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Liang, W. H., Chen, H. X., Oset, E., & Wang, E. (2019). Triangle singularity in the J/psi -> K+K- f(0)(980)(a(0)(980)) decays. Eur. Phys. J. C, 79(5), 411–11pp.
Abstract: We study the J/psi -> K+K- f(0)(980)(a(0)(980)) reaction and find that the mechanism to produce this decay develops a triangle singularity around M-inv(K- f(0)/K- a(0)) approximate to 1515 MeV. The differential width d Gamma/dM(inv)(K- f(0)/K- a(0)) shows a rapid growth around the invariant mass being 1515 MeV as a consequence of the triangle singularity of this mechanism, which is directly tied to the nature of the f(0)(980) and a(0)(980) as dynamically generated resonances from the interaction of pseudoscalar mesons. The branching ratios obtained for the J/psi -> K+K- f(0)(980)(a(0)(980)) decays are of the order of 10(-5), accessible in present facilities, and we argue that their observation should provide relevant information concerning the nature of the low-lying scalar mesons.
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Sakai, S., Oset, E., & Guo, F. K. (2020). Triangle singularity in the B-> K- pi X-0 (3872) reaction and sensitivity to the X(3872) mass. Phys. Rev. D, 101(5), 054030–10pp.
Abstract: We have done a study of the B--> K-pi X-0(3872) reaction by means of a triangle mechanism via the chain of reactions: B--> K-D*(0);(D) over bar*(0); D*(0)-> pi D-0(0); D-0(D) over bar*(0)-> X(3872). We show that this mechanism generates a triangle singularity in the pi X-0(3872) invariant mass for a very narrow window of the X(3872) mass, around the present measured values, and show that the peak positions and the shape of the mass distributions arc sensitive to the X(3872) mass, such that a measurement of the reaction can serve to improve on the present values of this mass. In particular, we point out that the X(3872) mass relative to the D-0(D) over bar*(0) threshold may be extracted from the asymmetry of the pi X-0 line shape.
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Dai, L. R., Yu, Q. X., & Oset, E. (2019). Triangle singularity in tau(-) -> nu(tau)pi(-) f(0)(980) (a(0)(980)) decays. Phys. Rev. D, 99(1), 016021–13pp.
Abstract: We study the triangle mechanism for the decay tau(-) -> nu(tau)pi(-) f(0)(980) with the f(0)(980) decaying into pi(+) pi(-). The mechanism for this process is initiated by tau(-) -> nu K-tau*(0) K- followed by the K*(0) decay into pi K--(+), then the K- K+ produce the f(0)(980) through a triangle loop containing K* K+ K- which develops a singularity around 1420 MeV in the pi f(0)(980) invariant mass. We find a narrow peak in the pi(+) pi(-) invariant mass distribution, which originates from the f(0)(980) amplitude. Similarly, we also study the triangle mechanism for the decay tau -> nu pi(-) a(0)(980), with the a(0)(980) decaying into pi(0)eta.The formalism leads to final branching ratios for pi(-) f(0)(980) and pi(-) a(0)(980) of the order of 4 x 10(-4) and 7 x 10(-5), respectively, which are within present measurable range. Experimental verification of these predictions will shed light on the nature of the scalar mesons and on the origin of the “a(1)(1420)” peak observed in other reactions.
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Molina, R., & Oset, E. (2020). Triangle singularity in B- ->K- X(3872); X ->pi 0 pi+ pi- and the X(3872) mass. Eur. Phys. J. C, 80(5), 451–9pp.
Abstract: We evaluate the contribution to the X(3872) width from a triangle mechanism in which the X decays into D0D<overbar></mml:mover>0-cc, then the D0(D<overbar></mml:mover>0) decays into D0 pi 0 (D<overbar></mml:mover>0 pi 0) and the D0D<overbar></mml:mover>0 fuse to produce pi+pi-. This mechanism produces an asymmetric peak from a triangle singularity in the pi+pi- invariant mass with a shape very sensitive to the X mass. We evaluate the branching ratios for a reaction where this effect can be seen in the B--> K-pi 0 pi+pi- reaction and show that the determination of the peak in the invariant mass distribution of pi <mml:mo>+pi <mml:mo>- is all that is needed to determine the X mass. Given the present uncertainties in the X mass, which do not allow to know whether the D<mml:mo>0<mml:mover accent=“true”>D<mml:mo stretchy=“false”><overbar></mml:mover>0 state is bound or not, measurements like the one suggested here should be most welcome to clarify this issue.
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Aristizabal Sierra, D., Bazzocchi, F., de Medeiros Varzielas, I., Merlo, L., & Morisi, S. (2010). Tri/Bi-maximal lepton mixing and leptogenesis. Nucl. Phys. B, 827(1-2), 34–58.
Abstract: In models with flavour symmetries added to the gauge group of the Standard Model the CP-violating asymmetry necessary for leptogenesis may be related with low-energy parameters. A particular case of interest is when the flavour symmetry produces exact Tri/Bi-maximal lepton mixing leading to a vanishing CP-violating asymmetry. In this paper we present a model-independent discussion that confirms this always occurs for unflavoured leptogenesis in type I see-saw scenarios, noting however that Tri/Bi-maximal mixing does not imply a vanishing asymmetry in general scenarios where there is interplay between type I and other see-saws. We also consider a specific model where the exact Tri/Bi-maximal mixing is lifted by corrections that can be parametrised by a small number of degrees of freedom and analyse in detail the existing link between low and high-energy parameters – focusing on how the deviations from Tri/Bi-maximal are connected to the parameters governing leptogenesis.
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Fernandez Navarro, M., King, S. F., & Vicente, A. (2024). Tri-unification: a separate SU(5) for each fermion family. J. High Energy Phys., 05(5), 130–32pp.
Abstract: In this paper we discuss SU(5)3 with cyclic symmetry as a possible grand unified theory (GUT). The basic idea of such a tri-unification is that there is a separate SU(5) for each fermion family, with the light Higgs doublet(s) arising from the third family SU(5), providing a basis for charged fermion mass hierarchies. SU(5)3 tri-unification reconciles the idea of gauge non-universality with the idea of gauge coupling unification, opening the possibility to build consistent non-universal descriptions of Nature that are valid all the way up to the scale of grand unification. As a concrete example, we propose a grand unified embedding of the tri-hypercharge model \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\text{U}}{\left(1\right)}_{Y}<^>{3}$$\end{document} based on an SU(5)3 framework with cyclic symmetry. We discuss a minimal tri-hypercharge example which can account for all the quark and lepton (including neutrino) masses and mixing parameters. We show that it is possible to unify the many gauge couplings into a single gauge coupling associated with the cyclic SU(5)3 gauge group, by assuming minimal multiplet splitting, together with a set of relatively light colour octet scalars. We also study proton decay in this example, and present the predictions for the proton lifetime in the dominant e+pi 0 channel.
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Beltran, R., Cepedello, R., & Hirsch, M. (2023). Tree-level UV completions for NRSMEFT d=6 and d=7 operators. J. High Energy Phys., 08(8), 31pp.
Abstract: We study ultra-violet completions for operators in standard model effective field theory extended with right-handed neutrinos (NRSMEFT). Using a diagrammatic method, we generate systematically lists of possible tree-level completions involving scalars, fermions or vectors for all operators at d = 6 and d = 7, which contain at least one right-handed neutrino. We compare our lists of possible UV models to the ones found for pure SMEFT. We also discuss how the observation of LNV processes via NRSMEFT operators at the LHC can be related to Majorana neutrino masses of the standard model neutrinos.
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ATLAS Collaboration(Aad, G. et al), Alvarez Piqueras, D., Aparisi Pozo, J. A., Bailey, A. J., Barranco Navarro, L., Cabrera Urban, S., et al. (2020). Transverse momentum and process dependent azimuthal anisotropies in root S-NN=8.16 TeV p plus Pb collisions with the ATLAS detector. Eur. Phys. J. C, 80(1), 73–31pp.
Abstract: The azimuthal anisotropy of charged particles produced in sNN=8.16TeV p+Pb collisions is measured with the ATLAS detector at the LHC. The data correspond to an integrated luminosity of 165 nb-1 that was collected in 2016. Azimuthal anisotropy coefficients, elliptic v2 and triangular v3\, extracted using two-particle correlations with a non-flow template fit procedure, are presented as a function of particle transverse momentum (pT) between 0.5 and 50 GeV. The v2 results are also reported as a function of centrality in three different particle pTintervals. The results are reported from minimum-bias events and jet-triggered events, where two jet pT thresholds are used. The anisotropies for particles with pT less than about 2 GeV are consistent with hydrodynamic flow expectations, while the significant non-zero anisotropies for pT in the range 9-50 GeV are not explained within current theoretical frameworks. In the pTrange 2-9 GeV, the anisotropies are larger in minimum-bias than in jet-triggered events. Possible origins of these effects, such as the changing admixture of particles from hard scattering and the underlying event, are discussed.
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Beltran-Palau, P., Navarro-Salas, J., & Pla, S. (2019). Translational anomaly of chiral fermions in two dimensions. Phys. Rev. D, 99(10), 105008–5pp.
Abstract: It is well known that a quantized two-dimensional Weyl fermion coupled to gravity spoils general covariance and breaks the covariant conservation of the energy-momentum tensor. In this brief article, we point out that the quantum conservation of the momentum can also fail in flat spacetime, provided the Weyl fermion is coupled to a time-varying homogeneous electric field. This signals a quantum anomaly of the space-translation symmetry, which has not been highlighted in the literature so far.
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Tonev, D. et al, & Gadea, A. (2021). Transition probabilities in P-31 and S-31: A test for isospin symmetry. Phys. Lett. B, 821, 136603–6pp.
Abstract: Excited states in the mirror nuclei P-31 and S-31 were populated in the 1p and 1n exit channels of the reaction Ne-20 + C-12, at a beam energy of 33 MeV. The Ne-20 beam was delivered for the first time by the Piave-Alpi accelerator of the Laboratori Nazionali di Legnaro. Angular correlations of coincident gamma-rays and Doppler-shift attenuation lifetime measurements were performed using the multi-detector array GASP in conjunction with the EUCLIDES charged particle detector. In the observed B(E1) strengths, the isoscalar component, amounting to 24% of the isovector one, provides strong evidence for breaking of the isospin symmetry in the A = 31 mass region. Self-consistent beyond mean field calculations using Equation of Motion method based on a chiral potential and including two- and three-body forces reproduce well the experimental B(E1) strengths, reinforcing our conclusion. Coherent mixing from higher-lying states involving the Giant Isovector Monopole Resonance accounts well for the effect observed. The breaking of the isospin symmetry originates from the violation of the charge symmetry of the two- and three-body parts of the potential, only related to the Coulomb interaction.
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