376 research outputs found
Higgs two-gluon decay and the top-quark chromomagnetic moment
We study the top quark chromomagnetic factor -dependence of the
effective interaction and apply the result to the case of
Higgs two gluon decay rate . Perturbative standard model
provides , and for the standard model value is suppressed by 9% as compared to . We further
show that in the leading order for
can be very small due to complete cancelation between the top and bottom quark
fluctuations. We discuss the extension of our results to and
consider potential paths to obtain experimental information for the
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 () in a strong external field is achievable at the
next high intensity laser experiments. The pair momentum is boosted and for
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
, 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
- âŠ