China Center of Advanced Science and Technology

About: China Center of Advanced Science and Technology is a facility organization based out in Beijing, China. It is known for research contribution in the topics: Magnetic field & Branching fraction. The organization has 924 authors who have published 1408 publications receiving 27714 citations. The organization is also known as: CCAST.

Design and construction of the BESIII detector

Abstract: This paper will discuss the design and construction of BESIII, which is designed to study physics in the τ -charm energy region utilizing the new high luminosity BEPCII double ring e + e − collider. The expected performance will be given based on Monte Carlo simulations and results of cosmic ray and beam tests. In BESIII, tracking and momentum measurements for charged particles are made by a cylindrical multilayer drift chamber in a 1 T superconducting solenoid. Charged particles are identified with a time-of-flight system based on plastic scintillators in conjunction with dE/dx (energy loss per unit pathlength) measurements in the drift chamber. Energies of electromagnetic showers are measured by a CsI(Tl) crystal calorimeter located inside the solenoid magnet. Muons are identified by arrays of resistive plate chambers in a steel magnetic yoke for the flux return. The level 1 trigger system, data acquisition system and the detector control system based on networked computers will also be described.

Observation of a charged charmoniumlike structure in e+ e- → (D* D*)± π∓ at √s = 4.26 GeV.

Abstract: We study the process e(+)e(-) -> pi(+)pi(-) J/psi at a center-of-mass energy of 4.260 GeV using a 525 pb(-1) data sample collected with the BESIII detector operating at the Beijing Electron Positron Collider. The Born cross section is measured to be (62.9 +/- 1.9 +/- 3.7) pb, consistent with the production of the Y(4260). We observe a structure at around 3.9 GeV/c(2) in the pi(+/-) J/psi mass spectrum, which we refer to as the Z(c)(3900). If interpreted as a new particle, it is unusual in that it carries an electric charge and couples to charmonium. A fit to the pi(+/-) J/psi invariant mass spectrum, neglecting interference, results in a mass of (3899.0 +/- 3.6 +/- 4.9) MeV/c(2) and a width of (46 +/- 10 +/- 20) MeV. Its production ratio is measured to be R = (sigma(e(+)e(-) -> pi(+/-) Z(c)(3900)(-/+) -> pi(+)pi(-) J/psi)/sigma(e(+)e(-) -> pi(+)pi(-) J/psi)) = (21.5 +/- 3.3 +/- 7.5)%. In all measurements the first errors are statistical and the second are systematic.

Phenomenological study of the size effect on phase transitions in ferroelectric particles

Abstract: Size effects on the Curie temperature and spontaneous polarization in spherical particles are studied using Landau phenomenological theory. The extrapolation length is shown to be size dependent. The spatial distribution of polarization is obtained. The size dependence of the polarization is calculated whereby a size-driven phase transition is demonstrated. The Curie temperature as a function of particle size is calculated. Theoretical results are compared with the experimental in the literature and good agreement is obtained.

Observation of a Charged Charmoniumlike Structure Z(c) (4020) and Search for the Z(c) (3900) in e(+)e(-) -> pi(+) pi(-)h(c)

Abstract: We study e(+)e(-) -> pi(+) pi(-)h(c) at center-of-mass energies from 3.90 to 4.42 GeV by using data samples collected with the BESIII detector operating at the Beijing Electron Positron Collider. The Born cross sections are measured at 13 energies and are found to be of the same order of magnitude as those of e(+)e(-) -> pi(+) pi(-) J/Psi but with a different line shape. In the pi(+/-)h(c) mass spectrum, a distinct structure, referred to as Z(c)(4020) is observed at 4. 02 GeV/c(2). The Z(c)(4020) carries an electric charge and couples to charmonium. A fit to the pi(+/-)h(c) invariant mass spectrum, neglecting possible interferences, results in a mass of (4022.9 +/- 0.8 +/- 2.7) MeV/c(2) and a width of (7.9 +/- 2.7 +/- 2.6) MeV for the Z(c)(4020), where the first errors are statistical and the second systematic. The difference between the parameters of this structure and the Z(c) (4025) observed in the D*(D) over bar* final state is within 1.5 sigma, but whether they are the same state needs further investigation. No significant Z(c)(3900) signal is observed, and upper limits on the Z(c)(3900) production cross sections in pi +/- h(c) at center-of-mass energies of 4.23 and 4.26 GeVare set.

Eigenvectors of two particles’ relative position and total momentum

Abstract: We give the explicit form of the common eigenvectors of the relative position ${\mathit{Q}}_{1}$-${\mathit{Q}}_{2}$ and the total momentum ${\mathit{P}}_{1}$+${\mathit{P}}_{2}$, of two particles which were considered by Einstein, Podolsky, and Rosen [Phys. Rev. 47, 777 (1935)] in their argument that the quantum-mechanical state vector is not complete. Orthonormality and completeness of such eigenvectors, as well as their use in constructing the unitary operator for simultaneously squeezing ${\mathit{Q}}_{1}$-${\mathit{Q}}_{2}$ and ${\mathit{P}}_{1}$+${\mathit{P}}_{2}$, are derived by using the technique of integration within an ordered product of operators.