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.
119501195
A Phenomenological expression for deuteron electromagnetic form-factors based on perturbative QCD predictions
For deuteron's electromagnetic form factors, perturbative QCD (pQCD) predicts that G(00)(+) becomes the dominate helicity amplitude and G(+0)(+), and G(+-)(+) are suppressed by factors Lambda QCD/Q and Lambda (2)(QCD)/Q(2) at large Q(2) respectively. We try to discuss the higher-order corrections beyond the pQCD asymptotic predictions by interpolating an analytical form to the intermediate energy region. From fitting the data, our results show that the helicity-zero to zero matrix element G(00)(+) dominates the gross structure function A(Q(2)) in both the large and intermediate energy regions. It is a good approximation for G(+-)(+) to ignore the higher-order contributions and the higher-order corrections to G(+0)(+) should be taken into account due to sizeable contributions in the intermediate energy region.
120804150
Ways to measure the hairpin diagram in charmed meson decays
The possible presence of hairpin diagrams is analyzed in th model-independent quark-diagram scheme for two-body decays of charmed mesons. Current experimental data do not require the presence of hairpin diagrams inD→VP (V: vector meson,P: pseudoscalar meson), in accordance with the OZI rule. However, there is a possible indication that they are important in the decay ofD→PP. The measurement ofDs+→π+η′ is crucial to test the mechanism of hairpin diagrams.
120469548
Discussion on the Translational Invariance of the Gluon Condensate
In this article, the nonvanishing vacuum average value of two-point function of gluons Ω|Aμa(x)Aνb(y)|Ω, which is related to the quantitative analyses of the nonperturbative effects in quantum chromodynamics(QCD), is expanded in the space-time interval r=x-y in the Lorentz gauge. The first two coefficient values are estimated with the phenomenological values for the vacuum condensates Ω|G2|Ω and Ω|ψ|Ω through the QCD motion equations. The advantage of the expansion is that the series remains translationally invariant as compared with the expansion of Ω|Aμa(x)Aνb(y)|Ω in the fixed-point gauge.
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.
109238158
BXERL photo-injector based on a 217 MHz normal conducting RF gun
The Beijing X-ray Energy Recovery Linac (BXERL) test facility is proposed in Institute of High Physics (IHEP). In this proposal, the main linac requires the injector to provide an electron beam with 5 MeV energy and 10 mA average current. An injector based on DC gun technology is the first candidate electron source for BXERL. However, the field emission in the DC gun cavity makes it much more difficult to increase the high voltage to more than 500 kV. Another technology based on a 217 MHz normal conducting RF gun is proposed as the backup injector for this test facility. We have designed this RF gun with 2D SUPERFISH code and 3D MICROWAVE STUDIO code. In this paper, we present the optimized design of the gun cavity, the gun RF parameters and the set-up of the whole injector system. The detailed beam dynamics have been done and the simulation results show that the injector can generate electron bunches with RMS normalized emittance 1.0 πmm·mrad, bunch length 0.77 mm, beam energy 5.0 MeV and energy spread 0.60%.