Angular distributions in $t\overline{t}H(H\to b\overline{b})$ reconstructed events at the LHC

The associated production of a Higgs boson and a top-quark pair, $t\overline{t}H$, in proton-proton collisions is addressed in this paper for a center of mass energy of 13 TeV at the LHC. Dileptonic final states of $t\overline{t}H$ events with two oppositely charged leptons and four jets from the decays $t\to b{W}^{+}\to b{\ell }^{+}{\nu }_{\ell }$, $\overline{t}\to \overline{b}{W}^{-}\to \overline{b}{\ell }^{-}{\overline{\nu }}_{\ell }$ and $h\to b\overline{b}$, are used. Signal events, generated with MadGraph5_aMC@NLO, are fully reconstructed by applying a kinematic fit. New angular distributions of the decay products as well as angular asymmetries are explored in order to improve discrimination of $t\overline{t}H$ signal events over the dominant irreducible background contribution, $t\overline{t}b\overline{b}$. Even after the full kinematic fit reconstruction of the events, the proposed angular distributions and asymmetries are still quite different in the $t\overline{t}H$ signal and the dominant background ($t\overline{t}b\overline{b}$).

Figure 1

Neutrino (left) and antineutrino (right) $p_T$ distributions. The generated distribution (shadowed region) is compared with the kinematical fit reconstruction with truth match (full line) distribution.

Figure 2

Same as in Fig. 1, but for the top (left) and antitop quarks (right) $p_T$ distributions.

Figure 3

Same as in Fig. 1, but for the $W^{+}$ (left) and $W^{-}$ (right) $p_T$ distributions.

Figure 4

Reconstructed top (left) and antitop (right) quark $p_T$ using the kinematical fit (without truth match) as a function of the $p_T$ at parton level.

Figure 5

Same as in Fig. 4, but for the $W^{+}$ (left) and $W^{-}$ (right) $p_T$ distributions.

Figure 6

Generated product of the cosine of the angle between the Higgs momentum direction (in the $\overline{t}H$ center-of-mass) with respect to the $\overline{t}H$ direction (in the $t\overline{t}H$ system), and the cosine of the angle of the ${\ell }^{+}(\text{left})$ and ${\ell }^{-}(\text{right})$ momentum (in the Higgs center-of-mass system) with respect to the Higgs direction (in the $\overline{t}H$ system).

Figure 7

Same as in Fig. 6, but after applying the acceptance cuts.

Figure 8

Same as in Fig. 7, but using reconstructed objects with truth match.

Figure 9

Same as in Fig. 8, but without truth match.

Figure 10

Reconstructed product (without truth match) of the cosine of the angle between the Higgs momentum direction (in the $\overline{t}H$ center-of-mass) with respect to the $\overline{t}H$ direction (in the $t\overline{t}H$ system), and the cosine of the angle of the $W^{+}(\text{left})$ and $W^{-}(\text{right})$ momentum (in the Higgs center-of-mass system) with respect to the Higgs direction (in the $\overline{t}H$ system).

Figure 11

Reconstructed product (without truth match) of the cosine of the angle between the Higgs momentum direction (in the $\overline{t}H$ center-of-mass) with respect to the $\overline{t}H$ direction (in the $t\overline{t}H$ system), and the cosine of the angle of the Higgs $b$-quark(left) and $\overline{t}$-quark(right) momentum (in the Higgs center-of-mass system) with respect to the Higgs direction (in the $\overline{t}H$ system).

Figure 12

Two binned generated product of the cosine of the angle between the Higgs momentum direction (in the $\overline{t}H$ center-of-mass) with respect to the $\overline{t}H$ direction (in the $t\overline{t}H$ system), and the cosine of the angle of the ${\ell }^{+}(\text{left})$ and ${\ell }^{-}(\text{right})$ momentum (in the Higgs center-of-mass system) with respect to the Higgs direction (in the $\overline{t}H$ system).

Figure 13

Two binned reconstructed product (without truth match) of the cosine of the angle between the Higgs momentum direction (in the $\overline{t}H$ center-of-mass) with respect to the $\overline{t}H$ direction (in the $t\overline{t}H$ system), and the cosine of the angle of the ${\ell }^{+}(\text{left})$ and ${\ell }^{-}(\text{right})$ momentum (in the Higgs center-of-mass system) with respect to the Higgs direction (in the $\overline{t}H$ system).

Figure 14

Higgs reconstructed mass (without truth match) fit (see text for details). The dashed line corresponds to the signal and shaded region the combinatorial background.