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Bruschini, R., & Gonzalez, P. (2021). Diabatic description of charmoniumlike mesons. II. Mass corrections and strong decay widths. Phys. Rev. D, 103(7), 074009–13pp.
Abstract: From a diabatic bound state approach to J(PC) = 1(--) and (0,1,2)(++) charmoniumlike resonances below 4.1 GeV, formulated in terms of c (c) over bar and closed meson-meson channels, we calculate mass shifts and widths due to open meson-meson channels. This calculation does not involve any new free parameter, so comparison of our predictions with existing data provides a direct test of our approach. Further mass corrections are also estimated and good agreement with the measured masses comes out. As for the calculated widths, overall reasonable, they point out to the need of some refinement of our current bound state approximation for an accurate description of data. These results give additional support to the diabatic approach in QCD as an adequate framework for a complete unified description of conventional and unconventional charmoniumlike resonances. In this respect, the experimental discovery of a predicted 2(++) resonance with a mass around 4 GeV would be of special relevance.
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Navarro-Salas, J., & Pla, S. (2021). (F, G)-summed form of the QED effective action. Phys. Rev. D, 103(8), L081702–7pp.
Abstract: We conjecture that the proper-time series expansion of the one-loop effective Lagrangian of quantum electrodynamics can be summed in all terms containing the field-strength invariants F = 1/4F F-mu nu(mu nu) (x), G = 1/4 (F) over tilde F-mu nu(mu nu) (x), including those also possessing derivatives of the electromagnetic field strength. This partial resummation is exactly encapsulated in a factor with the same form as the Heisenberg-Euler Lagrangian density, except that now the electric and magnetic fields can depend arbitrarily on spacetime coordinates. We provide strong evidence for this conjecture, which is proved to sixth order in the proper time. Furthermore, and as a byproduct, we generate some solvable electromagnetic backgrounds. We also discuss the implications for a generalization of the Schwinger formula for pair production induced by nonconstant electric fields. Finally, we briefly outline the extension of these results in the presence of gravity.
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Bruschini, R., & Gonzalez, P. (2021). Diabatic description of bottomoniumlike mesons. Phys. Rev. D, 103(11), 114016–13pp.
Abstract: We apply the diabatic approach, specially suited for a QCD based study of conventional (quark-antiquark) and unconventional (quark-antiquark + meson-meson) meson states, to the description of hidden-bottom mesons. A spectral analysis of the I = 0, J(++) and 1(--) resonances with masses up to about 10.8 GeV is carried out. Masses and widths of all the experimentally known resonances, including conventional and unconventional states, can be well reproduced. In particular, we predict a significant B (B) over bar* component in Upsilon(10580). We also predict the existence of a not yet discovered unconventional 1(++) narrow state, with a significant B-s(B) over bar (s)* content making it to decay into Upsilon(1S)phi, whose experimental discovery would provide definite support to our theoretical analysis.
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Escribano, P., Terol-Calvo, J., & Vicente, A. (2021). (g-2)(e,mu) in an extended inverse type-III seesaw model. Phys. Rev. D, 103(11), 115018–17pp.
Abstract: There has been a longstanding discrepancy between the experimental measurements of the electron and muon anomalous magnetic moments and their predicted values in the Standard Model. This is particularly relevant in the case of the muon g – 2, which has attracted a remarkable interest in the community after the long-awaited announcement of the first results by the Muon g – 2 collaboration at Fermilab, which confirms a previous measurement by the E821 experiment at Brookhaven and enlarges the statistical significance of the discrepancy, now at 4.2 sigma. In this paper we consider an extension of the inverse type-III seesaw with a pair of vectorlike leptons that induces masses for neutrinos at the electroweak scale and show that one can accommodate the electron and muon anomalous magnetic moments, while being compatible with all relevant experimental constraints.
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Ferreiro, A., Nadal-Gisbert, S., & Navarro-Salas, J. (2021). Renormalization, running couplings, and decoupling for the Yukawa model in a curved spacetime. Phys. Rev. D, 104(2), 025003–8pp.
Abstract: The decoupling of heavy fields as required by the Appelquist-Carazzone theorem plays a fundamental role in the construction of any effective field theory. However, it is not a trivial task to implement a renormalization prescription that produces the expected decoupling of massive fields, and it is even more difficult in curved spacetime. Focused on this idea, we consider the renormalization of the one-loop effective action for the Yukawa interaction with a background scalar field in curved space. We compute the beta functions within a generalized DeWitt-Schwinger subtraction procedure and discuss the decoupling in the running of the coupling constants. For the case of a quantized scalar field, all the beta function exhibit decoupling, including also the gravitational ones. For a quantized Dirac field, decoupling appears almost for all the beta functions. We obtain the anomalous result that the mass of the background scalar field does not decouple.
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Chala, M., & Titov, A. (2021). Neutrino masses in the Standard Model effective field theory. Phys. Rev. D, 104(3), 035002–8pp.
Abstract: We compute the leading-logarithmic correction to the neutrino mass matrix in the Standard Model effective field theory (SMEFT) to dimension seven. In the limit of negligible lepton and down-type quark Yukawa couplings, it receives contributions from the Weinberg dimension-five operator as well as from 11 dimension-six and five dimension-seven independent interactions. Two of the main implications we derive from this result are the following. First, we find dimension-seven operators which, despite violating lepton number, do not renormalize neutrino masses at one loop. And second, we demonstrate that the presence of dimension-six operators around the TeV scale can modify the Standard Model prediction by up to O(50%). Our result comprises also one step forward towards the renormalization of the SMEFT to order v(3)/Lambda(3).
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Martinez-Mirave, P., Molina Sedgwick, S., & Tortola, M. (2022). Nonstandard interactions from the future neutrino solar sector. Phys. Rev. D, 105(3), 035004–14pp.
Abstract: The next-generation neutrino experiment JUNO will determine the solar oscillation parameters- sin(2) theta(12) and Delta m(21)(2)-with great accuracy, in addition to measuring sin(2)theta(13), Delta m(31)(2), and the mass ordering. In parallel, the continued study of solar neutrinos at Hyper-Kamiokande will provide complementary measurements in the solar sector. In this paper, we address the expected sensitivity to nonuniversal and flavor-changing nonstandard interactions (NSI) with d-type quarks from the combination of these two future neutrino experiments. We also show the robustness of their measurements of the solar parameters sin(2)theta(12) and Delta m(2)(1)(2) in the presence of NSI. We study the impact of the exact experimental configuration of the Hyper-Kamiokande detector, and conclude it is of little relevance in this scenario. Finally, we find that the LMA-D solution is expected to be present if no additional input from nonoscillation experiments is considered.
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Bruschini, R., & Gonzalez, P. (2021). Coupled-channel meson-meson scattering in the diabatic framework. Phys. Rev. D, 104(7), 074025–16pp.
Abstract: We apply the diabatic framework, a QCD-based formalism for the unified study of quarkoniumlike systems in terms of heavy quark-antiquark and open-flavor meson-meson components, to the description of coupled-channel meson-meson scattering. For this purpose, we first introduce a numerical scheme to find the solutions of the diabatic Schrodinger equation for energies in the continuum, then we derive a general formula for calculating the meson-meson scattering amplitudes from these solutions. We thus obtain a completely nonperturbative procedure for the calculation of open-flavor meson-meson scattering cross sections from the diabatic potential, which is directly connected to lattice QCD calculations. A comprehensive analysis of various elastic cross sections for open-charm and open-bottom meson-meson pairs is performed in a wide range of the center-of-mass energies. The relevant structures are identified, showing a spectrum of quasiconventional and unconventional quarkoniumlike states. In addition to the customary Breit-Wigner peaks, we obtain nontrivial structures such as threshold cusps and minimums. Finally, our results are compared with existing data and with results from our previous bound-state-based analysis, finding full compatibility with both.
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Bruschini, R., & Gonzalez, P. (2022). Is chi(c1)(3872) generated from string breaking? Phys. Rev. D, 105(5), 054028–6pp.
Abstract: We show, from a diabatic analysis of lattice results for string breaking, that mixing of Q (Q) over bar with open-flavor meson-meson configurations may be expressed through a mixing potential which is order 1/m(Q). A relation between the minimum string breaking energy gap and the string tension comes out naturally. Using this relation, and matching the energy gap for b (b) over bar with lattice QCD data, we study the mixing in the c (c) over bar case without any additional parameter. A 1(++) bound state very close below the D-0(D) over bar*(0) threshold, in perfect correspondence with chi(c1)(3872), is predicted.
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Alvarado, F., & Alvarez-Ruso, L. (2022). Light-quark mass dependence of the nucleon axial charge and pion-nucleon scattering phenomenology. Phys. Rev. D, 105(7), 074001–13pp.
Abstract: The light-quark mass dependence of the nucleon axial isovector charge (gA) has been studied up to nextto-next-to-leading order, O(p4), in relativistic chiral perturbation theory using extended-on-mass-shell renormalization, without and with explicit Delta(1232) degrees of freedom. We show that in the Delta-less case, at this order, the flat trend of gA(MN) exhibited by state-of-the-art lattice QCD (LQCD) results cannot be reproduced using low energy constants extracted from pion-nucleon elastic and inelastic scattering. A satisfactory description of these LQCD data is only achieved in the theory with Delta. From this fit, we report gA(MN(phys)) = 1.260 1 0.012, close to the experimental result, and d16 = -0.88 1 0.88 GeV-2, in agreement with its empirical value. The large uncertainties are of theoretical origin, reflecting the difference between O(p3) and O(p4) that still persists at large MN in presence of the Delta.
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