On the constituent counting rule for hard exclusive processes involving multi-quark states  

作　　者：郭奉坤 Ulf-G.Mei?ner 王伟 

机构地区：[1]State Key Laboratory of Theoretical Physics,Institute of Theoretical Physics,Chinese Academy of Sciences [2]Helmholtz-Institut fr Strahlen- und Kernphysik and Bethe Center for Theoretical Physics,Universitt Bonn [3]Institute for Advanced Simulation,Institut fr Kernphysik and Jlich Center for Hadron Physics,Forschungszentrum Jlich [4]INPAC,Shanghai Key Laboratory for Particle Physics and Cosmology,Department of Physics and Astronomy,Shanghai Jiao-Tong University

出　　处：《Chinese Physics C》2017年第5期91-96,共6页中国物理C（英文版）

基　　金：Supported in part by DFG and NSFC through funds provided to the Sino-German CRC 110“Symmetries and the Emergence of Structure in QCD”(NSFC Grant No.11261130311);Thousand Talents Plan for Young Professionals,Chinese Academy of Sciences(CAS)President’s International Fellowship Initiative(PIFI)(2015VMA076);National Natural Science Foundation of China(11575110,11655002);Natural Science Foundation of Shanghai(15DZ2272100,15ZR1423100);Open Project Program of State Key Laboratory of Theoretical Physics,Institute of Theoretical Physics,Chinese Academy of Sciences,China(Y5KF111CJ1);Key Laboratory for Particle Physics,Astrophysics and Cosmology,Ministry of Education

摘　　要：At high energy,the cross section at finite scattering angle of a hard exclusive process falls off as a power of the Manderstam variable s.If all involved quark-gluon compositions undergo hard momentum transfers,the fall-off scaling is determined by the underlying valence structures of the initial and final hadrons,known as the constituent counting rule.In spite of the complication due to helicity conservation,it has been argued that when applied to exclusive process with exotic multiquark states,the counting rule is a powerful way to determine the valence degrees of freedom inside hadron exotics.In this work,we demonstrate that for hadrons with hidden flavors,the naive application of the constituent counting rule is problematic,since it is not mandatory for all components to participate in hard scattering at the scale s1/2.We illustrate the problems in the viewpoint based on effective field theory.We clarify the misleading results that may be obtained from the constituent counting rule in exclusive processes with exotic candidates such as Z_c~±（cd/cu）,Z_b~±（bd/bdu）,X（3872）,etc.At high energy,the cross section at finite scattering angle of a hard exclusive process falls off as a power of the Manderstam variable s.If all involved quark-gluon compositions undergo hard momentum transfers,the fall-off scaling is determined by the underlying valence structures of the initial and final hadrons,known as the constituent counting rule.In spite of the complication due to helicity conservation,it has been argued that when applied to exclusive process with exotic multiquark states,the counting rule is a powerful way to determine the valence degrees of freedom inside hadron exotics.In this work,we demonstrate that for hadrons with hidden flavors,the naive application of the constituent counting rule is problematic,since it is not mandatory for all components to participate in hard scattering at the scale s1/2.We illustrate the problems in the viewpoint based on effective field theory.We clarify the misleading results that may be obtained from the constituent counting rule in exclusive processes with exotic candidates such as Z_c~±（cd/cu）,Z_b~±（bd/bdu）,X（3872）,etc.

关 键 词：quark exclusive constituent hadron meson exotic problematic clarify momentum valence 

分 类 号：O572.33[理学—粒子物理与原子核物理]