arXiv subjects

M. Bayar

Publications and source records attributed to M. Bayar.

At least 19 recordsLinked to original sources

arXiv2023

Stripping triangle loops: Discussion of $D_s^+\to \rho^+\eta\to \pi^+\pi^0\eta$ in $a_0(980)$ production

We address a general problem in the evaluation of triangle loops stemming from the consideration of the range of the interaction involved in some of the vertices, as well as the energy dependence of the width of some unstable particles in the loop. We find sizeable corrections from both effects. We apply that to a loop relevant to the $D_s^+ \to \pi^+ \pi^0 \eta $ decay, and find reductions of about a factor of $4$ in the mass distribution of invariant mass of the $\pi \eta$ in the region of the $a_0(980)$. The method used is based on the explicit analytical evaluation of the $q^0$ integration in the $d^4q$ loop integration, using Cauchy's residues method, which at the same time offers an insight on the convergence of the integrals and the effect of form factors and cutoffs.

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arXiv2023

Predictions of super-exotic heavy mesons from $K^{}B^{}B^{*}$ interactions

We make a theoretical study of the three-body system composed of ${\bar K^*}{\bar B^*}{\bar B^*}$ to look for possible bound states, which could be associated to mesonic resonances of very exotic nature, containing open strange and double-bottom flavours. The three-body interaction is evaluated by using the fixed center approach to the Faddeev equations where the ${\bar B^*}{\bar B^*}$ is bound forming an $I(J^P)=0(1^+)$ state, as it was found in previous works, and the third particle, the ${\bar B^*}$, of much smaller mass, interacts with the components of the cluster. We obtain bound states for all the channels considered: spin $J=0$, 1 and 2, all of them with isospin $I=1/2$ and negative parity.

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arXiv2022

Exotic states with triple charm

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 $J^P=1^+$ 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 $\sim 6000$ MeV, which are manifestly exotic hadrons, i.e., with a multiquark inner structure.

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arXiv2022

Molecular states of $ D^* D^* \bar{K}^*$ nature

We study the interaction of two $ D^* $ and a $\bar{K}^{*}$ 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 $D^* \bar{K}^{*}$ interaction, where the $J^{P}=0^{+}$ bound state is identified with the $X_0 (2900)$, the $ D^* D^* \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 $56$ MeV to $151$ MeV and the widths from $80$ MeV to $100$ MeV.

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arXiv2022

The $X(3960)$ seen in $D_{s}^{+} D_{s}^{-}$ as the $X(3930)$ state seen in $ D^{+} D^{-} $

We perform a calculation of the interaction of the $ D \bar{D} $, $ D_{s} \bar{D}_{s} $ coupled channels and find two bound states, one coupling to $ D \bar{D} $ and another one at higher energies coupling mostly to $D_{s}^{+} D_{s}^{-}$. We identify this latter state with the $X_{0}(3930)$ seen in the $D^{+} D^{-}$ mass distribution in the $B^+ \to D^{+} D^{-} K^{+} $ decay, and also show that it produces an enhancement of the $D_{s}^{+} D_{s}^{-}$ mass distribution close to threshold which is compatible with the LHCb recent observation in the $B^+ \to D_{s}^{+} D_{s}^{-} K^{+} $ decay which has been identified as a new state, $X_{0}(3960)$.

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arXiv2022

Method to observe the $J^{P}=2^{+}$ partner of the $X_{0}(2866)$ in the $B^+ \to D^{+} D^{-} K^{+} $ reaction

We propose a method based on the moments of the $D^{-} K^{+}$ mass distribution in the $B^+ \to D^{+} D^{-} K^{+} $ decay to disentangle the contribution of the $ 2^{+} $ state, partner of $X_{0}(2900)$ in the $ \bar D^{*} 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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arXiv2020

Analysis of the $ψ(4040)$ and $ψ(4160)$ decay into $D^{(\ast)} \bar D^{(\ast)}$, $D_s^{(\ast)}\bar D_s^{(\ast)}$

We have performed an analysis of the $e^+ e^- \to D^{(*)} \bar D^{(*)}$ data in the region of the $ψ(4040)$ and $ψ(4160)$ resonances which have a substantial overlap and require special care. By using the $^3 P_0$ model to relate the different $D^{(*)} \bar D^{(*)}$ 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 $c \bar c$ states and the weight of the meson-meson components in the wave function is very small.

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arXiv2019

Line shape and $D^{(\ast)}\bar D^{(\ast)}$ probabilities of $ψ(3770)$ from the $e^+e^-\to D\bar D$ reaction

We have performed a calculation of the $D\bar D$, $D\bar D^\ast$, $D^\ast\bar D$, $D^\ast\bar D^\ast$ components in the wave function of the $ψ(3770)$. For this we make use of the $^3P_0$ model to find the coupling of $ψ(3770)$ to these components, that with an elaborate angular momentum algebra can be obtained with only one parameter. Then we use data for the $e^+e^-\to D\bar D$ reaction, from where we determine a form factor needed in the theoretical frame work, as well as other parameters needed to evaluate the meson-meson selfenergy of the $ψ(3770)$. 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 $80\sim85\%$, and the individual meson-meson components are rather small, providing new empirical information to support the largely $q\bar q$ component of vector mesons, and the $ψ(3770)$ in particular.

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arXiv2018

Production and mixing of scalar mesons in $η_c$ and $χ_{c1}$ decays

We briefly discuss how the chiral unitary approach in coupled channels and $SU(3)$ symmetry can be used to describe the production of $f_0(500)$, $f_0(980)$ and $a_0(980)$ in the $χ_{c1} \to ηπ^+ π^-$ reaction, recently measured by the BESIII collaboration. In this reaction a very strong peak for the $a_0(980)$ can be seen in the $ηπ$ invariant mass, while clear signals for the $f_0(500)$ and $f_0(980)$ appear in the one of $π^+π^-$. Next, we show the predictions made with the same model for the analogous decay $η_c \to ηπ^+ π^-$, which could also be measured experimentally. We discuss the differences of these two reactions which are interesting to test the picture where these scalar mesons are dynamically generated from the interaction of pairs of pseudoscalars. Furthermore, we comment on a new recent work where the same model was used to study the $a_0(980) - f_0(980)$ mixing in the $χ_{c1} \to π^0 π^0 η$ and $χ_{c1} \to π^0 π^+ π^-$ reactions, showing that quantitative agreement with the experimental measurement of this mixing, also performed by BESIII, can be obtained, revealing interesting aspects of the dynamics of this process and the importance of coupled channels.

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arXiv2017

$a_0(980) - f_0(980)$ mixing in $χ_{c1} \to π^0 f_0(980) \to π^0 π^+ π^-$ and $χ_{c1} \to π^0 a_0(980) \to π^0 π^0 η$

We study the isospin breaking in the reactions $χ_{c1} \to π^0 π^+ π^-$ and $χ_{c1} \to π^0 π^0 η$ 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 $χ_{c1} \to ηπ^+ π^-$ reaction (also measured by BESIII), and further explored in the predictions to the $η_{c} \to ηπ^+ π^-$, can be successfully employed in the present study. We assume that the $χ_{c1}$ 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 the pairs of mesons created in the $χ_{c1}$ 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 $π^0η\to π^+π^-$ amplitude nonzero, which gives an important contribution and also enhances the effect of the $K\bar{K}$ term. Also, we find that in the total amplitude the most important effect is the isospin breaking inside the $T$ matrix, due to the constructive sum of $π^0η\to π^+π^-$ and $K\bar{K} \to π^+ π^-$, which is essential to get a good agreement with the experimental measurement of the mixing.

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arXiv2017

The role of the triangle singularity in $Λ(1405)$ production in the $π^-p\rightarrow K^0πΣ$ and $pp\rightarrow pK^+πΣ$ processes

We have investigated the cross section for the $π^-p\rightarrow K^0πΣ$ and $pp\rightarrow pK^+πΣ$ reactions paying attention to a mechanism that develops a triangle singularity. The triangle diagram is realized by the decay of a $N^*$ to $K^*Σ$ and the $K^*$ decay into $πK$, and the $πΣ$ finally merges into $Λ(1405)$. The mechanism is expected to produce a peak around $2140$ MeV in the $KΛ(1405)$ invariant mass. We found that a clear peak appears around $2100$ MeV in the $KΛ(1405)$ 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 $K^*Σ$ production. The mechanism studied produces the peak of the $Λ(1405)$ around or below 1400 MeV, as is seen in the $pp\rightarrow pK^+πΣ$ HADES experiment.

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arXiv2016

$D_{s0}^{*}(2317)^+$ in the decay of $B_c$ into $J/ψDK$

In this paper we study the relationship between the $D_{s0}^{*}(2317)^+$ resonance and the decay of the $B_c$ meson into $J/ψDK$. In this process, the $B_c$ meson decays first into $J/ψ$ and the quark pair $c\bar{s}$, and then the quark pair hadronizes into $DK$ or $D_sη$ components, which undergo final state interaction. This final state interaction, generating the $D_{s0}^{*}(2317)^+$ resonance, is described by the chiral unitary approach. With the parameters which allow us to match the pole position of the $D_{s0}^{*}(2317)^+$, we obtain the $DK$ invariant mass distribution of the decay $B_c\to J/ψDK$, and also the rate for $B_c\to J/ψD_{s0}^{*}(2317)$. The ratio of these two magnitude is then predicted.

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arXiv2015

States of $ρB^* \bar{B}^*$ with $J=3$ within the Fixed Center Approximation to Faddeev equations

In this work we study the $ρB^*\bar{B}^*$ three-body system solving the Faddeev equations in the fixed center approximation. We assume the $B^*\bar{B}^*$ system forming a cluster, and in terms of the two-body $ρB^*$ unitarized scattering amplitudes in the local Hidden Gauge approach we find a new $I(J^{PC})=1(3^{--})$ state. The mass of the new state corresponds to a two particle invariant mass of the $ρB^\ast$ system close to the resonant energy of the $B^\ast_2(5747)$, indicating that the role of this $J=2$ resonance is important in the dynamical generation of the new state.

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arXiv2015

Two, three, many body systems involving mesons. Multimeson condensates

In this talk we review results from studies with unconventional many hadron systems containing mesons: systems with two mesons and one baryon, three mesons, some novel systems with two baryons and one meson, and finally systems with many vector mesons, up to six, with their spins aligned forming states of increasing spin. We show that in many cases one has experimental counterparts for the states found, while in some other cases they remain as predictions, which we suggest to be searched in BESIII, Belle, LHCb, FAIR and other facilities.

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arXiv2015

States of $ρD^* \bar D^*$ with $J=3$ within the Fixed Center Approximation to the Faddeev equations

We study the interaction of the a $ρ$ and $D^*$, $\bar D^*$ with spins aligned using the Fixed Center Approximation to the Faddeev equations. We select a cluster of $D^* \bar D^*$, which is found to be bound in $I=0$ and can be associated to the X(3915), and let the $ρ$ meson orbit around the $D^*$ and $\bar D^*$. In this case we find an $I=1$ state with mass around 4340 MeV and narrow width of about 50 MeV. We also investigate the case with a cluster of $ρD^*$ and let the $\bar D^*$ orbit around the system of the two states. The $ρD^*$ cluster is also found to bind and leads to the $D^*_2(2460)$ state. The addition of the extra $\bar D^*$ produces further binding and we find, with admitted uncertainties, a state of $I=0$ around 4000 MeV, and a less bound narrow state with $I=1$ around 4200 MeV.

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arXiv2014

$B^0$ and $B^0_s$ decays into $J/ψ$ plus a scalar or vector meson

We extend a recent approach to describe the $B^0$ and $B^0_s$ decays into $J/ψ$ $f_0(500)$ and $J/ψ$ $f_0(980)$, relating it to the $B^0$ and $B^0_s$ decays into $J/ψ$ and a vector meson, $ϕ$, $ρ$, $K^*$. In addition the $B^0$ and $B^0_s$ decays into $J/ψ$ and $κ(800)$ are evaluated and compared to the $K^*$ vector production. The rates obtained are in agreement with available experiment while predictions are made for the $J/ψ$ plus $κ(800)$ decay.

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arXiv2014

Signature of an $h_1$ state from $J/ψ\to ηK^{0}\bar{K}^{0}$ and theoretical description of the $Z_c(3900)$ and $Z_c(4020)$ as $D \bar D^$ and $D^ \bar D^*$ molecular states

In this talk we address two topics: The first one is an empirical explanation in terms of a new state $h_1$ of the peak in the $K^{*0}\bar{K}^{*0}$ invariant mass distribution close to threshold of this channel in the $J/ψ\to ηK^{*0}\bar{K}^{*0}$ decay. The second one is a theoretical description of the isospin $I=1$ $Z_c(3900)$ and $Z_c(4020)$ states in terms of molecular states of $D \bar D^*+ cc$ and $D^* \bar D^*$.

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arXiv2014

Prediction of an $I=1$ $D \bar D^*$ state and relationship to the claimed $Z_c(3900)$, $Z_c(3885)$

We study here the interaction of $D \bar D^*$ in the isospin $I=1$ channel in the light of recent theoretical advances that allow to combine elements of the local hidden gauge approach with heavy quark spin symmetry. We find that the exchange of light $q \bar q$ is OZI suppressed and, thus, we concentrate on the exchange of heavy vectors and of two pion exchange. The latter is found to be small compared to the exchange of heavy vectors, which then determines the strength of the interaction. A barely $D\bar{D}^*$ bound state decaying into $η_cρ$ and $πJ/ψ$ is found. At the same time we reanalyze the data of the BESIII experiment on $e^+ e^- \to π^{\pm} (D \bar D^*)^\mp$, from where a $Z_c(3885)$ state was claimed, associated to a peak in the $(D \bar D^*)^\mp$ invariant mass distribution close to threshold, and we find the data compatible with a resonance with mass around $3875$ MeV and width around $30$ MeV. We discuss the possibility that this and the $Z_c(3900)$ state found at BESIII, reconfirmed at 3896 MeV at Belle, or 3885 MeV at CLEO, could all be the same state and correspond to the one that we find theoretically.

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