  For searching beyond Standard Model physics, stars are laboratories which
complement terrestrial experiments. Massless neutrinos in the Standard Model of
particle physics cannot have a magnetic moment, but massive neutrinos have a
finite magnetic moment in the minimal extension of the Standard Model. Large
extra dimensions are a possible solution of the hierarchy problem. Both of
these provide additional energy loss channels in stellar interiors via the
electromagnetic interaction and radiation into extra dimensions, respectively,
and thus affect stellar evolution. We perform simulations of stellar evolution
with such additional energy losses and find that they eliminate the blue loops
in the evolution of intermediate-mass stars. The existence of Cepheid stars can
be used to constrain the neutrino magnetic moment and large extra dimensions.
In order for Cepheids to exist, the neutrino magnetic moment should be smaller
than the range ~2x10^{-10} to 4x10^{-11}mu_B, where mu_B is the Bohr magneton,
and the fundamental scale in the (4+2)-spacetime should be larger than ~2 to 5
TeV, depending on the rate of the ^{12}C(alpha, gamma)^{16}O reaction. The
fundamental scale also has strong dependence on the metallicity. This value of
the magnetic moment is in the range explored in the reactor experiments, but
higher than the limit inferred from globular clusters. Similarly the
fundamental scale value we constrain corresponds to a size of the compactified
dimensions comparable to those explored in the torsion balance experiments, but
is smaller than the limits inferred from collider experiments and low-mass
stars.
