Determination of $$\mathcal{C}\mathcal{P}$$ C P -violating HZZ interaction with polarised beams at the ILC
Abstract We study possible $${\mathcal{C}\mathcal{P}}$$ C P -violation effects of the 125 GeV Higgs to Z boson coupling at the 250 GeV ILC with transverse and longitudinal beam polarisation via the process $$e^+ e^- \rightarrow HZ \rightarrow H \mu ^-\mu ^+$$ e + e - → H Z → H μ - μ + . We explore t...
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2025-01-01
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| Series: | European Physical Journal C: Particles and Fields |
| Online Access: | https://doi.org/10.1140/epjc/s10052-025-13828-4 |
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| author | Cheng Li Gudrid Moortgat-Pick |
| author_facet | Cheng Li Gudrid Moortgat-Pick |
| author_sort | Cheng Li |
| collection | DOAJ |
| description | Abstract We study possible $${\mathcal{C}\mathcal{P}}$$ C P -violation effects of the 125 GeV Higgs to Z boson coupling at the 250 GeV ILC with transverse and longitudinal beam polarisation via the process $$e^+ e^- \rightarrow HZ \rightarrow H \mu ^-\mu ^+$$ e + e - → H Z → H μ - μ + . We explore the azimuthal angular distribution of the muon pair from the Z boson decay, and constructe $${\mathcal{C}\mathcal{P}}$$ C P -odd observables sensitive to $${\mathcal{C}\mathcal{P}}$$ C P -violation effects, where we derived this observable both by analytical calculations and by Whizard simulations. Particularly, we can construct two $${\mathcal{C}\mathcal{P}}$$ C P -odd observables with the help of transversely-polarised initial beams and improve the statistical significance of $${\mathcal{C}\mathcal{P}}$$ C P -violation effects by combining two measurements. We defined the asymmetries between the signal regions with different signs of the $${\mathcal{C}\mathcal{P}}$$ C P -odd observables, and determine the $${\mathcal{C}\mathcal{P}}$$ C P -violation effect by comparing with the SM 95% CL upper bound. In this paper, we setup a scenario which assumes that the total cross-section is always fixed while $${\mathcal{C}\mathcal{P}}$$ C P -violation is varying, and such a scenario helps us to determine the intrinsic $${\mathcal{C}\mathcal{P}}$$ C P -mixing angle limit around $$|\xi _{\mathcal{C}\mathcal{P}}|\sim 0.03~{\operatorname {rad}}$$ | ξ C P | ∼ 0.03 rad with (90%, 40%) polarised electron-positron beams and 5 $$\hbox {ab}^{-1}$$ ab - 1 integrated luminosity. In addition, we determine the $${\mathcal{C}\mathcal{P}}$$ C P -odd coupling limit $$|\widetilde{c}_{HZZ}|\sim 0.01$$ | c ~ HZZ | ∼ 0.01 as well, where we suppose that the SM tree-level cross-section is fixed and the $${\mathcal{C}\mathcal{P}}$$ C P -violation is the varying additional contribution. Comparing with the analysis with unpolarised beams, the sensitivity to the $${\mathcal{C}\mathcal{P}}$$ C P -violation effect can be improved by transverse or longitudinal polarisation. |
| format | Article |
| id | doaj-art-1fe56a7548d24dd89c978721b2c5e599 |
| institution | Kabale University |
| issn | 1434-6052 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | SpringerOpen |
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| series | European Physical Journal C: Particles and Fields |
| spelling | doaj-art-1fe56a7548d24dd89c978721b2c5e5992025-02-02T12:38:25ZengSpringerOpenEuropean Physical Journal C: Particles and Fields1434-60522025-01-0185112110.1140/epjc/s10052-025-13828-4Determination of $$\mathcal{C}\mathcal{P}$$ C P -violating HZZ interaction with polarised beams at the ILCCheng Li0Gudrid Moortgat-Pick1School of Science, Sun Yat-sen UniversityII. Institut für Theoretische Physik, Universität HamburgAbstract We study possible $${\mathcal{C}\mathcal{P}}$$ C P -violation effects of the 125 GeV Higgs to Z boson coupling at the 250 GeV ILC with transverse and longitudinal beam polarisation via the process $$e^+ e^- \rightarrow HZ \rightarrow H \mu ^-\mu ^+$$ e + e - → H Z → H μ - μ + . We explore the azimuthal angular distribution of the muon pair from the Z boson decay, and constructe $${\mathcal{C}\mathcal{P}}$$ C P -odd observables sensitive to $${\mathcal{C}\mathcal{P}}$$ C P -violation effects, where we derived this observable both by analytical calculations and by Whizard simulations. Particularly, we can construct two $${\mathcal{C}\mathcal{P}}$$ C P -odd observables with the help of transversely-polarised initial beams and improve the statistical significance of $${\mathcal{C}\mathcal{P}}$$ C P -violation effects by combining two measurements. We defined the asymmetries between the signal regions with different signs of the $${\mathcal{C}\mathcal{P}}$$ C P -odd observables, and determine the $${\mathcal{C}\mathcal{P}}$$ C P -violation effect by comparing with the SM 95% CL upper bound. In this paper, we setup a scenario which assumes that the total cross-section is always fixed while $${\mathcal{C}\mathcal{P}}$$ C P -violation is varying, and such a scenario helps us to determine the intrinsic $${\mathcal{C}\mathcal{P}}$$ C P -mixing angle limit around $$|\xi _{\mathcal{C}\mathcal{P}}|\sim 0.03~{\operatorname {rad}}$$ | ξ C P | ∼ 0.03 rad with (90%, 40%) polarised electron-positron beams and 5 $$\hbox {ab}^{-1}$$ ab - 1 integrated luminosity. In addition, we determine the $${\mathcal{C}\mathcal{P}}$$ C P -odd coupling limit $$|\widetilde{c}_{HZZ}|\sim 0.01$$ | c ~ HZZ | ∼ 0.01 as well, where we suppose that the SM tree-level cross-section is fixed and the $${\mathcal{C}\mathcal{P}}$$ C P -violation is the varying additional contribution. Comparing with the analysis with unpolarised beams, the sensitivity to the $${\mathcal{C}\mathcal{P}}$$ C P -violation effect can be improved by transverse or longitudinal polarisation.https://doi.org/10.1140/epjc/s10052-025-13828-4 |
| spellingShingle | Cheng Li Gudrid Moortgat-Pick Determination of $$\mathcal{C}\mathcal{P}$$ C P -violating HZZ interaction with polarised beams at the ILC European Physical Journal C: Particles and Fields |
| title | Determination of $$\mathcal{C}\mathcal{P}$$ C P -violating HZZ interaction with polarised beams at the ILC |
| title_full | Determination of $$\mathcal{C}\mathcal{P}$$ C P -violating HZZ interaction with polarised beams at the ILC |
| title_fullStr | Determination of $$\mathcal{C}\mathcal{P}$$ C P -violating HZZ interaction with polarised beams at the ILC |
| title_full_unstemmed | Determination of $$\mathcal{C}\mathcal{P}$$ C P -violating HZZ interaction with polarised beams at the ILC |
| title_short | Determination of $$\mathcal{C}\mathcal{P}$$ C P -violating HZZ interaction with polarised beams at the ILC |
| title_sort | determination of mathcal c mathcal p c p violating hzz interaction with polarised beams at the ilc |
| url | https://doi.org/10.1140/epjc/s10052-025-13828-4 |
| work_keys_str_mv | AT chengli determinationofmathcalcmathcalpcpviolatinghzzinteractionwithpolarisedbeamsattheilc AT gudridmoortgatpick determinationofmathcalcmathcalpcpviolatinghzzinteractionwithpolarisedbeamsattheilc |