LCFIPlus: A framework for jet analysis in linear collider studies

We study the potential of future lepton colliders to probe violation of the CP symmetry in the top quark sector. In certain extensions of the Standard Model, such as the two-Higgs-doublet model (2HDM), sizeable anomalous top quark dipole moments can arise, which may be revealed by a precise measurement of top quark pair production. We present results from detailed Monte Carlo studies for the ILC at 500 GeV and CLIC at 380 GeV and use parton-level simulations to explore the potential of high-energy operation. We find that precise measurements in e + e − → tt production with subsequent decay to lepton plus jets final states can provide sufficient sensitivity to detect Higgs-boson-induced CP violation in a viable two-Higgs-doublet model. The potential of a linear e + e − collider to detect CP-violating electric and weak dipole form factors of the top quark exceeds the prospects of the HL-LHC by over an order of magnitude.

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“…Particle-flow objects are clustered into exactly four jets. Heavy-flavour jets are identified using the LCFI algorithm [65,66].…”

Section: Full Simulation: Ilc At 500 Gevmentioning

confidence: 99%

CP-violating top quark couplings at future linear $$e^+e^-$$ e + e - colliders

et al. 2018

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“…Let us, e.g., assume the same specifications for b tagging as before, but a degraded c tagging efficiency of only 60 %. Even though the mis-tag rates will then decrease accordingly (subject to the LCFIPlus performance [36]), redoing the above calculation shows a further enhancement of thebb background, r bb = 13.5, with an expected worsened significance z ≈ √ S/3.9. Note that the above estimates were obtained for a given fixed branching ratio B(h → bj) = 0.73 %.…”

Section: Jhep12(2017)105mentioning

confidence: 83%

“…which are based on the expected performance of the LCFIPlus software [36]. Note that at the ILC it will not be possible to differentiate between jets from s and d quarks, rendering the Higgs decays to bs and bd effectively indistinguishable.…”

Section: Analysis Detailsmentioning

confidence: 99%

Quark flavour-violating Higgs decays at the ILC

Barducci

Helmboldt

2017

J. High Energ. Phys.

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Flavour-violating Higgs interactions are suppressed in the Standard Model such that their observation would be a clear sign of new physics. We investigate the prospects for detecting quark flavour-violating Higgs decays in the clean ILC environment. Concentrating on the decay to a bottom and a light quark j, we identify the dominant Standard Model background channels as coming from hadronic Standard Model Higgs decays with mis-identified jets. Therefore, good flavour tagging capabilities are essential to keep the background rate under control. Through a simple cut-based analysis, we find that the most promising search channel is the two-jet plus missing energy signature e + e − → bj + / E T . At 500 GeV, the expected 95 % CL upper limit on B(h → bj) is of order 10 −3 . Correspondingly, a 5 σ discovery is expected to be possible for branching ratios as low as a few 10 −3 .

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“…We assume that the b-tagging efficiency, the rates of misidentifying the c-jet and the light-quark jet as a b-jet are 0.8, 0.08 and 0.01, respectively [33]. To reconstruct the W and H bosons, we require that the invariant mass of the light jet pair and the b-jet pair satisfies [34] 3 It should be noted that although the energy of an electron can be measured in the electromagnetic calorimeter, the measurement is not statistically independent of the tracking determination of its momentum so that these two measurements cannot be combined [30].…”

Section: The H → Bb Casementioning

confidence: 99%

Measuring the ratio of HW W and HZZ couplings through W +W −H production

Chiang

2018

J. High Energ. Phys.

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For a generic Higgs boson, measuring the relative sign and magnitude of its couplings with the W and Z bosons is essential in determining its origin. Such a test is also indispensable for the 125-GeV Higgs boson. We propose that the ratio of the HW W and HZZ couplings λ W Z can be directly determined through the W + W − H production, where H denotes a generic Higgs boson, owing to the tree-level interference effect. While this is impractical at the LHC due to the limited sensitivity, it can be done at future e + e − colliders, such as a 500-GeV ILC with the beam polarization P (e − , e + ) = (−0.8, +0.3) in the jj ± bb and ± ± ∓ jj channels. The discovery potential of a general ratio and the power to discriminate it from the SM value are studied in detail. Combining the cross section of e + e − → W + W − H with the measurements of HZZ coupling at the HL-LHC, one can further improve the sensitivity of λ W Z .

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LCFIPlus: A framework for jet analysis in linear collider studies

Cited by 80 publications

References 12 publications

CP-violating top quark couplings at future linear $$e^+e^-$$ e + e - colliders

CP-violating top quark couplings at future linear $$e^+e^-$$ e + e - colliders

Quark flavour-violating Higgs decays at the ILC

Measuring the ratio of HW W and HZZ couplings through W +W −H production

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