Longitudinal asymmetry and its effect on pseudorapidity distributions in Pb-Pb collisions at sqrt(s_NN) = 2.76 TeV

Submission Date: 
22/10/2017
Article Information
Submission Form
System: 
Pb-Pb
Energy: 
2.76 TeV
Abstract Plain Text: 
First results on the longitudinal asymmetry and its effect on the
pseudorapidity distributions in \PbPb collisions at \snn = 2.76 TeV at
the Large Hadron Collider are obtained with the ALICE detector.
The longitudinal asymmetry arises because of an unequal
  number of participating nucleons from the two colliding nuclei, and is 
  estimated for each event by measuring the energy in the forward
  neutron-Zero-Degree-Calorimeters (ZNs). The effect
  of the longitudinal asymmetry is measured on the pseudorapidity distributions of
  charged particles in the regions $|\eta| < 0.9$,  $2.8 < \eta < 5.1$ and
  $-3.7 < \eta < -1.7 $ by taking the ratio of the pseudorapidity distributions from events
corresponding to different regions of asymmetry.  The coefficients of
a polynomial fit to the ratio characterise the effect of the
asymmetry. A Monte Carlo simulation using a Glauber
  model for the colliding nuclei is
  tuned to reproduce the spectrum in the ZNs and provides 
  a relation between the measurable longitudinal asymmetry and the shift in
  the rapidity ($y_{\mathrm{0}}$) of the participant zone formed by the
  unequal number of participating nucleons.
The dependence of the coefficient of the linear term in the polynomial
expansion, $c_{\rm 1}$, on the mean value of $y_{\mathrm{0}}$ is investigated.