119090605
Choice of heavy baryon currents in QCD sum rules
In this paper we investigate the effects due to the mixing of two interpolating currents for ground state baryons within the framework of Heavy Quark Effective Theory using the QCD sum rule approach. Both two-point and three-point sum rules, thus the mass, coupling constant and Isgur-Wise function sum rules are considered. It is interesting to contrast those results with each other. Based on the Isgur-Wise functions obtained in this paper, we also analyze the effects of current mixing to Lambda-type and and Sigma-type semi-leptonic decays Lambda_b-->Lambda_c\ell\bar\nu, \Sigma_b-->\Sigma_c\ell\bar\nu and \Sigma_b-->\Sigma^*_c\ell\bar\nu. Decay widths corresponding to various mixing parameters are obtained and can be compared to the experimental data.
119432190
Semileptonic decay Lambda(c) ---> Lambda l+ nu from QCD light-cone sum rules
We present the study of the semileptonic decay \Lambda_c to \Lambda\ell^+\nu by using the light-cone sum rule approach. Distribution amplitudes (DAs) for the \Lambda baryon are discussed to the leading order conformal spin, and QCD sum rule estimate for the corresponding parameters is presented. The form factors describing the decay are calculated and used to predict the decay width and the decay asymmetry parameter \alpha. With the inclusion of twist-3 contributions the calculated decay width \Gamma=(7.2+/-2.0)X10^{-14} GeV as well as asymmetry \alpha=-(0.88+/-0.03) is found in good agreement with the experimental data, while there are appreciable deviations from experiment values when the higher twist contributions are included.
121216453
Heavy quark effective theory sum rules for higher excited charmed mesons: With a view on D(sJ)(2632)
Mass of the excited (1{sup -},2{sup -}) (2{sup -},3{sup -}) and (2{sup +},3{sup +}) cs states is calculated to the 1/m{sub Q} order within the framework of the heavy quark effective theory using QCD sum rule method. The obtained kinetic energy is comparable to the c-quark mass, thus results in large 1/m{sub Q} correction for the c-quark case. With the sum rules for the chromomagnetic interaction term, the mass splitting for the three doublets is presented. Based on the predicted mass spectrum the exotic D{sub sJ}(2632) state, if really exists, is unlikely to be a conventional orbitally higher excited cs state, although the experimental center lies within the range for the mass of the 1{sup -} meson.
9083411
Improved analysis for the baryon masses to order Lambda(QCD) / m(Q) from QCD sum rules
We use the QCD sum rule approach to calculate the masses of the Lambda_Q and Sigma_Q baryons to the Lambda_{QCD}/m_Q order within the framework of heavy quark effective theory. We compare the direct approach and the covariant approach to this problem. Two forms of currents have been adopted in our calculation and their effects on the results are discussed. Numerical results obtained in both direct and covariant approaches are presented. The splitting between spin 1/2 and 3/2 doublets derived from our calculation is {\Sigma_Q^*}^2-\Sigma_Q^2\simeq 0.35\pm 0.03 GeV^2 which is in good agreement with the experiment.
118399148
Light cone QCD sum rules for the semileptonic decay Lambda(b) -> p l anti-nu
The exclusive semileptonic heavy baryon decay \Lambda_b\to p l\bar\nu is investigated using light-cone sum rule method in both full QCD and HQET. The form factors describing the decay are calculated and used to predict the decay width and differential distribution. The total decay width obtained from full QCD is in agreement with the previous theoretical predictions while the HQET result are typically one order smaller. Both results are consistent with the experimental upper limit and can be compared to the refined experimental data in the future.
53867504
On the soliton solutions of the two-dimensional Toda lattice
The two-dimensional Toda lattice (2DTL) is a well-known (2+1)-dimensional integrable system that admits a large class of line-soliton solutions. We classify these soliton solutions by exploiting the structure of the Casoratian expression for its tau function. In general, these solutions consist of unequal numbers of 'incoming' and 'outgoing' line solitons. We classify the incoming and outgoing line solitons based on asymptotic analysis of the tau function of the 2DTL as the discrete variable tends to infinity. We also identify various subclasses of solutions and characterize some of them in terms of the amplitudes and directions of the interacting solitons. As a special case, we obtain the reduction in the soliton solutions of the one-dimensional Toda lattice. Throughout, we point out the similarities with—and the differences from—the corresponding results for the Kadomtsev–Petviashvili equation.
119256536
Polarization switching demonstration using crossed-planar undulators in a seeded free-electron laser
Polarization switching of light sources is required over a wide spectral range to investigate the symmetry of matter. In this paper, we report the first experimental demonstration of the crossed-planar undulators technique at a seeded free-electron laser, which holds great promise for the full control and fast switching of the polarization of short-wavelength radiation. In the experiment, the polarization state of the coherent radiation at the secondharmonic of the seed laser is switched successfully. The experimental results confirm the theory and pave the way for applying the crossed-planar undulators technique for seeded x-ray free-electron lasers.
122204593
Measurement of femtosecond electron bunches using a rf zero-phasing method
Bunch lengths as short as 84 fs (rms) have been measured at Jefferson Laboratory using a rf zero-phasing technique. To the best of our knowledge, this is the first accurate measurement of the longitudinal distribution function in this regime. In this paper, an analytical approach for computing the longitudinal distribution function and bunch length is described for arbitrary longitudinal and transverse distributions for the case where the intrinsic energy spread of the bunch is small compared to the correlated energy spread imparted by zero-phasing cavities. The measurement results are presented, which are in excellent agreement with numerical simulations. {copyright} {ital 1998} {ital The American Physical Society}
120921557
Gamow-Teller strength distribution in 81Kr and the consequences for a 81Br solar neutrino detector
Abstract Neutron time-of-flight measurements have been performed on the 81 Br(p,n) 81 Kr reaction at E p = 190 and 200 MeV. Gamow-Teller transition strengths have been deduced for final 81 Kr states accessible through solar neutrino capture on 81 Br. For the standard solar model, 81 Br is most sensitive to 8 B neutrinos, not — as previously believed — 7 Be neutrinos.
119272921
Single-shot measurement of free-electron laser polarization at SDUV-FEL
In this paper, a division-of-amplitude photopolarimeter (DOAP) for measuring the polarization state of a free-electron laser (FEL) pulse is described. The incident FEL beam is divided into four separate beams, and four Stokes parameters can be measured in a single-shot. In the crossed-planar undulators experiment at the Shanghai deep ultraviolet FEL test facility, this DOAP instrument constructed in house responsed accurately and timely while the polarization-state of fully coherent FEL pulses were switched, which is helpful for confirming the crossed-planar undulators technique for short-wavelength FELs.