8,774 research outputs found
Single top polarisation as a window to new physics
We discuss the effect of heavy new physics, parameterised in terms of
four-fermion operators, in the polarisation of single top (anti-)quarks in the
-channel process at the LHC. It is found that for operators involving a
right-handed top quark field the relative effect on the longitudinal
polarisation is twice larger than the relative effect on the total cross
section. This enhanced dependence on possible four-fermion contributions makes
the polarisation measurements specially interesting, in particular at high
momenta.Comment: LaTeX 10 pages. v2: comments and references added, journal versio
Top effective operators at the ILC
We investigate the effect of top trilinear operators in t tbar production at
the ILC. We find that the sensitivity to these operators largely surpasses the
one achievable by the LHC either in neutral or charged current processes,
allowing to probe new physics scales up to 4.5 TeV for a centre of mass energy
of 500 GeV. We show how the use of beam polarisation and an eventual energy
upgrade to 1 TeV allow to disentangle all effective operator contributions to
the Ztt and gamma tt vertices.Comment: LaTeX 13 pages. Typos corrected. Final version in JHE
Top effective operators at the ILC
We investigate the effect of top trilinear operators in t tbar production at
the ILC. We find that the sensitivity to these operators largely surpasses the
one achievable by the LHC either in neutral or charged current processes,
allowing to probe new physics scales up to 4.5 TeV for a centre of mass energy
of 500 GeV. We show how the use of beam polarisation and an eventual energy
upgrade to 1 TeV allow to disentangle all effective operator contributions to
the Ztt and gamma tt vertices.Comment: LaTeX 13 pages. Typos corrected. Final version in JHE
Optimal quantum state reconstruction for cold trapped ions
We study the physical implementation of an optimal tomographic reconstruction
scheme for the case of determining the state of a multi-qubit system, where
trapped ions are used for defining qubits. The protocol is based on the use of
mutually unbiased measurements and on the physical information described in H.
H\"{a}ffner \emph{et. al} [Nature \textbf{438}, 643-646 (2005)]. We introduce
the concept of physical complexity for different types of unbiased measurements
and analyze their generation in terms of one and two qubit gates for trapped
ions.Comment: Accepted for publication in Phys. Rev. A as Rap. Com
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