72 research outputs found
Vanishing of the CP asymmetry in leptogenesis due to form dominance
No full textWe emphasize that the vanishing of the CP asymmetry in leptogenesis, previously observed for models with tribimaximal mixing and family symmetry, may be traced to a property of the type I seesaw mechanism satisfied by such models known as form dominance, corresponding to the case of a diagonal Casas-Ibarra R-matrix. Form dominance leads to vanishing flavor-dependent CP asymmetries irrespective of whether one has tribimaximal mixing or a family symmetry. Successful leptogenesis requires violation of form dominance, but not necessarily violation of tribimaximal mixing. This may be achieved in models where the family symmetry responsible for tribimaximal mixing is implemented indirectly and a strong neutrino mass hierarchy is present with the form dominance broken only softly by the right-handed neutrino responsible for the lightest neutrino mass, as in constrained sequential dominance.<br/
Doubly-charged Higgs boson at a future electron-proton collider
No full textWe explore the discovery prospect of the doubly-charged component of an SU(2)L-triplet scalar at the future e−p collider FCC-eh, proposed to operate with an electron beam energy of 60 GeV and a proton beam energy of 50 TeV. We consider the associated production of the doubly-charged Higgs boson along with leptons and jet(s), and its subsequent prompt decay to same-sign lepton pair. This occurs for O(1) Yukawa coupling of the scalar triplet with charged leptons, which is expected for reasonably small vacuum expectation values of the neutral component of the triplet field that governs the neutrino mass generation in the type-II seesaw. We present our analysis for two different final states, 3l+≥1j and an inclusive ≥2l+≥1j channel. Considering its decay to electrons only, we find that the doubly-charged Higgs boson with a mass around a TeV could be observed at the 3σ confidence level with O(200) fb−1 of integrated luminosity, while masses up to 2 TeV could be probed within a few years of data accumulation. The signal proposed here becomes essentially background free, if it is triggered in the μμ mode and a 5σ discovery is achievable in this channel for a TeV-scale doubly-charged Higgs boson with an integrated luminosity as low as O(50) fb−1. We also highlight the sensitivity of FCC-eh to the Yukawa coupling responsible for the production of the doubly-charged Higgs boson as a function of its mass in both the ee and μμ channels
Right handed neutrinos, TeV scale BSM neutral Higgs boson, and FIMP dark matter in an EFT framework
No full textInternational audienceWe consider an effective field theory framework with three Standard Model (SM) gauge singlet right-handed neutrinos, and an additional SM gauge singlet scalar field. The framework successfully generates eV masses of light neutrinos via the seesaw mechanism, and accommodates a feebly interacting massive particle (FIMP) as a dark matter candidate. Two of the gauge singlet neutrinos participate in neutrino mass generation, while the third gauge singlet neutrino is a FIMP dark matter. We explore the correlation between the vev (vacuum expectation value) of the gauge singlet scalar field which translates as mass of the BSM Higgs, and the mass of dark matter, which arises due to the relic density constraint. We furthermore explore the constraints from the light neutrino masses in this setup. We chose the gauge singlet BSM Higgs in this framework in the TeV scale. We perform a detailed collider analysis to explore the discovery prospect of the TeV scale BSM Higgs through its difatjet signature, at a future pp collider which can operate with s=100 TeV c.m. energy
An experiential learning approach to entrepreneurship education: a British initiative
No full textNo abstract available
Effect of cancellation in neutrinoless double beta decay
No full textIn light of recent experimental results, we carefully analyze the effects of interference in neutrinoless double beta decay, when more than one mechanism is operative. If a complete cancellation is at work, the half-life of the corresponding isotope is infinite, and any constraint on it will automatically be satisfied. We analyze this possibility in detail assuming a cancellation in Xe-136, and find its implications on the half-life of other isotopes, such as Ge-76. For definiteness, we consider the role of light and heavy sterile neutrinos. In this case, the effective Majorana mass parameter can be redefined to take into account all contributions, and its value gets suppressed. Hence, larger values of neutrino masses are required for the same half-life. The canonical light neutrino contribution cannot saturate the present limits of half-lives or the positive claim of observation of neutrinoless double beta decay, once the stringent bounds from cosmology are taken into account. For the case of cancellation, where all the sterile neutrinos are heavy, the tension between the results from neutrinoless double beta decay and cosmology becomes more severe. We show that the inclusion of light sterile neutrinos in this setup can resolve this issue. Using the recent results from GERDA, we derive upper limits on the active-sterile mixing angles and compare them with the case of no cancellation. The required values of the mixing angles become larger, if a cancellation is at work. A direct test of destructive interference in Xe-136 is provided by the observation of this process in other isotopes, and we study in detail the correlation between their half-lives. Finally, we discuss the model realizations which can accommodate light and heavy sterile neutrinos and the cancellation. We show that sterile neutrinos of few hundred MeVor GeV mass range, coming from an Extended seesaw framework or a further extension, can satisfy the required cancellation
(Re)interpretation of the LHC results for new physics
No full textHeavy neutral lepton (HNL) states can exist at the electroweak scale and can be investigated through current and future collider experiments. The scenario, where other new physics interactions occur at scales much higher than the HNL scale, can be described using an effective field theory (EFT) framework known as NR-EFT. We focus on constraining the Wilson coefficients of NR-EFT operators, which primarily contribute to tri-lepton plus missing energy signals at the LHC. We scrutinise the implication of the cuts proposed in the HNL search by CMS for the scenario where HNL production at LHC is dominated by NR-EFT operators and propose new variables, which are more relevant for some of the signal topology
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