Multi parton interaction studies in pp and p-Pb

20 May 2014, 16:30
spectrum (darmstadtium)



Board: I-17
Poster Correlations and Fluctuations Poster session


Emilia Leogrande (University of Utrecht (NL))


Two-particle angular correlations between unidentified charged trigger and associated particles are measured by the ALICE detector in pp collisions at a centre of mass energy of $0.9$, $2.76$, $7$ TeV and in p-Pb collisions at a nucleon-nucleon centre of mass energy of $5.02$ TeV. The particle correlations are expressed as an associated yield per trigger particle in the transverse-momentum range $0.7 < p_{\rm T}, assoc < p_{\rm T}, trig < 5.0$ GeV/$c$, to include jets down to the lowest energy (minijets). In p-Pb collisions, long-range near-side correlations, projected onto the azimuthal angle difference, are subtracted from both near- and away-side short-range correlations in order to remove the non-jet-related components, namely the double-ridge. Near- and away-side per trigger yields are studied as a function of the charged particle multiplicity at mid-rapidity. The extracted yields provide information about parton fragmentation at low transverse momenta, as well as about the contribution of multiple parton interactions (MPIs) to particle production. We find that in pp collisions the uncorrelated seeds stagnate at high multiplicity, showing a limit in the number of MPIs. On the contrary, in p-Pb they increase linearly with multiplicity. Further, moving from multiplicity to geometry parameters, we observe the expected scaling of MPIs with Glauber $\rm N_{coll}$ only in the intermediate Glauber $\rm N_{coll}$ region, revealing a bias in the number of hard scatterings when estimated from the Glauber model.
On behalf of collaboration: ALICE

Primary author

Emilia Leogrande (University of Utrecht (NL))

Presentation Materials