbation theory. As a by-product we also estimate SU(3)-breaking effects in the mass and the decay constant.
123310481
A Study of the Off-Shell Calculation in the Quark-Gluon Vertex
The off-shell calculation is studied in the quark-gluon vertex with dimension-4 gluon condensate in the fixed-point gauge. It is noted that the evaluated result depends on whether the zero point is set on the fermionic or gluonic line for the off-shell calculation in the quark-gluon vertex. In order to obtain more reasonable results, it is suggested that a covariant gauge should be adopted.
119015814
Probing Anomalous Top Quark Couplings at the Future Linear Colliders
In terms of an effective Lagrangian we investigate the possibilities of probing anomalous top quark couplings, $t \bar{t} H$, $\gamma t \bar{t}$, $Z t \bar{t}$ and $tWb$ at the future linear colliders. It is found that probing anomalous top quark couplings, $t \bar{t} H$, $\gamma t \bar{t}$, $Z t \bar{t}$ and $tWb$ at the future linear colliders. It is found that at a linear collider with a c.m.energy $\sqrt s \sim 0.5-1.5$ TeV and a high luminosity of 10-1000 fb$^{-1}$, $e^+e^- \to t \bar{t} H$ is an ideal process in probing anomalous $t \bar t H$ couplings. We also study in detail the effects of anomalous couplings on $t \bar{t}$ spin correlations in the top pair production as well as the top quark decay processes with three bases (helicity, beam line and off-diagonal bases). Our results show that with a c. m. energy $\sqrt s \sim 0.5-1$ TeV and a high luminosity of 1-100 fb$^{-1}$, the anomalous couplings $\gamma t \bar{t}$, $Z t\bar{t}$ and $tWb$ may be sensitively probed.
118657805
Finding a way to determine the pion distribution amplitude from the experimental data
It is believed that one can extract more accurate information of the pion distribution amplitude from the pion-photon transition form factor (TFF) due to the single pion in this process. However the BABAR and Belle data of the pion-photon TFF have a big difference for Q ∈ [15, 40] GeV, and at present, the pion DA can not be definitely determined from the pion-photon TFF. it is crucial to find the right pion DA behavior and to determine which data is more reliable. In this letter, we perform a combined analysis of the most existing data of the processes involving pion by using a general model for the pion wavefunction/DA. Such a DA model can mimic all the existed pion DA behaviors, whose parameters can be fixed by the constraints from the processes π → γγ, π → μν, B → πlν, and etc. Especially, we examine the B → π transition form factors that provides another constraint to the parameter B in our DA model, which results in B ∈ [0.00, 0.29]. This inversely shows that the predicted curve for the pion-photon TFF is between the BABAR and Belle data in the region Q ∈ [15, 40] GeV. It will be tested by coming more accurate data at large Q region, and the definite behavior of pion DA can be concluded finally.
123468539
A DISCUSSION ON THE EXISTENCE OF THE SADDLE-POINT SOLUTION
We prove that there is no saddle point solution in the (1 + 1)-dimensional O(3) nonlinear sigma model with a term explicitly breaking symmetry down to O(2). In the standard model, it is shown that the ansatz of Monton is not sufficient to get a saddle point solution of the theory. Thus the question of baryon number violation based on the saddle point solution in the electroweak theory should be re-examined.
110609545
SLAC Control Room Consolidation Using Linked Computers
Consolidation of two large accelerator control rooms using digital computers connected by a data link is described. Several consolidation plans are discussed and the adopted solution is described. The key elements are touch panels operating with a TV display system.
35673041
Decays of excited charmed Lambda -type and Sigma -type baryons in heavy hadron chiral perturbation theory.
Ground states and some excited p-wave states of heavy baryons are studied within the framework of heavy hadron chiral perturbation theory. The effective Lagrangian is written out to terms of the next-to-leading order in 1/${\mathit{m}}_{\mathit{Q}}$ or 1/${\mathrm{\ensuremath{\Lambda}}}_{\mathrm{\ensuremath{\chi}}}$. The coupling constants are estimated using the experimental data of \ensuremath{\Lambda} and \ensuremath{\Sigma} baryons in the static limit of the s quark. The single pion and double pion decay rates of these charmed baryons have been estimated. The numerical results show that both ${\mathrm{\ensuremath{\Lambda}}}_{\mathit{c}}$(1/${2}^{\mathrm{\ensuremath{-}}}$) and ${\mathrm{\ensuremath{\Lambda}}}_{\mathit{c}}$(3/${2}^{\mathrm{\ensuremath{-}}}$) are very narrow. We conclude that the two pion channel may offer the best hope for detecting the ${\mathrm{\ensuremath{\Sigma}}}_{\mathit{c}}$(3/${2}^{\mathrm{\ensuremath{-}}}$) and ${\mathrm{\ensuremath{\Sigma}}}_{\mathit{c}}$(1/${2}^{\mathrm{\ensuremath{-}}}$) p-wave doublet.
29791617
Gravitational field of radiating cosmic string.
We examine the Einstein equation with the energy-momentum tensors which correspond to an infinite line string of finite radius plus an outgoing radiation field. It is used to see the effect of the radiation field on the spacetime of a cosmic string. We make some assumptions about the metric coefficients and find a class of exact solutions. The result can be applied to studying the back reaction on a radiating cosmic string.
39608513
Bethe-Salpeter wave functions for mesons of arbitrary spin and the covariant instantaneous approximation.
The most general form of the Bethe-Salpeter (BS) wave functions for mesons of arbitrary spin and definite parity is given. Using the BS equation, the constraints on the BS wave function due to assuming the covariant instantaneous approximation are found. The application of the general formalism to heavy mesons is given and, in particular, the results from the spin SU(2) symmetry of the heavy quark are naturally obtained in the infinite quark mass limit.
46429286
Adiabatic regularization of the quantum stress-energy tensor in curved spacetimes: Path-integral quantization method.
A possible way to obtain the adiabatic regularized quantum stress-energy tensor in a background curved spacetime is developed within the method of path-integral quantization. As an illustration, we study the mode of a massive scalar field with arbitrary curvature coupling to the inhomogeneous conformally flat spacetime. The results so obtained are useful to investigate the back-reaction effects of a quantized field in the early Universe with an inhomogeneity.
13115734
Boson-fermion transmutation and the statistics of anyons.
It is shown that, by allowing a transmutation between a boson and a fermion, the system with both bosons and fermions will have the statistical distribution function of an anyon.