Motivation
Events containing an isolated, high transverse energy photon and an identified b jet are interesting to study from the point of view of both QCD and searches for new physics. A measurement of the production cross-section of these events tests some mechanisms of b jet production at the Tevatron. An excess in any photon + b channel could signal the presence of new physics, for example through light stop or techniomega production.Analysis in brief
We obtain a sample of photon + b jet events in data by selecting isolated photons inside |eta|<1.1 with Et>26 GeV, together with a jet containing a positively signed displaced secondary vertex and which has at least 20 GeV Et, and which lies within |eta|<1.5. The jet and photon must be separated by a cone of at least 0.7. We fit the secondary vertex mass in data to determine the b fraction. In order to determine the background from fake photon + b we use preshower detector information to estimate the number of fake photons in our sample, and multiply this by the b fraction we estimate from a representative background data sample. We obtain the number of real photon + b events by subtracting the background contribution from our original fit. By dividing this number by the selection, tagging and trigger efficiencies, and the integrated luminosity of the dataset, we obtain the cross-section.Public results
Figures- Template shapes in colour (gif,
ps) and black and white
(gif,
ps)
- Secondary vertex mass fits to all selected events
(gif,
ps), photon Et 26-28 GeV
(gif,
ps), photon Et 28-31 GeV
(gif,
ps), photon Et 31-35 GeV
(gif,
ps), photon Et 35-43 GeV
(gif,
ps), photon Et 43-70 GeV.
(gif,
ps)
- Differential cross-section results and comparison to LO in colour (gif, ps), and black and white (gif, ps)
Tables (jpg only)
- Results here
Caption: Differential and inclusive cross-sections for photon + b jet production within the kinematic range specified in the table, shown as a function of photon transverse energy. The first error shown is statistical, and the second systematic in each case. Note that the differential cross-section is given by the total cross-section in a photon transverse energy bin, divided by the width of that bin. Concerning the inclusive cross-section forphoton + b jet with photonEt > 26 GeV , the Leading Order Monte Carlo predictions using CTEQ5L PDFs are:33.6 ± 0.3 pb for PYTHIATune A and29.5 ± 0.3 pb for HERWIG.
- Final statistical error table here
Caption: Statistical errors for the photon + b differential and inclusive cross-section measurements. All measurements are in units of pb/GeV, apart from the inclusive cross-section which is in units of pb.
- Final systematic error table here
Caption: Systematic errors for photon + b differential and inclusive cross-section measurements. All measurements are in units of pb/GeV, apart from the inclusive cross-section which is in units of pb.
