Spin mixing mechanism in amplitude analysis of pi(-)p->pi(-)pi(+)n and a
  new view of dark matter
  We present the first amplitude analysis of the CERN data on
pi(-)p->pi(-)pi(+)n on polarized target at 17.2 GeV/c for dipion masses
580-1080 MeV at low momentum transfer using spin mixing mechanism. The analysis
of the S- and P-wave subsystem determines a unique solution for the spin mixing
transversity amplitudes S_tau, L_tau, the corresponding S-matrix amplitudes
S^0_tau, L^0_tau and the rho^0(770)-f_0(980) spin mixing parameters. The spin
mixing mechanism allows to extract D-wave observables from the CERN data.
Analysis of the full D-wave subsystem for transversity tau=u reveals rho^0(770)
mixing in the amplitudes |D^U_u|^2 and |D^N_u|^2 and a violation of a cosine
condition by the amplitudes D^2U_u and D^2N_u. We determine spin mixing and
S-matrix helicity amplitudes from which we calculate pipi phase-shifts
delta^0_S and delta_P below KKbar threshold. The spin mixing and the violation
of the cosine condition arise from a non-standard pure dephasing interaction of
the produced final S-matrix state rho_f(S) with a quantum state rho(E) of a
quantum environment to produce the observed state rho_f(O). Our analysis
determines that the number of interacting degrees of freedom of the environment
is M=4. We identify the four eigenstates |e_k> that define the density matrix
rho(E) with the four neutrino mass eigenstates |m_k> with m_4 due to light
sterile neutrino. We call the quantum states rho(E) dark neutrinos and propose
to identify them with the particles of a distinct component of dark matter.
Dephasing interactions are not rare events but they require high statistics
experiments with polarized targets for their detection. Our amplitude analysis
illustrates this new kind of search for dark matter.
