arXiv subjects

J. R. Peláez

Publications and source records attributed to J. R. Peláez.

At least 19 recordsLinked to original sources

arXiv2026

Hadron Physics Opportunities at FAIR

This White Paper outlines a coordinated, decade-spanning programme of hadron and QCD studies anchored at the GSI/FAIR accelerator complex. Profiting from intense deuteron, proton and pion beams coupled with high-rate capable detectors and an international theory effort, the initiative addresses fundamental questions related to the strong interaction featuring confinement and dynamical mass generation. This includes our understanding of hadron-hadron interactions and the composition of hadrons through mapping the baryon and meson spectra, including exotic states, and quantifying hadron structure. This interdisciplinary research connects topics in the fields of nuclear, heavy-ion, and (nuclear) astro (particle) physics, linking, for example, terrestrial data to constraints on neutron star structure. A phased roadmap with SIS100 accelerator start-up and envisaged detector upgrades will yield precision cross sections, transition form factors, in-medium spectral functions, and validated theory inputs. Synergies with external programmes at international accelerator facilities worldwide are anticipated. The programme is expected to deliver decisive advances in our understanding of non-perturbative (strong) QCD and astrophysics, and high-rate detector and data-science technology.

hep-ex↗

arXiv2026

A dispersive method to study CP asymmetries in hadronic multi-body $B$ decays

We present the details of a dispersive method to construct the amplitudes for hadronic multibody $B$ decays based on the universality of pairwise hadronic final-state interactions at low invariant masses. This approach allows us to split the amplitude into source terms controlled by phenomenological parameters and final-state interactions, governed by the precise knowledge of two-body dynamics, both resonant and non-resonant. As a concrete application, we make use of the well-determined low-energy pion-pion ($ππ$) interactions to understand the enhanced localized CP violation observed in $B^{\pm}\rightarrow K^{\pm}π^+π^-$. Fitting only angle-integrated CP-asymmetry data, the method successfully predicts the Dalitz plot differential distribution of events and of the CP asymmetry in the low-energy region. This allows for a better understanding of the large localized CP asymmetry recently reported by LHCb, which is shown not to be driven by an absolute enhancement of CP-violating effects, but by a suppression of the CP-conserving part resulting from the interplay of several partial waves. Moreover, we show that the widely-neglected non-resonant isospin-2 contributions play an essential role in the description of CP violation in this system. The method can be straightforwardly adapted to other multibody decays, where final-state two-hadron interactions drive the CP violation.

hep-ph↗

arXiv2026

Understanding large localized CP violation in $B^\pm\to K^\pmπ^+π^-$ using dispersive methods

We utilize the universality of pion-pion ($ππ$) final-state interactions at small invariant masses to understand the enhanced localized CP violation in $B^\pm\to K^\pmπ^+π^-$, using a dispersive approach. From a fit to the integrated CP-asymmetry data, we successfully predict the Dalitz-plot kinematic distribution of the asymmetry in the low-energy $ππ$ region, including the large localized CP violation recently observed by LHCb. An essential role is played by the contributions of isospin 2. This formalism, whose parameters have a physical meaning, can be adapted straightforwardly to other systems with CP violation enhanced by final-state interactions.

hep-ph↗

arXiv2025

Global parametrizations of $ππ$ scattering with dispersive constraints: Beyond the S0 wave

We provide new global parametrizations of $ππ\to ππ$ scattering for the S2, P, D, F, and G partial waves up to at least 1.8 GeV, easy to implement for phenomenological use. With earlier S0-wave parametrizations, slightly updated here, they reproduce previous partial wave dispersion analyses up to the $πω$ threshold. In addition, these new parametrizations have improved their description of recent P-wave data, the inelasticity in various waves, and their fulfillment of Roy-like and forward dispersion relations. The latter now test very high partial waves and have an improved matching with the Regge regime, extending those with P-wave contributions up to 1.6 GeV. Above 1.6 GeV and up to 1.8 GeV, or sometimes somewhat beyond, the parametrizations are simple unconstrained fits to data.

hep-ph↗

arXiv2025

Description of femtoscopic correlations with realistic pion-kaon interactions: the $κ/K^*_0(700)$ case

In this work, we show how $π^+ K_S$ femtoscopic correlations, recently reported by ALICE collaboration in $ pp $ collisions, can be well described taking into account relativistic corrections and using realistic $ πK $ interactions. These are obtained from a dispersive analysis of scattering data, which provides an accurate and model-independent description of the $ κ/K^*_0(700) $ resonance pole. The chiral symmetry suppression of the $ πK $ interactions at low energies and the non-ordinary features of the $ κ/K^*_0(700) $ seem to suggest that the $ π^+ K_S $ source radius might be surprisingly smaller than for other hadronic processes when using the standard and simple Lednicky-Lyuboshits factorization approximation.

hep-ph↗

arXiv2024

Improving $ππ$ dispersive analyses and resonance determination with Forward Dispersion Relations

We present preliminary results of an improved pion-pion scattering dispersive analysis that includes: a refined treatment of inelasticities, the introduction of G-waves, the extension of Forward Dispersion Relations as constraints up to 1.6 GeV, and data description up to roughly 1.8 GeV. Additionally, we impose Roy-like dispersion relations. As a result, we obtain three reliable solutions corresponding to three different datasets. From the Forward Dispersion Relation output, we extract resonance pole parameters in a parameterization-independent way using continued fractions.

hep-ph↗

arXiv2023

Note on the definitions of branching ratios of overlapping resonances

Branching ratios for the decay of hadrons with large width or near thresholds depend on their definition. We test different definitions and show that rather different branching ratios can be obtained. For wide resonances and for sequential decays with wide intermediate resonances, integration over the spectral functions is mandatory. The tests are performed exploiting the latest solution of the Bonn-Gatchina multi-channel analysis and published values for residues of light scalar mesons. For a resonance overlapping with a threshold, in case its pole lies in a non-adjacent sheet, we show how the total width, needed for the branching ratios, does not correspond to the imaginary part of the pole position. We use the Madrid-Krakow dispersive parameterizations to illustrate this situation with the $f_0(980)$.

hep-ph↗

arXiv2023

Dispersive $ππ\rightarrow K\bar K$ amplitude and giant CP violation in B to three light-meson decays at LHCb

The LHCb collaboration has recently reported the largest CP violation effect from a single amplitude, as well as other giant CP asymmetries in several $B$-meson decays into three charmless light mesons. It is also claimed that this is predominantly due to $ππ\rightarrow K\bar K$ rescattering in the final state, particularly in the 1 to 1.5 GeV region. In these analyses the $ππ\rightarrow K\bar K$ amplitude is by default estimated from the $ππ$ elastic scattering amplitude and does not describe the existing $ππ\rightarrow K\bar K$ scattering data. Here we show how the recent model-independent dispersive analysis of $ππ\rightarrow K\bar K$ data can be easily implemented in the LHCb formalism. This leads to a more accurate description of the asymmetry, while being consistent with the measured scattering amplitude and confirming the prominent role of hadronic final state interactions, paving the way for more elaborated analyses.

hep-ph↗

arXiv2022

Dispersive $πK\to πK$ and $ππ\to K \bar{K}$ amplitudes from scattering data, threshold parameters and the lightest strange resonance $κ$ or $K^*_0(700)$

We discuss the simultaneous dispersive analyses of $πK\to πK$ and $ππ\to K \bar{K}$ scattering data and the $κ/K^*_0(700)$ resonance. The unprecedented statistics of present and future Hadron Experiments, modern Lattice QCD calculations, and the wealth of new states and decays, require such precise and model-independent analyses to describe final state interactions. We review the existing and often conflicting data and explain in detail the derivation of the relevant dispersion relations, maximizing their applicability range. Next, we review and extend the caveats on some data, showing their inconsistency with dispersion relations. Our main result is the derivation and compilation of precise amplitude parameterizations constrained by several $πK\to πK$ and $ππ\to K \bar{K}$ dispersion relations. These constrained parameterizations are easily implementable and provide the rigor and accuracy needed for modern experimental and phenomenological Hadron Physics. As applications, after reviewing their status and interest, we will provide new precise threshold and subthreshold parameters and review our dispersive determination of the controversial $κ/K^*_0(700)$ resonance and other light-strange resonances.

hep-ph↗

arXiv2022

Dispersive determination of low energy $πK$ interactions

We summarize the application of dispersion relations for the determination of low energy $πK$ interactions. In particular, we present our recent dispersive analyses for the complete study of both $πK\to πK$ and $ππ\rightarrow K \bar K$ channels. First, we summarize our approach, we study both channels by using several families of dispersion relations and present the most relevant partial waves. Then we apply the dispersive formalism to the threshold region, where we extract many different low-energy parameters.

hep-ph↗

arXiv2021

Precision dispersive approaches versus unitarized Chiral Perturbation Theory for the lightest scalar resonances $σ/f_0(500)$ and $κ/K_0^*(700)$

For several decades, the $σ/f_0(500)$ and $κ/K_0^*(700)$ resonances have been subject to long-standing debate. Both their existence and properties were controversial until very recently. In this tutorial review we compare model-independent dispersive and analytic techniques versus unitarized Chiral Perturbation Theory, when applied to the lightest scalar mesons $σ/f_0(500)$ and $κ/K_0^*(700)$. Generically, the former have settled the long-standing controversy about the existence of these states, providing a precise determination of their parameters, whereas unitarization of chiral effective theories allows us to understand their nature, spectroscopic classification and dependence on QCD parameters. Here we review in a pedagogical way their uses, advantages and caveats.

hep-ph↗

arXiv2020

Determination of the lightest strange resonance $K_0^*(700)$ or $κ$, from a dispersive data analysis

In this work we present a precise and model-independent dispersive determination from data of the existence and parameters of the lightest strange resonance $κ/K_0^*(700)$. We use both subtracted and unsubtracted partial-wave hyperbolic and fixed-$t$ dispersion relations as constraints on combined fits to $πK\rightarrowπK$ and $ππ\rightarrow K\bar K$ data. We then use the hyperbolic equations for the analytic continuation of the isospin $I=1/2$ scalar partial wave to the complex plane, in order to determine the $κ/K_0^*(700)$ and $K^*(892)$ associated pole parameters and residues.

hep-ph↗

arXiv2017

Dispersive analysis tools for $ππ$ and $πK$ scattering

In this talk we discuss the relevance of dispersive methods and their different applications to obtain simple but rigorous parameterizations of pion-pion and kaon-pion scattering. We show as an example our latest dispersive analysis of $πK$ scattering, where we provide simple parameterizations of data satisfying Forward Dispersion Relations up to 1.6 GeV.

hep-ph↗

arXiv2017

Strange resonance poles from $Kπ$ scattering below 1.8 GeV

In this work we present a determination of the mass, width and coupling of the resonances that appear in kaon-pion scattering below 1.8 GeV. These are: the much debated scalar $κ$-meson, nowdays known as $K_0^*(800)$, the scalar $K_0^*(1430)$, the $K^*(892)$ and $K_1^*(1410)$ vectors, the spin-two $K_2^*(1430)$ as well as the spin-three $K^*_3(1780)$. The parameters will be determined from the pole associated to each resonance by means of an analytic continuation of the $Kπ$ scattering amplitudes obtained in a recent and precise data analysis constrained with dispersion relations, which were not well satisfied in previous analyses. This analytic continuation will be performed by means of Padé approximants, thus avoiding a particular model for the pole parameterization. We also pay particular attention to the evaluation of uncertainties.

hep-ph↗

arXiv2016

Calculation of Regge trajectories of strange resonances and identification of the K0*(800) as a non-ordinary meson

We review how the Regge trajectory of an elastic resonance can be obtained just from its pole position and coupling, using a dispersive formalism. This allows us to deal correctly with the finite widths of resonances in Regge trajectories. In this way we can calculate the Regge trajectories for the $K^*(892)$, $K_1(1400)$ and $K^*_0(1430)$, obtaining ordinary linear Regge trajectories, expected for $q \bar q$ resonances. In contrast, for the $K^*_0(800)$ meson, the resulting Regge trajectory is non-linear and with much smaller slope, strongly supporting its non-ordinary nature.

hep-ph↗

arXiv2016

Forward dispersion relations for pion-kaon scattering and the K*0(800) resonance

We review our recent analysis of $πK$ scattering data in terms of forward dispersion relations, and also present the parameters of the strange resonances. This work consists of fits to the data that are constrained to satisfy analyticity requirements. The method yields a set of simple and consistent parameterizations that are compatible with forward dispersion relations up to 1.6 GeV while still describing the data. We also obtain the pole parameters of the $K^*_0(800)$ and the $K^*(892)$ resonances.

hep-ph↗

arXiv2014

The non-ordinary Regge behavior of the $f_0(500)$ meson

We review how the Regge trajectory of an elastic resonance can be obtained just from its pole position and coupling, by means of a dispersive formalism. This allows to deal correctly with the finite widths of resonances in Regge trajectories. For the $ρ(770)$ meson this method leads to the ordinary linear Regge trajectory with a universal slope. In contrast, for the $f_0(500)$ meson, the resulting Regge trajectory is non-linear and with much smaller slope. This is another strong indication of the non-ordinary nature of the lightest scalar meson.

hep-ph↗

arXiv2013

Varying the light quark mass: impact on the nuclear force and Big Bang nucleosynthesis

The quark mass dependences of light element binding energies and nuclear scattering lengths are derived using chiral perturbation theory in combination with non-perturbative methods. In particular, we present new, improved values for the quark mass dependence of meson resonances that enter the nuclear force. A detailed analysis of the theoretical uncertainties arising in this determination is presented. As an application we derive from a comparison of observed and calculated primordial deuterium and helium abundances a stringent limit on the variation of the light quark mass, $δm_q/m_q = 0.02 \pm 0.04$. Inclusion of the neutron lifetime modification under the assumption of a variation of the Higgs vacuum expectation value that translates into changing quark, electron, and weak gauge boson masses, leads to a stronger limit, $|δm_q/m_q| < 0.009$.

nucl-th↗