DIRECT TEST OF THE COMPOSITE-FERMION MODEL IN QUANTUM HALL SYSTEMS

We show that neutron-scattering experiments can unambiguously determin e a composite-fermion parameter, viz., the effective number of Landau levels p filled by the composite fermions. We also show that Raman sca ttering experiments can directly measure the effective cyclotron frequ ency <(omega)over bar>(c) of composite fermions and p will also be det ermined thereby if the effective mass of the composite fermion is give n. For this purpose, one needs partially polarized or more preferably unpolarized quantum Hall states. We further find that the value of the static spin correlation function undergoes a jump in the spin transit ions. We identify the effective number of Landau levels filled by comp osite fermions of up (or down) spin to be the order parameter in the s pin transitions.