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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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2016). Measurement of angular asymmetries in the decays B -> K*l(+) l(+). Phys. Rev. D, 93(5), 052015–16pp.
Abstract: We study the lepton forward-backward asymmetry AFB and the longitudinal K* polarization F-L, as well as an observable P-2 derived from them, in the rare decays B -> K*l(+)l(-), where l(+)l(-) is either e(+)e(-) or mu(+)mu(-), using the full sample of 471 million B (B) over bar events collected at the Upsilon(4S) resonance with the BABAR, detector at the PEP-II e(+)e(-) collider. We separately fit and report results for the K*(0)(892)l(+)l(-) and K*(+)(892) l(+)l(-) final states, as well as their combination K*l(+)l(-), in five disjoint dilepton mass-squared bins. An angular analysis of B+ -> K*(+)l(+)l(-) decays is presented here for the first time.
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Lu, J. X., Wang, E., Xie, J. J., Geng, L. S., & Oset, E. (2016). Lambda(b) -> J/psi K-0 Lambda reaction and a hidden-charm pentaquark state with strangeness. Phys. Rev. D, 93(9), 094009–11pp.
Abstract: We study the Lambda(b) -> J/psi K-0 Lambda reaction considering both the K-0 Lambda interaction with its coupled channels and the J/psi Lambda interaction. The latter is described by taking into account the fact that there are predictions for a hidden-charm state with strangeness that couples to J/psi Lambda By using the coupling of the resonance to J/psi Lambda from these predictions, we show that a neat peak can be observed in the J/psi Lambda invariant mass distribution, rather stable under changes of unknown magnitudes. In some cases, one finds a dip structure associated to that state, but a signal of the state shows up in the J/psi Lambda spectrum.
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Sakai, S., Liang, W. H., Toledo, G., & Oset, E. (2020). J/psi -> gamma pi pi, gamma pi(0)eta reactions and the f(0)(980) and a(0)(980) resonances. Phys. Rev. D, 101(1), 014005–9pp.
Abstract: We study the J/psi -> gamma pi(+)pi(-), gamma pi(0)eta reactions from the perspective that they come from the J/psi -> phi(omega)pi(+)pi(-), rho(0)pi(0)eta reactions, where the rho(0), psi, and phi get converted into a photon via vector meson dominance. Using models successfully used previously to study the J/psi -> omega(phi)pi pi reactions, we make determinations of the invariant mass distributions for pi(+)pi(-) in the regions of the f(0)(500), f(0)(980), and for pi(0)eta in the region of the a(0)(980). The integrated differential widths lead to branching ratios below present upper bounds, but they are sufficiently large for future check in updated facilities.
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Ikeno, N., Bayar, M., & Oset, E. (2023). Molecular states of D*D*Kbar* nature. Phys. Rev. D, 107(3), 034006–12pp.
Abstract: We study the interaction of two D* and a over bar K* by using the fixed center approximation to the Faddeev equations to search for bound states of the three-body system. Since the D*D* interaction is attractive and gives a bound state, and so is the case of the D* over bar K* interaction, where the JP = 0+ bound state is identified with the X0(2900), the D*D* over bar K* system leads to manifestly exotic bound states with ccs open quarks. We obtain bound states of isospin I = 1=2, negative parity and total spin J = 0, 1, 2. For J = 0 we obtain one state, and for J = 1, 2 we obtain two states in each case. The binding energies range from 56 to 152 MeV and the widths from 80 to 100 MeV.
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Dai, L. R., Oset, E., Feijoo, A., Molina, R., Roca, L., Martinez Torres, A., et al. (2022). Masses and widths of the exotic molecular B-(s)(()*B-)((s))(*()) states. Phys. Rev. D, 105(7), 074017–11pp.
Abstract: We study the interaction of the doubly bottom systems BB, B*B, BsB, B-s*B, B*B*, B*B-S, B*B-s*, BsBs, BsBs*, B-s*B-s* by means of vector meson exchange with Lagrangians from an extension of the local hidden gauge approach. The full s-wave scattering matrix is obtained implementing unitarity in coupled channels by means of the Bethe-Salpeter equation. We find poles below the channel thresholds for the attractively interacting channels B*B in I = 0, B-s*B – B*B-s in I = 1/2, B* B* in I = 0, and B-s*B* in I = 1/2, all of them with J(P) = 1(+). For these cases the widths are evaluated identifying the dominant source of imaginary part. We find binding energies of the order of 10-20 MeV, and the widths vary much from one system to the other: of the order of 10-100 eV for the B* B system and B-s*B – B* B-s, about 6 MeV for the B*B* system and of the order of 0.5 MeV for the B-s*B* system.
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Wang, W. F., Feijoo, A., Song, J., & Oset, E. (2022). Molecular Omega(ce), Omega(bb), and Omega(bc) states. Phys. Rev. D, 106(11), 116004–14pp.
Abstract: We study the interaction of meson-baryon coupled channels carrying quantum numbers of a Omega(ce), Omega(bb), and Omega(bc) presently under investigation by the LHCb Collaboration. The interaction is obtained from an extension of the local hidden gauge approach to the heavy quark sector that has proved to provide accurate results compared to experiment in the case of Omega(c), Xi(c) states and pentaquarks, P-c and P-cs. We obtain many bound states, with small decay widths within the space of the chosen coupled channels. The spin-parity of the states are J(P) = 1/2(-) for coupled channels of pseudoscalar-baryon (1/2(+)), J(P) = 3/2(-) for the case of pseudoscalar-baryon (3/2(+)), J(P) = 1/2(-), 3/2(-) for the case of vector-baryon (1/2(+)) and J(P) = 1/2(-), 3/2(-). 5/2(-) for the vector- baryon (3/2(+)) channels. We look for poles of the states and evaluate the couplings to the different channels. The couplings obtained for the open channels can serve as a guide to see in which reaction the obtained states are more likely to be observed.
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