Calculation of francium hyperfine anomaly

The Dirac-Hartree-Fock plus many-body perturbation theory (DHF+MBPT) method has been used to calculate hyperfine structure constants for Fr. Calculated hyperfine structure anomaly for hydrogen-like ion has been shown to be in good agreement with analytical expressions. It has been shown that the ratio of the anomalies for $s$ and $p_{1/2}$ states is weakly dependent on the principal quantum number. Finally, we estimate Bohr--Weisskopf corrections for several Fr isotopes. Our results may be used to improve experimental accuracy for the nuclear $g$ factors of short-lived isotopes.Comment: 5 pages, 3 tables, 2 figures. arXiv admin note: text overlap with arXiv:1703.1004

Sgoldstino signature in hhhh, W+W−W^+W^- and ZZZZ spectra at the LHC

In a supersymmetric extension of the Standard Model of particle physics (SM) with low scale of supersymmetry breaking, sgoldstino of (sub)TeV mass can be observed at the Large Hadron Collider (LHC) as a peak in diboson mass spectra. Moreover, as a singlet with respect to the SM gauge group, scalar sgoldstino can mix with the SM-like Higgs boson and interfere in all neutral channels providing with the promising signatures of new physics if superpartners are heavy. Sgoldstino couplings to the SM particles are determined by the pattern of soft supersymmetry breaking parameters. Here we concentrate on the cases with a noticeable sgoldstino contribution to di-Higgs channel. Having found a phenomenologically viable region in the model parameter space where scalar sgoldstino, produced at the LHC in gluon fusion, decays into a pair of the lightest Higgs boson we give predictions for corresponding cross section. Using the results of the LHC searches for scalar resonances we place bounds on the supersymmetry breaking scale $\sqrt{F}$ in this region of parameter space. Remarkably, in this region sgoldstino may also be observed in $W^+W^-$ and $ZZ$ channels, yielding independent signatures, since their signal strengths are related to that of di-Higgs channel.Comment: 25 pages, 10 figure

Gravitational waves from first-order electroweak phase transition in a model with light sgoldstinos

We study previously unexplored possibility of triggering the first order electroweak phase transition (EWPT) by interactions of the Standard Model (SM) particles with the sector responsible for low scale supersymmetry breaking. The low-energy theory apart from the SM particles contains additional scalar degrees of freedom -- sgoldstinos -- which contribute to the effective scalar potential and thus can trigger the first order EWPT. Remarkably, the latter requires only moderate couplings in the scalar sector. The perturbative description in terms of the effective theory seems formally to be applicable upto the scale of supersymmetry breaking: the Landau pole in the scalar sector is above $10^8$-$10^9$ GeV. We calculate the gravitational wave signal generated at this transition (it can be tested, e.g. by LISA, BBO and DECIGO) and briefly discuss the collider phenomenology of this scenario.Comment: 30 pages, 5 figures, 3 tables; the estimate of uncertainties in GW spectra added, figures and tables updated; published versio