3,661 research outputs found
The dyon charge in noncommutative gauge theories
We present an explicit classical dyon solution for the noncommutative version
of the Yang-Mills-Higgs model (in the Prasad-Sommerfield limit) with a tehta
term. We show that the relation between classical electric and magnetic charges
also holds in noncommutative space. Extending the Noether approach to the case
of a noncommutative gauge theory, we analyze the effect of CP violation at the
quantum level, induced both by the theta term and by noncommutativity and we
prove that the Witten effect formula for the dyon charge remains the same as in
ordinary space.Comment: 17 page
Beyond the Standard Model for Montaneros
These notes cover (i) electroweak symmetry breaking in the Standard Model
(SM) and the Higgs boson, (ii) alternatives to the SM Higgs boson including an
introduction to composite Higgs models and Higgsless models that invoke extra
dimensions, (iii) the theory and phenomenology of supersymmetry, and (iv)
various further beyond topics, including Grand Unification, proton decay and
neutrino masses, supergravity, superstrings and extra dimensions.Comment: Based on lectures by John Ellis at the 5th CERN-Latin-American School
of High-Energy Physics, Recinto Quirama, Colombia, 15 - 28 Mar 2009, 84
pages, 35 figure
When Big Isn’t Better: Why Smaller International Initial Public Offering Firms Seem to Win
There is a considerable amount of research suggesting that “being international” is better. While that may be the case, the assumption remains tenuous at best, and research that considers organizational size provides results contesting this assumption. In particular, we explore the effect of having international sales and operations on both long and short-term performance of initial public offering (IPO) firms. We also explore the “size” phenomenon evident in prior research that suggests smaller firms seem to perform better when they are international than do medium size firms. By applying work from the field of human resource management, we suggest that the ‘size’ phenomenon may be related to the level of structural cohesion in the organization. Our longitudinal study supports the hypothesis that international companies with higher levels of structural cohesion are more successful
The Dyon Charge in Noncommutative Gauge Theories
We construct a dyon solution for the noncommutative version of the Yang-Mills-Higgs model with a ϑ-term. Extending the Noether method to the case of a noncommutative gauge theory, we analyze the effect of CP violation induced both by the ϑ- term and by noncommutativity proving that theWitten effect formula for the dyon charge remains the same as in ordinary space.Facultad de Ciencias Exacta
Vector boson production at hadron colliders: a fully exclusive QCD calculation at NNLO
We consider QCD radiative corrections to the production of W and Z bosons in
hadron collisions. We present a fully exclusive calculation up to
next-to-next-to-leading order (NNLO) in QCD perturbation theory. To perform
this NNLO computation, we use a recently proposed version of the subtraction
formalism. The calculation includes the gamma-Z interference, finite-width
effects, the leptonic decay of the vector bosons and the corresponding spin
correlations. Our calculation is implemented in a parton level Monte Carlo
program. The program allows the user to apply arbitrary kinematical cuts on the
final-state leptons and the associated jet activity, and to compute the
corresponding distributions in the form of bin histograms. We show selected
numerical results at the Tevatron and the LHC.Comment: 7 pages, 3 ps figure
Universality of transverse-momentum resummation and hard factors at the NNLO
We consider QCD radiative corrections to the production of colourless
high-mass systems in hadron collisions. The logarithmically-enhanced
contributions at small transverse momentum are treated to all perturbative
orders by a universal resummation formula that depends on a single
process-dependent hard factor. We show that the hard factor is directly related
to the all-order virtual amplitude of the corresponding partonic process. The
direct relation is universal (process independent), and it is expressed by an
all-order factorization formula that we explicitly evaluate up to the
next-to-next-to-leading order (NNLO) in QCD perturbation theory. Once the NNLO
scattering amplitude is available, the corresponding hard factor is directly
determined: it controls NNLO contributions in resummed calculations at full
next-to-next-to-leading logarithmic accuracy, and it can be used in
applications of the q_T subtraction formalism to perform fully-exclusive
perturbative calculations up to NNLO. The universality structure of the hard
factor and its explicit NNLO form are also extended to the related formalism of
threshold resummation.Comment: References added. Version accepted for publication on NP
Threshold resummation at NLL accuracy and soft-virtual cross sections at NLO
We consider QCD radiative corrections to the production of colourless
high-mass systems in hadron collisions. We show that the recent computation of
the soft-virtual corrections to Higgs boson production at NLO [1] together
with the universality structure of soft-gluon emission can be exploited to
extract the general expression of the hard-virtual coefficient that contributes
to threshold resummation at NLL accuracy. The hard-virtual coefficient is
directly related to the process-dependent virtual amplitude through a universal
(process-independent) factorization formula that we explicitly evaluate up to
three-loop order. As an application, we present the explicit expression of the
soft-virtual NLO corrections for the production of an arbitrary colourless
system. In the case of the Drell-Yan process, we confirm the recent result of
Ref.[2].Comment: Slightly expanded text, one reference added, version published on NP
Transverse-momentum resummation for the signal-background interference in the H →γγ channel at the LHC
We present an upgraded calculation of the effects of resonance-continuum interference for the Higgs boson decaying to two photons at the Large Hadron Collider, at next-to-leading order in the strong coupling αS, O(αS3), and including transverse-momentum (qT) resummation at next-to-leading logarithmic accuracy. We study the importance of the interference contribution in different transverse-momentum regions, with a particular focus on the low-qT region qT2 Q2 (with Q2 being the invariant diphoton mass) where resummation becomes essential for a reliable calculation
The Dyon Charge in Noncommutative Gauge Theories
We construct a dyon solution for the noncommutative version of the Yang-Mills-Higgs model with a ϑ-term. Extending the Noether method to the case of a noncommutative gauge theory, we analyze the effect of CP violation induced both by the ϑ- term and by noncommutativity proving that theWitten effect formula for the dyon charge remains the same as in ordinary space.Facultad de Ciencias Exacta
Dirac Quantization Condition for Monopole in Noncommutative Space-Time
Since the structure of space-time at very short distances is believed to get
modified possibly due to noncommutativity effects and as the Dirac Quantization
Condition (DQC), , probes the magnetic field point
singularity, a natural question arises whether the same condition will still
survive. We show that the DQC on a noncommutative space in a model of dynamical
noncommutative quantum mechanics remains the same as in the commutative case to
first order in the noncommutativity parameter , leading to the
conjecture that the condition will not alter in higher orders.Comment: 11 page
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