Speaker
Ramiro Rolando Debbe Velasco
(Brookhaven National Laboratory (US))
Description
Proton-lead collisions at the LHC provide an opportunity to probe the
physics of the initial state of ultra-relativistic heavy ion
collisions. In particular, they can provide insight on the effect
of an extended nuclear target on the dynamics of soft and hard
scattering processes and subsequent particle production. Charged
particle multiplicity and pseudorapidity distributions are among
the most basic experimental probes of particle production.
The centrality dependence of the charged particle pseudorapidity
distributions, dNch/deta , was measured in p+Pb collisions at a
nucleon-nucleon centre-of-mass energy of sqrt(s_NN) = 5.02 TeV using
the ATLAS detector. Charged particles were reconstructed over |eta| <
2.7 using the ATLAS pixel detector. The proton-lead collision
centrality was characterized by the total transverse energy measured
over the pseudorapidity interval 3.2 < eta < 4.9 in the direction of
the lead beam. The dNch/deta distributions are found to vary strongly
with centrality, with an increasing asymmetry between the proton-going
and Pb-going directions as the collisions become more central. Three
different calculations of the number of participants, Npart, have been
carried out using a standard Glauber model as well as two
Glauber-Gribov extensions. Charged particle multiplicities per
participant pair are found to vary differently with Npart for these
three models, highlighting the importance of the fluctuating nature of
nucleon-nucleon collisions in the modeling of the initial state of
p+Pb collisions.
| On behalf of collaboration: | ATLAS |
|---|
Primary author
Ramiro Rolando Debbe Velasco
(Brookhaven National Laboratory (US))
