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E. Santopinto

Publications and source records attributed to E. Santopinto.

At least 37 records · Page 2Linked to original sources
arXiv2020

Quark structure of the $χ_{\rm c}(3P)$ and $X(4274)$ resonances and their strong and radiative decays

We calculate the masses of $χ_{\rm c}(3P)$ states with threshold corrections in a coupled-channel model. The model was recently applied to the description of the properties of $χ_{\rm c}(2P)$ and $χ_{\rm b}(3P)$ multiplets [Phys.\ Lett.\ B {\bf 789}, 550 (2019)]. We also compute the open-charm strong decay widths of the $χ_{\rm c}(3P)$ states and their radiative transitions. According to our predictions, the $χ_{\rm c}(3P)$ states should be dominated by the charmonium core, but they may also show small meson-meson components. The $X(4274)$ is interpreted as a $c \bar c$ $χ_{\rm c1}(3P)$ state. More informations on the other members of the $χ_{\rm c}(3P)$ multiplet, as well as a more rigorous analysis of the $X(4274)$'s decay modes, are needed to provide further indications on the quark structure of the previous resonance.

hep-ph↗
arXiv2020

Hidden-charm and bottom tetra- and pentaquarks with strangeness in the hadro-quarkonium and compact tetraquark models

In two recent papers, we used the hadro-quarkonium model to study the properties of hidden-charm and bottom tetraquarks and pentaquarks. Here, we extend the previous results and calculate the masses of heavy-quarkonium-kaon/hyperon systems. We also compute the spectrum of hidden-charm and bottom tetraquarks with strangeness in the compact tetraquark (diquark-antidiquark) model. If heavy-light exotic systems with non-null strangeness content were to be observed experimentally, it might be possible to distinguish among the large variety of available theoretical pictures for tetra- and pentaquark states and, possibly, rule out those which are not compatible with the data.

hep-ph↗
arXiv2020

Heavy $Ω_c$ and $Ω_b$ baryons in the quark model

In this contribution, we present a study of ground- and excited-state $Ω_c$ and $Ω_b$ baryons consisting of two strange quarks and a heavy charm or bottom quark. An analysis in the quark model shows that the recently observed excited $Ω_c$ and $Ω_b$ states can be interpreted in terms of $λ$-mode excitations.

nucl-th↗
arXiv2020

Search for $bb\bar{b}\bar{b}$ tetraquark decays in 4 muons, $B^{+} B^{-}$, $B^0 \bar{B}^0$ and $B_s^0 \bar{B}_s^0$ channels at LHC

We perform a quantitative analysis of the $bb\bar{b}\bar{b}$ tetraquark decays into hidden- and open-bottom mesons and calculate, for the first time, the $bb\bar{b}\bar{b}$ tetraquark total decay width. On the basis of our results, we propose the $bb\bar{b}\bar{b} \to B^{+} B^{-} (B^0 \bar{B}^0) (B_s^0 \bar{B}_s^0) \to l^{+} l^{-}+\text{X}$ decays as the most suitable channels to observe the $bb\bar{b}\bar{b}$ tetraquark states, since the calculated two-lepton cross section upper limit, $\simeq 39 $ fb, is so large as to be potentially detectable with the 2018 LHCb sensitivity, paving the way to the observation of the $bb\bar{b}\bar{b}$ tetraquark in the future LHCb upgrade. The $4μ$ signal for the ground state, $J^{PC}=0^{++}$, is likely to be too small even for the upgraded LHCb, but it may not be hopeless for the $J^{PC}=2^{++}$ fully-bottom state.

hep-ph↗
arXiv2020

NURE: An ERC project to study nuclear reactions for neutrinoless double beta decay

Neutrinoless double beta decay (0ν\b{eta}\b{eta}) is considered the best potential resource to determine the absolute neutrino mass scale. Moreover, if observed, it will signal that the total lepton number is not conserved and neutrinos are their own anti-particles. Presently, this physics case is one of the most important research beyond Standard Model and might guide the way towards a Grand Unified Theory of fundamental interactions. Since the \b{eta}\b{eta} decay process involves nuclei, its analysis necessarily implies nuclear structure issues. The 0ν\b{eta}\b{eta} decay rate can be expressed as a product of independent factors: the phase-space factors, the nuclear matrix elements (NME) and a function of the masses of the neutrino species. Thus the knowledge of the NME can give information on the neutrino mass scale, if the 0ν\b{eta}\b{eta} decay rate is measured. In the NURE project, supported by a Starting Grant of the European Research Council, nuclear reactions of double charge-exchange (DCE) will be used as a tool to extract information on the \b{eta}\b{eta} NME. In DCE reactions and \b{eta}\b{eta} decay, the initial and final nuclear states are the same and the transition operators have similar structure. Thus the measurement of the DCE absolute crosssections can give crucial information on \b{eta}\b{eta} matrix elements.

nucl-ex↗
arXiv2020

Measuring nuclear reaction cross sections to extract information on neutrinoless double beta decay

Neutrinoless double beta decay (0v\b{eta}\b{eta}) is considered the best potential resource to access the absolute neutrino mass scale. Moreover, if observed, it will signal that neutrinos are their own anti-particles (Majorana particles). Presently, this physics case is one of the most important research "beyond Standard Model" and might guide the way towards a Grand Unified Theory of fundamental interactions. Since the 0v\b{eta}\b{eta} decay process involves nuclei, its analysis necessarily implies nuclear structure issues. In the NURE project, supported by a Starting Grant of the European Research Council (ERC), nuclear reactions of double charge-exchange (DCE) are used as a tool to extract information on the 0v\b{eta}\b{eta} Nuclear Matrix Elements. In DCE reactions and \b{eta}\b{eta} decay indeed the initial and final nuclear states are the same and the transition operators have similar structure. Thus the measurement of the DCE absolute cross-sections can give crucial information on \b{eta}\b{eta} matrix elements. In a wider view, the NUMEN international collaboration plans a major upgrade of the INFN-LNS facilities in the next years in order to increase the experimental production of nuclei of at least two orders of magnitude, thus making feasible a systematic study of all the cases of interest as candidates for 0v\b{eta}\b{eta}.

nucl-ex↗
arXiv2019

Masses of Light and Heavy Mesons and Baryons: A Unified Picture

We compute masses of positive parity spin-$1/2$ and $3/2$ baryons composed of $u$, $d$, $s$, $c$ and $b$ quarks in a quark-diaquark picture. The mathematical foundation for this analysis is implemented through a symmetry-preserving Schwinger-Dyson equations treatment of a vector-vector contact interaction, which preserves key features of quantum chromodynamics, such as confinement, chiral symmetry breaking and low energy Goldberger-Treiman relations. This study requires a computation of diquark correlations containing these quarks which in turn are readily inferred from solving the Bethe-Salpeter equations of the corresponding mesons. Therefore, it serves as a unified formalism for a multitude of mesons and baryons. It builds on our previous works on the study of masses, decay constants and form factors of quarkonia and light mesons, employing the same model. We use two sets of parameters, one which remains exactly the same for both the light and heavy sector hadrons, and another where the coupling strength is allowed to evolve according to the available mass scales of quarks. Our results are in very good agreement with the existing experimental data as well as predictions of other theoretical approaches whenever comparison is possible.

nucl-th↗
arXiv2019

Dark matter search in a Beam-Dump eXperiment (BDX) at Jefferson Lab -- 2018 update to PR12-16-001

This document complements and completes what was submitted last year to PAC45 as an update to the proposal PR12-16-001 "Dark matter search in a Beam-Dump eXperiment (BDX)" at Jefferson Lab submitted to JLab-PAC44 in 2016. Following the suggestions contained in the PAC45 report, in coordination with the lab, we ran a test to assess the beam-related backgrounds and validate the simulation framework used to design the BDX experiment. Using a common Monte Carlo framework for the test and the proposed experiment, we optimized the selection cuts to maximize the reach considering simultaneously the signal, cosmic-ray background (assessed in Catania test with BDX-Proto) and beam-related backgrounds (irreducible NC and CC neutrino interactions as determined by simulation). Our results confirmed what was presented in the original proposal: with 285 days of a parasitic run at 65 $μ$A (corresponding to $10^{22}$ EOT) the BDX experiment will lower the exclusion limits in the case of no signal by one to two orders of magnitude in the parameter space of dark-matter coupling versus mass.

physics.ins-det↗
arXiv2019

The $Ω_{c}$-puzzle solved by means of spectrum and strong decay amplitude predictions

The observation of new $Ω_{c}=ssc$ states by LHCb \cite{Aaij:2017nav} and the confirmation of four of them by Belle \cite{Yelton:2017qxg} may represent an important milestone in our understanding of the quark organization inside hadrons. By providing results for the spectrum of $Ω_{c(b)}$ baryons and predictions for their $Ξ_{c(b)}^{+}K^{-}$ decay channels, we suggest a possible solution to the $Ω_{c}$ quantum number puzzle. We also discuss why the set of $Ω_{c(b)}$ baryons are the most suitable environment to test the validity of three-quark and quark-diquark effective degrees of freedom. Finally, we calculate the masses and the partial decay widths of the $Ξ_b(6227)$ and $Σ_b(6097)$ states, just observed by LHCb \cite{Aaij:2018yqz,Aaij:2018tnn}. Our results are in good agreement with LHCb experimental data.

hep-ph↗
arXiv2019

Heavy-light mesons spectra in a contact interaction

We present the spectrum and decay constants of heavy-light mesons in four different channels: pseudo-scalar, vector, scalar and axial vector. We extend the framework for our previous analysis in a unified symmetry-preserving Schwinger-Dyson equations treatment of a vector$\times$vectord contact interaction. Despite the simplicity of our model, the results found for the meson masses are in good agreement experimental data and earlier model calculations based upon Schwinger-Dyson and Bethe-Salpeter equations (BSEs) involving sophisticated interaction kernels.

hep-ph↗
arXiv2019

Threshold corrections of $χ_{\rm c}(2P)$ and $χ_{\rm b}(3P)$ states and $J/ψρ$ and $J/ψω$ transitions of the $X(3872)$ in a coupled-channel model

We calculate the masses of $χ_{\rm c}(2P)$ and $χ_{\rm b}(3P)$ states with threshold corrections in a coupled-channel model. Here, the meson quarkonium core is augmented by higher Fock components due to pair-creation effects. According to our results, we interpret the resonances characterized by very small threshold corrections, like $χ_{\rm b}(3P)$'s, as almost pure quarkonia, and those states characterized by non-negligible threshold corrections, like the $X(3872)$, as quarkonium cores plus meson-meson components. We also study the $J/ψρ$ and $J/ψω$ hidden-flavor strong decays of the $X(3872)$. The decays are calculated as the dissociation of one of these components ($D^0 \bar D^{0*}$) into a $c \bar c$ state ($J/ψ$) plus a light meson ($ρ$ or $ω$) in a potential model. In particular, our result for the ratio between the $X(3872) \rightarrow J/ψω$ and $J/ψρ$ widths (0.6) is compatible with the present experimental data ($0.8\pm0.3$) within the experimental error.

hep-ph↗
arXiv2018

The baryo-quarkonium picture for hidden-charm and bottom pentaquarks and LHCb $P_{\rm c}(4380)$ and $P_{\rm c}(4450)$ states

We study baryo-charmonium [$η_{\rm c}$- and $J/ψ$-$N^*$, $η_{\rm c}(2S)$-, $ψ(2S)$- and $χ_{\rm c}(1P)$-$N$] and baryo-bottomonium [$η_{\rm b}(2S)$-, $Υ(2S)$- and $χ_{\rm b}(1P)$-$N$] bound states, where $N$ is the nucleon and $N^*$ a nucleon resonance. In the baryo-quarkonium model, the five $qqq Q \bar Q$ quarks are arranged in terms of a heavy quarkonium core, $Q \bar Q$, embedded in light baryonic matter, $qqq$, with $q = u$ or $d$. The interaction between the $Q \bar Q$ core and the light baryon can be written in terms of the QCD multipole expansion. The spectrum of baryo-charmonium states is calculated and the results compared with the existing experimental data. In particular, we can interpret the recently discovered $P_{\rm c}(4380)$ and $P_{\rm c}(4450)$ pentaquarks as $ψ(2S)$-$N$ and $χ_{\rm c2}(1P)$-$N$ bound states, respectively. We observe that in the baryo-bottomonium sector the binding energies are, on average, slightly larger than those of baryo-charmonia. Because of this, the hidden-bottom pentaquarks are more likely to form than their hidden-charm counterparts. We thus suggest the experimentalists to look for five-quark states in the hidden-bottom sector in the $10.4-10.9$ GeV energy region.

hep-ph↗
arXiv2018

The NUMEN project: NUclear Matrix Elements for Neutrinoless double beta decay

The article describes the main achievements of the NUMEN project together with an updated and detailed overview of the related R&D activities and theoretical developments. NUMEN proposes an innovative technique to access the nuclear matrix elements entering the expression of the lifetime of the double beta decay by cross section measurements of heavy-ion induced Double Charge Exchange (DCE) reactions. Despite the two processes, namely neutrinoless double beta decay and DCE reactions, are triggered by the weak and strong interaction respectively, important analogies are suggested. The basic point is the coincidence of the initial and final state many-body wave-functions in the two types of processes and the formal similarity of the transition operators. First experimental results obtained at the INFN-LNS laboratory for the 40Ca(18O,18Ne)40Ar reaction at 270 MeV, give encouraging indication on the capability of the proposed technique to access relevant quantitative information. The two major aspects for this project are the K800 Superconducting Cyclotron and MAGNEX spectrometer. The former is used for the acceleration of the required high resolution and low emittance heavy ion beams and the latter is the large acceptance magnetic spectrometer for the detection of the ejectiles. The use of the high-order trajectory reconstruction technique, implemented in MAGNEX, allows to reach the experimental resolution and sensitivity required for the accurate measurement of the DCE cross sections at forward angles. However, the tiny values of such cross sections and the resolution requirements demand beam intensities much larger than manageable with the present facility. The on-going upgrade of the INFN-LNS facilities in this perspective is part of the NUMEN project and will be discussed in the article.

nucl-ex↗
arXiv2018

Photoproduction of $K^+K^-$ meson pairs on the proton

The exclusive reaction $γp \to p K^+ K^-$ was studied in the photon energy range $3.0 - 3.8 \mbox{ GeV}$ and momentum transfer range $0.6<-t<1.3 \mbox{ GeV}^2$. Data were collected with the CLAS detector at the Thomas Jefferson National Accelerator Facility. In this kinematic range the integrated luminosity was approximately 20 pb$^{-1}$. The reaction was isolated by detecting the $K^+$ and the proton in CLAS, and reconstructing the $K^-$ via the missing-mass technique. Moments of the di-kaon decay angular distributions were extracted from the experimental data. Besides the dominant contribution of the $ϕ$ meson in the $P$-wave, evidence for $S-P$ interference was found. The differential production cross sections $dσ/dt$ for individual waves in the mass range of the $ϕ$ resonance were extracted and compared to predictions of a Regge-inspired model. This is the first time the $t$-dependent cross section of the $S$-wave contribution to the elastic $K^+K^-$ photoproduction has been measured.

hep-ex↗
arXiv2018

Heavy-ion double-charge-exchange and its relation to neutrinoless double-beta decay

We introduce the formalism to describe heavy-ion Double-Charge-Exchange (DCE) processes in the eikonal approximation. We focus on the low-momentum-transfer limit -- corresponding to the differential cross section at $θ=0^\circ$ -- and, for the first time, we show that it is possible to factorize the DCE cross-section in terms of reaction and nuclear parts. Whereas in the $θ\neq0^\circ$ case the nuclear part is a convolution of the beam and target nuclear matrix elements (NMEs), for $θ=0^\circ$ we demonstrate - for the first time- that the transition matrix elements can be written as the sum of Double-Gamow-Teller (DGT) and Double Fermi (DF) type parts, and that they can both be further factorized in terms of target and projectile NMEs. By making use of the Interacting Boson Model (IBM) formalism, we also show that the DGT and total parts of the neutrinoless double-beta decay NMEs are in linear correlation with DCE-DGT NMEs. This confirms the hypothesis of a linear correlation between them, as introduced in [Phys.\ Rev.\ Lett.\ {\bf 120}, 142502 (2018)]. The possibility of a Two-Step Factorization (TSF) of the very forward differential DCE-cross-section and the emergence of DGT and DF types for the DCE nuclear matrix elements, combined with a linear correlation between DCE-DGT and 0$νββ$ NMEs, opens the possibility of placing an upper limit on neutrinoless double-beta decay NMEs in terms of the DCE experimental data at $θ=0^\circ$.

nucl-th↗
arXiv2018

Open-flavor strong decays of open-charm and open-bottom mesons in the $^3P_0$ model

We provide results for the open-flavor strong decays of open-charm ($D$ and $D_{\rm s}$) and open-bottom ($B$, $B_{\rm s}$ and $B_{\rm c}$) mesons. The decays are calculated in a modified version of the $^3P_0$ pair-creation model, assuming harmonic oscillator wave functions. The spectra of open-charm and open-bottom mesons used in the calculations are computed within Godfrey and Isgur's relativized quark model. Quantum number assignments are also provided. Our results are compared with the existing experimental data.

hep-ph↗
arXiv2018

Dark matter search in a Beam-Dump eXperiment (BDX) at Jefferson Lab: an update on PR12-16-001

This document is an update to the proposal PR12-16-001 Dark matter search in a Beam-Dump eXperiment (BDX) at Jefferson Lab submitted to JLab-PAC44 in 2016 reporting progress in addressing questions raised regarding the beam-on backgrounds. The concerns are addressed by adopting a new simulation tool, FLUKA, and planning measurements of muon fluxes from the dump with its existing shielding around the dump. First, we have implemented the detailed BDX experimental geometry into a FLUKA simulation, in consultation with experts from the JLab Radiation Control Group. The FLUKA simulation has been compared directly to our GEANT4 simulations and shown to agree in regions of validity. The FLUKA interaction package, with a tuned set of biasing weights, is naturally able to generate reliable particle distributions with very small probabilities and therefore predict rates at the detector location beyond the planned shielding around the beam dump. Second, we have developed a plan to conduct measurements of the muon ux from the Hall-A dump in its current configuration to validate our simulations.

physics.ins-det↗