Determining the structure of Higgs couplings at the CERN LargeHadron Collider.

Department of Physics, University of Wisconsin, Madison, Wisconsin, USA.
Physical Review Letters (Impact Factor: 7.73). 03/2002; 88(5):051801. DOI: 10.1103/PhysRevLett.88.051801
Source: PubMed

ABSTRACT Higgs boson production via weak boson fusion at the CERN Large Hadron Collider has the capability to determine the dominant CP nature of a Higgs boson, via the tensor structure of its coupling to weak bosons. This information is contained in the azimuthal angle distribution of the two outgoing forward tagging jets. The technique is independent of both the Higgs boson mass and the observed decay channel.

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    ABSTRACT: We investigate methods to explore the CP nature of the $ t\bar{t}h $ coupling at the LHC, focusing on associated production of the Higgs with a $t \bar{t}$ pair. We first discuss the constraints implied by low-energy observables and by the Higgs-rate information from available LHC data, emphasizing that they cannot provide conclusive evidence on the nature of this coupling. We then investigate kinematic observables that could probe the $ t\bar{t}h $ coupling directly, in particular quantities that can be constructed out of just lab-frame kinematics. We define one such observable by exploiting the fact that $t \bar{t}$ spin correlations do also carry information about the CP-nature of the $ t\bar{t}h $ coupling. Finally, we introduce a CP-odd quantity and a related asymmetry, able to probe CP violation in the $ t\bar{t}h $ coupling and likewise constructed out of lab-frame momenta only.
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    ABSTRACT: An azimuthal angle correlation between two jets is studied in the top quark pair plus multi-jet process at the 14 TeV LHC. The event samples are generated by merging the ttbar plus up to 3 partons matrix elements with parton showers. The generated event samples exhibit a strong azimuthal angle correlation between the two highest p_T jets with large rapidity separation, when the ttbar plus up to 2 or 3 partons matrix elements are properly merged. The distribution of the azimuthal angle correlation differs non-negligibly from the prediction of the matrix element level, mainly because of the strong Sudakov suppression of events with relatively low p_T jets. The impacts of including the ttbar plus 3 partons matrix elements in the merging are studied in detail, and they are found to improve significantly the prediction of the azimuthal angle correlation.
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    ABSTRACT: Publisher’s description: With the discovery of the Higgs boson, the LHC experiments have closed the most important gap in our understanding of fundamental interactions, confirming that such interactions between elementary particles can be described by quantum field theory, more specifically by a renormalizable gauge theory. This theory is a priori valid for arbitrarily high energy scales and does not require an ultraviolet completion. Yet, when trying to apply the concrete knowledge of quantum field theory to actual LHC physics – in particular to the Higgs sector and certain regimes of QCD – one inevitably encounters an intricate maze of phenomenological know-how, common lore and other, often historically developed intuitions about what works and what doesn’t. These lectures cover three aspects to help understand LHC results in the Higgs sector and in searches for physics beyond the Standard Model: they discuss the many facets of Higgs physics, which is at the core of this significantly expanded second edition; then QCD, to the degree relevant for LHC measurements; as well as further standard phenomenological background knowledge. They are intended to serve as a brief but sufficiently detailed primer on LHC physics to enable graduate students and all newcomers to the field to find their way through the more advanced literature, and to help those starting to work in this very timely and exciting field of research. Advanced readers will benefit from this course-based text for their own lectures and seminars. See the review of the first edition in [Zbl 1243.81015].

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