arXiv subjects

Luis Roca

Publications and source records attributed to Luis Roca.

11 recordsLinked to original sources

arXiv2026

Role of $a_0(1710)$ in the $J/ψ\toρ^+ρ^-ω$ and $J/ψ\toγρ^0ω$ reactions

We investigate the strong decay $J/ψ\toρ^+ρ^-ω$ and the radiative decay $J/ψ\toγρ^0ω$, taking into account the $S$-wave $K^*\bar{K}^*$, $ρω$ and $ρϕ$ final-state interactions, which dynamically generate the scalar meson $a_0(1710)$. Our results demonstrate that a clear peak structure emerges around 1.8~GeV in the $ρ^+ω$~($ρ^-ω$) invariant mass distribution of the strong decay, which can be associated with the $a_0(1710)$ resonance. Similarly, a distinct peak is predicted in the $ρ^0ω$ invariant mass distribution of the radiative decay. Our results indicate that clear signals of $a_0(1710)$ production could be observed in future measurements of these processes at BESIII, Belle II, and the planned Super Tau-Charm Facility, thereby helping to determine its mass and width more precisely.

hep-ph↗

arXiv2024

Pentaquark molecular states with hidden bottom and double strangeness

We investigate the meson-baryon interaction in coupled channels with the quantum numbers of the pentaquarks $P_{bss}$ and $P_{bsss}$. The interaction is derived from an extension of the local hidden gauge approach to the heavy quark sector, which has demonstrated accurate results compared to experiments involving $Ω_{b}$, $Ξ_{b}$ states, and pentaquarks $P_{c}$ and $P_{cs}$. In our study, we identify several molecular states with small decay widths within the chosen set of coupled channels. The spin-parity ($J^P$) of these states is as follows: $J^P={\frac{1}{2}}^-$ for pseudoscalar-baryon (${\frac{1}{2}}^+$) coupled channels, $J^P={\frac{3}{2}}^-$ for pseudoscalar-baryon (${\frac{3}{2}}^+$) coupled channels, $J^P={\frac{1}{2}}^-$ and ${\frac{3}{2}}^-$ for vector-baryon (${\frac{1}{2}}^+$) coupled channels, and $J^P={\frac{1}{2}}^-$, ${\frac{3}{2}}^-$, ${\frac{5}{2}}^-$ for vector-baryon (${\frac{3}{2}}^+$) coupled channels. We search for the poles of these states and evaluate their couplings to the different channels.

hep-ph↗

arXiv2023

Open-VERSO: a vision of 5G experimentation infrastructures, hurdles and challenges

5G led to a digital revolution for networks by leveraging virtualisation techniques to manage software-based network functions through provided standard interfaces, which have matured recently for cloud infrastructure that is widely employed across domains and sectors. This undiscovered potential to adequately respond to concurrent and specialised traffic demands is promising for a wide spectrum of industries. Moreover, it exposes the networking ecosystem to prospects beyond the traditional value chain. However, the configuration, deployment and operation of a 5G network are challenging. Thus, different scientific and research entities have built their own open, evolvable and updateable testbed infrastructure that can be used for experimentation purposes. Such testbeds enable different stakeholders to integrate new systems or features exploiting new technologies, assess the performance of innovative services, and customise operation policies to find optimal setups from a cost-effective perspective. Furthermore, federations of infrastructure allow for wider and more complex experiments to be performed in distributed domains. However, numerous technical and procedural obstacles exist during the building of 5G network testbeds. In addition, some technical barriers persist despite the testing of alternatives and ongoing efforts within open-source systems and commercial equipment portfolios. All these limitations and challenges are relevant for experimenters and stakeholders as they attempt to determine the scope of 5G set expectations.

cs.NI↗

arXiv2020

Signatures of the two $K_1(1270)$ poles in $D^+\to νe^+ V P$ decay

We analyze theoretically the $D^+\to νe^+ ρ\bar K$ and $D^+\to νe^+ \bar K^* π$ decays to see the feasibility to check the double pole nature of the axial-vector resonance $K_1(1270)$ predicted by the unitary extensions of chiral perturbation theory (UChPT). Indeed, within UChPT the $K_1(1270)$ is dynamically generated from the interaction of a vector and a pseudoscalar meson, and two poles are obtained for the quantum numbers of this resonance. The lower mass pole couples dominantly to $K^*π$ and the higher mass pole to $ρK$, therefore we can expect that different reactions weighing differently these channels in the production mechanisms enhance one or the other pole. We show that the different final $VP$ channels in $D^+\to νe^+ V P$ weigh differently both poles, and this is reflected in the shape of the final vector-pseudoscalar invariant mass distributions. Therefore, we conclude that these decays are suitable to distinguish experimentally the predicted double pole of the $K_1(1270)$ resonance.

hep-ph↗

arXiv2016

Weak decays of heavy hadrons into dynamically generated resonances

In this review we give a perspective of the theoretical work done recently on the interpretation of results from $B$, $D$, $Λ_b$, $Λ_c$ weak decays into final states that contain interacting hadrons, and how it is possible to obtain additional valuable information that is increasing our understanding of hadron interactions and the nature of many hadronic resonances. The novelty of these processes is that one begins with a clean picture at the quark level which allows one to select the basic mechanisms by means of which the process proceeds. Finally, one has a final state described in terms of quarks. To make contact with the experiments, where mesons and baryons are observed, one must hadronize, creating pairs of $q \bar q$ and writing the new states in terms of mesons and baryons. This concludes the primary hadron production in these processes. After that, the interaction of these hadrons takes place, offering a rich spectrum of resonances and special features from where it is possible to learn much about the interaction of these hadrons and the nature of many resonances in terms of the components of their wave functions.

hep-ph↗

arXiv2015

Predictions for the $Λ_b \to J/ψ~ Λ(1405)$ decay

We calculate the shape of the $πΣ$ and $\bar K N$ invariant mass distributions in the $Λ_b \to J/ψ\, πΣ$ and $Λ_b \to J/ψ\,\bar K N$ decays that are dominated by the $Λ(1405)$ resonance. The weak interaction part is the same for both processes and the hadronization into the different meson-baryon channels in the final state is related by SU(3) symmetry. The most important feature is the implementation of the meson-baryon final-state interaction using two chiral unitary models from different theoretical groups. Both approaches give a good description of antikaon-nucleon scattering data, the complex energy shift in kaonic hydrogen and the line shapes of $πΣK$ in photoproduction, based on the two-pole scenario for the $Λ(1405)$. We find that this reaction reflects more the higher mass pole and we make predictions of the line shapes and relative strength of the meson-baryon distributions in the final state.

hep-ph↗

arXiv2008

Structure of the Lambda(1405) baryon resonance from its large Nc behavior

We study the behavior with the number of colors (Nc) of the two poles associated to the Lambda(1405) resonance obtained dynamically within the chiral unitary approach. The leading order chiral meson-baryon interaction manifests a nontrivial Nc dependence for SU(3) baryons, which gives a finite attractive interaction in some channels in the large Nc limit. As a consequence, the SU(3) singlet (Kbar N) component of the Lambda(1405) survives in the large Nc limit as a bound state, while the other components dissolve into the continuum. The Nc dependence of the decay widths shows different behavior from the general counting rule for a qqq state, indicating the dynamical origin of the two poles for the Lambda(1405) resonance.

hep-ph↗

arXiv2008

Lambda(1405) in chiral SU(3) dynamics

We discuss several aspects of the Lambda(1405) resonance in relation to the recent theoretical developments in chiral dynamics. We derive an effective single-channel KbarK N interaction based on chiral SU(3) coupled-channel approach, emphasizing the important role of the pi Sigma channel and the structure of the Lambda(1405) in Kbar N phenomenology. In order to clarify the structure of the resonance, we study the behavior with the number of colors (Nc) of the poles associated with the Lambda(1405), and argue the physical meaning of the renormalization procedure.

hep-ph↗

arXiv2007

Non-Perturbative Study of the Light Pseudoscalar Masses in Chiral Dynamics

We perform a non-perturbative chiral study of the masses of the lightest pseudoscalar mesons. In the calculation of the self-energies we employ the S-wave meson-meson amplitudes taken from Unitary Chiral Perturbation Theory (UCHPT) that include the lightest nonet of scalar resonances. Values for the bare masses of pions and kaons are obtained, as well as an estimate of the mass of the η_8. The former are found to dominate the physical pseudoscalar masses. We then match to the self-energies from Chiral Perturbation Theory (CHPT) to O(p^4), and a robust relation between several O(p^4) CHPT counterterms is obtained. We also resum higher orders from our calculated self-energies. By taking into account values determined from previous chiral phenomenological studies of m_s/\hat{m} and 3L_7+L^r_8, we determine a tighter region of favoured values for the O(p^4) CHPT counterterms 2L^r_6-L^r_4 and 2L^r_8-L^r_5. This determination perfectly overlaps with the recent determinations to O(p^6) in CHPT. We warn about a likely reduction in the value of m_s/\hat{m} by higher loop diagrams and that this is not systematically accounted for by present lattice extrapolations. We also provide a favoured interval of values for m_s/\hat{m} and 3L_7+L^r_8.

hep-ph↗

arXiv2007

Improved dispersion relations for γγ\to π^0π^0

We perform a dispersive theoretical study of the reaction γγ\to pi^0π^0 emphasizing the low energy region. The large source of theoretical uncertainty to calculate the γγ\toπ^0π^0 total cross section for \sqrt{s}\gtrsim 0.5 GeV within the dispersive approach is removed. This is accomplished by taking one more subtraction in the dispersion relations, where the extra subtraction constant is fixed by considering new low energy constraints, one of them further refined by taking into consideration the f_0(980) region. This allows us to make sharper predictions for the cross section for \sqrt{s}\lesssim 0.8 GeV, below the onset of D-wave contributions. In this way, were new more precise data on γγ\toπ^0π^0 available one might then distinguish between different parameterizations of the ππisoscalar S-wave. We also elaborate on the width of the σresonance to γγand provide new values.

hep-ph↗

arXiv2007

Scalar radius of the pion and zeros in the form factor

The quadratic pion scalar radius, \la r^2\ra^π_s, plays an important role for present precise determinations of ππscattering. Recently, Ynduráin, using an Omnès representation of the null isospin(I) non-strange pion scalar form factor, obtains \la r^2\ra^π_s=0.75\pm 0.07 fm^2. This value is larger than the one calculated by solving the corresponding Muskhelishvili-Omnès equations, \la r^2\ra^π_s=0.61\pm 0.04 fm^2. A large discrepancy between both values, given the precision, then results. We reanalyze Ynduráin's method and show that by imposing continuity of the resulting pion scalar form factor under tiny changes in the input ππphase shifts, a zero in the form factor for some S-wave I=0 T-matrices is then required. Once this is accounted for, the resulting value is \la r^2\ra_s^π=0.65\pm 0.05 fm^2. The main source of error in our determination is present experimental uncertainties in low energy S-wave I=0 ππphase shifts. Another important contribution to our error is the not yet settled asymptotic behaviour of the phase of the scalar form factor from QCD.

hep-ph↗