Search for the standard model Higgs boson produced in association with top quarks and decaying into a bb¯ pair in pp collisions at

M. Aaboud¹,

G. Aad²,

B. Abbott³

et al.

Abstract

A search for the standard model Higgs boson produced in association with a top-quark pair, ttH, is presented. The analysis uses 36.1 fb −1 of pp collision data at ffiffi ffi s p ¼ 13 TeV collected with the ATLAS detector at the Large Hadron Collider in 2015 and 2016. The search targets the H → bb decay mode. The selected events contain either one or two electrons or muons from the top-quark decays, and are then categorized according to the number of jets and how likely these are to contain b-hadrons. Multivariate techniques are used to discriminate between signal and background events, the latter being dominated by tt þ jets production. For a Higgs boson mass of 125 GeV, the ratio of the measured ttH signal cross-section to the standard model expectation is found to be μ ¼ 0.84 þ0.64 −0.61 . A value of μ greater than 2.0 is excluded at 95% confidence level (C.L.) while the expected upper limit is μ < 1.2 in the absence of a ttH signal.

Flavorful two-Higgs-doublet models with a twist

“…h 1 → µµ [44,45], and top associated production [46,47]. The projected sensitivities are taken from [48], and correspond to 3000 fb −1 of data collected at 14 TeV.…”

CP tests of Higgs couplings in tt¯h semileptonic events at the LHC

“…5 (top) includes the contributions from light and c jets, which, as can be seen in Table I, is a significant background after the final event selection applied in this paper. Restricting the selection to four b-tagged jets, the signal significance can increase at the expense of some statistical loss, and the background composition changes to a more ttbb-dominated sample [40]. This is the main reason why signal angular distributions are shown against the ttbb background.…”

Measuring properties of a Heavy Higgs boson in the $$ H\to t\overline{t}\to b{W}^{+}\overline{b}{W}^{-} $$ decay

“…Note that rec includes the efficiency of fully reconstructing the four momenta of the t andt quarks which are necessary to measure the Φ distribution. 8 We observe that rec may also account for the dilutions due to interference with irreducible backgrounds and incorrect reconstruction of the neutrino momentum. One may achieve rec ∼ 1 at the future e + e − colliders but the production cross sections would be much suppressed compared to pp colliders.…”

“…The output values together 7 Numerically, we find that the absolute difference is smaller than 5 × 10 −3 for the 6 scenarios under consideration. 8 Using the pseudo-top algorithm, for example, the missing neutrino momentum can be reconstructed with a two-fold ambiguity at the LHC [26]. See also, for example, ref.…”

“…The coupling to the top-quark pair from global fits has about 20-30% uncertainty [7]. There was also direct measurements of the top Yukawa coupling in pp → tth production [8,9], which still needs more data to have more precise measurements than the global fitting.…”