Measurement of the single top t-channel cross section in pp collisions at sqrt(s)=7 TeV

%The cross section of $t$-channel single-top production is already measured in pp collision at $\sqrt{s}=7$ TeV with the CMS detector at the LHC %using data collected in 2010 considering the leptonic decay channels with a muon or an electron in the final state. Data collected in 2011 is used %to measure this production cross section with reduced uncertainties compared to 2010 measurement. This note describes the measurement of the single top $t$-channel production cross section in pp collisions at 7 TeV with the CMS detector at the LHC with 2011 data considering the leptonic decay channel with a muon or an electron in the final state. This measurement significantly reduces the uncertainty with respect to the previous result with 2010 data, as it makes use of considerably larger data samples and exploits the improved knowledge of the detector. After a selection optimized for the $t$-channel production, the pseudorapidity distribution of the recoil jet and the reconstructed top quark mass are exploited for the measurement. The background in the selected sample is mainly estimated with data driven techniques. With an integrated luminosity of \lumiMuFB~fb$^{-1}$ (\lumiEleFB~fb$^{-1}$) for the muon (electron) channel the combined (muon and electron) cross section is $\xseccor \pm \xsectotstatcor\mathrm{(stat.)} \pm \xsecsystupcor \mathrm{(syst.)} \pm \xseclumi \mathrm{(lumi.)}\,\mathrm{pb}$ which is in agreement with the next-to-next leading order standard model prediction. The absolute value of CKM matrix element $V_{\mathrm{tb}}$ is also measured at the 10\% level. % under the assumption that. %, aimproving the previous result obtained by CMS. %which is a substantial improvement compared to so far the published results from %experiments at Tevatron and LHC. %%we measure Vtb (with some assumptions) at the 10% (9.2%) level, which is a substantial improvement compared to the published results from %%Tevatron and LHC. %The cross section of $t$-channel single-top production is measured in pp collision at $\sqrt{s}=7$ TeV with the CMS detector at the LHC. Leptonic %decay channels with a muon or an electron in the final state are considered. After a selection optimized for the $t$-channel, the %pseudodorapidity distribution of the recoil jet and the reconstructed top quark mass are exploited for the measurement. The background in the %selected sample is largely estimated with data. With an integrated luminosity of \lumiMuFB~fb$^{-1}$ (\lumiEleFB~fb$^{-1}$) for the muon %(electron) channel the combined (muon and electron) cross section is \xseccor $\pm$ \xsectotstatcor (stat) $\pm$ \xsecsystupcor (syst) $\pm$ %\xseclumi (lumi) ~pb. %This paper describes the measurement of the cross section of single top quark production in the $t$ channel in pp collision data at $\sqrt{s}=7$ %TeV, recorded at LHC with the CMS detector. Leptonic decay channels with a muon or an electron in the final state are considered. After a %selection optimized for the $t$ channel, analysis exploiting the psuedorapidity distribution of the recoil jet and reconstructed top quark mass %with data-driven background estimates is performed. With an integrated luminosity of 1299~pb$^{-1}$ (920~pb$^{-1}$) for the muon (electron) %channel we measure the combined (muon and electron) cross section $70.3 \pm 6.15$(stat.)$\pm 9.61$(syst.)$\pm 3.36$(lumi.)~pb.