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Ternes, C. A., Gariazzo, S., Hajjar, R., Mena, O., Sorel, M., & Tortola, M. (2019). Neutrino mass ordering at DUNE: An extra nu bonus. Phys. Rev. D, 100(9), 093004–10pp.
Abstract: We study the possibility of extracting the neutrino mass ordering at the future Deep Underground Neutrino Experiment using atmospheric neutrinos, which will be available before the muon neutrino beam starts being operational. The large statistics of the atmospheric muon neutrino and antineutrino samples at the far detector, together with the baselines of thousands of kilometers that these atmospheric (anti) neutrinos travel, provide ideal ingredients to extract the neutrino mass ordering via matter effects in the neutrino propagation through Earth. Crucially, muon capture by argon provides excellent charge tagging, allowing us to disentangle the neutrino and antineutrino signature. This is an important extra benefit of having a liquid argon time projection chamber as a far detector, that could render an similar to 3.5 sigma extraction of the mass ordering after approximately 7 yr of exposure.
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Cepedello, R., Hirsch, M., & Helo, J. C. (2018). Lepton number violating phenomenology of d=7 neutrino mass models. J. High Energy Phys., 01(1), 009–24pp.
Abstract: 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 4/ + 4W, 6/ + 2W etc. We study current constraints on these models from upper bounds on charged lepton flavour violating decays, existing lepton number conserving searches at the LHC and discuss possible future LNV searches.
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de Medeiros Varzielas, I., Lopez-Ibañez, M. L., Melis, A., & Vives, O. (2018). Controlled flavor violation in the MSSM from a unified Delta(27) flavor symmetry. J. High Energy Phys., 09(9), 047–22pp.
Abstract: We study the phenomenology of a unified supersymmetric theory with a flavor symmetry Delta(27). The model accommodates quark and lepton masses, mixing angles and CP phases. In this model, the Dirac and Majorana mass matrices have a unified texture zero structure in the (1, 1) entry that leads to the Gatto-Sartori-Tonin relation between the Cabibbo angle and ratios of the masses in the quark sectors, and to a natural departure from zero of the theta 13(l) angle in the lepton sector. We derive the flavor structures of the trilinears and soft mass matrices, and show their general non-universality. This causes large flavor violating effects. As a consequence, the parameter space for this model is constrained, allowing it to be (dis)proven by flavor violation searches in the next decade. Although the results are model specific, we compare them to previous studies to show similar flavor effects (and associated constraints) are expected in general in supersymmetric flavor models, and may be used to distinguish them.
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Parashar, S., Karan, A., Avnish, Bandyopadhyay, P., & Ghosh, K. (2022). Phenomenology of scalar leptoquarks at the LHC in explaining the radiative neutrino masses, muon g-2, and lepton flavor violating observables. Phys. Rev. D, 106(9), 095040–34pp.
Abstract: We study the phenomenology of a particular leptoquark extension of the Standard Model (SM), namely the doublet-singlet scalar leptoquark extension of the SM (DSL-SM). Besides generating Majorana mass for neutrinos, these leptoquarks contribute to muon and electron (g – 2) and various lepton flavor violating processes. Collider signatures of the benchmark points (BPs), consistent with the neutrino oscillation data, anomalous muon/electron magnetic moments, experimental bounds on the charged lepton flavor violation observables, etc., are studied at the LHC/FCC with center-of-mass energies of 14, 27 and 100 TeV. While the two -1=3 charged colored scalars from the singlet and the doublet leptoquark mix with each other, the charge 2=3 colored scalar from the doublet leptoquark remains pure. With a near-degenerate mass spectrum, the pure and mixed leptoquark states are shown to be distinguishable from multiple final states, while discerning between the two mixed states remains very challenging.
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Navarro-Salas, J., & Pla, S. (2022). Particle Creation and the Schwinger Model. Symmetry-Basel, 14(11), 2435–9pp.
Abstract: We study the particle creation process in the Schwinger model coupled with an external classical source. One can approach the problem by taking advantage of the fact that the full quantized model is solvable and equivalent to a (massive) gauge field with a non-local effective action. Alternatively, one can also face the problem by following the standard semiclassical route. This means quantizing the massless Dirac field and considering the electromagnetic field as a classical background. We evaluate the energy created by a generic, homogeneous, and time-dependent source. The results match exactly in both approaches. This proves in a very direct and economical way the validity of the semiclassical approach for the (massless) Schwinger model, in agreement with a previous analysis based on the linear response equation. Our discussion suggests that a similar analysis for the massive Schwinger model could be used as a non-trivial laboratory to confront a fully quantized solvable model with its semiclassical approximation, therefore mimicking the long-standing confrontation of quantum gravity with quantum field theory in curved spacetime.
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Figueroa, D. G., Lizarraga, J., Urio, A., & Urrestilla, J. (2023). Strong Backreaction Regime in Axion Inflation. Phys. Rev. Lett., 131(15), 151003–7pp.
Abstract: We study the nonlinear dynamics of axion inflation, capturing for the first time the inhomogeneity and full dynamical range during strong backreaction, till the end of inflation. Accounting for inhomogeneous effects leads to a number of new relevant results, compared to spatially homogeneous studies: (i) the number of extra efoldings beyond slow-roll inflation increases very rapidly with the coupling, (ii) oscillations of the inflaton velocity are attenuated, (iii) the tachyonic gauge field helicity spectrum is smoothed out (i.e., the spectral oscillatory features disappear), broadened, and shifted to smaller scales, and (iv) the nontachyonic helicity is excited, reducing the chiral asymmetry, now scale dependent. Our results are expected to impact strongly on the phenomenology and observability of axion inflation, including gravitational wave generation and primordial black hole production.
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del Rio, A., & Agullo, I. (2023). Chiral fermion anomaly as a memory effect. Phys. Rev. D, 108(10), 105025–22pp.
Abstract: We study the nonconservation of the chiral charge of Dirac fields between past and future null infinity due to the Adler-Bell-Jackiw chiral anomaly. In previous investigations [A. del Rio, Phys. Rev. D 104, 065012 (2021)], we found that this charge fails to be conserved if electromagnetic sources in the bulk emit circularly polarized radiation. In this article, we unravel yet another contribution coming from the nonzero, infrared “soft” charges of the external, electromagnetic field. This new contribution can be interpreted as another manifestation of the ordinary memory effect produced by transitions between different infrared sectors of Maxwell theory, but now on test quantum fields rather than on test classical particles. In other words, a flux of electromagnetic waves can leave a memory on quantum fermion states in the form of a permanent, net helicity. We elaborate this idea in both 1 + 1 and 3 + 1 dimensions. We also show that, in sharp contrast, gravitational infrared charges do not contribute to the fermion chiral anomaly.
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Du, M. L., Guo, Z. H., & Oller, J. A. (2021). Insights into the nature of the P-cs(4459). Phys. Rev. D, 104(11), 114034–14pp.
Abstract: We study the nature of the recently observed Pcs(4459) by the LHCb collaboration by employing three methods based on the elastic effective-range expansion and the resulting size of the effective-range, the saturation of the compositeness relation and width of the resonance, and a direct fit to data involving the channels J/psi Lambda, Xi ' c over line D, and Xi c over line D*. We have also considered the addition of a Castillejo-Dalitz-Dyson (CDD) pole but this scenario can be discarded. Our different analyses clearly indicate the molecular nature of the Pcs(4459) with a clear Xi c over line D* dominant component. In relation with heavy-quark-spin symmetry our results also favor the actual existence of two resonances with J=1/2 (the lighter one) and 3/2 (the heavier one) in the energy region of the Pcs(4459). In the scenario of two-resonance for the Pcs(4459), the inclusion of the Xi ' c over line D channel is required for their mass splitting and it allows one to determine the spin structures of the two resonances.
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Song, J., Dai, L. R., & Oset, E. (2023). Evolution of compact states to molecular ones with coupled channels: The case of the X(3872). Phys. Rev. D, 108(11), 114017–11pp.
Abstract: We study the molecular probability of the X(3872) in the D0 over bar D*0 and D+D*- channels in several scenarios. One of them assumes that the state is purely due to a genuine nonmolecular component. However, it gets unavoidably dressed by the meson components to the point that in the limit of zero binding of the D0 over bar D*0 component becomes purely molecular. Yet, the small but finite binding allows for a nonmolecular state when the bare mass of the genuine state approaches the D0 over bar D*0 threshold, but, in this case the system develops a small scattering length and a huge effective range for this channel in flagrant disagreement with present values of these magnitudes. Next we discuss the possibility to have hybrid states stemming from the combined effect of a genuine state and a reasonable direct interaction between the meson components, where we find cases in which the scattering length and effective range are still compatible with data, but even then the molecular probability is as big as 95%. Finally, we perform the calculations when the binding stems purely from the direct interaction between the meson-meson components. In summary we conclude, that while present data definitely rule out the possibility of a dominant nonmolecular component, the precise value of the molecular probability requires a more precise determination of the scattering length and effective range of the D0 over bar D*0 channel, as well as the measurement of these magnitudes for the D+D*- channel which have not been determined experimentally so far.
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Coppola, M., Gomez Dumm, D., Noguera, S., & Scoccola, N. N. (2024). Masses of magnetized pseudoscalar and vector mesons in an extended NJL model: The role of axial vector mesons. Phys. Rev. D, 109(5), 054014–30pp.
Abstract: We study the mass spectrum of light pseudoscalar and vector mesons in the presence of an external uniform magnetic field B., considering the effects of the mixing with the axial-vector meson sector. The analysis is performed within a two-flavor NJL-like model which includes isoscalar and isovector couplings together with a flavor mixing 't Hooft-like term. The effect of the magnetic field on charged particles is taken into account by retaining the Schwinger phases carried by quark propagators, and expanding the corresponding meson fields in proper Ritus-like bases. The spin-isospin and spin-flavor decomposition of meson mass states is also analyzed. For neutral pion masses it is shown that the mixing with axial vector mesons improves previous theoretical results, leading to a monotonic decreasing behavior with B that is in good qualitative agreement with lattice QCD (LQCD) calculations, both for the case of constant or B-dependent couplings. Regarding charged pions, it is seen that the mixing softens the enhancement of their mass with B. As a consequence, the energy becomes lower than the one corresponding to a pointlike pion, improving the agreement with LQCD results. The agreement is also improved for the magnetic behavior of the lowest.thorn energy state, which does not vanish for the considered range of values of B-a fact that can be relevant in connection with the occurrence of meson condensation for strong magnetic fields.
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