arXiv subjects

Miguel Albaladejo

Publications and source records attributed to Miguel Albaladejo.

36 records · Page 2Linked to original sources

arXiv2022

Novel approaches in Hadron Spectroscopy

The last two decades have witnessed the discovery of a myriad of new and unexpected hadrons. The future holds more surprises for us, thanks to new-generation experiments. Understanding the signals and determining the properties of the states requires a parallel theoretical effort. To make full use of available and forthcoming data, a careful amplitude modeling is required, together with a sound treatment of the statistical uncertainties, and a systematic survey of the model dependencies. We review the contributions made by the Joint Physics Analysis Center to the field of hadron spectroscopy.

hep-ph↗

arXiv2022

A combined analysis of the $Z_c(3900)$ and the $Z_{cs}(3985)$ exotic states

We have performed a combined analysis of the BESIII data for both the $Z_c(3900)$ and $Z_{cs}(3985)$ structures, assuming that the latter is an SU(3) flavor partner of the former one. We have improved on the previous analysis of Albaladejo $et$ $al.$ [Phys. Lett. B 755, 337 (2016)] by computing the amplitude for the $D_1\bar{D}D^*$ triangle diagram considering both $D$ and $S$-wave $D_1D^*π$ couplings. We have also investigated effects from SU(3) light-flavor violations, which are found to be moderate and of the order of 20%. The successful reproduction of the BESIII spectra, in both the hidden-charm and hidden-charm strange sectors, strongly supports that the $Z_{cs}(3985)$ and $Z_c(3900)$ are SU(3) flavor partners placed in the same octet multiplet. The best results are obtained when an energy-dependent term in the diagonal $D^{(*)}\bar D_{(s)}^{(*)}$ interaction is included, leading to resonances (poles above the thresholds) to describe these exotic states. We have also made predictions for the isovector $Z_{c}^*$ and isodoublet $Z_{cs}^*$, $D^*\bar{D}^*$ and $D^*\bar{D}_{s}^*$ molecules, with $J^{PC}=1^{+-}$ and $J^{P}=1^{+}$, respectively. These states would be heavy-quark spin symmetry partners of the $Z_{c}$ and $Z_{cs}$. Besides the determination of the masses and widths of the $Z_c(3900)$ and $Z_{cs}(3985)$, we also predict those of the $Z_c^*$ and $Z_{cs}^*$ resonances.

hep-ph↗

arXiv2022

Hadron Spectroscopy in Photoproduction

Recent decades have seen a resurge of interest in hadron spectroscopy, driven by new, high-luminosity experiments which have identified many new hadrons, both expected and unexpected. The large number of unexpected hadrons suggest contributions from additional quark and gluonic degrees of freedom to the hadronic spectrum beyond the basic quark model. Photoproduction has emerged as an attractive process to study hadron spectroscopy, due to the range of states accessible in new and planned experimental facilities, complimentary kinematics to other experiments where rescattering effects near thresholds are reduced, and advances in our theoretical understanding of these reactions. This white paper reviews the prospects for hadron spectroscopy from three major existing and proposed facilities: the current GlueX experiment, the planned Electron-Ion Collider, and a proposed JLab 24 GeV upgrade.

hep-ex↗

arXiv2022

Snowmass white paper: Need for amplitude analysis in the discovery of new hadrons

We highlight the need for the development of comprehensive amplitude analysis methods to further our understanding of hadron spectroscopy. Reaction amplitudes constrained by first principles of $S$-matrix theory and by QCD phenomenology are needed to extract robust interpretations of the data from experiments and from lattice calculations.

hep-ph↗

arXiv2019

Double Polarization Observables in Pentaquark Photoproduction

We investigate the properties of the hidden charm pentaquark-like resonances first observed by LHCb in 2015, by measuring the polarization transfer KLL between the incident photon and the outgoing proton in the exclusive photoproduction of J/psi near threshold. We present a first estimate of the sensitivity of this observable to the pentaquark photocouplings and hadronic branching ratios, and extend our predictions to the case of initial state helicity correlation ALL, using a polarized target. These results serve as a benchmark for the SBS experiment at Jefferson Lab, which proposes to measure for the first time the helicity correlations ALL and KLL in J/psi exclusive photoproduction, in order to determine the pentaquark photocouplings and branching ratios.

hep-ph↗

arXiv2018

Towards a new paradigm for heavy-light meson spectroscopy

Since 2003 many new hadrons, including the lowest-lying positive-parity charm-strange mesons ${D_{s0}^*(2317)}$ and ${D_{s1}(2460)}$, were observed that do not conform with quark model expectations. It was recently demonstrated that various puzzles in the charm meson spectrum find a natural resolution, if the SU(3) multiplets for the lightest scalar and axial-vector states, amongst them the ${D_{s0}^*(2317)}$ and the ${D_{s1}(2460)}$, owe their existence to the nonperturbative dynamics of Goldstone-Boson scattering off $D_{(s)}$ and $D^*_{(s)}$ mesons. Most importantly the ordering of the lightest strange and nonstrange scalars becomes natural. In this work we demonstrate for the first time that this mechanism is strongly supported by the recent high quality data on the ${B^-\to D^+π^-π^- }$ provided by the LHCb experiment. This implies that the lowest quark-model positive-parity charm mesons, together with their bottom counterparts, if realized in nature, do not form the ground-state multiplet. This is similar to the pattern that has been established for the scalar mesons made from light up, down and strange quarks, where the lowest multiplet is considered to be made of states not described by the quark model. In a broader view, the hadron spectrum must be viewed as more than a collection of quark model states.

hep-ph↗

arXiv2017

Scalar form factors of semi-leptonic $D\toπ/ \bar{K}$ transitions with coupled-channel effects

Coupled-channel effects are taken into account for the study of scalar form factors in semi-leptonic $D\toπ\bar{\ell}ν_\ell$ and $D\to \bar{K}\bar{\ell}ν_\ell$ decays, by solving the Muskhelishvili-Omnès integral equations. As inputs, we employ the unitarized amplitudes taken from chiral effective theory for the region not far away from thresholds, while, at higher energies of the Goldstone bosons, proper asymptotic conditions are employed. Within Muskhelishvili-Omnès formalism, the scalar form factors are represented in terms of Omnès matrix multiplied by a vector of polynomials. We reduce the number of subtraction constants by matching to the scalar form factors derived in chiral perturbation theory up to next-to-leading order. The recent lattice QCD data by ETM collaboration for ${D\toπ}$ and ${D\to\bar{K}}$ scalar form factors are simultaneously well described. The scalar form factors for $D\toη$, $D_s\to \bar{K}$ and $D_s\to η$ transitions are predicted in their whole kinematical regions. Using our fitting parameters, we also extract the following Cabibbo-Kobayashi-Maskawa elements: $|V_{cd}|=0.243(_{-12}^{+11})_{\rm sta.}({3})_{\rm sys.}(3)_{\rm exp.}$ and $|V_{cs}|=0.950(_{-40}^{+39})_{\rm sta.}(1)_{\rm sys.}(7)_{\rm exp.}$. The approach used in this work can be straightforwardly extended to the semileptonic $B$ decays.

hep-ph↗

arXiv2017

Note on X(3872) production at hadron colliders and its molecular structure

The production of the X(3872) as a hadronic molecule in hadron colliders is clarified. We show that the conclusion of Bignamini et al., Phys. Rev. Lett. 103 (2009) 162001, that the production of the X(3872) at high $p_T$ implies a non-molecular structure, does not hold. In particular, using the well understood properties of the deuteron wave function as an example, we identify the relevant scales in the production process.

hep-ph↗

arXiv2017

Lowest lying even-parity $\bar B_s$ mesons: heavy quark spin-flavor symmetry, chiral dynamics, and constituent quark model bare masses

The discovery of the $D^\ast_{s0}(2317)$ and $D_{s1}(2460)$ resonances in the charmed-strange meson spectra revealed that formerly successful constituent quark models lose predictability in the vicinity of two-meson thresholds. The emergence of non-negligible effects due to meson loops requires an explicit evaluation of the interplay between $Q\bar q$ and $(Q\bar q)(q\bar q)$ Fock components. In contrast to the $c\bar s$ sector, there is no experimental evidence of $J^P=0^+,1^+$ bottom-strange states yet. Motivated by recent lattice studies, in this work the heavy-quark partners of the $D_{s0}^\ast(2317)$ and $D_{s1}(2460)$ states are analyzed within a heavy meson chiral unitary scheme. As a novelty, the coupling between the constituent quark model P-wave $\bar B_s$ scalar and axial mesons and the $\bar B^{(\ast)}K$ channels is incorporated employing an effective interaction, consistent with heavy quark spin symmetry, constrained by the lattice energy levels.

hep-ph↗

arXiv2016

Two-pole structure of the $D^\ast_0(2400)$

The so far only known charmed non-strange scalar meson is dubbed as $D_0^*(2400)$ in the Review of Particle Physics. We show, within the framework of unitarized chiral perturbation theory, that there are in fact two $(I=1/2, J^P=0^+)$ poles in the region of the $D_0^*(2400)$ in the coupled-channel $Dπ$, $Dη$ and $D_s\bar K$ scattering amplitudes. With all the parameters previously fixed, we predict the energy levels for the coupled-channel system in a finite volume, and find that they agree remarkably well with recent lattice QCD calculations. This successful description of the lattice data is regarded as a strong evidence for the two-pole structure of the $D_0^*(2400)$. With the physical quark masses, the poles are located at $\left(2105^{+6}_{-8}-i\,102^{+10}_{-12}\right)$~MeV and $\left(2451^{+36}_{-26}-i\,134^{+7}_{-8}\right)$~MeV, with the largest couplings to the $Dπ$ and $D_s\bar K$ channels, respectively. Since the higher pole is close to the $D_s\bar K$ threshold, we expect it to show up as a threshold enhancement in the $D_s\bar K$ invariant mass distribution. This could be checked by high-statistic data in future experiments. We also show that the lower pole belongs to the same SU(3) multiplet as the $D_{s0}^*(2317)$ state. Predictions for partners in the bottom sector are also given.

hep-ph↗

arXiv2016

$D^\ast_{s0}(2317)$ and $DK$ scattering in $B$ decays from BaBar and LHCb data

We study the experimental $DK$ invariant mass spectra of the reactions $B^+ \to \bar{D}^0 D^0 K^+$, $B^0 \to D^- D^0 K^+$ (measured by the BaBar Collaboration) and $B_s \to π^+ \bar{D}^0 K^-$ (measured by the LHCb Collaboration), where an enhancement right above the threshold is seen. We show that this enhancement is due to the presence of $D^\ast_{s0}(2317)$, which is a $DK$ bound state in the $I(J^P) = 0(0^+)$ sector. We employ a unitarized amplitude with an interaction potential fixed by heavy meson chiral perturbation theory. We obtain a mass $M_{D^\ast_{s0}} = 2315^{+12}_{-17}\ ^{+10}_{-5}\ \text{MeV}$, and we also show, by means of the Weinberg compositeness condition, that the $DK$ component in the wave function of this state is $P_{DK} = 70^{+4}_{-6}\ ^{+4}_{-8} \%$, where the first (second) error is statistical (systematic).

hep-ph↗

arXiv2016

Can $X(5568)$ be described as a $B_sπ$, $B\bar{K}$ resonant state?

The D0 Collaboration has recently seen a resonant-like peak in the $B_sπ$ invariant mass spectrum, claimed to be a new state called $X(5568)$. Using a $B_sπ$--$B\bar{K}$ coupled channel analysis, implementing unitarity, and with the interaction derived from Heavy Meson Chiral Perturbation Theory, we are able to reproduce the reported spectrum, with a pole that can be associated to the claimed $X(5568)$ state, and with mass and width in agreement with the ones reported in the experimental analysis. However, if the $T$-matrix regularization is performed by means of a momentum cutoff, the value for the latter needed to reproduce the spectrum is $Λ= 2.80 \pm 0.04\ \text{GeV}$, much larger than a "natural" value $Λ\simeq 1\ \text{GeV}$. In view of this, it is difficult to interpret the nature of this new state. This state would not qualify as a resonance dynamically generated by the unitarity loops. Assuming the observed peak to correspond to a physical state, we make predictions for partners in the $D$, $D^\ast$, and $B^\ast$ sectors. Their observation (or lack thereof) would shed light into this issue.

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

$Z_c(3900)$: what has been really seen?

The $Z^\pm_c(3900)/Z^\pm_c(3885)$ resonant structure has been experimentally observed in the $Y(4260) \to J/ψππ$ and $Y(4260) \to \bar{D}^\ast D π$ decays. This structure is intriguing since it is a prominent candidate of an exotic hadron. Yet, its nature is unclear so far. In this work, we simultaneously describe the $\bar{D}^\ast D$ and $J/ψπ$ invariant mass distributions in which the $Z_c$ peak is seen using amplitudes with exact unitarity. Two different scenarios are statistically acceptable, where the origin of the $Z_c$ state is different. They correspond to using energy dependent or independent $\bar D^* D$ $S$-wave interaction. In the first one, the $Z_c$ peak is due to a resonance with a mass around the $D\bar D^*$ threshold. In the second one, the $Z_c$ peak is produced by a virtual state which must have a hadronic molecular nature. In both cases the two observations, $Z^\pm_c(3900)$ and $Z^\pm_c(3885)$, are shown to have the same common origin, and a $\bar D^* D$ bound state solution is not allowed. Precise measurements of the line shapes around the $D\bar D^*$ threshold are called for in order to understand the nature of this state.

hep-ph↗

arXiv2015

$D_{s0}^{\ast\pm}(2317)$ and $KD$ scattering from $B^0_s$ decay

We study the $\bar{B}_s^0\to D_s^-(DK)^+$ weak decay, and look at the $DK$ invariant mass distribution with the aim of obtaining relevant information on the nature of the $D_{s0}^{\ast+}(2317)$ resonance. We make a simulation of the experiment using the actual mass of the $D_{s0}^{\ast+}(2317)$ resonance and recent lattice QCD relevant parameters of the $KD$ scattering amplitude. We then solve the inverse problem of obtaining the $KD$ amplitude from these synthetic data, to which we have added a 5\% or 10\% error. We prove that one can obtain from these "data" the existence of a bound $KD$ state, the $KD$ scattering length and effective range, and most importantly, the $KD$ probability in the wave function of the bound state obtained, which was found to be largely dominant from the lattice QCD results. This means that one can obtain information on the nature of the $D_{s0}^{\ast+}(2317)$ resonance from the implementation of this experiment, in the line of finding the structure of resonances, which is one of the main aims in hadron spectroscopy.

hep-ph↗

arXiv2013

Constraints on a possible dibaryon from combined analysis of the $pn \to d π^+ π^-$ and $pn \to pn π^+ π^-$ cross sections

We use recent data that show a narrow peak around $\sqrt{s}=2.37\ \text{GeV}$ in the $pn \to d π^+ π^-$ cross section, with about double strength at the peak than in the analogous $pn \to d π^0 π^0$ reaction, and, assuming that it is due to the excitation of a dibaryon resonance, we evaluate the cross section for the $pn \to pn π^+ π^-$ reaction, with the final $pn$ unbound but with the same quantum numbers as the deuteron. We use accurate techniques to determine the final state interaction in the case of the $pn$ forming a deuteron or a positive energy state, which allow us to get the $pn \to pn π^+ π^-$ cross section with $pn$ in I=0 and S=1, that turns out to be quite close or saturates the experimental $pn \to pn π^+ π^-$ total cross section around $\sqrt{s} = 2.37\ \text{GeV}$, depending on the angular momentum assumed. We then parametrize a background with different methods, and the sum of the resonant and background contributions is fitted to present data. The resulting cross section exceeds the experimental results in the region of the resonant peak, showing a problem in the dibaryon hypothesis. Yet, in view of the dispersion of present experimental data, and the scarce information around $\sqrt{s} = 2.37\ \text{GeV}$, a call is made for precise measurements of the $pn \to pnπ^+π^-$ reaction around this energy, to further clarify this issue.

nucl-th↗

arXiv2013

Hidden charm molecules in finite volume

In the present paper we address the interaction of pairs of charmed mesons with hidden charm in a finite box. We use the interaction from a recent model based on heavy quark spin symmetry that predicts molecules of hidden charm in the infinite volume. The energy levels in the box are generated within this model, and from them some synthetic data are generated. These data are then employed to study the inverse problem of getting the energies of the bound states and phase shifts for $D \bar D$ or $D^* {\bar D}^*$. Different strategies are investigated using the lowest two levels for different values of the box size, carrying a study of the errors produced. Starting from the upper level, fits to the synthetic data are carried out to determine the scattering length and effective range plus the binding energy of the ground state. A similar strategy using the effective range formula is considered with a simultaneous fit to the two levels, one above and the other one below threshold. This method turns out to be more efficient than the other one. Finally, a method based on the fit to the data by means of a potential and a loop function conveniently regularized, turns out to be very efficient and allows to produce accurate results in the infinite volume starting from levels of the box with errors far larger than the uncertainties obtained in the final results. A regularization method based on Gaussian wave functions turns out to be rather efficient in the analysis and as a byproduct a practical and fast method to calculate the Lüscher function with high precision is presented.

hep-lat↗

arXiv2007

S-wave meson scattering up to sqrt{s} < 2 GeV from chiral Lagrangians

The problem of scalar mesons still remains a challenging puzzle, for which we do not even know which are the right pieces to set up. The proliferation of resonances (some of them are very broad and appear on top of hadronic thresholds) and of coupled channels that interact strongly among each other makes the study of this sector a hard task. Our objective is the study of the strongly interacting mesons in coupled channels with quantum numbers J^{PC} = 0^{++} and I=0 and I=1/2, up to a center of mass energy sqrt{s} < 2 GeV. Our framework is based on Unitary Chiral Perturbation Theory. We include for I=0 the channels: ππ, K\bar{K}, ηη, σσ, ηη', ρρ, ωω, η'η', ωϕ, ϕϕ, K^\ast \bar{K}^\ast, a_1(1260)πand π^{\star}(1300)π. In addition, and in order to constrain our fits, we also study the I=1/2, 3/2 channels given by Kπ, Kηand Kη'. We finally present the resonant content of our fits with the $σ$, $f_0(980)$, $f_0(1310)$, $f_(1500)$, $f_0(1710)$ and $f_0(1790)$.

hep-ph↗