We present a measurement of the ratio of the Bs meson lifetime, in the flavorspecific decay to $D_s^+\pi^$, to that of the B0 meson. The pp collision data used correspond to an integrated luminosity of 1/fb, collected with the LHCb detector, at a centerofmass energy of 7 TeV. Combining our measured value of 1.010 +/ 0.010 +/ 0.008 for this ratio with the known lifetime, we determine the flavorspecific Bs lifetime to be tau(Bs) = 1.535 +/ 0.015 +/ 0.014 ps, where the uncertainties are statistical and systematic, respectively. This is the most precise measurement to date, and is consistent with previous measurements and theoretical predictions.
Fits to the invariant mass spectra of candidates for the decays (a) ${B^}\rightarrow{D^0[K\pi]\pi^}$, (b) ${B^}\rightarrow{D^0[K\pi\pi\pi]\pi^}$, (c) ${\overline{ B }{} ^0 }\rightarrow{D^+[K\pi\pi]\pi^}$, (d) ${\overline{ B }{} ^0_ s }\rightarrow{D^+_s[KK\pi]\pi^}$. The points are the data and the superimposed curves show the fit components. The solid (blue) curve gives the total. The $DK^$ component is not visible, but is included. 
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Decay time distributions for ${B^}\rightarrow{D^0[K\pi]\pi^}$ shown as triangles (blue), ${B^}\rightarrow{D^0[K\pi\pi\pi]\pi^}$ shown as inverted triangles (cyan), ${B^0}\rightarrow{D^+[K\pi\pi]\pi^}$ shown as squares (red), ${\overline{ B }{} ^0_ s }\rightarrow{D^+_s[KK\pi]\pi^}$ shown as circles (magenta). For most entries the error bars are smaller than the point markers. 
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Ratio of the decay time acceptances between ${\overline{ B }{} ^0_ s }\rightarrow{D^+_s[KK\pi]\pi^}$ and ${B^}\rightarrow{D^0[K\pi]\pi^}$ shown as triangles (blue), ${B^0}\rightarrow{D^+[K\pi\pi]\pi^}$ shown as squares (red), and ${B^}\rightarrow{D^0[K\pi\pi\pi]\pi^}$ shown as inverted triangles (cyan). The vertical axis is shown in an arbitrary scale, different for each mode ratio to improve clarity. 
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Efficiencycorrected yield ratios of ${\overline{ B }{} ^0_ s }\rightarrow{D^+_s[KK\pi]\pi^}$ relative to ${B^}\rightarrow{D^0[K\pi]\pi^}$ shown as triangles (blue), ${\overline{ B }{} ^0 }\rightarrow{D^+[K\pi\pi]\pi^}$ shown as squares (red), and ${B^}\rightarrow{D^0[K\pi\pi\pi]\pi^}$ shown as inverted triangles (cyan). The simulation uncertainties are not included. The exponential fits are also shown. The vertical axis is shown in an arbitrary scale, different for each case to improve clarity. 
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Animated gif made out of all figures. 
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Measured lifetime ratios, compared with the known values, and the difference (fitted  known), as well as the resulting measured lifetime $\tau_{\rm meas}$. Errors are statistical only. $B_x$ and $B_y$ indicate the modes used. 
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Systematic uncertainties for $\Delta_{\overline{ B }{} ^0_ s B_x}$. 
Table_2.pdf [45 KiB] HiDef png [28 KiB] Thumbnail [10 KiB] tex code 
Created on 06 March 2021.