Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The design of the ILD forward region   Following the decision to reduce the L* from 4.4 m to 4.1 m, the BeamCal had
to be moved closer to the interaction point. Results of a study of how this
affects the beamstrahlung and backward scattering backgrounds show that the
e+e- pair background depositions from beamstrahlung at the BeamCal rises by
20%. The background from backscattered electrons and positrons in the inner
pixel layers rises almost by a factor two, so does the number of photons in the
tracker.

19
The categories of this paper are: eess
27
The categories of this paper are: comp-gas
22
The categories of this paper are: chao-dyn
6
The categories of this paper are: astro-ph
24
The categories of this paper are: dg-ga
31
The categories of this paper are: ao-sci
36
The categories of this paper are: cmp-lg
15
The categories of this paper are: nucl-ex
28
The categories of this paper are: alg-geom
34
The categories of this paper are: chem-ph
5
The categories of this paper are: gr-qc
11
The categories of this paper are: hep-lat
9
The categories of this paper are: nlin
17
The categories of this paper are: q-fin
12
The categories of this paper are: nucl-th
2
The categories of this paper are: math