554 research outputs found
pi-pi and pi-K scatterings in three-flavour resummed chiral perturbation theory
The (light but not-so-light) strange quark may play a special role in the
low-energy dynamics of QCD. The presence of strange quark pairs in the sea may
have a significant impact of the pattern of chiral symmetry breaking : in
particular large differences can occur between the chiral limits of two and
three massless flavours (i.e., whether m_s is kept at its physical value or
sent to zero). This may induce problems of convergence in three-flavour chiral
expansions. To cope with such difficulties, we introduce a new framework,
called Resummed Chiral Perturbation Theory. We exploit it to analyse pi-pi and
pi-K scatterings and match them with dispersive results in a frequentist
framework. Constraints on three-flavour chiral order parameters are derived.Comment: Proceedings of the EPS-HEP 2007 Conference, Manchester (UK). 3 pages,
1 figur
Sustainability in energy production
The requirement of energy in different human activities is continuously increasing; from the energetic production, chiefly by thermal systems, important and worrying environmental problems are generated: there are concerns about climate change, local air quality worsening, exhaustion of resources and land use change. To limit these negative aspects, policies of reduction in energy use must be first proposed; besides different technological, economic and planning solutions can be considered; their effect must be carefully assessed, as concerns effectiveness and practical implementation. The final political decision must consider the different tools that are at disposal, in order to define the best approach for the satisfaction of necessities with the minimum consequent impact
Chiral dynamics with strange quarks in the light of recent lattice simulations
Several lattice collaborations performing simulations with 2+1 light
dynamical quarks have experienced difficulties in fitting their data with
standard Nf=3 chiral expansions at next-to-leading order, yielding low values
of the quark condensate and/or the decay constant in the Nf=3 chiral limit. A
reordering of these expansions seems required to analyse these data in a
consistent way. We discuss such a reordering, known as Resummed Chiral
Perturbation Theory, in the case of pseudoscalar masses and decay constants,
pion and kaon electromagnetic form factors and Kl3} form factors. We show that
it provides a good fit of the recent results of two lattice collaborations
(PACS-CS and RBC/UKQCD). We describe the emerging picture for the pattern of
chiral symmetry breaking, marked by a strong dependence of the observables on
the strange quark mass and thus a significant difference between chiral
symmetry breaking in the Nf=2 and Nf=3 chiral limits. We discuss the
consequences for the ratio of decay constants F_K/F_pi and the Kl3 form factor
at vanishing momentum transfer.Comment: 31 pages. Published versio
Determining the chiral condensate from the distribution of the winding number beyond topological susceptibility
The first two non-trivial moments of the distribution of the topological
charge (or gluonic winding number), i.e., the topological susceptibility and
the fourth cumulant, can be computed in lattice QCD simulations and exploited
to constrain the pattern of chiral symmetry breaking. We compute these two
topological observables at next-to-leading order in three-flavour Chiral
Perturbation Theory, and we discuss the role played by the eta propagation in
these expressions. For hierarchies of light-quark masses close to the physical
situation, we show that the fourth cumulant has a much better sensitivity than
the topological susceptibility to the three-flavour quark condensate, and thus
constitutes a relevant tool to determine the pattern of chiral symmetry
breaking in the limit of three massless flavours. We provide the complete
formulae for the two topological observables in the isospin limit, and predict
their values in the particular setting of the recent analysis of the RBC/UKQCD
collaboration. We show that a combination of the topological susceptibility and
the fourth cumulant is able to pin down the three-flavour condensate in a
particularly clean way in the case of three degenerate quarks.Comment: 31 pages, 7 figures. Accepted for publication in EPJ
Three-particle contributions to the renormalisation of B-meson light-cone distribution amplitudes
We study light-cone distribution amplitudes of heavy-light systems, such as a
B-meson. By an explicit computation, we determine how two-parton distribution
amplitudes mix with three-parton ones at one loop: \phi_+ is shown to mix only
into itself, whereas \phi_- mixes with the difference of three-parton
distribution amplitudes \Psi_A-\Psi_V. We determine the corresponding anomalous
dimension and we check the gauge independence of our result by considering a
general covariant gauge. Finally, we comment on some implications of our result
for phenomenological models of these distribution amplitudes.Comment: 21 pages, 5 figures, some comments and 2 references added, except for
typesetting matches version published in JHE
PoN-S : a systematic approach for applying the Physics of Notation (PoN)
Visual Modeling Languages (VMLs) are important instruments of communication between modelers and stakeholders. Thus, it is important to provide guidelines for designing VMLs. The most widespread approach for analyzing and designing concrete syntaxes for VMLs is the so-called Physics of Notation (PoN). PoN has been successfully applied in the analysis of several VMLs. However, despite its popularity, the application of PoN principles for designing VMLs has been limited. This paper presents a systematic approach for applying PoN in the design of the concrete syntax of VMLs. We propose here a design process establishing activities to be performed, their connection to PoN principles, as well as criteria for grouping PoN principles that guide this process. Moreover, we present a case study in which a visual notation for representing Ontology Pattern Languages is designed
Environmental balance study for the construction of a biomass plant in a small town in Piedmont (Northern Italy)
In consideration of local critical aspects in opposition to overall environmental benefits (decrease of GHG generation), the aim of this work is to verify the local acceptability from the point of view of air quality of the territory in question for a biomass plant. The plant to be realized in a small town located in Piedmont, Northern Italy, will be constructed to produce electricity and heat. In order to verify the aspect of compatibility we performed an evaluation of the emissive flow modification that in the hypothesis of the biomass plant activation should be introduced in the municipal area. The evaluation has been conducted by using mass and energy balances as a tool. © 2011 WIT Press
Extracting CP violation and strong phase in D decays by using quantum correlations in psi(3770)-> D0\bar{D}0 -> (V1V2)(V3V4) and psi(3770)->D0\bar{D}0 -> (V1V2)(K pi)
The charm quark offers interesting opportunities to cross-check the mechanism
of CP violation precisely tested in the strange and beauty sectors. In this
paper, we exploit the angular and quantum correlations in the D\bar{D} pairs
produced through the decay of the psi(3770) resonance in a charm factory to
investigate CP-violation in two different ways. We build CP-violating
observables in psi(3770) -> D\bar{D} -> (V_1V_2)(V_3 V_4) to isolate specific
New Physics effects in the charm sector. We also consider the case of psi(3770)
-> D\bar{D} -> (V_1V_2)(K\pi) decays, which provide a new way to measure the
strong phase difference delta between Cabibbo-favored and doubly-Cabibbo
suppressed D decays required in the determination of the CKM angle gamma.
Neglecting the systematics, we give a first rough estimate of the sensitivities
of these measurements at BES-III with an integrated luminosity of 20 fb^-1 at
psi(3770) peak and at a future Super tau-charm factory with a luminosity of
10^35 cm^-2.s^-1.Comment: 13 pages
Sustainability in energy production
The requirement of energy in different human activities is continuously increasing; from the energetic production, chiefly by thermal systems, important and worrying environmental problems are generated: there are concerns about climate change, local air quality worsening, exhaustion of resources and land use change. To limit these negative aspects, policies of reduction in energy use must be first proposed; besides different technological, economic and planning solutions can be considered; their effect must be carefully assessed, as concerns effectiveness and practical implementation. The final political decision must consider the different tools that are at disposal, in order to define the best approach for the satisfaction of necessities with the minimum consequent impact
- …