Evidence for the associated production of the Higgs boson and a top quark pair with the ATLAS detector

Research output: Contribution to journalArticle

  • Authors:
  • ATLAS Collaboration
  • Agni Bethani
  • Rafal Bielski
  • Ian Connelly
  • Brian Cox
  • Cinzia Da Via
  • Nicholas Dann
  • Giulio Forcolin
  • Alessandra Forti
  • James Howarth
  • David Lack
  • Frederick Loebinger
  • Stephen Marsden
  • Jiri Masik
  • Stephen Menary
  • Francisca Munoz Sanchez
  • Alexander Oh
  • Emily Orgill
  • Joleen Pater
  • Andrew Pilkington
  • Darren Price
  • John Raine
  • Jacob Rawling
  • Rhys Roberts
  • Savanna Shaw
  • Lee Tomlinson
  • Stephen Watts
  • Fabian Wilk
  • Terence Wyatt

Abstract

A search for the associated production of the Higgs boson with a top quark pair (t¯tH) is reported. The search is performed in multilepton final states using a data set corresponding to an integrated luminosity of 36.1fb−1 of proton-proton collision data recorded by the ATLAS experiment at a center-of-mass energy √s=13  TeV at the Large Hadron Collider. Higgs boson decays to WW∗, ττ, and ZZ∗
are targeted. Seven final states, categorized by the number and flavor of charged-lepton candidates, are examined for the presence of the Standard Model Higgs boson with a mass of 125 GeV and a pair of top quarks. An excess of events over the expected background from Standard Model processes is found with an observed significance of 4.1 standard deviations, compared to an expectation of 2.8 standard deviations. The best fit for the
t
¯
t
H
production cross section is
σ
(
t
¯
t
H
)
=
79
0
+
230

210


fb
, in agreement with the Standard Model prediction of
50
7
+
35

50


fb
. The combination of this result with other
t
¯
t
H
searches from the ATLAS experiment using the Higgs boson decay modes to
b
¯
b
,
γ
γ
and
Z
Z


4

, has an observed significance of 4.2 standard deviations, compared to an expectation of 3.8 standard deviations. This provides evidence for the
t
¯
t
H
production mode.

Bibliographical metadata

Original languageEnglish
JournalPhysical Review D - Particles, Fields, Gravitation and Cosmology
Volume97
Issue number7
DOIs
Publication statusPublished - 9 Apr 2018