Pseudorapidity distributions of charged particles in pp collisions at √s = 7 TeV and 0.9 TeV with at least one central charged particle

CMS-PAS-QCD-10-024 in CDS

Abstract

We present a measurements of the charged particle pseudorapidity density distributions in proton-proton collisions at √s = 7 TeV and 0.9 TeV, for particles with a transverse momentum above 0.5 and 1.0 GeV/c and pseudorapidity |η| < 2.4. Only events with at least one charged particle in the kinematic range of |η| < 0.8 or 2.4 are used in the analysis. The measured pseudorapidity distributions using these selections should correspond to inclusive-inelastic distributions, that can be used reliably to improve physics generators of minimum bias events. The data were collected with a minimum-bias trigger during the 2010 Large Hadron Collider (LHC) commissioning period. The events are reconstructed using the inner tracking system of the Compact Muons Solenoid (CMS) detector.

Results for √s=7 TeV

pT > 0.5 GeV particles	pT > 1 GeV particles	description
		Measurement of the normalized charged particle pseudorapidity density distribution, at 7 TeV. Require at least one central track, \η\ < 0.8, and pT > 0.5 GeV/c (left) or > 1 Gev/c (right) -- Nev. Consider only particles with pT > 0.5 GeV/c (left) or > 1 Gev/c (right) in the distributions.
		Measurement of the normalized charged particle pseudorapidity density distribution, at 7 TeV. Require at least one track in \η\ < 2.4 and pT > 0.5 GeV/c (left) or > 1 Gev/c (right) -- Nev. Consider only particles with pT > 0.5 GeV/c (left) or > 1 Gev/c (right) in the distributions.

Results for √s=0.9 TeV

pT > 0.5 GeV particles	pT > 1 GeV particles	description
		Measurement of the normalized charged particle pseudorapidity density distribution, at 0.9 TeV. Require at least one central track, \η\ < 0.8, and pT > 0.5 GeV/c (left) or > 1 Gev/c (right) -- Nev. Consider only particles with pT > 0.5 GeV/c (left) or > 1 Gev/c (right) in the distributions.
		Measurement of the normalized charged particle pseudorapidity density distribution, at 0.9 TeV. Require at least one track in \η\ < 0.8 and pT > 0.5 GeV/c (left) or > 1 Gev/c (right) -- Nev. Consider only particles with pT > 0.5 GeV/c (left) or > 1 Gev/c (right) in the distributions.

See also

• MB & UE WG common plots - Minimum Bias and Underlying Event Working Group page. CMS, Atlas and Alice results combined. Some plots below:

pT > 0.5 GeV particles	pT > 1 GeV particles	description
		Combined results from CMS, Atlas and Alice for 7 TeV. pT > 0.5 GeV/c (left) and pT > 1 Gev/c (right). Note: only central region, \η\<0.8 is shown.
		Combined results from CMS, Atlas and Alice for 0.9 TeV. pT > 0.5 GeV/c (left) and pT > 1 Gev/c (right). Note: only central region, \η\<0.8 is shown.

For CERN users.

• The root files with the numbers for this analysis are located here:

/afs/cern.ch/user/a/andrey/public/dndeta/update

There are two root files, for 7TeV and 0.9TeV. The TGraphs are stored there together with plot.C macro that helps to print out the numbers.

A note on pythia 8 tune.

-- AndreyPozdnyakov - 28-Apr-2011