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.
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 $lambda_gamma ge 0$.
The recent discovery of a Higgs boson at LHC, while establishing the Higgs mechanism as the way of electroweak symmetry breaking, started an era of precision measurements involving the Higgs boson. In an effective Lagrangian framework, we consider th
e e+e- --> ZHH process, at an ILC running at a centre of mass energy of 800 GeV to investigate the effect of the ZZH and ZZHH couplings on the sensitivity of HHH coupling on this process. Our results show that the sensitivity of the trilinear Higgs self couplings on this process has somewhat strong dependence on the Higgs-gauge boson couplings. Single and two parameter reach of ILC with integrated luminosity of 1000 /fb are obtained on the effective couplings, c6 and cH, which are related to the HHH couplings, indicating how these limits are affected by the presence of anomalous ZZH and ZZHH couplings. The kinematic distributions studied to understand the effect of the anomalous couplings, again, show strong influence of Z-H couplings on the dependence of these distributions on HHH coupling. Similar results are indicated in the case of the process, e+e- --> nu nu HH, considered at a centre of mass energy of 2 TeV, where the cross section is large enough. The effect of WWH and WWHH couplings on the sensitivity of HHH coupling is clearely established through our analyses of this process.
We study the effect of explicit CP violation in the Higgs sectors of the MSSM in the di-photon decay of the lightest CP-mixed Higgs state. Further it is shown that the gluon fusion production mechanism along with the di-photon decay enhances CP-viola
ting effects for a large set of suitably chosen parameter values.
We investigate the effect of anomalous gamma-W-W couplings in e-gamma --> nu W through the angular and energy spectrum of the secondary leptons. Within the narrow-width approximation, a semi-analytical study of the secondary lepton energy-angle doubl
e distribution is considered. Utility of observables derived from this is demonstrated by considering the anomalous coupling, delta-kappa-gamma. Results of our investigation for typical ILC machine considered at Ecm = 300-1000 GeV re-affirms potential of this collider as a precision machine.
We prove the strong sensitivity of the gg --> H1 --> gamma.gamma cross section at the Large Hadron Collider on the explicitly CP-violating phases of the Minimal Supersymmetric Standard Model, where H1 is the lightest Supersymmetric Higgs boson.
Physical Higgs particles in the Minimal Supersymmetric Standard Model (MSSM) with explicit CP violation are CP mixed states. The decay of these Higgs particles can be analysed to study the CP properties of the MSSM. In the present work we consider th
e di-photon channel of the lightest neutral Higgs boson for this purpose. Compared to earlier studies on effects of scalar/pseudo-scalar mixing, our analysis also investigates the effect due to Higgs-sfermion-sfermion couplings along with that of mixing. We find that a light stop may have a strong impact on the width and Branching Ratio (BR) of the decay process H1 --> gamma.gamma, whereas other light sparticles have only little influence. In some regions of the MSSM parameter space with large CP-violating phase phi-mu ~ 90 deg a light (~ 200 GeV) stop can change the di-photon BR by more than 50 % compared to the case with heavy (~ 1 TeV) stop and otherwise same MSSM parameters.
The di-photon decay channel of the lightest Higgs boson is considerd as a probe to explore CP violation in the Minimal Supersymmetric Standard Model (MSSM). The scalar/pseudo-scalar mixing is considered along with CP violation entering through the Hi
ggs-sfermion-sfermion couplings, with and without light sparticles. The impact of a light stop on the decay width and Branching Ratio (BR) is established through a detailed study of the amplitude of the process H1 --> gamma.gamma. The other sparticles have little influence even when they are light. With a suitable combination of other MSSM parameters, a light stop can change the BR by more than 50 % with a CP-violating phase phi_mu ~ 90 deg., while the change is almost nil with a heavy stop.
