arXiv subjects

Vladimir Tello

Publications and source records attributed to Vladimir Tello.

14 recordsLinked to original sources

arXiv2026

Strong CP and the PMNS Phase in Dirac Left-Right Symmetry

Left--right symmetric theories with generalized parity restrict the bare QCD angle to a CP-conserving value and relate the physical strong-CP phase $\bar\theta$ to a CP-odd parity-breaking parameter $\eps$. We show that, in the Dirac-neutrino realization, imposing a sectorial reality condition on the Dirac lepton Yukawa matrices turns observable leptonic CP violation from an independent input into a branch-dependent prediction. Parity reconstructs the right-handed leptonic mixing matrix, whereas leptonic reality requires it to be rephasing-equivalent to the complex conjugate of the left-handed one. For generic three-generation Yukawas, compatibility is equivalent to the vanishing of a single Jarlskog-type CP-odd invariant. In the physical Dirac hierarchy, for fixed oscillation data, mass ordering, and discrete leptonic branch, compatibility determines the PMNS Jarlskog invariant as a function of the lightest neutrino mass and $\eps$. We derive its leading analytic behavior and obtain the nonlinear compatibility branches numerically. In compressed mixed-sign Dirac-neutrino spectra, small signed mass sums can amplify a tiny parity deformation into order-one values of the normalized PMNS Jarlskog invariant, including maximal CP violation. The corresponding quark reconstruction independently provides a calculable, branch-dependent conversion between $\eps$ and $\bar\theta$. Together, the leptonic and quark relations define a family of correlations among leptonic CP violation, the absolute neutrino mass scale, and strong CP.

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arXiv2026

Right-Handed Leptonic Mixing and Enhancement Band in Left-Right Symmetry

Left-right (LR) symmetric theories predict right-handed charged currents whose flavor structure encodes the realization of parity. While the right-handed quark mixing matrix closely tracks its left-handed counterpart, the leptonic sector with purely Dirac neutrinos has remained structurally unclear. We show that, in contrast to the quark case, parity in the Dirac leptonic sector admits a localized, branch-dependent enhancement band in which RH-LH misalignment becomes parametrically large despite small parity breaking. We derive analytic solutions of the LR consistency equation and demonstrate that the interplay between spontaneous parity violation and spectral near-degeneracies leads to a qualitatively new pattern of right-handed mixing. This establishes the Dirac leptonic sector of the minimal LR model as a predictive and structurally distinct regime.

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arXiv2023

Neutrinoless double beta decay: neutrino mass versus new physics

Neutrinoless double beta decay is the textbook example of lepton number violation, often claimed to be a probe of neutrino Majorana mass. However, it could be triggered by new physics; after all, neutrino Majorana mass requires physics beyond the Standard Model. If at least one electron were right-handed, it would automatically signify new physics rather than neutrino mass. In case both electrons were left-handed, the situation would become rather complicated, and additional effort would be needed to untangle the source for this process. We offer a comprehensive study of this issue from both the effective operator approach and the possible UV completions, including the Pati-Salam quark-lepton unification. While neutrino exchange is natural and physically preferred, our findings show that new physics can still be responsible for the neutrinoless double beta decay. In particular, the Pati-Salam theory can do the job, consistently with all the phenomenological and unification constraints, as long as the unification scale lies above 10^12 GeV, albeit at the price of fine-tuning of some scalar masses.

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arXiv2023

Spontaneous Parity Violation

We review here the central features of the idea of spontaneous breakdown of parity, in the context of its minimal realization, the Left-Right symmetric gauge theory.

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arXiv2020

Strong CP violation: problem or blessing?

We readdress the issue of strong CP violation both in the Standard Model and in the Minimal Left-Right Symmetric Model and try to clear the confusion that seems to still pervade the field. We argue that the smallness of strong CP violation, while harmless and basically decoupled from the rest of physics in the SM, in the context of LR symmetry provides a blessing by helping to narrow down the parameter space of the theory and connecting apparently uncorrelated physical quantities. In particular, in the context of left-right symmetry being parity, it either points to the suppression of leptonic CP violation noticed before, or it leads to relatively light right-handed neutrinos, potentially accessible at the next hadron collider. The latter, more natural in view of complex quark Yukawa couplings, goes hand in hand with the smallness of lepton flavor violation and enhances the possibility of observing neutrinoless double beta decay.

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arXiv2020

Parity and the origin of neutrino mass

In the LHC era the issue of the origin and nature of neutrino mass has attained a new meaning and a renewed importance. The growing success of the Higgs-Weinberg mechanism behind the charged fermion masses paves the way for the question of neutrino mass. We have shown recently how the spontaneous breaking of parity in the context of the minimal Left-Right Symmetric Model allows to probe the origin of neutrino mass in complete analogy with the charged fermions masses in the Standard Model. We revisit here this issue and fill in the gaps left in our previous work. In particular we discuss a number of different mathematical approaches to the problem of disentangling the seesaw mechanism and show how a unique analytical solution emerges. Most important, we give all the possible expressions for the neutrino Dirac mass matrix for general values of light and heavy neutrino mass matrices. In practical terms what is achieved is an untangling of the seesaw mechanism with clear and precise predictions testable at hadron colliders such as LHC.

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arXiv2019

Disentangling Seesaw in the Minimal Left-Right Symmetric Model

In a recent Letter we presented a systematic way of testing the seesaw origin of neutrino mass in the context of the Minimal Left-Right Symmetric Model. The essence of the program is to exploit lepton number violating decays of doubly charged scalars, particles which lie at the heart of the Higgs-mechanism-based seesaw, to probe the Dirac neutrino mass term which in turn enters directly into a number of physical processes including the decays of right-handed neutrinos into the $W$ boson and left-handed charged leptons. In this longer version we discuss at length these and related processes, and offer some missing technical details. We also carefully analyze the physically appealing possibility of parity conserving Yukawa sector showing that the neutrino Dirac mass matrix can be analytically expressed as a function of light and heavy neutrino masses and mixing, without resorting to any additional discrete symmetries, a context in which the seesaw mechanism can be disentangled completely.When parity does get broken, we show that, in the general case, only the Hermitian part of the Dirac mass term is independent which substantially simplifies the task of testing experimentally the origin of neutrino mass. We illustrate this program through some physical examples that allow simple analytical expressions. Our work shows that the Minimal Left-Right Symmetric Model is a self-contained theory of neutrino mass which can be in principle tested at the LHC or the next hadron collider.

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arXiv2016

Probing Seesaw with Parity Restoration

We present a novel way of testing the seesaw origin of neutrino mass in the context of the minimal Left-Right Symmetric Model. It is based on the connection between the leptonic interactions of the doubly charged scalars, whose presence is at the core of the seesaw mechanism, and the neutrino Dirac Yukawa couplings which govern, among other processes, the right-handed neutrino decays into left-handed charged leptons. We prove that any physical quantity depending on these couplings is a function of the hermitian part only which can significantly simplify their future experimental determination.

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arXiv2015

A facility to Search for Hidden Particles at the CERN SPS: the SHiP physics case

This paper describes the physics case for a new fixed target facility at CERN SPS. The SHiP (Search for Hidden Particles) experiment is intended to hunt for new physics in the largely unexplored domain of very weakly interacting particles with masses below the Fermi scale, inaccessible to the LHC experiments, and to study tau neutrino physics. The same proton beam setup can be used later to look for decays of tau-leptons with lepton flavour number non-conservation, $τ\to 3μ$ and to search for weakly-interacting sub-GeV dark matter candidates. We discuss the evidence for physics beyond the Standard Model and describe interactions between new particles and four different portals - scalars, vectors, fermions or axion-like particles. We discuss motivations for different models, manifesting themselves via these interactions, and how they can be probed with the SHiP experiment and present several case studies. The prospects to search for relatively light SUSY and composite particles at SHiP are also discussed. We demonstrate that the SHiP experiment has a unique potential to discover new physics and can directly probe a number of solutions of beyond the Standard Model puzzles, such as neutrino masses, baryon asymmetry of the Universe, dark matter, and inflation

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arXiv2015

Restoration of Parity and the Right-Handed Analog of the CKM Matrix

In a recent Letter we determined analytically the right-handed quark mixing matrix in the minimal Left-Right symmetric theory with generalized Parity. We derived its explicit form as a series expansion in a small parameter that measures the departure from hermiticity of quark mass matrices. Here we analyze carefully the convergence of the series by including higher order terms and by comparing with numerical results. We apply our findings to some phenomenological applications such as the production and decays of the right-handed gauge boson $W_R$, the neutrinoless double beta decay, the decays of the heavy scalar doublet, the strong CP parameter and the theoretical limits on the new mass scale from the $K$ and $B$-meson physics. In particular, we demonstrate that the relevant coupling for the production of the $W_R$ gauge boson at hadronic colliders and for the neutrinoless double beta decay equals its left-handed counterpart, within a percent. We also demonstrate that the stability of the theoretical lower limit on the $W_R$ mass from the $K$-meson physics is due to a partial cancellation of the external phases of the right-handed mixing matrix.

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arXiv2015

Right Handed Quark Mixing in Left-Right Symmetric Theory

We give exact formulas for the right-handed analog of the CKM matrix in the minimal Left-Right symmetric theory, for the case when the Left-Right symmetry is generalized Parity as in the original version of the theory. We derive its explicit form and give a physical reason for the known and surprising fact that the right-handed mixing angles are close in value to the CKM ones, in spite of the Left-Right symmetry being badly broken in nature. We exemplify our results on the production of the right-handed charged gauge boson and the computation of the neutral K meson mass difference.

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arXiv2013

Left-Right Symmetry: from Majorana to Dirac

Probing the origin of neutrino mass by disentangling the seesaw mechanism is one of the central issues of particle physics. We address it in the minimal left-right symmetric model and show how the knowledge of light and heavy neutrino masses and mixings suffices to determine their Dirac Yukawa couplings. This in turn allows one to make predictions for a number of high and low energy phenomena, such as decays of heavy neutrinos, neutrinoless double beta decay, electric dipole moments of charged leptons and neutrino transition moments. We also discuss a way of reconstructing the neutrino Dirac Yukawa couplings at colliders such as the LHC.

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arXiv2011

Neutrinoless Double Beta Decay: Low Left-Right Symmetry Scale?

Experiments in progress may confirm a nonzero neutrinoless double beta decay rate in conflict with the cosmological upper limit on neutrino masses and thus require new physics beyond the Standard Model. A natural candidate is the Left-Right symmetric theory, which led originally to neutrino mass and the seesaw mechanism. In the absence of cancelations of large Dirac Yukawa couplings, we show how such a scenario would require a low scale of Left-Right symmetry breaking roughly below 10 TeV, tantalizingly close to the LHC reach.

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arXiv2011

Left-Right Symmetry: from LHC to Neutrinoless Double Beta Decay

The Large Hadron Collider has a potential to probe the scale of left-right symmetry restoration and the associated lepton number violation. Moreover, it offers hope of measuring the right-handed leptonic mixing matrix. We show how this, together with constraints from lepton flavor violating processes, can be used to make predictions for neutrinoless double beta decay. We illustrate this deep connection in the case of the type-II seesaw.

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