Search for narrow resonances decaying to dijets in proton-proton collisions at sqrt(s) = 13 TeV
(1512.01224v2)
Published 3 Dec 2015 in hep-ex
Abstract: A search for narrow resonances in proton-proton collisions at sqrt(s) = 13 TeV is presented. The invariant mass distribution of the two leading jets is measured with the CMS detector using a data set corresponding to an integrated luminosity of 2.4 inverse femtobarns. The highest observed dijet mass is 6.1 TeV. The distribution is smooth and no evidence for resonant particles is observed. Upper limits at 95% confidence level are set on the production cross section for narrow resonances with masses above 1.5 TeV. When interpreted in the context of specific models, the limits exclude string resonances with masses below 7.0 TeV, scalar diquarks below 6.0 TeV, axigluons and colorons below 5.1 TeV, excited quarks below 5.0 TeV, color-octet scalars below 3.1 TeV, and W' bosons below 2.6 TeV. These results significantly extend previously published limits.
The paper presents a comprehensive search for narrow dijet resonances in 13 TeV proton-proton collisions using refined jet reconstruction techniques.
It establishes new exclusion limits for various models, ruling out string resonances below 7.0 TeV and setting stricter bounds on scalar diquarks, axigluons, and excited quarks.
The analysis confirms a smooth QCD dijet mass spectrum, providing critical constraints that narrow the search for new physics beyond the Standard Model.
Overview of the Paper: Search for Narrow Resonances Decaying to Dijet Pairs at s=13 TeV
This paper presents an analytical paper of narrow resonances in dijet systems produced by proton-proton collisions at a center-of-mass energy of s=13 TeV using 2.4 fb−1 of data recorded by the CMS detector during the 2015 running period of the CERN LHC, known as Run 2. The research investigates the invariant mass distribution of the two leading jets, aiming to discern any peaked structures that may indicate the presence of new massive particles beyond the Standard Model (SM).
Methodology and Data Analysis
Proton-proton collisions at high energies can produce multiple energetic jets, primarily through hard scattering of constituent partons. The quantum chromodynamics (QCD) predictions stipulate that the dijet mass spectrum should decrease smoothly without exhibiting resonances. This paper's focal point was to search for particles with masses above 1.5 TeV, providing stringent constraints on various hypothesized new phenomena that predict narrow resonance features in the dijet mass spectrum.
The analysis employed a refined reconstruction procedure to enhance the sensitivity to potential resonances. Jets were clustered using the anti-kt algorithm, immediately followed by a wide-jet approach, combining geometrically close jets to form wide jets and subsequently reconstructing the dijet system. This method significantly minimizes biases from gluon radiation and improves the identification of resonance signals.
No evidence for resonant particles was observed in the analyzed data, with the highest dijet mass reaching 6.1 TeV. The results confirmed the smooth distribution of the invariant mass spectrum, adhering to expectations of QCD processes, as verified through simulations using the {\PYTHIA8} event generator.
Implications and Findings
The paper explicitly set upper limits on the production cross sections for various models predicting such resonances, expanding the exclusion reach significantly beyond previously established limits:
String Resonances: Masses below 7.0 TeV were ruled out, advancing the previous limit of 5.0 TeV.
Axigluons and Colorons: Constrained below 5.1 TeV, exceeding the earlier limit of 3.6 TeV.
Excited Quarks: Excluded up to 5.0 TeV against ATLAS's limit of 4.06 TeV.
Color-Octet Scalars and $\PWpr$ Bosons: Additional mass exclusions were found.
These findings have profound implications in particle physics, particularly in testing the limits of SM extensions such as those involving novel gauge bosons, exotic quarks, and higher-dimensional gravity theories. The stringent constraints limit the mass range where such particles could exist, significantly narrowing the field for future theoretical exploration and search strategies.
Future Research Directions
The implications call for continued exploration at even higher energies and integrated luminosities, as further data could help refine and push current experimental boundaries. The CMS experiment must adapt methodologies to maintain sensitivity across broader dijet mass bands. As the search for new physics continues, fostering developments in detector technology and data analysis techniques is pivotal to uncovering subtle indications of non-SM phenomena.
Understanding systematic uncertainties remains crucial, particularly influences linked with the jet energy scale and resolution. Continued collaboration across global research entities and enhancements in computational models will aid in these endeavors.
In conclusion, while no direct evidence was found within the analyzed data, the robust constraints presented are vital to particle physics, providing a foundation for ongoing research initiatives and theoretical inquiries in understanding potential new physics beyond the Standard Model.