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

doi:10.1016/j.physletb.2016.02.055

Physics Letters B

Volume 756, 10 May 2016, Pages 52-71

https://doi.org/10.1016/j.physletb.2016.02.055 Get rights and content

Under a Creative Commons license

open access

Abstract

In the $p p \to t \bar{t}$ 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.

Cited by (0)

^ap: Also affiliated with PKU-CHEP.

^a: Also at Department of Physics, King's College London, London, United Kingdom.

^b: Also at Institute of Physics, Azerbaijan Academy of Sciences, Baku, Azerbaijan.

^c: Also at Novosibirsk State University, Novosibirsk, Russia.

^d: Also at TRIUMF, Vancouver, BC, Canada.

^e: Also at Department of Physics & Astronomy, University of Louisville, Louisville, KY, United States of America.

^f: Also at Department of Physics, California State University, Fresno, CA, United States.

^g: Also at Department of Physics, University of Fribourg, Fribourg, Switzerland.

^h: Also at Departament de Fisica de la Universitat Autonoma de Barcelona, Barcelona, Spain.

ⁱ: Also at Departamento de Fisica e Astronomia, Faculdade de Ciencias, Universidade do Porto, Portugal.

^j: Also at Tomsk State University, Tomsk, Russia.

^k: Also at Universita di Napoli Parthenope, Napoli, Italy.

^l: Also at Institute of Particle Physics (IPP), Canada.

^m: Also at Department of Physics, St. Petersburg State Polytechnical University, St. Petersburg, Russia.

ⁿ: Also at Department of Physics, The University of Michigan, Ann Arbor, MI, United States.

^o: Also at Louisiana Tech University, Ruston, LA, United States.

^p: Also at Institucio Catalana de Recerca i Estudis Avancats, ICREA, Barcelona, Spain.

^q: Also at Graduate School of Science, Osaka University, Osaka, Japan.

^r: Also at Department of Physics, National Tsing Hua University, Taiwan.

^s: Also at Department of Physics, The University of Texas at Austin, Austin, TX, United States.

^t: Also at Institute of Theoretical Physics, Ilia State University, Tbilisi, Georgia.

^u: Also at CERN, Geneva, Switzerland.

^v: Also at Georgian Technical University (GTU), Tbilisi, Georgia.

^w: Also at Ochadai Academic Production, Ochanomizu University, Tokyo, Japan.

^x: Also at Manhattan College, New York, NY, United States.

^y: Also at Hellenic Open University, Patras, Greece.

^z: Also at Institute of Physics, Academia Sinica, Taipei, Taiwan.

^aa: Also at Academia Sinica Grid Computing, Institute of Physics, Academia Sinica, Taipei, Taiwan.

^ab: Also at School of Physics, Shandong University, Shandong, China.

^ac: Also at Moscow Institute of Physics and Technology State University, Dolgoprudny, Russia.

^ad: Also at Section de Physique, Université de Genève, Geneva, Switzerland.

^ae: Also at International School for Advanced Studies (SISSA), Trieste, Italy.

^af: Also at Department of Physics and Astronomy, University of South Carolina, Columbia, SC, United States.

^ag: Also at School of Physics and Engineering, Sun Yat-sen University, Guangzhou, China.

^ah: Also at Institute for Nuclear Research and Nuclear Energy (INRNE) of the Bulgarian Academy of Sciences, Sofia, Bulgaria.

^ai: Also at Faculty of Physics, M.V. Lomonosov Moscow State University, Moscow, Russia.

^aj: Also at National Research Nuclear University MEPhI, Moscow, Russia.

^ak: Also at Department of Physics, Stanford University, Stanford, CA, United States.

^al: Also at Institute for Particle and Nuclear Physics, Wigner Research Centre for Physics, Budapest, Hungary.

^am: Also at Flensburg University of Applied Sciences, Flensburg, Germany.

^an: Also at University of Malaya, Department of Physics, Kuala Lumpur, Malaysia.

^ao: Also at CPPM, Aix-Marseille Université and CNRS/IN2P3, Marseille, France.

^⁎: Deceased.

^⋆: E-mail address: [email protected].