6,410 research outputs found
One Loop Soft Supersymmetry Breaking Terms in Superstring Effective Theories
We perform a systematic analysis of soft supersymmetry breaking terms at the
one loop level in a large class of string effective field theories. This
includes the so-called anomaly mediated contributions. We illustrate our
results for several classes of orbifold models. In particular, we discuss a
class of models where soft supersymmetry breaking terms are determined by quasi
model independent anomaly mediated contributions, with possibly non-vanishing
scalar masses at the one loop level. We show that the latter contribution
depends on the detailed prescription of the regularization process which is
assumed to represent the Planck scale physics of the underlying fundamental
theory. The usual anomaly mediation case with vanishing scalar masses at one
loop is not found to be generic. However gaugino masses and A-terms always
vanish at tree level if supersymmetry breaking is moduli dominated with the
moduli stabilized at self-dual points, whereas the vanishing of the B-term
depends on the origin of the mu-term in the underlying theory. We also discuss
the supersymmetric spectrum of O-I and O-II models, as well as a model of
gaugino condensation. For reference, explicit spectra corresponding to a Higgs
mass of 114 GeV are given. Finally, we address general strategies for
distinguishing among these models.Comment: 49 pages: includes three tables and nine figure
On Quadratic Divergences in Supergravity, Vacuum Energy and the Supersymmetric Flavor Problem
We examine the phenomenological consequences of quadratically divergent
contributions to the scalar potential in supergravity effective Lagrangians. We
focus specifically on the effect of these corrections on the vacuum
configuration of scalar fields in softly-broken supersymmetric theories and the
role these corrections play in generating non-diagonal soft scalar masses. Both
effects can only be properly studied when the divergences are regulated in a
manifestly supersymmetric manner -- something which has thus far been neglected
in past treatments. We show how a supersymmetric regularization can impact past
conclusions about both types of phenomena and discuss what types of high-energy
theories are likely to be safe from unwanted flavor-changing neutral current
interactions in the context of supergravity theories derived from heterotic
string compactifications
Life cycle assessment of Swiss organic farming systems
The impacts of organic and integrated farming systems in Switzerland on the environment have been assessed in a comprehensive study by the life cycle assessment method. This paper reports a comparison of the treatments of the DOC experiment. Organic farming showed clear ecological advantages particularly for eco- and human toxicity, resource use and biodiversity. These ecological advantages only partly apply to nutrient losses and are not always found for single products. Per kg of organic product, higher impacts were often found for global warming potential, ozone formation, eutrophication and acidification compared to integrated production. In the same crop rotation with the same amount of organic fertilisers there were no systematic differences in soil quality of organic compared with integrated production. Further improvement of the environmental performance of organic farming should focus on achieving higher yields of good quality – especially in potatoes and cereals - by using inputs more efficiently and minimising nitrogen losses
The Standard Model of Particle Physics
Particle physics has evolved a coherent model that characterizes forces and
particles at the most elementary level. This Standard Model, built from many
theoretical and experimental studies, is in excellent accord with almost all
current data. However, there are many hints that it is but an approximation to
a yet more fundamental theory. We trace the development of the Standard Model
and indicate the reasons for believing that it is incomplete.Comment: 25 pages, 17 figures; accepted for publication in Rev. Mod. Physics
(APS centenary issue
Understanding the Digital Divide As It Relates to Electronic Commerce
There exists an electronic digital divide within the United States. This digital divide concerns access to the Internet and its corresponding technologies. The U.S. government is concerned about the digital divide because it appears that certain ethnic groups and income levels are being excluded from computer technologies and the Internet. These groups include African Americans and Hispanics, who are lagging the Caucasians significantly in gaining access to the Internet. For a while the gap between majority and minority groups appeared to be widening. Since Internet access is a prerequisite to electronic commerce, an understanding of the relationship between the digital divide and marketing is important. Numerous Federal, State, and Local governments are trying to reduce or eliminate the digital divide to ensure equal access to all citizens. Marketing would benefit if equal access also meant increased electronic commerce.
Business leaders are also concerned about the digital divide because it affects access to the Internet and corresponding technologies. If the consumers are denied access to the Internet, it will be difficult for them to participate in business to consumer (B2C) level electronic commerce. However, this research has shown statistically that solving the problems of the digital divide will not necessarily aid business to consumer level electronic commerce. The research has further found that the apparent reasons for the digital divide, currently thought to be income, education, and ethnic orientation, may be less important than initial government surveys indicate.
The research demonstrates that between Internet access and consumer intent to purchase goods and services in business to consumer electronic commerce lies at least three other considerations that need to be addressed by business leaders. These areas are: consumer trust, consumer commitment, and consumer involvement with Internet technologies. All are important links between using the technology at all and using the technology for business to consumer electronic commerce. The research also shows that these three areas have a combined relationship to the magnitude of the digital divide. Thus, any actions that affect these constructs will also affect the digital divide.
Business leaders seeking to engage in business to consumer electronic commerce must pay attention to consumer trust, consumer commitment, and optimizing the consumer experience (involvement) when using the Internet. Not addressing these issues proactively will increase the likelihood of failure while engaging in electronic commerce
The 2D analogue of the Reissner-Nordstrom solution
A two-dimensional (2D) dilaton gravity model, whose static solutions have the
same features of the Reissner-Nordstrom solutions, is obtained from the
dimensional reduction of a four-dimensional (4D) string effective action
invariant under S-duality transformations. The black hole solutions of the 2D
model and their relationship with those of the 4D theory are discussed.Comment: 5 pages, Plain-Tex, no figure
Constraints on Hidden Sector Gaugino Condensation
We study the phenomenology of a class of models describing modular invariant
gaugino condensation in the hidden sector of a low-energy effective theory
derived from the heterotic string. Placing simple demands on the resulting
observable sector, such as a supersymmetry-breaking scale of approximately 1
TeV, a vacuum with properly broken electroweak symmetry, superpartner masses
above current direct search limits, etc., results in significant restrictions
on the possible configurations of the hidden sector.Comment: 33 pages, 10 figures. Full postscript also available from
http://phyweb.lbl.gov/theorygroup/papers/44305.p
Testing Gaugino Mass Unification Directly at the LHC
We report on the first step of a systematic study of how gaugino mass
unification can be probed at the LHC in a quasi-model independent manner. Here
we focus our attention on the theoretically well-motivated mirage pattern of
gaugino masses, a one-parameter family of models of which universal (high
scale) gaugino masses are a limiting case. Using a statistical method to
optimize our signature selection we arrive at three ensembles of observables
targeted at the physics of the gaugino sector, allowing for a determination of
this non-universality parameter without reconstructing individual mass
eigenvalues or the soft supersymmetry-breaking gaugino masses themselves. In
this controlled environment we find that approximately 80% of the
supersymmetric parameter space would give rise to a model for which our method
will detect non-universality in the gaugino mass sector at the 10% level with
approximately 10 inverse femptobarns of integrated luminosity.Comment: To appear in proceedings of "Beyond the Standard Model at the LHC
(BSM-LHC)", June 2-4, 200
Re-examination of Electroweak Symmetry Breaking in Supersymmetry and Implications for Light Superpartners
We examine arguments that could avoid light superpartners as an implication
of supersymmetric radiative electroweak symmetry breaking. We argue that, from
the point of view of string theory and standard approaches to generating the
mu-term, cancellations among parameters are not a generic feature. While the
coefficients relating the Z-mass to parameters in the soft supersymmetry
breaking Lagrangian can be made smaller, these same mechanisms lead to lighter
superpartner masses at the electroweak scale. Consequently we strengthen the
implication that gluinos, neutralinos, and charginos are light and likely to be
produced at the Fermilab Tevatron and a linear collider.Comment: 27 pages, 3 figure
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