118350917
Pseudo scalar contributions to light-by-light correction of muon g−2 in AdS/QCD
Abstract We have performed a holographic calculation of the hadronic contributions to the anomalous magnetic moment of the muon, using the gauge/gravity duality. As a gravity dual model of QCD with three light flavors, we study a U ( 3 ) L × U ( 3 ) R flavor gauge theory in the five-dimensional AdS background with a hard-wall cutoff. The anomalous (electromagnetic) form factors for the pseudo scalars, π 0 , η and η ′ , are obtained from the 5D Chern–Simons term of the gravity dual, which correctly reproduce the asymptotic behavior of the form factor, dictated by QCD. We find the total light-by-light contributions of pseudo scalars to the muon anomalous magnetic moment, a μ PS = 10.7 × 10 − 10 , which is consistent with previous estimates, based on other approaches.
118595793
Bayesian naturalness of the CMSSM and CNMSSM
The recent discovery of the 125.5 GeV Higgs boson at the LHC has fueled interest in the next-to-minimal supersymmetric standard model (NMSSM) as it may require less fine-tuning than the minimal model to accommodate such a heavy Higgs. To this end we present Bayesian naturalness priors to quantify fine-tuning in the (N)MSSM. These priors arise automatically as Occam razors in Bayesian model comparison and generalize the conventional Barbieri-Giudice measure. In this paper we show that the naturalness priors capture features of both the Barbieri-Giudice fine-tuning measure and a simple ratio measure that has been used in the literature. We also show that according to the naturalness prior the constrained version of the NMSSM is less tuned than the CMSSM.
123227475
Results from the bates 12C parity experiment
Abstract We report the results of an experiment measuring the the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from 12 C nuclei. We obtain A exp = 0.60 ± 0.14 ± 0.02 ppm. The first error is statistical and the second is systematic. Using our measured beam polarization of 0.37 ± 0.02, we compute the isoscalar vector hadronic coupling constant γ to be 0.136 ± 0.032 ± 0.009. This agrees with the tree level Standard Model prediction of γ = 0.155 .
118459937
Using energy peaks to count dark matter particles in decays
Abstract We study the determination of the symmetry that stabilizes a dark matter (DM) candidate produced at colliders. Our question is motivated per se , and by several alternative symmetries that appear in models that provide a DM particle. To this end, we devise a strategy to determine whether a heavy mother particle decays into one visible massless particle and one or two DM particles. The counting of DM particles in these decays is relevant to distinguish the minimal choice of Z 2 from a Z 3 stabilization symmetry, under which the heavy particle and the DM are charged and the visible particle is not. Our method is novel in that it chiefly uses the peak of the energy spectrum of the visible particle and only secondarily uses the M T 2 endpoint of events in which the heavy mother particles are pair-produced. We present new theoretical results concerning the energy distribution of the decay products of a three-body decay, which are crucial for our method. To demonstrate the feasibility of our method in investigating the stabilization symmetry, we apply it in distinguishing the decay of a bottom quark partner into a b quark and one or two DM particles. The method can be applied generally to distinguish two- and three-body decays, irrespective of DM.
119805142
Recent FOCUS results on charm mixing and CP violation
We summarize recent results on CP violation and mixing based on a high statistics photo-produced charm sample collected by the FOCUS experiment. We compare the lifetimes of two neutral D meson decays: D0 → K−π+ and D0 → K−K+. A mixing parameter for the neutral D system (yCP) is obtained under the assumption that K−π+ is an equal mixture of CP odd and even eigenstates. In addition, we searched for a CP width asymmetry in D+ → K−K+π+, D0 → K−K+ and D0 → π−π+. We found no evidence for CP violation by comparing the decay rates for the particle and antiparticle.
27444996
Conservative, gravitational self-force for a particle in circular orbit around a Schwarzschild black hole in a radiation gauge
This is the second of two companion papers on computing the self-force in a radiation gauge; more precisely, the method uses a radiation gauge for the radiative part of the metric perturbation, together with an arbitrarily chosen gauge for the parts of the perturbation associated with changes in black-hole mass and spin and with a shift in the center of mass. In a test of the method delineated in the first paper, we compute the conservative part of the self-force for a particle in circular orbit around a Schwarzschild black hole. The gauge vector relating our radiation gauge to a Lorenz gauge is helically symmetric, implying that the quantity h_(αβ)u^(α)u^(β) must have the same value for our radiation gauge as for a Lorenz gauge; and we confirm this numerically to one part in 10^(14). As outlined in the first paper, the perturbed metric is constructed from a Hertz potential that is in a term obtained algebraically from the retarded perturbed spin-2 Weyl scalar, ψ_(0)^(ret). We use a mode-sum renormalization and find the renormalization coefficients by matching a series in L= l + 1/2 to the large-L behavior of the expression for the self-force in terms of the retarded field h_(αβ)^(ret); we similarly find the leading renormalization coefficients of h_(αβ)u^(α)u^(β) and the related change in the angular velocity of the particle due to its self-force. We show numerically that the singular part of the self-force has the form f^(S)_(α) = , the part of ∇_(α)ρ^(-1) that is axisymmetric about a radial line through the particle. This differs only by a constant from its form for a Lorenz gauge. It is because we do not use a radiation gauge to describe the change in black-hole mass that the singular part of the self-force has no singularity along a radial line through the particle and, at least in this example, is spherically symmetric to subleading order in ρ.
118406159
Distinguishing dark matter stabilization symmetries using multiple kinematic edges and cusps
We emphasize that the stabilizing symmetry for dark matter (DM) particles does not have to be the commonly used parity (Z{sub 2}) symmetry. We therefore examine the potential of the colliders to distinguish models with parity stabilized DM from models in which the DM is stabilized by other symmetries. We often take the latter to be a Z{sub 3} symmetry for illustration. We focus on signatures where a single particle, charged under the DM stabilization symmetry decays into the DM and standard model (SM) particles. Such a Z{sub 3}-charged mother particle can decay into one or two DM particles along with the same SM particles. This can be contrasted with the decay of a Z{sub 2}-charged mother particle, where only one DM particle appears. Thus, if the intermediate particles in these decay chains are off-shell, then the reconstructed invariant mass of the SM particles exhibits two kinematic edges for the Z{sub 3} case but only one for the Z{sub 2} case. For the case of on-shell intermediate particles, distinguishing the two symmetries requires more than the kinematic edges. In this case, we note that certain decay chain topologies of the mother particle which are present for the Z{sub 3} casemore » (but absent for the Z{sub 2} case) generate a cusp in the invariant mass distribution of the SM particles. We demonstrate that this cusp is generally invariant of the various spin configurations. We further apply these techniques within the context of explicit models.« less