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Register a new userProbing $WWgamma$ coupling through $e^- gamma rightarrow u_e W^-$ at ILC
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The anomalous $WWgamma$ coupling is probed through $egammarightarrow u W$ at the ILC. With a spectacular single lepton final state, this process is well suited to study the above coupling. Cross section measurements can probe $delta kappa_gamma$ to about $pm 0.004$ for a luminosity of 100 fb$^{-1}$ at $500$ GeV center-of-mass energy with unpolarized electron beam. The limits derivable on $lambda_gamma$ from the total cross section are comparatively more relaxed. Exploiting the energy-angle double distribution of the secondary muons, kinematic regions sensitive to these couplings are identified. The derivable limit on $lambda_gamma < 0$ could be improved to a few per-mil, focusing on such regions. More importantly, the angular distributions at fixed energy values, and energy distribution at fixed angles present very interesting possibility of distinguishing the case of $lambda_gamma <0$ and $lambda_gamma ge 0$.
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In this work, Higgs couplings with gauge bosons is probed through $e^-e^+ rightarrow W^-W^+H$ in an effective Lagrangian framework. An ILC of 500 $GeV$ center of mass energy with possible beam polarization is considered for this purpose. The reach of ILC with integrated luminosity of 300 $fb^{-1}$ in the determination of both the CP-conserving and CP-violating parameters are obtained. Sensitivity of the probe of each of these couplings on the presence of other couplings is investigated. The most influential couplings parameters are $bar c_W=-bar c_B$. Other parameters of significant effect are $bar c_{HW}$ and $bar c_{HB}$ among the CP-conserving ones, and $tilde c_{HW}$ and $tilde c_{HB}$ among the CP-violating ones. CP-violating parameter, $tilde c_gamma$ seems to have very little influence on the process considered. Detailed study of the angular distributions have presented a way to disentangle the effect of some of these couplings.
A search for the rare radiative leptonic decay $D_s^+togamma e^+ u_e$ is performed for the first time using electron-positron collision data corresponding to an integrated luminosity of 3.19 fb$^{-1}$, collected with the BESIII detector at a center-of-mass energy of 4.178 GeV. No evidence for the $D_s^+togamma e^+ u_e$ decay is seen and an upper limit of $mathcal B(D_s^+togamma e^+ u_e)<1.3times 10^{-4}$ is set on the partial branching fraction at a 90% confidence level for radiative photon energies $E_{gamma}^*>0.01$~GeV.
New heavy neutral gauge bosons Z are predicted by many models of physics beyond the Standard Model. It is quite possible that Zs are heavy enough to lie beyond the discovery reach of the CERN Large Hadron Collider LHC, in which case only indirect signatures of Z exchanges may emerge at future colliders, through deviations of the measured cross sections from the Standard Model predictions. We discuss in this context the foreseeable sensitivity to Zs of W^pm-pair production cross sections at the e^+e^- International Linear Collider (ILC), especially as regards the potential of distinguishing observable effects of the Z from analogous ones due to competitor models with anomalous trilinear gauge couplings (AGC) that can lead to the same or similar new physics experimental signatures at the ILC. The sensitivity of the ILC for probing the Z-Z mixing and its capability to distinguish these two new physics scenarios is substantially enhanced when the polarization of the initial beams and the produced W^pm bosons are considered. A model independent analysis of the Z effects in the process e^+e^- to W^+W^- allows to differentiate the full class of vector Z models from those with anomalous trilinear gauge couplings, with one notable exception: the sequential SM (SSM)-like models can in this process not be distinguished from anomalous gauge couplings. Results of model dependent analysis of a specific Z are expressed in terms of discovery and identification reaches on the Z-Z mixing angle and the Z mass.
By using the GRACE-Loop system, we calculate the full $mathcal{O}(alpha)$ electroweak radiative corrections to the process $e^+e^- rightarrow e^+e^- gamma$, which is important for future investigations at the International Linear Collider (ILC). With the GRACE-Loop system, the calculations are checked numerically by three consistency tests: ultraviolet finiteness, infrared finiteness, and gauge-parameter independence. The results show good numerical stability when quadruple precision is used. In the phenomenological results, we find that the electroweak corrections to the total cross section range from $sim -4%$ to $sim -21%$ when $sqrt{s}$ varies from $250$ GeV to $1$ TeV. The corrections also significantly affect the differential cross sections, which are a function of the invariant masses and angles and the final-particle energies. Such corrections will play an important role for the high-precision program at the ILC.
We evaluate the $e^- e^+ to e^- e^+ +h$ process through the $ZZ$ fusion channel at the International Linear Collider (ILC) operating at $500$ GeV and $1$ TeV center of mass energies. We perform realistic simulations on the signal process and background processes. With judicious kinematic cuts, we find that the inclusive cross section can be measured to $2.9%$ after combining the $500$ GeV at $500 text{fb}^{-1}$ and $1$ TeV at $1~ text{ab}^{-1}$ runs. A multivariate log-likelihood analysis further improves the precision of the cross section measurement to $2.3%$. We discuss the overall improvement to model-independent Higgs width and coupling determinations and demonstrate the use of different channels in distinguishing new physics effects in Higgs physics. Our study demonstrates the importance of the $ZZ$ fusion channel to Higgs precision physics, which has often been neglected in the literature.
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