Inclusive b-jet production in pp collisions at $\sqrt {s} = 7TeV$

Abstract

The inclusive b-jet production cross section in pp collisions at a center-ofmass energy of 7 TeV is measured using data collected by the CMS experiment at the LHC. The cross section is presented as a function of the jet transverse momentum in the range 18 < p T < 200 GeV for several rapidity intervals. The results are also given as the ratio of the b-jet production cross section to the inclusive jet production cross section. The measurement is performed with two different analyses, which differ in their trigger selection and b-jet identification: a jet analysis that selects events with a b jet using a sample corresponding to an integrated luminosity of 34 pb −1 , and a muon analysis requiring a b jet with a muon based on an integrated luminosity of 3 pb −1 . In both approaches the b jets are identified by requiring a secondary vertex. The results from the two methods are in agreement with each other and with next-to-leading order calculations, as well as with predictions based on the pythia event generator.

Heavy quark jet fragmentation

“…As an application, we combine the above to study inclusive b-jet production at the LHC, which has been measured by the CMS collaboration [44]. At lowest order, the theoretical prediction is consistently above the measured rate.…”

“…Inclusive b-jet production is a good arena for studying perturbative QCD and probing Standard Model predictions, since hadronic uncertainty should be negligible compared to b-hadron production [43]. Recently the b-jet production rate in pp collision has been measured with a jet radius R = 0.5 [44]. 4 Based on this result, the production in heavy ion collision has been analyzed to examine heavy quark jet quenching [46].…”

“…In order to describe the b-jet production in a straightforward way, we introduce the fragmentation functions to the b-jet (FFbJs), D J b /i (z), where J b represents the b-jet that includes 4 It has been observed that the small R approximation for an inclusive jet process works well even up to R 0.7 [45]. We thus believe that the CMS experiment with R = 0.5 [44] can be legitimately compared with our analysis using the small R approximation, which will be performed in Sec. 5.…”

“…In this section we first discuss the heavy quark mass effects on the FFJs/FFbJs and then apply the formalism to b-jet production, comparing the results with CMS data [44]. In Figure 2 we have compared heavy quark FFJs (D J Q /Q and D J Q /g ) with the massless case.…”

Identification of b-quark jets in the CMS experiment

“…TCHE discriminator • b and c fractions: The fraction of b-flavour jets has been measured in CMS to agree with the simulation within a ±20% uncertainty [46]. A ±20% uncertainty is conservatively estimated for the overall fraction of b and c jets.…”