Bonus scaling and BCFW in N=7 supergravity

In search of natural building blocks for supergravity amplitudes, a tentative criteria is term-by-term bonus z−2 large momentum scaling. For a given choice of deformation legs, we present such an expansion in the form of a BCFW representation in N=7 supergravity based on a special shift. We will show that this improved scaling behavior, with respect to the fully N=8 representation, is due to its automatic incorporation of the so called bonus relations

Exact pseudofermion action for Monte Carlo simulation of domain-wall fermion

We present an exact pseudofermion action for hybrid Monte Carlo simulation (HMC) of one-flavor domain-wall fermion (DWF), with the effective 4-dimensional Dirac operator equal to the optimal rational approximation of the overlap-Dirac operator with kernel H=cHw(1+dγ5Hw)−1 where c and d are constants. Using this exact pseudofermion action, we perform HMC of one-flavor QCD, and compare its characteristics with the widely used rational hybrid Monte Carlo algorithm (RHMC). Moreover, to demonstrate the practicality of the exact one-flavor algorithm (EOFA), we perform the first dynamical simulation of the ( 1+1 )-flavors QCD with DWF

Charge loss (or the lack thereof) for AdS black holes

The evolution of evaporating charged black holes is complicated to model in general, but is nevertheless important since the hints to the Information Loss Paradox and its recent firewall incarnation may lie in understanding more generic geometries than that of Schwarzschild spacetime. Fortunately, for sufficiently large asymptotically flat Reissner-Nordström black holes, the evaporation process can be modeled via a system of coupled linear ordinary differential equations, with charge loss rate governed by Schwinger pair-production process. The same model can be generalized to study the evaporation of AdS Reissner-Nordström black holes with flat horizon. It was recently found that such black holes always evolve towards extremality since charge loss is inefficient. This property is completely opposite to the asymptotically flat case in which the black hole eventually loses its charges and tends towards Schwarzschild limit. We clarify the underlying reason for this different behavior

The localization principle in SUSY gauge theories

The localization principle is a powerful analytic tool in supersymmetric gauge theories which enables one to perform supersymmetric path integrals explicitly. Many important formulae have been obtained, and they led to a major breakthrough in the understanding of gauge theories at strong coupling as well as the dynamics of branes in M-theory. Some of those results are reviewed, focusing especially on Pestun's solution to four-dimensional supersymmetric gauge theories on and the subsequent developments on three- or four-dimensional gauge theories on spheres

On some computations of higher rank refined Donaldson-Thomas invariants

We present some computations of higher rank refined Donaldson-Thomas invariants on local curve geometries, corresponding to local D6-D2-D0 or D4-D2-D0 configurations. A refined wall-crossing formula for invariants with higher D6 or D4 rank is derived and verified to agree with the existing formulas under the unrefined limit. Using the formula, refined invariants on the (−1, −1) and (−2, 0) local rational curve with higher D6 or D4 ranks are computed

Charged Higgs contribution to B¯s→ϕπ0 and B¯s→ϕρ0

We study the decay modes B¯s→ϕπ0 and B¯s→ϕρ0 within the frameworks of two-Higgs doublet models type-II and type-III. We adopt in our study Soft Collinear Effective Theory as a framework for the calculation of the amplitudes. We derive the contributions of the charged Higgs mediation to the weak effective Hamiltonian governing the decay processes in both models. Moreover, we analyze the effect of the charged Higgs mediation on the Wilson coefficients of the electroweak penguins and on the branching ratios of B¯s→ϕπ0 and B¯s→ϕρ0 decays. We show that within two-Higgs doublet models type-II and type-III the Wilson coefficients corresponding to the electroweak penguins can be enhanced due to the contributions from the charged Higgs mediation leading into enhancement in the branching ratios of B¯s→ϕπ0 and B¯s→ϕρ0 decays. We find that, within two-Higgs doublet models type-II, the enhancement in the branching ratio of B¯s→ϕπ0 cannot exceed 18% with respect to the SM predictions. For the branching ratio of B¯s→ϕρ0 , we find that the charged Higgs contribution in this case is small where the branching ratio of B¯s→ϕρ0 can be enhanced or reduced by about 4% with respect to the SM predictions. For the case of the two-Higgs doublet models type-III we show that the branching ratio of B¯s→ϕπ0 can be enhanced by about a factor 2 of its value within two-Higgs doublet models type-II. However, no sizeable enhancement with respect to the SM predictions can be obtained for both B¯s→ϕπ0 and B¯s→ϕρ0 decays

Decay constants of pseudoscalar D -mesons in lattice QCD with domain-wall fermion

We present the first study of the masses and decay constants of the pseudoscalar D mesons in two flavors lattice QCD with domain-wall fermion. The gauge ensembles are generated on the 243×48 lattice with the extent Ns=16 in the fifth dimension, and the plaquette gauge action at β=6.10 , for three sea-quark masses with corresponding pion masses in the range 260–475 MeV. We compute the point-to-point quark propagators, and measure the time-correlation functions of the pseudoscalar and vector mesons. The inverse lattice spacing is determined by the Wilson flow, while the strange and the charm quark masses by the masses of the vector mesons ϕ(1020) and J/ψ(3097) respectively. Using heavy meson chiral perturbation theory (HMChPT) to extrapolate to the physical pion mass, we obtain fD=202.3(2.2)(2.6) MeV and fDs=258.7(1.1)(2.9) MeV

Dark photons as fractional cosmic neutrino masquerader

Recently, Weinberg proposed a Higgs portal model with a spontaneously broken global U(1) symmetry in which Goldstone bosons may be masquerading as fractional cosmic neutrinos. We extend the model by gauging the U(1) symmetry. This gives rise to the so-called dark photon and dark Higgs. The dark photons can constitute about 0.912 (0.167) to the effective number of light neutrino species if they decouple from the thermal bath before the pions become non-relativistic and after (before) the QCD transition. Restriction on the parameter space of the portal coupling and the dark Higgs mass is obtained from the freeze-out condition of the dark photons. Combining with the collider data constraints on the invisible width of the standard model Higgs requires the dark Higgs mass to be less than a few GeV

Searching for new physics with triple-top signal at the LHC

We study the triple-top quark production predicted by the effective operators at the Large Hadron Collider (LHC) with 14 TeV center-of-mass energy. We calculate the production cross section and find that the ratio of signal to Standard Model background can be large. Observation of triple-top signal would give evidence of signature of new physics. We also show that top quarks can be reconstructed using on-shell conditions and MT2 observable in the case that the anti-top quark decays hadronically and two top quarks decay semileptonically. Using the polarization of top quark, we demonstrate that the effective operators that predict different chirality combinations of top quarks in the final state can be distinguished

Minimal lepton flavor violation implications of the b → s anomalies

The latest measurements of rare b → s decays in the LHCb experiment have led to results in tension with the predictions of the standard model (SM), including a tentative indication of the violation of lepton flavor universality. Assuming that this situation will persist because of new physics, we explore some of the potential consequences in the context of the SM extended with the seesaw mechanism involving right-handed neutrinos plus effective dimension-six lepton-quark operators under the framework of minimal flavor violation. We focus on a couple of such operators which can accommodate the LHCb anomalies and conform to the minimal flavor violation hypothesis in both their lepton and quark parts. We examine specifically the lepton-flavor-violating decays B → K (∗) ℓℓ′, B s → ϕ ℓℓ′, B → (π , ρ )ℓℓ′, and B d,s → ℓℓ′, as well as K L → eμ and K → πeμ , induced by such operators. The estimated branching fractions of some of these decay modes with μτ in the final states are allowed by the pertinent experimental constraints to reach a few times 10 −7 if other operators do not yield competitive effects. We also look at the implications for B → K (∗) νν and K → πνν , finding that their rates can be a few times larger than their SM values. These results are testable in future experiments