Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: How to test path-length dependence in energy loss mechanisms: analysis
  leading to a new observable   When traversing QCD medium, high $p_\perp$ partons lose energy, which is
typically measured by suppression, and also predicted by various energy loss
models. A crucial test of different energy loss mechanisms is how the energy
loss depends on the length of traversed medium (so-called path-length
dependence). The upcoming experimental results will allow to, at least in
principle, for the first time, clearly observe how the energy loss changes with
the size of the medium, in particular, by comparing already available $Pb+Pb$
measurements with now upcoming $Xe+Xe$ data at the LHC. However, in practice,
to actually perform such test, it becomes crucial to chose an optimal
observable. With respect to this, a ratio of observed suppression for the two
systems may seem a natural (and frequently mentioned) choice. We, however, show
that extracting the path-length dependence from this observable would not be
possible. We here provide an analytical derivation based on simple scaling
arguments, as well as detailed numerical calculations based on our advanced
energy loss framework, showing that a different observable is suitable for this
purpose. We call this observable path-length sensitive suppression ratio
($R_L^{AB}$) and provide our predictions before experimental data become
available. This predictions also clearly show that this observable will allow a
simple comparison of the related theoretical models with the experimental data,
and consequently to distinguish between different (underlying) energy loss
mechanisms, which is in turn crucial for understanding properties of created
QCD medium.

3
The categories of this paper are: physics
31
The categories of this paper are: ao-sci
13
The categories of this paper are: quant-ph
34
The categories of this paper are: chem-ph
23
The categories of this paper are: solv-int
27
The categories of this paper are: comp-gas
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The categories of this paper are: nlin
15
The categories of this paper are: nucl-ex
22
The categories of this paper are: chao-dyn
10
The categories of this paper are: q-bio
33
The categories of this paper are: plasm-ph
28
The categories of this paper are: alg-geom
17
The categories of this paper are: q-fin
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The categories of this paper are: econ
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The categories of this paper are: math-ph
2
The categories of this paper are: math