29696360
Nonperturbative effects on the Wilson coefficients and the Delta I=(1/2 rule in kaon decays.
We apply the vacuum-background-field method and the modified renormalization-group equation in the energy region {mu}{lt}1 GeV to correct the Wilson coefficients in the {Delta}{ital S}=1 effective weak Hamiltonian responsible for {ital K}{r arrow}2{pi} decays. We find that the change of {ital C}{sub {plus minus}} results in an enhancement to the {Delta}{ital I}={1/2} amplitude by a factor of 2 at the scale {mu}=0.6 GeV for {ital K}{r arrow}2{pi} decays.
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.
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.
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.
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.
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.
5758218
Adiabatic regularization of the quantum stress-energy tensor in curved spacetimes: Stochastic quantization method.
It is found that the adiabatic regularized quantum stress-energy tensor for matter in any background spacetime can be obtained in the framework of stochastic quantization. As an illustration, we investigate the modes of a massive scalar field with arbitrary curvature coupling to the inhomogeneous conformally flat spacetime. The difficulty of the mode-mixing behavior arising from the spacetime inhomogeneity is overcome and a simple algorithm is presented to evaluate the adiabatic regularized quantum stress-energy tensor. The expressions so obtained are useful in formulating the semiclassical theory of gravity and in the numerical study of the back-reaction effects of quantized fields in inhomogeneous spacetimes, such as the problems of homogenization in the early universe and the evaporation of a quantum black hole. It can be seen that our prescriptions may be extended to investigate more realistic models with fermions and gauge fields. This will be studied in future papers.
7473966
Renormalization of the quantum stress-energy tensor in inhomogeneous spacetimes: Adiabatic regularization method.
The adiabatic regularization method, known to be a particularly efficient method for numerical study of quantum field dynamics in curved spacetimes, is applicable to evaluate the renormalized stress-energy tensor for matter in any background metric which has sufficient symmetry to allow a decomposition of the quantized field into modes. In this paper we extend this method to more general spacetimes with a small inhomogeneity which is invariant under spatial reflection. We overcome the difficulty of the mode-mixing behavior arising from the inhomogeneity of spacetime and show a possible way of obtaining the WKB solution of the time-dependent mode function under the early-time approximation. As an illustration, we investigate the renormalization of the quantum stress-energy tensor for a massive scalar field with an arbitrary curvature coupling to the inhomogeneous conformally flat spacetime. Our expressions are useful in formulating the semiclassical theory of gravity and in the numerical study of the back reaction of quantized fields in the early Universe with a small inhomogeneity.
10679146
Conformal transformation of renormalized effective action in curved spacetimes.
The functional-differential equation which governs the conformal transformation of the renormalized effective action for a massless, conformally invariant quantized field is solved exactly. The formula so obtained can be used to obtain the effective action in any background spacetime once there exists a conformally related spacetime in which the effective action is known. A simple example is presented to see how our formula is useful to obtain the renormalized stress tensor in the \ensuremath{\zeta}-functional regularization scheme.
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.
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.