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New searches for the Higgs boson

The discovery of the Higgs boson in 2012 did not only provide confirmation of the standard model of particle physics, it also heralded a new era of precision Higgs physics. EU-funded scientists have now measured and estimated the rate at which Higgs boson is produced by vector boson fusion.
New searches for the Higgs boson
Before 2012, all the particles described in the standard model had been observed, with the exception of the Higgs boson. A Toroidal LHC Apparatus (ATLAS) and the Compact Muon Solenoid (CMS) around the Large Hadron Collider (LHC) detected a particle whose properties resembled that of the Higgs boson.

Subsequent measurements by the two experiments confirmed that the Higgs boson exists. The EU-funded project HIGGSWBF (A path to understanding: Precision studies of the Higgs boson through weak boson fusion) attempted to measure the production rate of the Higgs boson through rare and interesting processes.

HIGGSWBF scientists picked up where previous studies have left off, namely measurements of what are known as dijets produced via strong nuclear and electroweak interaction in association with the W boson. The W is a vector boson, one of the carrier particles of the weak nuclear force.

W bosons and hadronic jets are produced in different ways at the LHC. Electroweak processes involve the radiation of the vector boson W off quarks, and that is an unusual thing to happen – much more unusual than a quark and an antiquark annihilating and producing a W.

These processes are interesting because the Higgs boson is also produced. According to the standard model, a significant fraction of Higgs bosons should be seen produced this way. They are also closely related to vector boson diffusion, where the Higgs boson plays a central role.

The HIGGSWBF scientists refined existing methods used to model the production of W and dijets. They also introduced two quantities, named jet centrality and lepton centrality, indicating the location of any additional jets and the decay products of the W boson, respectively.

While mining the data from the 2010-2012 LHC run, these tools allowed the scientists to define control regions where background processes that mimic W boson and dijets production could be constrained. More importantly, the desired signal was measured directly from the data without reliance on theoretical input.

The same techniques can be used for the measurement of any particle that is colour neutral and produced in association with dijets in similar vector boson fusion topologies. These colour-neutral particles are involved in, among other areas, the search for a doubly-charged Higgs, Majorana neutrinos and lepton flavour violating phenomena.

The HIGGSWBF project has opened up new avenues of research that promise the discovery of new elementary particle physics beyond the standard model.

Related information

Keywords

Higgs boson, standard model, particle physics, vector boson diffusion, HIGGSWBF, W boson
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