Search

By using two-dimensional particle-in-cell simulations, we demonstrate high-flux dense positrons generation by irradiating an ultra-intense laser pulse onto a tapered hollow target. By using a laser with an intensity of 4 ×1023W/cm², it is shown that the Breit-Wheeler process dominates the positron production during the laser-target interaction and a positron beam with a total number >1015 is obtained, which is increased by five orders of magnitude than in the previous work at the same laser intensity. Due to the focusing effect of the transverse electric fields formed in the hollow cone wall, the divergence angle of the positron beam effectively decreases to ~15° with an effective temperature of ~674 MeV. When the laser intensity is doubled, both the positron flux (>1016) and temperature (963 MeV) increase, while the divergence angle gets smaller (~13°). The obtained high-flux low-divergence positron beam may have diverse applications in science, medicine, and engineering. [ABSTRACT FROM AUTHOR]

Considering two assumptions on the molecular state, i.e. the S-wave Λ̄–K- and S-wave Σ̄0–K- molecular states, we study the possible decays of N̄X(1625) that include N̄X(1625)→K-Λ̄,π0p̄,ηp̄,π-n̄. Our results indicate that (1) if N̄X(1625) is the Λ̄–K- molecular state, K-Λ̄ is the main decay mode of N̄X(1625), and the branching ratios of the rest decay modes are tiny; (2) if N̄X(1625) is the Σ̄0–K- molecular state, the branching ratio of N̄X(1625)→K-Λ̄ is one or two orders smaller than that of N̄X(1625)→π0p̄,ηp̄,π-n̄. Thus the search for N̄X(1625)→π0p̄,ηp̄,π-n̄ will be helpful to shed light on the nature of N̄X(1625). [ABSTRACT FROM AUTHOR]

Recently the Babar Collaboration reported a new cs̄ state, DsJ(2860), and the Belle Collaboration observed DsJ(2715). We investigate the strong decays of the excited cs̄ states using the 3 P 0 model. After comparing the theoretical decay widths and decay patterns with the available experimental data, we are inclined to conclude that: (1) DsJ(2715) is probably the 1-(13 D 1) cs̄ state, although the 1-(23 S 1) assignment is not completely excluded; (2) DsJ(2860) seems unlikely to be the 1-(23 S 1) and 1-(13 D 1) candidate; (3) to consider DsJ(2860) either as a 0+(23 P 0) or as a 3-(13 D 3) cs̄ state is consistent with the experimental data; (4) the experimental search of DsJ(2860) in the channels Dsη, DK*, D*K and Ds *η will be crucial to distinguish the above two possibilities. [ABSTRACT FROM AUTHOR]

The article informs that the an electro-chemical reaction is made up of a series of chemical and physical steps occurring at very small length scales. The transfer of an electron between the electrode surface and a redox molecule takes place over a distance no greater that 2 nm and occurs in an interfacial region defined by the radius of adsorbed ions and solvent molecules, as welt as the distance that surface electric fields extend into the solution. In the late 1970s, analytical chemists first considered the role of electrode size in relation to electrochemical length scales. Electrodes of nanometer dimensions are also employed in in-situ electrochemical scanned probe microscopies, although their electrochemical behavior is not always of primary interest in these applications.

The elliptic flow v2, for , , p andin Au+Au collisions at center-of-mass energies , 11.5, 14.5 and 19.6 GeV, is analyzed using a multiphase transport model. A significant difference in the v2values for p andis observed, and the values of v2splitting are larger compared withand , and . The difference increases with decreasing the center-of-mass energy. The effect of the quark coalescence mechanism in a multi-phase transport model to the value of elliptic differencebetween p andhas been discussed. The simulation of Au+Au collisions at 14.5 GeV shows that the effect of hadron cascade tois not obvious, and a larger parton-scattering cross section can lead to a larger . [ABSTRACT FROM AUTHOR]