Non-perturbative QCD effects in jets at hadron colliders

Abstract: We discuss non-perturbative QCD contributions to jet observables, computing their dependence on the jet radius R, and on the colour and transverse momentum of the parton initiating the jet. We show, using analytic QCD models of power corrections as well as Monte Carlo simulations, that hadronisation corrections grow at small values of R, behaving as 1/R, while underlying event contributions grow with the jet area as R^2. We highlight the connection between hadronisation corrections to jets and those for event shapes in e^+e^- and DIS; we note the limited dependence of our results on the choice of jet algorithm; finally, we propose several measurements in the context of which to test or implement our predictions. The results presented here reinforce the motivation for the use of a range of R values, as well as a plurality of infrared-safe jet algorithms, in precision jet studies at hadron colliders.

• The paper demonstrates that hadronisation corrections scale as 1/R while underlying event contributions grow as R².
• It combines analytical power correction models with Monte Carlo simulations to validate non-perturbative QCD effects.
• Implications for jet energy scale underscore the need for diverse jet algorithms and R values in precision collider studies.

Non-perturbative QCD Effects in Jets at Hadron Colliders

The paper "Non-perturbative QCD effects in jets at hadron colliders" by Dasgupta, Magnea, and Salam presents an analytical and computational study of non-perturbative Quantum Chromodynamics (QCD) contributions to jet observables. The study focuses particularly on the dependence of these contributions on the jet radius $R$ and on the properties of the initiating parton, such as its color and transverse momentum. Using models of power corrections in QCD and Monte Carlo simulations, the authors explain how hadronisation corrections and underlying event contributions behave with respect to $R$.

For small $R$ values, hadronisation corrections scale as $1/R$, marking a significant enhancement in non-perturbative effects. Conversely, underlying event contributions grow with the jet area, behaving as $R^2$. The findings are consistent across various infrared-safe jet algorithms, affirming their reliability while allowing for different $R$ values to optimize precision in QCD studies.

Analyzing the implications, the study suggests that non-perturbative effects, particularly hadronisation, can impact the jet energy scale significantly. This impact might even be comparable to higher-order perturbative effects, thus affecting precision observables at hadron colliders like the Tevatron and the LHC. As a result, the authors reinforce the importance of employing a range of $R$ values and a variety of jet algorithms to address these effects robustly. This approach is crucial for accurate parton distribution functions and other precision measurements.

The paper provides a formal approach to quantifying these effects by leveraging Monte Carlo simulations with tools like Pythia and Herwig, comparing analytical results to computational outputs. These comparisons reveal striking agreements, particularly in the hadronisation component's behavior with $R$. These findings are crucial as they offer predictive power for the behavior of jets, thereby assisting in designing experimental setups to minimize non-perturbative uncertainties.

The future implications of this research are significant, pointing toward a more tailored treatment of jets in experiments, whereby adjustments to $R$ could optimize observations of specific phenomena while mitigating the impact of non-perturbative corrections. The study also opens avenues for further research to match and refine analytical estimates with perturbative resummations, extending the non-perturbative model's sophistication.

In conclusion, the paper underscores the need for flexibility and precision in jet studies at hadron colliders, suggesting that a robust understanding of non-perturbative QCD effects, particularly via the jet radius $R$, can significantly enhance the accuracy of experimental results in this field.