1,082 research outputs found
Discrete regularisation of localised kinetic terms
We investigate the behaviour of 5d models with general brane kinetic terms by
discretising the extra dimension. We show that in the continuum limit the
Kaluza-Klein masses and wave functions are in general nonanalytic in the
coefficients of brane terms.Comment: Presented at the 7th DESY Workshop on Elementary Particle Theory
``Loops and Legs in Quantum Field Theory'', Zinnowitz, April 25-30, 200
Impact of extra particles on indirect Z' limits
We study the possibility of relaxing the indirect limits on extra neutral
vector bosons by their interplay with additional new particles. They can be
systematically weakened, even below present direct bounds at colliders, by the
addition of more vector bosons and/or scalars designed for this purpose.
Otherwise, they appear to be robust.Comment: Latex 23 pages, 8 eps figures. Minor changes, version published in
Phys. Rev.
Reconstruction of the Extended Gauge Structure from Observables at Future Colliders
The discovery of a new neutral gauge boson with a mass in the TeV region
would allow for determination of gauge couplings of the to ordinary quarks
and leptons in a model independent way. We show that these couplings in turn
would allow us to determine the nature of the extended gauge structure. As a
prime example we study the group. In this case two discrete constraints
on experimentally determined couplings have to be satisfied. If so, the
couplings would then uniquely determine the two parameters, and
, which fully specify the nature of the within . If the
is part of the gauge structure, then for TeV and
could be determined to around at the future colliders. The NLC
provides a unique determination of the two constraints as well as of and , though with slightly larger error bars than at the LHC. On
the other hand, since the LHC primarily determines three out of four normalized
couplings, it provides weaker constraints for the underlying gauge structure.Comment: 14 pages LaTeX using RevTeX and psfig.sty. TeX source and 3 PS
figures, tarred, compressed and uuencoded; also available via anonymous ftp
to ftp://dept.physics.upenn.edu/pub/Cvetic/UPR-636-T
Low energy constraints on orbifold models
We review the low energy limits on Kaluza-Klein excitations in orbifold
models. New vector-like quarks, as well as new Z' gauge bosons, can be
accommodated with masses observable at large colliders.Comment: Presented at RADCOR 2002, to appear in the proceeding
Top mixing in effective theories
We review how top mixing with light quarks constrains new physics beyond the
Standard Model using the effective Lagrangian approach.Comment: 4 pages, contribution to Workshop "Loops and Legs in Quantum Field
Theory", April 200
The Minimal Extension of the SM and the Neutrino Oscillation Data
We study the simplest Standard Model estension with only one extra
right-handed neutrino. In this case there are two massless and two
massive neutrinos, and in principle both solar and atmospheric
anomalies can be described in two different scenarios, (scheme I)
and (scheme II). However, neither bi-maximal mixing nor the
dark matter problem are explained in this minimal extension. Only scheme II can
accommodate simultaneously maximal mixing for atmospheric neutrinos and the
small mixing angle MSW solution for the solar anomaly. This scenario can be
tested in the BOREXINO experiment.Comment: 9 pages, Presented by J. Gluza at the XXIII School of Theoretical
Physics, Ustron'99, Poland, September 15-22, 199
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.
Evidence for right-handed neutrinos at a neutrino factory
We emphasize that a muon based neutrino factory could show the existence of
light right-handed neutrinos, if a deficit in the number of detected events is
observed at a near detector. This could be as large as ~10% if the size of the
new interactions saturates the present limits from electroweak precision data,
what is not excluded by the oscillation experiments performed up to now. A
simple model realizing such a scenario can be obtained adding right-handed
neutrinos to the minimal Standard Model, together with an extra scalar doublet
and a triplet of hypercharge 1. In this case, however, the possible deficit is
reduced by a factor of ~3, and the Yukawa couplings must be adequately chosen.
This is also generically required if lepton flavour violation must be below
present bounds.Comment: Latex 18 pages, 2 eps figure
Neutrino oscillations beyond the Standard Model
We address the possible impact of New Physics on neutrino oscillation
experiments. This can modify the neutrino production, propagation and/or
detection, making the full cross section non-factorizable in general. Thus, for
example, the neutrino flux may not be properly described assuming an unitary
MNS matrix and/or neutrinos may propagate differently depending of their Dirac
or Majorana character. Interestingly enough, present limits on New Physics
still allow for observable effects at future neutrino experiments.Comment: 2 pages, 2 figures, Presented at the Neutrino 08 Conference,
Christchurch, New Zealand, May 25-31, 200
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