CDF Logo Measurement of the b-jet Cross section in events with a Z Boson CDF Logo
We describe a new preliminary measurement of the b-jet cross section in events with a Z boson by the CDF collaboration using an integrated luminosity of 1.5 fb-1. The jets must have a transverse energy ET > 20 GeV and pseudorapidity |eta| < 1.5. Jets are measured with a cone algorithm with cone size 0.7. Events are selected for the decay channels Z -> ee and Z -> mumu. Jets containing a $b$ hadron are indentified by reconstructing a secondary vertex. The data are unfolded to the hadron level and compared to predictions from PYTHIA and NLO QCD. This is an update of a previously published measurement with 5 times more data.


Results:

The measurement is the b-jet cross section and is defined to be proportional to the number of b-jets. The result is given in this table:

Here it is also as eps file.
The correction factors quoted are to account for the corrections due to the underlying event (UE) and the hadronisation. The theoretical calculation was made using MCFM, CTEQ6M for the parton density unctions and MZ+pT2 for the factorisation and renormalisation scales. The uncertainty on this prediction due to higher orders and parton distribution functions is about 15%.

Method:

The measurement is made by counting the number of jets with a secondary vertex and evaluating the fraction of b-jets among those by fitting the invariant mass of tracks at this secondary vertex. Only jets with p_T > 20 GeV and |eta| < 1.5 are considered. Pythia is used for unfolding this measurement to the hadron level. The details are described ib the previous publication.

Plots and Tables:


Dilepton invariant mass for events with a tagged b-jet:
EPS or GIF

Invariant mass of the tracks at the secondary vertex:
EPS or GIF

Pseudorapidity of the tagged b-jet:
EPS or GIF

Transverse Momentum of the tagged b-jet:
EPS or GIF
Here is the Table of systematic uncertainties