We investigate a scenario inspired by natural supersymmetry, where neutrino data is explained within a low-scale seesaw scenario. For this the Minimal Supersymmetric Standard Model is extended by adding light right-handed neutrinos and their superpartners, the R-sneutrinos. Moreover, we consider the lightest neutralinos to be Higgsino-like. We first update a previous analysis and assess to which extent does existing LHC data constrain the allowed slepton masses. Here we find scenarios where sleptons with masses as low as 175 GeV are consistent with existing data. However, we also show that the upcoming run will either discover or rule out sleptons with masses of 300 GeV, even for these challenging scenarios.
We then take a scenario which is on the borderline of observability of the upcoming LHC run assuming a luminosity of 300 fb$^{-1}$. We demonstrate that a prospective international $e^+ e^-$ linear collider with a center of mass energy of 1 TeV will be able to discover sleptons in scenarios which are difficult for the LHC. Moreover, we also show that a measurement of the spectrum will be possible within 1-3 percent accuracy.
The advent of the LHC, and the proposal of building future colliders as the ILC, both programmed to explore new physics at the TeV scale, justifies the recent interest in studying all kind of seesaw mechanisms whose signature lies on such energy scale. The natural candidate for this kind of seesaw mechanism is the inverse one. The conventional inverse seesaw mechanism is implemented in an arrangement involving six new heavy neutrinos in addition to the three standard ones. In this paper we develop the inverse seesaw mechanism based on Higgs triplet model and probe its signature at the LHC and …
Two important features of TeV-scale radiative seesaw models, in which tiny neutrino masses are generated at the quantum level, are an extended scalar (Higgs) sector and the Majorana nature. We study phenomenological aspects of these models at the ILC. It is found that the Majorana nature of the models can be tested directly via the electron-positron and electron-electron collision experiments.
We review the computation of the one-loop radiative corrections from the neutrino/ sneutrino sector to the lightest Higgs boson mass, Mh, within the context of the so-called MSSM-seesaw scenario. This model introduces right handed neutrinos and their supersymmetric partners, the sneutrinos, including Majorana mass terms. We find negative and sizeable corrections to Mh, up to -5 GeV for a large Majorana scale, 10^{13}-10^{15} GeV, and for the lightest neutrino mass in a range 0.1-1 eV. The corrections to Mh are substantially larger than the anticipated ILC precision for large regions of the MSS…
A collider probe of the radiative seesaw models are considered. Two key ingredients of these models, the extended Higgs sector and the source of the Majorana mass, although these details differ model by model, would be studied at the TeV-scale electron-positron and electron-electron colliders. The searches and mass determinations in the inert doublet model, which is the extended Higgs sector of the Ma model, are summarized as an example.
We investigate a scenario inspired by natural supersymmetry, where neutrino data is explained within a low-scale seesaw scenario. For this the Minimal Supersymmetric Standard Model is extended by adding light right-handed neutrinos and their superpartners, the R-sneutrinos. Moreover, we consider the lightest electroweakinos to be higgsino-like. We demonstrate that a prospective international $e^+ e^-$ linear collider with a center of mass energy of 1 TeV will be able to discover sleptons in scenarios which can be difficult for current colliders. Moreover, we also show that a measurement of the…
We discuss phenomenology in a new TeV scale model which would explain neutrino oscillation, dark matter, and baryon asymmetry of the Universe simultaneously by the dynamics of the extended Higgs sector and TeV-scale right-handed neutrinos. Tiny neutrino masses are generated at the three-loop level due to the exact $Z_2$ symmetry, by which the stability of the dark matter candidate is guaranteed. The model provides various discriminative predictions in Higgs phenomenology, which can be tested at the Large Hadron Collider and the International Linear Collider.
Supersymmetric mass spectra within two variants of the seesaw mechanism, commonly known as type-II and type-III seesaw, are calculated using full 2-loop RGEs and minimal Supergravity boundary conditions. The type-II seesaw is realized using one pair of 15 and $\bar{15}$ superfields, while the type-III is realized using three copies of $24_M$ superfields. Using published, estimated errors on SUSY mass observables attainable at the LHC and in a combined LHC+ILC analysis, we calculate expected errors for the parameters of the models, most notably the seesaw scale. If SUSY particles are within the…
We consider the production of a single Standard Model (SM) Higgs boson ($h^0$) in association with a photon at the future Linear collider (LC) in the context of a type-II seesaw model. The type-II seesaw model extends the SM particle content by adding one triple Higgs where its Higgs coupling is a key parameter of the scalar potential triggering the electroweak symmetry-breaking mechanism in the SM. It is a well motivated model since it provides neutrino masses and mixing. The LC presents a particularly interesting possibility to probe Higgs couplings due to the clean beams in the initial stat…
The Higgs inflation scenario is an approach to realize the cosmic inflation, where the Higgs boson plays a role of the inflaton. In the minimal model, it would be difficult to satisfy theoretical constraints from vacuum stability and perturbative unitarity. These problems can be solved by considering multi-Higgs models. In this talk, we discuss a Higgs inflation scenario in a radiative seesaw model with an inert doublet, which originally has been proposed to explain dark matter and neutrino masses. We study this model under the constraints from the current data, and find parameter regions wher…
We study the collider signature of pseudo-Dirac heavy neutrinos in the inverse seesaw scenario, where the heavy neutrinos with mass at the electroweak scale can have sizable mixings with the Standard Model neutrinos, while providing the tiny light neutrino masses by the inverse seesaw mechanism. Based on a simple, concrete model realizing the inverse seesaw, we fix the model parameters so as to reproduce the neutrino oscillation data and to satisfy other experimental constraints, assuming two typical flavor structures of the model and the different types of hierarchical light neutrino mass spe…
We calculate supersymmetric mass spectra with cMSSM boundary conditions and a type-I seesaw mechanism added to explain current neutrino data. Using published, estimated errors on SUSY mass observables for a combined LHC+ILC analysis, we perform a theoretical $χ^2$ analysis to identify parameter regions where pure cMSSM and cMSSM plus seesaw type-I might be distinguishable with LHC+ILC data. The most important observables are determined to be the (left) smuon and selectron masses and the splitting between them, respectively. Splitting in the (left) smuon and selectrons is tiny in most of cMSSM …
We consider a gauged U(1)$_{B-L}$ (Baryon-minus-Lepton number) extension of the Standard Model (SM), which is anomaly-free in the presence of three Right-Handed Neutrinos (RHNs). Associated with the U(1)$_{B-L}$ symmetry breaking the RHNs acquire their Majorana masses and then play the crucial role to generate the neutrino mass matrix by the seesaw mechanism. Towards the experimental confirmation of the seesaw mechanism, we investigate a RHN pair production through the U(1)$_{B-L}$ gauge boson ($Z^\prime$) at the 250 GeV International Linear Collider (ILC). The $Z^\prime$ gauge boson has been …
The signature of heavy fermionic triplets belonging to Type III seesaw at the International Linear Collider (ILC) is probed. Presence of charged fermionic triplets upto a mass of about $ 750$ GeV could be established through single production at a 1 TeV ILC with moderate luminosity of 300 fb$^{-1}$, assuming a fermion triplet-electron mixing of about 0.05. Unlike the case of LHC, the production process is highly sensitive to the mixing, making the process interesting. The single production of neutral triplet is found to be somewhat harder, considering the large SM background present. Pair prod…
The measure of the triple Higgs coupling is one of the major goals of the high-luminosity run of the CERN Large Hadron Collider (HL-LHC) as well as the future colliders, either leptonic such as the International Linear Collider (ILC) or hadronic such as the 100 TeV Future Circular Collider in hadron-hadron mode (FCC-hh). We have recently proposed this observable as a test of neutrino mass generating mechanisms in a regime where heavy sterile neutrino masses are hard to be probed otherwise. We present in this article a study of the one-loop corrected triple Higgs coupling in the inverse seesaw …
We consider a gauged B$-$L (Baryon number minus Lepton number) extension of the Standard Model (SM), which is anomaly free in the presence of three SM singlet Right Handed Neutrinos (RHNs). Associated with the $U(1)_{\rm B-L}$ gauge symmetry breaking, the RHNs acquire Majorana masses and then with the electroweak symmetry breaking, tiny Majorana masses for the SM(-like) neutrinos are naturally generated by the seesaw mechanism. As a result of the seesaw mechanism, the heavy mass eigenstates which are mainly composed of the SM-singlet RHNs obtain suppressed electroweak interactions through smal…
We investigate the potential of the International Linear Collider (ILC) to probe the mechanisms of neutrino mass generation and leptogenesis within the minimal seesaw model. Our results can also be used as an estimate for the potential of a Compact Linear Collider (CLIC). We find that heavy sterile neutrinos that simultaneously explain both, the observed light neutrino oscillations and the baryon asymmetry of the universe, can be found in displaced vertex searches at ILC. We further study the precision at which the flavour-dependent active-sterile mixing angles can be measured. The measurement…
Neutrino masses could originate in seesaw models testable at colliders, with light mediators and an approximate lepton number symmetry. The minimal model of this type contains two quasi-degenerate Majorana fermions forming a pseudo-Dirac pair. An important question is to what extent future colliders will have sensitivity to the splitting between the Majorana components, since this quantity signals the breaking of lepton number and is connected to the light neutrino masses. We consider the production of these neutral heavy leptons at the ILC, where their displaced decays provide a golden signal…
We study the capability of the international linear collider (ILC) to probe extra dimensions via the seesaw mechanism. In the scenario we study, heavy Kaluza-Klein neutrinos generate tiny neutrino masses and, at the same time, have sizable couplings to the standard-model particles. Consequently, a Kaluza-Klein tower of heavy neutrinos (N) can be produced and studied at the ILC through the process: e+e- -> vN followed by N -> Wl decay. We show that the single lepton plus two-jets final states with large missing energy from this signal process will provide a good opportunity to measure the masse…
We explore the possibility of resolving simultaneously the $W$-boson mass shift reported by the CDF collaboration and the apparent deviation from unitarity in the first row of the CKM mixing matrix in a class of left-right symmetric models. The fermion masses are generated in these models through a universal seesaw mechanism, utilizing vector-like partners of the usual fermions. We find a unique solution to the two anomalies where the mixing of the down quark with a vector-like quark (VLQ) resolves the CKM unitarity puzzle, and the mixing of the top quark with a VLQ partner explains the $W$ bo…
The origin of neutrino mass is a big unsolved problem of the Standard Model (SM) that motivate us to consider beyond the SM (BSM) scenarios where SM-singlet right-handed neutrinos (RHNs) are introduced to explain the origin of the light neutrino masses through the seesaw mechanism. There is a variety of ways which could lead us to this goal and one of them is a general U$(1)$ extension of the SM. In this scenario, three SM-singlet RHNs are introduced to cancel the gauge and mixed gauge gravity anomalies. After anomaly cancellation, we notice that the left- and right-handed charged fermions are…
The Higgs Triplet Model (HTM) is one of important examples for extended Higgs sectors, because tiny neutrino masses can be simply explained. Unlike the canonical type-I seesaw model, a scale of new particles can be taken as $\mathcal{O}(100)$ GeV keeping an enough amount of production cross section for direct searches at collider experiments. In the HTM, there appear doubly-charged Higgs bosons $H^{\pm\pm}$, and detection of them is a key to probe the model. The decay property of $H^{\pm\pm}$ depends on the magnitude of the vacuum expectation value of the triplet field $v_Δ$. When $v_Δ$ is sma…
The PQ mechanism resolving the strong CP problem and the seesaw mechanism explaining the smallness of neutrino masses may be related in a way that the PQ symmetry breaking scale and the seesaw scale arise from a common origin. Depending on how the PQ symmetry and the seesaw mechanism are realized, one has different predictions on the color and electromagnetic anomalies which could be tested in the future axion dark matter search experiments. Motivated by this, we construct various PQ seesaw models which are minimally extended from the (non-) supersymmetric Standard Model and thus set up differ…
Self-interacting neutrinos that begin to free-stream at close to matter-radiation equality can reduce the physical size of photon sound horizon at last scattering surface. This mechanism can be the reason why standard $Λ$CDM cosmology sees a lower value of the Hubble constant than local measurements from distance ladder. We propose a new realization of self-interacting Dirac neutrinos (SID$ν$) with light-dark-photon mediator for a viable interaction mechanism. Our model is UV completed by a Dirac seesaw with anomaly-free dark $U(1)_X^{}$ gauge group which charges the right-handed neutrinos. Th…
The DAMPE $e^+ e^-$ excess at around 1.4 TeV could be explained in the type-II seesaw model with a scalar dark mater $D$ which is stabilized by a discrete $Z_2$ symmetry. The simplest scenario is the annihilation $DD \to H^{++} H^{--}$ followed by the subsequent decay $H^{\pm\pm} \to e^\pm e^\pm$, with both the DM and triplet scalars roughly 3 TeV with a small mass splitting. In addition to the Drell-Yan process at future 100 TeV hadron colliders, the doubly-charged components could also be produced at lepton colliders like ILC and CLIC in the off-shell mode, and mediate lepton flavor violatin…
Heavy neutrinos with masses below the electroweak scale can simultaneously generate the light neutrino masses via the seesaw mechanism and the baryon asymmetry of the universe via leptogenesis. The requirement to explain these phenomena imposes constraints on the mass spectrum of the heavy neutrinos, their flavour mixing pattern and their $CP$ properties. We first combine bounds from different experiments in the past to map the viable parameter regions in which the minimal low scale seesaw model can explain the observed neutrino oscillations, while being consistent with the negative results of…
In this work we show that, by introducing two $SU(3)_{c}\times SU(2)_{L}$ singlet right handed fermions carrying opposite $U(1)_{Y}$ charges and while their left handed counterparts are singlet under $SU(3)_{c}\times SU(2)_{L}$ and neutral under $U(1)_{Y}$, in the regime where the new charged lepton masses are in the electroweak scale it will be able to explain the small neutrino masses via minimum-inverse seesaw scenario (MISS) as well as the reported $R(K^{(*)})$ and muon $(g-2)$ discrepancies. Also when the charged fermion masses are well above the electro weak scale the model can not expla…
Heavy right handed neutrinos could not only explain the observed neutrino masses via the seesaw mechanism, but also generate the baryon asymmetry of the universe via leptogenesis due to their CP-violating interactions in the early universe. We review recent progress in the theoretical description of this nonequilibrium process. Improved calculations are particularly important for a comparison with experimental data in testable scenarios with Majorana masses below the TeV scale, in which the heavy neutrinos can be found at the LHC, in the NA62 experiment, at T2K or in future experiments, includ…
