119297105
On the two-loop hexagon Wilson loop remainder function in N=4 SYM
Abstract A duality relation has been proposed between the planar gluon MHV amplitudes and light-like Wilson loops in N = 4 super Yang–Mills. At six-point two-loop, the results for the planar gluon MHV amplitude and for the light-like Wilson loop agree, but they both differ from the Bern–Dixon–Smirnov ansatz by a finite remainder function. Recently Del Duca, Duhr and Smirnov presented an analytical result for the two-loop hexagon Wilson loop remainder function in general kinematics. Their result is rather lengthy, and the dependence on the conformal cross ratios appears in a complicated way. Here we present an alternate, more compact representation for the two-loop hexagon Wilson loop remainder function.
38560063
Physics of the gluon-helicity contribution to proton spin.
The total gluon helicity in a polarized proton, measurable in high-energy scattering, is shown to be the large momentum limit of a gauge-invariant but nonlocal, frame-dependent gluon spin E × A⊥ in QCD. This opens a door for a nonperturbative calculation of this quantity in lattice QCD and also justifies using free-field expressions in the light-cone gauge as physical observables.
118538162
Hydrodynamics of a 5D Einstein-dilaton black hole solution and the corresponding BPS state
A bstractWe apply the potential reconstruction approach to generate a series of asymp-totically AdS (aAdS) black hole solutions, with a self-interacting bulk scalar field. Based on the method, we reproduce the pure AdS solution as a consistency check and we also generate a simple analytic 5D black hole solution. We then study various aspects of this solution, such as temperature, entropy density and conserved charges. Furthermore, we study the hydrodynamics of this black hole solution in the framework of fluid/gravity duality, e.g. the ratio of the shear viscosity to the entropy density. In a degenerate case of the 5D black hole solution, we find that the c function decreases monotonically from UV to IR as expected. Finally, we investigate the stability of the degenerate solution by studying the bosonic functional energy of the gravity and the Witten-Nester energy EWN. We confirm that the degenerate solution is a BPS domain wall solution. The corresponding superpotential and the solution of the killing spinor equation are found explicitly.
118117795
Radiative corrections to $h^0\to WW^*/ZZ^*\to 4$\,leptons in the MSSM
The electroweak $\mc O(\alpha)$ radiative corrections to the decay of the lightest MSSM Higgs boson to four leptons are presented, improved by the two-loop corrections provided by the program package FeynHiggs. We also analyze the results in the decoupling limit and investigate the numeric impact of contributions from the genuine supersymmetric particle spectrum.
119224499
On the Yang–Mills two-loop effective action with worldline methods
Abstract We derive the two-loop effective action for covariantly constant field strength of pure Yang–Mills theory in the presence of an infrared scale. The computation is done in the framework of the worldline formalism, based on a generalization procedure of constructing multiloop effective actions in terms of the bosonic worldline path integral. The two-loop β -function is correctly reproduced. This is the first derivation in the worldline formulation, and serves as a non-trivial check on the consistency of the multiloop generalization procedure in the worldline formalism.
54928710
Gravity/Fluid Correspondence and Its Application on Bulk Gravity with Gauge Field
As the long wavelength limit of the AdS/CFT correspondence, the gravity/fluid correspondence has been shown to be a useful tool for extracting properties of the fluid on the boundary dual to the gravity in the bulk. In this paper, after briefly reviewing the algorithm of gravity/fluid correspondence, we discuss the results of its application on bulk gravity with a gauge field. In the presence of a gauge field, the dual fluid possesses more interesting properties such as its charge current. Furthermore, an external field could affect the charge current, and the Chern-Simons term also induces extra structures to the dual current giving anomalous transport coefficients.
6718095
Towards the continuum limit of the overlap quark propagator in Landau gauge
Abstract The properties of the momentum space quark propagator in Landau gauge are examined for the overlap quark action in quenched lattice QCD. Numerical calculations were done on two lattices with different lattice spacing a and similar physical volumes to explore the quark propagator in the continuum limit. We have calculated the nonperturbative wavefunction renormalization function Z(p ) and the nonperturbative mass function M(p) for a variety of bare quark masses and perform a simple linear extrapolation to the chiral limit. We find the behaviour of Z(p) and M(p) in the chiral limit are in good agreement between the two lattices.
121658594
Effects of dynamical FLIC fermions in the quark and gluon propagator
In this work we examine the FLIC overlap quark propagator and the gluon propagator on both dynamical and quenched lattices. The tadpole improved Luscher-Weisz gauge action is used in both cases. The dynamical gauge fields use the FLIC fermion action for the sea quark contribution. We observe that the presence of sea quarks causes a suppression of the mass function, quark renormalisation function and gluon dressing function in the infrared. The ultraviolet physics is unaffected.
16387762
Overlap fermions on a 204 lattice
We report results on hadron masses, fitting of the quenched chiral log, and quark masses from Neuberger's overlap fermion on a quenched 204 lattice with lattice spacing a = 0.15 fm. We used the improved gauge action which is shown to lower the density of small eigenvalues for H2 as compared to the Wilson gauge action. This makes the calculation feasible on 64 nodes of CRAY-T3E. Also presented is the pion mass on a small volume (63 × 12 with a Wilson gauge action at β = 5.7). We find that for configurations that the topological charge Q ≠ 0, the pion mass tends to a constant and for configurations with trivial topology, it approaches zero possibly linearly with the quark mass.
118406545
Next-to-leading order QCD corrections to the top quark decay via the flavor-changing neutral-current operators with mixing effects
Detailed calculations of the complete $\mathcal{O}({\ensuremath{\alpha}}_{s})$ corrections to the top-quark decay widths $\ensuremath{\Gamma}(t\ensuremath{\rightarrow}q+V)$ with $V=g$, $\ensuremath{\gamma}$, $Z$, and $q=u$, $c$ are presented. Besides describing in detail the calculations in our previous work [Phys. Rev. Lett. 102, 072001 (2009)], we also include the mixing effects of the flavor-changing neutral-current operators for $t\ensuremath{\rightarrow}q+\ensuremath{\gamma}$ and $t\ensuremath{\rightarrow}q+Z$, which were not considered previously. We show that the mixing effects can either be large or small depending on the values of various anomalous couplings and thereby increase or decrease the branching ratios for $t\ensuremath{\rightarrow}q+\ensuremath{\gamma}$ and $t\ensuremath{\rightarrow}q+Z$.
118623641
Threshold resummation effects in neutral Higgs boson production by bottom quark fusion at the CERN Large Hadron Collider
We investigate the QCD effects in the production of neutral Higgs bosons via bottom quark fusion in both the standard model and the minimal supersymmetric standard model at the CERN Large Hadron Collider. We include the next-to-leading order (NLO) QCD corrections (including supersymmetric QCD) and the threshold resummation effects. We use the soft-collinear effective theory to resum the large logarithms near threshold from soft gluon emission. Our results show that the resummation effects can enhance the total cross sections by about 5% compared with the NLO results.