Spinning particle in an external linearized gravitational wave field

We study the interaction of a scalar and a spinning particle with a coherent linearized gravitational wave field treated as a classical spin two external field. The spin degrees of freedom of the spinning particle are described by skew-commuting variables. We derive the explicit expressions for the eigenfunctions and the Green's functions of the theory. The discussion is exact within the approximation of neglecting radiative corrections and we prove that the result is completely determined by the semiclassical contribution.Comment: 11 page

Multiple Z' -> t-tbar signals in a 4D Composite Higgs Model

We study the production of top-antitop pairs at the Large Hadron Collider as a testbed for discovering heavy Z' bosons belonging to a composite Higgs model, as, in this scenario, such new gauge interaction states are sizeably coupled to the third generation quarks of the Standard Model. We study their possible appearance in cross section as well as (charge and spin) asymmetry distributions. Our calculations are performed in the minimal four-dimensional formulation of such a scenario, namely the 4-Dimensional Composite Higgs Model (4DCHM), which embeds five new $Z'$s. We pay particular attention to the case of nearly degenerate resonances, highlighting the conditions under which these are separable in the aforementioned observables. We also discuss the impact of the intrinsic width of the new resonances onto the event rates and various distributions. We confirm that the 14 TeV stage of the LHC will enable one to detect two such states, assuming standard detector performance and machine luminosity. A mapping of the discovery potential of the LHC of these new gauge bosons is given. Finally, from the latter, several benchmarks are extracted which are amenable to experimental investigation.Comment: 30 pages, 3 figures. Text and figures updated to match published versio

Particles with anomalous magnetic moment in external e.m. fields: the proper time formulation

In this paper we evaluate the expression for the Green function of a pseudo-classical spinning particle interacting with constant electromagnetic external fields by taking into account the anomalous magnetic and electric moments of the particle. The spin degrees of freedom are described in terms of Grassmann variables and the evolution operator is obtained through the Fock-Schwinger proper time method.Comment: 10 page

Foldy-Wouthuysen Transformation for a Spinning Particle with Anomalous Magnetic Moment

We study the Foldy-Wouthuysen transformation for a pseudoclassical particle with anomalous magnetic moment in an external, stationary electromagnetic field. We show that the transformation can be expressed in a closed form for neutral particles in purely electrostatic fields and for neutral and charged particles in external magnetostatic fields. The explicit expressions of the diagonalized Hamiltonians are calculated.Comment: 10 page

Production of Z' and W' via Drell-Yan processes in the 4D Composite Higgs Model at the LHC

We present an analysis of both the Neutral Current (NC) and Charged Current (CC) Drell-Yan processes at the LHC within a 4 Dimensional realization of a Composite Higgs model studying the cross sections and taking into account the possible impact of the extra fermions present in the spectrum.Comment: Conference proceeding, XII IFAE Edition, 3-5 April 2013, Cagliari. 2 pages, 2 figures; v2 typo correcte

A calculation of the QCD phase diagram at finite temperature, and baryon and isospin chemical potentials

We study the phases of a two-flavor Nambu-Jona-Lasinio model at finite temperature $T$, baryon and isospin chemical potentials: $\mu_{B}=(\mu_{u}+\mu_{d})/2$, $\mu_{I}=(\mu_{u}-\mu_{d})/2$. This study completes a previous analysis where only small isospin chemical potentials $\mu_{I}$ were consideredComment: 21 pages, 13 figures included, two more refernces adde

Higgs Boson in the 4DCHM: LHC phenomenology

Composite Higgs models provide an elegant solution to the hierarchy problem present in the Standard Model (SM) and give an alternative pattern leading to the mechanism of Electro-Weak Symmetry Breaking (EWSB). We present an analysis of the Higgs boson production and decay within a recently proposed realistic realization of this general idea: the 4D Composite Higgs Model (4DCHM). Comparing our results with the latest Large Hadron Collider (LHC) data we show that the 4DCHM could provide an alternative explanation with respect to the SM of the LHC results pointing to the discovery of a Higgs-like particle at 125 GeV.Comment: Conference proceeding, EPS-HEP 2013, 18-24 July 2013, Stockholm. 3 pages, 2 figures, typo correcte

Cornering pseudoscalar-mediated dark matter with the LHC and cosmology

Models in which dark matter particles communicate with the visible sector through a pseudoscalar mediator are well-motivated both from a theoretical and from a phenomenological standpoint. With direct detection bounds being typically subleading in such scenarios, the main constraints stem either from collider searches for dark matter, or from indirect detection experiments. However., LHC searches for the mediator particles themselves can not only compete with — or even supersede — the reach of direct collider dark matter probes, but they can also test scenarios in which traditional monojet searches become irrelevant, especially when the mediator cannot decay on-shell into dark matter particles or its decay is suppressed. In this work we perform a detailed analysis of a pseudoscalar-mediated dark matter simplified model, taking into account a large set of collider constraints and concentrating on the parameter space regions favoured by cos-mological and astrophysical data. We find that mediator masses above 100-200 GeV are essentially excluded by LHC searches in the case of large couplings to the top quark, while forthcoming collider and astrophysical measurements will further constrain the available parameter space

XQCAT: eXtra Quark Combined Analysis Tool

XQCAT (eXtra Quark Combined Analysis Tool) is a tool aimed at determining exclusion confidence levels for scenarios of new physics characterised by the presence of one or multiple heavy extra quarks which interact through Yukawa couplings with any of the Standard Model quarks. The code uses a database of efficiencies for pre-simulated processes of QCD-induced pair production of extra quarks and their subsequent on-shell decays. In the version 1.2 of XQCAT the efficiencies have been computed for a set of seven publicly available search results by the CMS experiment. The input for the code is a text file in which masses, branching ratios and dominant chirality of the couplings of the new quarks are provided. The output of the code is the exclusion confidence levels of the test point for each implemented experimental analysis considered individually and, when possible, in statistical combination.Comment: 18 pages, 2 figures, version accepted for publication in Comp. Phys. Comm., fixed formatting problems caused by the arXiv's autotex syste