Searching For Axion-like Particles At Future Ep Colliders

In order to explain problems that the standard model can not explain,such as dark matter and strong CP problem,many new physics models beyond the standard model are proposed.In general,any physics model with global Abelian symmetry,which is spontaneously broken,predicts the existence of axion-like particles.Axion-like particles are pseudoscalar particles.It is gauge singlet under the standard model gauge group and is odd under CP.Using dimension-5 operators describes the interactions between axion-like particles and other particles.They cou-ple to Higgs boson or neutrino via higher dimension operators or loop level.The phenomeno-logical theory and the experimental constraint on these couplings have been widely studied.Future ep colliders like the LHeC or the FCC-eh can provide bigger center-of-mass energy and higher luminosity,while maintaining a clean environment with very little pile-up.There-fore,they can significantly expand the parameter space for detecting axion-like particles.We consider the possibility of searching for axion-like particle by the process e-p→e-a→e-γγat the LHeC and FCC-eh in a model-independent approach.The calculation results show that the effective ALP-photon coupling gaγγ range via searching for the diphoton signal at the LHeC and FCC-eh can be obviously exceeded the constraints of existing experiments when the mass interval is 10-100 GeV.Furthermore,the FCC-eh will improve the search limit up to 3 TeV and be sensitive to axion-like particle in a large range of the parameter space.Comparing to existing bounds on the axion-like particle parameters space,we find that the bounds given by ep colliders are competitive and complementary to other colliders.