# EPS HEP 2013 Stockholm

17-24 July 2013
KTH and Stockholm University Campus
Europe/Stockholm timezone

## Multi-jet cross section ratios and a determination of the strong coupling constant in ppbar collisions at sqrt(s)=1.96 TeV

18 Jul 2013, 09:30
15m
E1 (KTH Campus)

### E1

#### KTH Campus

Talk presentation QCD

### Speaker

Avtandyl Kharchilava

### Description

We present measurements of three different multi-jet cross section ratios. These include the very first measurements of the new quantities $R_{\DeltaR}$ and $R_{\Delta\phi}$, and a measurement of $R_{3/2}$. The variable $R_{\DeltaR}$ measures the average number of neighboring jets for jets from an inclusive jet sample. The variable $R_{\Delta\phi}$ measures the fraction of the inclusive dijet events in which the azimuthal separation of the two jets with the highest transverse momenta is less than a specified value of the parameter $\Delta\phi_{\rm max}$. The quantity $R_{3/2}$ is the ratio of the inclusive 3-jet and 2-jet cross sections. All three measurements use an event sample corresponding to an integrated luminosity of $0.7\,$fb$^{-1}$ collected with the D0 detector at the Fermilab Tevatron Collider. The results are compared to predictions of perturbative QCD calculations at next-to-leading order in the strong coupling with corrections for non-perturbative effects. In most kinematic regions, the theory predictions describe the data well. The $R_{\Delta R}$ data are used to determine the strong coupling constant over a large range of momentum transfers from 50-400 GeV, testing the predictions of the renormalization group equation for its running in a new range of momentum transfers.

### Primary author

The DØ Collaboration (Fermi National Laboratory)

 Slides