Identifying the structure of near-threshold states from the line shape  

作　　者：陈国英 霍文生 赵强 

机构地区：[1]Department of Physics, Xinjiang University [2]State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics,Chinese Academy of Sciences [3]Institute of High Energy Physics, Chinese Academy of Sciences [4]Theoretical Physics Center for Science Facilities, Chinese Academy of Sciences

出　　处：《Chinese Physics C》2015年第9期8-16,共9页中国物理C（英文版）

基　　金：Supported by National Natural Science Foundation of China (11147022, 11035006, 11305137);Chinese Academy of Sciences (KJCX2EW-N01);Ministry of Science and Technology of China (2009CB825200);DFG and NSFC (11261130311) through funds provided to the Sino-German CRC 110 "Symmetries and the Emergence of Structure in QCD";Doctor Foundation of Xinjiang University (BS110104)

摘　　要：We revisit the compositeness theorem proposed by Weinberg in an effective field theory （EFT） and explore criteria which are sensitive to the structure of S-wave threshold states. On a general basis, we show that the wave function renormalization constant Z, which is the probability of finding an elementary component in the wave function of a threshold state, can be explicitly introduced in the description of the threshold state. As an application of this EFT method, we describe the near-threshold line shape of the D＊0D0 invariant mass spectrum in B→D＊0D-0K and determine a nonvanishing value of Z. It suggests that the X（3872） as a candidate of the D＊0D0 molecule may still contain a small cc core. This elementary component, on the one hand, explains its production in the B meson decay via a short-distance mechanism, and on the other hand, is correlated with the D＊0D0 threshold enhancement observed in the D＊0D0 invariant mass distributions. Meanwhile, we also show that if Z is non-zero, the near-threshold enhancement of the D＊0D0 mass spectrum in the B decay will be driven by the short-distance production mechanism.We revisit the compositeness theorem proposed by Weinberg in an effective field theory （EFT） and explore criteria which are sensitive to the structure of S-wave threshold states. On a general basis, we show that the wave function renormalization constant Z, which is the probability of finding an elementary component in the wave function of a threshold state, can be explicitly introduced in the description of the threshold state. As an application of this EFT method, we describe the near-threshold line shape of the D＊0D0 invariant mass spectrum in B→D＊0D-0K and determine a nonvanishing value of Z. It suggests that the X（3872） as a candidate of the D＊0D0 molecule may still contain a small cc core. This elementary component, on the one hand, explains its production in the B meson decay via a short-distance mechanism, and on the other hand, is correlated with the D＊0D0 threshold enhancement observed in the D＊0D0 invariant mass distributions. Meanwhile, we also show that if Z is non-zero, the near-threshold enhancement of the D＊0D0 mass spectrum in the B decay will be driven by the short-distance production mechanism.

关 键 词：X（3872） effective field theory COMPOSITENESS 

分 类 号：O572.33[理学—粒子物理与原子核物理] TU311.2[理学—物理]