872 research outputs found
Contributions to Anomalies from -Parity Violating Interactions
We examine the parameter space of supersymmetric models with -parity
violating interactions of the form to explain the various
anomalies observed in transitions. To generate the
appropriate operator in the low energy theory, we are led to a region of
parameter space where loop contributions dominate. In particular, we
concentrate on parameters for which diagrams involving winos, which have not
been previously considered, give large contributions. Many different
potentially constraining processes are analyzed, including , mixing, ,
decays to charged leptons, and direct LHC searches. We find that it is
possible to explain the anomalies, but it requires large values of ,
which lead to relatively low Landau poles.Comment: 30 pages, 7 figures, references added, matched to journal versio
Electroweak precision measurements in supersymmetric models with a U(1)R lepton number
As experimental constraints on the parameter space of the MSSM and close
variations thereof become stronger, the motivation to explore supersymmetric
models that challenge some of the standard assumptions of the MSSM also become
stronger. For example, models where the gauginos are Dirac instead of Majorana
have recently received more attention. Beside allowing for a supersoft SUSY
breaking mechanism where the gauginos only provide finite threshold corrections
to scalar masses, the cross section for the production of a squark pairs is
reduced. In addition, Dirac gauginos can be used to build models that possess a
U(1)R symmetry. This symmetry can then be identified with a lepton number,
leading to models that are quite different from conventional scenarios. The
sneutrinos in these models can acquire a vev and give mass to the leptons and
the down-type squark. The phenomenology is novel, combining signatures that are
typical of R-parity violating scenarios with signatures arising from
leptoquarks. Correspondingly the constraints from electroweak precision data
are also different. In these models, one of the leptons mixes with gauginos and
superpotential Yukawa couplings can contribute to EWPM at tree level. In
addition, lepton universality is broken. In this paper we adapt the operators
analysis of Han and Skiba [1] to include the relevant violation of lepton
universality, and do a global fit of the model to electroweak precision data,
including all relevant tree-level and loop-level effects. We obtain bounds on
the vev of the sneutrino and on the superpotential couplings of the model.Comment: 18 pages, 6 figures, references adde
Nonisotropic 3-level Quantum Systems: Complete Solutions for Minimum Time and Minimum Energy
We apply techniques of subriemannian geometry on Lie groups and of optimal
synthesis on 2-D manifolds to the population transfer problem in a three-level
quantum system driven by two laser pulses, of arbitrary shape and frequency. In
the rotating wave approximation, we consider a nonisotropic model i.e. a model
in which the two coupling constants of the lasers are different. The aim is to
induce transitions from the first to the third level, minimizing 1) the time of
the transition (with bounded laser amplitudes),
2) the energy of lasers (with fixed final time). After reducing the problem
to real variables, for the purpose 1) we develop a theory of time optimal
syntheses for distributional problem on 2-D-manifolds, while for the purpose 2)
we use techniques of subriemannian geometry on 3-D Lie groups. The complete
optimal syntheses are computed.Comment: 29 pages, 6 figure
LHC constraints on Mini-Split anomaly and gauge mediation and prospects for LHC 14 and a future 100 TeV pp collider
Stringent experimental constraints have raised the lower limit on the masses
of squarks to TeV levels, while compatibility with the mass of the Higgs boson
provides an upper limit. This two-sided bound has lead to the emergence of
Mini-Split theories where gauginos are not far removed from the electroweak
scale while scalars are somewhat heavier. This small hierarchy modifies the
spectrum of standard anomaly and gauge mediation, leading to Mini-Split
deflected anomaly and gauge mediation models. In this paper, we study LHC
constraints on these models and their prospects at LHC 14 and a 100 TeV
collider. Current constraints on their parameter space come from ATLAS and CMS
supersymmetry searches, the known mass of the Higgs boson, and the absence of a
color-breaking vacuum. Prospects at LHC 14 and a 100 TeV collider are obtained
from these same theoretical constraints in conjunction with background
estimates. As would be expected from renormalization group effects, a slightly
lighter third generation of squarks is assumed. Higgsinos have masses similar
to those of the scalars and are at the origin of the deflection.Comment: 25 pages, 10 figures, references added, LHC 14 results added, matched
to journal versio
Mirror World at the Large Hadron Collider
A mirror world can modify in a striking way the LHC signals of the Higgs
sector. An exact or approximate Z_2 symmetry between the mirror world and our
world allows large mixing between the Higgs bosons of these worlds, leading to
production rates and branching ratios for these states that are markedly
different from the standard model and are characteristic of a mirror world. The
constraints on these Higgs boson masses from precision electroweak data differ
from the standard model bound, so that the new physics that cancels the
quadratic divergence induced by the top quark may appear at a larger scale,
possibly beyond the reach of the LHC. However, the scale of new physics needed
to cancel the quadratic divergence induced by the Higgs boson is not
significantly changed. With small breakings of the Z_2 parity, the lightest
mirror quarks (and possibly charged mirror leptons) could be the dark matter in
the universe, forming galactic halos that are stable to cooling. A possible
signal from the relic radiation density of the mirror world is also discussed.Comment: 15 pages, 1 figur
Development, Capitalists and Extractive Rent: Class Struggles in Venezuela and Ecuador
Through a relational class perspective, this dissertation compares the evolution of the development models in Venezuela and Ecuador since the 1970s to better understand the significance of the recent turn to the left. Based on field research in both countries comprising extensive interviews with representatives of social movements and business interest groups, it studies the main class organizations, their struggles, and their relation with the state in order to shed light on the dynamics of change in the development models pursued in each country, and the role that extractive rent plays within them.
While governments associated with the pink tide in Venezuela and Ecuador were not elected under similar economic contexts, they faced comparable political conditions. In particular, both countries faced situations where class struggle adopted a particular form as popular classes lost their coordination, and the capitalist classes had significant influence over the state. In response to the challenge these conditions represented, left governments attempted to increase the capacity of the state to act with more autonomy through the adoption of new constitutions and the reassertion of state ownership over extractive resources to pursue a rent-based social-developmental model. This involved the use of extractive rent for redistributive measures and as a leverage to foster economic diversification.
A comparative perspective on social classes shows how a united capitalist class in Venezuela, adopting a confrontational stance, pushed the state to rely increasingly on its role as a dispenser of rent. By contrast, a regionally divided capitalist class in Ecuador reacted less combatively, and led the Ecuadorian state to follow a social-developmental model more supportive of private initiative for economic diversification. In both cases, however, the governments put in place strategies aimed at gaining control over the responses of the popular sector.
As opposed to discussions of populism, focusing on the irrational relationship between the leader and its followers, or approaches that focus on categorizing different kinds of left governments, or even perspectives that stress the determining role of natural resources, this dissertation analyzes class struggles as a crucial factor to understanding the transformation of the state and of the development model it pursues
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