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Measurement of the angular coefficients in Z-boson events using electron and muon pairs from data taken at √ s = 8 TeV with the ATLAS detectorThe ATLAS collaboration E-mail: atlas.publications@cern.ch Abstract:The angular distributions of Drell-Yan charged lepton pairs in the vicinity of the Z-boson mass peak probe the underlying QCD dynamics of Z-boson production. This paper presents a measurement of the complete set of angular coefficients A 0−7 describing these distributions in the Z-boson Collins-Soper frame. The data analysed correspond to 20.3 fb −1 of pp collisions at √ s = 8 TeV, collected by the ATLAS detector at the CERN LHC. The measurements are compared to the most precise fixed-order calculations currently available (O(α 2 s )) and with theoretical predictions embedded in Monte Carlo generators. The measurements are precise enough to probe QCD corrections beyond the formal accuracy of these calculations and to provide discrimination between different parton-shower models. A significant deviation from the O(α 2 s ) predictions is observed for A 0 − A 2 . Evidence is found for non-zero A 5,6,7 , consistent with expectations. Keywords: Hadron-Hadron scattering (experiments)ArXiv ePrint: 1606.00689Open Access, Copyright CERN, for the benefit of the ATLAS Collaboration. Article funded by SCOAP 3 .doi:10.1007/JHEP08(2016)159 JHEP08(2016)159 JHEP08(2016)159E Quantifying A 5,6,7 58 F Additional results 61The ATLAS collaboration 83 IntroductionThe angular distributions of charged lepton pairs produced in hadron-hadron collisions via the Drell-Yan neutral current process provide a portal to precise measurements of the production dynamics through spin correlation effects between the initial-state partons and the final-state leptons mediated by a spin-1 intermediate state, predominantly the Z boson.In the Z-boson rest frame, a plane spanned by the directions of the incoming protons can be defined, e.g. using the Collins-Soper (CS) reference frame [1]. The lepton polar and azimuthal angular variables, denoted by cos θ and φ in the following formalism, are defined in this reference frame. The spin correlations are described by a set of nine helicity density matrix elements, which can be calculated within the context of the parton model using perturbative quantum chromodynamics (QCD). The theoretical formalism is elaborated in refs. [2][3][4][5].The full five-dimensional differential cross-section describing the kinematics of the two Born-level leptons from the Z-boson decay can be decomposed as a sum of nine harmonic polynomials, which depend on cos θ and φ, multiplied by corresponding helicity cross-sections that depend on the Z-boson transverse momentum (p Z T ), rapidity (y Z ), and invariant mass (m Z ). It is a standard convention to factorise out the unpolarised crosssection, denoted in the literature by σ U +L , and to present the five-dimensional differential cross-section as an expansion into nine harmonic polynomials P i (cos θ, φ) and dimensionless angular coefficients A 0−7 (p Z T , y Z , m Z ), whic...

The production and decay of 272 111 has been investigated using a gas-filled recoil ion separator in irradiations of 209 Bi targets with 64 Ni beam at 320, 323 and 326 MeV. We have observed 14 -decay chains in total, that can be assigned, on the basis of their time correlations, to subsequent decays from 272 111 produced in the 209 Bi( 64 Ni,1n) reaction. The present result is the first clear confirmation for the discovery of 272 111 and its -decay products, 264 Bh and 268 Mt, reported previously by a GSI group. New information on their half-lives and decay energies as well as the excitation function is presented.

This paper presents measurements of distributions of charged particles which are produced in proton–proton collisions at a centre-of-mass energy of and recorded by the ATLAS detector at the LHC. A special dataset recorded in 2012 with a small number of interactions per beam crossing (below 0.004) and corresponding to an integrated luminosity of 160  was used. A minimum-bias trigger was utilised to select a data sample of more than 9 million collision events. The multiplicity, pseudorapidity, and transverse momentum distributions of charged particles are shown in different regions of kinematics and charged-particle multiplicity, including measurements of final states at high multiplicity. The results are corrected for detector effects and are compared to the predictions of various Monte Carlo event generator models which simulate the full hadronic final state.

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