Forward energy flow

A measurement of the energy flow in the forward region ($ 3.15<|\eta|< 4.9$) of the CMS detector at the LHC is presented for centre-of-mass energies, $\sqrt{s}$, of 900 GeV and 7000 GeV. The energy flow, which is corrected for detector effects, is measured in two different event classes: in minimum bias events and in events with a hard scale which is provided by a dijet system at central pseudorapidities ($|\eta| < 2.5$). The jets are required to have transverse energy $E_{T,jet}>8$~GeV at $\sqrt{s}$ of 900 GeV and $E_{T,jet}>20$~GeV at $\sqrt{s}$ of 7000 GeV. The measured forward energy flow is found to differ significantly between the two event classes. The results of the measurements are compared to predictions from various Monte Carlo event generators that were tuned to describe charged particle spectra at central rapidities. In addition, it is observed that predictions by Cosmic Ray Monte Carlo generators describe the forward energy flow very well.