620 research outputs found
A Simple Method to detect spontaneous CP Violation in multi-Higgs models
For models with several Higgs doublets we present an alternative method to
the one proposed by Branco, Gerard and Grimus, in 1984, to check whether or not
CP is spontaneously violated in the Higgs potential. The previous method is
powerful and rigorous. It requires the identification of a matrix
corresponding to a symmetry of the Lagrangian and verifying a simple relation
involving the vacuum expectation values. The nonexistence of such a matrix
signals spontaneous CP violation. However, as the number of Higgs doublets
increases, finding such a matrix may not be straightforward and it may turn
out to be easier to analyse the potential by going to the so-called Higgs
basis. The transformation to the Higgs basis is straightforward once the vacuum
expectation values are known. The method proposed in this work is also powerful
and rigorous and can be particularly useful to analyse models with more than
two Higgs doublets and with continuous symmetries.Comment: 9 pages, no figures. v2: minor changes, matching JHEP versio
Diagnosing CP properties of the 2HDM
We have investigated a Two-Higgs-Doublet Model (2HDM), focusing on CP
violation. Various scenarios with spontaneous and explicit breaking of CP have
been considered. Some features of CP violation related to a choice of the basis
for the two Higgs doublets have been discussed and clarified. Regions in the
physical parameter space corresponding to spontaneous and explicit CP violation
have been located and discussed. The possibility to determine parameters of the
scalar potential with no reference to Yukawa couplings has been considered and
an unavoidable ambiguity has been found. The issue of disentangling spontaneous
and explicit CP violation has been investigated.Comment: 32 pages, 5 figures. Minor changes. Version to appear in JHE
Measuring CP violation in Two-Higgs-Doublet models in light of the LHC Higgs data
In Two-Higgs-Doublet models, the conditions for CP violation can be expressed
in terms of invariants under U(2) rotations among the two SU(2) Higgs doublet
fields. In order to design a strategy for measuring the invariants we express
them in terms of observables, i.e., masses and couplings of scalar bosons. We
find amplitudes directly sensitive to the invariants. Observation of the
Standard-Model-like Higgs boson at the LHC severely constrains the models. In
particular, in the model with Z_2 symmetry imposed on dimension-4 terms (in
order to eliminate tree-level flavour-changing neutral currents), CP violation
is strongly suppressed. On the other hand, the most general Two-Higgs-Doublet
model (without Z_2 symmetry) would still allow for CP violation to be present
in the model, without being in conflict with the LHC data. Consequently, also
flavour-changing neutral currents would in general be expected. We briefly
sketch a strategy for measuring the remaining CP violation.Comment: 26 pages, 7 figures. Version published in JHE
Testing the presence of CP violation in the 2HDM
We review CP properties of the Two-Higgs-Doublet model. In particular, we
show that spontaneous CP violation occurs in the parameter space on the border
between regions allowing explicit CP violation and those where there is another
minimum, deeper than the one corresponding to v=246 GeV. We discuss weak-basis
invariants which describe CP violation and express them through measurable
quantities like coupling constants and masses. Also, we discuss how CP
violation is constrained by the LHC Higgs data. Finally, we identify effective
operators that could be adopted to measure CP-invariants.Comment: 9 pages, Proceedings of the Corfu Summer Institute 2014 "School and
Workshops on Elementary Particle Physics and Gravity", 3-21 September 2014
Corfu, Greece. v2: References adde
Housing prices and multiple employment nodes: is the relationship nonmonotonic?
Standard urban economic theory predicts that house prices will decline with distance from the central business district. Empirical results have been equivocal, however. Disjoints between theory and empirics may be due to a nonmonotonic relationship between house prices and access to employment arising from the negative externalities associated with proximity to multiple centres of employment. Based on data from Glasgow (Scotland), we use gravity-based measures of accessibility estimated using a flexible functional form that allows for nonmonotonicity. The results are thoroughly tested using recent advances in spatial econometrics. We find compelling evidence of a nonmonotonic effect in the accessibility measure and discuss the implications for planning and housing policy
Update on the CP-Violating Inert-Doublet Model
We have updated a recently proposed extension of the Inert Doublet Model. The
extension amounts to the addition of an extra non-inert scalar doublet. The
model thus offers a possibility of CP violation in the scalar sector and a
candidate for the Dark Matter. The recent XENON100 direct-detection experiment
excludes a considerable range of medium-low dark-matter masses, leaving only as
viable very low masses of order 5-10 GeV, as well as the regions from \sim 60
to \sim 110 GeV, and above \sim 530 GeV. For favorable parameter regions one
may observe related long-lived charged particles produced at the LHC.Comment: Contribution to PoS Proceedings, The XXth International Workshop High
Energy Physics and Quantum Field Theory, September 24 - October 1, 2011,
Sochi, Russi
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