Sgoldstinos: Primaries of Ultra-High Energy Cosmic Rays

I describe supersymmetric extensions of the Standard Model with light sgoldstinos and discuss the explanation of Ultra High Energy Cosmic Rays above GZK cutoff in these models. Also I briefly discuss the possibility to solve other cosmological and astrophysical puzzles, such as gamma-ray bursts and dimming of high-redshift supernovae, within the models with light sgoldstinos.Comment: 6 pages; Talk given at the XXXVIIth Rencontres de Moriond, Electroweak Interactions and Unified Theories, Les Arcs, March 9-16, 200

On Electroweak Baryogenesis in Gauge Mediated Models with Messenger-Matter Mixing

We consider feasibility of electroweak baryogenesis in gauge mediated supersymmetry breaking models with messenger-matter mixing. We present a class of models where electroweak baryogenesis produces sufficient amount of baryon asymmetry. The main features of these models are ({\it i}) large mixing between messengers and right stop and ({\it ii}) fairly narrow region of viable $\tan\beta$.Comment: 12 page

Light Sgoldstino: Precision Measurements versus Collider Searches

We study sensitivity of low-energy experiments to the scale of supersymmetry breaking $\sqrt{F}$ in models with light sgoldstinos --- superpartners of goldstino. The limits on $\sqrt{F}$ may be obtained from direct and indirect measurements of sgoldstino coupling to photons, leptons, mesons and nucleons. There are three sources of constraints: ($i$) astrophysics and cosmology; ($ii$) precision laboratory experiments at low energies; ($iii$) rare decays. We discuss only processes with real sgoldstinos. For sgoldstino lighter than a few MeV and superpartner masses of the order of electroweak scale, astrophysical and reactor bounds on $\sqrt{F}$ are significantly stronger than limits which may be reached at future colliders. In models with heavier sgoldstino (up to 5 GeV), constraints from flavor conserving decays of mesons are complementary to ones coming from collider experiments. The most sensitive probes of sgoldstinos are flavor violating processes, provided that flavor is violated in squark and/or slepton sector. It is shown that sgoldstino contributions into FCNC and lepton flavor violation are strong enough to probe the supersymmetry breaking scale up to $\sqrt{F}\sim10^7$ GeV, if off-diagonal entries in squark (slepton) mass matrices are close to the current limits in MSSM.Comment: 18 pages, 6 figures; v2:misprints corrected, four figures added; v3: journal versio

Small Second Acoustic Peak from Interacting Cold Dark Matter?

We consider a possibility to explain the observed suppression of the second acoustic peak in the anisotropy spectrum of the Cosmic Microwave Background (CMB) by interaction between a fraction of non-baryonic Cold Dark Matter (CDM) and normal baryonic matter. This scenario does not require any modifications in the standard Big Bang Nucleosynthesis (BBN). We estimate the required values of the cross-section-to-mass ratio for elastic scattering of CDM particles off baryons. In case of velocity-independent elastic scattering (in the velocity interval 10^{-5}--10^{-3}) we find that such particles do not contradict observational limits if they are heavier than \sim 10^5 GeV or lighter than \sim 0.5 GeV. Another candidate, which may appear in the models with infinite extra dimensions, is a quasistable charged particle decaying through tunneling into extra dimensions. Finally a millicharged particle with the electric charge ranging from \sim 10^{-4} to \sim 10^{-1} and with mass M\sim 0.1 GeV--1 TeV also may be responsible for the suppression of the second acoustic peak. As a byproduct we point out that CMB measurements set new limits on the allowed parameter space for the millicharged particles.Comment: 10 pages, 1 figur

On sgoldstino interpretation of the diphoton excess

We point out that the diphoton excess at about 750 GeV recently discovered by the LHC experiments can be explained within supersymmetric models with low scale supersymmetry breaking with sgoldstino as a natural candidate. We discuss phenomenological consequences of this scenario describing possible signatures to test this hypothesis.Comment: 9 pages, 4 figures, journal versio

Low tan⁡β\tan{\beta} in the extended Minimal Gauge Mediated Model

We consider the Minimal Gauge Mediated Model (MGMM) with either fundamental or antisymmetric messenger multiplets and study consequences of messenger-matter mixing. It is shown that constraints on relevant coupling constants and mixing parameters coming from the existing experimental limits on lepton flavor violation and FCNC processes allow a wide range of $\tan\beta$ in MGMM with mixing.Comment: Talk presented at the 10th International Seminar ``Quarks-98'', Suzdal, Russia, May 18-24; to appear in the Proceeding

Nucleon-decay-like signatures of Hylogenesis

We consider nucleon-decay-like signatures of the hylogenesis, a variant of the antibaryonic dark matter model. For the interaction between visible and dark matter sectors through the neutron portal, we calculate the rates of dark matter scatterings off neutron which mimic neutron-decay processes $n\to \nu\gamma$ and $n\to \nu e^+ e^-$ with richer kinematics. We obtain bounds on the model parameters from nonobservation of the neutron decays by applying the kinematical cuts adopted in the experimental analyses. The bounds are generally (much) weaker than those coming from the recently performed study of events with a single jet of high transverse momentum and missing energy observed at the LHC. Then we suggest several new nucleon-decay like processes with two mesons in the final state and estimate (accounting for the LHC constraints) the lower limits on the nucleon lifetime with respect to these channels. The obtained values appear to be promising for probing the antibaryonic dark matter at future underground experiments like HyperK and DUNE.Comment: 32 pages, 14 figures, journal versio

Constraining neutrino superluminality from searches for sterile neutrino decays

Superluminal neutrinos are expected to lose energy due to bremstrauhlung. It is dominated by e+e--pair production if kinematically allowed. The same signature was used in searches for 3-body decays of hypothetical heavy sterile neutrinos. From the absence of these processes in CERN PS191 and CHARM experiments we set upper limits on the neutrino velocity in the energy range from 0.2 GeV to 280 GeV. Our limits are well below the neutrino velocity favored by the recent OPERA results. For energy-independent neutrino velocity the limits obtained in this paper are stronger than those coming from ICARUS experiment and observations of Supernova SN1987a

Disentangling perturbative and power corrections in precision tau decay analysis

Hadronic tau decay precision data are analyzed with account of both perturbative and power corrections of high orders within QCD. It is found that contributions of high order power corrections are essential for extracting a numerical value for the strange quark mass from the data on Cabibbo suppressed tau decays. We show that with inclusion of new five-loop perturbative corrections in the analysis the convergence of perturbation theory remains acceptable only for few low order moments. We obtain m_s(M_\tau) =130\pm 27 MeV in agreement with previous estimates.Comment: 6 page

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