84 research outputs found
A discrete mutualism model: analysis and exploration of a financial application
We perform a stability analysis on a discrete analogue of a known, continuous model of
mutualism. We illustrate how the introduction of delays affects the asymptotic stability
of the system’s positive nontrivial equilibrium point. In the second part of the paper we
explore the insights that the model can provide when it is used in relation to interacting
financial markets. We also note the limitations of such an approach
Branching Fractions for D0 -> K+K- and D0 -> pi+pi-, and a Search for CP Violation in D0 Decays
Using the large hadroproduced charm sample collected in experiment E791 at
Fermilab, we have measured ratios of branching fractions for the two-body
singly-Cabibbo-suppressed charged decays of the D0:
(D0 -> KK)/(D0 -> Kpi) = 0.109 +- 0.003 +- 0.003,
(D0 -> pipi)/(D0 -> Kpi) = 0.040 +- 0.002 +- 0.003, and
(D0 -> KK)/(D0 -> pipi) = 2.75 +- 0.15 +- 0.16. We have looked for
differences in the decay rates of D0 and D0bar to the CP eigenstates K+K- and
pi+pi-, and have measured the CP asymmetry parameters
A_CP(K+K-) = -0.010 +- 0.049 +- 0.012 and
A_CP(pi+pi-) = -0.049 +- 0.078 +- 0.030, both consistent with zero.Comment: 10 Postscript pages, including 2 figures. Submitted to Phys. Lett.
Asymmetries between the production of D+ and D- mesons from 500 GeV/c pi- nucleon interactions as a function of xF and pt**2
We present asymmetries between the production of D+ and D- mesons in Fermilab
experiment E791 as a function of xF and pt**2. The data used here consist of
74,000 fully-reconstructed charmed mesons produced by a 500 GeV/c pi- beam on C
and Pt foils. The measurements are compared to results of models which predict
differences between the production of heavy-quark mesons that have a light
quark in common with the beam (leading particles) and those that do not
(non-leading particles). While the default models do not agree with our data,
we can reach agreement with one of them, PYTHIA, by making a limited number of
changes to parameters used
Measurement of the form-factor ratios for D+ --> K* l nu
The form factor ratios rv=V(0)/A1(0), r2=A2(0)/A1(0) and r3=A3(0)/A1(0) in
the decay D+ --> K* l nu, K* -->K-pi+ have been measured using data from charm
hadroproduction experiment E791 at Fermilab. From 3034 (595) signal
(background) events in the muon channel, we obtain rv=1.84+-0.11+-0.09,
r2=0.75+-0.08+-0.09 and, as a first measurement of r3, we find 0.04+-0.33
+-0.29. The values of the form factor ratios rv and r2 measured for the muon
channel are combined with the values of rv and r2 that we have measured in the
electron channel. The combined E791 results for the muon and electron channels
are rv=1.87+-0.08+-0.07 and r2=0.73+-0.06+-0.08.Comment: 9 pages + 3 figures ; submitted to PL
Search for Rare and Forbidden Dilepton Decays of the D+, Ds, and D0 Charmed Mesons
We report the results of a search for flavor-changing neutral current,
lepton-flavor violating, and lepton-number violating decays of D+, Ds, and D0
mesons (and their antiparticles) into modes containing muons and electrons.
Using data from Fermilab charm hadroproduction experiment E791, we examine the
pi,l,l and K,l,l decay modes of D+ and Ds and the l+l- decay modes of D0. No
evidence for any of these decays is found. Therefore, we present
branching-fraction upper limits at 90% confidence level for the 24 decay modes
examined. Eight of these modes have no previously reported limits, and fourteen
are reported with significant improvements over previously published results.Comment: 12 pages, 3 figures, LaTeX, elsart.cls, epsf.sty, amsmath.sty
Submitted to Physics Letters
Search for CP Violation in Charged D Meson Decays
We report results of a search for CP violation in the singly
Cabibbo-suppressed decays D+ -> K- K+ pi+, phi pi+, K*(892)0 K+, and pi- pi+
pi+ based on data from the charm hadroproduction experiment E791 at Fermilab.
We search for a difference in the D+ and D- decay rates for each of the final
states. No evidence for a difference is seen. The decay rate asymmetry
parameters A(CP), defined as the difference in the D+ and D- decay rates
divided by the sum of the decay rates, are measured to be: A(CP)(K K pi) =
-0.014 +/- 0.029, A(CP)(phi pi) = -0.028 +/- 0.036, A(CP)(K*(892) K) = -0.010
+/- 0.050, and A(CP)(pi pi pi) = -0.017 +/- 0.042.Comment: 13 pages, 5 figures, 1 table; Elsevier LaTe
Response of a Lake Michigan coastal lake to anthropogenic catchment disturbance
A paleolimnological investigation of post-European sediments in a Lake Michigan coastal lake was used to examine the response of Lower Herring Lake to anthropogenic impacts and its role as a processor of watershed inputs. We also compare the timing of this response with that of Lake Michigan to examine the role of marginal lakes as ‘early warning’ indicators of potential changes in the larger connected system and their role in buffering Lake Michigan against anthropogenic changes through biotic interactions and material trapping. Sediment geochemistry, siliceous microfossils and nutrient-related morphological changes in diatoms, identified three major trophic periods in the recent history of the lake. During deforestation and early settlement (pre-1845–1920), lake response to catchment disturbances results in localized increases in diatom abundances with minor changes in existing communities. In this early phase of disturbance, Lower Herring Lake acts as a sediment sink and a biological processor of nutrient inputs. During low-lake levels of the 1930s, the lake goes through a transitional period characterized by increased primary productivity and a major shift in diatom communities. Post-World War II (late 1940s–1989) anthropogenic disturbances push Lower Herring Lake to a new state and a permanent change in diatom community structure dominated by Cyclotella comensis . The dominance of planktonic summer diatom species associated with the deep chlorophyll maximum (DCM) is attributed to epilimnetic nutrient depletion. Declining Si:P ratios are inferred from increased sediment storage of biogenic silica and morphological changes in the silica content of Aulacoseira ambigua and Stephanodiscus niagarae . Beginning in the late 1940s, Lower Herring Lake functions as a biogeochemical processor of catchment inputs and a carbon, nutrient and silica sink. Microfossil response to increased nutrients and increased storage of biogenic silica in Lower Herring Lake and other regional embayments occur approximately 20–25 years earlier than in a nearby Lake Michigan site. Results from this study provide evidence for the role of marginal lakes and bays as nutrient buffering systems, delaying the impact of anthropogenic activities on the larger Lake Michigan system.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43091/1/10933_2004_Article_1688.pd
Differential cross sections, charge production asymmetry, and spin-density matrix elements for D*(2010) produced in 500 GeV/c pi^- nucleon interactions
We report differential cross sections for the production of D*(2010) produced
in 500 GeV/c pi^- nucleon interactions from experiment E791 at Fermilab, as
functions of Feynman-x (x_F) and transverse momentum squared (p_T^2). We also
report the D* +/- charge asymmetry and spin-density matrix elements as
functions of these variables. Investigation of the spin-density matrix elements
shows no evidence of polarization. The average values of the spin alignment are
\eta= 0.01 +- 0.02 and -0.01 +- 0.02 for leading and non-leading particles,
respectively.Comment: LaTeX2e (elsart.cls). 13 pages, 6 figures (eps files). Submitted to
Physics Letters
Mass Splitting and Production of and Measured in N Interactions
From a sample of decaying to the
final state, we have observed, in the hadroproduction experiment E791 at
Fermilab, and through
their decays to . The mass difference ) is measured to be ; for
, we find .
The rate of production from decays of the triplet is
(22\pm 2\pm 3) {%} of the total production assuming equal rate
of production from all three, as measured for and .
We do not observe a statistically significant baryon-antibaryon
production asymmetry. The and spectra of from
decays are observed to be similar to those for all 's
produced.Comment: 15 pages, uuencoded postscript 3 figures uuencoded, tar-compressed
fil
The doubly Cabibbo-suppressed decay
We report the observation of the doubly Cabibbo-suppressed decay in data from Fermilab charm hadroproduction experiment E791. With
a signal of 59 \pm 13 events we measured the ratio of the branching fraction
for this mode to that of the Cabibbo-favored decay to
be . A Dalitz plot analysis was performed to search for
resonant structures.Comment: 10 pages, 5 eps figures, RevTe
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