arXiv subjects

Luciano M. Abreu

Publications and source records attributed to Luciano M. Abreu.

At least 37 records · Page 2Linked to original sources

arXiv2023

$B^+$ decay to $K^+ηη$ with ($ηη$) from the $D\bar{D}(3720)$ bound state

We search for a $B$ decay mode where one can find a peak for a $D \bar{D}$ bound state predicted in effective theories and in Lattice QCD calculations, which has also been claimed from some reactions that show an accumulated strength in $D \bar{D}$ production at threshold. We find a good candidate in the $B^+\to K^+ ηη$ reaction, by looking at the $ηη$ mass distribution. The reaction proceeds via a first step in which one has the $B^+\to D_s^{*+} \bar{D}^0$ reaction followed by $D_s^{*+}$ decay to $D^0 K^+$ and a posterior fusion of $D^0 \bar{D}^0$ to $ηη$, implemented trough a triangle diagram that allows the $D^0 \bar{D}^0$ to be virtual and produce the bound state. The choice of $ηη$ to see the peak is based on results of calculations that find the $ηη$ among the light pseudoscalar channels with stronger coupling to the $D \bar{D}$ bound state. We find a neat peak around the predicted mass of that state in the $ηη$ mass distribution, with an integrated branching ratio for $B^+\to K^+$ ($D\bar{D}$, bound) ; ($D\bar{D}$, bound) $\to ηη$ of the order of $1.5 \times 10^{-4}$, a large number for hadronic $B$ decays, which should motivate its experimental search.

hep-ph↗

arXiv2023

$J/ψ$ decay to $ ϕ,ω, K^{0}$ plus $f_0(1370)$, $f_0(1710)$, $K_0^(1430)$, $f_2(1270)$, $f'_2(1525)$ and $K_2^*(1430)$: role of the $D$-wave for tensor production

We reassess the decay of the $J/ψ$ into an $ω, ϕ, K^{*0}$ and one of the $f_0(1370)$, $f_0(1710)$, $f_2(1270)$, $f'_2(1525)$, $K_0^*(1430)$ and $K_2^*(1430)$ resonances. We benefit from previous works that considered this reaction as a $J/ψ$ decay into three vector mesons, with a scalar or tensor resonance being formed from the interaction of two of these vectors. The novelty here with respect to former studies is the investigation of the relation between the scalar meson and tensor productions for the first time. To this end, the spin structure of the four vectors present in the production vertex is analyzed, and the $D$-wave mechanism in the tensor production is included. Then, beyond the ratios studied previously involving scalar states and tensor states independently, new ratios relating the scalar and tensor meson productions are estimated. Our results suggest that the $D$-wave mechanism of tensor production assumes a relevant contribution. New experimental data reporting the angular distributions of these processes will be important for checking this conclusion.

hep-ph↗

arXiv2023

Role of $f_0(980)$ and $a_0(980)$ in the $B^- \to π^- K^+ K^- $ and $B^- \to π^- K^0 \bar K^0 $ reactions

In this work we study the role of the $f_0(980)$ and $a_0(980)$ resonances in the low $ K ^{+} K^{-} $ and $K^0 \bar K^0 $ invariant-mass region of the $B^- \to π^- K^+ K^- $ and $B^- \to π^- K^0 \bar K^0 $ reactions. The amplitudes are calculated by using the chiral unitary $\rm SU(3)$ formalism, in which these two resonances are dynamically generated from the unitary pseudocalar-pseudoscalar coupled-channel approach. The amplitudes are then used as input in the evaluation of the mass distributions with respect to the $ K^{+}K^{-} $ and $ K^{0}\bar K^{0} $ invariant-masses, where the contributions coming from the $I=0$ and $I=1$ components are explicitly assessed. Furthermore, the contribution of the $ K^{\ast }(892)^0 K^- $ production and its influence on the $ π^{-} K^+ $ and $ K^{+} K^- $ systems are also evaluated, showing that there is no significant strength for small $ K^{+} K^- $ invariant mass. Lastly, the final distributions of $ M_{\rm inv}^2( K^{\pm}K^{\mp} ) $ for the $B^{\mp} \to π^{\mp} K^{\pm}K^{\mp} $ reactions are estimated and compared with the LHCb data. Our results indicate that the $I=0$ component tied to the $f_0(980)$ excitation generates the dominant contribution in the range of low $ K ^{+} K^{-} $ invariant-mass.

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arXiv2023

Traces of the new $a_0(1780)$ resonance in the $J/ψ\to ϕK^+K^-(K^0\bar{K}^0)$ reaction

We study the $J/ψ\to ϕK \bar K$ decay, looking for differences in the production rates of $K^+ K^-$ or $K^0 \bar K^0$ in the region of 1700-1800 MeV, where two resonances appear dynamically generated from the vector-vector interaction. Two resonances are known experimentally in that region, the $f_0(1710)$ and a new resonance reported by the BABAR and BESIII collaborations. The $K \bar K$ should be produced with $I=0$ in that reaction, but due to the different $K^{*0}$ and $K^{*+}$ masses some isospin violation appears. Yet, due to the large width of the $K^*$, the violation obtained is very small and the rates of $K^+ K^-$ or $K^0 \bar K^0$ production are equal within $5\%$. However, we also find that due to the step needed to convert two vectors into $K \bar K$, a shape can appear in the $K \bar K$ mass distribution that can mimic the $a_0$ production around the $K^* \bar K^*$ threshold, and is simply a threshold effect.

hep-ph↗

arXiv2022

A note on the possible bound $D^{(\ast)} D ^{(\ast)}, \bar{B}^{(\ast)} \bar{B}^{(\ast)} $ and $D^{(\ast)} \bar{B}^{(\ast)} $ states

Motivated by the recently observation of the tetraquark $T_{cc}^+ $ state, in this work I revisit the Heavy-Meson Effective Theory to perform a simplified field-theoretical study of possible deuteron-like $D^{(\ast)} D ^{(\ast)}, \bar{B}^{(\ast)} \bar{B}^{(\ast)} $ and $D^{(\ast)} \bar{B}^{(\ast)} $ molecules. In particular, using the data from $T_{cc}^+ $ as input to fix the potential associated to the shallow-bound $ D D^{*} $ system with $I(J^P) = 1(1^+)$, the conditions for the formation of other loosely-bound states in the doubly charmed sector are analyzed. The other sectors are also discussed.

hep-ph↗

arXiv2022

Multiplicity of the doubly charmed state $T_{cc} ^+$ in heavy-ion collisions

We study the evolution of the doubly charmed state $T_{cc}^+$ in a hot hadron gas produced in the late stage of heavy-ion collisions. We use effective Lagrangians to calculate the thermally averaged cross sections of $T_{cc}^+$ production in reactions such as $ D^{(*)} D^{(*)} \rightarrow T_{cc}^+ π, T_{cc}^+ ρ$ and its absorption in the corresponding inverse processes. We then solve the rate equation to follow the time evolution of the $T_{cc}^+$ multiplicity, and determine how it is affected by the considered reactions during the expansion of the hadronic matter. We compare the evolution of the $T_{cc}^+$ abundance treated as a hadronic $S$-wave molecule and as a tetraquark state. Our results show that the tetraquark yield increases by a factor of about 2 at freeze-out, but it is still one order of magnitude smaller than the final yield of molecules formed from hadron coalescence. Also, the results indicate that $N_{T_{cc}}$ is more affected by interactions with hadronic medium than $ N_{X(3872)} $ in similar conditions. We also show that yields depend very weakly on the system size, represented by $\mathcal{N} = \left[ d N_{ch} / d η(η< 0.5)\right]^{1/3}$.

hep-ph↗

arXiv2022

An Effective Field Theory Treatment of the Production and Annihilation of Magnetic Monopoles and their Relic Abundance

We revisit the thermal production red and annihilation of magnetic monopoles and their relic abundance in order to gain a deeper physical interpretation on the monopole phenomenology predicted from the Baines et al. effective field theory, recently proposed in the description of monopole pair production via Drell-Yan and photon fusion processes. In this sense, we red use of the vacuum cross sections for the Drell-Yan reactions derived within the mentioned framework to evaluate the cross section averaged over the thermal distribution associated to other particles that constitute the hot medium where the monopoles propagate. In the considered range of monopole mass with spin-zero and spin-half, our findings suggest that the thermally averaged cross sections for the pair production are highly suppressed, while at higher temperatures those for the annihilation of lighter pairs reach larger magnitudes. Besides, we observe that smaller temperature leads to a rate of annihilation for scalar monopoles smaller than the one for fermionic monopoles, which might be interpreted as a theoretical evidence of a more pronounced stability for spin-0 and heavier monopoles.Then we input these thermally averaged cross sections into the kinetic equation that describes the evolution of the monopole abundance via an extension of a freeze-out theory. Our results infer that heavier monopoles achieve the equilibrium at earlier stages of the expansion, and consequently at higher temperatures. In addition, larger monopole masses produce higher values of the relic abundance. Besides, the results indicate that the abundance does not behave differently for spinless and spin-half relic monopoles.

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arXiv2022

Exotic hadrons in heavy ion collisions

Nucleus-nucleus collisions offer a great opportunity for analyzing and determining the intrinsic nature of heavy and exotic hadrons. In this sense, here we discuss how the production and dissociation of hadron states are affected by reactions during the expansion of hadronic matter in a heavy-ion collision environment. We give emphasis to recent works on exotic states, revisiting as a case study the time evolution of the abundances of the $X_{0,1}(2900)$ states.

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arXiv2022

Properties of neutral mesons in a hot and magnetized quark matter: size-dependent effects

In this work we investigate the combined finite-size and thermomagnetic effects on the properties of neutral mesons in a hot medium, in the context of the Nambu--Jona-Lasinio model. In particular, by using the mean-field approximation and the Schwinger proper time method in a toroidal topology with antiperiodic conditions, we evaluate the chiral phase transition, the constituent quark mass and meson observables like the $π^0$ and $σ$ meson masses and pion decay constant under the change of the size, temperature, chemical potential and strength of external magnetic field. The results indicate that the observables are strongly affected by the conjoint effects of relevant variables, and the net result will depend on the balance of these competing phenomena.

hep-ph↗

arXiv2021

New $Z_c$ spectroscopy or Landau singularities? Searches in Heavy Ion Collisions could help decide

A constellation of quarkonium-mass peaks has been reported in the last decade, opening what could be an entire new spectroscopy of nuclear-physics like complexity. Salient among these structures are the $Z_c$, much analyzed at BESIII as nicely summarised by J.~Zhao at this conference. Their stature as new hadron states has often been challenged by proposals that the peaks arise from triangle singularities instead, because they appear in three-body reactions and often satisfy the special kinematic conditions of the Coleman-Norton theorem. To experimentally decide, we should like to resort to different reactions erasing the kinematic coincidence, and see whether each peak survives. We observe that the most universal "eraser" is the medium created in Heavy Ion Collisions, because its high temperature often affects the masses and widths of the particles participating in the reaction: if additionally the triangle reaction is completed during the lifetime of the fireball, our computations in thermal field theory show that the triangle singularities do not survive the hot hadron phase (much less the hotter quark-gluon plasma). On the contrary, ordinary quarkonia are affected but often survive the fireball and molecular-like states are also routinely detected. We have provided several examples, and here investigate the exotic $Z_{c}(4020)^\pm\to π^{\pm} h_c $ peak (produced against a $π^\mp$ in $e^+e^-$ collisions). If, as has been proposed during the debates, it is produced or enhanced by a $D_{1} D^{*} D^*$ triangle loop, the estimate here reported suggests its disappearance near the critical temperature of the confinement/deconfinement phase transition, so any future detection in heavy-ion collision data would suggest it to be a real hadron, with its absence leaning towards the singularity interpretation.

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arXiv2021

The $Z_{cs}(3985)$ structure, if a triangle/kinematic singularity, would disappear when heated in Heavy Ion Collisons

Triangle and other kinematic singularities are very sensitive to the precise masses and widths of the intervening particles. Therefore, the effect that the heavy-ion collision medium can have on those masses and widths, as captured by finite-temperature field theory and reported in the literature, may erase the singularity from the spectrum if the effect is large enough and the loop completes before the hot gas freezes out. A very timely example is provided by the $Z_{cs}(3985)$ structure recently reported by BES-III in a $(D_s^-D^{*0}+D_s^{*-}D^0)$ spectrum recoiling against a $K^+$. If a new hadron, this would be a clear exotic $c\bar{c}s\bar{u}$ tetraquark candidate, the first of a charmonium-like family with strangeness: to accept this, alternative explanations first need to be tested and discarded. As shown in figure 1, the mass spectrum recoiling against the kaon is near the $m_{D_s^{*-}}+m_{D^0}$ threshold, whereas the production cross-section seems to peak around that for $\sqrt{s(e^-e^+)}=m_{D_{s2}^{*+}} +m_{D_s^{*-}} $. Therefore, this structure may well be caused by a triangle with the three charmed mesons $D_{s2}^{*+} / D_s^{*-} / D^0$ running in the loop, with the amplitude enhanced at the two thresholds. If so, the structure would be erased from the spectrum in Heavy Ion Collisions, whereas a hadron would continue to exist although with a mass decreased by a few percent as computed by other authors.

hep-ph↗

arXiv2021

Triangle singularities waning in Heavy Ion Collisions: the case of $Y(4260)\to π(πJ/ψ)$

We have recently observed that hadron triangle singularities, that can mock new exotic hadrons, can be significanttly suppressed in relativistic heavy ion collisions, provided two conditions are met: these are, first, that the fireball lives long enough so that the triangle process has enough time to complete in the Norton-Coleman classical sense, and second, that the mass and/or width of the particles in the triangle diagram are sufficiently modified from their vacuum values. Here we add a very interesting example to the canon, which is $Y(4260) \to D_1 D \to πD^* D \to π+ J/ψπ$. This reaction has been proposed as a mechanism to explain the appearance of $Z_c(3900)$ in the $J/ψπ$ spectrum. If the two muons and two pions reconstructing the initial-state $Y$ can be isolated from the combinatorial background, then the mechanism can provide a spectroscopy test: presence of $Y(4260)$ but absence of $Z_c(3900)$ would be more indicative of such triangle mechanism, while presence of both would rather point out to $Z_c$ being an exotic hadron.

hep-ph↗

arXiv2021

Heating triangle singularities in heavy ion collisions

We predict that triangle singularities of hadron spectroscopy can be strongly affected in heavy ion collisions. To do it we examine various effects on the singularity-inducing triangle loop of finite temperature in the terminal hadron phase. It appears that peaks seen in central heavy ion collisions are more likely to be hadrons than rescattering effects under two conditions. First, the flight-time of the intermediate hadron state must be comparable to the lifetime of the equilibrated fireball (else, the reaction mostly happens in vacuo after freeze out). Second, the medium effect over the triangle-loop particle mass or width must be sizeable. When these (easily checked) conditions are met, the medium quickly reduces the singularity: at T about 150 MeV, even by two orders of magnitude, acting then as a spectroscopic filter.

hep-ph↗

arXiv2021

Quarkonium interactions with (hot) hadronic matter

In this work, we present an updated study about the interactions of quarkonia with surrounding hadronic medium. The meson-meson interactions are described with a chiral effective Lagrangian within the framework of unitarized coupled channel amplitudes. In particular, we extend a previous work performed in the charmonium sector by calculating the cross-sections for $Υ$ scattering by light pseudoscalar mesons ($π, K, η$) and vector mesons ($ρ, K^\ast, ω$). We evaluate the relevant channels and compare the results with existing literature. The analysis is completed by including the finite-temperature effects in the unitarized scattering amplitudes for both quarkonium and bottomonium sectors.

hep-ph↗

arXiv2021

$X_J(2900)$ states in a hot hadronic medium

In this work we investigate the hadronic effects on the $X_{J=0,1} (2900)$ states in heavy-ion collisions. We make use of Effective Lagrangians to estimate the cross sections and their thermal averages of the processes $X_J π\to \bar{D}^{*} K , K^{*} \bar{D} $, as well as those of the corresponding inverse processes, considering also the possibility of different isospin assignments ($I=0,1$). We complete the analysis by solving the rate equation to follow the time evolution of the $X_J (2900)$ multiplicities and determine how they are affected by the considered reactions during the expansion of the hadronic matter. We also perform a comparison of the $X_J (2900)$ abundances considering them as hadronic molecular states ($J=0$ as a $S$-wave and $J=1$ as a $P$-wave) and tetraquark states at kinetic freeze-out.

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arXiv2019

Mixing and $m_q$ dependence of axial vector mesons in the Coulomb gauge QCD model

We discuss pure $q\bar{q}$ axial-vector mesons in the Tamm-Dancoff approximation of the Coulomb-gauge QCD model from NCSU. While recent studies have put emphasis in configuration mixing with open meson-meson channels, we here concentrate on the simpler closed-channel problem and follow the $1^+$ mixing through a wide range of quark masses. We also examine their radial excitations and discuss with them the concept of insensitivity to chiral symmetry breaking.

hep-ph↗

arXiv2015

Heavy mesons in a hadronic medium: interaction and transport coefficients

We review the recent results of heavy meson diffusion in thermal hadronic matter. The interactions of D and B-bar mesons with other hadrons (light mesons and baryons) are extracted from effective field theories based on chiral and heavy-quark symmetries. When these guiding principles are combined with exact unitarity, physical values of the cross sections are obtained. These cross sections (which contain resonant contributions) are used to calculate the drag and diffusion coefficients of heavy mesons immersed in a thermal and dense medium. The transport coefficients are computed using a Fokker-Planck reduction of the Boltzmann equation.

nucl-th↗

arXiv2014

$X(3872)$ production from reactions involving $D$ and $D^*$ mesons

In this proceeding we show the results found for the cross sections of the processes $\bar D D\toπX(3872)$, $\bar D^* D\to πX(3872)$ and $\bar D^* D^*\toπX(3872)$, information needed for calculations of the $X(3872)$ abundance in heavy ion collisions. Our formalism is based on the generation of $X(3872)$ from the interaction of the hadrons $\bar D^0 D^{*0} - \textrm{c.c}$, $D^- D^{*+} - \textrm{c.c}$ and $D^-_s D^{*+}_s - \textrm{c.c}$. The evaluation of the cross section associated with processes having $D^*$ meson(s) involves an anomalous vertex, $X\bar D^* D^*$, which we have determined by considering triangular loops motivated by the molecular nature of $X(3872)$. We find that the contribution of this vertex is important. Encouraged by this finding we estimate the $X\bar D^* D^*$ coupling, which turns out to be $1.95\pm 0.22$. We then use it to obtain the cross section for the reaction $\bar D^* D^*\toπX$ and find that the $X\bar D^* D^*$ vertex is also relevant in this case. We also discuss the role of the charged components of $X$ in the determination of the production cross sections.

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