C. X. Liu

D-sJ(+)(2632): An excellent candidate of tetraquarks

We analyze various possible interpretations of the narrow state D{sub sJ}(2632) which lies 100 MeV above threshold. This interesting state decays mainly into D{sub s}{eta} instead of D{sup 0}K{sup +}. If this relative branching ratio is further confirmed by other experimental groups, we point out that the identification of D{sub sJ}(2632) either as a cs state or more generally as a 3 state in the SU(3){sub F} representation is probably problematic. Instead, such an anomalous decay pattern strongly indicates D{sub sJ}(2632) is a four-quark state in the SU(3){sub F} 15 representation with the quark content (1/2{radical}(2))(dsd+sdd+suu+usu-2sss)c. We discuss its partners in the same multiplet and the similar four-quark states composed of a bottom quark B{sub sJ}{sup 0}(5832). Experimental searches of other members especially those exotic ones are strongly called for.

Measurements of the Mass and Width of the eta(c) Using the Decay psi (3686) -> gamma eta(c)

The mass and width of the lowest-lying S-wave spin singlet charmonium state, the η(c), are measured using a data sample of 1.06×10(8) ψ(3686) decays collected with the BESIII detector at the BEPCII storage ring. We use a model that incorporates full interference between the signal reaction, ψ(3686)→γη(c), and a nonresonant radiative background to describe the line shape of the η(c) successfully. We measure the η(c) mass to be 2984.3±0.6±0.6 MeV/c(2) and the total width to be 32.0±1.2±1.0 MeV, where the first errors are statistical and the second are systematic.

Study on the separation of 100 TeV γ-rays from cosmic rays for the Tibet ASγ experiment

A γ/hadron separation analysis is described for the observed air shower events with primary energy above 100 TeV based on the Tibet ASγ detector configuration. The shower age and size parameters are fitted from the measured lateral density distribution and used as discrimination variables. According to the MC simulation while taking into account the systematic uncertainty estimated from data and MC comparison, it is found that 70% of the cosmic ray (CR) background can be rejected while more than 78% of the γ-rays can be retained. Sensitivity for 100 TeV γ-rays observation can thus be improved by at least 40%.