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Title: Measuring the CP property of Higgs coupling to tau leptons in the VBF channel at the LHC

Abstract

Here, we study the prospects of measuring the CP property of the Higgs (h) coupling to tau leptons using the vector boson fusion (VBF) production mode at the high-luminosity LHC. Utilizing the previously proposed angle between the planes spanned by the momentum vectors of the (π +π 0) and (π -π 0) pairs originating in τ ± decays as the CP-odd observable, we perform a detailed Monte Carlo analysis, taking into account the relevant standard model backgrounds, as well as detector resolution effects. We then found that excluding a pure CP-odd coupling hypothesis requires O(400 fb -1) luminosity at the 14TeV LHC, and values of the CP-mixing angle larger than about 25° can be excluded at 95% con fidence level using 3 ab -1 data. It is observed that the uncertainty in the angular resolution of the neutral pion momenta does not constitute a signifi cant hurdle. Achieving a signal to background ratio (S=B) close to one, while keeping a high enough signal yield required to study the angular distributions selects out VBF as a promising mode to probe the CP nature of the hττ coupling, with gluon fusion suffering from a low S=B, and the W ±h=Zh mode (withmore » leptonically decaying W ±=Z) having a much smaller signal rate.« less

Authors:
 [1];  [2];  [3];  [1]
  1. Univ. of Pittsburgh, PA (United States). Dept. of Physics and Astronomy; Tsinghua Univ., Beijing (China). Dept. of Physics
  2. Univ. of Pittsburgh, PA (United States). Dept. of Physics and Astronomy
  3. Harish-Chandra Research Inst., Allahabad (India)
Publication Date:
Research Org.:
Univ. of Wisconsin, Madison, WI (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1389301
Grant/Contract Number:
FG02-95ER40896
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of High Energy Physics (Online)
Additional Journal Information:
Journal Name: Journal of High Energy Physics (Online); Journal Volume: 2017; Journal Issue: 5; Journal ID: ISSN 1029-8479
Publisher:
Springer Berlin
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; Higgs Physics; CP violation

Citation Formats

Han, Tao, Mukhopadhyay, Satyanarayan, Mukhopadhyaya, Biswarup, and Wu, Yongcheng. Measuring the CP property of Higgs coupling to tau leptons in the VBF channel at the LHC. United States: N. p., 2017. Web. doi:10.1007/JHEP05(2017)128.
Han, Tao, Mukhopadhyay, Satyanarayan, Mukhopadhyaya, Biswarup, & Wu, Yongcheng. Measuring the CP property of Higgs coupling to tau leptons in the VBF channel at the LHC. United States. doi:10.1007/JHEP05(2017)128.
Han, Tao, Mukhopadhyay, Satyanarayan, Mukhopadhyaya, Biswarup, and Wu, Yongcheng. Tue . "Measuring the CP property of Higgs coupling to tau leptons in the VBF channel at the LHC". United States. doi:10.1007/JHEP05(2017)128. https://www.osti.gov/servlets/purl/1389301.
@article{osti_1389301,
title = {Measuring the CP property of Higgs coupling to tau leptons in the VBF channel at the LHC},
author = {Han, Tao and Mukhopadhyay, Satyanarayan and Mukhopadhyaya, Biswarup and Wu, Yongcheng},
abstractNote = {Here, we study the prospects of measuring the CP property of the Higgs (h) coupling to tau leptons using the vector boson fusion (VBF) production mode at the high-luminosity LHC. Utilizing the previously proposed angle between the planes spanned by the momentum vectors of the (π+π0) and (π-π0) pairs originating in τ± decays as the CP-odd observable, we perform a detailed Monte Carlo analysis, taking into account the relevant standard model backgrounds, as well as detector resolution effects. We then found that excluding a pure CP-odd coupling hypothesis requires O(400 fb-1) luminosity at the 14TeV LHC, and values of the CP-mixing angle larger than about 25° can be excluded at 95% con fidence level using 3 ab-1 data. It is observed that the uncertainty in the angular resolution of the neutral pion momenta does not constitute a signifi cant hurdle. Achieving a signal to background ratio (S=B) close to one, while keeping a high enough signal yield required to study the angular distributions selects out VBF as a promising mode to probe the CP nature of the hττ coupling, with gluon fusion suffering from a low S=B, and the W±h=Zh mode (with leptonically decaying W±=Z) having a much smaller signal rate.},
doi = {10.1007/JHEP05(2017)128},
journal = {Journal of High Energy Physics (Online)},
number = 5,
volume = 2017,
place = {United States},
year = {Tue May 23 00:00:00 EDT 2017},
month = {Tue May 23 00:00:00 EDT 2017}
}

Journal Article:
Free Publicly Available Full Text
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  • The search for a new source of CP violation is one of the most important endeavors in particle physics. A particularly interesting way to perform this search is to probe the CP phase in themore » $$h\tau\tau$$ coupling, as the phase is currently completely unconstrained by all existing data. Recently, a novel variable $$\Theta$$ was proposed for measuring the CP phase in the $$h\tau\tau$$ coupling through the $$\tau^\pm \to \pi^\pm \pi^0 \nu$$ decay mode. We examine two crucial questions that the real LHC detectors must face, namely, the issue of neutrino reconstruction and the effects of finite detector resolution. For the former, we find strong evidence that the collinear approximation is the best for the $$\Theta$$ variable. For the latter, we find that the angular resolution is actually not an issue even though the reconstruction of $$\Theta$$ requires resolving the highly collimated $$\pi^\pm$$'s and $$\pi^0$$'s from the $$\tau$$ decays. Instead, we find that it is the missing transverse energy resolution that significantly limits the LHC reach for measuring the CP phase via $$\Theta$$.« less
  • We exploit the spin and kinematic correlations in the decay of a scalar boson into a pair of real or virtual W-bosons, with both W-bosons decaying leptonically, for Higgs boson discovery at 7 TeV LHC energy with 10 fb{sup -1} luminosity. Without reconstruction of the events, we obtain estimators of the Higgs mass from the peak and width of the signal distribution in m{sub ll}. The separation of signal and background with other distributions, such as the azimuthal angle between two W decay planes, the rapidity difference between the two leptons, missing E{sub T}, and the p{sub T} of leptons,more » are also prescribed. Our approach identifies the salient Higgs to dilepton signatures that allow subtraction of the continuum W*W* background.« less
  • Cited by 7
  • Results of a search for H → ττ decays are presented, based on the full set of proton-proton collision data recorded by the ATLAS experiment at the LHC during 2011 and 2012. The data correspond to integrated luminosities of 4.5 fb –1 and 20.3 fb –1 at centre-of-mass energies of √s=7 TeV and √s=8 TeV respectively. All combinations of leptonic (τ → ℓνν¯ with ℓ = e, μ) and hadronic (τ → hadrons ν) tau decays are considered. An excess of events over the expected background from other Standard Model processes is found with an observed (expected) significance of 4.5more » (3.4) standard deviations. This excess provides evidence for the direct coupling of the recently discovered Higgs boson to fermions. The measured signal strength, normalized to the Standard Model expectation, of μ = 1.43 –0.37 +0.43 is consistent with the predicted Yukawa coupling strength in the Standard Model.« less