First measurement of the charge asymmetry in beauty-quark pair production

The preprint is available here.

arXiv: 1406.4789

More detailed information: ANA note 2014-010

Abstract

The difference in the angular distributions between beauty quarks and antiquarks, referred to as the charge asymmetry, is measured for the first time in bb pair production at a hadron collider. The data used correspond to an integrated luminosity of 1.0 fb−1 collected at 7 TeV center-of-mass energy in proton-proton collisions with the LHCb detector. The measurement is performed in three regions of the invariant mass of the bb system. The results obtained are AbbbarCb (40 < Mbbbar < 75 GeV/c2 ) = 0.4 0.4 (stat) 0.3 (syst)%, AbbbarCb (75 < M bbbar< 105 GeV/c2 ) = 2.0 0.9 (stat) 0.6 (syst)%, AbbbarCb (M bbbar> 105 GeV/c2 ) = 1.6 1.7 (stat) 0.6 (syst)%, where AbbbarCb is defined as the asymmetry in the difference in rapidity between jets formed from the beauty quark and antiquark. The beauty jets are required to satisfy 2 < η < 4, ET > 20 GeV, and have an opening angle in the transverse plane ∆φ > 2.6 rad. These measurements are consistent with the predictions of the Standard Model.

Figures

(Note, pdf versions are available under attachments).
Caption Figure
Figure 1: (top) Corrected mass of TOPO objects associated to bTAG jets in the final event sample. Less than 2% of jets are found originate from charm. (bottom) Corrected mass of TOPO objects associated to sub-leading vs leading jets in the final event sample. A small ccbar contribution is visible near (2,2) GeV/c2 . Fig1a.png Fig1b.png
Figure 2: Reconstructed ∆y distribution for all selected events after background subtraction and correction for qTAG impurity. The dashed line shows the mirror image distribution. Fig2.png
Figure 3: Migration matrix in ∆y and Mbbbar Fig3.png
Figure 4: Corrected ∆y distribution for all selected events. The statistical uncertainties are negligible. The systematic uncertainties are highly correlated from bin to bin and largely cancel in the determination of AbbbarC . The LO SM prediction obtained from Pythia [36] is also shown. Fig4.png

-- KatharinaMueller - 19 Jun 2014

Topic attachments
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PDFpdf Fig1a.pdf r1 manage 107.6 K 2014-06-19 - 11:00 KatharinaMueller  
PNGpng Fig1a.png r1 manage 37.4 K 2014-06-19 - 11:00 KatharinaMueller  
PDFpdf Fig1b.pdf r1 manage 23.3 K 2014-06-19 - 11:00 KatharinaMueller  
PNGpng Fig1b.png r1 manage 42.3 K 2014-06-19 - 11:00 KatharinaMueller  
PDFpdf Fig2.pdf r1 manage 13.5 K 2014-06-19 - 11:00 KatharinaMueller  
PNGpng Fig2.png r1 manage 11.3 K 2014-06-19 - 11:00 KatharinaMueller  
PDFpdf Fig3.pdf r1 manage 46.3 K 2014-06-19 - 11:00 KatharinaMueller  
PNGpng Fig3.png r1 manage 42.0 K 2014-06-19 - 11:00 KatharinaMueller  
PDFpdf Fig4.pdf r1 manage 13.3 K 2014-06-19 - 11:01 KatharinaMueller  
PNGpng Fig4.png r1 manage 17.8 K 2014-06-19 - 11:01 KatharinaMueller  
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