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%                         P H O T O N 9 9
%                          Freiburg
%                       May  23 - 27, 1999
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Abstract \#000, \today
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{\large \bf
Phi Asymmetries in Dijet Production in Deep-inelastic 
Scattering at HERA
\\ }
\vspace{5mm}
M.~Erdmann$^1$
(for the H1 Collaboration)
\\
\vspace{5mm}
{\small\it
(1) University Karlsruhe / DESY, Notkestr. 85, D-22607 Hamburg, Germany
\\
}
\end{center}
The helicity dependent azimuthal asymmetries in (2+1) jet events 
in deep-inelastic scattering at HERA have been measured. 
The data sample has been taken in the
years  1996 -- 1997 and corresponds to an
integrated luminosity of ${\cal L}_{int} \simeq 20\;\mbox{pb}^{-1}$. 
For semi-inclusive measurements of neutral current DIS processes with
unpolarized beams
, the cross-section can be written as a function of 4 structure-functions, 
$d^{5}\sigma=(1+(1-y)^2)\,F_{2}+2(1-y)\,F_{L}-(2-y)\sqrt{1-y}\,F_{4}
\cos\phi^*+2(1-y)\,F_{6}\cos2\phi^*$, where 
$\phi^*$ is defined in the Breit system as the angle between the lepton-plane 
and the hadron-plane.
The ratios $R=F_{L,4,6}/F_{2}$ all go like $k^{2}_{\perp}/Q^2$ for $Q^2>>k^{2}_{\perp}$.
The fact that the intrinsic $p_{\perp}$ of the proton is contributing in a non-trivial manner 
motivated
an exclusive jet measurement to establish the scaling properties 
of the structure-functions and the size and shape of the effects from the intrinsic $p_{\perp}$. 
Systematic effects stemming from QED-radiation on the lepton-side and the 
acceptance of the detector are thoroughly discussed.
The sensitivity to the helicity is checked with a toy-model,where the 
gluons have spin-0.
The effects stemming from the intrinsic $p_{\perp}$ of the proton is incorporated 
in a  Monte-Carlo model and, using this, the intrinsic $p_{\perp}$ in our data is 
estimated to be below $300\,MeV$.
The measurement is in very good agreement with both analytical predictions concerning scaling, 
and a detailed Monte-Carlo integration of leading order QCD.

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