17 In this section we shall concentrate on semileptonic CP asymmetry ( A$_{SL}$ ) in B$_{s}$ system $^{2}$. In general the CP asymmetry in semileptonic B$_{s}$ decays defined as, depends on the relative phase between the absorptive and dispersive parts of B$_{s}$ − ¯ B$_{s}$ mixing amplitude [77], with φ$_{s}$ = arg ( − M s 12 Γ s 12 ) , the relative phase between B$_{s}$ − ¯ B$_{s}$ mixing and the corresponding b → c ¯ cs decays and | Δ$_{s}$ | parametrises the NP effect in M s 12 [6]. | Γ$_{12}$ /M$_{12}$ | = O ( m 2 $_{b}$/M 2 $_{W}$) suppresses A$_{SL}$ to the percent level, apart from this there is a GIM suppression factor m 2 $_{c}$/m 2 b reducing A$_{SL}$ by another order of magnitude. Because of these suppression factors it is very small in SM, for B$_{s}$ system it is O (10 − $^{5}$). The GIM suppression is lifted if new physics contributes to arg( M$_{12}$ ). Therefore A$_{SL}$ is very sensitive to new CP phases [78, 79]. The situation where new physics could enhance A$_{SL}$ by a factor O (10-100) makes this asymmetry a sensitive probe of new physics. Recently the search for CP violation in semileptonic B$_{s}$ decays achieved a much more improved sensitivity [80, 81]: Present world average is given by [82], In near future more precise measurements can exclude SM prediction if it is much enhanced then the SM prediction. It is important to note that the scenarios like SM4 can significantly A$_{SL}$ = ( − 0 . 37 ± 0 . 94) × 10 − 2 HFAG . (52) A$_{SL}$ = (2 . 45 ± 1 . 96) × 10 − 2 D0 = (2 . 00 ± 2 . 79) × 10 − 2 CDF . (51) A$_{SL}$ = Im ( Γ$_{12}$ M$_{12}$ ) = | Γ s 12 | | M SM 12 |$^{sin}$$^{φ$_{s}$}$ | Δ$_{s}$ | , (50) A$_{SL}$ = Γ[ ¯ B phys s ( t ) → ℓ $^{+}$X ] − Γ[ B phys s ( t ) → ℓ − X ] Γ[ ¯ B phys s ( t ) ℓ $^{+}$X ] + Γ[ B phys s ( t ) ℓ − X ] , (49) B. CP asymmetry in B$_{s}$ → X$_{s}$ℓν 2 We were about to post a short paper reporting our study of A$_{SL}$ in SM4 when the paper [70] appeared wherein this topic is also discussed-consequently we are making a very breif addition of this in version 2 of our paper. Our results agree with Buras et. al [70].