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A theory of finite structures

Author: Leivant Daniel M
Publication venue
Publication date: 2020
Field of study

We develop a novel formal theory of finite structures, based on a view of finite structures as a fundamental artifact of computing and programming, forming a common platform for computing both within particular finite structures, and in the aggregate for computing over infinite data-types construed as families of finite structures. A "finite structure" is here a finite collection of finite partial-functions, over a common universe of atoms. The theory is second-order, as it uses quantification over finite functions. Our formal theory FS uses a small number of fundamental axiom-schemas, with finiteness enforced by a schema of induction on finite partial-functions. We show that computability is definable in the theory by existential formulas, generalizing Kleene's Theorem on the Sigma-1 definability of RE sets, and use that result to prove that FS is mutually interpretable with Peano Arithmetic

Monte Carlo Simulations of Trapped Ultracold Neutrons in the UCN $\tau$ Experiment

In the UCN τ experiment, ultracold neutrons (UCN) are confined by magnetic fields and the Earth's gravitational field. Field-trapping mitigates the problem of UCN loss on material surfaces, which caused the largest correction in prior neutron experiments using material bottles. However, the neutron dynamics in field traps differ qualitatively from those in material bottles. In the latter case, neutrons bounce off material surfaces with significant diffusivity and the population quickly reaches a static spatial distribution with a density gradient induced by the gravitational potential. In contrast, the field-confined UCN—whose dynamics can be described by Hamiltonian mechanics—do not exhibit the stochastic behaviors typical of an ideal gas model as observed in material bottles. In this report, we will describe our efforts to simulate UCN trapping in the UCN τ magnetogravitational trap. We compare the simulation output to the experimental results to determine the parameters of the neutron detector and the input neutron distribution. The tuned model is then used to understand the phase-space evolution of neutrons observed in the UCN τ experiment. We will discuss the implications of chaotic dynamics on controlling the systematic effects, such as spectral cleaning and microphonic heating, for a successful UCN lifetime experiment to reach a 0.01% level of precision

Council on East Asian Libraries Statistics 2017-2018 for North American Institutions

Author: Doll Vickie Fu
Liu Wen-ling Diana
Publication venue
Publication date: 2020
Field of study

But What Does it Mean? Competition between Products Carrying Alternative Green Labels when Consumers are Active Acquirers of Information

Author: A. Heyes,
Sandeep Kapur,
P.W. Kennedy,
S. Martin,
J.W. Maxwell,
Publication venue
Publication date: 2020
Field of study

Programs that certify the environmental (or other social) attributes of firms are common. But the proliferation of labeling schemes makes it difficult for consumers to know what each one means—what level of “greenness” does a particular label imply? We provide the first model in which consumers can expend effort to learn what labels mean. The relationship between information acquisition costs, firm pricing decisions, the market shares obtained by alternatively labeled goods and a brown “backstop” good, and total environmental impact proves complex. Consumer informedness can have perverse implications. In plausible cases a reduction in the cost of information damages environmental outcomes. Our results challenge the presumption that provision of environmental information to the public is necessarily good for welfare or the environment

Amplitude analysis of $D^{+} \rightarrow K_{S}^{0} \pi^{+} \pi^{+} \pi^{-}$

Author: M. Ablikim,
Mitchell R. E., et al.
Publication venue
Publication date: 2020
Field of study

The decay

D^{+} \rightarrow K_{S}^{0} \pi^{+} \pi^{+} \pi^{-}

is studied with an amplitude analysis using a data set of 2.93fb

^{-1}

e^+e^-

collisions at the

\psi(3770)

peak accumulated by the BESIII detector. Intermediate states and non-resonant components, and their relative fractions and phases have been determined. The significant amplitudes, which contribute to the model that best fits the data, are composed of five quasi-two-body decays

K_{S}^{0} a_{1}(1260)^{+}

\bar{K}_{1}(1270)^{0} \pi^{+}

\bar{K}_{1}(1400)^{0} \pi^{+}

\bar{K}_{1}(1650)^{0} \pi^{+}

, and

\bar{K}(1460)^{0} \pi^{+}

, a three-body decays

K_{S}^{0}\pi^{+}\rho^{0}

as well as a non-resonant component

K_{S}^{0}\pi^{+}\pi^{+}\pi^{-}

. The dominant amplitude is

K_{S}^{0} a_{1}(1260)^{+}

, , with a fit fraction of (40.3±2.1±2.9)%, where the first and second uncertainties are statistical and systematic, respectively

Amplitude analysis of $D_{s}^{+} \rightarrow \pi^{+}\pi^{0}\eta$ and first observation of the pure $W$ -annihilation decays $D_{s}^{+} \rightarrow a_{0}(980)^{+}\pi^{0}$ and $D_{s}^{+} \rightarrow a_{0}(980)^{0}\pi^{+}$

Author: Ablikim M.
Mitchell R. E., et al.
Publication venue
Publication date: 2020
Field of study

We present the first amplitude analysis of the decay

D_{s}^{+} \rightarrow \pi^{+}\pi^{0}\eta

. We use an

e^+e^−

collision data sample corresponding to an integrated luminosity of 3.19fb

^{−1}

collected with the BESIII detector at a center-of-mass energy of 4.178 GeV. We observe for the first time the pure

W

-annihilation decays

D_{s}^{+} \rightarrow a_{0}(980)^{+}\pi^{0}

and

D_{s}^{+} \rightarrow a_{0}(980)^{0}\pi^{+}

. We measure the absolute branching fractions

\mathcal{B}(D_{s}^{+} \rightarrow a_{0}(980)^{+(0)}\pi^{0^(+)}, a_{0}(980)^{+(0)} \to \pi^{+(0)}\eta) = (1.46\pm0.15_{\rm stat.}\pm0.23_{\rm sys.})

, which is larger than the branching fractions of other measured pure

W

-annihilation decays by at least one order of magnitude. In addition, we measure the branching fraction of

D_{s}^{+} \rightarrow \pi^{+}\pi^{0}\eta

with significantly improved precision

First observation of the decay $\chi_{cJ}\to \Sigma^{+}\bar{p}K_{S}^{0}+c.c. ~(J = 0, 1, 2)$

Author: Ablikim M.
Mitchell R. E., et al.
Publication venue
Publication date: 2020
Field of study

Using E1 radiative transitions

\psi(3686) \to \gamma\chi_{cJ}

from a sample of

(448.1 \pm 2.9)\times10^{6} \psi(3686)

events collected with the BESIII detector, the decays

\chi_{cJ}\to \Sigma^{+}\bar{p}K_{S}^{0}+c.c.~(J = 0, 1, 2)

are studied. The decay branching fractions are measured to be

\mathcal{B}(\chi_{c0}\to \Sigma^{+}\bar{p}K_{S}^{0}+c.c.) = (3.52 \pm 0.19\pm 0.21)\times10^{-4}

\mathcal{B}(\chi_{c1}\to \Sigma^{+}\bar{p}K_{S}^{0}+c.c.) = (1.53 \pm 0.10\pm 0.08)\times10^{-4}

, and

\mathcal{B}(\chi_{c2}\to \Sigma^{+}\bar{p}K_{S}^{0}+c.c.) = (8.25 \pm 0.83 \pm 0.49)\times10^{-5}

, where the first and second uncertainties are the statistical and systematic ones, respectively. No evident intermediate resonances are observed in the studied processes

Measurement of branching fractions of $\psi(3686)\to \phi\eta^\prime, \phi f_1(1285)$ and $\phi \eta(1405)$

Author: Ablikim M.
Mitchell R. E., et al.
Publication venue
Publication date: 2020
Field of study

Using a sample of

448.1×10^6 \psi(3686)

events collected with the BESIII detector, we perform a study of the decay

\psi(3686) \rightarrow \phi \pi^{+}\pi^{-}\eta

. The branching fraction of

\psi(3686)\rightarrow\phi\eta^\prime

is determined to be

(1.51\pm0.16\pm0.12)\times 10^{-5}

, which is consistent with the previous measurement but with significantly improved precision. The resonances

f_1(1285)

and

\eta(1405)

are clearly observed in the

\pi^{+}\pi^{-}\eta

mass spectrum with statistical significances of 18

\sigma

and 9.7

\sigma

, respectively. The corresponding product branching fractions are measured to be

\mathcal{B}(\psi(3686)\rightarrow\phi f_{1}(1285),f_{1}(1285)\rightarrow\pi^{+}\pi^{-}\eta) =(1.03\pm0.10\pm0.09)\times 10^{-5}

and

\mathcal{B}(\psi(3686)\rightarrow\phi\eta(1405),\eta(1405)\rightarrow\pi^{+}\pi^{-}\eta) =(8.46\pm1.37\pm0.92)\times 10^{-6}

Measurement of the phase between strong and electromagnetic amplitudes of $J/\psi$ decays

Author: Ablikim M.
Mitchell R. E., et al.
Publication venue
Publication date: 2020
Field of study

Using 16 energy points of

e^+e^−

annihilation data collected in the vicinity of the

J/\psi

resonance with the BESIII detector and with a total integrated luminosity of around 100 pb

^{−1}

, we study the relative phase between the strong and electromagnetic amplitudes of

J/\psi

decays. The relative phase between Jψ electromagnetic decay and the continuum process (

e^+e^−

annihilation without the

J/\psi

resonance) is confirmed to be zero by studying the cross section lineshape of

\mu^{+}\mu^{-}

production. The relative phase between

J/\psi

strong and electromagnetic decays is then measured to be

(84.9\pm3.6)^\circ

(-84.7\pm3.1)^\circ

for the

2(\pi^{+}\pi^{-})\pi^{0}

final state by investigating the interference pattern between the

J/\psi

decay and the continuum process. This is the first measurement of the relative phase between

J/\psi

strong and electromagnetic decays into a multihadron final state using the lineshape of the production cross section. We also study the production lineshape of the multihadron final state

\eta\pi^{+}\pi^{-}

with

\eta\to\pi^{+}\pi^{-}\pi^{0}

, which provides additional information about the phase between the

J/\psi

electromagnetic decay amplitude and the continuum process. Additionally, the branching fraction of

J/\psi\to 2(\pi^{+}\pi^{-})\pi^{0}

is measured to be (4.73±0.44)% or (4.85±0.45)%, and the branching fraction of

J/\psi\to\eta\pi^{+}\pi^{-}

is measured to be (3.78±0.68)×10

^{−4}

. Both of them are consistent with the world average values. The quoted uncertainties include both statistical and systematic uncertainties, which are mainly caused by the low statistics

Search for the decay $D_s^+\rightarrow \gamma e^+\nu_e$

Author: Ablikim M.
Mitchell R. E., et al.
Publication venue
Publication date: 2020
Field of study

A search for the rare radiative leptonic decay

D_s^+\to\gamma e^+\nu_e

is performed for the first time using electron-positron collision data corresponding to an integrated luminosity of 3.19 fb

^{−1}

, collected with the BESIII detector at a center-of-mass energy of 4.178 GeV. No evidence for the

D_s^+\to\gamma e^+\nu_e

decay is seen and an upper limit of

\mathcal B(D_s^+\to\gamma e^+\nu_e)0.01

GeV

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