We analyse the redshift-space ( z -space ) distortions of QSO clustering in the 2dF QSO Redshift Survey ( 2QZ ) .
To interpret the z -space correlation function , \xi ( \sigma, \pi ) , we require an accurate model for the QSO real-space correlation function , \xi ( r ) .
Although a single power-law \xi ( r ) \propto r ^ { - \gamma } model fits the projected correlation function ( w _ { p } ( \sigma ) ) at small scales , it implies somewhat too shallow a slope for both w _ { p } ( \sigma ) and the z -space correlation function , \xi ( s ) , at larger scales ( \sim > 20 h ^ { -1 } { Mpc } ) .
Motivated by the form for \xi ( r ) seen in the 2dF Galaxy Redshift Survey ( 2dFGRS ) and in standard \Lambda CDM predictions , we use a double power-law model for \xi ( r ) which gives a good fit to \xi ( s ) and w _ { p } ( \sigma ) .
The model is parametrized by a slope of \gamma = 1.45 for 1 < r < 10 h ^ { -1 } Mpc and \gamma = 2.30 for 10 < r < 40 h ^ { -1 } Mpc .
As found for 2dFGRS , the value of \beta determined from the ratio of \xi ( s ) / \xi ( r ) depends sensitively on the form of \xi ( r ) assumed .
With our double power-law form for \xi ( r ) , we measure \beta ( z = 1.4 ) = 0.32 ^ { +0.09 } _ { -0.11 } .
Assuming the same model for \xi ( r ) we then analyse the z -space distortions in the 2QZ \xi ( \sigma, \pi ) and put constraints on the values of \Omega ^ { 0 } _ { m } and \beta ( z = 1.4 ) , using an improved version of the method of Hoyle et al .
The constraints we derive are \Omega _ { m } ^ { 0 } = 0.35 ^ { +0.19 } _ { -0.13 } , \beta ( z = 1.4 ) = 0.50 ^ { +0.13 } _ { -0.15 } , in agreement with our \xi ( s ) / \xi ( r ) results at the \sim 1 \sigma level .