Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Fragmentation of the $^4$He$_2$ dimer by relativistic highly charged
  projectiles in collisions with small kinetic energy release   We study theoretically the fragmentation of the helium dimer, $^4$He$_2$,
into singly charged ions in collisions with relativistic highly-charged
projectiles. We discuss the main mechanisms driving this process with the focus
on the fragmentation caused by direct ionization of both atomic sites of the
dimer in a single collision with the projectile. This direct mechanism
dominates the He$_2$ $\to $ He$^+$ + He$^+$ breakup events with the kinetic
energies of the emerging ionic fragments below $4$--$5$ eV. We explore the
energy and angular distributions of the He$^+$ ions produced in collisions with
$1$ and $7$ GeV/u U$^{92+}$ projectiles and show that their shape is
significantly affected by relativistic and higher-order effects in the
interaction between the projectile and the dimer. We also show that the shape
of the energy spectrum is quite sensitive to the binding energy of the He$_2$
dimer which can be exploited for its precise determination. The contribution of
the direct mechanism to the total cross section for the He$_2$ fragmentation by
$1$ and $7$ GeV/u U$^{92+}$ was calculated to be $3.65$ Mb and $2.4$ Mb,
respectively, representing roughly half of this cross section.

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The categories of this paper are: acc-phys
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The categories of this paper are: chao-dyn
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The categories of this paper are: supr-con
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The categories of this paper are: cmp-lg
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The categories of this paper are: hep-ex
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The categories of this paper are: atom-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: ao-sci
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The categories of this paper are: q-bio
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The categories of this paper are: hep-th
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The categories of this paper are: nucl-ex
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The categories of this paper are: q-alg
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The categories of this paper are: patt-sol
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The categories of this paper are: math-ph
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The categories of this paper are: eess
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The categories of this paper are: cond-mat