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E. Santopinto

Publications and source records attributed to E. Santopinto.

At least 19 recordsLinked to original sources

Radiative decays of the 1$P$, 1$D$, 2$S$, and 2$P$ $\Lambda_c$ and 1$D$, 2$S$, and 2$P$ $\Xi_c$ charmed baryons

We analyze the radiative decays of the the 1$P$, 1$D$, 2$S$, and 2$P$ $\Lambda_c$ and 1$D$, 2$S$, and 2$P$ $\Xi_c$ charmed baryons, which belong to the flavor anti-triplet ($\bf {\bar 3}_{\rm F}$), using the constituent quark model. We compute electromagnetic transitions from ground and $P$-wave states to ground states, as well as from second-shell states to both ground and $P$-wave final states. Electromagnetic decay widths are especially valuable for identifying resonances when multiple states share the same mass and total decay width. We give branching ratios which can confirm the assignment of the $\Xi_c(3055)$ reported by LHCb. We also give branching ratios that can support the assignment of the $\Xi_c(3080)$, and discuss the possibilities for the $\Xi_c(3080)$ to be the 1$D$ state with $J^P=5/2^{+}$ or the 2$S$ with $J^P=1/2^{+}$. For the first time, this work provides calculations of electromagnetic decays for $D_\rho$-wave states, $\rho-\lambda$ mixed configurations, and $\rho$-mode radially excited states in singly charmed baryons of the flavor anti-triplet. Both experimental and model-dependent uncertainties are taken into account throughout our analysis.

hep-ph

Radiative decays of the $Σ_c$, $Ξ'_c$ and $Ω_c$ charmed baryons

In this work, we study the radiative decays of the $Σ_c$, $Ξ'_c$ and $Ω_c$ charmed baryons, which belong to the flavor sextet ($\bf {6}_{\rm F}$), within the constituent quark model formalism. The electromagnetic transitions are calculated from the ground and $P$-wave states to ground states, as well as from the second shell states to both the ground and $P$-wave final states. These decays play a crucial role in confirming the existence of certain resonances when strong decays are not allowed. Moreover, electromagnetic decay widths are particularly useful for identifying resonances when states have the same mass and total decay width. A relevant case is the $Ω_c (3327)$ state, whose branching ratios between the strong decay channels are comparable; thus, the radiative decay widths may help assign this state. We also make the assignment of the recently discovered $Ξ'_c(2923)^{+}$ baryon, which is consistent with being the isospin partner of the $Ξ'_c(2923)^{0}$. This study presents, for the first time, the calculation of electromagnetic decays for $D_ρ$-wave states, $ρ-λ$ mixed states, and $ρ$-mode radially excited states in the charm sector. Throughout our calculations, we account for uncertainties arising from both experimental and model-dependent errors.

hep-ph

Radiative decays of the second shell $Λ_b$ and $Ξ_b$ bottom baryons

In this work, we investigate the radiative decays of the $Λ_b$ and $Ξ_b$ bottom baryons, which belong to the flavor anti-triplet ($\mathbf{\bar{3}}_{\rm F}$), within the constituent quark model formalism. The electromagnetic transitions are calculated from the second-shell states to both the ground and $P$-wave final states. These decays play a crucial role in confirming the existence of certain resonances. When strong decays are not allowed, the reconstruction of states relies on their electromagnetic decay channels. Moreover, electromagnetic decay widths are particularly useful for the identification of resonances when states have the same mass and total decay width. This study presents, for the first time, the calculation of electromagnetic decays for $D_ρ$-wave states, $ρ-λ$ mixed states, and $ρ$-mode radially excited states. Throughout our calculations, we account for uncertainties arising from both experimental and model-dependent errors.

hep-ph

$Ξ_c(2790)^{+/0}$ and $Ξ_c(2815)^{+/0}$ radiative decays

In this work, we study the $Ξ_c$ baryon electromagnetic decay widths within the constituent quark model formalism through an analysis of the transitions from $P-$wave states to ground states. We use the non-relativistic limit of the Hamiltonian of the electromagnetic interaction on keeping all the terms up to the order $m_j^{-1}$. We calculate the electromagnetic decay widths analytically, for the first time, without any further approximation. Specifically, our theoretical results for the $Ξ_c(2790)^{+/0}$ and $Ξ_c(2815)^{+/0}$ radiative decay widths, without the introduction of any additional parameters, display a significant agreement with the recent experimental values obtained by the Belle experiment. The agreement is due to the fact that we have not introduced further approximation to simplify the calculation of the difficult convective term, unlike what was done in previous studies. Our predictions may be useful for future experiments at the Belle, BABAR, and LHC experiments.

hep-ph

Mini-Proceedings of the "Fourth International Workshop on the Extension Project for the J-PARC Hadron Experimental Facility (HEF-ex 2024)"

The mini proceedings of the "Fourth International Workshop on the Extension Project for the J-PARC Hadron Experimental Facility (HEF-ex 2024) [https://kds.kek.jp/event/46965]" held at J-PARC, February 19-21, 2024, are presented. The workshop was devoted to discussing the physics case that connects both the present and the future Hadron Experimental Facility at J-PARC, covering a wide range of topics in flavor, hadron, and nuclear physics related to both experimental and theoretical activities being conducted at the facility.

nucl-ex

Decay widths and mass spectra of single bottom baryons

We develop a Hamiltonian model that incorporates the spin, spin-orbit, and isospin interactions to determine the masses of the ground states of single-bottom baryons and their excitations up to the $D$-wave. Furthermore, we calculate the strong decay widths of single-bottom baryons using the $^3P_0$ model. Our calculations consider final states comprising bottom baryon-(vector/pseudoscalar) meson pairs and (octet/decuplet) baryon-(pseudoscalar/vector) bottom meson pairs within a constituent quark model. In that respect, this is the most complete investigation which has ever been performed in the single bottom baryon sector so far. Additionally, we compute the electromagnetic decay widths from $P$-wave states to ground states. The electromagnetic decays become dominant in cases where the strong decays are suppressed. The experimental uncertainties are propagated to the model parameters using a Monte Carlo bootstrap method. Our quantum number assignments, as well as our mass and strong decay width predictions, are in reasonable agreement with the available data. We also provide the partial decay widths for each open flavor channel. Our predictions of mass spectra and decay widths provide valuable information for the experiments seeking to identify new bottom baryons and knowledge of possible decay channels can aid in their identification in the data. Therefore, our results will be able to guide future searches for the undiscovered single bottom baryons at LHCb, ATLAS, and CMS.

hep-ph

Strong decay widths and mass spectra of charmed baryons

The total decay widths of the charmed baryons are calculated by means of the $^3P_0$ model. Our calculations consider in the final states: the charmed baryon-(vector/pseudoscalar) meson pairs and the (octet/ decuplet) baryon-(pseudoscalar/vector) charmed meson pairs, within a constituent quark model. Furthermore, we calculate the masses of the charmed baryon ground states and their excitations up to the $D$-wave in a constituent quark model both in the three-quark and in the quark-diquark schemes, utilizing a Hamiltonian model based on a harmonic oscillator potential plus a mass splitting term that encodes the spin, \mbox{spin-orbit}, isospin, and flavor interactions. The parameters of the Hamiltonian model are fitted to the experimental data of the charmed baryon masses and decay widths. As the experimental uncertainties of the data affect the fitted model parameters, we have thoroughly propagated these uncertainties into our predicted charmed baryon masses and decay widths via a Monte Carlo bootstrap approach, which is often absent in other theoretical studies on this subject. Our quantum number assignments and predictions of the masses and strong partial decay widths are in reasonable agreement with the available data. Thus, our results show the ability to guide future measurements in LHCb, Belle and Belle II experiments. Finally, the appendices provide some details of our calculations, in which we include the flavor coupling coefficients, which are useful for further theoretical investigations.

hep-ph

$0^+$ to $2^+$ neutrinoless double-$β$ decay of $^{76}$Ge, $^{82}$Se, $^{130}$Te and $^{136}$Xe in the microscopic interacting boson model}

Here, we study the neutrinoless double-$β$ ($0νββ$) decay between the ground state and the first $2^+$ state of $^{76}\mbox{Ge} \rightarrow {}^{76}\mbox{Se}$, $^{82}\mbox{Se} \rightarrow{}^{82}\mbox{Kr}$, $^{130}\mbox{Te} \rightarrow {}^{130}\mbox{Xe}$ and $^{136}\mbox{Xe} \rightarrow {}^{136}\mbox{Ba}$ systems. The relevant nuclear matrix elements (NMEs) involved in the process are calculated within the formalism of the microscopic interacting boson model (IBM-2). The IBM-2 has been widely used to obtain predictions for nuclear observables, such as the spectrum, but also to explore the possible emergence of beyond-the-Standard Model effects in the weak interactions of nuclei. Our calculations are carried out by considering the exchange of a Majorana neutrino between two nucleons ($2N$-mechanism). In addition to NMEs, we calculate the associated leptonic phase-space factors (PSFs) using electron radial wave functions, which are obtained by solving numerically the Dirac equation of a screened Coulomb potential that takes into account finite nuclear size. By combining our IBM-2 results for the NMEs with those for the PSFs along with experimental half-life limits, we can set limits on the $\langle λ\rangle$ and $\langle η\rangle$ couplings of left-right (L-R) models.

nucl-th

Summary of Topical Group on Hadron Spectroscopy (RF07) Rare Processes and Precision Frontier of Snowmass 2021

Hadron spectroscopy, the driving force of high-energy physics in its early decades, has experienced a renaissance in interest over the past 20 years due to the discovery of scores of new, potentially "exotic states" (tetraquarks, pentaquarks, hybrid mesons, glueballs), as well as the observation of many new "conventional" hadrons. The new discoveries expose our lack of understanding about hadronic states, beyond just a few low excitations of the simplest quark configurations. Even so, no single theoretical interpretation (such as hadron molecules, threshold effects, diquark compounds, or others) as yet successfully accommodates all of the new multiquark particles, while a great deal of work remains to extract signals of hybrids and glueballs from reaction-amplitude data. This document summarizes the current state of the field from both experimental and theoretical perspectives. On the experimental side, this report summarizes the current, planned, and proposed activities of LHCb and other LHC experiments, Belle II, BESIII, and GlueX, as well as the approved Electron-Ion Collider, the proposed Super Tau-Charm factory, and other future experiments. The theoretical portion provides a brief overview of multiple phenomenological approaches studied to date, progress in rigorous studies of reaction amplitudes, and advances in lattice-QCD simulations.

hep-ph

The new $P_{\rm cs}(4459)$, $Z_{\rm cs}(3985)$, $Z_{\rm cs}(4000)$ and $Z_{\rm cs}(4220)$ and the possible emergence of flavor pentaquark octets and tetraquark nonets

Our hadro-charmonium and compact tetraquark model predictions, published before the BESIII and LHCb experimental data for the $Z_{\rm cs}(3985)$ and $Z_{\rm cs}(4003)$ tetraquarks were released, match surprisingly well with them. Here, we extend our results for the $P_{\rm cs}$ states to $Λ$ + charmonium configurations and also our hadro-charmonium predictions for $Z_{\rm c}$ and $X_{\rm c}$ tetraquarks to charmonium + pion/eta. We use them, in combination with our previous findings, to discuss the possible emergence of SU(3)$_{\rm f}$ pentaquark octets and tetraquark nonets in the hidden-charm sector as a tool to discriminate among different theoretical interpretations.

hep-ph

Analysis of one-neutron transfer reaction in $^{18}$O + $^{76}$Se collision at 275 MeV

Purpose: We want to analyze transitions to low-lying excited states of the residual and ejectile nuclei in the 76Se(18O, 17O) 77Se one-neutron stripping reaction at 275-MeV incident energy and determine the role of single-particle and core excitation in the description of the measured cross sections. In addition, we explore the sensitivity of the calculated cross section to different nuclear structure models. Methods: The excitation energy spectrum and the differential cross-section angular distributions are measured using the MAGNEX large acceptance magnetic spectrometer for the detection of the ejectiles and the missing mass technique for the reconstruction of the reaction kinematics. The data are compared with calculations based on distorted-wave Born approximation, coupled-channels Born approximation, and coupled reaction channels adopting spectroscopic amplitudes for the projectile and target overlaps derived by large-scale shell-model calculations and interacting boson-fermion model. Results: Peaks in the energy spectra corresponding to groups of unresolved transitions to 77Se and 17O are identified. The experimental cross sections are extracted and compared to theoretical calculations. A remarkable agreement is found, without using any scaling factors, demonstrating that the adopted models for nuclear structure and reaction take into account the relevant aspects of the studied processes. The main transitions which contribute to the cross section of each peak are identified.

nucl-ex

Analysis of two-nucleon transfer reactions in the 20Ne + 116Cd system at 306 MeV

Background: Heavy-ion induced two-nucleon transfer reactions are powerful tools to reveal peculiar aspects of the atomic nucleus, such as pairing correlations, single-particle and collective degrees of freedom, and more. Also, these processes are in competition with the direct meson exchange in the double charge exchange reactions, which have recently attracted great interest due to their possible connection to neutrinoless double-beta decay. In this framework, the exploration of two-nucleon transfer reactions in the 20Ne+116Cd collision at energies above the Coulomb barrier is particularly relevant since the 116Cd nucleus is a candidate for the double-beta decay. Methods: We measured the excitation energy spectra and absolute cross sections for the two reactions using the MAGNEX large acceptance magnetic spectrometer to detect the ejectiles. We performed direct coupled reaction channels and sequential distorted wave Born approximation calculations using the double folding São Paulo potential to model the initial and final state interactions. The spectroscopic amplitudes for two- and singleparticle transitions were derived by different nuclear structure approaches: microscopic large-scale shell model, interacting boson model-2 and quasiparticle random phase approximation. Results: The calculations are able to reproduce the experimental cross sections for both two-neutron and twoproton transfer reactions. The role of couplings with the inelastic channels are found to be important in the two-proton transfer case. A competition between the direct and the sequential process is found in the reaction mechanism. For the two-proton transfer case, the inclusion of the 1g7/2 and 2d5/2 orbitals in the model space is crucial.

nucl-ex

Light dark matter searches with positrons

We discuss two complementary strategies to search for light dark matter (LDM) exploiting the positron beam possibly available in the future at Jefferson Laboratory. LDM is a new compelling hypothesis that identifies dark matter with new sub-GeV "hidden sector" states, neutral under standard model interactions and interacting with our world through a new force. Accelerator-based searches at the intensity frontier are uniquely suited to explore it. Thanks to the high intensity and the high energy of the CEBAF (Continuous Electron Beam Accelerator Facility) beam, and relying on a novel LDM production mechanism via positron annihilation on target atomic electrons, the proposed strategies will allow us to explore new regions in the LDM parameters space, thoroughly probing the LDM hypothesis as well as more general hidden sector scenarios.

hep-ex

Quark structure of the $X(4500)$, $X(4700)$ and $χ_{\rm c}(4P,5P)$ states

We study some of the main properties (masses and open-flavor strong decay widths) of $4P$ and $5P$ charmonia. While there are two candidates for the $χ_{\rm c0}(4P,5P)$ states, the $X(4500)$ and $X(4700)$, the properties of the other members of the $χ_{\rm c}(4P,5P)$ multiplets are still completely unknown. With this in mind, we start to explore the charmonium interpretation for these mesons. Our second goal is to investigate if the apparent mismatch between the Quark Model (QM) predictions for $χ_{\rm c0}(4P,5P)$ states and the properties of the $X(4500)$ and $X(4700)$ mesons can be overcome by introducing threshold corrections in the QM formalism. According to our coupled-channel model results for the threshold mass shifts, the $χ_{\rm c0}(5P) \rightarrow X(4700)$ assignment is unacceptable, while the $χ_{\rm c0}(4P) \rightarrow X(4500)$ or $X(4700)$ assignments cannot be completely ruled out.

hep-ph

$β$-decay rates of $^{(115,117)}$Rh into $^{(115,117)}$Pd isotopes in the microscopic IBFM-2

The structure of odd-$A$ $^{(115,117)}$Rh and $^{(115,117)}$Pd isotopes is studied by means of the neutron-proton Interacting Boson-Fermion Model (IBFM-2). $J^P = \frac{1}{2}^+$ quantum number assignment for the $^{(115,117)}$Pd ground-states is critically discussed and the predicted energy levels are compared to the existing experimental data. The resulting nuclear wave functions are used to compute the $β$-decay $ft$ values of the transitions from $^{(115,117)}$Rh to $^{(115,117)}$Pd in the microscopic IBFM-2 and the results compared with the data.

nucl-th

Spectrum of fully-heavy tetraquarks from a diquark+antidiquark perspective

Using a relativized diquark model Hamiltonian, we calculate the masses of $J^{PC}=0^{++}$ ground-state tetraquarks in the following systems: $b s \bar b \bar s$, $bb \bar n \bar n$ ($n=u, d$), $bb \bar s \bar s$, $cc\bar c \bar c$, $b b \bar b \bar b$, $b c\bar b \bar c$ and $b b \bar c \bar c$. We also compute extensive spectra for the fully-heavy quark flavour combinations. Finally, as a test of the diquark model approach, we compute the masses of fully-heavy baryons in the diquark model. Our results may be compared soon to the forthcoming experimental data for fully-heavy three-quark systems.

hep-ph

A study of $c c\bar{c}\bar{c}$ tetraquark decays in 4 muons and in $D^{(*)} \bar{D}^{(*)}$ at LHC

We perform a quantitative analysis of the decays of $cc\bar c\bar c$ tetraquarks with $J^{PC}=0^{++}, 2^{++}$ into 4 muons and into hidden- and open-charm mesons and estimate, for the first time, the fully charmed tetraquark decay width. The calculated cross section upper limit is $\sim 40$ fb for the 4 muons channel, and $\sim 28$ nb for the $D^{(*)} \bar D^{(*)} \to eμ$ channel. On the basis of our results, with the present sensitivity LHCb should detect both signals, for $0^{++}$ and $2^{++}$ fully-charmed tetraquarks.

hep-ph

Diquark Correlations in Hadron Physics: Origin, Impact and Evidence

The last decade has seen a marked shift in how the internal structure of hadrons is understood. Modern experimental facilities, new theoretical techniques for the continuum bound-state problem and progress with lattice-regularised QCD have provided strong indications that soft quark+quark (diquark) correlations play a crucial role in hadron physics. For example, theory indicates that the appearance of such correlations is a necessary consequence of dynamical chiral symmetry breaking, viz. a corollary of emergent hadronic mass that is responsible for almost all visible mass in the universe; experiment has uncovered signals for such correlations in the flavour-separation of the proton's electromagnetic form factors; and phenomenology suggests that diquark correlations might be critical to the formation of exotic tetra- and penta-quark hadrons. A broad spectrum of such information is evaluated herein, with a view to consolidating the facts and therefrom moving toward a coherent, unified picture of hadron structure and the role that diquark correlations might play.

hep-ph