Higgs two-gluon decay and the top-quark chromomagnetic moment

We study the top quark chromomagnetic factor $\kappa_t$-dependence of the effective interaction ${\cal L}_{hgg}$ and apply the result to the case of Higgs two gluon decay rate $\Gamma_{h\to gg}$. Perturbative standard model provides $\kappa_t< 2$, and for the standard model value $\Gamma_{h\to gg}(\kappa_t)$ is suppressed by 9% as compared to $\kappa_t= 2$. We further show that in the leading order $\Gamma_{h\to gg}$ for $\kappa_t\simeq \pm 1.2$ can be very small due to complete cancelation between the top and bottom quark fluctuations. We discuss the extension of our results to $\kappa_t>2$ and consider potential paths to obtain experimental information for the $h\to gg$ rate.Comment: 4 pages, 3 figures, elsarticle format, v2 added section "Gluon Fusion into Higgs

Pair Production from Asymmetric Head-on Laser Collisions

We evaluate particle production in highly asymmetric head-on collisions of lasers pulses due to non-perturbative coherent action of many photons. We obtain the yield of electron-positron pairs, which is controlled by the photon content of the weaker pulse, and show that the wavelength of the weaker pulse and the momentum asymmetry determine laboratory energy of the produced particles.Comment: 4 pages, 1 figur

Enhanced nonperturbative photon-pair conversion in small-angle laser collisions

We show a new scheme of nonperturbative pair production by high energy photons ($\omega\gtrsim m$) in a strong external field is achievable at the next high intensity laser experiments. The pair momentum is boosted and for $\omega\gtrsim 1.2m$ the pair yield is increased when the external field is formed by two laser pulses converging at a small angle. These characteristics are nonperturbative in origin and related to the presence of magnetic field in addition to electric field. By enhancing the signal over perturbative backgrounds, these features allow the employment of above-threshold photons $\omega>2m$, which further increases the pair yield. We note the close relation of this photon-pair conversion mechanism to spontaneous pair creation, recommending it as an accessible stepping stone experiment using state-of-the-art or soon-to-be laser technology.Comment: 5 pages, 2 figures, revtex forma

Planetary Impacts by Clustered Quark Matter Strangelets

We propose a model of clustered u-d-s quark matter that leads to stable bulk strange quark matter. We discuss qualitatively consequences of impacts by sub-planetary mass strangelets on rocky solar system bodies.Comment: 6 pages, 1 figure, SQM 2011 Proceeding

Effective Field Theory of Broken Spatial Diffeomorphisms

We study the low energy effective theory describing gravity with broken spatial diffeomorphism invariance. In the unitary gauge, the Goldstone bosons associated with broken diffeomorphisms are eaten and the graviton becomes a massive spin-2 particle with 5 well-behaved degrees of freedom. In this gauge, the most general theory is built with the lowest dimension operators invariant under only temporal diffeomorphisms. Imposing the additional shift and SO(3) internal symmetries, we analyze the perturbations on a FRW background. At linear perturbation level, the observables of this theory are characterized by five parameters, including the usual cosmological parameters and one additional coupling constant for the symmetry-breaking scalars. In the de Sitter and Minkowski limit, the three Goldstone bosons are supermassive and can be integrated out, leaving two massive tensor modes as the only propagating degrees of freedom. We discuss several examples relevant to theories of massive gravity.Comment: 26 pages, V2 more references, several remarks and a new subsection are added, V3 a major revision, with two new subsections added, as well as several new discussions on the construction of our EF