Principles and Applications of Muon Cooling

E l e c t r o n p o s i t r o n (e§ ) c o l i i d e r s have been es s e n t i a l t o o l s in ga in ing an unders tanding of p a r t i c l e physics. However, their future use at higher energies i s s e v e r e l y l i m i t e d by r a d i a t i o n processes . Synchrot ron r a d i a t i o n in s torage r i n g s causes e l e c t r o n s to lose energy a t a r a te p r o p o r t i o n a l to the fou r th power of the e l e c t r o n energy, and this radiation effectively + preven t s c o n s t r u c t i o n of es torage r i ngs a t ene rg ie s g r e a t e r than lO0 GeV (LEP). e+-e l i n e a r c o l l i d e r s are proposed to circumvent this problem. However, they have s u b s t a n t i a l p r a c t i c a l d i f f i c u l t i e s in o b t a i n i n g adequate l uminos i t y , are very expens ive , and a l s o have p a r t i c l e r a d i a t i o n problems tha t prevent p r a c t i c a l implementa t ion a t p a r t i c l e ene rg ie s ~300 GeV. Another approach, ~p and pp c o l l i d e r s , can indeed reach m u l t i TeV e n e r g i e s , but hadron-hadron i n t e r a c t i o n s lack the s i m p l i c i t y of l e p t o n l e p t o n c o l l i s i o n s ; l e p t o n l e p t o n and lep ton-hadron c o l l i d e r s are necessary to provide a complete p i c t u r e of h igh-energy processes .