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  • Chromomagnetic and chromoelectric dipole moments of quarks in the reduced 331 model
    Published: 2021-09-14, doi: 10.1088/1674-1137/ac1b9a
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    The one-loop contributions to the chromomagnetic dipole moment $\hat\mu_t(q^2)$ and electric dipole moment $\hat d_t(q^2)$ of the top quark are calculated within the reduced 331 model (RM331) for non-zero $q^2$. It is argued that the results are gauge independent and thus represent valid observable quantities. In the RM331, $\hat \mu_t(q^2)$ receives new contributions from two heavy gauge bosons, namely $Z'$ and $V^\pm$, and one neutral scalar boson $h_2$, along with a new contribution from the standard model's Higgs boson via flavor changing neutral currents. The latter, which is also mediated by the $Z'$ gauge boson and the scalar boson $h_2$, can provide a non-vanishing $\hat d_t(q^2)$ if there is a $CP$-violating phase. The analytical results are presented in terms of both Feynman parameter integrals and Passarino-Veltman scalar functions, which are useful to cross-check the numerical results. Both $\hat\mu_t(q^2)$ and $\hat d_t(q^2)$ are numerically evaluated for parameter values still allowed by the constraints from experimental data. It is found that the new one-loop contributions of the RM331 to the real (imaginary) part of $\hat \mu_t(q^2)$ are of the order of $10^{-5}$ ($10^{-6}$), which means at least three orders of magnitude smaller than the standard model prediction but larger than the predictions of other models of new physics. In the RM331, the dominant contribution arises from the $V^\pm$ gauge boson for $\|q\|$ in the 30-1000 GeV interval and a mass $m_{V}$ of the order of a few hundreds of GeV. As for $\hat d_t(q^2)$, it receives its largest contribution from $h_2$ exchange and can reach values of the order of $10^{-19}$, i.e., smaller than the contributions predicted by other standard model extensions.
  • Cosmological implications of a BL charged hidden scalar: leptogenesis and gravitational waves
    Published: 2021-09-14, doi: 10.1088/1674-1137/ac1e09
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    In this study, we investigated the cosmological implications of a complex singlet scalar $ {\cal{S}}$ with non-trivial $ B-L$ charges in the conformal $ U(1)_{B-L}$ theory. It was found that, in a sizable region of parameter space, $ {\cal{S}}$ may disturb the resonant leptogenesis mechanism, which is used to generate baryon asymmetry, and affect the symmetry breaking dynamics in the strong first order phase transition. The stochastic gravitational waves (GWs) produced at the phase transition can be probed in future GW experiments. The GW searches prefer a relatively light $ {\cal{S}}$ at the TeV-scale; however, this is difficult to detect directly at future high-energy colliders.
  • Description of elastic scattering induced by the unstable nuclei 9,10,11,13,14C
    Published: 2021-09-14, doi: 10.1088/1674-1137/ac1fe1
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    The elastic-scattering angular distributions and total reaction cross sections of $^{9,10,11,13,14}{\rm{C}}$ projectiles were predicted using the obtained $^{12}{\rm{C}}$ and $^{9}{\rm{Be}}$ global optical model potentials, respectively. The predictions were analyzed in detail by comparison with the available experimental data. The results indicate that the $^{12}{\rm{C}}$ and $^{9}{\rm{Be}}$ global optical model potentials provide a satisfactory description of the elastic scattering data for the reactions induced by the $^{9,10,11,13}{\rm{C}}$. For the neutron-rich carbon isotope $^{14}{\rm{C}}$, the elastic scattering can be well described by changing the real part radius parameter of the $^{12}{\rm{C}}$ global optical model potential. Possible physical explanations for the observed differences are further discussed.