# The European Physical Journal C

## List of Papers (Total 3,408)

#### Dark matter stability and one-loop neutrino mass generation based on Peccei–Quinn symmetry

We propose a model which is a simple extension of the KSVZ invisible axion model with an inert doublet scalar. Peccei–Quinn symmetry forbids tree-level neutrino mass generation and its remnant $Z_2$ symmetry guarantees dark matter stability. The neutrino masses are generated by one-loop effects as a result of the breaking of Peccei–Quinn symmetry through a nonrenormalizable ...

#### New signals for vector-like down-type quark in U(1) of $E_6$

We consider the pair production of vector-like down-type quarks in an $E_6$ motivated model, where each of the produced down-type vector-like quark decays into an ordinary Standard Model light quark and a singlet scalar. Both the vector-like quark and the singlet scalar appear naturally in the $E_6$ model with masses at the TeV scale with a favorable choice of symmetry breaking ...

#### Interaction between two point-like charges in nonlinear electrostatics

We consider two point-like charges in electrostatic interaction within the framework of a nonlinear model, associated with QED, that provides finiteness of their field energy. We find the common field of the two charges in a dipole-like approximation, where the separation between them R is much smaller than the observation distance r : with the linear accuracy with respect to the ...

#### The quest for $\mu \rightarrow e \gamma$ and its experimental limiting factors at future high intensity muon beams

The search for the lepton flavor violating decay $\mu ^+ \rightarrow e^+ \gamma$ will reach an unprecedented level of sensitivity within the next five years thanks to the MEG-II experiment. This experiment will take data at the Paul Scherrer Institut where continuous muon beams are delivered at a rate of about $10^8$ muons per second. On the same time scale, accelerator ...

#### Pentaquarks with hidden charm as hadroquarkonia

We consider hidden charm pentaquarks as hadroquarkonium states in a QCD inspired approach. Pentaquarks arise naturally as bound states of quarkonia excitations and ordinary baryons. The LHCb $P_c(4450)$ pentaquark is interpreted as a $\psi '$-nucleon bound state with spin-parity $J^P=3/2^-$. The partial decay width $\varGamma (P_c(4450)\rightarrow J/\psi +N)\approx 11$ MeV ...

#### Emergent cosmos in Einstein–Cartan theory

Based on Padmanabhan’s proposal, the accelerated expansion of the universe can be driven by the difference between the surface and bulk degrees of freedom in a region of space, described by the relation $\mathrm{d}V/\mathrm{d}t = N_\mathrm{sur}-N_\mathrm{bulk}$ where $N_\mathrm{sur}$ and $N_\mathrm{bulk}= -N_\mathrm{em} +N_\mathrm{de}$ are the degrees of freedom assigned to ...

#### A new look at the Y tetraquarks and $\Omega _c$ baryons in the diquark model

We analyze the hidden charm P-wave tetraquarks in the diquark model, using an effective Hamiltonian incorporating the dominant spin–spin, spin–orbit and tensor interactions. We compare with other P-wave systems such as P-wave charmonia and the newly discovered $\Omega _c$ baryons, analysed recently in this framework. Given the uncertain experimental situation on the Y states, we ...

#### On the effect of renormalization group improvement on the cosmological power spectrum

Asymptotically safe quantum gravity predicts running gravitational and cosmological constants, while it remains a meaningful quantum field theory because of the existence of a finite number of non-Gaussian ultraviolet fixed points. We have investigated the effect of such running couplings on the cosmological perturbations. We have obtained the improved Mukhanov–Sassaki equation and ...

#### Anisotropic generalization of well-known solutions describing relativistic self-gravitating fluid systems: an algorithm

We present an algorithm to generalize a plethora of well-known solutions to Einstein field equations describing spherically symmetric relativistic fluid spheres by relaxing the pressure isotropy condition on the system. By suitably fixing the model parameters in our formulation, we generate closed-form solutions which may be treated as an anisotropic generalization of a large class ...

#### Functional perturbative RG and CFT data in the $\epsilon$ -expansion

We show how the use of standard perturbative RG in dimensional regularization allows for a renormalization group-based computation of both the spectrum and a family of coefficients of the operator product expansion (OPE) for a given universality class. The task is greatly simplified by a straightforward generalization of perturbation theory to a functional perturbative RG approach. ...

#### Analysis of the scalar, axialvector, vector, tensor doubly charmed tetraquark states with QCD sum rules

In this article, we construct the axialvector-diquark–axialvector-antidiquark type currents to interpolate the scalar, axialvector, vector, tensor doubly charmed tetraquark states, and study them with QCD sum rules systematically by carrying out the operator product expansion up to the vacuum condensates of dimension 10 in a consistent way, the predicted masses can be confronted ...

#### Regge-like relation and a universal description of heavy–light systems

Using the Regge-like formula $(M-m_Q)^2=\pi \sigma L$ between hadron mass M and angular momentum L with a heavy quark mass $m_Q$ and a string tension $\sigma$, we analyze all the heavy–light systems, i.e., $D/D_s/B/B_s$ mesons and charmed and bottom baryons. Numerical plots are obtained for all the heavy–light mesons of experimental data whose slope becomes nearly equal to ...

#### SpecBit, DecayBit and PrecisionBit: GAMBIT modules for computing mass spectra, particle decay rates and precision observables

We present the GAMBIT modules SpecBit, DecayBit and PrecisionBit. Together they provide a new framework for linking publicly available spectrum generators, decay codes and other precision observable calculations in a physically and statistically consistent manner. This allows users to automatically run various combinations of existing codes as if they are a single package. The ...

#### The minimal GUT with inflaton and dark matter unification

Giving up the solutions to the fine-tuning problems, we propose the non-supersymmetric flipped $SU(5)\times U(1)_X$ model based on the minimal particle content principle, which can be constructed from the four-dimensional SO(10) models, five-dimensional orbifold SO(10) models, and local F-theory SO(10) models. To achieve gauge coupling unification, we introduce one pair of ...

#### Hyperunified field theory and gravitational gauge–geometry duality

A hyperunified field theory is built in detail based on the postulates of gauge invariance and coordinate independence along with the conformal scaling symmetry. All elementary particles are merged into a single hyper-spinor field and all basic forces are unified into a fundamental interaction governed by the hyper-spin gauge symmetry SP(1, $D_h-1$). The dimension $D_h$ of ...

#### Einstein and Rastall theories of gravitation in comparison

We profit by a recent paper of Visser claiming that Rastall gravity is equivalent to Einstein gravity to compare the two gravitational theories in a general way. Our conclusions are different from Visser’s ones. We indeed argue that these two theories are not equivalent. In fact, Rastall theory of gravity is an “open” theory when compared to Einstein general theory of relativity. ...

#### Relativistic quantum motion of spin-0 particles under the influence of noninertial effects in the cosmic string spacetime

We study solutions for the Klein–Gordon equation with vector and scalar potentials of the Coulomb types under the influence of noninertial effects in the cosmic string spacetime. We also investigate a quantum particle described by the Klein–Gordon oscillator in the background spacetime generated by a cosmic string. An important result obtained is that the noninertial effects ...

#### Mitigation of $^{42}$ Ar/ $^{42}$ K background for the GERDA Phase II experiment

Background coming from the $^{42}$Ar decay chain is considered to be one of the most relevant for the Gerda experiment, which searches for the neutrinoless double beta decay of $^{76}$Ge. The sensitivity strongly relies on the absence of background around the Q-value of the decay. Background coming from $^{42}$K, a progeny of $^{42}$Ar, can contribute to that background via ...

#### Jets in a strongly coupled anisotropic plasma

In this paper, we study the dynamics of the light quark jet moving through the static, strongly coupled ${\mathcal {N}}=4$, anisotropic plasma with and without charge. The light quark is presented by a 2-parameters point-like initial condition falling string in the context of the AdS/CFT. We calculate the stopping distance of the light quark in the anisotropic medium and compare ...

#### Search for dark matter produced in association with bottom or top quarks in $\sqrt{s}=13$ TeV pp collisions with the ATLAS detector

A search for weakly interacting massive dark-matter particles produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and missing transverse momentum are considered. The analysis uses $36.1 \; \mathrm {fb}^{-1}$ of proton–proton collision data recorded by the ATLAS experiment at $\sqrt{s}=13$ TeV in 2015 and 2016. No ...

#### On the emergence of the $\mathbf{\Lambda }$ CDM model from self-interacting Brans–Dicke theory in $\mathbf{d= 5}$

We investigate whether a self-interacting Brans–Dicke theory in $d=5$ without matter and with a time-dependent metric can describe, after dimensional reduction to $d=4$, the FLRW model with accelerated expansion and non-relativistic matter. By rewriting the effective 4-dimensional theory as an autonomous 3-dimensional dynamical system and studying its critical points, we show ...

#### The decay width of the $Z_c(3900)$ as an axialvector tetraquark state in solid quark–hadron duality

In this article, we tentatively assign the $Z_c^\pm (3900)$ to be the diquark–antidiquark type axialvector tetraquark state, study the hadronic coupling constants $G_{Z_cJ/\psi \pi }, G_{Z_c\eta _c\rho }, G_{Z_cD \bar{D}^{*}}$ with the QCD sum rules in details. We take into account both the connected and disconnected Feynman diagrams in carrying out the operator product ...

#### Forecast and analysis of the cosmological redshift drift

The cosmological redshift drift could lead to the next step in high-precision cosmic geometric observations, becoming a direct and irrefutable test for cosmic acceleration. In order to test the viability and possible properties of this effect, also called Sandage–Loeb (SL) test, we generate a model-independent mock data set in order to compare its constraining power with that of ...

#### Production of $\tau \tau jj$ final states at the LHC and the TauSpinner algorithm: the spin-2 case

The TauSpinner algorithm is a tool that allows one to modify the physics model of the Monte Carlo generated samples due to the changed assumptions of event production dynamics, but without the need of re-generating events. With the help of weights $\tau$-lepton production or decay processes can be modified accordingly to a new physics model. In a recent paper a new version ...