arXiv subjects

E. Ruiz Arriola

Publications and source records attributed to E. Ruiz Arriola.

At least 19 recordsLinked to original sources

arXiv2026

Global superscaling analysis of quasielastic electron scattering with relativistic effective mass

We present a global analysis of the inclusive quasielastic electron scattering data with a superscaling approach with relativistic effective mass. The SuSAM* model exploits the approximation of factorization of the scaling function $f^*(ψ^*)$ out of the cross section under quasifree conditions. Our approach is based on the relativistic mean field theory of nuclear matter where a relativistic effective mass for the nucleon encodes the dynamics of nucleons moving in presence of scalar and vector potentials. Both the scaling variable $ψ^*$ and the single nucleon cross sections include the effective mass as a parameter to be fitted to the data alongside the Fermi momentum $k_F$. Several methods to extract the scaling function and its uncertainty from the data are proposed and compared. The model predictions for the quasielastic cross section and the theoretical error bands are presented and discussed for nuclei along the periodic table from $A=2$ to $A=238$: $^2$H, $^3$H, $^3$He, $^4$He, $^{12}$C, $^{6}$Li, $^{9}$Be, $^{24}$Mg, $^{59}$Ni, $^{89}$Y, $^{119}$Sn, $^{181}$Ta, $^{186}$W, $^{197}$Au, $^{16}$O, $^{27}$Al, $^{40}$Ca, $^{48}$Ca, $^{56}$Fe, $^{208}$Pb, and $^{238}$U. We find that more than 9000 of the total $\sim 20000$ data fall within the quasielastic theoretical bands. Predictions for $^{48}$Ti and $^{40}$Ar are also provided for the kinematics of interest to neutrino experiments.

nucl-th↗

arXiv2026

Coarse graining the Bethe-Goldstone equation: nucleon-nucleon high momentum components

The delta-shell representation of the nuclear force allows a simplified treatment of nuclear correlations. We show how this applies to the Bethe-Goldstone equation as an integral equation in coordinate space with a few mesh points, which is solved by inversion of a 5-dimensional square matrix in the single channel cases and a $10\times10$ matrix for the tensor-coupled channels. This allows us to readily obtain the high momentum distribution, for all partial waves, of a back-to-back correlated nucleon pair in nuclear matter. We find that the probability of finding a high-momentum correlated neutron-proton pair is about 18 times that of a proton-proton one, as a result of the strong tensor force, thus confirming in an independent way previous results and measurements.

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arXiv2025

Power corrections in the quark-antiquark potential at finite temperature

A recently proposed phenomenological model, which includes nonperturbative effects from dimension two gluon condensates, is applied to analyze the available lattice data for the heavy quark free energy in the deconfined phase of quenched QCD. For large $q\bar{q}$ separations, we recover previous results for the Polyakov loop, exhibiting unequivocal power corrections in the temperature. For the $q\bar{q}$ potential at finite temperature and finite separation, we find that a good overall description of the lattice data can be achieved once the condensate is properly accounted for. In addition, the model predicts a duality between the zero temperature potential as a function of the $q\bar{q}$ separation, on the one hand, and the quark selfenergy as a function of the temperature, on the other, which turns out to be satisfied to a high degree by the lattice 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↗

arXiv2023

Center-of-mass momentum dependence of short-range correlations with the coarse-grained Granada potential

The effect of the center of mass motion on the high-momentum distributions of correlated nucleon pairs is studied by solving the Bethe-Goldstone equation in nuclear matter with the Granada nucleon-nucleon potential. We show that this coarse-grained potential reduces the problem to an algebraic linear system of five (ten) equations for uncoupled (coupled) partial waves that can be easily solved. The corresponding relative wave functions of correlated pn, pp and nn pairs are computed for different values of their CM momentum. We find that the pn pairs dominate the high-momentum tail of the relative momentum distribution, and that this only depends marginally on center of mass momentum. Our results provide further justification and agreement for the factorization approximation commonly used in the literature. This approximation assumes that the momentum distribution of nucleon pairs can be factorized as the product of the center of mass momentum distribution and the relative momentum distribution.

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arXiv2021

On-shell transition of SRG and nuclear systems

We make variational estimates for the binding energies of $^2H,~^3H,~^4He,~^{16}O,~^{40}Ca$, showing their running with the Similarity Renormalization Group (SRG) cutoff towards the infrared region and show the generalized Tjon lines that emerge from the calculations. We infer the SRG evolution of the three-body contributions for the $^3H$ and $^4He$ binding energies by computing the two-body contributions with a variational approach assuming that four-body forces are negligible. At any given SRG cutoff, the three-body contributions may then be inferred as being the experimental value minus the two-body contributions. The off-shell / on-shell transition at a critical SRG cutoff $λ_c$ drives the behavior of all binding energies and this scale is the turning point of the generalized Tjon lines. Also, at $λ_c$ the ratios between three-body and two-body contributions to the binding energies, $B_{λ_c}(3) ~/~ B_{λ_c}(2)$, are the same in both $^3H$ and $^4He$ systems and equal to $1/4$, so that $B_{λ_c}(2) ~=~ 4~B_{λ_c}(3)$. All calculations are carried out with the Idaho-Salamanca N3LO potential, which is evolved with the SRG up to the infrared fixed point ($λ\to 0$) in all S, P, D, F and G partial-wave channels in order to compute the variational binding energies at several SRG cutoff scales.

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arXiv2020

Quark-diquark string tension, excited baryonic resonances and thermal fluctuations

We study the baryonic fluctuations from second to eighth order involving electric charge, baryon number and strangeness below the quark-gluon plasma crossover and numerically known from lattice QCD calculations. By considering a particular realization of the Hadron Resonance Gas model, we provide evidence on the dominant role of quark-diquark degrees of freedom to describe excited baryonic resonances. After proving by means of suitable Polyakov loop correlators that the quark-diquark and the quark-antiquark forces coincide, $V_{\bar q q } (r) = V_{\bar q D } (r) + \textrm{const}$, we find that the corresponding susceptibilities can be saturated with excited baryonic states in a quark-diquark model picture.

hep-ph↗

arXiv2020

The X(3872) as a mass distribution

All existing experimental evidence of the bound state nature of the X(3872) relies on considering its decay products with a finite experimental spectral mass resolution which is typically $Δm \ge 2$ MeV and much larger than its alleged binding energy, $B_X =0.00(18)$MeV. On the other hand, there is a neat cancellation in the $1^{++} $ channel for the invariant $D {\bar D}^*$ mass around the threshold between the continuum and bound state contribution. We discuss the impact of this effect for X(3872) at finite temperature, in prompt production in pp collisions data with a finite $p_T$ or the lineshapes of specific production experiments of exotic states involving triangle singularities

hep-ph↗

arXiv2019

Quark-diquark models and baryonic fluctuations in QCD

We study the baryonic fluctuations of electric charge, baryon number and strangeness, by considering a realization of the Hadron Resonance Gas model in the light flavor sector of QCD. We elaborate on the idea that the susceptibilities can be saturated with excited baryonic states with a quark-diquark structure with a linearly confining interaction identical up to a constant to the quark-antiquark potential, $V_{qD}^\prime(r) = V_{q{\bar q}}^\prime(r)$. We obtain an overall good agreement with the spectrum obtained with other quark models and with lattice data for the fluctuations.

hep-ph↗

arXiv2019

Baryonic susceptibilities, quark-diquark models, and quark-hadron duality at finite temperature

Fluctuations of conserved charges such as baryon number, electric charge and strangeness may provide a test for completeness of states in lattice QCD for three light flavors. We elaborate on the idea that the corresponding susceptibilities can be saturated with excited baryonic states with an underlying quark-diquark structure with a linearly confining interaction. Using Polyakov-loop correlators we show that in the static limit, the quark-diquark potential coincides with the quark-antiquark potential in marked agreement with recent lattice studies. We thus study in a quark-diquark model the baryonic fluctuations of electric charge, baryon number and strangeness: $χ_{BQ}$, $χ_{BB}$ and $χ_{BS}$; by considering a realization of the hadron resonance gas model in the light flavor sector of QCD. These results have been obtained by using the baryon spectrum computed within a relativistic quark-diquark model, leading to an overall good agreement with the spectrum obtained with other quark models and with lattice data for the fluctuations.

hep-ph↗

arXiv2019

Fluctuations and correlations in thermal QCD

We study the equation of state, fluctuations and static correlators of electric charge, baryon number and strangeness, by considering a realization of the Hadron Resonance Gas model in the light flavor sector of QCD. We emphasize the importance of these observables to study, within this approach, the possible existence of exotic and missing states in the hadron spectrum. Some preliminary results for the baryon spectrum have been obtained within a relativistic quark-diquark model, leading to an overall good agreement with the spectrum obtained with other quark models. Finally, it is conjectured, within the Hadron Resonance Gas approach, the existence of a singularity in the correlators at zero temperature, which turns out to be analogous to the divergence of the partition function at the Hagedorn temperature.

hep-ph↗

arXiv2018

Thermal correlators in the hadron resonance gas: a dual Hagedorn distance

Fluctuations and correlations of conserved quantities in the confined phase of QCD are a viable way to characterize the existence of exotic and missing states with given quantum numbers in the hadronic spectrum. We study a realization of the Hadron Resonance Gas model in the light quark (uds) flavor sector of QCD to study the fluctuations and static correlators of electric charge, baryon number and strangeness. It is also conjectured an interesting duality between the correlators at zero temperature, and the fluctuations of integrated quantities at low temperatures, leading to the appearance of a dual Hagedorn distance for the former.

hep-ph↗

arXiv2018

Quasielastic charged-current neutrino scattering in the scaling model with relativistic effective mass

We use a recent scaling analysis of the quasielastic electron scattering data from $^{12}$C to predict the quasielastic charge-changing neutrino scattering cross sections within an uncertainty band. We use a scaling function extracted from a selection of the $(e,e')$ cross section data, and an effective nucleon mass inspired by the relativistic mean-field model of nuclear matter. The corresponding super-scaling analysis with relativistic effective mass (SuSAM*) describes a large amount of the electron data lying inside a phenomenological quasielastic band. The effective mass incorporates the enhancement of the transverse current produced by the relativistic mean field. The scaling function incorporates nuclear effects beyond the impulse approximation, in particular meson-exchange currents and short range correlations producing tails in the scaling function. Besides its simplicity, this model describes the neutrino data as reasonably well as other more sophisticated nuclear models.

nucl-th↗

arXiv2018

Low energy peripheral scaling in Nucleon-Nucleon Scattering and uncertainty quantification

We analyze the peripheral structure of the nucleon-nucleon interaction for LAB energies below 350 MeV. To this end we transform the scattering matrix into the impact parameter representation by analyzing the scaled phase shifts $(L+1/2) δ_{JLS} (p)$ and the scaled mixing parameters $(L+1/2)ε_{JLS}(p)$ in terms of the impact parameter $b=(L+1/2)/p$. According to the eikonal approximation, at large angular momentum $L$ these functions should become an universal function of $b$, {\it independent} on $L$. This allows to discuss in a rather transparent way the role of statistical and systematic uncertainties in the different long range components of the two-body potential. Implications for peripheral waves obtained in chiral perturbation theory interactions to fifth order (N5LO) or from the large body of NN data considered in the SAID partial wave analysis are also drawn from comparing them with other phenomenological high-quality interactions, constructed to fit scattering data as well. We find that both N5LO and SAID peripheral waves disagree more than $5 σ$ with the Granada-2013 statistical analysis, more than $ 2 σ$ with the 6 statistically equivalent potentials fitting the Granada-2013 database and about $1 σ$ with the historical set of 13 high-quality potentials developed since the 1993 Nijmegen analysis.

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arXiv2017

An exact solution to the Bertsch problem and the non-universality of the Unitary Fermi Gas

We analyze the universality of the Unitary Fermi Gas in its ground state from a Wilsonian renormalization point of view and compute the effective range dependence of the Bertsch parameter $ξ$ exactly. To this end we construct an effective block-diagonal two-body separable interaction with the Fermi momentum as a cut-off which reduces the calculation to the mean field level. The interaction is separable in momentum space and is determined by Tabakin's inverse scattering formula. For a vanishing effective range we get $ξ= \frac{176}{9 π}-\frac{17}{3} = 0.56$. By using phase-equivalent similarity transformations we can show that there is a class of exact solutions with any value in the range $ 0.56 \ge ξ\ge -1/3$.

cond-mat.quant-gas↗

arXiv2017

Fermi-momentum dependence of relativistic effective mass below saturation from superscaling of quasielastic electron scattering

The relativistic effective mass $M^*$, and Fermi momentum, $k_F$, are important ingredients in the determination of the nuclear equation of state, but they have rarely been extracted from experimental data below saturation density where translationally invariant nuclear matter becomes unstable against clusterization into the existing atomic nuclei. Using a novel kind of superscaling analysis of the quasielastic cross section electron scattering data involving a suitable selection criterion and $^{12}$C as a reference nucleus, the global scaling properties of the resulting set of data for 21 nuclei ranging from $^2$H to $^{238}$U are then analyzed. We find that a subset of a third of the about $20000$ data approximately scales to an universal superscaling function with a more constrained uncertainty band than just the reference $^{12}$C case and provides $M^*$ as a function of $k_F$.

nucl-th↗

arXiv2017

Excited Hadrons and Quark-Hadron Duality

We review how Quark-Hadron Duality (QHD) for (u,d) flavors at high energies and in the scaling regime suggests a radial and angular behaviour of mesonic and baryonic resonance masses of the Regge form $M^2_{nJ} = μ^2 n + β^2 J + M_0^2 $. The radial mass dependence is asymptotically consistent with a common two-body dynamics for mesons and baryons in terms of the quark-antiquark ($q \bar q)$ and quark-diquark ($qD$) degrees of freedom, respectively. This formula is validated phenomenologically within an uncertainty determined by half the width of the resonances, $ΔM_{nJ}^2 \sim Γ_{nJ} M_{nJ}$. With this error prescription we find from the non-strange PDG hadrons different radial slopes $μ^2_{\bar qq}=1.34(4) {\rm GeV}^2$ and $μ^2_{qD}=0.75(3) {\rm GeV}^2$, but similar angular slopes $β_{\bar q q}^2 \sim β_{ q D}^2 \sim 1.15 {\rm GeV}^2$.

hep-ph↗

arXiv2017

The BCS pairing gap in the on-shell limit of the Similarity Renormalization Group

The pairing gap plays a fundamental role in the nuclear many-body problem and many large scale and accurate mass formula fits suggest the smooth nuclear mass dependence $Δ\sim 6(1)~ A^{-1/3}~{\rm MeV}$ in the liquid drop model which lacks a theoretical motivation. Within the BCS theory we analyze the impact of phase equivalent interactions on the pairing gap for a translational invariant many-fermion system such as nuclear and neutron matter. To that end we use explicitly the Similarity Renormalization Group (SRG) transformations. We show that in the on-shell and continuum limits the pairing gap vanishes. For finite size systems the pairing gap can be computed directly from the scattering phase-shifts by the formula $$ Δ_{nn} (p_F) = Δε_F ~ δ^{^1S_0}_{nn}(p_F) /π~ , $$ where $p_F$ is the Fermi momentum and $Δε_F$ the level spacing at the Fermi energy which for the harmonic oscillator shell model becomes $Δε_F= \hbar ω\sim 41 ~ A^{-1/3}~{\rm MeV}$, so that $$ Δ_{nn} (p_F) \sim 4 ~ A^{-1/3}~{\rm MeV} ~ . $$ The comparison with double differences from binding energies of stable nuclei is satisfactory and the discrepancy with the large scale analysis may be attributed to the lack of three-body forces. Nevertheless, the on-shell two-body interaction provides a basis for the $c~A^{-1/3}$ dependency and accounts for 75\% of the coefficient $c$.

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