69 research outputs found
Neutral Higgs boson pair production at the LC in the Noncommutative Standard Model
We study the Higgs boson pair production through collision in the
noncommutative(NC) extension of the standard model using the Seiberg-Witten
maps of this to the first order of the noncommutative parameter . This process is forbidden in the standard model with background
space-time being commutative. We find that the cross section of the pair
production of Higgs boson (of intermediate and heavy mass) at the future Linear
Collider(LC) can be quite significant for the NC scale lying in the
range TeV. Finally, using the direct experimental(LEP II, Tevatron
and global electro-weak fit) bound on Higgs mass, we obtain bounds on the NC
scale as 665 GeV GeV.Comment: 14 pages, 8 figure
Resonances and Unitarity in Weak Boson Scattering at the LHC
A crucial test of the Standard Model is the measurement of electroweak
gauge-boson scattering. In this paper, we describe a generic parameterization
aimed at a realistic simulation of weak-boson scattering at the LHC. The
parameterization implements resonances of all possible spin and isospin
combinations, properly matched to the low-energy effective (chiral) Lagrangian,
includes leading higher-order effects and contains a minimal unitarization
scheme. We implement the parameterization in the Monte-Carlo event generator
WHIZARD and present results for complete partonic cross-section integration and
event generation. We provide a comparison with the effective W approximation
that previously has been used for most WW scattering studies at hadron
colliders.Comment: 49 pages, 15 figure
Probing the Noncommutative Standard Model at Hadron Colliders
We study collider signals for the noncommutative extension of the standard
model using the Seiberg-Witten maps for SU(3)_C x SU(2)_L x U(1)_Y to first
order in the noncommutativity parameters theta_munu. In particular, we
investigate the ensitivity of Z-gamma-production at the Tevatron and the LHC to
the components of theta_munu. We discuss the range of validity of this
approximation and estimate exclusion limits from a Monte Carlo simulation.Comment: 18 pages LaTeX, 23 figures. Slightly expanded introduction and
additional references. Accepted for publication in Physical Review
Non-commutative SU(N) gauge theories and asymptotic freedom
In this paper we analyze the one-loop renormalization of the
-expanded Yang-Mills theory. We show that the {\it freedom
parameter} , key to renormalization, originates from higher order
non-commutative gauge interaction, represented by a higher derivative term . The renormalization condition fixes the allowed values of the
parameter to one of the two solutions: or , i.e. to or to
, respectively. When the higher order interaction is switched on,
(), pure non-commutative SU(N) gauge theory at first order in
-expansion becomes one-loop renormalizable for various representations
of the gauge group. We also show that, in the case and the adjoint
representation of the gauge fields, the non-commutative deformation parameter
has to be renormalized and it is asymptotically free.Comment: 16 pages, no figure
Renormalisability of the matter determinants in noncommutative gauge theory in the enveloping-algebra formalism
We consider noncommutative gauge theory defined by means of Seiberg-Witten
maps for an arbitrary semisimple gauge group. We compute the one-loop UV
divergent matter contributions to the gauge field effective action to all
orders in the noncommutative parameters . We do this for Dirac fermions
and complex scalars carrying arbitrary representations of the gauge group. We
use path-integral methods in the framework of dimensional regularisation and
consider arbitrary invertible Seiberg-Witten maps that are linear in the matter
fields. Surprisingly, it turns out that the UV divergent parts of the matter
contributions are proportional to the noncommutative Yang-Mills action where
traces are taken over the representation of the matter fields; this result
supports the need to include such traces in the classical action of the gauge
sector of the noncommutative theory.Comment: 7 page
Renormalizability and Phenomenology of theta-expanded Noncommutative Gauge Field Theory
In this article we consider theta-expanded noncommutative gauge field theory,
constructed at the first order in noncommutative parameter theta, as an
effective, anomaly free theory, with one-loop renormalizable gauge sector.
Related phenomenology with emphasis on the standard model forbidden decays, is
discussed. Experimental possibilities of Z -> gamma gamma decay are analyzed
and a firm bound to the scale of the noncommutativity parameter is set around
few TeV's.Comment: 10 page
Yukawa couplings and seesaw neutrino masses in noncommutative gauge theory
We consider Yukawa couplings in a theta-exact approach to noncommutative
gauge field theory and show that both Dirac and singlet Majorana neutrino mass
terms can be consistently accommodated. This shows that in fact the whole
neutrino-mass extended standard model on noncommutative spacetime can the
formulated in the new nonperturbative (in theta) approach which eliminates the
previous restriction of Seiberg-Witten map based theories to low-energy
phenomena. Spacetime noncommutativity induced couplings between neutrinos and
photons as well as Z-bosons appear quite naturally in the model. We derive
relevant Feynman rules for the type I seesaw mechanism.Comment: 10 pages, version to be published in Physics Letters
What if the Higgs couplings to W and Z bosons are larger than in the Standard Model?
We derive a general sum rule relating the Higgs coupling to W and Z bosons to
the total cross section of longitudinal gauge boson scattering in I=0,1,2
isospin channels. The Higgs coupling larger than in the Standard Model implies
enhancement of the I=2 cross section. Such an enhancement could arise if the
Higgs sector is extended by an isospin-2 scalar multiplet including a doubly
charged, singly charged, and another neutral Higgs.Comment: 11 pages, no figures. v2: comments and references added. v3: early
QCD references adde
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