This paper presents measurements of top-antitop quark pair ($t\bar{t}$) production in association with additional $b$-jets. The analysis utilises 140 fb$^{-1}$ of proton-proton collision data collected with the ATLAS detector at the Large Hadron Collider at a centre-of-mass energy of 13 TeV. Fiducial cross-sections are extracted in a final state featuring one electron and one muon, with at least three or four $b$-jets. Results are presented at the particle level for both integrated cross-sections and normalised differential cross-sections, as functions of global event properties, jet kinematics, and $b$-jet pair properties. Observable quantities characterising $b$-jets originating from the top quark decay and additional $b$-jets are also measured at the particle level, after correcting for detector effects. The measured integrated fiducial cross-sections are consistent with $t\bar{t}b\bar{b}$ predictions from various next-to-leading-order matrix element calculations matched to a parton shower within the uncertainties of the predictions. State-of-the-art theoretical predictions are compared with the differential measurements; none of them simultaneously describes all observables. Differences between any two predictions are smaller than the measurement uncertainties for most observables.
- - - - - - - - Overview of HEPData Record - - - - - - - - <br/><br/> ATLAS public webpage of paper: <a href="https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/TOPQ-2019-03/">link</a><br/><br/> <b>Fiducial phase space definitions:</b><br/> <i>Particle level:</i> <ul> <li> Common: N E = N MU = 1, CHARGE E != CHARGE MU <li> NJETS >= 2, NBJETS >= 2 <li> NJETS >= 3, NBJETS >= 3 <li> NJETS >= 4, NBJETS >= 3 <li> NJETS >= 4, NBJETS >= 4 <li> NJETS >= 5, NBJETS >= 4 </ul><br/> <b>Objects definitions:</b> <ul> <li> LEP PT > 28 GeV, ABS ETARAP LEP < 2.5 <li> JET PT > 25 GeV, ABS ETARAP JET < 2.5, R JET = 0.4 <li> BJET: >=1 b-hadron with PT > 5 GeV is associated to the jet via ghost matching </ul><br/> <b>Particle level:</b><br/> <br/>Data from Table 06: <a href="153521?table="Fiducial xsec results>Fiducial xsec results </a><br/><br/> <u>1D:</u><br/> Data bootstraps: <ul> <li> Data from Figure 09: <a href="153521?table=Bootstrap $N_{b-jets}$ in $≥2b$">Bootstrap $N_{b-jets}$ in $≥2b$ </a> <li> Data from Figure 10a: <a href="153521?table=Bootstrap $N_{b-jets}$ in $≥3b$">Bootstrap $N_{b-jets}$ in $≥3b$ </a> <li> Data from Figure 10b: <a href="153521?table=Bootstrap $N_{c/l-jets}$ in $≥3b$">Bootstrap $N_{c/l-jets}$ in $≥3b$ </a> <li> Data from Figure 10c: <a href="153521?table=Bootstrap $H_{T}^{had}$ in $≥3b$">Bootstrap $H_{T}^{had}$ in $≥3b$ </a> <li> Data from Figure 10d: <a href="153521?table=Bootstrap $\Delta R_{avg}^{bb}$ in $≥3b$">Bootstrap $\Delta R_{avg}^{bb}$ in $≥3b$ </a> <li> Data from Figure 11a: <a href="153521?table=Bootstrap $p_{T}(b_{1})$ in $≥3b$">Bootstrap $p_{T}(b_{1})$ in $≥3b$ </a> <li> Data from Figure 11b: <a href="153521?table=Bootstrap $p_{T}(b_{2})$ in $≥3b$">Bootstrap $p_{T}(b_{2})$ in $≥3b$ </a> <li> Data from Figure 11c: <a href="153521?table=Bootstrap $p_{T}(b_{1}^{top})$ in $≥3b$">Bootstrap $p_{T}(b_{1}^{top})$ in $≥3b$ </a> <li> Data from Figure 11d: <a href="153521?table=Bootstrap $p_{T}(b_{2}^{top})$ in $≥3b$">Bootstrap $p_{T}(b_{2}^{top})$ in $≥3b$ </a> <li> Data from Figure 12a: <a href="153521?table=Bootstrap $p_{T}(b_{3})$ in $≥3b$">Bootstrap $p_{T}(b_{3})$ in $≥3b$ </a> <li> Data from Figure 12b: <a href="153521?table=Bootstrap $p_{T}(b_{1}^{add})$ in $≥3b$">Bootstrap $p_{T}(b_{1}^{add})$ in $≥3b$ </a> <li> Data from Figure 13a: <a href="153521?table=Bootstrap $m(b_{1}b_{2})$ in $≥3b$">Bootstrap $m(b_{1}b_{2})$ in $≥3b$ </a> <li> Data from Figure 13b: <a href="153521?table=Bootstrap $p_{T}(b_{1}b_{2})$ in $≥3b$">Bootstrap $p_{T}(b_{1}b_{2})$ in $≥3b$ </a> <li> Data from Figure 13c: <a href="153521?table=Bootstrap $m(bb^{top})$ in $≥3b$">Bootstrap $m(bb^{top})$ in $≥3b$ </a> <li> Data from Figure 13d: <a href="153521?table=Bootstrap $p_{T}(bb^{top})$ in $≥3b$">Bootstrap $p_{T}(bb^{top})$ in $≥3b$ </a> <li> Data from Figure 14a: <a href="153521?table=Bootstrap $\Delta R(e\mu bb^{top}, b_{1}^{add})$ in $≥3b$">Bootstrap $\Delta R(e\mu bb^{top}, b_{1}^{add})$ in $≥3b$ </a> <li> Data from Figure 14b: <a href="153521?table=Bootstrap $\Delta R(e\mu bb^{top}, l/c-jet_{1})$ in $≥3b≥1l/c$">Bootstrap $\Delta R(e\mu bb^{top}, l/c-jet_{1})$ in $≥3b≥1l/c$ </a> <li> Data from Figure 14c: <a href="153521?table=Bootstrap $p_{T}(l/c-jet_{1})$ in $≥3b≥1l/c$">Bootstrap $p_{T}(l/c-jet_{1})$ in $≥3b≥1l/c$ </a> <li> Data from Figure 14d: <a href="153521?table=Bootstrap $p_{T}(l/c-jet_{1})-p_{T}(b_{1}^{add})$ in $≥3b≥1l/c$">Bootstrap $p_{T}(l/c-jet_{1})-p_{T}(b_{1}^{add})$ in $≥3b≥1l/c$ </a> <li> Data from Figure 15a: <a href="153521?table=Bootstrap $m(bb^{min\Delta R})$ in $≥4b$">Bootstrap $m(bb^{min\Delta R})$ in $≥4b$ </a> <li> Data from Figure 15b: <a href="153521?table=Bootstrap $p_{T}(bb^{min\Delta R})$ in $≥4b$">Bootstrap $p_{T}(bb^{min\Delta R})$ in $≥4b$ </a> <li> Data from Figure 15c: <a href="153521?table=Bootstrap $m(bb^{add})$ in $≥4b$">Bootstrap $m(bb^{add})$ in $≥4b$ </a> <li> Data from Figure 15d: <a href="153521?table=Bootstrap $p_{T}(bb^{add})$ in $≥4b$">Bootstrap $p_{T}(bb^{add})$ in $≥4b$ </a> <li> Data from Figure 01a (aux): <a href="153521?table=Bootstrap $|\eta(b_{3})|$ in $≥3b$">Bootstrap $|\eta(b_{3})|$ in $≥3b$ </a> <li> Data from Figure 01b (aux): <a href="153521?table=Bootstrap $|\eta(b_{1}^{add})|$ in $≥3b$">Bootstrap $|\eta(b_{1}^{add})|$ in $≥3b$ </a> <li> Data from Figure 02a (aux): <a href="153521?table=Bootstrap $\Delta R(b_{1}b_{2})$ in $≥3b$">Bootstrap $\Delta R(b_{1}b_{2})$ in $≥3b$ </a> <li> Data from Figure 02b (aux): <a href="153521?table=Bootstrap $m(e\mu bb^{top})$ in $≥3b$">Bootstrap $m(e\mu bb^{top})$ in $≥3b$ </a> <li> Data from Figure 03a (aux): <a href="153521?table=Bootstrap $|\eta(l/c-jet_{1})|$ in $≥3b≥1l/c$">Bootstrap $|\eta(l/c-jet_{1})|$ in $≥3b≥1l/c$ </a> <li> Data from Figure 03b (aux): <a href="153521?table=Bootstrap $\Delta\eta_{max}^{jj}$ in $≥3b$">Bootstrap $\Delta\eta_{max}^{jj}$ in $≥3b$ </a> <li> Data from Figure 04a (aux): <a href="153521?table=Bootstrap $H_{T}^{all}$ in $≥3b$">Bootstrap $H_{T}^{all}$ in $≥3b$ </a> <li> Data from Figure 04b (aux): <a href="153521?table=Bootstrap $m(e\mu b_{1}b_{2})$ in $≥3b$">Bootstrap $m(e\mu b_{1}b_{2})$ in $≥3b$ </a> <li> Data from Figure 05a (aux): <a href="153521?table=Bootstrap $|\eta(b_{1})|$ in $≥3b$">Bootstrap $|\eta(b_{1})|$ in $≥3b$ </a> <li> Data from Figure 05b (aux): <a href="153521?table=Bootstrap $|\eta(b_{2})|$ in $≥3b$">Bootstrap $|\eta(b_{2})|$ in $≥3b$ </a> <li> Data from Figure 05c (aux): <a href="153521?table=Bootstrap $|\eta(b_{1}^{top})|$ in $≥3b$">Bootstrap $|\eta(b_{1}^{top})|$ in $≥3b$ </a> <li> Data from Figure 05d (aux): <a href="153521?table=Bootstrap $|\eta(b_{2}^{top})|$ in $≥3b$">Bootstrap $|\eta(b_{2}^{top})|$ in $≥3b$ </a> <li> Data from Figure 06a (aux): <a href="153521?table=Bootstrap $p_{T}(b_{1})$ in $≥4b$">Bootstrap $p_{T}(b_{1})$ in $≥4b$ </a> <li> Data from Figure 06b (aux): <a href="153521?table=Bootstrap $p_{T}(b_{2})$ in $≥4b$">Bootstrap $p_{T}(b_{2})$ in $≥4b$ </a> <li> Data from Figure 06c (axu): <a href="153521?table=Bootstrap $p_{T}(b_{1}^{top})$ in $≥4b$">Bootstrap $p_{T}(b_{1}^{top})$ in $≥4b$ </a> <li> Data from Figure 06d (aux): <a href="153521?table=Bootstrap $p_{T}(b_{2}^{top})$ in $≥4b$">Bootstrap $p_{T}(b_{2}^{top})$ in $≥4b$ </a> <li> Data from Figure 07a (aux): <a href="153521?table=Bootstrap $p_{T}(b_{3})$ in $≥4b$">Bootstrap $p_{T}(b_{3})$ in $≥4b$ </a> <li> Data from Figure 07b (aux): <a href="153521?table=Bootstrap $p_{T}(b_{4})$ in $≥4b$">Bootstrap $p_{T}(b_{4})$ in $≥4b$ </a> <li> Data from Figure 07c (aux): <a href="153521?table=Bootstrap $p_{T}(b_{1}^{add})$ in $≥4b$">Bootstrap $p_{T}(b_{1}^{add})$ in $≥4b$ </a> <li> Data from Figure 07d (aux): <a href="153521?table=Bootstrap $p_{T}(b_{2}^{add})$ in $≥4b$">Bootstrap $p_{T}(b_{2}^{add})$ in $≥4b$ </a> <li> Data from Figure 08a (aux): <a href="153521?table=Bootstrap $m(b_{1}b_{2})$ in $≥4b$">Bootstrap $m(b_{1}b_{2})$ in $≥4b$ </a> <li> Data from Figure 08b (aux): <a href="153521?table=Bootstrap $p_{T}(b_{1}b_{2})$ in $≥4b$">Bootstrap $p_{T}(b_{1}b_{2})$ in $≥4b$ </a> <li> Data from Figure 09a (aux): <a href="153521?table=Bootstrap $m(bb^{top})$ in $≥4b$">Bootstrap $m(bb^{top})$ in $≥4b$ </a> <li> Data from Figure 09b (aux): <a href="153521?table=Bootstrap $p_{T}(bb^{top})$ in $≥4b$">Bootstrap $p_{T}(bb^{top})$ in $≥4b$ </a> <li> Data from Figure 10a (aux): <a href="153521?table=Bootstrap $H_{T}^{all}$ in $≥4b$">Bootstrap $H_{T}^{all}$ in $≥4b$ </a> <li> Data from Figure 10b (aux): <a href="153521?table=Bootstrap $m(e\mu b_{1}b_{2})$ in $≥4b$">Bootstrap $m(e\mu b_{1}b_{2})$ in $≥4b$ </a> <li> Data from Figure 11a (aux): <a href="153521?table=Bootstrap $m(e\mu bb^{top})$ in $≥4b$">Bootstrap $m(e\mu bb^{top})$ in $≥4b$ </a> <li> Data from Figure 11b (aux): <a href="153521?table=Bootstrap $H_{T}^{had}$ in $≥4b$">Bootstrap $H_{T}^{had}$ in $≥4b$ </a> <li> Data from Figure 11c (aux): <a href="153521?table=Bootstrap min$\Delta R(bb)$ in $≥4b$">Bootstrap min$\Delta R(bb)$ in $≥4b$ </a> <li> Data from Figure 11d (aux): <a href="153521?table=Bootstrap $\Delta R(e\mu bb^{top}, b_{1}^{add})$ in $≥4b$">Bootstrap $\Delta R(e\mu bb^{top}, b_{1}^{add})$ in $≥4b$ </a> <li> Data from Figure 12a (aux): <a href="153521?table=Bootstrap $\Delta R_{avg}^{bb}$ in $≥4b$">Bootstrap $\Delta R_{avg}^{bb}$ in $≥4b$ </a> <li> Data from Figure 12b (aux): <a href="153521?table=Bootstrap $\Delta\eta_{max}^{jj}$ in $≥4b$">Bootstrap $\Delta\eta_{max}^{jj}$ in $≥4b$ </a> <li> Data from Figure 12c (aux): <a href="153521?table=Bootstrap $N_{l/c-jets}$ in $≥4b$">Bootstrap $N_{l/c-jets}$ in $≥4b$ </a> <li> Data from Figure 13a (aux): <a href="153521?table=Bootstrap $p_{T}(l/c-jet_{1})$ in $≥4b≥1l/c$">Bootstrap $p_{T}(l/c-jet_{1})$ in $≥4b≥1l/c$ </a> <li> Data from Figure 13b (aux): <a href="153521?table=Bootstrap $|\eta(l/c-jet_{1})|$ in $≥4b≥1l/c$">Bootstrap $|\eta(l/c-jet_{1})|$ in $≥4b≥1l/c$ </a> <li> Data from Figure 13c (aux): <a href="153521?table=Bootstrap $\Delta R(e\mu bb^{top}, l/c-jet_{1})$ in $≥4b≥1l/c$">Bootstrap $\Delta R(e\mu bb^{top}, l/c-jet_{1})$ in $≥4b≥1l/c$ </a> <li> Data from Figure 13d (aux): <a href="153521?table=Bootstrap $p_{T}(l/c-jet_{1})-p_{T}(b_{1}^{add})$ in $≥4b≥1l/c$">Bootstrap $p_{T}(l/c-jet_{1})-p_{T}(b_{1}^{add})$ in $≥4b≥1l/c$ </a> <li> Data from Figure 14a (aux): <a href="153521?table=Bootstrap $|\eta(b_{1})|$ in $≥4b$">Bootstrap $|\eta(b_{1})|$ in $≥4b$ </a> <li> Data from Figure 14b (aux): <a href="153521?table=Bootstrap $|\eta(b_{2})|$ in $≥4b$">Bootstrap $|\eta(b_{2})|$ in $≥4b$ </a> <li> Data from Figure 14c (aux): <a href="153521?table=Bootstrap $|\eta(b_{1}^{top})|$ in $≥4b$">Bootstrap $|\eta(b_{1}^{top})|$ in $≥4b$ </a> <li> Data from Figure 14d (aux): <a href="153521?table=Bootstrap $|\eta(b_{2}^{top})|$ in $≥4b$">Bootstrap $|\eta(b_{2}^{top})|$ in $≥4b$ </a> <li> Data from Figure 15a (aux): <a href="153521?table=Bootstrap $|\eta(b_{3})|$ in $≥4b$">Bootstrap $|\eta(b_{3})|$ in $≥4b$ </a> <li> Data from Figure 15b (aux): <a href="153521?table=Bootstrap $|\eta(b_{4})|$ in $≥4b$">Bootstrap $|\eta(b_{4})|$ in $≥4b$ </a> <li> Data from Figure 15c (aux): <a href="153521?table=Bootstrap $|\eta(b_{1}^{add})|$ in $≥4b$">Bootstrap $|\eta(b_{1}^{add})|$ in $≥4b$ </a> <li> Data from Figure 15d (aux): <a href="153521?table=Bootstrap $|\eta(b_{2}^{add})|$ in $≥4b$">Bootstrap $|\eta(b_{2}^{add})|$ in $≥4b$ </a> </ul><br/> Measurements: <ul> <li> Data from Table 01 (aux): <a href="153521?table=Diff. XS $N_{b-jets}$ in $≥2b$">Diff. XS $N_{b-jets}$ in $≥2b$ </a> <li> Data from Table 02 (aux): <a href="153521?table=Diff. XS $H_{T}^{had}$ in $≥3b$">Diff. XS $H_{T}^{had}$ in $≥3b$ </a> <li> Data from Table 03 (aux): <a href="153521?table=Diff. XS $H_{T}^{all}$ in $≥3b$">Diff. XS $H_{T}^{all}$ in $≥3b$ </a> <li> Data from Table 04 (aux): <a href="153521?table=Diff. XS $\Delta R_{avg}^{bb}$ in $≥3b$">Diff. XS $\Delta R_{avg}^{bb}$ in $≥3b$ </a> <li> Data from Table 05 (aux): <a href="153521?table=Diff. XS $\Delta\eta_{max}^{jj}$ in $≥3b$">Diff. XS $\Delta\eta_{max}^{jj}$ in $≥3b$ </a> <li> Data from Table 06 (aux): <a href="153521?table=Diff. XS $p_{T}(b_{1})$ in $≥3b$">Diff. XS $p_{T}(b_{1})$ in $≥3b$ </a> <li> Data from Table 07 (aux): <a href="153521?table=Diff. XS $p_{T}(b_{1}^{top})$ in $≥3b$">Diff. XS $p_{T}(b_{1}^{top})$ in $≥3b$ </a> <li> Data from Table 08 (aux): <a href="153521?table=Diff. XS $p_{T}(b_{2})$ in $≥3b$">Diff. XS $p_{T}(b_{2})$ in $≥3b$ </a> <li> Data from Table 09 (aux): <a href="153521?table=Diff. XS $p_{T}(b_{2}^{top})$ in $≥3b$">Diff. XS $p_{T}(b_{2}^{top})$ in $≥3b$ </a> <li> Data from Table 10 (aux): <a href="153521?table=Diff. XS $p_{T}(b_{3})$ in $≥3b$">Diff. XS $p_{T}(b_{3})$ in $≥3b$ </a> <li> Data from Table 11 (aux): <a href="153521?table=Diff. XS $p_{T}(b_{1}^{add})$ in $≥3b$">Diff. XS $p_{T}(b_{1}^{add})$ in $≥3b$ </a> <li> Data from Table 12 (aux): <a href="153521?table=Diff. XS $|\eta(b_{1})|$ in $≥3b$">Diff. XS $|\eta(b_{1})|$ in $≥3b$ </a> <li> Data from Table 13 (aux): <a href="153521?table=Diff. XS $|\eta(b_{1}^{top})|$ in $≥3b$">Diff. XS $|\eta(b_{1}^{top})|$ in $≥3b$ </a> <li> Data from Table 14 (aux): <a href="153521?table=Diff. XS $|\eta(b_{2})|$ in $≥3b$">Diff. XS $|\eta(b_{2})|$ in $≥3b$ </a> <li> Data from Table 15 (aux): <a href="153521?table=Diff. XS $|\eta(b_{2}^{top})|$ in $≥3b$">Diff. XS $|\eta(b_{2}^{top})|$ in $≥3b$ </a> <li> Data from Table 16 (aux): <a href="153521?table=Diff. XS $|\eta(b_{3})|$ in $≥3b$">Diff. XS $|\eta(b_{3})|$ in $≥3b$ </a> <li> Data from Table 17 (aux): <a href="153521?table=Diff. XS $|\eta(b_{1}^{add})|$ in $≥3b$">Diff. XS $|\eta(b_{1}^{add})|$ in $≥3b$ </a> <li> Data from Table 18 (aux): <a href="153521?table=Diff. XS $m(b_{1}b_{2})$ in $≥3b$">Diff. XS $m(b_{1}b_{2})$ in $≥3b$ </a> <li> Data from Table 19 (aux): <a href="153521?table=Diff. XS $p_{T}(b_{1}b_{2})$ in $≥3b$">Diff. XS $p_{T}(b_{1}b_{2})$ in $≥3b$ </a> <li> Data from Table 20 (aux): <a href="153521?table=Diff. XS $m(bb^{top})$ in $≥3b$">Diff. XS $m(bb^{top})$ in $≥3b$ </a> <li> Data from Table 21 (aux): <a href="153521?table=Diff. XS $p_{T}(bb^{top})$ in $≥3b$">Diff. XS $p_{T}(bb^{top})$ in $≥3b$ </a> <li> Data from Table 22 (aux): <a href="153521?table=Diff. XS $m(e\mu b_{1}b_{2})$ in $≥3b$">Diff. XS $m(e\mu b_{1}b_{2})$ in $≥3b$ </a> <li> Data from Table 23 (aux): <a href="153521?table=Diff. XS $m(e\mu bb^{top})$ in $≥3b$">Diff. XS $m(e\mu bb^{top})$ in $≥3b$ </a> <li> Data from Table 24 (aux): <a href="153521?table=Diff. XS $\Delta R(b_{1}b_{2})$ in $≥3b$">Diff. XS $\Delta R(b_{1}b_{2})$ in $≥3b$ </a> <li> Data from Table 25 (aux): <a href="153521?table=Diff. XS $N_{l/c-jets}$ in $≥3b$">Diff. XS $N_{l/c-jets}$ in $≥3b$ </a> <li> Data from Table 26 (aux): <a href="153521?table=Diff. XS $\Delta R(e\mu b_{1}b_{2},b_{3})$ in $≥3b$">Diff. XS $\Delta R(e\mu b_{1}b_{2},b_{3})$ in $≥3b$ </a> <li> Data from Table 27 (aux): <a href="153521?table=Diff. XS $\Delta R(e\mu bb^{top}, b_{1}^{add})$ in $≥3b$">Diff. XS $\Delta R(e\mu bb^{top}, b_{1}^{add})$ in $≥3b$ </a> <li> Data from Table 28 (aux): <a href="153521?table=Diff. XS $\Delta R(e\mu bb^{top},l/c-jet)$ in $≥3b≥1l/c$">Diff. XS $\Delta R(e\mu bb^{top},l/c-jet)$ in $≥3b≥1l/c$ </a> <li> Data from Table 29 (aux): <a href="153521?table=Diff. XS $p_{T}(l/c-jet_{1}) - p_{T}(b_{1}^{add})$ in $≥3b≥1l/c$">Diff. XS $p_{T}(l/c-jet_{1}) - p_{T}(b_{1}^{add})$ in $≥3b≥1l/c$ </a> <li> Data from Table 30 (aux): <a href="153521?table=Diff. XS $|\eta(l/c-jet_{1})|$ in $≥3b≥1l/c$">Diff. XS $|\eta(l/c-jet_{1})|$ in $≥3b≥1l/c$ </a> <li> Data from Table 31 (aux): <a href="153521?table=Diff. XS $p_{T}(l/c-jet_{1})$ in $≥3b≥1l/c$">Diff. XS $p_{T}(l/c-jet_{1})$ in $≥3b≥1l/c$ </a> <li> Data from Table 32 (aux): <a href="153521?table=Diff. XS $H_{T}^{had}$ in $≥4b$">Diff. XS $H_{T}^{had}$ in $≥4b$ </a> <li> Data from Table 33 (aux): <a href="153521?table=Diff. XS $H_{T}^{all}$ in $≥4b$">Diff. XS $H_{T}^{all}$ in $≥4b$ </a> <li> Data from Table 34 (aux): <a href="153521?table=Diff. XS $\Delta R_{avg}^{bb}$ in $≥4b$">Diff. XS $\Delta R_{avg}^{bb}$ in $≥4b$ </a> <li> Data from Table 35 (aux): <a href="153521?table=Diff. XS $\Delta\eta_{max}^{jj}$ in $≥4b$">Diff. XS $\Delta\eta_{max}^{jj}$ in $≥4b$ </a> <li> Data from Table 36 (aux): <a href="153521?table=Diff. XS $p_{T}(b_{1})$ in $≥4b$">Diff. XS $p_{T}(b_{1})$ in $≥4b$ </a> <li> Data from Table 37 (aux): <a href="153521?table=Diff. XS $p_{T}(b_{1}^{top})$ in $≥4b$">Diff. XS $p_{T}(b_{1}^{top})$ in $≥4b$ </a> <li> Data from Table 38 (aux): <a href="153521?table=Diff. XS $p_{T}(b_{2})$ in $≥4b$">Diff. XS $p_{T}(b_{2})$ in $≥4b$ </a> <li> Data from Table 39 (aux): <a href="153521?table=Diff. XS $p_{T}(b_{2}^{top})$ in $≥4b$">Diff. XS $p_{T}(b_{2}^{top})$ in $≥4b$ </a> <li> Data from Table 40 (aux): <a href="153521?table=Diff. XS $p_{T}(b_{3})$ in $≥4b$">Diff. XS $p_{T}(b_{3})$ in $≥4b$ </a> <li> Data from Table 41 (aux): <a href="153521?table=Diff. XS $p_{T}(b_{1}^{add})$ in $≥4b$">Diff. XS $p_{T}(b_{1}^{add})$ in $≥4b$ </a> <li> Data from Table 42 (aux): <a href="153521?table=Diff. XS $p_{T}(b_{4})$ in $≥4b$">Diff. XS $p_{T}(b_{4})$ in $≥4b$ </a> <li> Data from Table 43 (aux): <a href="153521?table=Diff. XS $p_{T}(b_{2}^{add})$ in $≥4b$">Diff. XS $p_{T}(b_{2}^{add})$ in $≥4b$ </a> <li> Data from Table 44 (aux): <a href="153521?table=Diff. XS $|\eta(b_{1})|$ in $≥4b$">Diff. XS $|\eta(b_{1})|$ in $≥4b$ </a> <li> Data from Table 45 (aux): <a href="153521?table=Diff. XS $|\eta(b_{1}^{top})|$ in $≥4b$">Diff. XS $|\eta(b_{1}^{top})|$ in $≥4b$ </a> <li> Data from Table 46 (aux): <a href="153521?table=Diff. XS $|\eta(b_{2})|$ in $≥4b$">Diff. XS $|\eta(b_{2})|$ in $≥4b$ </a> <li> Data from Table 47 (aux): <a href="153521?table=Diff. XS $|\eta(b_{2}^{top})|$ in $≥4b$">Diff. XS $|\eta(b_{2}^{top})|$ in $≥4b$ </a> <li> Data from Table 48 (aux): <a href="153521?table=Diff. XS $|\eta(b_{3})|$ in $≥4b$">Diff. XS $|\eta(b_{3})|$ in $≥4b$ </a> <li> Data from Table 49 (aux): <a href="153521?table=Diff. XS $|\eta(b_{1}^{add})|$ in $≥4b$">Diff. XS $|\eta(b_{1}^{add})|$ in $≥4b$ </a> <li> Data from Table 50 (aux): <a href="153521?table=Diff. XS $|\eta(b_{4})|$ in $≥4b$">Diff. XS $|\eta(b_{4})|$ in $≥4b$ </a> <li> Data from Table 51 (aux): <a href="153521?table=Diff. XS $|\eta(b_{2}^{add})|$ in $≥4b$">Diff. XS $|\eta(b_{2}^{add})|$ in $≥4b$ </a> <li> Data from Table 52 (aux): <a href="153521?table=Diff. XS $m(b_{1}b_{2})$ in $≥4b$">Diff. XS $m(b_{1}b_{2})$ in $≥4b$ </a> <li> Data from Table 53 (aux): <a href="153521?table=Diff. XS $p_{T}(b_{1}b_{2})$ in $≥4b$">Diff. XS $p_{T}(b_{1}b_{2})$ in $≥4b$ </a> <li> Data from Table 54 (aux): <a href="153521?table=Diff. XS $m(bb^{top})$ in $≥4b$">Diff. XS $m(bb^{top})$ in $≥4b$ </a> <li> Data from Table 55 (aux): <a href="153521?table=Diff. XS $p_{T}(bb^{top})$ in $≥4b$">Diff. XS $p_{T}(bb^{top})$ in $≥4b$ </a> <li> Data from Table 56 (aux): <a href="153521?table=Diff. XS $m(e\mu b_{1}b_{2})$ in $≥4b$">Diff. XS $m(e\mu b_{1}b_{2})$ in $≥4b$ </a> <li> Data from Table 57 (aux): <a href="153521?table=Diff. XS $m(e\mu bb^{top})$ in $≥4b$">Diff. XS $m(e\mu bb^{top})$ in $≥4b$ </a> <li> Data from Table 58 (aux): <a href="153521?table=Diff. XS $m(bb^{min\Delta R})$ in $≥4b$">Diff. XS $m(bb^{min\Delta R})$ in $≥4b$ </a> <li> Data from Table 59 (aux): <a href="153521?table=Diff. XS $p_{T}(bb^{min\Delta R})$ in $≥4b$">Diff. XS $p_{T}(bb^{min\Delta R})$ in $≥4b$ </a> <li> Data from Table 60 (aux): <a href="153521?table=Diff. XS $m(bb^{add})$ in $≥4b$">Diff. XS $m(bb^{add})$ in $≥4b$ </a> <li> Data from Table 61 (aux): <a href="153521?table=Diff. XS $p_{T}(bb^{add})$ in $≥4b$">Diff. XS $p_{T}(bb^{add})$ in $≥4b$ </a> <li> Data from Table 62 (aux): <a href="153521?table=Diff. XS $min\Delta R(bb)$ in $≥4b$">Diff. XS $min\Delta R(bb)$ in $≥4b$ </a> <li> Data from Table 63 (aux): <a href="153521?table=Diff. XS $\Delta R(b_{1}b_{2})$ in $≥4b$">Diff. XS $\Delta R(b_{1}b_{2})$ in $≥4b$ </a> <li> Data from Table 64 (aux): <a href="153521?table=Diff. XS $N_{l/c-jets}$ in $≥4b$">Diff. XS $N_{l/c-jets}$ in $≥4b$ </a> <li> Data from Table 65 (aux): <a href="153521?table=Diff. XS $\Delta R(e\mu b_{1}b_{2},b_{3})$ in $≥4b$">Diff. XS $\Delta R(e\mu b_{1}b_{2},b_{3})$ in $≥4b$ </a> <li> Data from Table 66 (aux): <a href="153521?table=Diff. XS $\Delta R(e\mu bb^{top}, b_{1}^{add})$ in $≥4b$">Diff. XS $\Delta R(e\mu bb^{top}, b_{1}^{add})$ in $≥4b$ </a> <li> Data from Table 67 (aux): <a href="153521?table=Diff. XS $\Delta R(e\mu bb^{top}, l/c-jet_{1})$ in $≥4b≥1l/c$">Diff. XS $\Delta R(e\mu bb^{top}, l/c-jet_{1})$ in $≥4b≥1l/c$ </a> <li> Data from Table 68 (aux): <a href="153521?table=Diff. XS $p_{T}(l/c-jet_{1}) - p_{T}(b_{1}^{add})$ in $≥4b≥1l/c$">Diff. XS $p_{T}(l/c-jet_{1}) - p_{T}(b_{1}^{add})$ in $≥4b≥1l/c$ </a> <li> Data from Table 69 (aux): <a href="153521?table=Diff. XS $|\eta(l/c-jet_{1})|$ in $≥4b≥1l/c$">Diff. XS $|\eta(l/c-jet_{1})|$ in $≥4b≥1l/c$ </a> <li> Data from Table 70 (aux): <a href="153521?table=Diff. XS $p_{T}(l/c-jet_{1})$ in $≥4b≥1l/c$">Diff. XS $p_{T}(l/c-jet_{1})$ in $≥4b≥1l/c$ </a> </ul><br/> <u>2D:</u><br/> Correlation matrices: <ul> <li> Data from Table 71 (aux): <a href="153521?table=Corr. mtrx $N_{b-jets}$ in $≥2b$">Corr. mtrx $N_{b-jets}$ in $≥2b$ </a> <li> Data from Table 72 (aux): <a href="153521?table=Corr. mtrx $N_{b-jets}$ in $≥3b$">Corr. mtrx $N_{b-jets}$ in $≥3b$ </a> <li> Data from Table 73 (aux): <a href="153521?table=Corr. mtrx $H_{T}^{had}$ in $≥3b$">Corr. mtrx $H_{T}^{had}$ in $≥3b$ </a> <li> Data from Table 74 (aux): <a href="153521?table=Corr. mtrx $H_{T}^{all}$ in $≥3b$">Corr. mtrx $H_{T}^{all}$ in $≥3b$ </a> <li> Data from Table 75 (aux): <a href="153521?table=Corr. mtrx $\Delta R_{avg}^{bb}$ in $≥3b$">Corr. mtrx $\Delta R_{avg}^{bb}$ in $≥3b$ </a> <li> Data from Table 76 (aux): <a href="153521?table=Corr. mtrx $\Delta\eta_{max}^{jj}$ in $≥3b$">Corr. mtrx $\Delta\eta_{max}^{jj}$ in $≥3b$ </a> <li> Data from Table 77 (aux): <a href="153521?table=Corr. mtrx $p_{T}(b_{1})$ in $≥3b$">Corr. mtrx $p_{T}(b_{1})$ in $≥3b$ </a> <li> Data from Table 78 (aux): <a href="153521?table=Corr. mtrx $p_{T}(b_{1}^{top})$ in $≥3b$">Corr. mtrx $p_{T}(b_{1}^{top})$ in $≥3b$ </a> <li> Data from Table 79 (aux): <a href="153521?table=Corr. mtrx $p_{T}(b_{2})$ in $≥3b$">Corr. mtrx $p_{T}(b_{2})$ in $≥3b$ </a> <li> Data from Table 80 (aux): <a href="153521?table=Corr. mtrx $p_{T}(b_{2}^{top})$ in $≥3b$">Corr. mtrx $p_{T}(b_{2}^{top})$ in $≥3b$ </a> <li> Data from Table 81 (aux): <a href="153521?table=Corr. mtrx $p_{T}(b_{3})$ in $≥3b$">Corr. mtrx $p_{T}(b_{3})$ in $≥3b$ </a> <li> Data from Table 82 (aux): <a href="153521?table=Corr. mtrx $p_{T}(b_{1}^{add})$ in $≥3b$">Corr. mtrx $p_{T}(b_{1}^{add})$ in $≥3b$ </a> <li> Data from Table 83 (aux): <a href="153521?table=Corr. mtrx $|\eta(b_{1})|$ in $≥3b$">Corr. mtrx $|\eta(b_{1})|$ in $≥3b$ </a> <li> Data from Table 84 (aux): <a href="153521?table=Corr. mtrx $|\eta(b_{1}^{top})|$ in $≥3b$">Corr. mtrx $|\eta(b_{1}^{top})|$ in $≥3b$ </a> <li> Data from Table 85 (aux): <a href="153521?table=Corr. mtrx $|\eta(b_{2})|$ in $≥3b$">Corr. mtrx $|\eta(b_{2})|$ in $≥3b$ </a> <li> Data from Table 86 (aux): <a href="153521?table=Corr. mtrx $|\eta(b_{2}^{top})|$ in $≥3b$">Corr. mtrx $|\eta(b_{2}^{top})|$ in $≥3b$ </a> <li> Data from Table 87 (aux): <a href="153521?table=Corr. mtrx $|\eta(b_{3})|$ in $≥3b$">Corr. mtrx $|\eta(b_{3})|$ in $≥3b$ </a> <li> Data from Table 88 (aux): <a href="153521?table=Corr. mtrx $|\eta(b_{1}^{add})|$ in $≥3b$">Corr. mtrx $|\eta(b_{1}^{add})|$ in $≥3b$ </a> <li> Data from Table 89 (aux): <a href="153521?table=Corr. mtrx $m(b_{1}b_{2})$ in $≥3b$">Corr. mtrx $m(b_{1}b_{2})$ in $≥3b$ </a> <li> Data from Table 90 (aux): <a href="153521?table=Corr. mtrx $p_{T}(b_{1}b_{2})$ in $≥3b$">Corr. mtrx $p_{T}(b_{1}b_{2})$ in $≥3b$ </a> <li> Data from Table 91 (aux): <a href="153521?table=Corr. mtrx $m(bb^{top})$ in $≥3b$">Corr. mtrx $m(bb^{top})$ in $≥3b$ </a> <li> Data from Table 92 (aux): <a href="153521?table=Corr. mtrx $p_{T}(bb^{top})$ in $≥3b$">Corr. mtrx $p_{T}(bb^{top})$ in $≥3b$ </a> <li> Data from Table 93 (aux): <a href="153521?table=Corr. mtrx $m(e\mu b_{1}b_{2})$ in $≥3b$">Corr. mtrx $m(e\mu b_{1}b_{2})$ in $≥3b$ </a> <li> Data from Table 94 (aux): <a href="153521?table=Corr. mtrx $m(e\mu bb^{top})$ in $≥3b$">Corr. mtrx $m(e\mu bb^{top})$ in $≥3b$ </a> <li> Data from Table 95 (aux): <a href="153521?table=Corr. mtrx $\Delta R(b_{1}b_{2})$ in $≥3b$">Corr. mtrx $\Delta R(b_{1}b_{2})$ in $≥3b$ </a> <li> Data from Table 96 (aux): <a href="153521?table=Corr. mtrx $N_{l/c-jets}$ in $≥3b$">Corr. mtrx $N_{l/c-jets}$ in $≥3b$ </a> <li> Data from Table 97 (aux): <a href="153521?table=Corr. mtrx $\Delta R(e\mu b_{1}b_{2},b_{3})$ in $≥3b$">Corr. mtrx $\Delta R(e\mu b_{1}b_{2},b_{3})$ in $≥3b$ </a> <li> Data from Table 98 (aux): <a href="153521?table=Corr. mtrx $\Delta R(e\mu bb^{top}, b_{1}^{add})$ in $≥3b$">Corr. mtrx $\Delta R(e\mu bb^{top}, b_{1}^{add})$ in $≥3b$ </a> <li> Data from Table 99 (aux): <a href="153521?table=Corr. mtrx $\Delta R(e\mu bb^{top},l/c-jet)$ in $≥3b≥1l/c$">Corr. mtrx $\Delta R(e\mu bb^{top},l/c-jet)$ in $≥3b≥1l/c$ </a> <li> Data from Table 100 (aux): <a href="153521?table=Corr. mtrx $p_{T}(l/c-jet_{1})-p_{T}(b_{1}^{add})$ in $≥3b≥1l/c$">Corr. mtrx $p_{T}(l/c-jet_{1})-p_{T}(b_{1}^{add})$ in $≥3b≥1l/c$ </a> <li> Data from Table 101 (aux): <a href="153521?table=Corr. mtrx $|\eta(l/c-jet_{1})|$ in $≥3b≥1l/c$">Corr. mtrx $|\eta(l/c-jet_{1})|$ in $≥3b≥1l/c$ </a> <li> Data from Table 102 (aux): <a href="153521?table=Corr. mtrx $p_{T}(l/c-jet_{1})$ in $≥3b≥1l/c$">Corr. mtrx $p_{T}(l/c-jet_{1})$ in $≥3b≥1l/c$ </a> <li> Data from Table 103 (aux): <a href="153521?table=Corr. mtrx $H_{T}^{had}$ in $≥4b$">Corr. mtrx $H_{T}^{had}$ in $≥4b$ </a> <li> Data from Table 104 (aux): <a href="153521?table=Corr. mtrx $H_{T}^{all}$ in $≥4b$">Corr. mtrx $H_{T}^{all}$ in $≥4b$ </a> <li> Data from Table 105 (aux): <a href="153521?table=Corr. mtrx $\Delta R_{avg}^{bb}$ in $≥4b$">Corr. mtrx $\Delta R_{avg}^{bb}$ in $≥4b$ </a> <li> Data from Table 106 (aux): <a href="153521?table=Corr. mtrx $\Delta\eta_{max}^{jj}$ in $≥4b$">Corr. mtrx $\Delta\eta_{max}^{jj}$ in $≥4b$ </a> <li> Data from Table 107 (aux): <a href="153521?table=Corr. mtrx $p_{T}(b_{1})$ in $≥4b$">Corr. mtrx $p_{T}(b_{1})$ in $≥4b$ </a> <li> Data from Table 108 (aux): <a href="153521?table=Corr. mtrx $p_{T}(b_{1}^{top})$ in $≥4b$">Corr. mtrx $p_{T}(b_{1}^{top})$ in $≥4b$ </a> <li> Data from Table 109 (aux): <a href="153521?table=Corr. mtrx $p_{T}(b_{2})$ in $≥4b$">Corr. mtrx $p_{T}(b_{2})$ in $≥4b$ </a> <li> Data from Table 110 (aux): <a href="153521?table=Corr. mtrx $p_{T}(b_{2}^{top})$ in $≥4b$">Corr. mtrx $p_{T}(b_{2}^{top})$ in $≥4b$ </a> <li> Data from Table 111 (aux): <a href="153521?table=Corr. mtrx $p_{T}(b_{3})$ in $≥4b$">Corr. mtrx $p_{T}(b_{3})$ in $≥4b$ </a> <li> Data from Table 112 (aux): <a href="153521?table=Corr. mtrx $p_{T}(b_{1}^{add})$ in $≥4b$">Corr. mtrx $p_{T}(b_{1}^{add})$ in $≥4b$ </a> <li> Data from Table 113 (aux): <a href="153521?table=Corr. mtrx $p_{T}(b_{4})$ in $≥4b$">Corr. mtrx $p_{T}(b_{4})$ in $≥4b$ </a> <li> Data from Table 114 (aux): <a href="153521?table=Corr. mtrx $p_{T}(b_{2}^{add})$ in $≥4b$">Corr. mtrx $p_{T}(b_{2}^{add})$ in $≥4b$ </a> <li> Data from Table 115 (aux): <a href="153521?table=Corr. mtrx $|\eta(b_{1})|$ in $≥4b$">Corr. mtrx $|\eta(b_{1})|$ in $≥4b$ </a> <li> Data from Table 116 (aux): <a href="153521?table=Corr. mtrx $|\eta(b_{1}^{top})|$ in $≥4b$">Corr. mtrx $|\eta(b_{1}^{top})|$ in $≥4b$ </a> <li> Data from Table 117 (aux): <a href="153521?table=Corr. mtrx $|\eta(b_{2})|$ in $≥4b$">Corr. mtrx $|\eta(b_{2})|$ in $≥4b$ </a> <li> Data from Table 118 (aux): <a href="153521?table=Corr. mtrx $|\eta(b_{2}^{top})|$ in $≥4b$">Corr. mtrx $|\eta(b_{2}^{top})|$ in $≥4b$ </a> <li> Data from Table 119 (aux): <a href="153521?table=Corr. mtrx $|\eta(b_{3})|$ in $≥4b$">Corr. mtrx $|\eta(b_{3})|$ in $≥4b$ </a> <li> Data from Table 120 (aux): <a href="153521?table=Corr. mtrx $|\eta(b_{1}^{add})|$ in $≥4b$">Corr. mtrx $|\eta(b_{1}^{add})|$ in $≥4b$ </a> <li> Data from Table 121 (aux): <a href="153521?table=Corr. mtrx $|\eta(b_{4})|$ in $≥4b$">Corr. mtrx $|\eta(b_{4})|$ in $≥4b$ </a> <li> Data from Table 122 (aux): <a href="153521?table=Corr. mtrx $|\eta(b_{2}^{add})|$ in $≥4b$">Corr. mtrx $|\eta(b_{2}^{add})|$ in $≥4b$ </a> <li> Data from Table 123 (aux): <a href="153521?table=Corr. mtrx $m(b_{1}b_{2})$ in $≥4b$">Corr. mtrx $m(b_{1}b_{2})$ in $≥4b$ </a> <li> Data from Table 124 (aux): <a href="153521?table=Corr. mtrx $p_{T}(b_{1}b_{2})$ in $≥4b$">Corr. mtrx $p_{T}(b_{1}b_{2})$ in $≥4b$ </a> <li> Data from Table 125 (aux): <a href="153521?table=Corr. mtrx $m(bb^{top})$ in $≥4b$">Corr. mtrx $m(bb^{top})$ in $≥4b$ </a> <li> Data from Table 126 (aux): <a href="153521?table=Corr. mtrx $p_{T}(bb^{top})$ in $≥4b$">Corr. mtrx $p_{T}(bb^{top})$ in $≥4b$ </a> <li> Data from Table 127 (aux): <a href="153521?table=Corr. mtrx $m(e\mu b_{1}b_{2})$ in $≥4b$">Corr. mtrx $m(e\mu b_{1}b_{2})$ in $≥4b$ </a> <li> Data from Table 128 (aux): <a href="153521?table=Corr. mtrx $m(e\mu bb^{top})$ in $≥4b$">Corr. mtrx $m(e\mu bb^{top})$ in $≥4b$ </a> <li> Data from Table 129 (aux): <a href="153521?table=Corr. mtrx $m(bb^{min\Delta R})$ in $≥4b$">Corr. mtrx $m(bb^{min\Delta R})$ in $≥4b$ </a> <li> Data from Table 130 (aux): <a href="153521?table=Corr. mtrx $p_{T}(bb^{min\Delta R})$ in $≥4b$">Corr. mtrx $p_{T}(bb^{min\Delta R})$ in $≥4b$ </a> <li> Data from Table 131 (aux): <a href="153521?table=Corr. mtrx $m(bb^{add})$ in $≥4b$">Corr. mtrx $m(bb^{add})$ in $≥4b$ </a> <li> Data from Table 132 (aux): <a href="153521?table=Corr. mtrx $p_{T}(bb^{add})$ in $≥4b$">Corr. mtrx $p_{T}(bb^{add})$ in $≥4b$ </a> <li> Data from Table 133 (aux): <a href="153521?table=Corr. mtrx min$\Delta R(bb)$ in $≥4b$">Corr. mtrx min$\Delta R(bb)$ in $≥4b$ </a> <li> Data from Table 134 (aux): <a href="153521?table=Corr. mtrx $\Delta R(b_{1}b_{2})$ in $≥4b$">Corr. mtrx $\Delta R(b_{1}b_{2})$ in $≥4b$ </a> <li> Data from Table 135 (aux): <a href="153521?table=Corr. mtrx $N_{l/c-jets}$ in $≥4b$">Corr. mtrx $N_{l/c-jets}$ in $≥4b$ </a> <li> Data from Table 136 (aux): <a href="153521?table=Corr. mtrx $\Delta R(e\mu b_{1}b_{2},b_{3})$ in $≥4b$">Corr. mtrx $\Delta R(e\mu b_{1}b_{2},b_{3})$ in $≥4b$ </a> <li> Data from Table 137 (aux): <a href="153521?table=Corr. mtrx $\Delta R(e\mu bb^{top}, b_{1}^{add})$ in $≥4b$">Corr. mtrx $\Delta R(e\mu bb^{top}, b_{1}^{add})$ in $≥4b$ </a> <li> Data from Table 138 (aux): <a href="153521?table=Corr. mtrx $\Delta R(e\mu bb^{top}, l/c-jet_{1})$ in $≥4b≥1l/c$">Corr. mtrx $\Delta R(e\mu bb^{top}, l/c-jet_{1})$ in $≥4b≥1l/c$ </a> <li> Data from Table 139 (aux): <a href="153521?table=Corr. mtrx $p_{T}(l/c-jet_{1})-p_{T}(b_{1}^{add})$ in $≥4b≥1l/c$">Corr. mtrx $p_{T}(l/c-jet_{1})-p_{T}(b_{1}^{add})$ in $≥4b≥1l/c$ </a> <li> Data from Table 140 (aux): <a href="153521?table=Corr. mtrx $|\eta(l/c-jet_{1})|$ in $≥4b≥1l/c$">Corr. mtrx $|\eta(l/c-jet_{1})|$ in $≥4b≥1l/c$ </a> <li> Data from Table 141 (aux): <a href="153521?table=Corr. mtrx $p_{T}(l/c-jet_{1})$ in $≥4b≥1l/c$">Corr. mtrx $p_{T}(l/c-jet_{1})$ in $≥4b≥1l/c$ </a> </ul><br/>
Measured and predicted fiducial cross-section results for additional b-jet production in four phase-space regions. The dashes (–) indicate that the predictions are not available. The differences between the various MC generator predictions are smaller than the size of theoretical uncertainties (20%–50%, not presented here) in the predictions.
Data bootstraps post unfolding for the normalised differential cross-section in the phase space with at least two $b$-jets as a function of the number of $b$-jets compared with predictions. The replicas are obtained by reweighting each observed data event by a random integer generated according to Poisson statistics, using the BootstrapGenerator software package (https://gitlab.cern.ch/atlas-physics/sm/StandardModelTools_BootstrapGenerator/BootstrapGenerator), which implements a technique described in ATL-PHYS-PUB-2021-011 (https://cds.cern.ch/record/2759945). The ATLAS event number and run number of each event are used as seed to uniquely but reproducibly initialise the random number generator for each event. The last bin contains the overflow.
This paper reports the observation of top-quark pair production in proton-lead collisions in the ATLAS experiment at the Large Hadron Collider. The measurement is performed using 165 nb$^{-1}$ of $p$+Pb data collected at $\sqrt{s_\mathrm{NN}}=8.16$ TeV in 2016. Events are categorised in two analysis channels, consisting of either events with exactly one lepton (electron or muon) and at least four jets, or events with two opposite-charge leptons and at least two jets. In both channels at least one $b$-tagged jet is also required. Top-quark pair production is observed with a significance over five standard deviations in each channel. The top-quark pair production cross-section is measured to be $\sigma_{t\bar{t}}= 58.1\pm 2.0\;\mathrm{(stat.)\;^{+4.8}_{-4.4} \;\mathrm{(syst.)}}\;\mathrm{nb}$, with a total uncertainty of 9%. In addition, the nuclear modification factor is measured to be $R_{p\mathrm{A}} = 1.090\pm0.039\;(\mathrm{stat.})\;^{+0.094}_{-0.087}\;(\mathrm{syst.})$. The measurements are found to be in good agreement with theory predictions involving nuclear parton distribution functions.
The figure shows the pre-fit distribution of events as a function of $H_{\mathrm{T}}^{\ell,j} = \sum_{\ell,j} p_{T}^{\ell,j}$, scalar sum of $p_T$ for all jets and leptons in the $\ell+$jets channel, in proton-lead (p+Pb) collisions at a center-of-mass energy of $\sqrt{s_{\mathrm{NN}}} = 8.16$ TeV, with an integrated luminosity of 165 nb$^{-1}$. The data correspond to the $1\ell 1b$ $e$+jets channel in a pre-fit configuration. The stacked histograms represent different processes contributing to the event yield, including top quark pair production ($t\bar{t}$), single top, $W$ boson production with $b$, $c$, and light quarks, $Z$ boson production with $b$, $c$, and light quarks, diboson, and fake lepton backgrounds.
The figure shows the post-fit distribution of events as a function of $H_{\mathrm{T}}^{\ell,j} = \sum_{\ell,j} p_{T}^{\ell,j}$, scalar sum of $p_T$ for all jets and leptons in the $\ell+$jets channel, in proton-lead (p+Pb) collisions at a center-of-mass energy of $\sqrt{s_{\mathrm{NN}}} = 8.16$ TeV, with an integrated luminosity of 165 nb$^{-1}$. The data correspond to the $1\ell 1b$ $e$+jets channel in a pre-fit configuration. The stacked histograms represent different processes contributing to the event yield, including top quark pair production ($t\bar{t}$), single top, $W$ boson production with $b$, $c$, and light quarks, $Z$ boson production with $b$, $c$, and light quarks, diboson, and fake lepton backgrounds.
The figure shows the pre-fit distribution of events as a function of $H_{\mathrm{T}}^{\ell,j} = \sum_{\ell,j} p_{T}^{\ell,j}$, scalar sum of $p_T$ for all jets and leptons in the $\ell+$jets channel, in proton-lead (p+Pb) collisions at a center-of-mass energy of $\sqrt{s_{\mathrm{NN}}} = 8.16$ TeV, with an integrated luminosity of 165 nb$^{-1}$. The data correspond to the $1\ell 1b$ $\mu$+jets channel in a pre-fit configuration. The stacked histograms represent different processes contributing to the event yield, including top quark pair production ($t\bar{t}$), single top, $W$ boson production with $b$, $c$, and light quarks, $Z$ boson production with $b$, $c$, and light quarks, diboson, and fake lepton backgrounds.
A search for the resonant production of a heavy scalar $X$ decaying into a Higgs boson and a new lighter scalar $S$, through the process $X \to S(\to bb) H(\to \gamma\gamma)$, where the two photons are consistent with the Higgs boson decay, is performed. The search is conducted using an integrated luminosity of 140 fb$^{-1}$ of proton-proton collision data at a centre-of-mass energy of 13 TeV recorded with the ATLAS detector at the Large Hadron Collider. The search is performed over the mass range 170 $\leq$$m_{X}$$\leq$ 1000 GeV and 15 $\leq$$m_{S}$$\leq$ 500 GeV. Parameterised neural networks are used to enhance the signal purity and to achieve continuous sensitivity in a domain of the ($m_{X}$, $m_{S}$) plane. No significant excess above the expected background is found and 95% CL upper limits are set on the cross section times branching ratio, ranging from 39 fb to 0.09 fb. The largest deviation from the background-only expectation occurs for ($m_{X}$, $m_{S}$) = (575, 200) GeV with a local (global) significance of 3.5 (2.0) standard deviations.
Number of events for the 2 b-jet process category obtained from a background-only fit to data in the signal region and sideband. In the signal region the yield in the most signal-like bin of the PNN distribution, parameterised to the signal point mass (mX, mS) = (250, 100) GeV, is also provided. The uncertainties are symmetrised around the central value. The uncertainty in the total background is calculated taking correlations between the individual contributions into account. For the single Higgs boson processes, 'Other' includes the following production modes: VBF, WH, tHq, and tHW.
Number of events for the 1 b-jet process category obtained from a background-only fit to data in the signal region and sideband. In the signal region the yield in the most signal-like bin of the PNN distribution, parameterised to the signal point mass (mX, mS) = (1000, 70) GeV, is also provided. The uncertainties are symmetrised around the central value. The uncertainty in the total background is calculated taking correlations between the individual contributions into account. For the single Higgs boson processes, 'Other' includes the following production modes: VBF, WH, tHq, and tHW.
Expected and observed 95% CL upper limits on the signal cross section times the branching ratio of X → SH → b b $\gamma \gamma$ shown in the (mX, mS) plane, for each evaluated point. The values of the expected limit one and two standard deviations from the nominal value are also shown. The band at mS = 125 GeV is not included as these signal points are equivalent to those already probed in Phys. Rev. D 106 (2022) 052001.
We report a measurement of the $e^+e^- \to \pi^+\pi^-\pi^0$ cross section in the energy range from 0.62 to 3.50 GeV using an initial-state radiation technique. We use an $e^+e^-$ data sample corresponding to 191 $\text{fb}^{-1}$ of integrated luminosity, collected at a center-of-mass energy at or near the $\Upsilon{(4S)}$ resonance with the Belle II detector at the SuperKEKB collider. Signal yields are extracted by fitting the two-photon mass distribution in $e^+e^- \to \pi^+\pi^-\pi^0\gamma$ events, which involve a $\pi^0 \to \gamma\gamma$ decay and an energetic photon radiated from the initial state. Signal efficiency corrections with an accuracy of 1.6% are obtained from several control data samples. The uncertainty on the cross section at the $\omega$ and $\phi$ resonances is dominated by the systematic uncertainty of 2.2%. The resulting cross sections in the 0.62-1.80 GeV energy range yield $ a_\mu^{3\pi} = [48.91 \pm 0.23~(\mathrm{stat}) \pm 1.07~(\mathrm{syst})] \times 10^{-10} $ for the leading-order hadronic vacuum polarization contribution to the muon anomalous magnetic moment. This result differs by $2.5$ standard deviations from the most precise current determination.
Energy bin range ($\sqrt{s'}$), number of events after unfolding ($N_{\mathrm{unf}}$), corrected efficiency ($\varepsilon$), and cross section ($\sigma_{3\pi}$) for $e^{+}e^{-} \to \pi^{+} \pi^{-} \pi^{0}$ in energy range 0.62--1.05~GeV. The two uncertainties in the cross section are the statistical and systematic contributions. The statistical uncertainties for the unfolding and cross section are square roots of the diagonal components of the unfolding covariance matrix. The image shows Figure 23 in the PRD paper, and the points with error bars indicate the cross section in the table.
Energy bin range ($\sqrt{s'}$), number of events after unfolding ($N_{\mathrm{unf}}$), corrected efficiency ($\varepsilon$), and cross section ($\sigma_{3\pi}$) for $e^{+}e^{-} \to \pi^{+} \pi^{-} \pi^{0}$ in energy range 1.05--3.50~GeV. The two uncertainties in the cross section are the statistical and systematic contributions. The statistical uncertainties for the unfolding and cross section are square roots of the diagonal components of the unfolding covariance matrix. The image shows Figure 23 in the PRD paper, and the points with error bars indicate the cross section in the table.
The statistic covariance matrix for the $e^+e^- \to \pi^+ \pi^- \pi^0$ cross section measurement at the Belle II. The 212 x 212 matrix of the energy ranges from 0.62 to 3.50 GeV. This covariance matrix, obtained by propagating the covariance matrix in the unfolding procedure, shows the total statistical uncertainties for the cross section results.
A search is presented for the pair production of higgsinos $\tilde{\chi}$ in gauge-mediated supersymmetry models, where the lightest neutralinos $\tilde{\chi}_1^0$ decay into a light gravitino $\tilde{G}$ in association with either a Higgs $h$ or a $Z$ boson. The search is performed with the ATLAS detector at the Large Hadron Collider using 139 fb$^{-1}$ of proton-proton collisions at a centre-of-mass energy of $\sqrt{s}$ = 13 TeV. It targets final states in which a Higgs boson decays into a photon pair, while the other Higgs or $Z$ boson decays into a $b\bar{b}$ pair, with missing transverse momentum associated with the two gravitinos. Search regions dependent on the amount of missing transverse momentum are defined by the requirements that the diphoton mass should be consistent with the mass of the Higgs boson, and the $b\bar{b}$ mass with the mass of the Higgs or $Z$ boson. The main backgrounds are estimated with data-driven methods using the sidebands of the diphoton mass distribution. No excesses beyond Standard Model expectations are observed and higgsinos with masses up to 320 GeV are excluded, assuming a branching fraction of 100% for $\tilde{\chi}_1^0\rightarrow h\tilde{G}$. This analysis excludes higgsinos with masses of 130 GeV for branching fractions to $h\tilde{G}$ as low as 36%, thus providing complementarity to previous ATLAS searches in final states with multiple leptons or multiple $b$-jets, targeting different decays of the electroweak bosons.
<b>- - - - - - - - Overview of HEPData Record - - - - - - - -</b> <b>Histograms:</b><ul> <li><a href=?table=Distribution1>Figure 3a: $m_{\gamma\gamma}$ Distribution in VR1</a> <li><a href=?table=Distribution2>Figure 3b: $E_{\mathrm{T}}^{\mathrm{miss}}$ Distribution in VR1</a> <li><a href=?table=Distribution3>Figure 3c: $m_{\gamma\gamma}$ Distribution in VR2</a> <li><a href=?table=Distribution4>Figure 3d: $E_{\mathrm{T}}^{\mathrm{miss}}$ Distribution in VR2</a> <li><a href=?table=Distribution5>Figure 4a: N-1 $m_{\gamma\gamma}$ Distribution for SR1h</a> <li><a href=?table=Distribution6>Figure 4b: N-1 $m_{\gamma\gamma}$ Distribution for SR1Z</a> <li><a href=?table=Distribution7>Figure 4c: N-1 $m_{\gamma\gamma}$ Distribution for SR2</a> <li><a href=?table=Distribution8>Auxiliary Figure 1: Signal and Validation Region Yields</a> </ul> <b>Tables:</b><ul> <li><a href=?table=YieldsTable1>Table 3: Signal Region Yields & Model-independent Limits</a> <li><a href=?table=Cutflow1>Auxiliary Table 1: Benchmark Signal Cutflows</a> </ul> <b>Cross section limits:</b><ul> <li><a href=?table=X-sectionU.L.1>Figure 5: 1D Cross-section Limits</a> <li><a href=?table=X-sectionU.L.2>Auxiliary Figure 3: 2D Cross-section Limits</a> </ul> <b>2D CL limits:</b><ul> <li><a href=?table=Exclusioncontour1>Figure 6: Expected Limit on $\mathrm{BF}(\tilde{\chi}_1^0\rightarrow h\tilde{G})$</a> <li><a href=?table=Exclusioncontour2>Figure 6: $+1\sigma$ Variation for Expected Limit on $\mathrm{BF}(\tilde{\chi}_1^0\rightarrow h\tilde{G})$</a> <li><a href=?table=Exclusioncontour3>Figure 6: $-1\sigma$ Variation for Expected Limit on $\mathrm{BF}(\tilde{\chi}_1^0\rightarrow h\tilde{G})$</a> <li><a href=?table=Exclusioncontour4>Figure 6: Observed Limit on $\mathrm{BF}(\tilde{\chi}_1^0\rightarrow h\tilde{G})$</a> <li><a href=?table=Exclusioncontour5>Figure 6: $+1\sigma$ Variation for Observed Limit on $\mathrm{BF}(\tilde{\chi}_1^0\rightarrow h\tilde{G})$</a> <li><a href=?table=Exclusioncontour6>Figure 6: $-1\sigma$ Variation for Observed Limit on $\mathrm{BF}(\tilde{\chi}_1^0\rightarrow h\tilde{G})$</a> </ul> <b>2D Acceptance and Efficiency maps:</b><ul> <li><a href=?table=Acceptance1>Auxiliary Figure 4a: Acceptances SR1h</a> <li><a href=?table=Acceptance2>Auxiliary Figure 4b: Acceptances SR1Z</a> <li><a href=?table=Acceptance3>Auxiliary Figure 4c: Acceptances SR2</a> <li><a href=?table=Efficiency1>Auxiliary Figure 5a: Efficiencies SR1h</a> <li><a href=?table=Efficiency2>Auxiliary Figure 5b: Efficiencies SR1Z</a> <li><a href=?table=Efficiency3>Auxiliary Figure 5c: Efficiencies SR2</a> </ul>
Distribution of the diphoton invariant mass in validation region VR1. The solid histograms are stacked to show the SM expectations after the 2×2D background estimation technique is applied. Background and signal predictions are normalised to the luminosity. The background category "h (other)" includes events originating from VBF, Vh, ggF, thq, thW and bb̄h, all subdominant in this signature. Statistical and systematic uncertainties are indicated by the shaded area. The lower panel of each plot shows the ratio of the data to the SM prediction for the respective bin. The first and last bins include the underflows and overflows respectively.
Distribution of the missing transverse momentum in validation region VR1. The solid histograms are stacked to show the SM expectations after the 2×2D background estimation technique is applied. Background and signal predictions are normalised to the luminosity. The background category "h (other)" includes events originating from VBF, Vh, ggF, thq, thW and bb̄h, all subdominant in this signature. Statistical and systematic uncertainties are indicated by the shaded area. The lower panel of each plot shows the ratio of the data to the SM prediction for the respective bin. The first and last bins include the underflows and overflows respectively.
This paper presents a measurement of the production cross-section of a $Z$ boson in association with $b$- or $c$-jets, in proton-proton collisions at $\sqrt{s} = 13$ TeV with the ATLAS experiment at the Large Hadron Collider using data corresponding to an integrated luminosity of 140 fb$^{-1}$. Inclusive and differential cross-sections are measured for events containing a $Z$ boson decaying into electrons or muons and produced in association with at least one $b$-jet, at least one $c$-jet, or at least two $b$-jets with transverse momentum $p_\textrm{T} > 20$ GeV and rapidity $|y| < 2.5$. Predictions from several Monte Carlo generators based on next-to-leading-order matrix elements interfaced with a parton-shower simulation, with different choices of flavour schemes for initial-state partons, are compared with the measured cross-sections. The results are also compared with novel predictions, based on infrared and collinear safe jet flavour dressing algorithms. Selected $Z + \ge 1 c$-jet observables, optimized for sensitivity to intrinsic-charm, are compared with benchmark models with different intrinsic-charm fractions.
Figure 6(left) of the article. Measured fiducial cross sections for events with $Z (\rightarrow ll) \ge 1 $ b-jets. The thin inner band corresponds to the statistical uncertainty of the data, and the outer band to statistical and systematic uncertainties of the data, added in quadrature.
Figure 6(right) of the article. Measured fiducial cross sections for events with $Z (\rightarrow ll) \ge 2 $ b-jets. The thin inner band corresponds to the statistical uncertainty of the data, and the outer band to statistical and systematic uncertainties of the data, added in quadrature.
Figure 7 of the article. Measured fiducial cross sections for events with $Z (\rightarrow ll) \ge 1 $ c-jets. The thin inner band corresponds to the statistical uncertainty of the data, and the outer band to statistical and systematic uncertainties of the data, added in quadrature.
A search for charged-lepton-flavour violating $\mu\tau qt$ ($q=u,c$) interactions is presented, considering both top-quark production and decay. The data analysed correspond to 140 $\textrm{fb}^{-1}$ of proton-proton collisions at a centre-of-mass energy of $\sqrt{s}= $13 TeV recorded with the ATLAS detector at the Large Hadron Collider. The analysis targets events containing two muons with the same electric charge, a hadronically decaying $\tau$-lepton and at least one jet, with exactly one $b$-tagged jet, produced by a $\mu\tau qt$ interaction. Agreement with the Standard Model expectation within $1.6\sigma$ is observed, and limits are set at the 95% CL on the charged-lepton-flavour violation branching ratio of $\mathcal{B}(t \to \mu\tau q) < 8.7 \times 10^{-7}$. An Effective Field Theory interpretation is performed yielding 95% CL limits on Wilson coefficients, dependent on the flavour of the associated light quark and the Lorentz structure of the coupling. These range from $|c_{\mathsf{lequ}}^{3(2313)}| / \Lambda^{2} < 0.10\textrm{ TeV}^{-2}$ for $\mu\tau ut$ to $|c_{\mathsf{ lequ}}^{1(2323)}| / \Lambda^{2} < 1.8\textrm{ TeV}^{-2}$ for $\mu\tau ct$. An additional interpretation is performed for scalar leptoquark production inducing charged lepton flavour violation, with fixed inter-generational couplings. Upper limits on leptoquark coupling strengths are set at the 95% CL, ranging from $\lambda^{\textrm{LQ}} = $1.3 to $\lambda^{\textrm{LQ}} = $3.7 for leptoquark masses between 0.5 and 2.0 TeV.
Observed event yields in $\textrm{CR}t\bar{t}\mu$ compared with pre-fit expectations from Monte Carlo simulations, as a function of the scalar sum of lepton and jet transverse momenta, $H_{\mathrm{T}}$. The last bin includes overflow events. `Signal (prod.)' and `Signal (dec.)' refer to the single-top-quark production and top-quark pair decay signal contributions, respectively. The pre-fit signal yield represents all Wilson coefficients set to 0.1 simultaneously for a new physics scale of $\Lambda=1$ TeV.
Observed event yields in $\textrm{CR}t\bar{t}\mu$ compared with post-fit expectations from Monte Carlo simulations, as a function of the scalar sum of lepton and jet transverse momenta, $H_{\mathrm{T}}$. The last bin includes overflow events. `Signal (prod.)' and `Signal (dec.)' refer to the single-top-quark production and top-quark pair decay signal contributions, respectively.
Observed event yields in $\textrm{SR}$ compared with pre-fit expectations from Monte Carlo simulations, as a function of the scalar sum of lepton and jet transverse momenta, $H_{\mathrm{T}}$. The last bin includes overflow events. `Signal (prod.)' and `Signal (dec.)' refer to the single-top-quark production and top-quark pair decay signal contributions, respectively. The pre-fit signal yield represents all Wilson coefficients set to 0.1 simultaneously for a new physics scale of $\Lambda=1$ TeV.
The production of single top quarks and top antiquarks via the $t$-channel exchange of a virtual $W$ boson is measured in proton-proton collisions at a centre-of-mass energy of 13 TeV at the LHC using $140\,\mathrm{fb^{-1}}$ of ATLAS data. The total cross-sections are determined to be $\sigma(tq)=137^{+8}_{-8}\,\mathrm{pb}$ and $\sigma(\bar{t}q)=84^{+6}_{-5}\,\mathrm{pb}$ for top-quark and top-antiquark production, respectively. The combined cross-section is found to be $\sigma(tq+\bar{t}q)=221^{+13}_{-13}\,\mathrm{pb}$ and the cross-section ratio is $R_{t}=\sigma(tq)/\sigma(\bar{t}q)=1.636^{+0.036}_{-0.034}$. The predictions at next-to-next-to-leading-order in quantum chromodynamics are in good agreement with these measurements. The predicted value of $R_{t}$ using different sets of parton distribution functions is compared with the measured value, demonstrating the potential to further constrain the functions when using this result in global fits. The measured cross-sections are interpreted in an effective field theory approach, setting limits at the 95% confidence level on the strength of a four-quark operator and an operator coupling the third quark generation to the Higgs boson doublet: $-0.37 < C_{Qq}^{3,1}/\Lambda^2 < 0.06$ and $-0.87 < C_{\phi Q}^{3}/\Lambda^2 < 1.42$. The constraint $|V_{tb}|>0.95$ at the 95% confidence level is derived from the measured value of $\sigma(tq+\bar{t}q)$. In a more general approach, pairs of CKM matrix elements involving top quarks are simultaneously constrained, leading to confidence contours in the corresponding two-dimensional parameter spaces.
The 17 variables used for the training of the NN ordered by their discriminating power. The jet that is not \(b\)-tagged is referred to as the untagged jet. The charged lepton is denoted \(\ell\). The sphericity tensor \(S^{\alpha\beta}\) used to define the sphericity \(S\) is formed with the three-momenta \(\vec{p}_i\) of the reconstructed objects, namely the jets, the charged lepton and the reconstructed neutrino. The tensor is given by \(S^{\alpha\beta}=\frac{\sum_i p_i^\alpha p_i^\beta}{\sum_i |\vec{p}_i|^2}\) where \(\alpha\) and \(\beta\) correspond to the spatial components $x$, $y$ and $z$.
The impact of different groups of systematic uncertainties on the \(\sigma(tq)\) , \(\sigma(\bar t q)\), \(\sigma(tq + \bar t q)\) and \(R_t\), given in %.
The impact of the eight most important systematic uncertainties on the \(\sigma(tq)\) , \(\sigma(\bar t q)\) and \(\sigma(tq + \bar t q)\), given in %. The sequence of the uncertainties is given by the impact on \(\sigma(tq + \bar t q)\)
A search for high-mass resonances decaying into a $\tau$-lepton and a neutrino using proton-proton collisions at a center-of-mass energy of $\sqrt{s}=13$ TeV is presented. The full Run 2 data sample corresponding to an integrated luminosity of 139 fb$^{-1}$ recorded by the ATLAS experiment in the years 2015-2018 is analyzed. The $\tau$-lepton is reconstructed in its hadronic decay modes and the total transverse momentum carried out by neutrinos is inferred from the reconstructed missing transverse momentum. The search for new physics is performed on the transverse mass between the $\tau$-lepton and the missing transverse momentum. No excess of events above the Standard Model expectation is observed and upper exclusion limits are set on the $W^\prime\to \tau \nu$ production cross-section. Heavy $W^\prime$ vector bosons with masses up to 5.0 TeV are excluded at 95% confidence level, assuming that they have the same couplings as the Standard Model $W$ boson. For non-universal couplings, $W^\prime$ bosons are excluded for masses less than 3.5-5.0 TeV, depending on the model parameters. In addition, model-independent limits on the visible cross-section times branching ratio are determined as a function of the lower threshold on the transverse mass of the $\tau$-lepton and missing transverse momentum.
Observed and predicted $m_{\rm T}$ distributions including SSM and NU (cot$\theta$ = 5.5) $W^{\prime}$ signals with masses of 4 TeV. Please note that in the paper figure the bin content is divided by the bin width, but this is not done in the HepData table.
Observed and expected 95% CL upper limits on cross section times $\tau\nu$ branching fraction for $W^{\prime}_{\rm SSM}$.
Regions of the non-universal parameter space excluded at 95% CL.
This Letter presents the first study of the energy-dependence of diboson polarization fractions in $WZ \rightarrow \ell\nu \ell'\ell'~(\ell, \ell'=e, \mu)$ production. The data set used corresponds to an integrated luminosity of 140 fb$^{-1}$ of proton-proton collisions at a center-of-mass energy of 13 TeV recorded by the ATLAS detector. Two fiducial regions with an enhanced presence of events featuring two longitudinally-polarized bosons are defined. A non-zero fraction of events with two longitudinally-polarized bosons is measured with an observed significance of 5.2 standard deviations in the region with $100
Polarization fractions in the region with $100<p_T^Z\leq200$ GeV using three unconstrained parameters.
Polarization fractions in the region with $p_T^Z>200$ GeV using three unconstrained parameters.
Fraction of events where both bosons are longitudinally polarized in the region with $100<p_T^Z\leq200$ GeV using two unconstrained parameters.
Forum