12,690 research outputs found

### A Twisted Custodial Symmetry in the Two-Higgs-Doublet Model

In the Standard Model for electroweak interactions, the Higgs sector is known
to display a "custodial" symmetry protecting the mass relation
m_{W^\pm}^2=m_{W_3}^2 from large corrections. When considering extensions of
the scalar sector, this symmetry has to be introduced by hand in order to pass
current electroweak precision tests in a natural way. In this Letter we
implement a generalized custodial symmetry in the two-Higgs-doublet model.
Assuming the invariance of the potential under CP transformations, we prove the
existence of a new custodial scenario characterized by m_{H^\pm}^2=m_{H^0}^2
instead of m_{H^\pm}^2=m_{A^0}^2. Consequently the pseudoscalar A^0 may be much
lighter than the charged H^\pm, giving rise to interesting phenomenology.Comment: 4 pages, RevTeX

### The observable light deflection angle

The physical deflection angle of a light ray propagating in a space-time
supplied with an asymptotically flat metric has to be expressed in terms of the
impact parameter.Comment: 11 pages, 1 figur

### A theoretical determination of the eta-eta' mixing

The systematic large N_c limit within chiral perturbation provides an optimal
eta-eta' mixing angle of about -27 degrees at leading order in p^2. In this
frame, agreement with the data can be reached with higher order corrections of
about 20%.Comment: 12 pages, 2 figures; reference to the two-mixing-angle scheme added,
minor corrections; to appear in JHE

### Tests for the asymptotic behaviour of the gamma^* --> gamma pi^0 form factor

The gamma^* --> gamma pi^0 transition measured at different photon
virtualities already provides us with a clean test for the behaviour of the
pi^0 gamma^* gamma off-shell axial anomaly at large time-like squared momenta.
It also allows reliable predictions for the branching ratio of heavy quarkonium
decays into omega pi^0.Comment: Latex, 7 pages + 1 .ps figure, comments on the Brodsky-Lepage limit
and 5 new references adde

### A model for the dynamics of extensible semiflexible polymers

We present a model for semiflexible polymers in Hamiltonian formulation which
interpolates between a Rouse chain and worm-like chain. Both models are
realized as limits for the parameters. The model parameters can also be chosen
to match the experimental force-extension curve for double-stranded DNA. Near
the ground state of the Hamiltonian, the eigenvalues for the longitudinal
(stretching) and the transversal (bending) modes of a chain with N springs,
indexed by p, scale as lambda_lp ~ (p/N)^2 and lambda_tp ~ p^2(p-1)^2/N^4
respectively for small p. We also show that the associated decay times tau_p ~
(N/p)^4 will not be observed if they exceed the orientational time scale tau_r
~ N^3 for an equally-long rigid rod, as the driven decay is then washed out by
diffusive motion.Comment: 28 pages, 2 figure

### Assessing intonation skills in a tertiary music training programme

[Abstract]: Buttsworth, Fogarty, and Rorke (1993) reported the construction of a battery of tonal
tests designed to assess intonation abilities. A subset of the tests in the battery
predicted 36 per cent of final scores in an aural training subject in a tertiary music course. In
the current study, the original battery of fourteen tests was reduced to six tests and
administered three times throughout the academic year to a new sample (N = 87) of
tertiary music students. Three research questions were investigated. Firstly, it was
hypothesised that tests in the battery would discriminate among the different aural
classes at USQ, which were grouped according to ability level. The results from
discriminant function analyses provided strong support for this hypothesis. Secondly,
it was hypothesised that students should improve their performance on the pitch
battery across the three administrations. A repeated measures analysis of variance
failed to find evidence of overall improvement. Finally, it was hypothesised that there
would be significant differences on the intonation tests between musicians of different
instrumental families. Again, no overall differences were found. The results indicated
that intonation tests appear to tap an ability that (a) is not significantly modified by
training, (b) is more or less the same across different instrument families, and (c) is
related to success in music training programmes

### TOP-INDUCED ELECTROWEAK BREAKING IN THE MINIMAL SUPERSYMMETRIC STANDARD MODEL

Severe constraints on parameters of the minimal supersymmetric standard model
follow from a dynamical electroweak symmetry breaking mechanism dominated by
top and stop loops. In particular, the lightest Higgs boson mass is expected to
be smaller than 100 GeV.Comment: 10 pages, Latex, 6 Postcript Figure

### Anomalous enhancement of a penguin hadronic matrix element in B->K eta'

We estimate the density matrix element for the pi^0, eta and eta' production
from the vacuum in the large-N_c limit. As a consequence, we find that the QCD
axial anomaly leads to highly non-trivial corrections to the usual flavour
SU(3) relations between B^0-> K^0 pi^0, B^0-> K^0 eta and B^0-> K^0 eta' decay
amplitudes. These corrections may explain why the B-> K eta' branching ratio is
about six times larger than the B-> K pi one.Comment: 5 pages, 1 figur

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