Cambridge Linear Collider Group - Home Page

Steven Green, John Marshall, Mark Thomson

Performance at CLIC

A typical event display in the CLIC_ILD detector, with 60 BX of γγ → hadrons background, with tight cuts applied

A typical event display in the CLIC_ILD detector, with 60 BX of γγ → hadrons background, with background suppression

A typical event display in the CLIC_ILD detector, with 60 BX of γγ → hadrons background, without background suppression

A typical event display in the CLIC_ILD detector, with 60 BX of γγ → hadrons background, without background suppression

The impact of PFO selection cuts on jet energy
                resolution for jets from simulated Z→qq decays.

The impact of different level of background suppression cuts on jet energy resolution for jets from simulated Z→qq decays

CLIC detector.

CLIC detector canvas.

Due to the higher beam energy and the large electric fields at CLIC there are a number of unwanted background particles, which need to be suppressed for detailed physics analyses to take place.

By simulating the effects of such background events it is possible to determine their impact on the physics analyses at CLIC and allows for development of techniques to suppress them so that the interesting interaction buried under the background can be probed.

To test the jet energy resolution in CLIC, we used samples of Z decays to light quarks without any overlaid backgrounds. Jet energies in range 45-1500GeV and jets in barrel region only, |cos(θ)| < 0.7 are considered. With no cuts applied, resolution is better than ~3.7% for all energies considered

Consider W and Z Separation. W samples provided by e+e-→WW→μνqq events in energy range 125-1000GeV. Full GEANT4 simulation, PandoraPFA reconstruction are used and different levels of background are considered.

Additional reconstruction and selection procedures are applied: removal of muon, removal of neutral fragments from background, jet reconstruction (kt algorithm) and jet angular selection cuts.

The di-jet mass distributions obtained from the e+e-→WW→μνqq event samples were then compared with those obtained from e+e-→ZZ→ννqq event samples.

Without background a 2σ separation is maintained for W/Z energies between 125-1000GeV. The separation is reduced to about 1.7σ when 60BX of γγ → hadrons background is included. Tight PFO selection cuts are used for events with background. This is better than what traditional calorimetry could achieve.