Peak Locations and Relative Phase of Different Decay Modes of the a_{1} Axial Vector Resonance in Diffractive Production.
We show that a single I=1 spin-parity J^{PC}=1^{++} a_{1} resonance can manifest itself as two separated mass peaks, one decaying into an S-wave ρπ system and the second decaying into a P-wave f_{0}(980)π system, with a rapid increase of the phase difference between their amplitudes arising mainly from the structure of the diffractive production process. This study clarifies questions related to the mass, width, and decay rates of the a_{1} resonance raised by the recent high statistics data of the COMPASS Collaboration on a_{1} production in πN→πππN at high energies.
Studies of light mesons at COMPASS
To investigate the spectrum of light mesons, the COMPASS experiment has recorded data with a 190 GeV/ c negative pion beam impinging on a liquid hydrogen target. Diffractive dissociation reactions at squared four-momentum transfers to the target between 0.1 and 1.0 (GeV/ c ) 2 are studied. The flagship channel is the π − π + π − final state, for which COMPASS has recorded the at present world’s largest data sample. A new axial-vector signal, the a 1 (1420), has been found with unusual properties, pointing to an exotic nature. The findings are confirmed by the analysis of the π − π 0 π 0 final state.
Thermal-mechanical fully coupled analysis of high-speed angular contact ball bearings
The thermal and mechanical properties of angular contact ball bearings are critical to their operating accuracy and service life. On the basis of the theory of dynamics and frictional heat generation, this work establishes a thermal-mechanical fully coupled model. The high-speed motion characteristics, temperature, and dynamic stiffness are analyzed, and the simulation results are compared with the theoretical calculation and experimental results. Then, the temperature and axial deformation of the bearings under different rotation speeds are analyzed, and the laws of mechanical and thermal characteristics of the bearings are obtained. Results show that an increase in the rotation speed of the inner ring causes the temperature of each component to increase, with the contact area of the balls showing the greatest increase in temperature. An increase in rotation speed also increases the axial deformation of the inner ring.