Liang, W. H., Bayar, M., & Oset, E. (2017). Lambda(b) -> pi(-)(D-S(-)) Lambda(C)(2595), pi(-)(D-S(-)) Lambda(C)(2625) decays and DN, D*N molecular components. Eur. Phys. J. C, 77(1), 39–9pp.
Abstract: From the perspective that Lambda(C)(2595) and Lambda(C)(2625) are dynamically generated resonances from the DN, D*N interaction and coupled channels, we have evaluated the rates for Lambda(b) -> pi(-)Lambda(C)(2595) and Lambda(b) -> pi(-)Lambda(C)(2625) up to a global unknown factor that allows us to calculate the ratio of rates and compare with experiment, where good agreement is found. Similarly, we can also make predictions for the ratio of rates of the, yet unknown, decays of Lambda(b) -> D-s(-)Lambda(C)(2595) and Lambda(b) -> D-s(-)Lambda(c)(2625) and make estimates for their individual branching fractions.
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Bayar, M., & Debastiani, V. R. (2017). a(0)(980) – f(0)(980) mixing in chi(c1) -> pi(0)f(0)(980) -> pi(0)pi(+)pi(-) and chi(c1) -> pi(0) a(0)(980) -> pi(0)pi(0)eta. Phys. Lett. B, 775, 94–99.
Abstract: We study the isospin breaking in the reactions chi(c1) -> pi(0)pi(+)pi(-) and chi(c1) -> pi(0)pi(0)eta and its relation to the a(0)(980) – f(0)(980) mixing, which was measured by the BESIII Collaboration. We show that the same theoretical model previously developed to study the chi(c1) -> eta pi(+)pi(-) reaction (also measured by BESIII), and further explored in the predictions to the eta(c) -> eta pi(+)pi(-), can be successfully employed in the present study. We assume that the chi(c1) behaves as an SU(3) singlet to find the weight in which trios of pseudoscalars are created, followed by the final state interaction of pairs of mesons to describe how the a(0)(980) and f(0)(980) are dynamically generated, using the chiral unitary approach in coupled channels. The isospin violation is introduced through the use of different masses for the charged and neutral kaons, either in the propagators of pairs of mesons created in the chi(c1) decay, or in the propagators inside the T matrix, constructed through the unitarization of the scattering and transition amplitudes of pairs of pseudoscalar mesons. We find that violating isospin inside the T matrix makes the pi(0)eta -> pi(+)pi(-) amplitude nonzero, which gives an important contribution and also enhances the effect of the K (K) over bar term. We also find that the most important effect in the total amplitude is the isospin breaking inside the T matrix, due to the constructive sum of pi(0)eta -> pi(+)pi(-) and K (K) over bar -> pi(+)pi(-), which is essential to get a good agreement with the experimental measurement of the mixing.
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Bayar, M., Pavao, R., Sakai, S., & Oset, E. (2018). Role of the triangle singularity in Lambda(1405) production in the pi(-) p -> K-0 pi Sigma and pp -> pK(+) pi Sigma processes. Phys. Rev. C, 97(3), 035203–12pp.
Abstract: We have investigated the cross section for the pi(-) p -> K-0 pi Sigma and pp -> pK(+) pi Sigma reactions, paying attention to a mechanism that develops a triangle singularity. The triangle diagram is realized by the decay of a N* to K* Sigma and the K* decay into pi K, and the pi Sigma finally merges into Lambda (1405). The mechanism is expected to produce a peak around 2140 MeV in the K Lambda (1405) invariant mass. We found that a clear peak appears around 2100 MeV in the K Lambda (1405) invariant mass, which is about 40 MeV lower than the expectation, and that is due to the resonance peak of a N* resonance which plays a crucial role in the K* Sigma production. The mechanism studied produces the peak of the Lambda (1405) around or below 1400 MeV, as is seen in the pp -> pK(+) pi Sigma HADES experiment.
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Ikeno, N., Bayar, M., & Oset, E. (2018). Semileptonic decay of B-c(-) into X (3930), X (3940), X (4160). Eur. Phys. J. C, 78(5), 429–7pp.
Abstract: We study the semileptonic decay of B-c(-) meson into & Unknown;l(-) and the isospin zero X (3930) (2(++)), X(3940) (0(++)), X (4160) (2(++)) resonances. We look at the reaction from the perspective that these resonaces appear as dynamically generated from the vector-vector interaction in the charm sector, and couple strongly to D*& Unknown;D* and D-s*& Unknown;D-s*. We also look into the B-c(-) -> & Unknown;(l)l(-) D*& Unknown;* and B-c(-) -> & Unknown;(l)l(-) D-s*& Unknown;(s)* reactions close to threshold and relate the D*& Unknown;* and D-s*& Unknown;(s)* mass distribution to the rate of production of the X resonances.
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Yu, Q. X., Liang, W. H., Bayar, M., & Oset, E. (2019). Line shape and D-(*())(D)over-bar(()*()) probabilities of psi(3770) from the e(+) e(-) -> D(D)over-bar reaction. Phys. Rev. D, 99(7), 076002–17pp.
Abstract: We have performed a calculation of the D (D) over bar, D (D) over bar*, D*(D) over bar, D*(D) over bar* components in the wave function of the psi(3770). For this we make use of the P-3(0) model to find the coupling of psi(3770) to these components, that with an elaborate angular momentum algebra can be obtained with only one parameter. Then we use data for the e(+)e(-) -> D (D) over bar reaction, from where we determine a form factor needed in the theoretical framework, as well as other parameters needed to evaluate the meson-meson self-energy of the psi(3770). Once this is done we determine the Z probability to still have a vector core and the probability to have the different meson components. We find Z about 80%-85%, and the individual meson-meson components are rather small, providing new empirical information to support the largely q (q) over bar component of vector mesons, and the psi(3770) in particular. A discussion is done of the meaning of the terms obtained for the case of the open channels where the concept of probability cannot be strictly used.
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Bayar, M., Ikeno, N., & Oset, E. (2020). Analysis of the psi (4040) and psi (4160) decay into D-(*()) (D)over-bar(()*()), D-s(()*()) (D)over-bar(s)(()*()). Eur. Phys. J. C, 80(3), 222–9pp.
Abstract: We have performed an analysis of the e+e--> D(*) data in the region of the psi(4040) and psi(4160) resonances which have a substantial overlap and require special care. By using the P-3(0) model to relate the different D(*)(D) over bar(*) production modes, we make predictions for production of these channels and compare with experiment and other theoretical approaches. As a side effect we find that these resonances qualify largely as c (c) over bar states and theweight of the meson-meson components in the wave function is very small.
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Ikeno, N., Bayar, M., & Oset, E. (2021). Combined theoretical study of the D+ -> pi(+) eta eta and D+ -> pi(+)pi(0) eta reactions. Eur. Phys. J. C, 81(4), 377–10pp.
Abstract: We study the D+ -> pi(+) eta eta and D+ -> pi(+)pi(0) eta reactions, which are single Cabibbo suppressed and can proceed both through internal and external emission. The primary mechanisms at quark level are considered, followed by hadronization to produce three mesons in the D+ decay, and after that the final state interaction of these mesons leads to the production of the a(0)(980) resonance, seen in the pi(+)eta, pi(0)eta mass distributions. The theory has three unknown parameters to determine the shape of the distributions and the ratio between the D+ -> pi(+) eta eta and D+ -> pi(+)pi(0) eta rates. This ratio restricts much the sets of parameters but there is still much freedom leading to different shapes in the mass distributions. We call for a measurement of these mass distributions that will settle the reaction mechanism, while at the same time provide relevant information on the way that the a(0)(980) resonance is produced in the reactions.
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Bayar, M., & Oset, E. (2022). Method to observe the J(P)=2(+) partner of the X-0(2866) in the B+ -> D+ D- K+ reaction. Phys. Lett. B, 833, 137364–6pp.
Abstract: We propose a method based on the moments of the D- K+ mass distribution in the B+ -> D+ D- K+ decay to disentangle the contribution of the 2(+) state, partner of X-0(2900) in the (D) over bar *K* picture for this resonance. Some of these moments show the interference patterns of the X-1(2900) and X-0(2900) with the 2(+) state, which provide a clearer signal of the 2(+) resonance than the 2(+) signal alone. The construction of these magnitudes from present data is easy to implement, and based on these data we show that clear signals for that resonance should be seen even with the present statistics.
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Bayar, M., Martinez Torres, A., Khemchandani, K. P., Molina, R., & Oset, E. (2023). Exotic states with triple charm. Eur. Phys. J. C, 83(1), 46–9pp.
Abstract: In this work we investigate the possibility of the formation of states from the dynamics involved in the D* D* D* system by considering that two D*'s generate a JP = 1+ bound state, with isospin 0, which has been predicted in an earlier theoretical work. We solve the Faddeev equations for this system within the fixed center approximation and find the existence of J(P) = 0(-), 1(-) and 2(-) states with charm 3, isospin 1/2, masses similar to 6000 MeV, which are manifestly exotic hadrons, i.e., with a multiquark inner structure.
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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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