19,375 research outputs found
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
The minimal stealth boson: models and benchmarks
Stealth bosons are relatively light boosted particles with a cascade decay , reconstructed as a single fat jet. In this
work, we establish minimal extensions of the Standard Model that allow for such
processes. Namely, we consider models containing a new (leptophobic) neutral
gauge boson and two scalar singlets, plus extra matter required to cancel
the anomalies. Our analysis shows that, depending on the model
and benchmark scenario, the expected statistical significance of stealth boson
signals (yet uncovered by current searches at the Large Hadron Collider) is up
to nine times larger than for the most sensitive of the standard leptophobic
signals such as dijets, pairs or dibosons. These results
provide strong motivation for model-independent searches that cover these
complex signals.Comment: LaTeX 39 pages. Additional comments. Bug corrected, final version in
JHE
Multilepton production via top flavour-changing neutral couplings at the CERN LHC
Zt and gamma t production with Z -> l+ l- and t -> Wb -> l nu b provides the
best determination of top flavour-changing neutral couplings at the LHC. The
bounds on tc couplings eventually derived from these processes are similar to
those expected from top decays, while the limits on tu couplings are better by
a factor of two. The other significant Z and W decay modes are also
investigated.Comment: 30 pages, 23 PS figures. Uses epsfig.sty and elsart.sty. Added some
references and corrected some typos. Added more comments about statistics.
Using elsart.sty reduces the size to 30 pages. Published in Nucl. Phys.
Multiphoton signals of a (96 GeV?) stealth boson
Cascade decays of new scalars into final states with multiple photons and
possibly quarks may lead to distinctive experimental signatures at high-energy
colliders. Such signals are even more striking if the scalars are highly
boosted, as when produced from the decay of a much heavier resonance. We study
this type of events within the framework of the minimal stealth boson model, an
anomaly-free extension of the Standard Model with two
complex scalar singlets. It is shown that, while those signals may have cross
sections that might render them observable with LHC Run 2 data, they have
little experimental coverage. We also establish a connection with a CMS excess
observed in searches for new scalars decaying into diphoton final states near
96 GeV. In particular, we conclude that the predicted multiphoton signatures
are compatible with such excess.Comment: LaTeX 32 pages. Comments added and discussions extended. Final
version in EPJ
A closer look at the possible CMS signal of a new gauge boson
The CMS collaboration has recently reported a 2.8 excess of
events with an invariant mass around 2 TeV. This observation can be explained
in the context of standard model extensions with new gauge bosons ,
and heavy neutrinos coupling (mainly) to the electron. We discuss additional
signals that allow to confirm or discard the and hypotheses.Comment: ReVTeX 5 page
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