The $$R^2$$-Higgs inflation with two Higgs doublets

We study $$R^2$$ R 2 -Higgs inflation in a model with two Higgs doublets in which the Higgs sector of the Standard Model is extended by an additional Higgs doublet, thereby four scalar fields are involved in the inflationary evolutions. We first derive the set of equations required to follow the inflationary dynamics in this two Higgs doublet model, allowing a nonminimal coupling between the Higgs-squared and the Ricci scalar R, as well as the $$R^2$$ R 2 term in the covariant formalism. By numerically solving the system of equations, we find that, in parameter space where a successful $$R^2$$ R 2 -Higgs inflation are realized and consistent with low energy constraints, the inflationary dynamics can be effectively described by a single slow-roll formalism even though four fields are involved in the model. We also argue that the parameter space favored by $$R^2$$ R 2 -Higgs inflation requires nearly degenerate masses for $$m_{\mathsf {H}}$$ m H , $$m_A$$ m A and $$m_{{\mathsf {H}}^{\pm }}$$ m H ± , where $${\mathsf {H}}$$ H , A, and $${\mathsf {H}}^{\pm }$$ H ± are the extra CP even, CP odd, and charged Higgs bosons in the general two Higgs doublet model taking renormalization group evolutions of the parameters into account. Discovery of such heavy scalars at the Large Hadron Collider (LHC) are possible if they are in the sub-TeV mass range. Indirect evidences may also emerge at the LHCb and Belle-II experiments, however, to probe the quasi degenerate mass spectra one would likely require high luminosity LHC or future lepton colliders such as the International Linear Collider and the Future Circular Collider.

$e^+e^-\gamma$ production at photon-photon colliders at complete electroweak NLO accuracy

We present the full NLO electroweak radiative corrections to $e^+e^-\gamma$ production in $\gamma\gamma$ collision, which is an ideal channel for calibrating the beam luminosity of Photon Linear Collider. We analyse the dependence of the total cross section on the beam colliding energy, and investigate the kinematic distributions of final particles at various initial photon beam polarizations at EW NLO accuracy. The numerical results show that the EW relative corrections to the total cross section are non-negligible and become more and more significant as the increase of the beam colliding energy, even can exceed $-10\%$ in $\text{J} = 2$ $\gamma\gamma$ collision at $\sqrt{\hat{s}}=1~ \text{TeV}$. Such EW corrections are very important and should be taken into consideration in precision theoretical and experimental studies at high-energy $\gamma\gamma$ colliders.

A high-luminosity superconducting twin e+e- linear collider with energy recovery

Superconducting technology makes it possible to build a high energy e+e- linear collider with energy recovery (ERLC) and reusable beams. To avoid parasitic collisions inside the linacs, a twin (dual) LC is proposed. In this article, I consider the principle scheme of the collider and estimate the achievable luminosity, which is limited by collision effects and available power. Such a collider can operate in a duty cycle (DC) and in a continuous (CW) modes, if sufficient power. With current SC Nb technology (T = 1.8 K, f RF = 1.3 GHz, used for ILC) and with power P = 100 MW, a luminosity L ∼ 0.33 × 1036 cm-2 s-1 is possible at the Higgs factory with 2E 0 = 250 GeV. Using superconductors operating at 4.5 K with high Q 0 values, such as Nb3Sn, and f RF = 0.65 GHz, the luminosity can reach L ∼ 1.4 × 1036 cm-2 s-1 at 2EE0 = 250 GeV (with P = 100 MW) and L ∼ 0.8 × 1036 cm-2 s-1 at 2E 0 = 500 GeV (with P = 150 MW), which is almost two orders of magnitude greater than at the ILC, where the beams are used only once. This technology requires additional efforts to obtain the required parameters and reliably operation. Such a collider would be the best machine for precision Higgs studies, including the measurement of Higgs self-coupling.

Phenomenology of dark matter and mirror fermions from a left-right mirror model with singlet scalar

We investigate a left-right mirror model with SU(3)c×SU(2)L×SU(2)R×U(1)Y and a discrete Z2 symmetry, which introduces mirror fields that are copies of the standard model fields. The mirror fields have the opposite chirality to their standard model counterpart fields. We also introduce singlet scalars as dark matter. The new interaction between dark matter, standard model fermions, and mirror fermions can account for dark matter abundance, charged lepton flavor violation, lepton anomalous magnetic moment, and flavor changing neutral current. We demonstrated that if we choose dark matter annihilation into muon as the dominant annihilation channel for leptophilic dark matter, both the observed dark matter abundance and the observed discrepancy between theory and experiment in the muon anomalous magnetic moment can be explained without contradicting the bound derived from charged lepton flavor violating processes. We briefly discuss how mirror fermions will be produced at the future linear collider, as mirror fermions can interact with neutral gauge bosons in this model. Finally, we discuss the lightest mirror neutrino decay mechanism, which will be highly abundant if stable.

Higgs production in association with a dark-Z at future electron positron colliders

In recent years there have been many proposals for new electron-positron colliders, such as the Circular Electron-Positron Collider, the International Linear Collider, and the Future Circular Collider in electron-positron mode. Much of the motivation for these colliders is precision measurements of the Higgs boson and searches for new electroweak states. Hence, many of these studies are focused on energies above the h Z threshold. However, there are proposals to run these colliders at the lower WW threshold and Z-pole energies. In this paper, we study a new search for Higgs physics accessible at lower energies: e+e− → h Zd, where Zdis a new light gauge boson such as a dark photon or dark-Z. Such searches can be conducted at the WW threshold, i.e. energies below the h Z threshold where exotic Higgs decays can be searched for in earnest. Additionally, due to very good angular and energy resolution at future electron-positron colliders, these searches will be sensitive to Zd masses below 1 GeV, which is lower than the current direct LHC searches. We will show that at √s = 160 GeV with 10 ab−1, a search for e+e− → h Zd is sensitive to h −Z −Zd couplings of δ ∼ 9 × 10−3and cross sections of ∼ 2 − 3 ab for Zd masses below 1 GeV. The results are similar at √s = 240 GeV with 5 ab−1.

Next-to-leading-order corrections to the Higgs strahlung process from electron–positron collisions in extended Higgs models

We present the cross section for $$e^{+}e^{-}\rightarrow hZ$$ e + e - → h Z with arbitrary sets of electron and Z boson polarizations at the full next-to-leading order in various extended Higgs models, such as the Higgs singlet model (HSM), the inert doublet model (IDM) and the two Higgs doublet model (2HDM). We systematically perform complete one-loop calculations to the helicity amplitudes in the on-shell renormalization scheme, and present the full analytic results as well as numerical evaluations. The deviation $$\Delta R^{hZ}$$ Δ R hZ in the total cross section from its standard model (SM) prediction is comprehensively analyzed, and the differences among these models are discussed in details. We find that new physics effects appearing in the renormalized hZZ vertex almost govern the behavior of $$\Delta R^{hZ}$$ Δ R hZ , and it takes a negative value in most cases. The possible size of $$\Delta R^{hZ}$$ Δ R hZ reaches several percent under the theoretical and experimental bounds. We also analyze the deviation $$\Delta R^{hZ}_{XY}$$ Δ R XY hZ in the total cross section times decay branching ratios of the discovered Higgs boson by utilizing the program. It is found that the four types of 2HDMs can be discriminated by analyzing the correlation between $$\Delta R^{hZ}_{\tau \tau }$$ Δ R τ τ hZ and $$\Delta R^{hZ}_{bb}$$ Δ R bb hZ and those between $$\Delta R^{hZ}_{\tau \tau }$$ Δ R τ τ hZ and $$\Delta R^{hZ}_{cc}$$ Δ R cc hZ . Furthermore, the HSM and the IDM can be discriminated from the 2HDMs by measuring $$\Delta R^{hZ}_{WW}$$ Δ R WW hZ . These signatures can be tested by precision measurements at future Higgs factories such as the International Linear Collider.

Sensitivity of future linear $$\hbox {e}^+\hbox {e}^-$$ colliders to processes of dark matter production with light mediator exchange

As any $$e^+e^-$$ e + e - scattering process can be accompanied by a hard photon emission from the initial state radiation, the analysis of the energy spectrum and angular distributions of those photons can be used to search for hard processes with an invisible final state. Thus high energy $$e^+e^-$$ e + e - colliders offer a unique possibility for the most general search of dark matter (DM) based on the mono-photon signature. We consider production of DM particles at the International Linear Collider (ILC) and Compact Linear Collider (CLIC) experiments via a light mediator exchange. Detector effects are taken into account within the Delphes fast simulation framework. Limits on the light DM production in a simplified model are set as a function of the mediator mass and width based on the expected two-dimensional distributions of the reconstructed mono-photon events. The experimental sensitivity is extracted in terms of the DM production cross section. Limits on the mediator couplings are then presented for a wide range of mediator masses and widths. For light mediators, for masses up to the centre-of-mass energy of the collider, coupling limits derived from the mono-photon analysis are more stringent than those expected from direct resonance searches in decay channels to SM particles.

Mechanism of Spontaneous Surface Modifications on Polycrystalline Cu Due to Electric Fields

We present a credible mechanism of spontaneous field emitter formation in high electric field applications, such as Compact Linear Collider in CERN (The European Organization for Nuclear Research). Discovery of such phenomena opens new pathway to tame the highly destructive and performance limiting vacuum breakdown phenomena. Vacuum breakdowns in particle accelerators and other devices operating at high electric fields is a common problem in the operation of these devices. It has been proposed that the onset of vacuum breakdowns is associated with appearance of surface protrusions while the device is in operation under high electric field. Moreover, the breakdown tolerance of an electrode material was correlated with the type of lattice structure of the material. Although biased diffusion under field has been shown to cause growth of significantly field-enhancing tips starting from initial nm-size protrusions, the mechanisms and the dynamics of the growth of the latter have not been studied yet. In the current paper we conduct molecular dynamics simulations of nanocrystalline copper surfaces and show the possibility of protrusion growth under the stress exerted on the surface by an applied electrostatic field. We show the importance of grain boundaries on the protrusion formation and establish a linear relationship between the necessary electrostatic stress for protrusion formation and the temperature of the system. Finally, we show that the time for protrusion formation decreases with the applied electrostatic stress, we give the Arrhenius extrapolation to the case of lower fields, and we present a general discussion of the protrusion formation mechanisms in the case of polycrystalline copper surfaces.

Search for single production of vector-like B quark decaying to bZ at future linear colliders

New vector-like quarks are predicted in many new physics scenarios beyond the Standard Model (SM). Based on a model-independent framework, we investigate the prospect of discovering the SU(2) singlet vector-like bottom quark (VLQ-B) in $$e^{+}e^{-}$$ e + e - collisions at 3 TeV Compact Linear Collider. We study the single VLQ-B production process $$e^{-}e^{+}\rightarrow B{\bar{b}}\rightarrow Zb{\bar{b}}$$ e - e + → B b ¯ → Z b b ¯ with two types of decay channel: $$Z\rightarrow \ell ^{+}\ell ^{-}$$ Z → ℓ + ℓ - , and $$Z\rightarrow \nu {\bar{\nu }}$$ Z → ν ν ¯ . By carrying out a full simulation for the signals and the relevant SM backgrounds, the $$2\sigma $$ 2 σ exclusion limit and $$5\sigma $$ 5 σ discovery prospects are, respectively, obtained on the B quark mass and the coupling strength $$g^{*}$$ g ∗ with the integrated luminosity of 5 $$\hbox {ab}^{-1}$$ ab - 1 . Our numerical results show that the possible signals of the singlet VLQ-B might be detected at the future high-energy $$e^{+}e^{-}$$ e + e - linear colliders.