Related papers: Four-quark stability
Indirect searches, and in particular rare decays, have proven to be a fruitful field to search for New Physics beyond the Standard Model. While the down-quark sector (B and K) have been studied in detail, less attention was devoted to charm…
I provide a comprehensive review of indirect searches for New Physics with charmed mesons. I discuss current theoretical and experimental challenges and successes in understanding decays and mixings of those mesons. I argue that in many New…
The theory of the strong force, quantum chromodynamics, describes the proton in terms of quarks and gluons. The proton is a state of two up quarks and one down quark bound by gluons, but quantum theory predicts that in addition there is an…
After sketching heavy quark expansions as applied to heavy flavour decays I emphasize the relevance of nonperturbative dynamics at the charm scale for exclusive $b\to c$ modes. I address the issue of quark-hadron duality for charm and…
Recent developments in charm physics within the standard model and beyond are reviewed. The precision study of leptonic charm meson decays accompanied with the constraints coming from K, B and tau physics enables to determine constraints on…
Doubly charmed mesons are studied within a quark model framework. We solve the four-quark Schor\"dinger equation by means of a variational approach by using different interacting potentials. Our results point to the existence of a stable…
Despite the apparent simplicity of meson spectroscopy there are some states which cannot be accommodated in the usual $q\bar q$ structure. Among them there are either exotic states as the X(1600) or the recently measured charm states…
We investigate the charm sector of the nucleon structure phenomenologically, using the most up-to-date global QCD analysis. Going beyond the common assumption of purely radiatively generated charm, we explore possible degrees of freedom in…
The possibility of using the charm system to search for new physics is addressed. Phenomena such as $D^0-\bar D^0$ mixing and rare decays of charmed mesons are first examined in the Standard Model to test our present understanding and to…
A number of new four-quark states containing from one to four charm or anti-charm quarks have been observed recently. Many of these new states have been discovered at the LHC. The production of these states via intrinsic charm in the proton…
The masses of the ground state and excited heavy tetraquarks with hidden charm and bottom are calculated within the relativistic diquark-antidiquark picture. The dynamics of the light quark in a heavy-light diquark is treated completely…
The molecular picture and the constituent-quark model of exotic hadrons are reviewed, with application to the states recently discovered in the hidden-charm and hidden beauty sectors, and to other configurations.
We set the scene for theoretical issues in charm physics that were discussed at CHARM 2016 in Bologna. In particular we emphasize the importance of improving our understanding of standard model contributions to numerous charm observables…
We review some recent studies on the string model of confinement inspired by the strong-coupling regime of QCD and its application to exotic multiquark configurations. This includes two quarks and two antiquarks, four quarks and one…
The relativistic four-quark equations are found in the framework of coupled-channel formalism. The dynamical mixing of the meson-meson states with the four-quark states is considered. The four-quark amplitudes of the tetraquarks with hidden…
New results on properties and decays of open charm and charmonium states are reviewed. The emphasis is on examples that illustrate the various aspects through which studies of charm physics impact the field.
More and more hadron states are found to be difficult to be accommodated by the quenched quark models which describe baryons as 3-quark states and mesons as antiquark-quark states. Dragging out an antiquark-quark pair from the gluon field…
Scores of exotic hadrons, particularly tetraquarks and pentaquarks in the heavy-quark sector, have been observed in the past 20 years, and more continue to be discovered to this day. Unlike mesons and baryons, such exotics are not mandated…
In some models, exotic baryons with strangeness and anticharm or antibeauty should exist and even be stable against strong decay. We consider the stability of such possible exotic baryons, which in the constituent quark picture are called…
In this feature article we summarise and highlight aspects of the treatment of four-quark states with functional methods. Model approaches to those exotic mesons almost inevitably have to assume certain internal structures, e.g. by grouping…