分类: 物理学 >> 核物理学 提交时间: 2016-09-05
摘要: The electromagnetic form factors and low-energy observables of deuteron are studied with the help of the light-front approach, where the deuteron is regarded as a weekly bound state of a proton and a neutron. Both the S− and D−wave interacting vertexes among deuteron, proton, and neutron are taken into account. Moreover, the regularization functions are also introduced. In our calculations, the vertex and the regularization functions are employed to simulate the momentum distribution inside the deuteron. Our numerical results show that the light-front approach can roughly reproduce the deuteron electromagnetic form factors, like charge G0, magnetic G1, and quadrupole G2, in the low Q2 region. The important role of the D−wave vertex on G2 is also addressed.
分类: 物理学 >> 核物理学 提交时间: 2016-09-14
摘要: We report a measurement of differential cross section of π0 pair production in single-tag two-photon collisions. These results are obtained with 759fb−1 of the data collected with the Belle detector at the KEKB asymmetric energy e+e−collider. The cross section is measured for Q2 up to 30 GeV2, where Q2 is the negative of the invariant mass squared of the tagged virtual photon, in the kinematic range 0.5 GeV < W < 2.1 GeV and |cosθ∗| < 1.0 for the total energy and pion scattering angle, respectively. The transition form factor of the f0(980) and that of the f2(1270)with the helicity-0,-1, and -2 components separately are measured for the first time and are compared with theoretical calculations.
分类: 物理学 >> 核物理学 提交时间: 2016-09-10
摘要: We extract the e+e−→π+π− cross section in the energy range between 600 and 900 MeV, exploiting the method of initial state radiation. A data set with an integrated luminosity of 2.93 fb−1 taken at a center-of-mass energy of 3.773 GeV with the BESIII detector at the BEPCII collider is used. The cross section is measured with a systematic uncertainty of 0.9%. We extract the pion form factor |Fπ|2 as well as the contribution of the measured cross section to the leading order hadronic vacuum polarization contribution to (g−2)μ. We find this value to be aππ,LOμ(600−900MeV)=(368.2±2.5stat±3.3sys)⋅10−10.