198,428 research outputs found
Accurate determination of the scattering length of metastable Helium atoms using dark resonances between atoms and exotic molecules
We present a new measurement of the s-wave scattering length a of
spin-polarized helium atoms in the 2^3S_1 metastable state. Using two-photon
photoassociation spectroscopy and dark resonances we measure the energy
E_{v=14}= -91.35 +/- 0.06 MHz of the least bound state v=14 in the interaction
potential of the two atoms. We deduce a value of a = 7.512 +/- 0.005 nm, which
is at least one hundred times more precise than the best previous
determinations and is in disagreement with some of them. This experiment also
demonstrates the possibility to create exotic molecules binding two metastable
atoms with a lifetime of the order of 1 microsecond.Comment: 4 pages, 4 figure
Hierarchical Mass Structure of Fermions in Warped Extra Dimension
The warped bulk standard model has been studied in the Randall-Sundrum
background on interval with the bulk gauge symmetry
. With the assumption of no
large cancellation between the fermion flavor mixing matrices, we present a
simple analytic method to determine the bulk masses of standard model fermions
in the almost universal bulk Yukawa coupling model. We also predict
element of MNS matrix to be near the experimental upper bound when the neutrino
masses are of Dirac type.Comment: 16 page
decays and twisted boundary conditions
We propose a new method to evaluate the Lellouch-L\"uscher factor which
relates the matrix elements computed on a finite
lattice to the physical (infinite-volume) decay amplitudes. The method relies
on the use of partially twisted boundary conditions, which allow the s-wave
phase shift to be computed as an almost continuous function of the
centre-of-mass relative momentum and hence for its derivative to be evaluated.
We successfully demonstrate the feasibility of the technique in an exploratory
computation.Comment: 19 pages, 7 figure
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