A fundamental question of physics is what ultimately happens to matter as it is heated or compressed. In the realm of very high temperature and density the fundamental degrees of freedom of the strong interaction, quarks and gluons, come into play and a transition from matter consisting of confined baryons and mesons to a state with 'liberated' quarks and gluons is expected. The study of the possible phases of strongly-interacting matter is at the focus of many research activities worldwide. In this article we discuss physical aspects of the phase diagram, its relation to the evolution of the early universe as well as the inner core of neutron stars. We also summarize recent progress in the experimental study of hadronic or quark-gluon matter under extreme conditions with ultrarelativistic nucleus-nucleus collisions.
We calculate the particle ratios for a strongly interacting hadronic matter matter using non-linear Walecka model (NLWM) in relativistic mean-field approximation. A comparison with Hadron Resonance Gas Model is made.
Equation of state and electric (isospin) charge fluctuations are studied for matter composed of interacting pions. The pion matter is described by self interacting scalar fields via a $ϕ^4-ϕ^6$ type Lagrangian. The mean-field approximation is used, and interaction parameters are fixed by fitting lattice QCD results on the isospin density as a function of the isospin chemical potential at zero temperature. Two scenarios for fixing the model parameters -- with and without the first order phase transition -- are considered, both yielding a satisfactory description of the lattice data. Thermodynam…
We introduce a method based on the chiral susceptibility, which enables one to draw a phase diagram in the chemical-potential/temperature plane for strongly-interacting quarks whose interactions are described by any reasonable gap equation, even if the diagrammatic content of the quark-gluon vertex is unknown. We locate a critical endpoint (CEP) at (μ^E,T^E) ~ (1.0,0.9)T_c, where T_c is the critical temperature for chiral symmetry restoration at μ=0; and find that a domain of phase coexistence opens at the CEP whose area increases as a confinement length-scale grows.
We report on a new equilibration scenario in relativistic heavy ion collisions, the scenario of the Increasingly Strongly Interacting Parton Plasma, and the effects of this scenario on equilibration and open charm, photon and dilepton production. The parton plasma is shown to be a very special kind of many-body system, which contains new physics concerning the approach towards equilibrium. This is likely to be unique to the parton plasma.
We summarize the phase diagrams of SU, SO and Sp gauge theories as function of the number of flavors, colors, and matter representation as well as the ones of phenomenologically relevant chiral gauge theories such as the Bars-Yankielowicz and the generalized Georgi-Glashow models. We finally report on the intriguing possibility of the existence of gauge-duals for nonsupersymmetric gauge theories and the impact on their conformal window.
Available experimental data in respect to a possible formation of a strongly interacting mixed phase are outlined. A physical program is formulated for new facilities being opend in Dubna for acceleration of heavy ions with an energy up to 5 AGeV.
We study the evolution of the equation of state of a strongly interacting quark system as a function of the diquark interaction strength. We show that for the system to avoid collapsing into a pressureless Boson gas at sufficiently strong diquark coupling strength, the diquark-diquark repulsion has to be self-consistently taken into account. In particular, we find that the tendency at zero temperature of the strongly interacting diquark gas to condense into the system ground state is compensated by the repulsion between diquarks if the diquark-diquark coupling constant is higher than a critica…
Using the classical argument about tree level unitarity breakdown in combination with the precision electroweak data, it is shown, that if part of the Higgs sector is strongly interacting, this part is small and is out of range of the LHC.
We employ a conformal mapping to explore the thermodynamics of strongly interacting matter at finite values of the baryon chemical potential $μ$. This method allows us to identify the singularity corresponding to the critical point of a second-order phase transition at finite $μ$, given information only at $μ=0$. The scheme is potentially useful for computing thermodynamic properties of strongly interacting hot and dense matter in lattice gauge theory. The technique is illustrated by an application to a chiral effective model.
I discuss the phase structure of strongly interacting matter at high temperatures and densities, as predicted by statistical QCD, and consider in particular the nature of the transition of hot hadronic matter to a plasma of deconfined quarks and gluons.
This text is meant as an introduction to the theoretical physics of photon emission in hot and dense strongly interacting matter, the principal application being relativistic nuclear collisions. We shall cover some of the results and techniques appropriate for studies at SPS, RHIC, and LHC energies
The understanding of the behaviour of strongly interacting matter at finite temperature and density is of fundamental interest and has applications in cosmology, in the astrophysics of neutron stars and in the physics of relativistic heavy ion collisions. Given the possible existence of strong magnetic fields in the mentioned situations, their effect on the QCD phase diagram has recently become a topic of increasing interest. Here, we report on the study of this issue in the framework of the two flavor Nambu-Jona-Lasinio model with Polyakov loop (PNJL) and an extension of it, the so-called ent…
The correlation between baryon number and strangeness elucidates the nature of strongly interacting matter, such as that formed transiently in high-energy nuclear collisions. This diagnostic can be extracted theoretically from lattice QCD calculations and experimentally from event-by-event fluctuations. The analysis of present lattice results above the critical temperature severely limits the presence of q-qbar bound states, thus supporting a picture of independent (quasi)quarks.
We study the ground-state properties of a dilute gas of strongly-interacting fermions in the framework of the coupled-cluster expansion (CCE). We demonstrate that properties such as universality, opening of a gap in the excitation spectrum and applicability of s-wave approximations appear naturally in the CCE approach. In the zero-density limit, we show that the ground-state energy density depends on only one parameter which in turn may depend at most on the spatial dimensionality of the system.
We discuss recent results for the equation of state for cold and dense strongly interacting matter. We consider the extreme cases of very high densities, where weak-coupling approaches may in principle give reasonable results, and very low densities, where we use the framework of heavy-baryon chiral perturbation theory. We also speculate on the nature of the chiral transition and present possible astrophysical implications.
We show how to obtain a complete set of electromagnetic corrections to a given nonperturbative model of strong interactions based on integral equations. The gauge invariance of these corrections is a consequence of their completeness.
We consider laboratory experiments that can detect stable, neutral strongly interacting massive particles (SIMPs). We explore the SIMP annihilation cross section from its minimum value (restricted by cosmological bounds) to the barn range, and vary the mass values from a GeV to a TeV. We also consider the prospects and problems of detecting such particles at the Tevatron.
Following a recent work on equation of state for strongly interacting quark-gluon plasma [J. Phys. G: Nucl. Part. Phys. 32, 993 (2006)], we revisited the equation of state by incorporating the non-perturbative effects in the deconfined plasma phase. Our results on thermodynamic observables viz. pressure, energy density, speed of sound etc. nicely fit with the lattice equation of state for gluon, massless and as well massive flavored plasma. Motivated by this agreement with lattice results, we have employed our equation of state to estimate the quarkonium suppression in an expanding, dissipativ…
We sketch some of our recent studies on probing strongly interacting electroweak symmetry breaking mechanism at high energy colliders such as the CERN LHC and the future e(+)e(-) linear collider. The study includes both model-dependent and model-independent probes.
We evaluate the impact of electroweak corrections of infrared origin on longitudinal strongly interacting gauge bosons scattering, calculating all order resummed expressions at the double log level. As a working example, we consider the Standard model with a heavy Higgs. At energies typical of forthcoming experiments (LHC,ILC,CLIC), the corrections are in the 10-40 % range, the relative sign depending on the initial state considered and on whether or not additional gauge bosons emission is included.
Strongly interacting gauge mediation (SIGM) of supersymmetry breaking is very attractive, since it naturally predicts a light gravitino of mass $\lsim{\cal O}(10)$ eV, which causes no cosmological problem. We discuss various signatures of the SIGM in the early stage (a low integrated luminosity period) of the LHC experiments. We show, in particular, a possible way to discriminate it from the conventional gauge mediation by counting the number of high $P_{\rm T}$ leptons.
We consider laboratory experiments that can detect stable, neutral strongly interacting massive particles (SIMPs). We explore the SIMP annihilation cross section from its minimum value (restricted by cosmological bounds) to the barn range, and vary the mass values from a GeV to a TeV. We also consider the prospects and problems of detecting such particles at the Tevatron.
This was a plenary talk at the 19th Conference of Slovak Physicists reviewing the status, consequences, and prospects of the 125-GeV boson discovery. To illustrate a possible impact of the discovery on the strongly-interacting extensions of the Standard Model the preliminary results of the analysis of the top-BESS effective model with the 125-GeV scalar boson added were shown. The complete analysis has appeared recently in arxiv:1301.2124.
We confront our quasi-particle model for the equation of state of strongly interacting matter with recent first-principle QCD calculations. In particular, we test its applicability at finite baryon densities by comparing with Taylor expansion coefficients of the pressure for two quark flavours. We outline a chain of approximations starting from the Phi-functional approach to QCD which motivates the quasi-particle picture.
Renormalization group analyses show that the three running gauge coupling constants of the Standard Model do not become equal at any energy scale. These analyses have not included any effects of the Higgs boson's self-interaction. In this paper, I examine whether these effects can modify this conclusion.
In this review we discuss theories of the electroweak symmetry breaking sector in which the $W$ and $Z$ interactions become strong at an energy scale not larger than a few TeV.
We propose a new mechanism for producing a Higgs boson mass near 125 GeV within the MSSM. By coupling the MSSM Higgs boson to a set of strongly interacting fields, large corrections to the Higgs quartic coupling are induced. Although the Higgs doublets do not participate in the strong dynamics, they feel the effects of the strongly coupled sector via (semi-)perturbative interactions. These same strong dynamics are also capable of generating the $μ$-term. Additionally, this strong sector is in the conformal window, which drives the couplings to an infrared fixed point and naturally generates mo…
A nonlinear transformation approach is formulated for the correlated fermions' thermodynamics through a medium-scaling effective action. An auxiliary implicit variable-effective chemical potential is introduced to characterize the non-Gaussian fluctuations physics. By incorporating the nonlocal correlation effects, the achieved grand partition function is made of coupled highly nonlinear parametric equations. Analytically, the low temperature expansions for the strongly interacting unitary Fermi gas are performed for the adiabatic compressibility-sound speed and specific heat with the Sommerfe…
If electro-weak symmetry is broken by a new strongly interacting sector, new physics will probably manifest itself in gauge boson scattering at the LHC. The relevant dynamics is well described in terms of an effective lagrangian. We discuss the probable size of the coefficients of the relevant operators under a combination of model-independent constraints and reasonable assumptions based on two models of the strongly interacting sector. We compare these values with LHC sensitivity and argue that they will be too small to be seen. Therefore, the presence of vector and scalar resonances required…
We report the coupling of an external $γγ$ or $t\bar t$ state to a strongly interacting EWSBS satisfying unitarity. We exploit perturbation theory for those coupling of the external state, whereas the EWSBS is taken as strongly interacting. We use a modified version of the IAM unitarization procedure to model such a strongly interacting regime. The matrix elements $V_LV_L\to V_LV_L$, $V_LV_L\leftrightarrow hh$, $hh\to hh$, $V_LV_L\leftrightarrow\{γγ,t\bar t\}$, and $hh\leftrightarrow\{γγ,t\bar t\}$ are all computed to NLO in perturbation theory with the Nonlinear Effective Field Theory of the …
g g \to γ\bar{f}f scattering is discussed in the strongly interacting phase of the MSSM. The rate for the decay h \to γ\bar{f} f is computed in the MSSM and SM, and values of the Higgs-sfermion coupling needed for the former to dominate on the latter are identified. It is found that the MSSM signal dominates on the SM one for Higgs-sfermion couplings well below the one needed for developing stopponium bound states via Higgs mediation.
The method of coset-space dimensional reduction is employed in order to proceed from a gauged E_8 * E_8' unified theory defined in 10 dimensions to 4 dimensions. The resulting theory comprises the Standard Model along with a strongly-interacting fermion sector which breaks the electroweak symmetry dynamically at the right scale.
Several proposals for dynamical electroweak symmetry breaking and fermion mass generation involve strong gauge interactions with a characteristic scale of a few hundred GeV. The detection of the glueballs which should occur in such models would be a indication of the non-Abelian nature of the gauge theories operating at this scale. We discuss signatures for these particles.
We study the possible experimental signatures resulting from a strongly-interacting electroweak sector at $e^-e^-$ colliders, emphasizing the signal enhancement by high beam polarization. We also discuss the unique role for operating the collider in $e^-γ$ mode to produce a heavy isosinglet vector state $ω_T$.
We investigate a model where neutrinos are strongly coupled to a new, light scalar field. In this model neutrinos annihilate as soon as they become non-relativistic in the early universe, and a non-zero neutrino mass has a marginal effect on the matter power spectrum. However, the angular power spectrum of the cosmic microwave background (CMB) is changed significantly because the strongly interacting fluid of neutrinos and scalars does not experience any anisotropic stress. Such models are strongly disfavoured by current observations. Interestingly, this leads to the conclusion that the relati…
We investigate fermion self energy problem in the strongly coupled dense medium in holographic approach. By working out bottom up models as well as top down ones we showed that vanishing thermal mass and non-existence of temperature generated plasmino mode is the universal feature of the strongly interacting fermion system. We identified that the dual of the bulk Rashiba effect, which was recently found by the Herzog et.al, is the presence of the plasmino mode generated by the density.
We propose a method to determine the total magnetic susceptibility of strongly interacting matter by lattice QCD simulations, and present first numerical results for the theory with two light flavors, which suggest a weak magnetic activity in the confined phase and the emergence of strong paramagnetism in the deconfined, Quark-Gluon Plasma phase.
We show that models of strongly interacting (SIMP) dark matter built to reproduce the DAMA signal actually cannot account for its time dependence. We discuss the constraints on this type of models coming from direct detection experiments and study the propagation of thermalised dark matter particles in the ground for the allowed values of the parameters. We consider a simple 1D diffusion and a more detailed 3D diffusion. In both cases the predicted signal has either the wrong phase of the annual modulation or a much larger amplitude of the diurnal modulation.
We propose a new realization of strongly interacting massive particles (SIMP) as self-interacting dark matter, where SIMPs couple to the Standard Model sector through an axion-like particle. Our model gets over major obstacles accompanying the original SIMP model, such as a missing mechanism of kinetically equilibrating SIMPs with the SM plasma as well as marginal perturbativity of the chiral Lagrangian density. Remarkably, the parameter region realizing $σ_{\rm self}/m_{\rm DM} \simeq 0.1 \textrm{--} 1 \, {\rm cm}^{2}/{\rm g}$ is within the reach of future beam dump experiments such as the Se…
