116 research outputs found
Calculations of Resonance Coupling Constants in the Scalar Sector of the ENJL Model
We derive the scalar resonance coupling constants of resonance chiral theory
from the Extended Nambu Jona-Lasinio model by using heat-kernel expansion.Comment: 7 page
A precise characterisation of the top quark electro-weak vertices at the ILC
Top quark production in the process at a future linear
electron positron collider with polarised beams is a powerful tool to determine
indirectly the scale of new physics. The presented study, based on a detailed
simulation of the ILD detector concept, assumes a centre-of-mass energy of
GeV and a luminosity of
equally shared between the incoming beam polarisations of . Events are selected in which the top pair
decays semi-leptonically and the cross sections and the forward-backward
asymmetries are determined. Based on these results, the vector, axial vector
and tensorial conserving couplings are extracted separately for the photon
and the component. With the expected precision, a large number of models
in which the top quark acts as a messenger to new physics can be distinguished
with many standard deviations. This will dramatically improve expectations from
e.g. the LHC for electro-weak couplings of the top quark.Comment: This work is an update of arXiv:1307.8102, minor changes w.r.t. v1
(typos, wrong grammar, incomplete sentences etc.
pi/K -> e nu branching ratios to O(e^2 p^4) in Chiral Perturbation Theory
We calculate the ratios R_{e/mu}^{(P)} = Gamma(P -> e nu)/Gamma (P -> mu nu)
(P=pi,K) in Chiral Perturbation Theory to order e^2 p^4. We complement the one-
and two-loop effective theory results with a matching calculation of the local
counterterm, performed within the large- expansion. We find
R_{e/mu}^{(\pi)} = (1.2352 \pm 0.0001)*10^{-4} and R_{e/mu}^{(K)} = (2.477 \pm
0.001)*10^{-5}, with uncertainty induced by the matching procedure and chiral
power counting. Given the sensitivity of upcoming new measurements, our results
provide a clean baseline to detect or constrain effects from weak-scale new
physics in these rare decays. As a by-product, we also update the theoretical
analysis of the individual pi/K -> \ell nu modes.Comment: 40 pages, 4 figures, 3 table
On the radiative decays of light vector and axial-vector mesons
We study the light vector and axial-vector mesons. According to the
hadrogenesis conjecture the nature of the two types of states is distinct. The
axial-vector mesons are generated dynamically by coupled-channel interactions
based on the chiral Lagrangian written down in terms of the Goldstone bosons
and the light vector mesons. We propose a novel counting scheme that arises if
the chiral Lagrangian is supplemented by constraints from large-N_c QCD in the
context of the hadrogenesis conjecture. The counting scheme is successfully
tested by a systematic study of the properties of vector mesons. The spectrum
of light axial-vector mesons is derived relying on the leading order
interaction of the Goldstone bosons with the vector mesons supplemented by a
phenomenology for correction terms. The f_1(1282), b_1(1230), h_1(1386),
a_1(1230) and K_1(1272) mesons are recovered as molecular states. Based on
those results the one-loop contributions to the electromagnetic decay
amplitudes of axial-vector molecules into pseudo-scalar or vector mesons are
evaluated systematically. In order to arrive at gauge invariant results in a
transparent manner we choose to represent the vector particles by
anti-symmetric tensor fields. It is emphasized that there are no tree-level
contributions to a radiative decay amplitude of a given state if that state is
generated by coupled-channel dynamics. The inclusion of the latter would be
double counting. At present we restrict ourselves to loops where a vector and a
pseudo-scalar meson couple to the axial-vector molecule. We argue that final
and predictive results require further computations involving intermediate
states with two vector mesons. The relevance of the latter is predicted by our
counting rules.Comment: added appendix concerning double-counting issue
Four-point correlator constraints on electromagnetic chiral parameters and resonance effective Lagrangians
We pursue the analysis of a set of generalized DGMLY sum rules for the
electromagnetic chiral parameters at order and discuss implications
for effective Lagrangians with resonances. We exploit a formalism in which
charge spurions are introduced and treated as sources. We show that no
inconsistency arises from anomalies up to quadratic order in the spurions. We
focus on the sum rules associated with QCD 4-point correlators which were not
analyzed in detail before. Convergence properties of the sum rules are deduced
from a general analysis of the form of the counterterms in the presence of
electromagnetic spurions. Following the approach in which vector and
axial-vector resonances are described with antisymmetric tensor fields and have
a chiral order, we show that the convergence constraints are violated at chiral
order four and can be satisfied by introducing a set of terms of order six. The
relevant couplings get completely and uniquely determined from a set of
generalized Weinberg sum-rule relations. An update on the corrections to
Dashen's low-energy theorem is given.Comment: 42 pages, 1 figure. v2: references adde
On different lagrangian formalisms for vector resonances within chiral perturbation theory
We study the relation of vector Proca field formalism and antisymmetric
tensor field formalism for spin-one resonances in the context of the large N_C
inspired chiral resonance Lagrangian systematically up to the order O(p6) and
give a transparent prescription for the transition from vector to antisymmetric
tensor Lagrangian and vice versa. We also discuss the possibility to describe
the spin-one resonances using an alternative "mixed" first order formalism,
which includes both types of fields simultaneously, and compare this one with
the former two. We also briefly comment on the compatibility of the above
lagrangian formalisms with the high-energy constraints for concrete VVP
correlator.Comment: 34 pages, 3 figure
Electromagnetic transitions in an effective chiral Lagrangian with the eta-prime and light vector mesons
We consider the chiral Lagrangian with a nonet of Goldstone bosons and a
nonet of light vector mesons. The mixing between the pseudoscalar mesons eta
and eta-prime is taken into account. A novel counting scheme is suggested that
is based on hadrogenesis, which conjectures a mass gap in the meson spectrum of
QCD in the limit of a large number of colors. Such a mass gap would justify to
consider the vector mesons and the eta-prime meson as light degrees of freedom.
The complete leading order Lagrangian is constructed and discussed. As a first
application it is tested against electromagnetic transitions of light vector
mesons to pseudoscalar mesons. Our parameters are determined by the
experimental data on photon decays of the omega, phi and eta-prime meson. In
terms of such parameters we predict the corresponding decays into virtual
photons with either dielectrons or dimuons in the final state.Comment: 17 pages, extended discussion on mixin
Influence of drying process and particle size of persimmon fibre on its physicochemical, antioxidant, hydration and emulsifying properties
[EN] Persimmon, given its current surplus production, could be an alternative source for the extraction of certain interesting ingredients for the food industry and human health, such as fibre. Thus, the aim of this study was to analyse the influence of hot air and freeze-drying, as well as the particle size of fibre extracted from persimmon peels or pulp on their physicochemical, antioxidant, hydration and emulsifying properties, compared to commercial fibres (from peach, lemon, orange and apple). The results showed that both freeze-dried persimmon pulp and freeze-dried peel had better hydration properties and oil holding capacity than other fibres analysed, although the swelling capacity was higher for lemon fibre. Freeze-dried persimmon peel fibre showed higher values of emulsion stability than commercial fibres. Finally, the antioxidant activity of the smallest sized persimmon peel fibre obtained by freeze-drying was higher than that for lemon, orange and peach fibre.The authors acknowledge the support of the Universtitat Politecnica de Valencia and certify that there is no conflict of interest with any financial organization regarding the material discussed in the manuscript.MartĂnez-Las Heras, R.; Landines, E.; Heredia GutiĂ©rrez, AB.; CastellĂł GĂłmez, ML.; AndrĂ©s Grau, AM. (2017). Influence of drying process and particle size of persimmon fibre on its physicochemical, antioxidant, hydration and emulsifying properties. Journal of Food Science and Technology. 54(9):1-11. doi:10.1007/s13197-017-2728-zS111549Abdul-Hamid A, Luan YS (2000) Functional properties of dietary fibre prepared from defatted rice bran. Food Chem 68:15â19Adams MR, Moss MO (1997) MicrobiologĂa de los alimentos. 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Food Chem 100:1402â1408Chen XN, Fan JF, Yue X, Wu XR, Li LT (2008) Radical scavenging activity and phenolic compounds in persimmon (Diospyros kaki L. cv. Mopan). J Food Sci 73:24â28de Escalada Pla MF, GonzĂĄlez P, Sette P, Portillo F, Rojas AM, Gerschenson LN (2012) Effect of processing on physico-chemical characteristics of dietary fibre concentrates obtained from peach (Prunus persica L.) peel and pulp. Food Res Int 49:184â192de Moraes Crizel T, Jablonski A, de Oliveira Rios A, Rech R, FlĂŽres SH (2013) Dietary fiber from orange byproducts as a potential fat replacer. LWT-Food Sci Technol 53:9â14Femenia A, Lefebvre AC, Thebaudin JY, Robertson JA, Bourgeois CM (1997) Physical and sensory properties of model foods supplemented with cauliflower fibre. J Food Sci 62:635â639Femenia A, Selvendran RR, Ring SG, Robertson JA (1999) Effects of heat treatment and dehydration on properties of cauliflower fiber. 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Form Factors in the radiative pion decay
We perform an analysis of the form factors that rule the structure-dependent
amplitude in the radiative pion decay. The resonance contributions to pion -> e
nu_e gamma decays are computed through the proper construction of the vector
and axial-vector form factors by setting the QCD driven asymptotic properties
of the three-point Green functions VVP and VAP, and by demanding the smoothing
of the form factors at high transfer of momentum. A comparison between
theoretical and experimental determinations of the form factors is also carried
out. We also consider and evaluate the role played by a non-standard tensor
form factor. We conclude that, at present and due to the hadronic incertitudes,
the search for New Physics in this process is not feasible.Comment: 14 pages, no figures. Typos corrected. Accepted for publication in
The European Physical Journal
Multiobjective Early Design of Complex Distillation Sequences Considering Economic and Inherent Safety Criteria
Inherent safety aspects are not usually considered as a driving force during the conceptual design stage of chemical plants. Instead, after the selection of the optimal economic flowsheet, safety is added to the design. However, this sequential design approach could be applied to inferior designs due to protection devicesâ cost overrun. The objective of this work is to implement a strategy to simultaneously design a profitable and inherently safer distillation train. Two safety indexes, a disaggregated version of the Safety Weighted Hazard Index and Dowâs Fire and Explosion Index, have been adapted to quantify the inherent safety performance. A large-scale multiobjective MILP problem is formulated. Thus, two strategies of objective reduction are utilized: principal component analysis coupled with Debâs algorithm and a method based on the dominance structure. The results prove the suitability of these safety index as inherently safer metrics, and showcase the ability of the objective reduction methods to discriminate among the inherent safety criteria.We acknowledge financial support from âProyectos de I + D para grupos de investigacioÌn emergentes GV/2016/005â (Conselleria dâEducacioÌ, InvestigacioÌ, Cultura i Esport, GENERALITAT VALENCIANA) Spanish âMinisterio de EconomĂa, Industria y Competitividadâ (CTQ2016-77968-C3-2-P, AEI/FEDER, UE)
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