Yamagata-Sekihara, J., Nieves, J., & Oset, E. (2011). Couplings in coupled channels versus wave functions in the case of resonances: Application to the two A(1405) states. Phys. Rev. D, 83(1), 014003–15pp.
Abstract: In this paper we develop a formalism to evaluate wave functions in momentum and coordinate space for the resonant states dynamically generated in a unitary coupled channel approach. The on-shell approach for the scattering matrix, commonly used, is also obtained in quantum mechanics with a separable potential, which allows one to write wave functions in a trivial way. We develop useful relationships among the couplings of the dynamically generated resonances to the different channels and the wave functions at the origin. The formalism provides an intuitive picture of the resonances in the coupled channel approach, as bound states of one bound channel, which decays into open ones. It also provides an insight and practical rules for evaluating couplings of the resonances to external sources and how to deal with final state interaction in production processes. As an application of the formalism we evaluate the wave functions of the two A(1405) states in the pi Sigma, (K) over barN, and other coupled channels. It also offers a practical way to study three-body systems when two of them cluster into a resonance.
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Xie, J. J., & Oset, E. (2014). (B)over-bar(0) and (B)over-bar(s)(0) decays into J/psi and f(0)(1370), f(0)(1710), f(2)(1270), f(2)'(1525), K-2*(1430). Phys. Rev. D, 90(9), 094006–7pp.
Abstract: We make predictions for the ratios of branching fractions of (B) over bar (0) and (B) over bar (0)(s) decays into J/psi and the scalar mesons f(0)(1370), f(0)(1710) or tensor mesons f(2)(1270), f(2)'(1525), K-2*(1430). The theoretical approach is based on results of chiral unitary theory where these resonances are shown to be generated from the vector meson-vector meson interaction. Eight independent ratios can be predicted, and comparison is made with the recent data on (B) over bar (0)(s) decay into J/psi f(2)'(1525) versus the (B) over bar (0)(s) decay into J/psi f(2)(1270).
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Xie, J. J., Geng, L. S., & Oset, E. (2017). f(2)(1810) as a triangle singularity. Phys. Rev. D, 95(3), 034004–6pp.
Abstract: We perform calculations showing that a source producing K*K* in J = 2 and L = 0 gives rise to a triangle singularity at 1810 MeV with a width of about 200 MeV from the mechanism K*-> pi K and then KK* merging into the a alpha(1)(1260) resonance. We suggest that this is the origin of the present f(2)(1810) resonance and propose to look at the pa pi alpha(1)(1260) mode in several reactions to clarify the issue.
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Xiao, C. W., Nieves, J., & Oset, E. (2013). Combining heavy quark spin and local hidden gauge symmetries in the dynamical generation of hidden charm baryons. Phys. Rev. D, 88(5), 056012–20pp.
Abstract: We present a coupled channel unitary approach to obtain states dynamically generated from the meson-baryon interaction with hidden charm, using constraints of heavy quark spin symmetry. As a basis of states, we use (D) over barB, (D) over bar *B states, with B baryon charmed states belonging to the 20 representations of SU(4) with J(P) = 1/2(+), 3/2(+). In addition we also include the eta N-c and J/psi N states. The inclusion of these coupled channels is demanded by heavy quark spin symmetry, since in the large m(Q) limit the D and D* states are degenerate and are obtained from each other by means of a spin rotation, under which QCD is invariant. The novelty in the work is that we use dynamics from the extrapolation of the local hidden gauge model to SU(4), and we show that this dynamics fully respects the constraints of heavy quark spin symmetry. With the full space of states demanded by the heavy quark spin symmetry and the dynamics of the local hidden gauge, we look for states dynamically generated and find four basic states that are bound, corresponding to (D) over bar Sigma(c), (D) over bar Sigma(c)*, (D) over bar*Sigma(c) and (D) over bar*Sigma*(c) decaying mostly into eta N-c and J/psi N. All the states appear in isospin I = 1/2, and we find no bound states or resonances in I = 3/2. The (D) over bar Sigma(c) state appears in J = 1/2 and the (D) over bar Sigma*(c) in J = 3/2; the (D) over bar*Sigma(c) appears nearly degenerate in J = 1/2, 3/2 and the (D) over bar*Sigma*(c) appears nearly degenerate in J = 1/2, 3/2, 5/2, with the peculiarity that in J = 5/2 the state has zero width in the space of states chosen. All the states are bound with about 50 MeV with respect to the corresponding (D) over barB thresholds, and the width, except for the J = 5/2 state, is also of the same order of magnitude. Finally, we discuss the uncertainties stemming from the expected breaking of SU(4) and the heavy quark spin symmetry.
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Xiao, C. W., Nieves, J., & Oset, E. (2019). Heavy quark spin symmetric molecular states from (D)over-bar(()*())Sigma(()(c)*()) and other coupled channels in the light of the recent LHCb pentaquarks. Phys. Rev. D, 100(1), 014021–6pp.
Abstract: We consider the (D) over bar (()*())Sigma(()(c)*()) states, together with J/psi N and other coupled channels, and take an interaction consistent with heavy quark spin symmetry, with the dynamical input obtained from an extension of the local hidden gauge approach. By fitting only one parameter to the recent three pentaquark states reported by the LHCb Collaboration, we can reproduce the three of them in base to the mass and the width, providing for them the quantum numbers and approximate molecular structure as 1/2(-) (D) over bar Sigma(c), 1/2(-) (D) over bar*Sigma(c), and 3/2(-) (D) over bar*Sigma(c), and the isospin I = 1/2. We find another state around 4374 MeV, of the 3/2(-) (D) over bar Sigma(c)* structure, for which indications appear in the experimental spectrum. Two other near degenerate states of a 1/2(-) (D) over bar*Sigma(c)* and 3/2(-) (D) over bar*Sigma(c)* nature are also found around 4520 MeV, which although less clear, are not incompatible with the observed spectrum. In addition, a 5/2(-) (D) over bar*Sigma(c)* state at the same energy appears, which however does not couple to J/psi p in an S wave, and hence, it is not expected to show up in the LHCb experiment.
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Xiao, C. W., Dias, J. M., Dai, L. R., Liang, W. H., & Oset, E. (2024). Triangle singularity in the J/ψ → ϕ π+ a−0(π−η) ,ϕ π− a+0(π+η) decays. Phys. Rev. D, 109(7), 074033–11pp.
Abstract: We study the J= psi -> phi pi + a 0 ( 980 ) – ( a – 0 -> pi – eta ) decay, evaluating the double mass distribution in terms of the pi – eta and pi + a – 0 invariant masses. We show that the pi – eta mass distribution exhibits the typical cusp structure of the a 0 ( 980 ) seen in recent high statistics experiments, and the pi + a – 0 spectrum shows clearly a peak around M inv ( pi + a – 0 ) = 1420 MeV, corresponding to a triangle singularity. When integrating over the two invariant masses we find a branching ratio for this decay of the order of 10 – 5 , which is easily accessible in present laboratories. We also call attention to the fact that the signal obtained is compatible with a bump experimentally observed in the eta pi + pi – mass distribution in the J= psi -> phi eta pi + pi – decay and encourage further analysis to extract from there the phi pi + a – 0 and phi pi – a + 0 decay modes.
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Xiao, C. W., Bayar, M., & Oset, E. (2011). NDK, (K)over-barDN, and ND(K)over-bar molecules. Phys. Rev. D, 84(3), 034037–8pp.
Abstract: We investigate theoretically baryon systems made of three hadrons which contain one nucleon and one D meson, and in addition another meson, (D) over tilde, K, or (K) over tilde. The systems are studied using the fixed center approximation to the Faddeev equations. The study is made assuming scattering of a K or a (K) over tilde on a DN cluster, which is known to generate the Lambda(c)(2595), or the scattering of a nucleon on the D (D) over tilde cluster, which has been shown to generate a hidden charm resonance named X(3700). We also investigate the configuration of scattering of N on the KD cluster, which is known to generate the D*(s0)(2317). In all cases we find bound states, with the NDK system, of exotic nature, more bound than the (K) over tilde DN.
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Xiao, C. W., Bayar, M., & Oset, E. (2012). Prediction of D*-multi-rho states. Phys. Rev. D, 86(9), 094019–10pp.
Abstract: We present a study of the many-body interaction between a D* and multi-rho. We use an extrapolation to SU(4) of the hidden gauge formalism, which produced dynamically the resonances f(2)(1270) in the rho rho interaction and D-2* (2460) in the rho D* interaction. We then let a third particle, rho, D*, or a resonance, collide with them, evaluating the scattering amplitudes in terms of the fixed center approximation of the Faddeev equations. We find several clear resonant structures above 2800 MeV in the multibody scattering amplitudes. They would correspond to new charmed resonances, D-3*, D-4*, D-5*, and D-6*, which are not yet listed in the Particle Data Group, which would be analogous to the rho(3)(1690), f(4)(2050), rho(5)(2350), f(6)(2510) and K-3*(1780), K-4*(2045), K-5*(2380) described before as multi-rho and K*-multi-rho states, respectively.
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Xiao, C. W. (2015). States generated in the K-multi-rho interactions. Phys. Rev. D, 92(5), 054011–16pp.
Abstract: In the present work, we use three-body interaction formalism to investigate the K-multi-rho interactions. First, we reproduce the resonances f(2)(1270) and K-1(1270) in the rho rho and rho K two-body interactions, respectively, as the clusters of the fixed-center approximation. Then, we study the three-body K-rho rho(f(2)) and rho-rho K(K-1) interactions with the fixed-center approximation of the Faddeev equations. Furthermore, we extrapolate the formalism to study the four-body, five-body, and six-body systems containing one K meson and multiple rho mesons. In our research, without introducing any free parameters, we generate the K-2(1770) state in the three-body interaction with the mass of 1707 MeV and a width about 113 MeV, which are consistent with the experiments. We also find a clear resonant structure in our results of the five-body interaction, with a mass 2505 MeV and a width about 32 MeV or more, which is associated with the K-4(2500) state, where we obtain consistent results with the experimental findings. Furthermore, we predict some new states in the other many-body interactions, K-3(2080), K-5(2670) (isospin I = 1/2), and K-4(2640) (isospin I = 3/2), with uncertainties.
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XENON100 Collaboration(Aprile, E. et al), & Orrigo, S. E. A. (2014). First axion results from the XENON100 experiment. Phys. Rev. D, 90(6), 062009–7pp.
Abstract: We present the first results of searches for axions and axionlike particles with the XENON100 experiment. The axion-electron coupling constant, g(Ae), has been probed by exploiting the axioelectric effect in liquid xenon. A profile likelihood analysis of 224.6 live days x 34-kg exposure has shown no evidence for a signal. By rejecting g(Ae) larger than 7.7 x 10(-12) (90% C. L.) in the solar axion search, we set the best limit to date on this coupling. In the frame of the DFSZ and KSVZ models, we exclude QCD axions heavier than 0.3 and 80 eV/c(2), respectively. For axionlike particles, under the assumption that they constitute the whole abundance of dark matter in our galaxy, we constrain gAe to be lower than 1 x 10(-12) (90% C.L.) for masses between 5 and 10 keV/c(2).
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