We present the Large Hadron Collider (LHC) discovery potential in the $Z'$ and heavy neutrino sectors of a $U(1)_{B-L}$ enlarged Standard Model also encompassing three heavy Majorana neutrinos. This model exhibits novel signatures at the LHC, the most interesting arising from a $Z'$ decay chain involving heavy neutrinos, eventually decaying into leptons and jets. In particular, this signature allows one to measure the $Z'$ and heavy neutrino masses involved. In addition, over a large region of parameter space, the heavy neutrinos are rather long-lived particles producing distinctive displaced vertices that can be seen in the detectors. Lastly, the simultaneous measurement of both the heavy neutrino mass and decay length enables an estimate of the absolute mass of the parent light neutrino.
The phenomenology of absolute neutrino masses is reviewed, focusing on tritium beta decay, cosmological measurements and neutrinoless double-beta decay.
We make a general analysis of neutrino phenomenology for the case neutrino masses are generated by the see-saw mechanism with just two right handed neutrinos. We find general constraints on leptogenesis and lepton flavour violating processes. We also analyse the predictions following from a nontrivial texture zero structure.
Neutrino oscillation phenomenology is briefly reviewed, and impact of the late Professor Masatoshi Koshiba on research on neutrino oscillation is discussed from the viewpoint of phenomenology.
We explain the physics of neutrino oscillation in vacuum and in matter. We attempt to clarify several features of oscillation that can be puzzling when neutrinos are their own antiparticles.
The phenomenology of solar, atmospheric, supernova and laboratory neutrino oscillations is described. Analytical formulae for matter effects are reviewed. The results from oscillations are confronted with neutrinoless double beta decay.
A simple method of the calculation of neutrino transition probabilities in vacuum in the general case of $n$ massive neutrinos is presented. The method proposed fully utilizes the unitarity of the mixing matrix. Three-neutrino case for both neutrino mass hierarchies is considered in some details. Transitions in the case of the sterile neutrinos are also discussed.
Various issues in neutrino phenomenology are reviewed, including: the possibility of large mixing angles in various models for neutrino masses, difficulties for degenerate neutrinos as candidates for hot dark matter, strategies for discriminating between different oscillation interpretations of the atmospheric and solar neutrino anomalies, the programme of work for long-baseline neutrino experiments, and the possible future option of a muon storage ring as a neutrino factory.
We present an overview of the phenomenology of prompt neutrinos produced in the atmosphere by the decay of charmed particles. In face of the great activity involving operational and proposed large scale neutrino telescopes, we discuss the implications of different scenarios in calculating the prompt flux, upon the detectable signals in these experiments.
In this talk, I give an overview on recent theoretical and phenomenological studies of massive neutrinos. First of all, the present status of neutrino mixing parameters is summarized. The phenomenology of neutrino oscillations is then discussed, and current understanding of lepton flavor mixing is presented. Finally, I consider the seesaw models of neutrino masses and briefly mention the direct searches at the CERN Large Hadron Collider (LHC).
It is shown in the three flavor framework that neutrino factories enable us to measure some of the oscillation parameters, such as the sign of $Δm_{32}^2$, $θ_{13}$, $δ$. Some efforts are made to determine the parameters (the muon energy and the neutrino path length) of a neutrino factory to optimize the signals.
We review theoretical ideas, problems and implications of neutrino masses and mixing angles. We give a general discussion of schemes with three light neutrinos. Several specific examples are analyzed in some detail, particularly those that can be embedded into grand unified theories.
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.
We review some fundamental aspects of the theory of neutrino masses and mixing. The results of neutrino oscillation experiments are interpreted as evidence of three-neutrino mixing. Implications for the mixing parameters and the neutrino masses are discussed, with emphasis on the connection with the measurements of the absolute values of neutrino masses in beta decay and neutrinoless double-beta decay experiments and cosmological observations.
We study the phenomenology of d=7 1-loop neutrino mass models. All models in this particular class require the existence of several new $SU(2)_L$ multiplets, both scalar and fermionic, and thus predict a rich phenomenology at the LHC. The observed neutrino masses and mixings can easily be fitted in these models. Interestingly, despite the smallness of the observed neutrino masses, some particular lepton number violating (LNV) final states can arise with observable branching ratios. These LNV final states consists of leptons and gauge bosons with high multiplicities, such as 4l+4W, 6l+2W, etc. …
Neutrino oscillation is the new physics beyond standard model. In this paper we have revisited the issue of neutrino oscillation in simple and delicate manner. Starting from the fundamental quantum mechanical treatment for the neutrinos, we calculated the probabilities for the neutrino oscillating within three flavors. Normal and inverted hierarchy have been taken into account for the solar and atmospheric cases, in vacuum and matter. The probabilities have been plotted for all the cases and discussed.
We reanalyze the recent data from the Liquid Scintillator Neutrino Detector (LSND) experiment, that might indicate anti-nu_mu<--->anti-nu_e mixing. This indication is not completely excluded by the negative results of established accelerator and reactor neutrino oscillation searches. We quantify the region of compatibility by means of a thorough statistical analysis of all the available data, assuming both two-flavor and three-flavor neutrino oscillations. The implications for various theoretical scenarios and for future oscillation searches are studied. The relaxation of the LSND constraints …
We review the status of several phenomenological topics of current interest in neutrino oscillations: (i) Solar neutrino oscillations after the first Sudbury Neutrino Observatory measurements, including both model-independent and model-dependent results; (ii) Dominant nu_mu-->nu_tau oscillations of atmospheric and K2K neutrinos, and possible subdominant oscillations induced by either extra states or extra interactions; and (iii) Four-neutrino scenarios embedding the controversial LSND evidence for oscillations.
The generic predictions of two-texture zero neutrino mass matrices in the flavor basis have been examined especially in relation to the degeneracies between mass matrices within a class and interesting constraints on the neutrino parameters have been obtained. It is shown that the knowledge of the octant of $θ_{23}$, the sign of $\cosδ$ and neutrino mass hierarchy can be used to lift these degeneracies.
(abridged) The physical mechanisms that make a neutrino with standard-model (SM) weak interactions a "lepton-number conservation (LNC) violating" neutrino such as the Majorana neutrino are analysed in a basis of two Majorana states that have opposite charge-parity ("charge-parity basis"). A small Majorana mass that is larger than any Dirac mass makes the neutrino not a Majorana but a "pseudo-Majorana" particle that has no definite chirality and therefore has a different phenomenology than the physical neutrino. A combination of a large Majorana and Dirac mass of nearly equal value makes the ne…
We formulate general conditions on $3\times 3$ neutrino mass matrices under which a degenerate pair of neutrinos at a high scale would split at low scale by radiative corrections involving only the standard model fields. This generalizes the original observations of Wolfenstein on pseudo Dirac neutrinos to three generations. A specific model involving partially broken discrete symmetry and solving the solar and atmospheric anomalies is proposed. The symmetry pattern of the model naturally generates two large angles one of which can account for the large angle MSW solution to the solar neutrino…
The Zee model for Dirac neutrinos is one of the simplest models featuring one-loop Dirac neutrino masses. The interactions between the new scalars (two singly-charged fields) and neutrinos induce general neutrino interactions (GNI) which, as a generalisation of the non standard neutrino interactions, constitute an additional tool to probe models beyond the SM like this. In this work, we consider a $U(1)_{B-L}$ gauge symmetry as the responsible for the Diracness of the neutrinos and the radiative character of the neutrino masses. We determine the viable parameter space consistent with neutrino …
In this thesis we investigate several topics in neutrino physics, with an em- phasis on the phenomenology of the sterile neutrinos. We study the existence of a light sterile neutrino within the so called 3+1 scenario using the data of the medium baseline reactor experiments. We will also probe the parameters of the Large Extra Dimension model with the high energy atmospheric data of the IceCube experiment, and will find an equivalence between the Kaluza Klein modes and the sterile neutrinos. We will study the secret interaction of the ster- ile neutrinos which is proposed to solve the tension …
The relevance of the data concerning upward--going muons for the solution of the atmospheric neutrino problem is stressed. In particular, their inclusion in the analysis confirms the goodness of the neutrino oscillation hypothesis and allows to exclude some alternative, exotic explanations such as neutrino decay, flavour changing neutral currents, violations of the equivalence principle (at least in their simplest forms), and also to discriminate, in principle, between different neutrino oscillation models (nu_mu <-> nu_tau versus nu_mu <-> nu_s), because of the difference in the matter effect…
In this paper, we present several possible anomaly-free implementations of the Branco-Grimus-Lavoura (BGL) model with two Higgs doublets and one singlet scalar. The model also includes three generations of massive neutrinos that get their mass via a type-I seesaw mechanism. A particular anomaly-free realization, which we dub $ν$BGL-1 scenario, is subjected to an extensive phenomenological analysis, from the perspective of flavour physics and collider phenomenology.
We consider supersymmetric extension of standard electroweak model with Dirac neutrino masses. In such model for significant region of the parameters right-handed tau sneutrino is the lightest superparticle and right-handed charged tau slepton is the next to lightest superparticle. Due to the smallness of the neutrino masses the right-handed tau slepton is long-lived particle that changes the standard signatures used in the search for supersymmetry at supercolliders. The most striking signatures of such scenario is the existence of highly ionizing tracks and excess of multilepton events that i…
Neutrinoless double beta decay violates lepton number by two units, a positive observation therefore necessarily implies physics beyond the standard model. Here, three possible contributions to neutrinoless double beta decay are briefly reviewed: (a) The mass mechanism and its connection to neutrino oscillations; (b) Left-right symmetric models and the lower limit on the right-handed W boson mass; and (c) R-parity violating supersymmetry. In addition, the recently published ``extended black box'' theorem is briefly discussed. Combined with data from oscillation experiments this theorem provide…
A sterile neutrino in addition to the three known neutrinos seems unavoidable if one wants a simultaneous understanding of the results of the LSND experiment indicating $ν_μ-ν_e$ oscillation together with other evidences for neutrino oscillations such as those from solar and atmospheric neutrino deficits. A major theoretical challenge then is to understand why the sterile neutrino is so light. A simple solution appears to be to assume that it is the lightest neutrino of a mirror sector of the universe which has identical matter and gauge content as the standard model. After a brief review of t…
We show that neutrino telescopes, optimized for detecting neutrinos of TeV to PeV energy, can reveal threshold effects associated with TeV-scale gravity. The signature is an increase with energy of the cross section beyond what is predicted by the Standard Model. The advantage of the method is that the neutrino cross section is measured in an energy region where i) the models are characteristically distinguishable and ii) the Standard Model neutrino cross section can be reliably calculated so that any deviation can be conclusively identified.
We present a model based on the A4 non-abelian discrete symmetry leading to a predictive five-parameter neutrino mass matrix and providing a stable dark matter candidate. We found an interesting correlation among the atmospheric and the reactor angles which predicts theta_23 ~ pi/4 for very small reactor angle and deviation from maximal atmospheric mixing for large theta_13. Only normal neutrino mass spectrum is possible and the effective mass entering the neutrinoless double beta decay rate is constrained to be |m_ee| > 4 10^{-4} eV.
We study neutrino masses in the framework of the supersymmetric inverse seesaw model. Different from the non-supersymmetric version a minimal realization with just one pair of singlets is sufficient to explain all neutrino data. We compute the neutrino mass matrix up to 1-loop order and show how neutrino data can be described in terms of the model parameters. We then calculate rates for lepton flavour violating (LFV) processes, such as $μ\to e γ$, and chargino decays to singlet scalar neutrinos. The latter decays are potentially observable at the LHC and show a characteristic decay pattern dic…
In this thesis I discuss in some detail the possibility that neutrinos are Dirac. If this is indeed the case, some extra symmetries beyond the Standard Model gauge group need to be enforced in order to protect Diracness and the smallness of neutrino mass. These symmetries may have a deep connection with other physics sectors, like Dark Matter stability. I also review the general seesaw framework applied to Dirac neutrinos in a model-independent way thanks to the analysis of generalized Weinberg operators and give some simple, elegant UV complete examples both for seesaw variants and radiative …
We consider the prospects for a neutrino factory to measure mixing angles, the CP violating phase and mass-squared differences by detecting wrong-charged muons arising from the chain μ^+ to ν_e to ν_μ to μ^- and the right-charged muons coming from the chain μ^+ to \barν_μ to \barν_μ to μ^+ (similar to μ^- chains), where ν_e to ν_μ and \barν_μ to \barν_μ are neutrino oscillation channels through a long baseline. First, we perform the baseline and energy optimization of the neutrino factory including the latest simulation results from the magnetized iron neutrino detector (MIND). Second, we stud…
We consider a model of dynamical neutrino masses via the see-saw mechanism. Nambu-Goldstone bosons (majorons) arise associated with the formation of the heavy right-handed majorana masses. These bosons then acquire naturally soft masses (become pNGB's) at loop level via the Higgs-Yukawa mass terms. These models, like the original neutrino pNGB quintessence schemes of the 1980's that proceed through the Dirac masses, are natural, have cosmological implications through mass varying neutrinos, long range forces, and provide a soft potential for dark energy. We further argue that these models can …
Motivated by the recent SuperKamiokande results on atmospheric neutrinos, we incorporate massive neutrinos, with large angle oscillation between the second and third generations, in a theory with R-parity violating supersymmetry. The general features of such a theory are briefly reviewed. We emphasize its testability through the observation of comparable numbers of muons and taus, produced together with the W-boson, in decays of the lightest neutralino. A distinctly measurable decay gap is another remarkable feature of such a scenario.
We study a model of neutrino within the framework of the minimal extended seesaw (MES), which plays an important role in active and sterile neutrino phenomenology in (3+1) scheme. The $A_4$ flavor symmetry is augmented by an additional $Z_4\times Z_3$ symmetry to constraint the Yukawa Lagrangian of the model. We use non-trivial Dirac mass matrix, with broken $μ-τ$ symmetry, as the origin of leptonic mixing. Interestingly, such a structure of mixing naturally leads to the non-zero reactor mixing angle $θ_{13}$. Non-degenerate mass structure for right-handed neutrino $M_R$ is considered so that …
In Split Supersymmetry scenarios the possibility of having a very heavy gravitino opens the door to alleviate or completely solve the worrisome "gravitino problem'' in the context of supersymmetric baryogenesis models. Here we assume that the gravitino may indeed be heavy and that Majorana masses for neutrinos are forbidden as well as direct Higgs Yukawa couplings between left and right handed neutrinos. We investigate the viability of the mechansim known as Dirac leptogenesis (or neutrinogenesis), both in solving the baryogenesis puzzle and explaining the observed neutrino sector phenomenolog…
Assuming a type-I seesaw mechanism for neutrino mass generation and invoking a baryogengesis via leptogenesis scenario, we consider a reasonable hierarchical structure for Dirac neutrino mass matrix, similar to up-type quark mass matrix. These hypotheses imply a relevant connection between high scale CP violation and low energy one. By requiring a compact heavy neutrino mass spectrum, which allows to circumvent Davidson-Ibarra limit, one can obtain an efficient leptogenesis restricting the allowed region for low energy neutrino parameters. Once the oscillating parameters are taken inside a $3σ…
Among three typical energy scales, a neutrino mass scale ($m_ν\sim$ 0.1 eV), a GUT scale ($M_{GUT}\sim 10^{16}$ GeV), and a TeV-scale ($M_{NP}\sim$ 1 TeV), there is a fascinating relation of $M_{NP}\simeq \sqrt{m_ν\cdot M_{GUT}}$.The TeV-scale, $M_{NP}$, is a new physics scale beyond the standard model which is regarded as "supersymmetry" (SUSY) in this letter. We investigate phenomenology of SUSY SU(5) GUT with neutrinophilic Higgs, which realizes the above relation dynamically as well as the suitable magnitude of Dirac mass, $m_ν$, through a tiny vacuum expectation value of neutrinophilic Hi…
The search for possible mixing patterns of charged leptons and neutrinos is important to get clues of the origin of nearly maximal mixings, since there are some preferred bases of the lepton mass matrices given by underlying theories. We systematically examine the mixing patterns which could lead to large lepton mixing angles. We find out 37 mixing patterns are consistent with experimental data if taking into account phase factors in the mixing matrices. Only 6 patterns of them can explain the observed data without any tuning of parameters, while the others need particular choices for phase va…
We present a minimal left-right symmetric flavor model and analyze the predictions for the neutrino sector. In this scenario, the Yukawa sector is shaped by the dihedral $D_4$ symmetry which leads to correlations for the neutrino mixing parameters. We end up with four possible solutions within this model. We further analyzed the impact of the upcoming long-baseline neutrino oscillation experiment DUNE. Due to its high sensitivity, DUNE will be able to rule out two of the solutions. Finally, the prediction for the neutrinoless double beta decay for the model has also been examined.
We have constrained unparticle interactions with neutrinos and electrons using available data on neutrino-electron elastic scattering and the four CERN LEP experiments data on mono photon production. We have found that, for neutrino-electron elastic scattering, the MUNU experiment gives better constraints than previous reported limits in the region d>1.5. The results are compared with the current astrophysical limits, pointing out the cases where these limits may or may not apply. We also discuss the sensitivity of future experiments to unparticle physics. In particular, we show that the measu…
This article summarises the status of the solar neutrino oscillation phenomenology at the end of 2002 in the light of the SNO and KamLAND results. We first present the allowed areas obtained from global solar analysis and demonstrate the preference of the solar data towards the Large-Mixing-Angle (LMA) MSW solution. A clear confirmation in favor of the LMA solution comes from the \kl reactor neutrino data. The \kl spectral data in conjunction with the global solar data further narrows down the allowed LMA region and splits it into two allowed zones -- a low $Δm^2$ region (low-LMA) and high $Δm…
We study a model in which lepton number violation is solely triggered by a dimension 4 hard breaking term in the scalar potential. A minimal model which contains a SU(2) triplet with hypercharge Y=2, and a pair of singlet doubly charged scalar fields in addition to the Standard Model (SM) Higgs doublet is constructed. The model is technically natural in the sense that lepton number is preserved in the limit that the hard term vanishes. SM phenomenology restricts the vacuum expectation value of the triplet scalar field $v_T<5.78$ GeV. Neutrino masses controlled by $v_T$ are generated at the two…
We present a TeV scale seesaw mechanism for exploring the dark matter and neutrino phenomenology in the light of recent neutrino and cosmology data. A different realization of the Inverse seesaw(ISS) mechanism with $A_{4}$ flavor symmetry is being implemented as a leading contribution to the light neutrino mass matrix which usually gives rise to vanishing reactor mixing angle $θ_{13}$. Using a non-diagonal form of Dirac neutrino mass matrix and $3σ$ values of mass square differences we parameterize the neutrino mass matrix in terms of Dirac Yukawa coupling "$y$". We then use type II seesaw as …
We show how neutrino data can be used in order to constrain the free parameters of possible extensions to the standard model of elementary particles (SM). For definiteness, we focus in the recently proposed unparticle scenario. We show that neutrino data, in particular the MUNU experiment, can set stronger bounds than previous reported limits in the scale dimension parameter for certain region (d > 1.5). We compute the sensitivity of future neutrino experiments to unparticle physics such as future neutrino-electron scattering detectors, coherent neutrino-nuclei scattering as well as the ILC . …
We suggest that a singlet fermion $S$ exists beyond the standard see-saw structure. It mixes with light neutrinos via interactions with the right-handed neutrino components, so that $\n_e \to S$ conversion solves the solar neutrino problem. Supersymmetry endowed with R-symmetry is shown to give a natural framework for existence, mass scale and mixing ($\sin^22þ_{es} \sim (0.1-1.5)\cdot 10^{-2}$) of such a fermion. Models with an approximate horizontal symmetry are constructed, which embed the fermion $S$ and explain simultaneously solar, atmospheric, hot dark matter problems as well as may pre…
We consider an anomaly-free $\mathrm{U}(1)$ extension of the Standard Model with three right-handed neutrinos (RHNs) and two complex scalars, wherein the charge assignments preclude all tree-level mass terms for the neutrinos. Considering this setup, in turn, to be only a low-energy effective theory, we introduce higher-dimensional terms {\em a la} Froggatt-Nielsen to naturally generate tiny neutrino masses. One of the RHNs turns out to be very light, thereby constituting the main decay mode for the $Z'$ and hence relaxing the LHC dilepton resonance search constraints. This very RHN has a life…
We discuss the phenomenological consequences of theories which describe sterile neutrinos in large extra dimensions. We show that the Kaluza-Klein tower of the singlet neutrinos, albeit tiny individual contribution in electroweak processes, act cumulatively, giving rise to non-universality of the weak interactions of the light neutrinos and to flavour-violating radiative processes. Owing to these non-decoupling effects of th Kaluza--Klein neutrinos, we derive strong constraints on the parameters of the theory that originates from the non-observation of flavour-violating and universality-breaki…
We perform a phenomenological study of the scalar sector of two models that generate neutrino mass at the three-loop level and contain viable dark matter candidates. Both models contain a charged singlet scalar and a larger scalar multiplet (triplet or quintuplet). We investigate the effect of the extra scalars on the Higgs mass and analyze the modifications to the triple Higgs coupling. The new scalars can give observable changes to the Higgs decay channel $h\rightarrowγγ$ and, furthermore, we find that the electroweak phase transition becomes strongly first-order in large regions of paramete…
The $μν$SSM solves the $μ$ problem of the MSSM and explains the origin of neutrino masses by simply using right-handed neutrino superfields. The solution implies the breaking of R-parity. The properties and phenomenology of the model are briefly reviewed.
Dark matter (DM) and neutrinos are the two most compelling pieces of evidence of new physics beyond the Standard Model of Particle Physics but these are often treated as belonging to two different sectors. Yet DM-neutrino interactions are known to have cosmological consequences. Here, we study the scenario of a scalar DM candidate coupled to left-handed neutrinos via a Dirac mediator. We determine the mass of a DM candidate that yields the right DM relic abundance in a thermal scenario and it is consistent with large-scale structure formation. In order to satisfy both constraints, a complex DM…
We study the possibility of simultaneously addressing neutrino phenomenology and the dark matter in the framework of inverse seesaw. The model is the extension of the standard model by the addition of two right handed neutrinos and three sterile fermions which leads to a light sterile state with the mass in the keV range along with three light active neutrino states. The lightest sterile neutrino can account for a feasible dark matter(DM) candidate. We present a $S_{4}$ flavor symmetric model which is further augmented by $Z_{4}\times Z_{3}$ symmetry to constrain the Yukawa Lagrangian. The str…
