Decaying light particles in the SHiP experiment. III. Signal rate estimates for scalar and pseudoscalar sgoldstinos

For supersymmetric extensions of the Standard Model with light sgoldstinos - scalar and pseudoscalar superparthners of goldstino - we estimate the signal rate anticipated at the lately proposed fixed target experiment SHiP utilizing CERN SPS beam of 400 GeV protons. We also place new limits on the model parameters from the similar analysis of the published results of CHARM experiment.Comment: 11 pages, 12 figure

Stoponium Search at Photon Linear Collider

In some supersymmetric extensions of the Standard Model fairly light superpartner of t-quark is predicted, which may form bound states ({\it stoponiums}) under certain conditions. We study prospects of search for stoponium at the future Photon Linear Collider. It is found that this machine could be the best machine for discovery and study of these resonances at some scenarios of supersymmetric extension of the Standard Model. In particular, if the $hh$ decay channel is dominant stoponium could be observed at the beginning of PLC run with collision energy tuned at the stoponium mass. If this channel is kinematically closed stoponium could be discovered in $gg$, $\gamma\gamma$ and $ZZ$ decay channels but higher statistics are needed. Effects of the stoponium-Higgs mixing and degeneracy are briefly discussed.Comment: 11 pages, 2 figures added, corrections taken into account result in increasing of signal significanc

Induced resonance makes light sterile neutrino Dark Matter cool

We describe two new generation mechanisms for Dark Matter composed of sterile neutrinos with ${\cal O}(1)$ keV mass. The model contains a light scalar field which coherently oscillates in the early Universe and modulates the Majorana mass of the sterile neutrino. In a region of model parameter space, the oscillations between active and sterile neutrinos are resonantly enhanced. This mechanism allows us to produce sterile neutrino DM with small mixing angle with active neutrinos, thus evading the X-ray constraints. At the same time the spectrum of produced DM is much cooler, than in the case of ordinary oscillations in plasma, opening a window of lower mass DM, which is otherwise forbidden by structure formation considerations. In other regions of the model parameter space, where the resonance does not appear, another mechanism can operate: large field suppresses the active-sterile oscillations, but instead sterile neutrinos are produced by the oscillating scalar field when the effective fermion mass crosses zero. In this case DM component is cold, and even 1 keV neutrino is consistent with the cosmic structure formation.Comment: 6 pages, 4 figures, PRD accepted versio

Kaon Physics with Light Sgoldstinos and Parity Conservation

Superpartners of goldstino -- scalar and pseudoscalar sgoldstinos -- interact weakly with ordinary particles. One or both of them may be light. We consider a class of supersymmetric extensions of the Standard Model in which interactions of sgoldstinos with quarks and gluons conserve parity but do not conserve quark flavor. If the pseudoscalar sgoldstino $P$ is light, m_P<(m_K-2m_\pi), and the scalar sgoldstino is heavier, m_S>(m_K-m_\pi), an interesting place for experimental searches is the poorly explored area of three-body decays of kaons, K^0_{S,L}\to\pi^+\pi^- P, K^0_{S,L}\to\pi^0\pi^0 P and K^+\to\pi^+\pi^0 P, with $P$ subsequently decaying into \gamma\gamma, possibly e^+e^-, or flying away from the detector. We evaluate the constraints on the flavor-violating coupling of sgoldstino to quarks which are imposed by K^0_L-K^0_S mass difference and CP-violation in neutral kaon system, and find that these constraints allow for fairly large Br(K\to\pi\pi P). We find that the most interesting ranges of branching ratios start at Br(K^0_L\to\pi\pi P)\sim 10^{-3}, Br(K^+\to\pi^+\pi^0 P)\sim 10^{-4}, Br(K_S^0\to\pi\pi P)\sim 10^{-3}. These searches for light pseudoscalar sgoldstino would be sensitive to the supersymmetry breaking scale \sqrt{F} in the 100 TeV range and above. We also briefly discuss the cases of light scalar sgoldstino and relatively heavy sgoldstinos.Comment: 14 pages, 3 figures. References added. Journal versio