We investigate in detail the charged Higgs production associated with a $W$ boson at electron-positron colliders within the framework of the Type-I two-Higgs-doublet model (THDM). We calculate the integrated cross section at the LO and analyze the dependence of the cross section on the THDM parameters and the colliding energy in a benchmark scenario of the input parameters of Higgs sector. The numerical results show that the integrated cross section is sensitive to the charged Higgs mass, especially in the vicinity of $m_{H^{\pm}} \simeq 184~ {\rm GeV}$ at a $500~ {\rm GeV}$ $e^+e^-$ collider, and decreases consistently as the increment of $\tanβ$ in the low $\tanβ$ region. The peak in the colliding energy distribution of the cross section arises from the resonance of loop integrals and its position moves towards low colliding energy as the increment of $m_{H^{\pm}}$. We also study the two-loop NLO QCD corrections to both the integrated cross section and the angular distribution of the charged Higgs boson, and find that the QCD relative correction is also sensitive to the charged Higgs mass and strongly depends on the final-state phase space. For $\tanβ= 2$, the QCD relative correction at a $500~ {\rm GeV}$ $e^+e^-$ collider varies in the range of $[-10\%,\, 11\%]$ as $m_{H^{\pm}}$ increases from $150$ to $400~ {\rm GeV}$.
We study the decay $t\rightarrow cγ$ with flavor-changing neutral interactions in scalar sector of the type III Two Higgs Doublet Model (THDM-III) with mixing between neutral scalar fields as a result of considering the most general scalar potential. The branching ratio of the decay $Br(t\rightarrow cγ)$ is calculated as function of the mixing parameters and masses of the neutral scalar fields. We obtain a $Br(t\rightarrow cγ)$ of the order of $10^{-8}$ for the considered regions of the mixing parameters. Finally, one upper bound for the possible events is estimated to be $n=18$ by assuming a …
In this paper, we have theoretically studied the neutral Higgs pair production in Two Higgs Doublet Model (THDM) in the presence of a circularly polarized laser field. The laser-assisted differential partial cross section is derived in the centre of mass frame at the leading order including $Z$ diagram. The total cross section is computed numerically by integrating the differential cross section over the solid angle $dΩ$. Two benchmark points are discussed for the THDM parameters. In the first step, we have analyzed the total cross section of ${e}^{+}{e}^{-}\rightarrow h^{0}A^{0}$ by consideri…
We present results of a calculation of the cross section for the production of a charged Higgs boson in association with an electron and a neutrino at electron-positron colliders (e+ e- -> H+ e- nu_e-bar, H- e+ nu_e). We study predictions for the cross section in the Minimal Supersymmetric Standard Model (MSSM) and the Two Higgs Doublet Model (THDM), highlighting possible differences. The process is effectively loop-induced in both models. Hence, the cross section is expected to be strongly model-dependent. Most notably, due to the presence of superpartners, the MSSM amplitude contains Feynman…
We discuss the formalism of two Higgs doublet model type III with CP violation from CP-even CP-odd mixing in the neutral Higgs bosons. The flavor changing interactions among neutral Higgs bosons and fermions are presented at tree level in this type of model. These assumptions allow the study rare top decays mediated by neutral Higgs bosons, particularly we are interested in $t\rightarrow c l^+l^-$. For this process we estimated upper bounds of the branching ratios $\textrm{Br}(t\rightarrow c τ^+τ^-)$ of the order of $10^{-9}\sim 10^{-7}$ for a neutral Higgs boson mass of 125 GeV and $\tanβ=1$,…
In this paper, we combine the $ν$-Two-Higgs-Doublet-Model ($ν$THDM) with the inverse seesaw mechanisms. In this model, the Yukawa couplings involving the sterile neutrinos and the exotic Higgs bosons can be of order one in the case of a large $\tan β$. We calculated the corrections to the Z-resonance parameters $R_{l_i}$, $A_{l_i}$, $N_ν$, together with the $l_1 \rightarrow l_2 γ$ branching ratios, and the muon anomalous $g-2$. Compared with the current bounds and plans for the future colliders, we find that the corrections to the electroweak parameters can be contrained or discovered in much …
In this study, the charged Higgs pair production is analyzed for the minimal extension of the standard model called two-higgs-doublet model. The process $γγ\rightarrow H^+H^-$ is calculated at the tree level for the ILC and the numerical analysis is presented for various parameters. The production rate of the charged Higgs boson pair as a function of center-of-mass (CM) energy and the differential cross section as a function of angle between photon and positive charged Higgs boson is presented. The cross section gets high at the low charged Higgs mass and low CM energies. The total integrated …
We study associated Higgs production with a photon at electron-positron colliders, $e^+e^-\to hγ$, in various extended Higgs models, such as the inert doublet model (IDM), the inert triplet model (ITM) and the two Higgs doublet model (THDM). The cross section in the standard model (SM) is maximal around $\sqrt{s}=$250 GeV, and we present how and how much the new physics can enhance or reduce the production rate. We also discuss the correlation with the $h\toγγ$ and $h\to Zγ$ decay rates. We find that, with a sizable coupling to a SM-like Higgs boson, charged scalars can give considerable contr…
We present a calculation of the cross section for the process e+ e- --> W+/- H-/+ in the minimal supersymmetric standard model (MSSM) and the Two Higgs Doublet Model (THDM). We study the basic features of the MSSM prediction for some distinctive parameter scenarios. We find large effects from virtual squarks for scenarios with large mixing in the stop sector which can lead to a cross section vastly different from a THDM with identical Higgs sector parameters. We investigate this interesting behaviour in more detail by thoroughly scanning the MSSM parameter space for regions of large cross sect…
In the framework of the 3-3-1 model with neutral leptons, we have investigated the lepton-flavor-violating sources based on the Higgs mass spectrum which has two neutral Higgses identitied with corresponding ones in the Two-Higgs-Doublet model (THDM). On the $13~\mathrm{TeV}$ scale of the LHC, we point out the parameter space regions where the experimental limits of $e_i \rightarrow e_jγ$ decays are satisfied. These regions depend heavily on the mixing of exotic leptons but are predicted to have large $h^0_1\rightarrow μτ$ signals. We also show that $\mathrm{Br}(h^0_1\rightarrow μτ)$ can reach…
It is shown that $BR(χ_{b1}(1P)\rightarrow Z\rightarrow e^+e^-)\simeq 3.3\cdot 10^{-7}$, $BR(χ_{b1}(2P)\rightarrow Z\rightarrow e^+e^-)\simeq 4.1\cdot 10^{-7}$ and $BR(χ_{c1}(1P)\rightarrow Z\rightarrow e^+e^-)\simeq 10^{-8}$ that give a good chance to search for the direct production of pseudovector $^3P_1$ heavy quarkonia in $e^+e^-$ collisions ($e^+e^-\rightarrow Z\rightarrow ^3P_1$) even at current facilities not to mention $b$ and $c-τ$ factories. Leading radiative corrections to annihilation of quarkonia in QCD are discussed.
Phenomenological Study of $Ω_c\rightarrow Ω^-π^+$ at Polarized Electron-Positron Collider
Key Laboratory of Nuclear Physics and Ion-beam Application (MOE) and Institute of Modern Physics, Fudan University（核物理与离子束应用教育部重点实验室和现代物理研究所，复旦大学）；College of Physics, Jilin University（吉林大学物理学院）；Institute of High Energy Physics（高能物理研究所）
Production of $ρ(770)$, $η$ pairs at colliding of electron-positron beams and in the decays $ρ(1450)\rightarrow ρ(770)η$, $τ\rightarrow ρ(770)ην_τ$ is calculated in the framework of the Nambu - Jona-Lasinio model. In the process of electron-positron annihilation and the $τ$ - lepton decay the contributions of the intermediate $ρ(770)$ vector meson in the ground and first radially excited state are taken into account. The theoretical prediction for the decay $τ\rightarrow ρ(770)ην_τ$ is given. The obtained results for other processes are in satisfactory agreement with the experimental data.
There is no guarantee that the violation of lepton number, assuming it exists, will primarily manifest itself in neutrinoless double beta decay ($0νββ$). Lepton-number violation and lepton-flavor violation may be related, and much-needed information regarding the physics that violates lepton number can be learned by exploring observables that violate lepton flavors other than electron flavor. One of the most promising observables is $μ^- \rightarrow e^+$ conversion, which can be explored by experiments that are specifically designed to search for $μ^- \rightarrow e^-$ conversion. We survey lep…
One kind of particularly interesting pseudoscalar particles, called axion-like particles (ALPs), have rich physical phenomenology at high- and low-energy collider experiments. After discussing most of single production channels of ALP at electron-positron colliders, we investigate the possibility of detecting this kind of new particles through the W$^{+}$W$^{-}$ fusion process e$^{+}$e$^{-}$ $\rightarrow$ $\overlineν_{e}$$ν_{e}a$ $(\rightarrow γγ)$ at the CLIC. The 3$σ$ and 5$σ$ bounds on the ALP parameter space at the three energy stages of the CLIC are obtained. We find that the bounds given…
Very recently, the Fermi-Lab reported the new experimental combined results on the magnetic momentum of muon with a 4.2$σ$ discrepancy compared with the expectation of the Standard Model \cite{Fermi_Lab}. A new light gauge boson $X$ in the $L_μ-L_τ$ model provides a good explanation for the $g-2$ anomaly. A Dirac fermion dark matter with a large $L_μ-L_τ$ charge can explain both the $g-2$ anomaly and the dark matter relic density \cite{Asai_2021}. In this work, we focus on the case that the mass of the dark matter is larger than the mass of muon (i.e. $m_Ψ > m_μ$) for which the channel $ΨΨ\rig…
The Glashow resonance is a rapid enhancement of the cross section for scattering of electron antineutrinos on electrons at the $W^-$ boson production threshold due to the $s$-channel contribution. This resonance is being searched for at large volume neutrino detectors in which the reaction $\barν_ee^-\rightarrow W^-$ to be initiated by cosmic ray antineutrinos of energies about 6.3 PeV. The relatively small neutrino flux reaching the Earth together with the necessity of analyzing ultra-high-energy final states make such searches challenging. We argue here that the Glashow resonance may contrib…
Because the production cross sections of gamma-rays, electrons, and positrons made in p-p collisions, $σ_{pp\rightarrow γ}$ and $σ_{pp\rightarrow {e}^\pm}$, respectively, are kinematically equivalent with respect to the parent pion-production cross section $σ_{pp\rightarrow π}$, we obtain $σ_{pp\rightarrow {e}^\pm}$ directly from the machine data on $σ_{pp\rightarrow γ}$. In Sato et al. (2012), we give explicitly $σ_{pp\rightarrow γ}$, reproducing quite well the accelerator data with LHC, namely $σ_{pp\rightarrow {e}^\pm}$ is applicable enough over the wide energy range from GeV to 20\,PeV for…
A complete one-loop prediction for the single production of the neutral Higgs bosons in association with a photon in electron-positron collisions is presented in the framework the minimal supersymmetric standard model (MSSM), paying special attention to the individual contribution from each type of diagram. This process has no amplitude at tree level and is hence directly sensitive to one-loop impacts and the underlying dynamics of Higgs. To investigate the effect of the new physics, four different scenarios, which include a Higgs boson with mass and couplings consistent with those of the disc…
We study Higgs diphoton decays, in which both photons undergo nuclear conversion to electron- positron pairs. The kinematic distribution of the two electron-positron pairs may be used to probe the CP violating (CPV) coupling of the Higgs to photons, that may be produced by new physics. Detecting CPV in this manner requires interference between the spin-polarized helicity amplitudes for both conversions. We derive leading order, analytic forms for these amplitudes. In turn, we obtain compact, leading-order expressions for the full process rate. While performing experiments involving photon conv…
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 propose a new search for Higgs physics ac…
In this paper, the production of the charged Higgs pair associated with the $Z^0$ boson is analyzed in the minimal extension of the standard model the so-called two-Higgs-doublet model (2HDM). The process $e^+e^- \rightarrow H^+H^-Z^0$ is calculated at the tree level including all the possible diagrams in 2HDM. The numerical analysis is performed in consideration of the current experimental constraints and various scenarios for the free parameters of the model. The results are presented as a function of center-of-mass energy, the charged Higgs mass ($m_{H^\pm}$), and the ratio of the vacuum ex…
Lepton flavor violating interactions are absent in the standard model but are expected in various beyond standard models. In this work, the potential of the future circular electron-positron collider to probe the four fermion lepton flavor couplings via the $e^{+}e^{-}\rightarrow e^{\pm}τ^{\mp}$ process is revisited by means of an effective field theory approach. We provide constraints at $95\%$ CL on the dimension-six Wilson coefficients including major sources of background processes and considering realistic detector effects at four expected operation energies $\sqrt{s}=157.5$, $162.5$, $24…
The Circular Electron Positron Collider (CEPC) is a future Higgs factory proposed by the Chinese high energy physics community. It will operate at a center-of-mass energy of 240-250 GeV. The CEPC will accumulate an integrated luminosity of 5 ab$^{\rm{-1}}$ in ten years' operation. With GEANT4-based full simulation samples for CEPC, Higgs boson decaying into electron pair is studied at the CEPC. The upper limit of ${\cal B}(H \rightarrow e^+ e^-)$ could reach 0.024\% at 95\% confidence level. The signal process is generated by MadGraph, with Initial State Radiation (ISR) implemented, as a first…
Dark sector may couple to the Standard Model via one or more mediator particles. We discuss two types of mediators: the dark photon $A^{\prime}$ and the dark scalar mediator $ϕ$. The total cross-sections and various differential distributions of the processes $e^{+} e^{-} \rightarrow q \bar{q} A^{\prime}$ and $e^{+} e^{-} \rightarrow q \bar{q} ϕ$ ($q=u,~d,~c,~s$ and $b$ quarks) are discussed. We focus on the study of the invisible $A^{\prime}$ due to the cleaner background at future $e^{+} e^{-}$ colliders. It is found that the kinematic distributions of the two-jet system could be used to ide…
Beyond the Standard Model Higgs physics: Hunting $h \rightarrow bs$ with Higgs-strahlung at CEPC and FCC-ee
Benemérita Universidad Autónoma de Puebla（普埃布拉自治大学）；Centro Interdisciplinario de Investigación y Enseñanza de la Ciencia (CIIEC)（科学交叉研究与教育中心）；Universidad Nacional Autónoma de México（墨西哥国立自治大学）
One of the most challenging tasks for future high-luminosity electron-positron colliders is to extract Higgs triple coupling. It was proposed that this can be carried out via the precisely measuring the cross section of ZH associated production up to $0.4\%$. In this paper, we example the possible heavy pollution from Higgs-top anomalous coupling. Our numerical results show that the pollution is small for $\sqrt{s}_{e^+e^-}= 240 GeV$. However for the higher energy collider, pollution is sizable, which should be taken into account. We further explored the possibility to measure CP-violated Higg…
In view of the recent interest in the decays of mesons into a pair of light leptons, a computation of the QED radiative corrections to the decay of $π^{0}$ into an electron-positron pair is presented here. The results indicate that the peak value of the differential decay rate is reduced by about $50 \%$, because of soft-photon radiation. The number of $e^{+}e^{-}$ pairs having invariant masses in an energy bin of 0.5 MeV centered around $m_π$ is found to be about $20 \%$ smaller than the one it would be if radiative corrections were neglected.
Based on the NRQCD factorization formalism, we calculate the next-to-next-to-leading order QCD corrections to the heavy quarkonium $η_c (η_b)$ production associated with a photon at electron-positron colliders. By matching the amplitudes calculated in full QCD theory to a series of operators in NRQCD, the short-distance coefficients up to NNLO QCD radiative corrections are determined. It turns out that the full set of master integrals that we obtained could be analytically expressed in terms of Goncharov Polylogarithms, Chen's iterated integrals, and elliptic functions, which mostly do not exi…
We present a study to examine the sensitivity of a future $e^{-} e^{+}$ collider to the anomalous top flavour-changing neutral current (FCNC) to the gluon. To separate signal from background a multivariate analysis is performed on top-quark pair and background events, where one top quark is considered to follow the dominant Standard Model (SM) decay, $t \rightarrow Wb$, and the other top decays through FCNC, $t\rightarrow qg$, where $q$ is a $u-$ or a $c-$quark. The analysis of fully-hadronic FCNC decay of the $t \bar{t}$ pair is also presented. The $95\%$ confidence level limits on the top-qu…
The data collected by ATIC, CREAM and PAMELA all display remarkable cosmic-ray-nuclei spectrum hardening above the magnetic rigidity $\sim$ 240 GV. One natural speculation is that the primary electron spectrum also gets hardened (possibly at $\sim 80$ GV) and the hardening partly accounts for the electron/positron total spectrum excess discovered by ATIC, HESS and Fermi-LAT. If it is the case, the increasing behavior of the subsequent positron-to-electron ratio will get flattened and the spectrum hardening should be taken into account in the joint fit of the electron/psoitron data otherwise th…
In present work we study the production of ground and excited charmonium pairs in $e^- e^+ \rightarrow Ψ(nS)+ χ_{cJ}(nP)$ for $J=0,1$ and $n=1,2$, through leading order (LO) tree-level diagrams $\sim O(α_{em} α_s)$, which proceed through exchange of a virtual photon and an internal gluon line connecting two quark lines (in the triangle quark loop part of the diagram), in the framework of $4\times 4$ Bethe-Salpeter equation, at center of mass energy, $\sqrt{s}=10.6 GeV.$ We have tried to show that the cross sections for this process calculated with use of the four leading order $\sim O(α_{em} α…
We studied the dimension-6 leptonic anomalous gauge couplings in the formulation of linearly realized gauge symmetry effective Lagrangian and investigated the constraints on these anomalous couplings from the existed experimental data including LEP2 and $W$/$Z$ boson decay. Some bounds of $O(0.1-10){\rm TeV}^{-2}$ on four relevant anomalous couplings are given by the Z factories. We studied the sensitivity of testing the leptonic anomalous couplings via the process $e^+e^-\rightarrow W^+W^-$ at future $e^+e^-$ linear colliders. We discussed different sensitivities to anomalous couplings at pol…
The Elementary Goldstone Higgs (EGH) model is a perturbative extension of the standard model (SM), which identifies the EGH boson as the observed Higgs boson. In this paper, we study pair production of the EGH boson in future linear electron positron colliders. The cross sections in the TeV region can be changed to about $-27\%$, $163\%$ and $-34\%$ for the $e^+e^-\rightarrow Zhh$, $e^+e^-\rightarrow ν\barνhh$, and $e^+e^-\rightarrow t\bar{t}hh$ processes with respect to the SM predictions, respectively. According to the expected measurement precisions, such correction effects might be observe…
The effect of single top production on the study of top quark pair production in future high energy electron--positron colliders is evaluated. The rate of the single top quark production process is sizeable throughout a large range of center-of-mass energies and cannot easily be distinguished from the dominant pair production process. We discuss the impact on the top quark mass extraction from a scan through the pair production threshold and the determination of top quark form factors in the continuum. These results advocate for the exploration of the inclusive $e^+e^-\rightarrow W^+bW^-\bar{b…
Neutral gauge bosons beyond the Standard Model are becoming interesting as possible mediators to explain several experimental anomalies. They have small masses, below one GeV, and are referred to as dark photons, $U$, $A'$ or $Z'$ bosons. Electron--positron collision experiments at the B-factories provide the most straightforward way to probe bosons of this kind. In the present article we study production of the bosons at $e^+e^-$ colliders operating at GeV center-of-mass energies. We have studied two channels: $e^+e^-\rightarrow γZ'$ and $e^+e^-\rightarrow e^+e^-Z'$. Analytic expressions for …
We review in some detail the QCD corrections to the measurement of the forward-backward charge asymmetry of heavy quarks in the $\mathrm{e^+e^-\rightarrow Q\overline{Q}(g)}$ process at the Z pole. We show that the size of these corrections can be reduced by an order of magnitude by using simple cuts on jet acollinearity. Such a reduction is expected to lead to systematic uncertainties at the $Δ\mathrm{A_{FB}^{0,Q}} \approx 10^{-4}$ level, opening up the path to high precision electroweak measurements with heavy flavors at future high luminosity $\mathrm{e^+e^-}$ colliders like the FCC-ee.
We analyze the capability of the next generation of linear electron--positron colliders to unravel the spin and couplings of excited leptons predicted by composite models. Assuming that these machines will be able to operate both in the $e^+e^-$ and $e^-γ$ modes, we study the effects of the excited electrons of spin $\frac{1}{2}$ and $\frac{3}{2}$ in the reactions $e^-γ\rightarrow e^-γ$ and $e^+e^- \rightarrow γγ$. We show how the use of polarized beams is able not only to increase the reach of these machines, but also to determine the spin and couplings of the excited states.
($γ$, $χ_{cJ}(J=0,1)$) and ($γ$, $η_c$) production in electron-positron annihilation at $\sqrt{s}=10.6$ GeV and $4.6$ GeV in the framework of Bethe-Salpeter equation
In this paper, we have investigated the elementary particle reaction ${e}^{+} {e}^{-} \rightarrowμ^{+} μ^{-}$ that results from the electron-positron interaction, at the leading order, with an intense laser wave of circular polarization. We have derived, by annalytical means, the laser-assisted differential cross section expression by using the scattering matrix approach. We have analyzed the energy and the number of exchanged photons dependence of muon pair production in electron-positron annihilation at different centre of mass energies including the $Z$-boson peak. For this reason, a wide r…
The addition of a high intensity 11 GeV polarized positron beam at the Continuous Electron Beam Accelerator Facility (CEBAF) at JLAB would allow for a search of Charged Lepton Flavor Violation (CLFV) via the process $e^+N \rightarrow μ^+ X$. The proposed Solenoidal Large Intensity Detector (SoLID) spectrometer, in the configuration with muon chambers, would be ideal for such CLFV searches. Various new physics scenarios, including the phenomenologically convenient Leptoquark (LQ) framework, predict CLFV rates that are within reach of current or planned experiments. A positron beam with instanta…
A "Higgs factory", an electron-positron collider with center-of-mass energy of about 250 GeV, will measure the cross section of the Higgsstrahlung process, $e^+e^-\rightarrow hZ$, with sub-percent precision. This measurement is sensitive to a variety of new physics scenarios. In this paper, we study two examples. First, we compute corrections to the $e^+e^-\rightarrow hZ$ differential cross section in the effective field theory (EFT) approach, including the complete set of dimension-6 operators contributing to this process. These results are applicable to any model where the new physics mass s…
Full one-loop electroweak-corrections for an $e^-e^+\rightarrow t \bar{t}$ process associated with sequential $t\rightarrow b μν_μ$ decay are discussed. At the one-loop level, the spin-polarization effects of the initial electron and positron beams are included in the total and differential cross sections. A narrow-width approximation is used to treat the top-quark production and decay while including full spin correlations between them. We observed that the radiative corrections due to the weak interaction have a large polarization dependence on both the total and differential cross sections.…
In the Circular Electron Positron Collider (CEPC), a measurement of the Higgs CP mixing through $e^{+} e^{-} \rightarrow Z H \rightarrow l^{+} l^{-}(e^{+} e^{-} /μ^{+} μ^{-}) H(\rightarrow b \bar{b} / c \bar{c} / g g)$ process is presented, with $5.6\ \mbox{ab}^{-1}$ $e^{+} e^{-}$ collision data at the center-of-mass energy of $240\ \mathrm{GeV}$. In this study, the CP-violating parameter $\tilde{c}_{Z γ}$ is constrained between the region of $ -0.30$ and $0.27$ and $\tilde{c}_{Z Z}$ between $-0.06$ and $0.06$ at $68\%$ confidence level. This study demonstrates the great potential of probing H…
In our previous work [Phys. Rev. D 101 (2020) 075046], we have proposed to install FAr Detectors at the Electron Positron Collider (FADEPC) to enhance the discovery potential of long-lived particles (LLPs). In this study, we consider eight designs of far detectors with different locations, volumes and geometries and investigate their potential for discovering long-lived axion-like particles (ALPs) via the process $e^-e^+ \rightarrow γ\,\, a,~ a \to γγ$ at future $e^{-}e^{+}$ colliders running at a center-of-mass energy of 91.2 GeV and integrated luminosities of 16, 150, and 750 ab$^{-1}$. We e…
