Abstract
We propose a novel method in that quark-gluon tagging of the jets emitted as initial state radiation (ISR) can boost searches of invisible Higgs from gluon fusion processes against irreducible electroweak vector boson productions. While quark ISR typically takes up a dominant portion than gluon in the background processes mainly by frequent quark-gluon initiated hard scatterings at the LHC, gluon ISR portion in the gluon fusion can be significantly larger in the central region of detector. Focusing on invisible Higgs searches using jet substructure variables capturing the new features, we demonstrate that Higgs from gluon fusion constrains invisible Higgs decays the most, over vector boson fusion traditionally known as the most constraining, and the limit on the branching ratio is significantly improved. We summarize with emphasizing that our method has wider implications in search for new resonances from gluon fusion processes.
Highlights
The Higgs boson discovery at the LHC in 2012 completed the Standard Model (SM) as a description of nature in terms of elementary particles and their interactions [1,2], and the precision measurement of the SM Higgs boson couplings is one of the most important tasks for probing new physics and the dynamics of electroweak symmetry breaking of the Universe at future collider experiments [3]
We focus on the sizable differences in quark-gluon composition of the central initial state radiation (ISR) jets between the general ggH productions and their irreducible electroweak vector bosons (EWVBs) backgrounds
To prove its experimental feasibility, we apply the new method in search for invisible Higgs boson decays and show that the limit on the Higgs boson invisible decay branching ratio can be improved significantly (60% → 5%) for the most dominant gluon fusion, to be the most constraining channel, which has been not so useful compared to the other channels at the LHC
Summary
The Higgs boson discovery at the LHC in 2012 completed the Standard Model (SM) as a description of nature in terms of elementary particles and their interactions [1,2], and the precision measurement of the SM Higgs boson couplings is one of the most important tasks for probing new physics and the dynamics of electroweak symmetry breaking of the Universe at future collider experiments [3]. In result, tagging the Higgs boson from gluon fusion has been suffering from the irreducible backgrounds much more than the other subdominant productions including vector boson fusion (VBF), Higgsstrahlung (VH), and ttH, as it does not have associated objects with fixed particle identity good for tagging the whole process For this reason, the most stringent constraints for probing the Yukawa couplings of Higgs bosons have usually been obtained via the non-ggH processes, e.g., in H → bb [6], cc [7], τþτ− [8], μþμ− [9], and eþe− [10]. We focus on the sizable differences in quark-gluon composition of the central initial state radiation (ISR) jets between the general ggH productions and their irreducible EWVB backgrounds. Based on such differences, we show that tagging the central gluon jets from ISR can provide useful discrimination power to overall Higgs boson searches.
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