Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Phd by thesis

The hidden-charm pentaquark and tetraquark states

A large number of experimental discoveries especially in the heavy quarkonium sector that did not at all fit to the expectations of the until then very successful quark model led to a renaissance of hadron spectroscopy Among various explanations of the internal structure of these excitations, hadronic molecules, being analogues of light nuclei, play a unique role since for those predictions can be made with controlled uncertainty We review experimental evidences of various candidates of hadronic molecules, and methods of identifying such structures Nonrelativistic effective field theories are the suitable framework for studying hadronic molecules, and are discussed in both the continuum and finite volumes Also pertinent lattice QCD results are presented Further, we discuss the production mechanisms and decays of hadronic molecules, and comment on the reliability of certain assertions often made in the literature

Hadronic molecules

Quantum chromodynamics (QCD), the generally accepted theory for strong interactions, describes the interactions between quarks and gluons. The strongly interacting particles that are seen in nature are hadrons, which are composites of quarks and gluons. Since QCD is a strongly coupled theory at distance scales that are characteristic of observable hadrons, there are no rigorous, first-principle methods to derive the spectrum and properties of the hadrons from the QCD Lagrangian, except for lattice QCD simulations that are not yet able to cope with all aspects of complex and short-lived states. Instead, a variety of “QCD inspired” phenomenological models have been proposed. Common features of these models are predictions for the existence of hadrons with substructures that are more complex than the standard quark-antiquark mesons and the three-quark baryons of the original quark model that provides a concise description of most of the low-mass hadrons. Recently, an assortment of candidates for nonstandard multiquark mesons, meson-gluon hybrids, and pentaquark baryons that contain heavy (charm or bottom) quarks has been discovered. Here the experimental evidence for these states is reviewed and some general comparisons of their measured properties with standard quark model expectations and predictions of various models for nonstandard hadrons are made. The conclusion is that the spectroscopy of all but the simplest hadrons is not yet understood.

https://link.aps.org/accepted/10.1103/RevModPhys.90.015003

Nonstandard heavy mesons and baryons: Experimental evidence

The interacting boson model.

We discuss the possible existence of the fully-heavy tetraquarks. We calculate the ground-state energy of the $$bb {\bar{b}} {\bar{b}}$$
 bound state, where b stands for the bottom quark, in a nonrelativistic effective field theory framework with one-gluon-exchange (OGE) color Coulomb interaction, and in a relativized diquark model characterized by OGE plus a confining potential. Our analysis advocates the existence of uni-flavor heavy four-quark bound states. The ground state $$bb{\bar{b}}{\bar{b}}$$
 tetraquark mass is predicted to be $$(18.72\pm 0.02)$$
  GeV. Mass inequality relations among the lowest $$QQ\bar{Q}\bar{Q}$$
 states, where $$Q\in \{c, b\}$$
 , and the corresponding heavy quarkonia are presented, which give the upper limit on the mass of ground state $$QQ\bar{Q}\bar{Q}$$
 . The possible decays of the lowest $$bb\bar{b}\bar{b}$$
 are highlighted, which might provide useful references in the search for them in ongoing LHC experiments, and its width is estimated to be a few tens of MeV.

/pdf/spectroscopy-and-decays-of-the-fully-heavy-tetraquarks-1ok6rrfwwq.pdf

Spectroscopy and decays of the fully-heavy tetraquarks

We present a quark model calculation of the charmonium spectrum with self-energy corrections due to the coupling to the meson-meson continuum. The bare masses used in the calculation are computed within the relativized quark model by Godfrey and Isgur. The strong decay widths of $3S$, $2P$, $1D$, and $2D$ $c\overline{c}$ states are also calculated, to set the values of the ${}^{3}{P}_{0}$ pair-creation model's parameters we use to compute the vertex functions of the loop integrals. Finally, the nature of the $X(3872)$ resonance is analyzed and the main possibilities ($c\overline{c}$ state or $D{\overline{D}}^{*}$ molecule) are discussed. According to our results, the $X(3872)$ is compatible with the meson ${\ensuremath{\chi}}_{c1}(2P)$, with ${J}^{\mathrm{PC}}={1}^{++}$, and is thus interpreted as a $c\overline{c}$ core plus higher Fock components due to the coupling to the meson-meson continuum. These ${J}^{\mathrm{PC}}={1}^{++}$ quantum numbers are in agreement with the experimental results found by the LHCb collaboration. In our view, the $X(3872)$'s mass is lower than the quark model's predictions because of self-energy shifts.

Interpretation of the X(3872) as a charmonium state plus an extra component due to the coupling to the meson-meson continuum

We discuss the nature of the ${\ensuremath{\chi}}_{b}(3P)$ and $X(3872)$ mesons. Are the ${\ensuremath{\chi}}_{b}(3P)$'s standard $b\overline{b}$ mesons or $b\overline{b}$ states with a significative continuum component? Is the $X(3872)$ a $c\overline{c}$ state with continuum coupling effects or a meson-meson molecule? To do that, we compare quark model and unquenched quark model results for the mass barycenter and splittings of the ${\ensuremath{\chi}}_{b}(3P)$ multiplet. Future and more precise experimental results will discriminate between the two interpretations. In the case of the $X(3872)$, we interpret it as a $c\overline{c}$ core plus higher Fock components due to the coupling to the meson-meson continuum, and thus we think that it is compatible with the meson ${\ensuremath{\chi}}_{c1}(2P)$, with ${J}^{PC}={1}^{++}$. The ${J}^{PC}={1}^{++}$ quantum numbers are in agreement with the experimental results found by the LHCb collaboration. In our view, the $X(3872)$'s mass is lower than the quark model's predictions because of self-energy shifts. We also provide an estimation of the open charm/bottom strong decay modes of the $X(3872)$ and ${\ensuremath{\chi}}_{b}(3P)$ mesons, such as $X(3872)\ensuremath{\rightarrow}D{\overline{D}}^{*}$ and ${\ensuremath{\chi}}_{b2}(3P)\ensuremath{\rightarrow}B\overline{B}$, and radiative transitions.

Quark structure of the $X(3872)$ and $\chi_b(3P)$ resonances

We show the results of a coupled-channel quark model calculation of the bottomonium spectrum with self-energy corrections due to the coupling to the meson-meson continuum. We also provide results for the open-bottom strong decay amplitudes of higher bottomonia in a ${^{3}P}_{0}$ model.

Higher mass bottomonia

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.

/pdf/spectrum-of-fully-heavy-tetraquarks-from-a-diquark-3xk75k9rxl.pdf

Jacopo Ferretti

Papers

Spectroscopy and decays of the fully-heavy tetraquarks

Interpretation of the X(3872) as a charmonium state plus an extra component due to the coupling to the meson-meson continuum

Quark structure of the $X(3872)$ and $\chi_b(3P)$ resonances

Higher mass bottomonia

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