Measurement of the charge asymmetry in highly boosted top-quark pair production in $\sqrt{s} =$ 8 TeV $pp$ collision data collected by the ATLAS experiment

• Published in: Physics letters. B Vol. 756; pp. 52 - 71
• Main Authors: Aad, G., Albrand, S., Berlendis, S., Camincher, C., Collot, J., Crépé-Renaudin, S., Delsart, P.A., Gabaldon, C., Genest, M.H., Hostachy, J.Y., Ledroit-Guillon, F., Lleres, A., Lucotte, A., Malek, F., Petit, E., Stark, J., Trocmé, B., Wu, M., Rahal, G., Alio, L., Barbero, M., Calandri, A., Calvet, T.P., Coadou, Y., Diaconu, C., Diglio, Sara, Djama, F., Ellajosyula, V., Feligioni, L., Gao, J., Hadef, A., Hallewell, G.D., Hubaut, F., Kahn, S.J., Knoops, E. B. F. G., Le Guirriec, E., Liu, J., Liu, K., Madaffari, D., Mochizuki, K., Monnier, E., Muanza, S., Nagai, Y., Nagy, E., Pralavorio, P., Rodina, Y., Rozanov, A., Theveneaux-Pelzer, T., Talby, M., Ticse Torres, R.E., Tiouchichine, E., Tisserant, S., Toth, J., Touchard, F., Vacavant, L., Wang, Chen, Ayoub, M.K., Bassalat, A., Bécot, C., Binet, S., Bourdarios, C., Delgove, D., de Vivie de Regie, J.-B., Duflot, L., Escalier, M., Fayard, L., Fournier, D., Gkougkousis, E.L., Grivaz, J-F., Guillemin, T., Hariri, F., Henrot-Versille, S., Hrivnac, J., Iconomidou-Fayard, L., Kado, M., Lounis, A., Makovec, N., Morange, N., Nellist, C., Petroff, P., Poggioli, L., Puzo, P., Renaud, A., Rousseau, D., Rybkin, G., Schaffer, A.C., Scifo, E., Serin, L., Simion, S., Tanaka, R., Zerwas, D., Zhang, Zhongkai, Zhao, Y., Barnovska, Z., Berger, N., Delmastro, M., Di Ciaccio, L., Elles, S., Goy, C., Hryn’ova, T.
• Format: Journal Article
• Language: English
• Published: Elsevier 2016
• Subjects: High Energy Physics - Experiment; Physics
• ISSN: 0370-2693
• DOI: 10.1016/j.physletb.2016.02.055

In the $pp \rightarrow t\bar{t}$ process the angular distributions of top and anti-top quarks are expected to present a subtle difference, which could be enhanced by processes not included in the Standard Model. This Letter presents a measurement of the charge asymmetry in events where the top-quark pair is produced with a large invariant mass. The analysis is performed on 20.3 fb$^{-1}$ of $pp$ collision data at $\sqrt{s} =$ 8 TeV collected by the ATLAS experiment at the LHC, using reconstruction techniques specifically designed for the decay topology of highly boosted top quarks. The charge asymmetry in a fiducial region with large invariant mass of the top-quark pair ($m_{t\bar{t}} > $ 0.75 TeV) and an absolute rapidity difference of the top and anti-top quark candidates within $-$2 $ < |y_t| - |y_{\bar{t}}| <$ 2 is measured to be 4.2 $\pm$ 3.2%, in agreement with the Standard Model prediction at next-to-leading order. A differential measurement in three $t\bar{t}$ mass bins is also presented.