32279311
Hadronic wave functions in D and B decays.
We propose meson wave functions and discuss their properties, such as the moments and the average transverse momenta. We also modify the Bauer-Stech-Wirbel (BSW) model by applying these wave functions to exclusive decays of {ital D} and {ital B} mesons. Comparisons between our results and those of BSW are given. An upper limit of {ital V}{sub {ital u}{ital b}} which is smaller than that of the BSW model is found.
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.
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.
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.
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.
73519332
RHIC Performance for FY10 200 GeV Au+Au Heavy Ion Run
Since the last successful RHIC Au+Au run in 2007 (Run-7), the RHIC experiments have made numerous detector improvements and upgrades. In order to benefit from the enhanced detector capabilities and to increase the yield of rare events in the acquired heavy ion data a significant increase in luminosity is essential. In Run-7 RHIC achieved an average store luminosity of = 12 × 10 cm−2 s−1 by operating with 103 bunches (out of 111 possible), and by squeezing to β∗ = 0.85 m. This year, Run-10, we achieved = 20 × 10 cm−2 s−1, which put us an order of magnitude above the RHIC design luminosity. To reach these luminosity levels we decreased β∗ to 0.75 m, operated with 111 bunches per ring, and reduced longitudinal and transverse emittances by means of bunched-beam stochastic cooling. In addition we introduced a lattice to suppress intra-beam scattering (IBS) in both RHIC rings, upgraded the RF control system, and separated transition crossing times in the two rings. We present an overview of the changes and the results of Run-10 performance.
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.
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.
46025843
Heavy quark symmetry, chiral symmetry, and parity doublets of heavy mesons in the Bethe-Salpeter approach.
It is shown that there must exist degenerate parity doublets of heavy mesons with arbitrary spin if QCD possesses both heavy quark and chiral symmetries. The chiral symmetric pahase and chiral broken phase can be dynamically turned in the Bethe-Salpeter approach. In the chiral broken phase the mass splittings of the parity doublets can be calculated and they are proportional to the constituent mass [ital m] of the light quark to order [ital m]/[Lambda][sub [chi]].
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.