161 research outputs found
On meson dominance in the `second class' tau \to eta pi nu_tau decay
Motivated by recent estimates of the isospin-violating process tau \to eta pi
nu_tau, mostly relying on the rho and a_0 dominance of the relevant form
factors near threshold, we present an assessment for the branching ratio that
accounts for additional, potential, effects from the lowest radial excitations
rho(1450) and a_0(1450), respectively, also lying in the decay phase space.Comment: 8 page
Measuring Double Parton Distributions in Nucleons at Proton-Nucleus Colliders
We predict a strong enhancement of multijet production in proton-nucleus
collisions at collider energies, as compared to a naive expectation of a cross
section . The study of the process would allow to measure, for the
first time, the double parton distribution functions in a nucleon in a model
independent way and hence to study both the longitudinal and the transverse
correlations of partons.Comment: 12 pages, 2 figure
Diverse and Variable Community Structure of Picophytoplankton across the Laurentian Great Lakes
The Laurentian Great Lakes provide economic support to millions of people, drive biogeochemical cycling, and are an important natural laboratory for characterizing the fundamental components of aquatic ecosystems. Small phytoplankton are important contributors to the food web in much of the Laurentian Great Lakes. Here, for the first time, we reveal and quantify eight phenotypically distinct picophytoplankton populations across the Lakes using a multilaser flow cytometry approach, which distinguishes cells based on their pigment phenotype. The distributions and diversity of picophytoplankton flow populations varied across lakes and depths, with Lake Erie standing out with the highest diversity. By sequencing sorted cells, we identified several distinct lineages of Synechococcales spanning Subclusters 5.2 and 5.3. Distinct genotypic clusters mapped to phenotypically similar flow populations, suggesting that there may not be a clear one-to-one mapping between genotypes and phenotypes. This suggests genome-level differentiation between lakes but some degree of phenotypic convergence in pigment characteristics. Our results demonstrate that ecological selection for locally adapted populations may outpace homogenization by physical transport in this interconnected system. Given the reliance of the Lakes on in situ primary production as a source for organic carbon, this work sets the foundation to test how the community structure of small primary producers corresponds to biogeochemical and food web functions of the Great Lakes and other freshwater systems
Multiparton interactions and production of minijets in high energy hadronic collisions
We discuss the inclusive cross section to produce two minijets with a large
separation in rapidity in high energy hadronic collisions. The contribution to
the inclusive cross section from the exchange of a BFKL Pomeron is compared
with the contribution from the exchange of two BFKL Pomerons, which is induced
by the unitarization of the semi-hard interaction. The effect of the multiple
exchange is studied both as a function of the azimuthal correlation and as a
function of the transverse momentum of the observed minijets.Comment: TeX file, 20 pages, 4 figures available on reques
High- production as signals for Double Parton scattering at hadron colliders
We present an analysis of the \psi\psi production from double parton (DP)
sacttering and single parton (SP) scattering in the large p_T region via
color-octet gluon fragmentation. We find that at the Tevatron the DP \psi\psi
production is at the edge of the detectability at present, and at the LHC the
DP cross section will dominate over the SP cross section in the lower p_T(min)
region (i.e., p_T(min)<7GeV). We also conclude that the color-octet mechanism
is of crucial importance to the double j/psi production at high energy hadron
colliders.Comment: Revtex, 12 pages, 3 Postscript figure
The possible - mixing in QCD sum rules
We calculate the on-shell - mixing parameter with
the method of QCD sum rule. Our result is MeV. The electromagnetic interaction is not included
Growing Environmental Activists: Developing Environmental Agency and Engagement Through Children’s Fiction.
We explore how story has the potential to encourage environmental engagement and a sense of agency provided that critical discussion takes place. We illuminate this with reference to the philosophies of John Macmurray on personal agency and social relations; of John Dewey on the primacy of experience for philosophy; and of Paul Ricoeur on hermeneutics, dialogue, dialectics and narrative. We view the use of fiction for environmental understanding as hermeneutic, a form of conceptualising place which interprets experience and perception. The four writers for young people discussed are Ernest Thompson Seton, Kenneth Grahame, Michelle Paver and Philip Pullman. We develop the concept of critical dialogue, and link this to Crick's demand for active democratic citizenship. We illustrate the educational potential for environmental discussions based on literature leading to deeper understanding of place and environment, encouraging the belief in young people that they can be and become agents for change. We develop from Zimbardo the key concept of heroic resister to encourage young people to overcome peer pressure. We conclude with a call to develop a greater awareness of the potential of fiction for learning, and for writers to produce more focused stories engaging with environmental responsibility and activism
``Non-factorizable'' terms in hadronic B-meson weak decays
The branching ratios for the hadronic B-meson weak decays B -> J/psi K and B
-> D pi are used to extract the size of the ``non-factorizable'' terms in the
decay amplitudes. It is pointed out that the solutions are not uniquely
determined. In the B -> J/psi K case, a 2-fold ambiguity can be removed by
analyzing the contribution of this decay to B -> K l+ l-. In the B -> D pi
case, a 4-fold ambiguity can only be removed if the ``non-factorizable'' terms
are assumed to be a small correction to the vacuum insertion result.Comment: 15 pages (and 1 figure, available upon request), TRIUMF report no.
TRI-PP-94-7
Multiple Parton Interactions in Z+jets production at the LHC. A comparison of factorized and non--factorized double parton distribution functions
We examine the contribution of Multiple Parton Interactions to Z+n-jets
production at the LHC, n=2,3,4, where the Z boson is assumed to decay
leptonically. We compare the results obtained with the correlated GS09 double
parton distribution function with those obtained with two instances of fully
factorized single parton distribution functions: MSTW2008LO and CTEQ6LO. It
appears quite feasible to measure the MPI contribution to Z+2/3/4 jets already
in the first phase of the LHC with a total luminosity of one inverse femtobarn
at 7 TeV. If as expected the trigger threshold for single photons is around 80
GeV, Z+2-jets production may well turn out to be more easily observable than
the gamma+3-jets channel. The MPI cross section is dominated by relatively soft
events with two jets balancing in transverse momentum.Comment: 15 pages, 3 plot
Isospin Breaking in the Pion-Nucleon Coupling from QCD Sum Rules
We use QCD sum rules for the three point function of a pseudoscalar and two
nucleonic currents in order to estimate the charge dependence of the pion
nucleon coupling constant coming from isospin violation in the
strong interaction. The effect can be attributed primarily to the difference of
the quark condensates . For the splitting
we obtain an interval of to , the uncertainties coming mainly from the input
parameters. The charged pion nucleon coupling is found to be the average of
and . Electromagnetic effects are not included.Comment: 18 pages (REVTeX) + 2 figures (as PostScript), to be published in
PRC, replaced with final version: inclusion of pi-eta mixing and N -> N*
transition
- …