arXiv subjects

R. Molina

Publications and source records attributed to R. Molina.

At least 19 recordsLinked to original sources

arXiv2026

The $B^{()}\bar{K}^{()}$-coupled-channel system in the hidden-gauge approach

In this work we provide predictions for bottom-strange molecular states within the Hidden Gauge Formalism. We study the coupled-channel scattering of $B^{(*)}\bar{K}^{(*)}$ states and, by fixing only one free parameter to obtain the mass of a new excited $B_s^0$ state seen by the LHCb, we predict the pole parameters of six states in this sector. Concretely, we get that the masses of the flavor partners of the $D_{s0}(2317)$ and $D_{s1}(2460)$ states in the bottom sector are $5760$ and $5802$ MeV for the $B\bar{K}$ ($J^P=0^+$) and $B^{*}\bar{K}$ ($1^+$) states, respectively. Moreover, the recently seen states by the LHCb with masses around $6100$ and $6160$ MeV can be interpreted as $B\bar{K}^*$ and $B^*\bar{K}^*$ molecular states, according to reasonable values of the pole parameters and the splitting between these two states obtained in our calculation.

hep-ph↗

arXiv2025

Pion scattering in finite volume within the Inverse Amplitude Method

We study the effect of a finite volume for pion-pion scattering within Chiral Perturbation Theory (ChPT) and the Inverse Amplitude Method (IAM) in a $L^3$ box (rest frame). Our full ChPT calculation takes into account the discretization not only in the $s$-channel loops but also in the $t,u$- channels and tadpole contributions. Hence, not only the unitarity right-hand cut but also the left-hand one continuum contributions are calculated in the finite volume. A proper extension of the standard Veltman-Pasarino identities is needed, as well as a suitable projection on the internal space spanned by the irreducible representations (irreps) of the octahedral group, based on either a finite set of cubic harmonics or the matrices which represent the irreps properly. From the ChPT we construct the IAM in the internal space, which provides the full volume dependence of the interacting energy levels of two-pions scattering in the finite volume. Our results for various low-energy constants sets show sizable corrections with respect to previous analyses in the literature for $ m_\pi L \lesssim 2$, being compatible with energy levels lattice data. We expect that our analysis and results will help to optimize the process of determination of energy levels and phase-shifts with higher accuracy.

hep-lat↗

arXiv2025

Off-shell ambiguities in correlation functions: strategies to minimize them

We face here the problem of uncertainties in correlation functions due to the freedom in the off-shell dependence of the wave functions, or equivalently, off-shell ambiguities in the scattering matrices. We make the study for the case of meson baryon interaction, choosing the $K\Lambda$, $K \Sigma$, $\eta N$ coupled channels, which are related to the $N^*(1535)$ resonance. We find that using realistic interactions based on chiral dynamics the uncertainties are small, of the order of $2-3$~\%, but could be much bigger if other methods are used. However, our study shows the way to optimally overcome these uncertainties in the analysis of correlation functions, and we provide a series of recommendations for any general analysis.

hep-ph↗

arXiv2024

One or two poles for the $\Xi(1820)$?

In this talk, we present a new interpretation for the recently observed $\Xi(1820)$ resonance. We recall that the chiral unitary approach for the interaction of pseudoscalar mesons with the baryons of the decuplet predicts two states for the $\Xi(1820)$ resonance, one with a narrow width and the other one with a large width. We contrast this fact with the recent BESIII measurement of the $K^- \Lambda$ mass distribution in the $\psi(3686)$ decay to $K^- \Lambda \bar\Xi^+ $, which demands a width much larger than the average of the PDG, and show how the consideration of the two $\Xi(1820)$ states provides a natural explanation to this apparent contradiction.

hep-ph↗

arXiv2024

Quark mass dependence of the $T_{cc}(3875)^+$ pole

Recently, several LQCD simulations have proven that the interaction in the isoscalar channel in $DD^*$ scattering is attractive. This channel is naturally connected to the $T_{cc}(3875)^+$ which is observed in the $D^0D^0\pi^+$ invariant mass distribution. However, it remains an open question whether the virtual bound state found in the several LQCD simulations is actually linked to the LHCb experimental observation. In this article we perform an EFT-based analysis of the LQCD data and demostrate that a proper chiral extrapolation leads to a $T_{cc}$ pole compatible with experiment. At the physical pion mass, we find a virtual bound state with a binding energy $\Delta E=-0.06 \left(^{+1.30}_{-2.20}\right) \left(^{+0.50}_{-1.11}\right)$. Moreover, we extract from a global analysis both, the light and heavy quark mass dependence of the $T_{cc}$ pole, and study the role of the $\rho$ and $\pi$ meson exchanges.

hep-ph↗

arXiv2024

Pole analysis for the $D^{}\bar K$-$D\bar{K^}$ coupled-channel system

By solving the Lippmann-Schwinger equation, possible hadronic molecules in the $D^*\bar K$-$D\bar K^*$ coupled-channel system are investigated with the one-meson exchange potentials, where both vector and pseudoscalar mesons are considered as exchange particles. We find an S-wave virtual state with mass $M=2487$ MeV, and a resonance with $M=2759$ and width $\Gamma=18$ MeV. In the $D^* \bar K$ invariant mass distribution, the virtual state appears as a cusp at the $D^*\bar K$ threshold, while the resonance potentially manifests as a dip. In particular, we take into account the $D\bar K \pi$ three-body dynamics due to the on-shell pion exchange and the finite decay width for $\bar K^*$.

hep-ph↗

arXiv2024

Hyperbolic Secant representation of the logistic function: Application to probabilistic Multiple Instance Learning for CT intracranial hemorrhage detection

Multiple Instance Learning (MIL) is a weakly supervised paradigm that has been successfully applied to many different scientific areas and is particularly well suited to medical imaging. Probabilistic MIL methods, and more specifically Gaussian Processes (GPs), have achieved excellent results due to their high expressiveness and uncertainty quantification capabilities. One of the most successful GP-based MIL methods, VGPMIL, resorts to a variational bound to handle the intractability of the logistic function. Here, we formulate VGPMIL using P\'olya-Gamma random variables. This approach yields the same variational posterior approximations as the original VGPMIL, which is a consequence of the two representations that the Hyperbolic Secant distribution admits. This leads us to propose a general GP-based MIL method that takes different forms by simply leveraging distributions other than the Hyperbolic Secant one. Using the Gamma distribution we arrive at a new approach that obtains competitive or superior predictive performance and efficiency. This is validated in a comprehensive experimental study including one synthetic MIL dataset, two well-known MIL benchmarks, and a real-world medical problem. We expect that this work provides useful ideas beyond MIL that can foster further research in the field.

cs.LG↗

arXiv2023

Correlation function for the $a_0(980)$

We have conducted a model independent analysis of the $K^+ \bar{K}^0$ pair correlation function obtained from ultra high energy $pp$ collisions, with the aim of extracting the information encoded in it related to the $K\bar{K}$ interaction and the coupled channel $\pi^+ \eta$. With the present large errors at small relative $K^+\bar{K}^0$ momenta, we find that the information obtained about the scattering matrix suffers from large uncertainties. Even then, we are able to show that the data imply the existence of the $a_0$ resonance, $a_0(980)$, showing as a strong cusp close to the $K\bar{K}$ threshold. We also mention that the measurement of the $\pi^+ \eta$ correlation function will be essential in order to constrain more the information on $K\bar{K}$ dynamics that can be obtained from correlation functions.

hep-ph↗

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.

hep-ph↗

arXiv2023

Contrasting observables related to the $N^*(1535)$ from the molecular or a genuine structure

In this work we compare the predictions for the scattering length and effective range of the channels $K^0 \Sigma^+, K^+ \Sigma^0 , K^+ \Lambda$ and $\eta p$, assuming the $N^*(1535)$ state as a molecular state of these channels, or an original genuine state, made for instance from three quarks. Looking at very different scenarios, what we conclude is that the predictions of these two pictures are drastically different, to the point that we advise the measurement of these magnitudes, accessible for instance by measuring correlation functions, in order to gain much valuable information concerning the nature of this state.

hep-ph↗

arXiv2023

The $T_{c\bar{s}}(2900)$ as a threshold effect from the interaction of the $D^K^$, $D^*_s\rho$ channels

We investigate the $D^*K^*$ and $D^*_s\rho$ interaction in coupled channels within the hidden gauge formalism. A structure is developed around their thresholds, short of producing a bound state, which leads to a peak in the $D_s^+ \pi^-$ mass distribution in the $B^0 \to \bar{D}^0 D_s^+ \pi^-$ decay compatible with the experimental data. We conclude that the interaction between the $D^*K^*$ and $D^*_s\rho$ is essential to produce the cusp structure that we associate to the recently seen $T_{c\bar{s}}(2900)$, and that its experimental width is mainly due to the decay width of the $\rho$ meson. The peak obtained together with a smooth background reproduces fairly well the experimental mass distribution observed in the $B_0 \to \bar{D}^0 D_s^+ \pi^-$ decay.

hep-ph↗

arXiv2023

Two states for the $\Xi(1820)$ resonance

We recall that the chiral unitary approach for the interaction of pseudoscalar mesons with the baryons of the decuplet predicts two states for the $\Xi(1820)$ resonance, one with a narrow width and the other one with a large width. We contrast this fact with the recent BESIII measurement of the $K^- \Lambda$ mass distribution in the $\psi(3686)$ decay to $K^- \Lambda \bar\Xi^+ $, which demands a width much larger than the average of the PDG, and show how the consideration of the two $\Xi(1820)$ states provides a natural explanation to this apparent contradiction.

hep-ph↗

arXiv2023

Quark mass dependence of the $D_{s0}^*(2317)$ and $D_{s1}(2460)$ resonances

We determine the quark mass dependence - light and heavy - of the $D_{s0}^*(2317)$ and $D_{s1}(2460)$ properties, such as, mass, coupling to $DK$, scattering lengths and compositeness, from a global analysis of $DK$ energy levels from LQCD. In particular, we analyze the HSC energy levels for $DK$ scattering in $I=0$ for different boosts and two pion masses. The formalism is based in the local hidden-gauge interaction of Weinberg-Tomozawa type which respects chiral and heavy quark spin symmetries, supplemented by a term that takes into account the $D^{(*)}K$ coupling to a bare $c\bar{s}$ component. The isospin violating decay of the $D_{s0}^*(2317)\to D_{s}^+\pi^0$ is also evaluated.

hep-ph↗

arXiv2023

AGATA: Advancements in Software Developments

Presently, gamma-ray tracking in germanium segmented detectors is realised by applying two advanced, complex algorithms. While they have already triggered an intensive R&D, they are still subject to further improvements. Making such algorithms effective, online in real time conditions and/or offline for deeper analysis, in data pipelines do require many additional software developments. This review paper gives an overview of the various bricks of software produced so far by the AGATA collaboration. It provides hints of what is foreseen for the next phases of the project up to its full configuration namely with 180 capsules in the array.

physics.ins-det↗

arXiv2023

Quark mass dependence of the low-lying charmed mesons at one loop in HH$\chi$PT

We study the light and heavy quark mass dependence of the low-lying charmed mesons in the framework of one-loop HH$\chi$PT. The low energy constants are determined by analyzing the available lattice data from different LQCD simulations. Model selection tools are implemented to determine the relevant parameters as required by data with a higher precision. Discretization and other effects due to the charm quark mass setting are discussed.

hep-lat↗

arXiv2023

Quark mass dependence of hadron resonances

We study the dependence of the $D_{s0}(2317)$ mass on the light quark mass through the analysis of data from QCD lattice simulations. Combining HH$χ$PT and model selection tools as the LASSO method we fit the lattice data of the low-lying charmed mesons masses, obtaining their extrapolation to the physical point and extracting results for the quark mass dependence of the exotic resonances $D_{s0}(2317)$ and $D_{s1}(2460)$, taking as input the energy levels from a lattice simulation.

hep-lat↗

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.

hep-ph↗

arXiv2022

The $T_{c\bar{s}}(2900)$ as a threshold effect from the interaction of the $D^K^$, $D^*_s\rho$ channels

We look at the mass distribution of the $D_s^+ \pi^-$ in the $B^0 \to \bar{D}^0 D_s^+ \pi^-$ decay, where a peak has been observed in the region of the $D^*_s \rho$, $D^* K^*$ thresholds. By creating these two channels together with a $\bar{D}^0$ in $B^0$ decay and letting them interact as coupled channels, we obtain a structure around their thresholds, short of producing a bound state, which leads to a peak in the $D_s^+ \pi^-$ mass distribution in the $B^0 \to \bar{D}^0 D_s^+ \pi^-$ decay. We conclude that the interaction between the $D^*K^*$ and $D^*_s\rho$ is essential to produce the cusp structure that we associate to the recently seen $T_{c\bar{s}}(2900)$, and that its experimental width is mainly due to the decay width of the $\rho$ meson. The peak obtained together with a smooth background reproduces fairly well the experimental mass distribution observed in the $B_0 \to \bar{D}^0 D_s^+ \pi^-$ decay.

hep-ph↗