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Claudio Dib

Publications and source records attributed to Claudio Dib.

At least 19 recordsLinked to original sources
arXiv2026

Electron-muon colliders at high energies to discover heavy sterile neutrinos

We study high-energy charged-lepton-flavor-violating (cLFV) channels in $e^- \mu^+$ scattering to probe heavy sterile neutrinos, which arise naturally in minimal extensions of the Standard Model. For $\sqrt{s} \le 2M_W$, we consider the process $e^- \mu^+ \to e^+ \mu^-$, which is dominated by one-loop box diagrams. We numerically evaluate these diagrams, involving a high-energy extension of the Inami-Lim functions, and find that the amplitudes are strongly suppressed because of their quartic dependence on light-heavy mixing. Using current bounds on active-sterile neutrino mixing, we determine the maximal rates allowed by existing constraints. For $\sqrt{s} > 2M_W$, we analyze the process $e^- \mu^+ \to W^+ W^-$ and compute the corresponding cross sections in both single-sterile and minimal type-I seesaw scenarios. We find this latter process to be significantly more promising for revealing the presence of heavy sterile neutrinos at $e-\mu$ colliders.

hep-ph↗
arXiv2024

A common framework for fermion mass hierarchy, leptogenesis and dark matter

In this work, we explore an extension of the Standard Model designed to elucidate the fermion mass hierarchy, account for the dark matter relic abundance, and explain the observed matter-antimatter asymmetry in the universe. Beyond the Standard Model particle content, our model introduces additional scalars and fermions. Notably, the light active neutrinos and the first two generations of charged fermions acquire masses at the one-loop level. The model accommodates successful low-scale leptogenesis, permitting the mass of the decaying heavy right-handed neutrino to be as low as 10 TeV. We conduct a detailed analysis of the dark matter phenomenology and explore various interesting phenomenological implications. These include charged lepton flavor violation, muon and electron anomalous magnetic moments, constraints arising from electroweak precision observables, and implications for collider experiments.

hep-ph↗
arXiv2024

Spontaneous Symmetry Breaking and Panic Escape

Panic-induced herding in individuals often leads to social disasters, resulting in people being trapped and trampled in crowd stampedes triggered by panic. We introduce a novel approach that offers fresh insights into studying the phenomenon of asymmetrical panic-induced escape. Our approach is based on the concept of Spontaneous Symmetry Breaking (SSB), a fundamental governing mechanism in the Physical Sciences. By applying the principles of SSB, we conjecture that the onset of disastrous effects of panic can be understood as a SSB phenomenon, and we formulate the process accordingly. We highlight that this way of understanding panic escape leads to simple general measures of preventing catastrophic situations, by considering two crucial parameters: \emph{population density} and \emph{external information}. The interplay of these two parameters is responsible for either breaking or restoring the symmetry of a system. We describe how these parameters are set by design conditions as well as crowd control. Based on these parameters, we discuss strategies for preventing potential social disasters caused by asymmetrical panic escape.

physics.soc-ph↗
arXiv2022

Improvement of W Boson Hadronic Decay Width up to $\mathcal{O}\left(\alpha_s^4 \right)$-order

The principle of maximum conformality (PMC) is used to remove uncertainties in the renormalization scale and scheme, thus eliminating unnecessary systematic errors for high-precision perturbative Quantum Chromodynamics (pQCD) predictions. In this work, we use PMC method to improve the determination of the decay width of the $W$ boson in hadrons by working on the corrections coming from pQCD theory at the four-loop level. In conventional scale setting, we find that the initial scaling dependence of the renormalization is small only at high correction orders, whereas in single-scale PMC method we obtain a scaling-independent initial result. Finally, the wide hadronic decay of $W$ is used for an indirect determination of the charm-strange mixing parameter.

hep-ph↗
arXiv2022

Why should the U.S. care about high energy physics in Africa and Latin America?

Research, education and training in high energy physics (HEP) often draw international collaborations even when priorities and long term visions are defined regionally or nationally. Yet in many developing regions, HEP activities are limited in both human capacity and expertise, as well as in resource mobilisation. In this paper, the benefits -- to the U.S. HEP program -- of engagements with developing countries are identified and studied through specific examples of Africa and Latin America; conversely, the impact of HEP education and research for developing countries are also pointed out. In the context of the U.S. strategic planning for high energy physics, the authors list recommendations on investments that will benefit both developed and developing nations.

physics.soc-ph↗
arXiv2021

Quasi-Dirac neutrinos in the linear seesaw model

We implement a minimal linear seesaw model (LSM) for addressing the Quasi-Dirac (QD) behaviour of heavy neutrinos, focusing on the mass regime of $M_{N} \lesssim M_{W}$. Here we show that for relatively low neutrino masses, covering the few GeV range, the same-sign to opposite-sign dilepton ratio, $R_{\ell \ell}$, can be anywhere between 0 and 1, thus signaling a Quasi-Dirac regime. Particular values of $R_{\ell \ell}$ are controlled by the width of the QD neutrino and its mass splitting, the latter being equal to the light-neutrino mass $m_{\nu}$ in the LSM scenario. The current upper bound on $m_{\nu_{1}}$ together with the projected sensitivities of current and future $|U_{N \ell}|^{2}$ experimental measurements, set stringent constraints on our low-scale QD mass regime. Some experimental prospects of testing the model by LHC displaced vertex searches are also discussed.

hep-ph↗
arXiv2019

Low-scale seesaw from neutrino condensation

Knowledge of the mechanism of neutrino mass generation would help understand a lot more about Lepton Number Violation (LNV), the cosmological evolution of the Universe, or the evolu tion of astronomical objects. Here we propose a verifiable and viable extension of the Standard model for neutrino mass generation, with a low-scale seesaw mechanism via LNV condensation in the sector of sterile neutrinos. To prove the concept, we analyze a simplified model of just one single family of elementary particles and check it against a set of phenomenological constraints coming from electroweak symmetry breaking, neutrino masses, leptogenesis and dark matter. The model predicts (i) TeV scale quasi-degenerate heavy sterile neutrinos, suitable for leptogenesis with resonant enhancement of the CP asymmetry, (ii) a set of additional heavy Higgs bosons whose existence can be challenged at the LHC, (iii) an additional light and sterile Higgs scalar which is a candidate for decaying warm dark matter, and (iv) a majoron. Since the model is based on simple and robust principles of dynamical mass generation, its parameters are very restricted, but remarkably it is still within current phenomenological limits.

hep-ph↗
arXiv2017

Probing the Dirac or Majorana nature of the Heavy Neutrinos in pure leptonic decays at the LHC

We propose a strategy for distinguishing the Dirac / Majorana character of heavy neutrinos with masses below the $W$ boson mass, using purely leptonic decays at the LHC. The strategy makes use of a forward-backward asymmetry of the opposite charge lepton in the $W^{+}\rightarrow l^{+}l^{+}l^{'-}\nu$ decay. In order to check the experimental feasibility of the model, we show, through a numerical analysis, that in the decay $W^{+}\rightarrow e^{+}e^{+}\mu^{-}\nu$ the two positrons in the final state can be distinguished for different ranges of the heavy neutrino masses. Finally, we estimated the number of events of $W^{+}\rightarrow e^{+}e^{+}\mu^{-}\nu$ for a Dirac and Majorana $N$ neutrino. For an integrated luminosity of 120 fb$^{-1}$ at LHC RUN II, signals can be found if heavy-to-light neutrino mixings are $ |U_{N \mu}|^2,|U_{N e}|^2 \gtrsim 10^{-6} $.

hep-ph↗
arXiv2015

Probing the Majorana neutrinos and their CP violation in decays of charged scalar mesons $π, K, D, D_s, B, B_c$

Some of the outstanding questions of particle physics today concern the neutrino sector, in particular whether there are more neutrinos than those already known and whether they are Dirac or Majorana particles.There are different ways to explore these issues. In this article we describe neutrino-mediated decays of charged pseudoscalar mesons such as $π^{\pm}$, $K^{\pm}$ and $B^{\pm}$, in scenarios where extra neutrinos are heavy and can be on their mass shell. We discuss semileptonic and leptonic decays of such kinds. We investigate possible ways of using these decays in order to distinguish between the Dirac and Majorana character of neutrinos. Further, we argue that there are significant possibilities of detecting CP violation in such decays when there are at least two almost degenerate Majorana neutrinos involved. This latter type of scenario fits well into the known neutrino minimal standard model ($ν$MSM) which could simultaneously explain the Dark Matter and Baryon Asymmetry of the Universe.

hep-ph↗
arXiv2012

Probing Majorana neutrinos in rare pi+ to e+ e+ mu- nu decays

We study the rare decays of charged π mesons, π+ to e+ e+ μ- anti-ν_μ and π+ to e+ μ- e+ ν_e, induced by a sterile neutrino N with a mass in the range m_μ< m_N < m_π. The first process violates Lepton Number by two units and so occurs only if N is Majorana, while the second process conserves Lepton Number and occurs irrespective of the Majorana or Dirac character of N. We study a way to distinguish the Majorana vs. Dirac character of N in these processes using the muon spectrum. We also find that the branching ratios could be at the reach of high luminosity experiments like Project X at FNAL or any proposed neutrino (or muon) factories worldwide.

hep-ph↗
arXiv2011

Heavy Sterile Neutrinos in Tau Decays and the MiniBooNE Anomaly

Current results of the MiniBooNE experiment show excess events that indicate neutrino oscillations, but only if one goes beyond the standard 3 family scenario. Recently a different explanation of the events has been given, not in terms of oscillations but by the production and decay of a massive sterile neutrino with large transition magnetic moment. We study the effect of such a sterile neutrino in the rare decays $τ^- \rightarrow μ^- μ^+ π^- ν$ and $τ^{-}\rightarrow μ^{-} μ^{+} e^{-} νν$. We find that searches for these decays featuring displaced vertices between the $μ^-$ and the other charged particles, constitute good tests for the existence of the sterile neutrino proposed to explain the MiniBooNE anomaly. These searches could be done with already existing experimental data.

hep-ph↗
arXiv2011

On Sterile neutrino explanation of LSND and MiniBooNE anomalies

We examine the compatibility between existing experimental data and a recently proposed explanation of the LSND and MiniBooNE anomalies, given in terms of a sterile neutrino $N$ whose decay is dominated by a radiative mode. We find that current experimental data on $τ\rightarrow μννγ$ decays are compatible with the sterile neutrino parameters required for the explanation of the anomalies, but $K\rightarrow μνγ$ shows a marginal tension with those parameters. We also propose experimental cuts on radiative $K$ decays that could test the sterile neutrino hypothesis better. Finally, we study the contribution of this sterile neutrino to $K\toμνe e$, and find that measurements of this process would provide powerful tests for the sterile neutrino explanation of the LSND and MiniBooNE anomalies, if the experimental cut on the invariant mass of the $e^{+}e^{-}$ pair could be reduced from its current value of 145 MeV to a value below 40 MeV.

hep-ph↗
arXiv2010

Probing Majorana neutrinos in rare K and D, D_s, B, B_c meson decays

We study lepton number violating decays of charged K, D, D_s, B and B_c mesons of the form M^+\to {M'}^-\ell^+\ell^+, induced by the existence of Majorana neutrinos. These processes provide information complementary to neutrinoless double nuclear beta decays, and are sensitive to neutrino masses and lepton mixing. We explore neutrino mass ranges m_N from below 1 eV to several hundred GeV. We find that in many cases the branching ratios are prohibitively small, however in the intermediate range m_π< m_N < m_{B_c}, in specific channels and for specific neutrino masses, the branching ratios can be at the reach of high luminosity experiments like those at the LHC-b and future Super flavor-factories, and can provide bounds on the lepton mixing parameters.

hep-ph↗
arXiv2006

Strong CP violation and the neutron electric dipole form factor

We calculate the neutron electric dipole form factor induced by the CP violating theta-term of QCD, within a perturbative chiral quark model which includes pion and kaon clouds. On this basis we derive the neutron electric dipole moment and the electron-neutron Schiff moment. From the existing experimental upper limits on the neutron electric dipole moment we extract constraints on the theta-parameter and compare our results with other approaches.

hep-ph↗
arXiv2006

The neutron electric dipole form factor in the perturbative chiral quark model

We calculate the electric dipole form factor of the neutron in a perturbative chiral quark model, parameterizing CP-violation of generic origin by means of effective electric dipole moments of the constituent quarks and their CP-violating couplings to the chiral fields. We discuss the relation of these effective parameters to more fundamental ones such as the intrinsic electric and chromoelectric dipole moments of quarks and the Weinberg parameter. From the existing experimental upper limits on the neutron EDM we derive constraints on these CP-violating parameters.

hep-ph↗
arXiv2005

Neutrino emission rates in highly magnetized neutron stars revisited

Magnetars are a subclass of neutron stars whose intense soft-gamma-ray bursts and quiescent X-ray emission are believed to be powered by the decay of a strong internal magnetic field. We reanalyze neutrino emission in such stars in the plausibly relevant regime in which the Landau band spacing of both protons and electrons is much larger than kT (where k is the Boltzmann constant and T is the temperature), but still much smaller than the Fermi energies. Focusing on the direct Urca process, we find that the emissivity oscillates as a function of density or magnetic field, peaking when the Fermi level of the protons or electrons lies about 3kT above the bottom of any of their Landau bands. The oscillation amplitude is comparable to the average emissivity when the Landau band spacing mentioned above is roughly the geometric mean of kT and the Fermi energy (excluding mass), i. e., at fields much weaker than required to confine all particles to the lowest Landau band. Since the density and magnetic field strength vary continuously inside the neutron star, there will be alternating surfaces of high and low emissivity. Globally, these oscillations tend to average out, making it unclear whether there will be any observable effects.

astro-ph↗
arXiv2001

Resummation of the hadronic tau decay width with the modified Borel transform method

A modified Borel transform of the Adler function is used to resum the hadronic tau decay width ratio. In contrast to the ordinary Borel transform, the integrand of the Borel integral is renormalization--scale invariant. We use an ansatz which explicitly accounts for the structure of the leading infrared renormalon. Further, we use judiciously chosen conformal transformations for the Borel variable, in order to map sufficiently away from the origin the other ultraviolet and infrared renormalon singularities. In addition, we apply Pade approximants for the corresponding truncated perturbation series of the modified Borel transform, in order to further accelerate the convergence. Comparing the results with the presently available experimental data on the tau hadronic decay width ratio, we obtain $α_s(M^z) = 0.1192 +- 0.0007_{exp.} +- 0.0010_{EW+CKM} +- 0.0009_{th.} +- 0.0003_{evol.}$. These predictions virtually agree with those of our previous resummations where we used ordinary Borel transforms instead.

hep-ph↗