### Regular Series

#### Mesons Beyond the Quark–Antiquark Picture

abstract

The vast majority of mesons can be understood as quark–antiquark states. Yet, various other possibilities exists: glueballs (bound-state of gluons), hybrids (quark–antiquark plus gluon), and four-quark states (either as diquark–antidiquark or molecular objects) are expected. In particular, the existence of glueballs represents one of the first predictions of QCD, which relies on the non-Abelian feature of its structure; this is why the search for glueballs and their firm discovery would be so important, both for theoretical and experimental developments. At the same time, many new resonances ($X,Y,$ and $Z$ states) were discovered experimentally, some of which can be well understood as four-quark objects. In this paper, we review some basic aspects of QCD and show in a pedagogical way how to construct an effective hadronic model of QCD. We then present the results for the decays of the scalar and the pseudoscalar glueballs within this approach and discuss the future applications to other glueball states. In conclusion, we briefly discuss the status of four-quark states, both in the low-energy domain (light scalar mesons) as well as in the high-energy domain (in the charmonia region)

#### Central Exclusive Particle Production in DPE Process: Search for Glueballs etc.

abstract

We shall discuss resonance production in the process of Central Exclusive Production (CEP) at hadron colliders. The corresponding program of glueball search in Double Pomeron Exchange (DPE) process shall also be discussed. As an exercise, we shall “construct” an experiment to measure CEP using the STAR experiment at the Relativistic Heavy Ion Collider (RHIC), where this program is currently under way. Preliminary $\pi ^+\pi ^-$ mass spectra ($dN/dM_X$) from the Central Exclusive Production (CEP) measured in the STAR detector shall be presented. For this measurement, one proton on each side of STAR was detected in the Roman Pots and the charged particle recoil system was measured in the Time Projection Chamber (TPC) of STAR.

#### Soliton Model for Baryons

abstract

We present a description of low-lying baryon states (below 2 GeV) based on the general soliton model, which follows from QCD in the limit of large number of colors. Relation to the quark model is discussed. The model describes the spectrum of baryons below 2 GeV with no extra nor missing states. Main properties of baryons (mass splitting and widths) are calculated and relations independent of the specific soliton model are derived. These relations agree rather well with the data.

#### Search for Exotic Hadronic Matter: Tetraquarks, Pentaquarks, Dibaryons and Mesic Nuclei

abstract

We describe selected results of the search for the exotic hadronic matter such as e.g. tetraquarks, pentaquarks and hexaquarks. The content of the proceedings is by far not complete and reflects a personal choice of the author with the emphasis put on the recent discovery of the dibaryon state and the search for the mesic nuclei with the WASA detector at COSY.

#### Recent Progress in Charmonium Studies

abstract

We review recent developments in studies of charmonium and charmonium-like states at $e^+e^-$ and hadronic colliders.

#### Doubly Heavy Exotic Mesons and Baryons and How to Look for Them

abstract

I discuss the experimental evidence for and theoretical interpretation of the new mesons and baryons with two heavy quarks. These include doubly-heavy baryons, exotic hadronic quarkonia and, most recently, a manifestly exotic pentaquark-like doubly heavy baryon discovered by LHCb with a minimal quark content $uud\bar c c$. Its mass, decay mode and width are in agreement with a prediction based on a physical picture of a deuteron-like ${\mit \Sigma }_c \bar D^*$ “hadronic molecule”. In the second part of the paper, I focus on possible ways of experimental exploration of this new spectroscopy of QCD, especially in future high-energy $e^+ e^-$ colliders with very high luminosity. The primary task of these machines is searching for physics beyond the Standard Model. Consequently, their planned CM energy is far above the relevant energy scale for production of the new doubly-heavy hadrons. Yet, preliminary analysis of radiative-return processes indicates rather high effective luminosity at CM energies of interest, suggesting a possibility for copious production.

#### Electroweak Symmetry Breaking and the Higgs Boson

abstract

The first LHC run has confirmed the Standard Model as the correct theory at the electroweak scale, and the existence of a Higgs-like particle associated with the spontaneous breaking of the electroweak gauge symmetry. This article overviews the present knowledge on the Higgs boson and discuss alternative scenarios of electroweak symmetry breaking which are already being constrained by the experimental data.

#### The Inert Doublet Model and Its Extensions

abstract

The Inert Doublet Model and its extension with an additional complex singlet is considered. The CP violation aspects are analysed in the simplified case, with one SM-like Higgs doublet and a complex singlet.

#### SUSY with $R$-symmetry: Confronting EW Precision Observables and LHC Constraints

abstract

After motivation and short presentation of the minimal supersymmetric model with $R$-symmetry (MRSSM), we address the question of accommodating the measured Higgs boson mass in accordance with electroweak precision observables and LHC constraints.

#### Dark Matter: Evidence, Direct and Indirect Searches

abstract

Dark Matter (DM) is thought to comprise the majority of matter in the universe. In these proceedings, we will briefly describe the plethora of evidence for the existence of Dark Matter, discuss alternatives in the form of changing the laws of gravitation and present some experimental efforts to discover the particle nature of the Dark Matter.

#### Asymptotic Freedom of Gluons in the Fock Space

abstract

Asymptotic freedom of gluons is described in terms of a family of scale-dependent renormalized Hamiltonian operators acting in the Fock space. The Hamiltonians are obtained by applying the renormalization group procedure for effective particles to the quantum Yang–Mills theory.

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