Nieves, J., & Pavao, R. (2020). Nature of the lowest-lying odd parity charmed baryon Lambda(c)(2595) and Lambda(c)(2625) resonances. Phys. Rev. D, 101(1), 014018–17pp.
Abstract: We study the structure of the Lambda(c) (2595) and Lambda(c) (2625) resonances in the framework of an effective field theory consistent with heavy quark spin and chiral symmetries, which incorporates the interplay between Sigma(()(c)*() )pi – ND(*()) baryon-meson degrees of freedom (d.o.f.) and bare P-wave c (u) over bard quark-model states. We show that these two resonances are not heavy quark spin symmetry partners. The J(P) = 3/2(-) Lambda(c) (2625) should be viewed mostly as a dressed three-quark state, whose origin is determined by a bare state, predicted to lie very close to the mass of the resonance. The J(P) = 1/2(-) Lambda(c) (2595) seems to have, however, a predominant molecular structure. This is because it is either the result of the chiral Sigma(c)pi interaction, whose threshold is located much closer than the mass of the bare three-quark state, or because the light d.o.f. in its inner structure are coupled to the unnatural 0(-) quantum numbers. We show that both situations can occur depending on the renormalization procedure used. We find some additional states, but the classification of the spectrum in terms of heavy quark spin symmetry is difficult, despite having used interactions that respect this symmetry. This is because the bare quark-model state and the Sigma(c)pi threshold are located extraordinarily close to the Lambda(c) (2625) and Lambda(c) (2595), respectively, and hence they play totally different roles in each sector.
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Bruschini, R., & Gonzalez, P. (2020). Radiative decays in charmonium beyond the p/m approximation. Phys. Rev. D, 101(1), 014027–16pp.
Abstract: We analyze the theoretical description of radiative decays in charmonium. We use an elementary emission decay model to build the most general electromagnetic transition operator. We show that accurate results for the widths can be obtained from a simple quark potential model reasonably fitting the spectroscopy if the complete form of the operator is used instead of its standard p/m approximation and the experimental masses are properly implemented in the calculation.
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T2K Collaboration(Abe, K. et al), Antonova, M., Cervera-Villanueva, A., Fernandez, P., Izmaylov, A., & Novella, P. (2020). First measurement of the charged current (nu)over-bar(mu) double differential cross section on a water target without( )pions in the final state. Phys. Rev. D, 102(1), 012007–16pp.
Abstract: This paper reports the first differential measurement of the charged-current (nu) over bar (mu) interaction cross section on water with no pions in the final state. The unfolded flux-averaged measurement using the T2K off-axis near detector is given in double-differential bins of mu(+) momentum and angle. The integrated cross section in a restricted phase space is sigma = (1.11 +/- 0.18) x 10(-38) cm(2) per water molecule. Comparisons with several nuclear models are also presented.
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Dias, A. G., Leite, J., Sanchez-Vega, B. L., & Vieira, W. C. (2020). Dynamical symmetry breaking and fermion mass hierarchy in the scale-invariant 3-3-1 model. Phys. Rev. D, 102(1), 015021–18pp.
Abstract: We propose an extension of the Standard Model (SM) based on the SU(3)(C) circle times SU(3)(L) circle times U(1)(X) (3-3-1) gauge symmetry and scale invariance. Maintaining the main features of the so-called 3-3-1 models, such as the cancellation of gauge anomalies related to the number of chiral fermion generations, this model exhibits a very compact scalar sector. Only two scalar triplets and one singlet are necessary and sufficient to break the symmetries dynamically via the Coleman-Weinberg mechanism. With the introduction of an Abelian discrete symmetry and assuming a natural hierarchy among the vacuum expectation values of the neutral scalar fields, we show that all particles in the model can get phenomenologically consistent masses. In particular, most of the standard fermion masses are generated via a seesaw mechanism involving some extra heavy fermions introduced for consistency. This mechanism provides a partial solution for the fermion mass hierarchy problem in the SM. Furthermore, the simplicity of the scalar sector allows us to analytically find the conditions for the potential stability up to one-loop level and show how they can be easily satisfied. Some of the new particles, such as the scalars H, H-+/- and all the non-SMvector bosons, are predicted to get masses around the TeV scale and, therefore, could be produced at the high-luminosity LHC. Finally, we show that the model features a residual symmetry, which leads to the stability of a heavy neutral particle; the latter is expected to show up in experiments as missing energy.
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Leite, J., Morales, A., Valle, J. W. F., & Vaquera-Araujo, C. A. (2020). Dark matter stability from Dirac neutrinos in scotogenic 3-3-1-1 theory. Phys. Rev. D, 102(1), 015022–11pp.
Abstract: We propose the simplest TeV-scale scotogenic extension of the original 3-3-1 theory, where dark matter stability is linked to the Dirac nature of neutrinos, which results from an unbroken B – L gauge symmetry. The new gauge bosons get masses through the interplay of spontaneous symmetry breaking a la Higgs and the Stueckelberg mechanism.
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