International Journal of Modern Physics A

Bent silicon crystals mounted on high-accuracy angular actuators were installed in the CERN Super Proton Synchrotron (SPS) and extensively tested to assess the feasibility of crystal-assisted collimation in circular hadron colliders. The adopted layout was exploited and regularly upgraded for about a decade by the UA9 Collaboration. The investigations provided the compelling evidence of a strong reduction of beam losses induced by nuclear inelastic interactions in the aligned crystals in comparison with amorphous orientation. A conceptually similar device, installed in the betatron cleaning insertion of CERN Large Hadron Collider (LHC), was operated through the complete acceleration and storage cycle and demonstrated a large reduction of the background leaking from the collimation region and radiated into the cold sections of the accelerator and the experimental detectors. The implemented layout and the relevant results of the beam tests performed in the SPS and in the LHC with stored proton and ion beams are extensively discussed.

The aim of this work is to investigate the occurrence of two different spontaneous symmetry breakings at two levels of the description of fermion-scalar field model, by means of a set of gap equations and with a background field effective action. For that, we consider the Yukawa model, as a toy model for interactions between nonmassive fermions intermediated by a self-interacting real scalar field. This model has at stake two symmetries at the classical level that, as we know, might be spontaneously or dynamically broken with mass generation for the particles. The auxiliary field method is considered and it produces coupled renormalized gap equations. The effective action is then written with quantum contributions by the external background field method. We brought to light how the renormalization procedure affects the physical gaps, investigate its properties, and discuss the connection between the auxiliary fields not only to define composite states but also to compute the effective action.

In this paper, we analyze the loop-induced decays of neutral Higgs boson $h$ into pairs of photons, gluons and $Z\gamma$ in 3-Higgs Doublet Models (3HDMs), where all the doublets have nonzero vacuum expectation values. In the 3HDM, there are contributions to these decays from loops of charged scalars $H_{1,2}^{\pm }$ that are not present in the Standard Model. We find an enhancement in the channel $h\to Z\gamma$ with respect to the Standard Model prediction in some parameter region while respecting constraints from the measurements of $h\to \gamma \gamma$ at the LHC. The charged Higgs bosons $H_{1,2}^{\pm }$ lead to the enhancement of $Z\gamma$ decay mode in some part of the parameter space of the 3HDM. Then, we discuss the correlations between the decay modes $h\to Z\gamma$ and $h\to \gamma \gamma$. Moreover, we study Type-I and Type-Z of 3HDMs and find that these types of 3HDMs can be distinguished via only the gluonic decays, since the contributions of the $H_{1,2}^{\pm }$ loops are dominant to those of fermion loops. We also investigate the effects of the model parameters on these loop-induced decays. As an interesting phenomenological consequence, the 3HDM is dominantly governed by the parameters: two ratios of vacuum expectation values (VEVs); $tan\gamma$, $tan\beta$ and the mixing angles of the CP-even Higgs bosons, ${\alpha }_{1,2}$ and $𝜃$.

In this work, we study an explicit calculation of the deformed Pauli–Schrödinger oscillator for nonrelativistic charged spin 1/2 particle in momentum space with Snyder–de Sitter model, where the energy eigenvalues are given in their exact forms, and the corresponding radial wave functions are expressed in associated Jacobi polynomials. We have also studied the effect of the spatial deformation parameter on the bound states of our system.

Rare electromagnetic (EM) decays of charmed mesons are useful laboratories to explore the structure of hadronic states and the interactions between photons and charmed mesons, to test the chiral perturbation theory in flavor sector and to search for new physics including dark photons. In this paper, we calculate the relative branching ratios of EM Dalitz decays $D_{(s)}^{\ast }\to D_{(s)}{\ell }^{+}{\ell }^{-}$ to their corresponding radiative decays $D_{(s)}^{\ast }\to D_{(s)}\gamma$ with transition form factor in vector-meson dominance model, where $D_{(s)}^{\ast }$ represents $D^{\ast }{(2007)}^0$, $D^{\ast }{(2010)}^{\pm }$, $D^{\ast }{(2640)}^{\pm }$, $D_s^{\ast \pm }$, $D_{s1}^{\ast }{(2700)}^{\pm }$ and $D_{s1}^{\ast }{(2860)}^{\pm }$. The corresponding dileptonic invariant mass spectra and the leptonic angular distributions are also presented.

In this paper, we mainly investigate the constrained Kadomtsev–Petviashvili (KP) and modified KP (mKP) hierarchies. Squared eigenfunction (SE) symmetry is an important symmetry defined by eigenfunctions and adjoint eigenfunctions, which can be viewed as the generator of the additional symmetries. Due to special constraints on the Lax operators, it is found that there are three different cases for the generating eigenfunctions and adjoint eigenfunctions of the SE symmetries. Then we discuss the changes of the SE symmetries under the Miura links between the KP and mKP hierarchies. Next, the exponential of the SE symmetries is shown to be the binary Darboux transformations. At last based upon the results above, new additional symmetries for the constrained KP and mKP hierarchies are constructed, different from the additional Virasoro symmetries defined by Aratyn.

A consistent QM/NCG duality is put forward as a model for the ${\mathrm{\text{AdS}}}^2/{\mathrm{\text{CFT}}}_1$ correspondence. This is a duality/correspondence between (1) the dAFF conformal quantum mechanics (QM) on the boundary (which is only “quasi-conformal” in the sense that there is neither an $SO(1,2)$-invariant vacuum state nor there are strictly speaking primary operators), and between (2) the noncommutative geometry of ${\mathrm{\text{AdS}}}_{𝜃}^2$ in the bulk (which is only “quasi-AdS” in the sense of being only asymptotically ${\mathrm{\text{AdS}}}^2$). The Laplacian operators on noncommutative ${\mathrm{\text{AdS}}}_{𝜃}^2$ and commutative ${\mathrm{\text{AdS}}}^2$ have the same spectrum and thus their correlators are conjectured to be identical. These bulk correlation functions are found to be correctly reproduced by appropriately defined boundary quantum observables in the dAFF quantum mechanics. Moreover, these quasi-primary operators on the boundary form a subalgebra of the operator algebra of noncommutative ${\mathrm{\text{AdS}}}_{𝜃}^2$.

In this paper, we present the construction of noncommutative ${\mathrm{\text{AdS}}}_{𝜃}^2$ black hole and its four-dimensional Yang–Mills IKKT-type matrix model which includes two competing Myers term one responsible for the condensation of pure ${\mathrm{\text{AdS}}}_{𝜃}^2$ and the other one responsible for the condensation of the dilaton field. It is argued that the phase diagram of this matrix model features three phases: (1) a gravitational phase (${\mathrm{\text{AdS}}}_{𝜃}^2$ black hole), (2) a geometric phase (${\mathrm{\text{AdS}}}_{𝜃}^2$ background) and (3) a Yang–Mills phase. The Hawking process is therefore seen as an exotic line of discontinuous transitions between the gravitational and geometrical phases. Alternatively, a noncommutative nonlinear sigma model describing the transition of the dilaton field between the gravitational and geometrical phases is also constructed.

The near-horizon noncommutative geometry of black holes, given by ${\mathrm{\text{AdS}}}_{𝜃}^2\times {𝕊}_N^2$, is discussed and the phase structure of the corresponding Yang–Mills matrix models is presented. The dominant phase transition as the system cools down, i.e. as the gauge coupling constant is decreased is an emergent geometry transition between a geometric noncommutative ${\mathrm{\text{AdS}}}_{𝜃}^2\times {𝕊}_N^2$ phase (discrete spectrum) and a Yang–Mills matrix phase (continuous spectrum) with no background geometrical structure. We also find a possibility for topology change transitions in which space or time directions grow or decay as the temperature is varied. Indeed, the noncommutative near-horizon geometry ${\mathrm{\text{AdS}}}_{𝜃}^2\times {𝕊}_N^2$ can evaporate only partially to a fuzzy sphere ${𝕊}_N^2$ (emergence of time) or to a noncommutative anti-de Sitter space–time ${\mathrm{\text{AdS}}}_{𝜃}^2$ (topology change).

We construct new Darboux transformations for one-dimensional stationary Dirac and Klein–Gordon equations. The transformed solutions and potentials are expressed in closed form through generalized Wronskians. A reality condition for the transformed potentials is derived.

In this work, we discuss the stability analysis of generalized ghost dark energy (GGDE) and new holographic dark energy (NHDE) in the framework of Chameleon Brans–Dicke (CBD) gravity. The adiabatic squared sound speed $v_s^2$ plays a crucial role to analyze the stability of the models. We know that the models are stable if $v_s^2>0$ and unstable if $v_s^2<0$. We study the interacting and noninteracting versions of GGDE and NHDE with dark matter in CBD model in a nonflat FLRW universe. We also try to show that in all cases of investigation, the models are classically stable with suitable choices of parameters. Finally, we analyze the perturbative analysis for both GGDE and NHDE models in the background of CBD gravity.

The elliptically oscillating solutions in the Abelian–Higgs model are presented and the classical massive-dispersion-relation through the nonlinear dynamics is discussed. The generated massive-dispersion-relation including a field value of the scalar field is derived as the consequence of the equation of motions. We discuss the property of the new solutions and its Hamiltonian density. In addition, we calculate the electromagnetic property of the system, in particular, we derive the relation between the field value and the electric field and the electric current density.