Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Spin alignment and violation of the OZI rule in exclusive $\omega$ and
  $\phi$ production in pp collisions   Exclusive production of the isoscalar vector mesons $\omega$ and $\phi$ is
measured with a 190 GeV$/c$ proton beam impinging on a liquid hydrogen target.
Cross section ratios are determined in three intervals of the Feynman variable
$x_{F}$ of the fast proton. A significant violation of the OZI rule is found,
confirming earlier findings. Its kinematic dependence on $x_{F}$ and on the
invariant mass $M_{p\mathrm{V}}$ of the system formed by fast proton
$p_\mathrm{fast}$ and vector meson $V$ is discussed in terms of diffractive
production of $p_\mathrm{fast}V$ resonances in competition with central
production. The measurement of the spin density matrix element $\rho_{00}$ of
the vector mesons in different selected reference frames provides another
handle to distinguish the contributions of these two major reaction types.
Again, dependences of the alignment on $x_{F}$ and on $M_{p\mathrm{V}}$ are
found. Most of the observations can be traced back to the existence of several
excited baryon states contributing to $\omega$ production which are absent in
the case of the $\phi$ meson. Removing the low-mass $M_{p\mathrm{V}}$ resonant
region, the OZI rule is found to be violated by a factor of eight,
independently of $x_\mathrm{F}$.

10
The categories of this paper are: q-bio
1
The categories of this paper are: cs
18
The categories of this paper are: econ
4
The categories of this paper are: cond-mat
9
The categories of this paper are: nlin
14
The categories of this paper are: math-ph
2
The categories of this paper are: math
19
The categories of this paper are: eess
37
The categories of this paper are: supr-con
22
The categories of this paper are: chao-dyn
21
The categories of this paper are: adap-org
7
The categories of this paper are: hep-th
24
The categories of this paper are: dg-ga
35
The categories of this paper are: mtrl-th
5
The categories of this paper are: gr-qc
28
The categories of this paper are: alg-geom