Search

The singly charged $SU(2)_L$ singlet scalar is one of the very interesting new particles, as it can generate neutrino masses at loop level, produce contributions to various flavour observables. We study the possibility of detecting this kind of scalar predicted by the singly-charged scalar model at ILC via the lepton flavour violation (LFV) process $e^+e^-\rightarrow S^+S^-\rightarrow \mu e + {E\mkern-10.5 mu/}$. Considering the constraints on the free parameters, we obtain the expected sensitivities of the ILC with the center of mass energy $\sqrt{s}=1~\mathrm{TeV}$ and the integrated luminosity $\mathcal{L}=$ $1.5~\mathrm{ab}^{-1}$ to the parameter space of the singly-charged scalar model. The prospective excluded mass range at $95\%$ C.L. is $M_S \gtrsim 470~\mathrm{GeV}$, $410~\mathrm{GeV}$ for the branching ratio $\mathcal{B}_{\mu e}$ = $100\%$ , $50\%$, respectively, while the scalar with $M_S \gtrsim 300~\mathrm{GeV}$ is excluded at $95\%$ C.L. for $\mathcal{B}_{\mu e}$ = $30\%$.

Mathematically, topological invariants arise from the parallel transport of eigenstates on the energy bands, which, in physics, correspond to the adiabatic dynamical evolution of transient states. It determines the presence of boundary states, while lacking direct measurements. Here, we develop time-varying programmable coupling circuits between acoustic cavities to mimic the Hamiltonians in the Brillouin zone, with which excitation and adiabatic evolution of bulk states are realized in a unit cell. By extracting the Berry phases of the bulk band, topological invariants, including the Zak phase for the SSH model and the Chern number for the AAH model, are obtained convincingly. The bulk state evolution also provides insight into the topological charges of our newly developed non-Abelian models, which are also verified by observing the adiabatic eigenframe rotation. Our work not only provides a general recipe for telling various topological invariants but also sheds light on transient acoustic wave manipulations., Comment: 16 pages, 4 figures

We explore the possibility of detecting the couplings of axion-like particle (ALP) with leptons from their loop-level impact on the ALP couplings to electroweak (EW) gauge bosons via the signal process $e^+ e^- \to \gamma \gamma /E$ at the Circular Electron Positron Collider (CEPC) and obtain prospective sensitivities to the ALP-lepton couplings. Our numerical results show that the CEPC with the center of mass energy $\sqrt{s}=240$ GeV and the integrated luminosity $\mathcal{L}=$ $5.6$ ab$^{-1}$ might be sensitive for probing the ALP-lepton couplings in the ALP mass range from $10$ GeV to $130$ GeV, where the prospective sensitivities to the ALP-neutrino coupling $Tr(g_{a\nu\nu})/f_a$ can be as low as $0.016$ GeV$^{-1}$ and $0.0031$ GeV$^{-1}$ for $c_{R}=0$ and $c_{R}=c_{L}$, and to the ALP-charged lepton coupling $Tr(g_{a\ell\ell})/f_a$ can be as low as $0.035$ GeV$^{-1}$ for $c_{L}=0$. We find that the prospective sensitivities given by the CEPC are not covered by the current exclusion regions in some ALP mass intervals. The CEPC has the potential for exploring the ALP-neutrino couplings via some promising processes induced by the ALP-EW gauge boson couplings in the future.

Spin and orbital angular momenta are fundamental physical characteristics described by polarization and spatial degrees of freedom, respectively. Polarization is a feature of vector fields while spatial phase gradient determines the orbital angular momentum ubiquitous to any scalar field. Common wisdom treats these two degrees of freedom as distinct and independent principles to manipulate wave propagations. Here, we demonstrate their synergy. This is achieved by introducing two orthogonal $p$-orbitals as eigenbases, whose spatial modal features are exploited to generate orbital angular momenta and the associated orbital orientations provide means to simultaneously manipulate polarizations. Through periodic modulation and directional coupling, we realize a full cyclic evolution of the synchronized and synergized spin-orbital angular momenta. Remarkably, this evolution acquires a nontrivial geometric phase, leading to its representation on a M\"obius strip. Experimentally, an acoustic cavity array is designed, whose dipole resonances precisely mimic the $p$-orbitals. The acoustic waves, uniquely, see the pressure (scalar) field as a spatial feature and carry an intrinsic polarization defined by the velocity (vector) field, serving as an ideal platform to observe the synergy of spin and orbital angular momenta. Based on such a property, we further showcase a spin-orbital-Hall effect, highlighting the intricate locking of handedness, directionality, spin density and spatial mode profile. Our study unveils a fundamental connection between spin and orbital angular momenta, promising avenues for novel applications in information coding and high-capacity communications.