504 research outputs found
The CP properties of the lightest Higgs boson with sbottom effects
In the framework of the recently proposed gluino-axion model, using the
effective potential method and taking into account the top-stop as well as the
bottom-sbottom effects, we discuss the CP--properties of the lightest Higgs
boson, in particular its CP--odd composition, which can offer new opportunities
at collider searches. It is found that although the CP-odd composition of the
lightest Higgs increases slightly with the inclusion of the sbottom effects, it
never exceeds %0.17 for all values of the renormalization scale Q ranging from
top mass to TeV scaleComment: 24 pp, 12 eps fig
The Topological Unitarity Identities in Chern-Simons Theories
Starting from the generating functional of the theory of relativistic spinors
in 2+1 dimensions interacting through the pure Chern-Simons gauge field, the
S-matrix is constructed and seen to be formally the same as that of spinor
quantum electrodynamics in 2+1 dimensions with Feynman diagrams having external
photon lines excluded, and with the propagator of the topological Chern-Simons
photon substituted for the Maxwell photon propagator. It is shown that the
absence of real topological photons in the complete set of vector states of the
total Hilbert space leads in a given order of perturbation theory to
topological unitarity identities that demand the vanishing of the
gauge-invariant sum of the imaginary parts of Feynman diagrams with a given
number of internal on-shell free topological photon lines. It is also shown,
that these identities can be derived outside the framework of perturbation
theory. The identities are verified explicitly for the scattering of a
fermion-antifermion pair in one-loop order.Comment: 13 pages, LaTex file, one figure (not included
Classical limit for the scattering of Dirac particles in a magnetic field
We present a relativistic quantum calculation at first order in perturbation
theory of the differential cross section for a Dirac particle scattered by a
solenoidal magnetic field. The resulting cross section is symmetric in the
scattering angle as those obtained by Aharonov and Bohm (AB) in the string
limit and by Landau and Lifshitz (LL) for the non relativistic case. We show
that taking pr_0\|sin(\theta/2)|/\hbar<<1 in our expression of the differential
cross section it reduces to the one reported by AB, and if additionally we
assume \theta << 1 our result becomes the one obtained by LL. However, these
limits are explicitly singular in \hbar as opposed to our initial result. We
analyze the singular behavior in \hbar and show that the perturbative Planck's
limit (\hbar -> 0) is consistent, contrarily to those of the AB and LL
expressions. We also discuss the scattering in a uniform and constant magnetic
field, which resembles some features of QCD
Optimizing Current Collector Interfaces for Efficient âAnode-Freeâ Lithium Metal Batteries
Current lithium (Li)-metal anodes are not sustainable for the mass production of future energy storage devices because they are inherently unsafe, expensive, and environmentally unfriendly. The anode-free concept, in which a current collector (CC) is directly used as the host to plate Li-metal, by using only the Li content coming from the positive electrode, could unlock the development of highly energy-dense and low-cost rechargeable batteries. Unfortunately, dead Li-metal forms during cycling, leading to a progressive and fast capacity loss. Therefore, the optimization of the CC/electrolyte interface and modifications of CC designs are key to producing highly efficient anode-free batteries with liquid and solid-state electrolytes. Lithiophilicity and electronic conductivity must be tuned to optimize the plating process of Li-metal. This review summarizes the recent progress and key findings in the CC design (e.g. 3D structures) and its interaction with electrolytes
On the Nonabelian Aharonov Bohm Scattering of Spinless Particles
The Aharonov Bohm scattering for spinless, isospin 1/2, particles interacting
through a nonabelian Chern-Simons field is studied. Starting from the
relativistic quantum field theory and using a Coulomb gauge formulation, the
one loop renormalization program is implemented. Through the introduction of an
intermediary cutoff, separating the regions of high and low integration
momentum, the nonrelativistic limit is derived. The next to leading
relativistic approximation is also determined. In this approach quantum field
theory vacuum polarization effects are automatically incorporated.Comment: 20 pages, 8 figures, revtex. Misspelled reference corrected and new
references adde
Neutral Higgs bosons in the MNMSSM with explicit CP violation
Within the framework of the minimal non-minimal supersymmetric standard model
(MNMSSM) with tadpole terms, CP violation effects in the Higgs sector are
investigated at the one-loop level, where the radiative corrections from the
loops of the quark and squarks of the third generation are taken into account.
Assuming that the squark masses are not degenerate, the radiative corrections
due to the stop and sbottom quarks give rise to CP phases, which trigger the CP
violation explicitly in the Higgs sector of the MNMSSM. The masses, the
branching ratios for dominant decay channels, and the total decay widths of the
five neutral Higgs bosons in the MNMSSM are calculated in the presence of the
explicit CP violation. The dependence of these quantities on the CP phases is
quite recognizable, for given parameter values.Comment: 25 pages, 8 figure
The Rare Decay D^0 -> gamma gamma
We present a calculation of the rare decay mode D^0 -> gamma gamma, in which
the long distance contributions are expected to be dominant. Using the Heavy
Quark Chiral Perturbation Theory Lagrangian with a strong g coupling as
recently determined by CLEO from the D^* -> D pi width, we consider both the
anomaly contribution which relates to the annihilation part of the weak
Lagrangian and the one-loop pi, K diagrams. The loop contributions which are
proportional to g and contain the a_1 Wilson coefficient are found to dominate
the decay amplitude, which turns out to be mainly parity violating. The
branching ratio is then calculated to be (1.0+-0.5)x10^(-8). Observation of an
order of magnitude larger branching ratio could be indicative of new physics.Comment: 16 pages, 5 figures, additional reference and several remarks added,
results unchange
Weak Isospin Violations in Charged and Neutral Higgs Couplings from SUSY Loop Corrections
Supersymmetric QCD and supersymmetric electroweak loop corrections to the
violations of weak isospin to Yukawa couplings are investigated. Specifically
it involves an analysis of the supersymmetric loop corrections to the Higgs
couplings to the third generation quarks and leptons. Here we analyze the SUSY
loop corrections to the charged Higgs couplings which are then compared with
the supersymmetric loop corrections to the neutral Higgs couplings previously
computed. It is found that the weak isospin violations can be quite
significant, i.e, as much as 40-50% or more of the total loop correction to the
Yukawa coupling. The effects of CP phases are also studied and it is found that
these effects can either enhance or suppress the weak isospin violations. We
also investigate the weak isospin violation effects on the branching ratio
and show that the effects
are sensitive to CP phases. Thus an accurate measurement of this branching
ratio along with the branching ratio of the neutral Higgs boson decays can
provide a measure of weak isospin violation along with providing a clue to the
presence of supersymmetry.Comment: 20 pages, 9 figure
Key constraints to smallholder village chicken production and marketing systems in Centre-Nord region, Burkina Faso
Objective
Chicken keeping among rural households in low-income countries like Burkina Faso provides an important source of income, nutrition, and gifts to strengthen social ties. However, the sector is hampered by high losses mostly due to diseases, limited access to farm inputs and value chain inefficiency impacting on productivity, marketing and human health. To better understand these issues, we investigated challenges faced by male and female poultry producers and other value chain actors, with emphasis given to animal health and welfare issues.
Material and methods
This study was conducted in the framework of the Poultry Losses and One Health (POLOH) project implemented by the International Livestock research Institute and partners. Two stakeholder workshops and one field site scoping visit were carried out but the research team. Various village poultry value chain stakeholders were engaged in group discussions or informal interviews in September and October 2022. National workshop participants (22 men, 8 women) included national and international research organizations, private sector, extension agents, government and development organizations. A site scoping visit included meetings with 14 stakeholders (9 men, 5 women) and field visits to poultry farms and markets. The workshop in Centre-Nord was attended by 60 stakeholders (50 men, 10 women) including representatives of producer cooperatives, traders, project area village leaders, private veterinarians, government (animal health, human health and environment) and development NGOs. Discussions focused on issues negatively affecting the village poultry value chain, and specific gender constraints and recommendations for upgrading the value chain.
Results
The national workshop identified a range of constraints, including lack of feed associated with increased cereal prices; insufficient veterinary service coverage due to the low number of animal health workers; insufficient producer knowledge of poultry farming good practices; persistence of poultry diseases; inadequate housing; difficulty accessing micro-credit finances; and insecurity in the region.
The Nord-Centre regional workshop with grassroot stakeholders, raised similar constraints. The top three constraints cited by input suppliers were: low level of actor knowledge about good management practices; low formal education of actors; and emergence of poultry diseases.
Producers cited: non-availability of veterinary pharmaceuticals; difficulty accessing feeds; and insufficient funds to purchase farm inputs.
Market actors cited: lack of poultry slaughter sites; unsuitable poultry transport and lack of dedicated poultry markets.
Women's issues included: lack of financial resources to grow farming business; lack knowledge on how to tackle zoonotic diseases; and the high costs of veterinary inputs. Recommendations to boost the poultry sector in the Centre-Nord region, included: build producer capacity; train processing node actors on good hygiene practices; strengthen extension agent capacity; facilitate access to loans; train actors in herd management and marketing; involve all stakeholders in the consultation process and decision-making to develop the poultry sector; and raise awareness of on the merits of empowering women in production activities such as leadership and their participation in meeting household needs.
Conclusion
These findings will guide interventions to improve poultry productivity and provision of safe chicken products to consumers. In-depth qualitative interviews and household surveys are ongoing to support context specific interventions that will be scaled up to sustainably increase livelihoods food and nutrition security
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