Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Measuring the Tensor Polarization of Positronium   A method for measuring the tensor polarization in a positronium (Ps) beam is
proposed, which is based on the determination of the Ps lifetime as a function
of the orientation of a homogeneous magnetic field. The dependence of the
orthopositronum (o-Ps) lifetime on the angle between the directions of the
magnetic field and the tensor polarization of the Ps beam can be determined
from the results of measurements from two or more field orientations.

28
The categories of this paper are: alg-geom
37
The categories of this paper are: supr-con
20
The categories of this paper are: acc-phys
23
The categories of this paper are: solv-int
2
The categories of this paper are: math
9
The categories of this paper are: nlin
15
The categories of this paper are: nucl-ex
32
The categories of this paper are: atom-ph
19
The categories of this paper are: eess
17
The categories of this paper are: q-fin
25
The categories of this paper are: patt-sol
30
The categories of this paper are: q-alg
34
The categories of this paper are: chem-ph
27
The categories of this paper are: comp-gas
22
The categories of this paper are: chao-dyn
12
The categories of this paper are: nucl-th