23 research outputs found
Rare decay Z --> neutrino antineutrino photon photon via quartic gauge boson couplings
We present a detailed calculation of the rare decay Z --> neutrino
antineutrino photon photon via the quartic neutral gauge boson coupling
Z-Z-photon-photon in the framework of the effective Lagrangian approach. The
current experimental bound on this decay mode is then used to constrain the
coefficients of this coupling. It is found that the bounds obtained in this
way, of the order of , are weaker than the ones obtained from the
analysis of triple-boson production at LEP-2Comment: 5 pages, 2 figures, to appear in Physical Review D Brief Report
Bosonic Quartic Couplings at LHC
We analyze the potential of the CERN Large Hadron Collider (LHC) to study
anomalous quartic vector-boson interactions Z Z gamma gamma, Z Z Z gamma, W+ W-
gamma gamma, and W+ W- Z gamma through the weak boson fusion processes q q -> q
q gamma gamma and q q -> q q gamma Z(-> l+ l-) with l = electron or muon. After
a careful study of the backgrounds and how to extract them from the data, we
show that the process p p -> j j gamma l+ l- is potentially the most sensitive
to deviations from the Standard Model, improving the sensitivity to anomalous
couplings by up to a factor 10^4 (10^2) with respect to the present direct
(indirect) limits.Comment: 18 pages, 2 figures, revised versio
Scrutinizing the ZW+W- vertex at the Large Hadron Collider at 7 TeV
We analyze the potential of the CERN Large Hadron Collider running at 7 TeV
to search for deviations from the Standard Model predictions for the triple
gauge boson coupling ZW+W- assuming an integrated luminosity of 1 fb^{-1}. We
show that the study of W+W- and W^\pm Z productions, followed by the leptonic
decay of the weak gauge bosons can improve the present sensitivity on the
anomalous couplings \Delta g_1^Z, \Delta \kappa_Z, \lambda_Z, g_4^Z, and
\tilde{\lambda}_Z at the 2\sigma level.Comment: 12 pages, 3 figures. One reference added, matches published versio
Quartic Gauge Couplings and the Radiation Zero in pp to l nu gamma gamma events at the LHC
We report a study of the process pp to l nu gamma gamma at CERN's Large
Hadron Collider, using a leading order partonic-level event generator
interfaced to the Pythia program for showering and hadronisation and a with a
generic detector simulation. The process is sensitive to possible anomalous
quartic gauge boson couplings of the form W W gamma gamma. It is shown how
unitarity-safe limits may be placed on these anomalous couplings by applying a
binned maximum likelihood fit to the distribution of the two-photon invariant
mass, M(gamma gamma), below a cutoff of 1TeV. Assuming 30fb-1 of integrated
luminosity, the expected limits are two orders of magnitude tighter than those
available from LEP. It is also demonstrated how the Standard Model radiation
zero feature of the qq to W gamma gamma process may be observed in the
difference between the two-photon and charged lepton pseudo-rapidities.Comment: 9 pages, 7 figure
Bhabha Scattering with Radiated Gravitons at Linear Colliders
We study the process e+- e- -> e+- e- +- missing energy at a high-energy e+-
e- collider, where the missing energy arises from the radiation of Kaluza-Klein
gravitons in a model with large extra dimensions. It is shown that at a
high-energy linear collider, this process can not only confirm the signature of
such theories but can also sometimes be comparable in effectiveness to the
commonly discussed channel e+- e- -> gamma +- missing energy, especially for a
large number of extra dimensions and with polarized beams. We also suggest some
ways of distinguishing the signals of a graviton tower from other types of new
physics signals by combining data on our suggested channel with those on the
photon-graviton channel.Comment: 16 pages, LaTex, 8 figures embedded, typos, report no and references
correcte
Optical Activity From Extra Dimension
Optical activity, like Faraday effect, is a rotation of the plane of
polarization of propagating light in a medium and can be attributed to
different sources with distinct signatures. In this note we discuss the effect
of optical activity {\it{in vacuum}} due to Kaluza-Klein scalar field ,
in the presence of an external electro-magnetic field. The astrophysical
implication of this effect is indicated. We also point out the possibility of
observing the same in laboratory conditions.Comment: Four Page
Electrostatic self-energy and Bekenstein entropy bound in the massive Schwinger model
We obtain the electrostatic energy of two opposite charges near the horizon
of stationary black-holes in the massive Schwinger model. Besides the confining
aspects of the model, we discuss the Bekenstein entropy upper bound of a
charged object using the generalized second law. We show that despite the
massless case, in the massive Schwinger model the entropy of the black hole and
consequently the Bekenstein bound are altered by the vacuum polarization.Comment: 14 pages, accepted for publication in "Gen. Rel. Grav. (2005)
Weak Boson Production Amplitude Zeros; Equalities of the Helicity Amplitudes
We investigate the radiation amplitude zeros exhibited by many Standard Model
amplitudes for triple weak gauge boson production processes. We show that
production amplitudes have especially rich structure in terms of
zeros, these amplitudes have zeros originating from several different sources.
It is also shown that TYPE I current null zone is the special case of the
equality of the specific helicity amplitudes.Comment: 27 pages, 12 figures, 2 table
Invisible Higgs Boson Decay into Massive Neutrinos of 4th Generation
Results from several recent experiments provide inderect evidences in the
favor of existence of a 4th generation neutrino. Such a neutrino of mass about
50 GeV is compatible with current physical and astrophysical constraints and
well motivated in the framework of superstring phenomenology. If sufficiently
stable the existence of such a neutrino leads to the drastic change of Higgs
boson physics: for a wide range of Higgs boson masses the dominant mode of
Higgs boson decay is invisible and the branching ratios for the most promising
modes of Higgs boson search are significantly reduced. The proper strategy of
Higgs boson searches in such a framework is discussed. It is shown that in the
same framework the absence of a signal in the search for invisible Higgs boson
decay at LEP means either that the mass of Higgs is greater than 113.5 GeV or
that the mass difference between the Higgs mass and doubled neutrino mass is
small.Comment: 8 pages, 2 figure
One-Loop Renormalization of a Self-Interacting Scalar Field in Nonsimply Connected Spacetimes
Using the effective potential, we study the one-loop renormalization of a
massive self-interacting scalar field at finite temperature in flat manifolds
with one or more compactified spatial dimensions. We prove that, owing to the
compactification and finite temperature, the renormalized physical parameters
of the theory (mass and coupling constant) acquire thermal and topological
contributions. In the case of one compactified spatial dimension at finite
temperature, we find that the corrections to the mass are positive, but those
to the coupling constant are negative. We discuss the possibility of
triviality, i.e. that the renormalized coupling constant goes to zero at some
temperature or at some radius of the compactified spatial dimension.Comment: 16 pages, plain LATE