626 research outputs found
The nucleon's strange electromagnetic and scalar matrix elements
Quenched lattice QCD simulations and quenched chiral perturbation theory are
used together for this study of strangeness in the nucleon. Dependences of the
matrix elements on strange quark mass, valence quark mass and momentum transfer
are discussed in both the lattice and chiral frameworks. The combined results
of this study are in good agreement with existing experimental data and
predictions are made for upcoming experiments. Possible future refinements of
the theoretical method are suggested.Comment: 24 pages, 9 figure
A unified approach to Performance Assessment (PA) of geological CO2 storage
AbstractPerformance Assessment (PA) evaluates the effectiveness of a specified system or sub-system relative to some criteria of interest to particular stakeholders. A flexible PA approach has been developed for geological CO2 storage, by which qualitative information, quantitative data, output from numerical models and expert judgments are combined within a decision-support framework. The methodology has been implemented in three software tools: (1) TESLA, which is used to construct decision trees, propagate evidence and record the logic underlying a decision; (2) an on-line database of Features, Events and Processes (FEPs) targeted at CO2 storage; and (3) QPAC-CO2, for modelling system performance
Charmless Two-body Baryonic B Decays
We study charmless two-body baryonic B decays in a diagramatic approach.
Relations on decay amplitudes are obtained. In general there are more than one
tree and more than one penguin amplitudes. The number of independent amplitudes
can be reduced in the large m_B limit. It leads to more predictive results.
Some prominent modes for experimental searches are pointed out.Comment: 15 pages, 2 figures. To appear in Phys. Rev.
Childcare, choice and social class: Caring for young children in the UK
This paper draws on the results of two qualitative research projects examining parental engagements with the childcare market in the UK. Both projects are located in the same two London localities. One project focuses on professional middle class parents, and the other on working class families, and we discuss the key importance of social class in shaping parents' differential engagement with the childcare market, and their understandings of the role childcare plays in their children's lives. We identify and discuss the different "circuits" of care (Ball et al 1995) available to and used by families living physically close to each other, but in social class terms living in different worlds. We also consider parents' relationships with carers, and their social networks. We conclude that in order to fully understand childcare policies and practices and families' experiences of care, an analysis which encompasses social class and the workings of the childcare market is needed
Ice sheet model dependency of the simulated Greenland Ice Sheet in the mid-Pliocene
The understanding of the nature and behavior of ice sheets in past warm periods is important for constraining the potential impacts of future climate change. The Pliocene warm period (between 3.264 and 3.025 Ma) saw global temperatures similar to those projected for future climates; nevertheless, Pliocene ice locations and extents are still poorly constrained. We present results from the efforts to simulate mid-Pliocene Greenland Ice Sheets by means of the international Pliocene Ice Sheet Modeling Intercomparison Project (PLISMIP). We compare the performance of existing numerical ice sheet models in simulating modern control and mid-Pliocene ice sheets with a suite of sensitivity experiments guided by available proxy records. We quantify equilibrated ice sheet volume on Greenland, identifying a potential range in sea level contributions from warm Pliocene scenarios. A series of statistical measures are performed to quantify the confidence of simulations with focus on inter-model and inter-scenario differences. We find that Pliocene Greenland Ice Sheets are less sensitive to differences in ice sheet model configurations and internal physical quantities than to changes in imposed climate forcing. We conclude that Pliocene ice was most likely to be limited to the highest elevations in eastern and southern Greenland as simulated with the highest confidence and by synthesizing available regional proxies; however, the extent of those ice caps needs to be further constrained by using a range of general circulation model (GCM) climate forcings
Polarization phenomena in open charm photoproduction processes
We analyze polarization effects in associative photoproduction of
pseudoscalar () charmed mesons in exclusive processes , , . Circularly polarized photons
induce nonzero polarization of the -hyperon with - and -components
(in the reaction plane) and non vanishing asymmetries and for polarized nucleon target. These polarization observables can be
predicted in model-independent way for exclusive -production processes
in collinear kinematics. The T-even -polarization and asymmetries for
non-collinear kinematics can be calculated in framework of an effective
Lagrangian approach. The depolarization coefficients , characterizing
the dependence of the -polarization on the nucleon polarization are also
calculated.Comment: 36 pages 13 figure
in the Standard Model with Flavor Symmetry
The observed branching ratios for decays are much larger than
factorization predictions in the Standard Model (SM). Many proposals have been
made to reconcile the data and theoretical predictions. In this paper we study
these decays within the SM using flavor U(3) symmetry. If small annihilation
amplitudes are neglected, one needs 11 hadronic parameters to describe decays where can be one of the , , and nonet
mesons. We find that existing data are consistent with SM with flavor U(3)
symmetry. We also predict several measurable branching ratios and CP
asymmetries for , decays.
Near future experiments can provide important tests for the Standard Model with
flavor U(3) symmetry.Comment: 13 pages, 4 table
Hyperon semileptonic decays and quark spin content of the proton
We investigate the hyperon semileptonic decays and the quark spin content of
the proton taking into account flavor SU(3) symmetry breaking.
Symmetry breaking is implemented with the help of the chiral quark-soliton
model in an approach, in which the dynamical parameters are fixed by the
experimental data for six hyperon semileptonic decay constants. As a result we
predict the unmeasured decay constants, particularly for ,
which will be soon measured and examine the effect of the SU(3) symmetry
breaking on the spin content of the proton. Unfortunately
large experimental errors of decays propagate in our analysis making
and practically undetermined. We conclude that
statements concerning the values of these two quantities, which are based on
the exact SU(3) symmetry, are premature. We stress that the meaningful results
can be obtained only if the experimental errors for the decays are
reduced.Comment: The final version accepted for publication in Phys. Rev. D. 18 pages,
RevTex is used with 4 figures include
'Itâs like saying âcoloured"' : understanding and analysing the urban working classes
This paper draws on data from a qualitative project exploring the engagement of working class families in London with childcare. It is a first attempt to throw some light on our usage of the term âworking classâ, and consider what forms âworking class-nessâ takes in relation to our respondent families. We discuss some recent sociological literature on the working class(es) in order to understand the emphasises and focuses of other research. We emphasise the heterogeneity of the working class(es), the differences in attitude and experiences based on place, gender, occupational status, education, age and family membership. Then we consider our respondents in relation to their strategies and exercise of agency, their engagement with the labour market, and their embedded-ness in social networks. We conclude that one way of understanding the lives of urban working class families is to consider the extent to which they âmanage or struggle to copeâ, a focus which emphasises process, activity and the differential degrees of agency which the respondents are able to exercise
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