42564053
Highlights from BESIII experiment
BESIII had collected large data samples on J/ψ and ψ ´ peaks during the first run in 2009. We review recent results on charmonium decays and hadron spectroscopy. The prospects on open charm physics are also discussed.
120924995
Centrality, azimuthal and rapidity dependence of two-particle transverse-momentum correlation in relativistic heavy ion collisions
The centrality, azimuthal and rapidity dependence of two-particle transverse-momentum correlations are studied for Au-Au collision at 200 GeV using RQMD (relativistic quantum molecular dynamics) with and without final hadron re-scattering models. The influences of the re-scattering effects on the measured correlations are discussed. The results are compared with those from current heavy ion experiments.
204172260
New Observations on Light Hadron Spectroscopy at BESIII
121577507
Two-charge-particle azimuthal correlations and the azimuthal balance function in RQMD and AMPT
Two-charge-particle azimuthal correlations (TCPAC) and the azimuthal charge balance function (ACBF) are compared with anisotropic flow by using transport models, RQMD and AMPT. In these two models, TCPAC has the same centrality dependence as anisotropic flow. The momentum conservation contributes only back-to-back correlations in TCPAC, which are well separated from small angle correlations caused by anisotropic transverse momentum distribution, while the centrality dependence of ACBF is different from those of anisotropic flow and TCPAC. This indicates that ACBF cannot be used as another presentation of anisotropic flow, as expected from thermal models.
121778142
Confirmation of pp̄ Mass Threshold Enhancement and X(1835) at BESIII
pp mass threshold enhancement is studied using the data samples of J/ψ and ψ′ collected with BESIII detector in 2009. The enhancement is evident in J/ψ radiative decay, which is consistent with BESII result. No significant narrow enhancement is observed in ψ′ radiative decay. The study of J/ψ→γπ+π−η′ is also presented, it is also consistent with BESII result, which shows that the X(1835) is confirmed at BESIII.
119231853
Basics of Generalized Unitarity
We review generalized unitarity as a means for obtaining loop amplitudes from on-shell tree amplitudes. The method is generally applicable to both supersymmetric and non-supersymmetric amplitudes, including non-planar contributions. Here, we focus mainly on Yang–Mills theory, in the context of on-shell superspaces. Given the need for regularization at loop level, we also review a six-dimensional helicity-based superspace formalism and its application to dimensional and massive regularizations. An important feature of the unitarity method is that it offers a means for carrying over any identified tree-level property of on-shell amplitudes to loop level, though sometimes in a modified form. We illustrate this with examples of dual conformal symmetry and a recently discovered duality between color and kinematics. This article is an invited review for a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Scattering amplitudes in gauge theories’.
6593967
String interactions on the random lattice
Abstract We combine two partons on a random lattice as a vector state. In the ladder approximation, we find that such states have 1 / p 2 propagators (after tuning the mass to vanish). We also construct some diagrams which are very similar to 3-string vertices in string field theory for the first oscillator mode. Attaching 3 such lattice states to these vertices, we get Yang–Mills and F 3 interactions up to 3-point as from bosonic string (field) theory. This gives another view of a gauge field as a bound state in a theory whose only fundamental fields are scalars.
119118512
Worldgraph approach to Yang-Mills amplitudes from N = 2 spinning particle
By coupling the N = 2 spinning particle to background vector fields, we construct Yang-Mills amplitudes for trees and one loop. The vertex operators are derived through coupling the BRST charge; therefore background gauge invariance is manifest, and the Yang-Mills ghosts are automatically included in loop calculations by worldline ghosts. Inspired by string calculations, we extend the usual worldline approach to incorporate more ``generalized" 1D manifolds. This new approach should be useful for constructing higher-point and higher-loop amplitudes.
34930280
Equivalent D = 3 supergravity amplitudes from double copies of three-algebra and two-algebra gauge theories.
We show that three-dimensional supergravity amplitudes can be obtained as double copies of either three-algebra super-Chern-Simons matter theory or two-algebra super-Yang-Mills theory when either theory is organized to display the color-kinematics duality. We prove that only helicity-conserving four-dimensional gravity amplitudes have nonvanishing descendants when reduced to three dimensions, implying the vanishing of odd-multiplicity S-matrix elements, in agreement with Chern-Simons matter theory. We explicitly verify the double-copy correspondence at four and six points for N = 12,10,8 supergravity theories and discuss its validity for all multiplicity.
119182093
ABJM amplitudes and the positive orthogonal Grassmannian
A bstractA remarkable connection between perturbative scattering amplitudes of four dimensional planar SYM, and the stratification of the positive Grassmannian, was revealed in the seminal work of Arkani-Hamed et al. Similar extension for three-dimensional ABJM theory was proposed. Here we establish a direct connection between planar scattering amplitudes of ABJM theory, and singularities thereof, to the stratification of the positive orthogonal Grassmannian. In particular, scattering processes are constructed through on-shell diagrams, which are simply iterative gluing of the fundamental four-point amplitude. Each diagram is then equivalent to the merging of fundamental OG2 orthogonal Grassmannian to form a larger OGk, where 2k is the number of external particles. The invariant information that is encoded in each diagram is precisely this stratification. This information can be easily read off via permutation paths of the on-shell diagram, which also can be used to derive a canonical representation of OGk that manifests the vanishing of consecutive minors as the singularity of all on-shell diagrams. Quite remarkably, for the BCFW recursion representation of the tree-level amplitudes, the on-shell diagram manifests the presence of all physical factorization poles, as well as the cancellation of the spurious poles. After analytically continuing the orthogonal Grassmannian to split signature, we reveal that each on-shell diagram in fact resides in the positive cell of the orthogonal Grassmannian, where all minors are positive. In this language, the amplitudes of ABJM theory is simply an integral of a product of d log forms, over the positive orthogonal Grassmannian.