Jet energy scale and resolution in the CMS experiment in pp collisions at 8 TeV (1607.03663v2)

Abstract: Improved jet energy scale corrections, based on a data sample corresponding to an integrated luminosity of 19.7 inverse-femtobarns collected by the CMS experiment in proton-proton collisions at a center-of-mass energy of 8 TeV, are presented. The corrections as a function of pseudorapidity eta and transverse momentum pT are extracted from data and simulated events combining several channels and methods. They account successively for the effects of pileup, uniformity of the detector response, and residual data-simulation jet energy scale differences. Further corrections, depending on the jet flavor and distance parameter (jet size) R, are also presented. The jet energy resolution is measured in data and simulated events and is studied as a function of pileup, jet size, and jet flavor. Typical jet energy resolutions at the central rapidities are 15-20% at 30 GeV, about 10% at 100 GeV, and 5% at 1 TeV. The studies exploit events with dijet topology, as well as photon+jet, Z+jet and multijet events. Several new techniques are used to account for the various sources of jet energy scale corrections, and a full set of uncertainties, and their correlations, are provided. The final uncertainties on the jet energy scale are below 3% across the phase space considered by most analyses (pT > 30 GeV and abs(eta) < 5.0). In the barrel region (abs(eta) < 1.3) an uncertainty below 1% for pT > 30 GeV is reached, when excluding the jet flavor uncertainties, which are provided separately for different jet flavors. A new benchmark for jet energy scale determination at hadron colliders is achieved with 0.32% uncertainty for jets with pT of the order of 165-330 GeV, and abs(eta) < 0.8.

• The paper presents a calibrated approach for jet energy scale measurements achieving systematic uncertainties below 1% in the central barrel region.
• It employs a multi-stage correction strategy including pileup offset, simulated, and residual data/MC corrections to refine jet responses across various conditions.
• The analysis sets new benchmarks for CMS detector performance, enabling more precise measurements for future LHC physics and new physics explorations.

Jet Energy Scale and Resolution in the CMS Experiment: An Analysis of Proton-Proton Collisions at 8 TeV

The paper outlines the methodologies and results concerning jet energy scale (JES) and jet energy resolution (JER) achieved by the Compact Muon Solenoid (CMS) experiment, utilizing data amassed from proton-proton collisions at a center-of-mass energy of 8 TeV. This analysis leverages an extensive dataset corresponding to an integrated luminosity of 19.7 fb$^{-1}$.

Calibration and Correction Strategy

The paper employs a comprehensive strategy to calibrate jets in the CMS detector, addressing the complex interaction between detector response, pileup corrections, and intrinsic jet properties, such as jet flavor. The procedure is segmented into several stages:

1. Pileup Offset Correction: The pileup offset, due to additional particle collisions occurring in the same bunch crossing, is initially corrected using simulations complemented by real data, extracted via the random-cone method in zero-bias events.
2. Simulated Response Corrections: Monte Carlo (MC) simulations generate initial response corrections across different jet algorithms and configurations to approximate detector responses over a broad phase space in $\eta$ and \pt.
3. Residual Data/MC Corrections: These corrections focus on discrepancies between data and simulation, enhancing the calibration precision across rapidity ($\eta$) and transverse momentum (\pt). Data from dijet, $\gamma$+jet, and $\PZ$+jet events inform these adjustments, providing a robust cross-check against simulation discrepancies.
4. Flavor and \pt-Specific Corrections: Jet energy scales are fine-tuned according to specific jet flavors and extended into high-\pt regimes using multijet events to correct higher-order discrepancies.
5. Jet Energy Resolution (JER): This involves measuring the spread in jet energy measurement both in data and simulations. The JER determination is crucial for accounting for detector effects that cannot be inherently corrected.

Results

The CMS experiment achieves an impressive standard for precise jet calibration, with a systematic uncertainty in JES maintained below 1% in the central barrel region ($\abs{\eta} < 1.3$) for jets above 30 GeV, excluding jet flavor uncertainties. This precision is exemplified by a minimum uncertainty of 0.32% for \pt between 165 and 330 GeV and $\abs{\eta} < 0.8$. Overall uncertainties in the wider phase space remain below 3%.

Theoretical and Practical Implications

The research provides a robust framework for future analyses in high-energy physics, particularly in calibrating jets within proton-proton collisions at large hadron colliders (LHC). The refined measurement techniques and enhanced calibration accuracy facilitate more precise determinations of fundamental particle properties and interactions.

Future Directions

The precision demonstrated by these methodologies sets a new benchmark, driving further exploration of more granular detector performance studies and finer correction algorithms that could adaptively respond to evolving collider conditions. This work also prompts further investigation into reducing systematic uncertainties, particularly for different jet flavors and extreme \pt values, potentially extending insights into new physics beyond the standard model.