Câmara, H. B., Joaquim, F. R., & Valle, J. W. F. (2023). Dark-sector seeded solution to the strong CP problem. Phys. Rev. D, 108(9), 095003–6pp.
Abstract: We propose a novel realization of the Nelson-Barr mechanism “seeded” by a dark sector containing scalars and vectorlike quarks. Charge parity (CP) and a Z8 symmetry are spontaneously broken by the complex vacuum expectation value of a singlet scalar, leaving a residual Z2 symmetry that stabilizes dark matter (DM). A complex Cabibbo-Kobayashi-Maskawa matrix arises via one-loop corrections to the quark mass matrix mediated by the dark sector. In contrast with other proposals where nonzero contributions to the strong CP phase arise at the one-loop level, in our case this occurs only at two loops, enhancing naturalness. Our scenario also provides a viable weakly interacting massive particle scalar DM candidate.
|
Maiezza, A., & Nemevsek, M. (2014). Strong P invariance, neutron electric dipole moment, and minimal left-right parity at LHC. Phys. Rev. D, 90(9), 095002–10pp.
Abstract: In the minimal left-right model the choice of left-right symmetry is twofold: either generalized parity P or charge conjugation C. In the minimal model with spontaneously broken strict P, a large tree-level contribution to strong CP violation can be computed in terms of the spontaneous phase alpha. Searches for the neutron electric dipole moments then constrain the size of alpha. Following the latest update on indirect CP violation in the kaon sector, a bound on W-R mass at 20 TeV is set. Possible ways out of this bound require a further hypothesis, either a relaxation mechanism or explicit breaking of P. To this end, the chiral loop of the neutron electric dipole moment at next-to-leading order is recomputed and provides an estimate of the weak contribution. Combining this constraint with other CP-violating observables in the kaon sector allows for M-WR greater than or similar to 3 TeV. On the other hand, C symmetry is free from such constraints, leaving the right-handed scale within the experimental reach.
|
Bonilla, C., Modak, T., Srivastava, R., & Valle, J. W. F. (2018). U(1)(B3-3L2) gauge symmetry as a simple description of b -> s anomalies. Phys. Rev. D, 98(9), 095002–11pp.
Abstract: We present a simple U(1)(B3-3L2) gauge standard model extension that can easily account for the anomalies in R(K) and R(K*) reported by LHCb. The model is economical in its setup and particle content. Among the standard model fermions, only the third generation quark family and the second generation leptons transform nontrivially under the new U(1)(B3-3L2) symmetry. This leads to lepton nonuniversality and flavor changing neutral currents involving the second and third quark families. We discuss the relevant experimental constraints and some implications.
|
Huang, F., Sanz, V., Shu, J., & Xue, X. (2021). LIGO as a probe of dark sectors. Phys. Rev. D, 104(10), 095001–9pp.
Abstract: We show how current LIGO data is able to probe interesting theories beyond the Standard Model, particularly dark sectors where a dark Higgs boson triggers symmetry breaking via a first-order phase transition. We use publicly available LIGO O2 data to illustrate how these sectors, even if disconnected from the Standard Model, can be probed by gravitational wave detectors. We link the LIGO measurements with the model content and mass scale of the dark sector, finding that current O2 data are testing a broad set of scenarios that can be mapped into many different types of dark-sector models where the breaking of SU(N) theories with Nf fermions is triggered by a dark Higgs boson at scales ? similar or equal to 108-109 GeV with reasonable parameters for the scalar potential.
|
Pich, A., Platschorre, A., & Reig, M. (2023). Electroweak mass difference of mesons. Phys. Rev. D, 108(9), 094044–6pp.
Abstract: We consider electroweak gauge boson corrections to the masses of pseudoscalar mesons to next to leading order in alpha s and 1/NC. The pion mass shift induced by the Z boson is shown to be m pi +/- – m pi 0 = -0.00201(12) MeV. While being small compared to the electromagnetic mass shift, the prediction lies about a factor of similar to 4 above the precision of the current experimental measurement and a factor O(10) below the precision of current lattice calculations. This motivates future implementations of these electroweak gauge boson effects on the lattice. Finally, we consider beyond standard model contributions to the pion mass difference.
|
Aguilar, A. C., Ferreira, M. N., Figueiredo, C. T., & Papavassiliou, J. (2019). Gluon mass scale through nonlinearities and vertex interplay. Phys. Rev. D, 100(9), 094039–19pp.
Abstract: We present a novel analysis of the gluon gap equation, where its full nonlinear structure is duly taken into account. In particular, while in previous treatments the linearization of this homogeneous integral equation introduced an indeterminacy in the scale of the corresponding mass, the current approach determines it uniquely, once the value of the gauge coupling at a given renormalization point is used as input. A crucial ingredient for this construction is the “kinetic term” of the gluon propagator, whose form is not obtained from the complicated equation governing its evolution, but is rather approximated by suitable initial Ansatze, which are subsequently improved by means of a systematic iterative procedure. The multiplicative renormalization of the central equation is carried out following an approximate method, which is extensively employed in the studies of the standard quark gap equation. This approach amounts to the effective substitution of the vertex renormalization constants by kinematically simplified form factors of the three- and four-gluon vertices. The resulting numerical interplay, exemplified by the infrared suppression of the three-gluon vertex and the mild enhancement of the four-gluon vertex, is instrumental for obtaining positive-definite and monotonically decreasing running gluon masses. The resulting gluon propagators, put together from the gluon masses and kinetic terms obtained with this method, match rather accurately the data obtained from large-volume lattice simulations.
|
Fontoura, C. E., Krein, G., Valcarce, A., & Vijande, J. (2019). Production of exotic tetraquarks QQ(q)over-bar (q)over-bar in heavy-ion collisions at the LHC. Phys. Rev. D, 99(9), 094037–8pp.
Abstract: We investigate the production of exotic tetraquarks, QQ (q) over bar (q) over bar T-QQ (Q = c or b and q = u or d), in relativistic heavy-ion collisions using the quark coalescence model. The T-QQ yield is given by the overlap of the density matrix of the constituents in the emission source with the Wigner function of the produced tetraquark. The tetraquark wave function is obtained from exact solutions of the four-body problem using realistic constituent models. The production yields are typically one order of magnitude smaller than previous estimations based on simplified wave functions for the tetraquarks. We also evaluate the consequences of the partial restoration of chiral symmetry at the hadronization temperature on the coalescence probability. Such effects, in addition to increasing the stability of the tetraquarks, lead to an enhancement of the production yields, pointing towards an excellent discovery potential in forthcoming experiments. We discuss further consequences of our findings for the search of exotic tetraquarks in central Pb + Pb collisions at the LHC.
|
Albertus, C., Hernandez, E., & Nieves, J. (2012). Exclusive c -> s, d semileptonic decays of ground-state spin-1/2 and spin-3/2 doubly heavy cb baryons. Phys. Rev. D, 85(9), 094035–21pp.
Abstract: We evaluate exclusive semileptonic decays of ground-state spin-1/2 and spin-3/2 doubly heavy cb baryons driven by a c --> s, d transition at the quark level. We check our results for the form factors against heavy quark spin symmetry constraints obtained in the limit of very large heavy quark masses and near zero recoil. Based on those constraints we make model-independent, though approximate, predictions for ratios of decay widths.
|
Debastiani, V. R., Dias, J. M., Liang, W. H., & Oset, E. (2018). Molecular Omega(c) states generated from coupled meson-baryon channels. Phys. Rev. D, 97(9), 094035–11pp.
Abstract: We have investigated Omega(c) states that are dynamically generated from the meson-baryon interaction. We use an extension of the local hidden gauge to obtain the interaction from the exchange of vector mesons. We show that the dominant terms come from the exchange of light vectors, where the heavy quarks are spectators. This has as a consequence that heavy quark symmetry is preserved for the dominant terms in the (1/m(Q)) counting, and also that the interaction in this case can be obtained from the SU(3) chiral Lagrangians. We show that for a standard value for the cutoff regulating the loop, we obtain two states with J(P) = 1/2(-) and two more with J(P) = 3/2(-), three of them in remarkable agreement with three experimental states in mass and width. We also make predictions at higher energies for states of vector-baryon nature.
|
Carlomagno, J. P., Gomez Dumm, D., Izzo Villafañe, M. F., Noguera, S., & Scoccola, N. N. (2022). Charged pseudoscalar and vector meson masses in strong magnetic fields in an extended NJL model. Phys. Rev. D, 106(9), 094035–17pp.
Abstract: The mass spectrum of pi(+) and rho(+) mesons in the presence of a static uniform magnetic field (B) over right arrow is studied within a two-flavor Nambu-Jona-Lasinio-like model. We improve previous calculations, taking into account the effect of Schwinger phases carried by quark propagators and using an expansion of meson fields in terms of the solutions of the corresponding equations of motion for nonzero B. It is shown that the meson polarization functions are diagonal in this basis. Our numerical results for the rho(+) meson spectrum are found to disfavor the existence of a meson condensate induced by the magnetic field. In the case of the pi(+) meson, pi-rho mixing effects are analyzed for the meson lowest-energy state. The predictions of the model are compared with available lattice QCD results.
|
