Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Measurement of transverse energy at midrapidity in Pb-Pb collisions at
  $\sqrt{s_{\rm NN}} = 2.76$ TeV   We report the transverse energy ($E_{\mathrm T}$) measured with ALICE at
midrapidity in Pb-Pb collisions at ${\sqrt{s_{\mathrm {NN}}}}$ = 2.76 TeV as a
function of centrality. The transverse energy was measured using identified
single particle tracks. The measurement was cross checked using the
electromagnetic calorimeters and the transverse momentum distributions of
identified particles previously reported by ALICE. The results are compared to
theoretical models as well as to results from other experiments. The mean
$E_{\mathrm T}$ per unit pseudorapidity ($\eta$), $\langle $d$E_{\mathrm
T}/$d$\eta \rangle$, in 0-5% central collisions is 1737 $\pm$ 6(stat.) $\pm$
97(sys.) GeV. We find a similar centrality dependence of the shape of $\langle
$d$E_{\mathrm T}/$d$\eta \rangle$ as a function of the number of participating
nucleons to that seen at lower energies. The growth in $\langle $d$E_{\mathrm
T}/$d$\eta \rangle$ at the LHC ${\sqrt{s_{\mathrm {NN}}}}$ exceeds
extrapolations of low energy data. We observe a nearly linear scaling of
$\langle $d$E_{\mathrm T}/$d$\eta \rangle$ with the number of quark
participants. With the canonical assumption of a 1 fm/$c$ formation time, we
estimate that the energy density in 0-5% central Pb-Pb collisions at
${\sqrt{s_{\mathrm {NN}}}}$ = 2.76 TeV is 12.3 $\pm$ 1.0 GeV/fm$^3$\xspace and
that the energy density at the most central 80 fm$^2$ of the collision is at
least 21.5 $\pm$ 1.7 GeV/fm$^3$. This is roughly 2.3 times that observed in
0-5% central Au-Au collisions at ${\sqrt{s_{\mathrm {NN}}}}$ = 200 GeV.

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The categories of this paper are: q-alg
12
The categories of this paper are: nucl-th
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The categories of this paper are: chem-ph
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The categories of this paper are: nlin
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The categories of this paper are: hep-lat
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The categories of this paper are: solv-int
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The categories of this paper are: q-bio
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The categories of this paper are: math
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The categories of this paper are: eess
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The categories of this paper are: comp-gas
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The categories of this paper are: mtrl-th
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The categories of this paper are: math-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: stat
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The categories of this paper are: gr-qc
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The categories of this paper are: atom-ph