The European Physical Journal C

http://link.springer.com/journal/10052

List of Papers (Total 3,703)

On stability of a neutron star system in Palatini gravity

We formulate the generalized Tolman–Oppenheimer–Volkoff equations for the \(f(\hat{R})\) Palatini gravity in the case of static and spherical symmetric geometry. We also show that a neutron star can be a stable system independently of the form of the functional \(f(\hat{R})\).

Non-perturbative to perturbative QCD via the FFBRST

Recently a new type of quadratic gauge was introduced in QCD in which the degrees of freedom are suggestive of a phase of abelian dominance. In its simplest form it is also free of Gribov ambiguity. However this gauge is not suitable for usual perturbation theory. The finite field dependent BRST (FFBRST) transformation is a method established to interrelate generating functionals...

The minimal axion minimal linear \(\sigma \) model

The minimal SO(5) / SO(4) linear \(\sigma \) model is extended including an additional complex scalar field, singlet under the global SO(5) and the Standard Model gauge symmetries. The presence of this scalar field creates the conditions to generate an axion à la KSVZ, providing a solution to the strong CP problem, or an axion-like-particle. Different choices for the PQ charges...

White dwarfs with a surface electrical charge distribution: equilibrium and stability

The equilibrium configuration and the radial stability of white dwarfs composed of charged perfect fluid are investigated. These cases are analyzed through the results obtained from the solution of the hydrostatic equilibrium equation. We regard that the fluid pressure and the fluid energy density follow the relation of a fully degenerate electron gas. For the electric charge...

Stephani cosmology: entropically viable but observationally challenged

Inhomogeneous cosmological models such as the Stephani universes could, in principle, provide an explanation for the observed accelerated expansion of the Universe. Working with a concrete, popular model of the Stephani cosmology – the Stephani-Da̧browski model, we found that it is entropically viable. We also comment on the energy conditions and the two-sheeted geometry of the...

The cosmological nature of the dark Universe

This paper deals with the cancellation mechanism, which identifies the energy density of space-time expansion in an empty universe with the zero-point energy density and avoids the scale discrepancy with the observed energy density (cosmological constant problem). Using an intrinsic degree of freedom which describes the coupling of a variable cosmological term \(\varLambda...

Search for a new heavy gauge-boson resonance decaying into a lepton and missing transverse momentum in 36 fb \(^{-1}\) of pp collisions at \(\sqrt{s} = 13\) TeV with the ATLAS experiment

The results of a search for new heavy \(W^\prime \) bosons decaying to an electron or muon and a neutrino using proton–proton collision data at a centre-of-mass energy of \(\sqrt{s}~=~13\) TeV are presented. The dataset was collected in 2015 and 2016 by the ATLAS experiment at the Large Hadron Collider and corresponds to an integrated luminosity of 36.1 \(\text{ fb }^{-1}\). As...

Bouncing cosmological solutions from \(f(\mathsf{R,T})\) gravity

In this work we study classical bouncing solutions in the context of \(f(\mathsf{R},\mathsf{T})=\mathsf{R}+h(\mathsf{T})\) gravity in a flat FLRW background using a perfect fluid as the only matter content. Our investigation is based on introducing an effective fluid through defining effective energy density and pressure; we call this reformulation as the “effective picture...

Scalar pair production in a magnetic field in de Sitter universe

The production of scalar particles by the dipole magnetic field in de Sitter expanding universe is analyzed. The amplitude and probability of transition are computed using perturbative methods. A graphical study of the transition probability is performed obtaining that the rate of pair production is important in the early universe. Our results prove that in the process of pair...

Analysis of the structure of \(\Xi (1690)\) through its decays

The mass and pole residue of the first orbitally and radially excited \( \Xi \) state as well as the ground state residue are calculated by means of the two-point QCD sum rules. Using the obtained results for the spectroscopic parameters, the strong coupling constants relevant to the decays \(\Xi (1690)\rightarrow \Sigma K\) and \(\Xi (1690) \rightarrow \Lambda K\) are calculated...

Elliptic flow of electrons from beauty-hadron decays extracted from Pb–Pb collision data at \(\sqrt{s_\mathrm{NN}} = 2.76\ \hbox {TeV}\)

We present a calculation of the elliptic flow of electrons from beauty-hadron decays in semi-central Pb–Pb collisions at centre-of-mass energy per colliding nucleon pair, represented as \(\sqrt{s_\mathrm{NN}}\), of 2.76 TeV. The result is obtained by the subtraction of the charm-quark contribution in the elliptic flow of electrons from heavy-flavour hadron decays in semi-central...

A femtoscopic correlation analysis tool using the Schrödinger equation (CATS)

We present a new analysis framework called “Correlation Analysis Tool using the Schrödinger equation” (CATS) which computes the two-particle femtoscopy correlation function C(k), with k being the relative momentum for the particle pair. Any local interaction potential and emission source function can be used as an input and the wave function is evaluated exactly. In this paper we...

Wigner distributions for gluons

We investigate the gluon Wigner distributions for unpolarized, longitudinally polarized and transversely polarized target state. Instead of a nucleon, we take the target state to be a quark dressed with a gluon at one loop and investigate the gluon Wigner distributions at leading twist. Better numerical convergence is obtained compared to an earlier study, that removes the...

Improving sensitivity of a BEGe-based high-purity germanium spectrometer through pulse shape analysis

We performed Pulse Shape Analysis to separate single-scattered gamma energy deposition events from multiple-scattered photons in a high-sensitivity \(\gamma \)-ray spectrometer. The spectrometer is based on a Broad Energy High Purity Germanium detector and the developed technique uses multivariate analysis by an application of the Multi-Layer Perceptron Neural Network. A very...

Non-perturbative quark mass renormalisation and running in \(N_{\scriptstyle \mathrm{f}}=3\) QCD

We determine from first principles the quark mass anomalous dimension in \(N_{\scriptstyle \mathrm{f}}=3\) QCD between the electroweak and hadronic scales. This allows for a fully non-perturbative connection of the perturbative and non-perturbative regimes of the Standard Model in the hadronic sector. The computation is carried out to high accuracy, employing massless \(\text{ O...

The distribution of inelastic dark matter in the Sun

If dark matter is composed of new particles, these may become captured after scattering with nuclei in the Sun, thermalize through additional scattering, and finally annihilate into neutrinos that can be detected on Earth. If dark matter scatters inelastically into a slightly heavier (\({\mathcal {O}} (10-100)\,\hbox {keV}\)) state it is unclear whether thermalization occurs. One...

A type N radiation field solution with \(\Lambda <0\) in a curved space-time and closed time-like curves

An anti-de Sitter background four-dimensional type N solution of the Einstein’s field equations, is presented. The matter-energy content pure radiation field satisfies the null energy condition (NEC), and the metric is free-from curvature divergence. In addition, the metric admits a non-expanding, non-twisting and shear-free geodesic null congruence which is not covariantly...

On the trajectories of null and timelike geodesics in different wormhole geometries

The paper deals with an extensive study of null and timelike geodesics in the background of wormhole geometries. Starting with a spherically symmetric spacetime, null geodesics are analyzed for the Morris–Thorne wormhole (WH) and photon spheres are examined in WH geometries. Both bounded and unbounded orbits are discussed for timelike geodesics. A similar analysis has been done...

Gravitational decoupled anisotropies in compact stars

Simple generic extensions of isotropic Durgapal–Fuloria stars to the anisotropic domain are presented. These anisotropic solutions are obtained by guided minimal deformations over the isotropic system. When the anisotropic sector interacts in a purely gravitational manner, the conditions to decouple both sectors by means of the minimal geometric deformation approach are satisfied...

Stochastic dark energy from inflationary quantum fluctuations

We study the quantum backreaction from inflationary fluctuations of a very light, non-minimally coupled spectator scalar and show that it is a viable candidate for dark energy. The problem is solved by suitably adapting the formalism of stochastic inflation. This allows us to self-consistently account for the backreaction on the background expansion rate of the Universe where its...

Gauge symmetry and constraints structure for topologically massive AdS gravity: a symplectic viewpoint

By applying the Faddeev–Jackiw symplectic approach we systematically show that both the local gauge symmetry and the constraint structure of topologically massive gravity with a cosmological constant \(\Lambda \), elegantly encoded in the zero-modes of the symplectic matrix, can be identified. Thereafter, via a suitable partial gauge-fixing procedure, the time gauge, we calculate...

Calibration of high voltages at the ppm level by the difference of \(^{83{\mathrm{m}}}\) Kr conversion electron lines at the KATRIN experiment

The neutrino mass experiment KATRIN requires a stability of 3 ppm for the retarding potential at − 18.6 kV of the main spectrometer. To monitor the stability, two custom-made ultra-precise high-voltage dividers were developed and built in cooperation with the German national metrology institute Physikalisch-Technische Bundesanstalt (PTB). Until now, regular absolute calibration...

Fayet–Iliopoulos terms in supergravity and D-term inflation

We analyse the consequences of a new gauge invariant Fayet–Iliopoulos (FI) term proposed recently to a class of inflation models driven by supersymmetry breaking with the inflaton being the superpartner of the goldstino. We first show that charged matter fields can be consistently added with the new term, as well as the standard FI term in supergravity in a Kähler frame where the...

Estimating decay rate of \(X^{{\pm }}(5568)\rightarrow B_s\pi ^{{\pm }}\) while assuming them to be molecular states

Discovery of X(5568) brings up a tremendous interest because it is very special, i.e. made of four different flavors. The D0 collaboration claimed that they observed this resonance through portal \(X(5568)\rightarrow B_s\pi \), but unfortunately, later the LHCb, CMS, CDF and ATLAS collaborations’ reports indicate that no such state was found. Almost on the Eve of 2017, the D0...

Mass-induced instability of SAdS black hole in Einstein–Ricci cubic gravity

We perform the stability analysis of Schwarzschild-AdS (SAdS) black hole in the Einstein–Ricci cubic gravity. It shows that the Ricci tensor perturbations exhibit unstable modes for small black holes. We call this the mass-induced instability of SAdS black hole because the instability of small black holes arises from the massiveness in the linearized Einstein–Ricci cubic gravity...