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For searching beyond Standard Model physics, stars are laboratories whichcomplement terrestrial experiments. Massless neutrinos in the Standard Model ofparticle physics cannot have a magnetic moment, but massive neutrinos have afinite magnetic moment in the minimal extension of the Standard Model. Largeextra dimensions are a possible solution of the hierarchy problem. Both ofthese provide additional energy loss channels in stellar interiors via theelectromagnetic interaction and radiation into extra dimensions, respectively,and thus affect stellar evolution. We perform simulations of stellar evolutionwith such additional energy losses and find that they eliminate the blue loopsin the evolution of intermediate-mass stars. The existence of Cepheid stars canbe used to constrain the neutrino magnetic moment and large extra dimensions.In order for Cepheids to exist, the neutrino magnetic moment should be smallerthan 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 5TeV, depending on the rate of the ^{12}C(alpha, gamma)^{16}O reaction. Thefundamental scale also has strong dependence on the metallicity. This value ofthe magnetic moment is in the range explored in the reactor experiments, buthigher than the limit inferred from globular clusters. Similarly thefundamental scale value we constrain corresponds to a size of the compactifieddimensions comparable to those explored in the torsion balance experiments, butis smaller than the limits inferred from collider experiments and low-massstars.

Elimination of the Blue Loops in the Evolution of Intermediate-mass Stars by the Neutrino Magnetic Moment and Large Extra Dimensions