Underlying Event measurements in pp collisions at $ \sqrt {s} = 0.9 $ and 7 TeV with the ALICE experiment at the LHC

Media type: E-Article

Title: Underlying Event measurements in pp collisions at $ \sqrt {s} = 0.9 $ and 7 TeV with the ALICE experiment at the LHC

Contributor: Abelev, Betty; Quintana, Arian Abrahantes; Adamova, Dagmar; Adare, Andrew Marshall; Aggarwal, Madan; Rinella, Gianluca Aglieri; Agocs, Andras Gabor; Agostinelli, Andrea; Salazar, Saul Aguilar; Ahammed, Zubayer; Ahmad, Nazeer; Ahmad, Arshad; Ahn, Sang Un; Akindinov, Alexander; Aleksandrov, Dmitry; Alessandro, Bruno; Molina, Jose Ruben Alfaro; Alici, Andrea; Alkin, Anton; Avina, Erick Jonathan Almaraz; Alt, Torsten; Altini, Valerio; Altinpinar, Sedat; Altsybeev, Igor; [...]

Published: Springer Science and Business Media LLC, 2012

Language: English

DOI: 10.1007/jhep07(2012)116

ISSN: 1029-8479

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Description: Abstract We present measurements of Underlying Event observables in pp collisions at $ \sqrt {s} = 0.9 $ and 7TeV. The analysis is performed as a function of the highest charged-particle transverse momentum p T,LT in the event. Different regions are defined with respect to the azimuthal direction of the leading (highest transverse momentum) track: Toward, Transverse and Away. The Toward and Away regions collect the fragmentation products of the hardest partonic interaction. The Transverse region is expected to be most sensitive to the Underlying Event activity. The study is performed with charged particles above three different p T thresholds: 0.15, 0.5 and 1.0 GeV/c. In the Transverse region we observe an increase in the multiplicity of a factor 2–3 between the lower and higher collision energies, depending on the track p T threshold considered. Data are compared to Pythia 6.4, Pythia 8.1 and Phojet. On average, all models considered underestimate the multiplicity and summed p T in the Transverse region by about 10–30%.

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