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.
118143037
Multidimensional Residues for Feynman Integrals with Generic Power of Propagators
We propose that the concept of multidimensional residues can be used to directly extracting the coefficients of scalar master integrals (with single propagators only) from one-loop Feynman integrals with generic power of propagators. Unlike the usual integration-by-parts (IBP) technique, where one has to solve iteratively a complicated set of equations to carry out the reduction and determine the coefficients of scalar master integrals, using multidimensional residues provides the possibility of directly extracting the coefficients of the master integrals. As the first application of this idea, we show how to directly extract the scalar box integral coefficients.
119115860
Justifying the naive partonic sum rule for proton spin
Abstract We provide a theoretical basis for understanding the spin structure of the proton in terms of the spin and orbital angular momenta of free quarks and gluons in Feynman's parton picture. We show that each term in the Jaffe–Manohar spin sum rule can be related to the matrix element of a gauge-invariant, but frame-dependent operator through a matching formula in large-momentum effective field theory. We present all the matching conditions for the spin content at one-loop order in perturbation theory, which provide a basis to calculate parton orbital angular momentum in lattice QCD at leading logarithmic accuracy.
119308558
Vacuum stability and Higgs diphoton decay rate in the Zee-Babu model
A bstractAlthough recent Higgs data from ATLAS and CMS are compatible with a Standard Model (SM) signal at 2σ level, both experiments see indications for an excess in the diphoton decay channel, which points to new physics beyond the SM. Given such a low Higgs mass mH ~ 125 GeV, another sign indicating the existence of new physics beyond the SM is the vacuum stability problem, i.e., the SM Higgs quartic coupling may run to negative values at a scale below the Planck scale. In this paper, we study the vacuum stability and enhanced Higgs diphoton decay rate in the Zee-Babu model, which was used to generate tiny Majorana neutrino masses at two-loop level. We find that it is rather difficult to find overlapping regions allowed by the vacuum stability and diphoton enhancement constraints. As a consequence, it is almost inevitable to introduce new ingredients into the model, in order to resolve these two issues simultaneously.
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.
118483519
Hydrodynamics with conserved current via AdS/CFT correspondence in the Maxwell-Gauss-Bonnet gravity
Using the AdS/CFT correspondence, we study the hydrodynamics with conserved current from the dual Maxwell-Gauss-Bonnet gravity. After constructing the perturbative solution to the first order based on the boosted black brane solution in the bulk Maxwell-Gauss-Bonnet gravity, we extract the stress tensor and conserved current of the dual conformal fluid on its boundary, and also find the effect of Gauss-Bonnet term on the dual conformal fluid. Our results show that the Gauss-Bonnet term can affect the parameters such as the shear viscosity $\eta$, entropy density $s$, thermal conductivity $\kappa$ and electrical conductivity $\sigma$. However, it does not affect the so-called Wiedemann-Franz law which relates $\kappa$ to $\sigma$, while it affects the ratio $\eta/s$. In addition, another interesting result is that the $\eta/s$ can also be affected by the bulk Maxwell field in our case, which is consistent with some previous results predicted through the Kubo formula. Moreover, the anomalous magnetic and vortical effects by adding the Chern-Simons term are also considered in our case in the Maxwell-Gauss-Bonnet gravity.
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 $t\ensuremath{\rightarrow}q+Z$.
117031507
Preheating in a DBI Inflation Model
We study the preheating process in a model of DBI inflation with a DBI-type inflaton coupling to a canonical entropy field. At the end of inflation, the inflaton field oscillates around its vacuum which can arise from an infrared cutoff parameter on the warp factor and correspondingly the evolution of its fluctuations can be approximately described by a generalized Hill's equation in third order. We study the field fluctuations numerically and show that they could grow exponentially since the instability bands commonly exist in the DBI models if the amplitudes of background oscillations are of order or larger than the cutoff parameter. Our numerical result also reveals that the particle excitation of the matter field is more dramatic than that in usual case since the parametric resonance lasts longer when the effect of a warp factor is taken into account. Therefore, we conclude that the preheating process in the model of DBI inflation could be more efficient than that in standard inflation models.
118496902
Note on thermodynamics method of black hole/CFT correspondence
A bstractIn the paper we further refine the thermodynamics method of black hole/CFT correspondence. We show that one can derive the central charges of different holographic pictures directly from the entropy product S+S− if it is mass-independent, for a black hole in the Einstein gravity or the gravity without diffeomorphism anomaly. For a general black hole in the Einstein gravity that admits holographic descriptions, we show that the thermodynamics method and asymptotic symmetry group (ASG) analysis can always give consistent results in the extreme limit. Furthermore, we discuss the relation between black hole thermodynamics and the hidden conformal symmetry. We show that the condition T+A+ = T−A−, with A± being the outer and inner horizon areas, is the necessary, but not sufficient, condition for a black hole to have the hidden conformal symmetry. In particular, for the Einstein(-Maxwell) gravity T+A+ = T−A− is just the condition T+S+ = T−S−, with S± being the outer and inner horizon entropies, which is the condition for the entropy product S+S− being mass-dependent. When there exists the hidden conformal symmetry in the low-frequency scattering off the generic non-extremal black hole, it always leads to the same temperatures of dual CFT as the ones got from the thermodynamics method.
118595684
Next-to-leading order QCD corrections to the single top quark production via model-independent tqg flavor-changing neutral-current couplings at hadron colliders
We present the calculations of the complete next-to-leading order (NLO) QCD effects on the single top productions induced by model-independent tqg flavor-changing neutral-current couplings at hadron colliders. Our results show that, for the tcg coupling, the NLO QCD corrections can enhance the total cross sections by about 60% and 30%, and for the tug coupling by about 50% and 20% at the Tevatron and LHC, respectively, which means that the NLO corrections can increase the experimental sensitivity to the flavor-changing neutral-current couplings by about 10%-30%. Moreover, the NLO corrections reduce the dependence of the total cross sections on the renormalization or factorization scale significantly, which lead to increased confidence on the theoretical predictions. Besides, we also evaluate the NLO corrections to several important kinematic distributions, and find that for most of them the NLO corrections are almost the same and do not change the shape of the distributions.
41278561
The silicon matrix for the prototype for the Dark Matter Particle Explorer
In this paper, a silicon matrix detector is described and the results of the cosmic ray test are given. The silicon matrix is composed by the 180 silicon PIN detectors, which covers an area of 32 * 20cm2. The data of whole detectors is read out by the ASIC chips, and suppressed by an FPGA. In the test system, the trigger is given by two plastic scintillators, which are placed above and beneath the silicon matrix. The MIPs energy spectrum is shown in this paper. In further test, a small plastic scintillator is inserted to give a differential cosmic ray counting response.