Abstract
Measurements of transverse energy–energy correlations and their associated asymmetries in multi-jet events using the ATLAS detector at the LHC are presented. The data used correspond to sqrt{s} = 8~hbox {TeV} proton–proton collisions with an integrated luminosity of 20.2~hbox {fb}^{-1}. The results are presented in bins of the scalar sum of the transverse momenta of the two leading jets, unfolded to the particle level and compared to the predictions from Monte Carlo simulations. A comparison with next-to-leading-order perturbative QCD is also performed, showing excellent agreement within the uncertainties. From this comparison, the value of the strong coupling constant is extracted for different energy regimes, thus testing the running of alpha _{mathrm {s}}(mu ) predicted in QCD up to scales over 1~hbox {TeV}. A global fit to the transverse energy–energy correlation distributions yields alpha _{mathrm {s}}(m_Z) = 0.1162 pm 0.0011 text{(exp.) }^{+0.0084}_{-0.0070} text{(theo.) }, while a global fit to the asymmetry distributions yields a value of alpha _{mathrm {s}}(m_Z) = 0.1196 pm 0.0013 text{(exp.) }^{+0.0075}_{-0.0045} text{(theo.) }.
Highlights
ET = E sin θ since the energy alone is not Lorentz-invariant under longitudinal boosts along the beam direction
The next-to-leading-order (NLO) corrections were obtained recently [37] by using the NLOJET++ program [38,39]. They are found to be of moderate size so that the TEEC and ATEEC functions are well suited for precision tests of QCD, including a precise determination of the strong coupling constant αs
The ATLAS Collaboration presented a measurement of the TEEC and ATEEC [41], where these observables were used for a determination of the strong coupling constant αs(m Z ) at an energy regime of Q = 305 GeV
Summary
The ATLAS detector [44] is a multipurpose particle physics detector with a forward-backward symmetric cylindrical geometry and a solid angle coverage of almost 4π. The inner tracking system covers the pseudorapidity range |η| < 2.5 It consists of a silicon pixel detector, a silicon microstrip detector and, for |η| < 2.0, a transition radiation tracker. It is surrounded by a thin superconducting solenoid providing a 2 T magnetic field along the beam direction. A high-granularity liquid-argon sampling electromagnetic calorimeter covers the region |η| < 3.2. It consists of three large air-core superconducting toroid systems and separate trigger and high-precision tracking chambers providing accurate muon tracking for |η| < 2.7. The event filter uses reconstruction algorithms similar to the offline versions with the full detector granularity
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