Dimiter Hadjimichef

Do glueballs contribute in heavy-ion collisions?

In heavy-ion collision simulations many hadron states and/or parton degrees of freedom are included in order to obtain the observables. Meson spectroscopy, for example, considers the 0++ meson as a mixture of and glue. This fact is usually not considered in heavy-ion collision physics. In the present work, we consider two extreme possibilities for the constitution of the 0++ meson, either as a pure glueball or as meson. The scattering amplitude and cross sections with constituent interchange are determined for the two situations. The comparison showed that the glueball–glueball elastic scattering cross section for a colour singlet state is between one to two orders of magnitude smaller than the corresponding state. The 2++ glueball–glueball interaction is also evaluated with similar behaviour. Thus, glueball–glueball scattering is not very likely to introduce significant changes in heavy-ion collision observables.

On the possibility of a 130 GeV gamma-ray line from annihilating singlet fermionic dark matter

There is evidence for a spectral line at Eγ ≈ 130 GeV in the Fermi -LAT data that can be explained as dark mater particles annihilating into photons. We review a well known dark matter model that consists in a singlet Dirac fermion and a singlet scalar. The scalar implements spontaneous symmetry breaking in the dark sector, and is responsible for the communication between dark matter and standard model particles through a coupling to the Higgs. These interactions are suppressed by the mixing between the scalar and the Higgs. Therefore, the singlet fermionic dark matter is naturally a weakly interacting massive particle (WIMP) and can explain the observed relic density. We show that this model cannot produce the signal identified in the Fermi -LAT data. Thus, we propose a modification in the model by introducing a new scalar multiplet that carries electric charge and couples to the singlet scalar. It enhances the annihilation into two photons and succeeds in producing the observed signal. We also discuss the resulting increase of the branching ratio of the h γγ process, which is consistent with measurements from the CMS experiments. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

GLUEBALL-DILATON AS AN ALTERNATIVE TO DARK MATTER IN NEUTRON STARS

We study cold nuclear matter based on a mean field description of baryons bound by the exchange of scalar-isoscalar, vector-isoscalar, scalar-isovector and vector-isovector meson fields as well as the glueball field. For this task, we use an extended version of the effective model with derivative couplings with genuine many-body forces simulated by nonlinear self-couplings and meson-meson interaction terms involving scalar-isoscalar (σ, σ*), vector-isoscalar (ω, ɸ), vector-isovector (ϱ), scalar-isovector (δ) meson and the glueball fields. In our approach, the realization of the broken scale invariance of quantum chromodynamics is achieved through the introduction of a dilaton field. The effective model with dilatons is the applied to the description of neutron stars.

AN EFFECTIVE THEORY FOR NUCLEAR MATTER WITH GENUINE MANY-BODY FORCES

Nuclear science has developed many excellent descriptions that embody various properties of the nucleus, and nuclear matter at low, medium and high densities. However, a full microscopic understanding of nuclear systems is still lacking. The aim of our theoretical research group is to shed some light on such challenges and particularly on open questions facing the high density nuclear many-body problem. Here we focus our attention on the conceptual issue of naturalness and its role in shaping the baryon-meson phase space dynamics in the description of the equation of state (EoS) of nuclear matter. In particular, in order to stimulate possible new directions of research, we discuss relevant aspects of a recently developed relativistic effective theory for nuclear matter with natural parametric couplings and genuine many-body forces. Among other topics we discuss in this work the connection of this theory with other known effective QHD models of the literature and its potentiality in describing a new physic...

Effective Field Theory for Neutron Stars with Genuine Many-body Forces

The aim of our contribution is to shed some light on open questions facing the high density nuclear many-body problem. We focus our attention on the conceptual issue of naturalness and its role for the baryon-meson coupling for nuclear matter at high densities. As a guideline for the strengths of the various couplings the concept of naturalness has been adopted. In order to encourage possible new directions of research, we discuss relevant aspects of a relativistic effective theory for nuclear matter with “natural” parametric couplings and genuine many-body forces. Among other topics, we discuss in this work the connection of this theory with other known effective Quantum Hadrodynamics (QHD) models found in literature and how we can potentially use our approach to describe new physics for neutron stars. We also show some preliminary results for the equation of state, population profiles and mass-radius relation for neutron stars assuming local charge neutrality and beta equilibrium. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

CP violation in dual dark matter

In this paper, we study the consequences of extending dual symmetry (DuSy) to include a generic Cµ vector field as a dual partner of the photon Aµ. A new combined field, the complex Z′µ, is obtained from Cµ and Aµ. The promotion of dual symmetry to a local symmetry for Z′µ implies the inclusion of an extra complex vector field Wµ with a complex gauge transformation. A dual dark matter (DM) Lagrangian LDDM is obtained from the general DuSy invariant Lagrangian LDuSy. Our tentative conjecture is to interpret W±µ as the actual weak interaction charged gauge boson W μ ±, which leads us to speculate about a possible extra CP violation scenarios for future calculations. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Bound State Correction in CP Violation

We study hadronic weak decays using an approach which consists in a mapping technique, the Fock-Tani formalism, in order to obtain an effective weak Hamiltonian starting from a contact microscopic interaction. An additional effect is manifest in this formalism associated to the extended nature of mesons: bound-state corrections which can be related to CP violation parameters.

Mimetic Dark Matter in Pseudo-Complex General Relativity

We investigate the dark matter problem in the context of Pseudo-complex General Relativity. A form of gravitational dark matter has recently been studied, the mimetic dark matter, which is a scalar tensor extension for gravity where the conformal degree of freedom is isolated in a covariant way. For such, we perform a combination of both approaches to reveal non trivial results even in the absence of matter. Solutions for different scenarios and possible interpretations are presented.

The Ds1(2536)+ Decay Widths in the C3P0 Model

The Fock-Tani representation is a field theory formalism appropriated for the simultaneous treatment of composite particles and their constituents. The 3P0 model is a typical decay model which considers only OZI-allowed strong decays. The model considers a quark-antiquark pair created with the vacuum quantum numbers in the presence of the initial state meson. It is described as the non-relativistic limit of the pair creation Hamiltonian. Applying the Fock-Tani transformation to the microscopic Hamiltonian of the pair creation produces the characteristic expansion in powers of the wavefunction, where the 3P0 model is the lowest order in the expansion. The corrected 3P0 model (C3P0) is obtained from higher orders in the expansion, by the introduction of the bound state kernel Δ, called the bound state correction. The goal of this work is to study the application of the 3P0 model and C3P0 model in detail for the strange charmed meson sector (DSJ meson). In particular, we shall calculate the decay amplitudes ...

Photon-Photon Interaction in Glueball Production

In the last years many exotic states have been identified in several colliders around the world. One of the exotic states provided in QCD is the glueball. Using a non-relativistic gluon bound-state model, we compute Γ(G → γγ), where G is a pseudoscalar, tensor, or scalar digluon. For the starting from the amplitudes we considers the process γγ → g∗g∗ at threshold, where the amplitudes are obtained in perturbative QCD at lowest order by deriving them from QED calculation and the g∗s are massive constituent gluons. In this calculation the unknown parameters of the model, such as the digluon wave function, are obtained using measured values of Γ(J/Ψ → Gγ). Our theorical results are compared with the present experimental limits for the various glueballs candidates.