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Register a new userDark matter and Collider signals in supersymmetric $U(1)^prime$ models with non-universal $Z^prime$ couplings
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We analyse supersymmetric models augmented by an extra $U(1)$ gauge group. To avoid anomalies in these models without introducing exotics, we allow for family-dependent $U(1)^prime$ charges, and choose a simple form for these, dependent on one $U(1)^prime$ charge parameter only. With this choice, $Z^prime$ decays into di-taus but not di-leptons, weakening considerably the constraints on its mass. In the supersymmetric sector, the effect is to lower the singlino mass, allowing it to be the dark matter candidate. We investigate the dark matter constraints and collider implications of such models, with mostly singlino, or mostly higgsinos, or a mixture of the two as lightest supersymmetric particles. In these scenarios, $Z^prime$ decays significantly into chargino or neutralino pairs, and thus indirectly into final state leptons. We devise benchmarks which, with adequate cuts, can yield signals visible at the high-luminosity LHC.
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We analyze the prospects for light neutralino dark matter in the minimal supersymmetric model extended by a $U(1)$ gauge group. We allow the neutralino to be an arbitrary admixture of singlet and doublet higgsinos, as well as of the three gauginos, and we require agreement with the data from the direct and indirect dark matter detection experiments, while maintaining consistency of the model with the relic density and with the recent Higgs data from the LHC. The constraints have implications for the structure of the lightest neutralino as a dark matter candidate, indicating that it is largely singlino, and its mass can be as light as $sim 20 $ GeV.
We have studied phenomenological implications of several family non-universal U(1)$^prime$ sub-models in the U(1)$^prime$-extended Minimal Supersysmmetric Standard Model (UMSSM) possesing an extra down quark type exotic field. In doing this, we have started by enforcing anomaly cancellation criteria to generate a number of solutions in which the extra U(1)$^prime$ charges of the particles are treated as free parameters. We have then imposed existing bounds coming from colliders and astrophysical observations on the assumed sub-models and observed that current limits dictate certain charge orientations, for instance, $Q_{H_u}sim Q_{H_d}$ is preferred in general and the charge of the singlet $Q_S$ cannot be very small ($|Q_S|>$ 0.4) even if any of the charges is allowed to take any value within the $[-1, 1]$ range. We have finally studied the potential impact of such non-universal charges on $Z$ mediated processes and made predictions for existing and future experiments. It has turned out that UMSSMs with or without the presence of light exotic quarks can yield distinguisable signatures if non-universal charges are realised in the leptonic sector of such models.
We consider a class of gauged $U(1)$ extensions of the Standard Model (SM), where the light neutrino masses are generated by an inverse seesaw mechanism. In addition to the three right handed neutrinos, we add three singlet fermions and demand an extra $Z_2$ symmetry under which, the third generations of both of the neutral fermions are odd, which in turn gives us a stable dark matter candidate. We express the $U(1)$ charges of all the fermions in terms of the U(1) charges of the standard model Higgs and the new complex scalar. We study the bounds on the parameters of the model from vacuum stability, perturbative unitarity, dark matter relic density and direct detection constraints. We also obtain the collider constraints on the $Z$ mass and the $U(1)$ gauge coupling. Finally we compare all the bounds on the $Z$ mass versus the $U(1)$ gauge coupling plane.
We study a class of general U$(1)^prime$ models to explain the observed dark matter relic abundance and light neutrino masses. The model contains three right handed neutrinos and three gauge singlet Majorana fermions to generate the light neutrino mass via the inverse seesaw mechanism. We assign one pair of degenerate sterile neutrinos to be the dark matter candidate whose relic density is generated by the freeze-in mechanism. We consider different regimes of the masses of the dark matter particle and the ${Z^prime}$ gauge boson. The production of the dark matter can occur at different reheating temperatures in various scenarios depending on the masses of the ${Z^prime}$ boson and the dark matter candidate. We also note that if the mass of the sterile neutrino dark matter is $gtrsim 1 rm{MeV}$ and if the $Z^prime$ is heavier than the dark matter, the decay of the dark matter candidate into positrons can explain the long standing puzzle of the galactic $511rm{keV}$ line in the Milky Way center observed by the INTEGRAL satellite. We constrain the model parameters from the dark matter analysis, vacuum stability and the collider searches of heavy ${Z^prime}$ at the LHC. For the case with light $Z^prime$, we also compare how far the parameter space allowed from dark matter relic density can be probed by the future lifetime frontier experiments SHiP and FASERs in the special case of $U(1)_{B-L}$ model.
We study $Z$ phenomenology at hadron colliders in an $U(1)$ extended MSSM. We choose a $U(1)$ model with a secluded sector, where the tension between the electroweak scale and developing a large enough mass for $Z$ is resolved by incorporating three additional singlet superfields into the model. We perform a detailed analysis of the production, followed by decays, including into supersymmetric particles, of a $Z$ boson with mass between 4 and 5.2 TeV, with particular emphasis on its possible discovery. We select three different scenarios consistent with the latest available experimental data and relic density constraints, and concentrate on final signals with two leptons, four leptons and six leptons. Including the SM background from processes with two, three or four vector bosons, we show the likelihood of observing a $Z^prime$ boson is not promising for the HL-LHC at 14 TeV. While at 27 and 100 TeV, the situation is more optimistic, and we devise specific benchmark scenarios which could be observed.
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