121663887
Mass and transverse momentum dependence of the dielectron yield in p-Be collisions at 4.9 GeV
We present the invariant mass and transverse momentum dependence of direct electron-positron pair production in {ital p}-Be collisions at a beam kinetic energy of 4.9 GeV. The acceptance of our apparatus is shown to have no significant effect for masses above 0.15 GeV. After a correction is made for the available phase space, the transverse momentum dependence of the data is found to be comparable to hadron-hadron observations. A phenomenological calculation involving {pi}{sup +}{pi}{sup {minus}} annihilation into {ital e}{sup +}e{sup {minus}} is shown to be in good agreement with our measurements.
44598663
Measurement of dielectron production in niobium-niobium collisions at 1.05 GeV/nucleon.
A dielectron signal for pair masses greater than [ital M][sub [pi]] is observed in Nb+Nb collisions at 1.05 GeV/nucleon beam kinetic energy. The invariant mass spectrum and the associated multiplicity distribution are presented. Comparisons are made with previous cross section measurements in [ital p]+Be and Ca+Ca.
119395992
Dilepton production from p-p to CaCa at the Bevalac
Abstract The DLS collaboration has recently completed a high statistics study of dilepton production at the Bevalac. In particular, we have measured dielectrons (e + e − ) from p - p and p - d collisions to understand the basic dilepton production mechanisms in the energy range from 1.05 – 4.9 GeV. These data can be used to determine the basic processes which contribute to nucleon-nucleon dilepton production such as hadronic bremsstrahlung, vector meson processes, and hadronic Dalitz decay. The data show that a simple elastic bremsstrahlung calculation is insufficient to explain the data. Theoretical models are compared with the data. A new high statistics study of Ca  Ca at 1.05 A·GeV has been made to study the collectivity of A - A collisions.
6986761
Threshold behavior of electron pair production in p-Be collisions.
We report on the measurements of electron pair production in /ital p/-Becollisions at 1.0, 2.1, and 4.9 GeV beam kinetic energies. The invariant-massand transverse-momentum spectra are presented, along with the total crosssections. A rapid decrease in the integrated cross section is observed as thebeam energy is reduced. Comparison of the excitation function for dielectron(/ital e//sup +/e/sup /minus//) and dipion (..pi../sup +/..pi../sup /minus//)production suggests that the dominant production mechanism at beam kineticenergies 2.1 and 4.9 GeV may be ..pi../sup +/..pi../sup /minus// annihilation.
121663887
Mass and transverse momentum dependence of the dielectron yield in p-Be collisions at 4.9 GeV
We present the invariant mass and transverse momentum dependence of direct electron-positron pair production in {ital p}-Be collisions at a beam kinetic energy of 4.9 GeV. The acceptance of our apparatus is shown to have no significant effect for masses above 0.15 GeV. After a correction is made for the available phase space, the transverse momentum dependence of the data is found to be comparable to hadron-hadron observations. A phenomenological calculation involving {pi}{sup +}{pi}{sup {minus}} annihilation into {ital e}{sup +}e{sup {minus}} is shown to be in good agreement with our measurements.
118235333
Dielectron Production in Nucleus+Nucleus Collisions at 1.05 GeV/nucleon
Measurements of dielectron production in heavy-ion collisions are valuable probes into the dynamics of the collision process. While the hadronic participants of the collision are subject to strong final state interactions, the coupling of the electron-positron pair to the collision medium is electromagnetic. Dielectrons, therefore suffer little rescattering leaving the interaction and can retain information about their production origins, probing even the early stages in the evolution of the collision. The DiLepton Spectrometer (DLS) collaboration`s original measurements of dielectron production established the existence of the signal at Bevalac energies. The 1992- 93 DLS measurements in nucleus+Nucleus collisions at a kinetic beam energy of 1.05 {ital GeV/nucleon} are the subject of this presentation.
18086741
What is in One: Uncertainty quantum and Continuum Hypothesis
The concept of measurement is discussed. It is argued that counting process in mathematics is also measurement which requires a basic unit. The idea of scale is put forward. The basic unit itself, which are composed of the infinitesimal of uncertainty quantum, can be regarded as infinite in another scale. Thus infinite, infinitesimal and integer " 1 " are unified. It is proposed that multiplication changes to summation when it is transformed to a larger scale. The Continuum Hypothesis is proved to be correct after a scale transformation.
119184427
Analysis of the vector and axialvector Bc mesons with QCD sum rules
In this article, we study the vector and axialvector Bc mesons with QCD sum rules, and make reasonable predictions for the masses and decay constants, then calculate the leptonic decay widths. The present predictions for the masses and decay constants can be confronted with the experimental data in the future. We can also take the masses and decay constants as basic input parameters and study other phenomenological quantities with the three-point vacuum correlation functions via QCD sum rules.
119184301
The Zb(10610) and Zb(10650) as axial-vector tetraquark states in the QCD sum rules
Abstract In this article, we study the axial-vector mesons Z b ( 10 610 ) and Z b ( 10 650 ) with the C γ μ – C γ 5 type and C γ μ – C γ ν type interpolating currents, respectively, by carrying out the operator product expansion to the vacuum condensates up to dimension 10. In calculations, we explore the energy scale dependence of the QCD spectral densities of the hidden bottom tetraquark states in detail for the first time, and suggest a formula μ = M X / Y / Z 2 − ( 2 M b ) 2 with the effective mass M b = 5.13 GeV to determine the energy scales. The numerical results favor assigning the Z b ( 10 610 ) and Z b ( 10 650 ) as the C γ μ – C γ 5 type and C γ μ – C γ ν type hidden bottom tetraquark states, respectively. We obtain the mass of the J PC = 1 + + hidden bottom tetraquark state as a byproduct, which can be compared to the experimental data in the futures. Furthermore, we study the strong decays Z b ± ( 10 610 ) → ϒ π ± , η b ρ ± with the three-point QCD sum rules, the decay widths also support assigning the Z b ( 10 610 ) as the C γ μ – C γ 5 type hidden bottom tetraquark state.
38889804
Experimental demonstration of plasma-drag acceleration of a dust cloud to hypervelocities.
Simultaneous acceleration of hundreds of dust particles to hypervelocities by collimated plasma flows ejected from a coaxial gun is demonstrated. Graphite and diamond grains with radii between 5 and 30 microm, and flying at speeds up to 3.7 km/s, have been recorded with a high-speed camera. The observations agree well with a model for plasma-drag acceleration of microparticles much larger than the plasma screening length.
119627570
How to Resum Feynman Graphs
In this paper, we reformulate the combinatorial core of constructive quantum field theory. We define universal rational combinatorial weights for pairs made of a graph and any of its spanning trees. These weights are simply the percentage of Hepp’s sectors of the graph in which the tree is leading, in the sense of Kruskal’s greedy algorithm. Our main new mathematical result is an integral representation of these weights in terms of the positive matrix appearing in the symmetric “BKAR” Taylor forest formula. Then, we explain how the new constructive technique called Loop Vertex Expansion reshuffles according to these weights the divergent series of the intermediate field representation into a convergent series which is the Borel sum of the ordinary perturbative Feynman’s series.