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CMS Experiment at CERN Reports New W Boson Mass Measurement
The CMS experiment at CERN has made significant advancements in measuring the mass of the W boson, an essential elementary particle that, alongside the Z boson, is fundamental to the weak force. This force plays a crucial role in various processes, including certain types of radioactive decay and the nuclear fusion reactions that sustain the sun’s energy.
During a seminar on September 17, the CMS collaboration revealed its analysis of proton–proton collision data from the second run of the Large Hadron Collider (LHC), marking a new milestone in W boson mass measurement.
The latest findings represent the most accurate W boson mass measurement achieved at the LHC to date. This new measurement is consistent with predictions from the Standard Model of particle physics and aligns with previous experimental results, with the notable exception of a recent measurement from the CDF experiment at Fermilab’s Tevatron collider.
In the context of the Standard Model, the mass of the W boson is intricately linked to the strength of the interactions that unify the electromagnetic and weak forces, as well as the masses of other crucial particles, including the Higgs boson and the top quark. This relationship restricts the W boson mass to approximately 80,353 million electronvolts (MeV) with an uncertainty of 6 MeV.
High-precision measurements of the W boson mass are vital for testing the consistency of the Standard Model. Significant discrepancies from expected values could indicate the existence of new physics, potentially involving previously unknown particles or interactions.
Since its discovery roughly 40 years ago, various collider experiments, including those at CERN, have progressively refined the measurement of the W boson mass. In 2022, the CDF experiment reported a notably high W boson mass of 80,433.5 MeV, which diverged from the Standard Model predictions and other experimental findings, igniting discussions within the scientific community about the need for further investigation.
The ATLAS collaboration, which first measured the W boson mass in 2017, issued a revised measurement in 2023 based on a thorough reanalysis of initial LHC collision data. Their updated figure came in at 80,366.5 MeV, aligning with all previous measurements except for the CDF’s, which remains the highest precision measurement thus far.
The CMS experiment’s new finding signals its inaugural W boson mass measurement, calculated at 80,360.2 MeV with an uncertainty of 9.9 MeV. This result closely matches the precision of the CDF measurement and is consistent with all previous determinations, again excepting the CDF outcome.
Patricia McBride, the outgoing CMS spokesperson, commented, “The wait for the CMS result is now over. After carefully analyzing data from 2016 and completing numerous cross-checks, we are excited to present this W mass measurement.” McBride noted the significance of this analysis, referencing its conduct within the challenging collision environment of the LHC’s second operational period.
Incoming CMS spokesperson Gautier Hamel de Monchenault added, “The challenges associated with W mass measurements require intricate measurements and theoretical models for understanding the production and decay of the W boson.” He emphasized the CMS detector’s ability to precisely measure muons, which significantly contributed to achieving this high level of precision.
This measurement not only reiterates the capabilities of the LHC and its detectors but also underscores the ongoing commitment to pushing the boundaries of precision measurement in particle physics, consequently allowing the Standard Model and potential extensions to face increasingly rigorous tests. As the third run of the collider progresses, along with future upgrades to the High-Luminosity LHC, further advancements in understanding fundamental particles are anticipated.
More information: Paper: Measurement of the W boson mass in proton-proton collisions at √s =13 TeV
Citation: CMS experiment at CERN weighs in on the W boson mass (2024, September 17) retrieved 17 September 2024 from https://phys.org/news/2024-09-cms-cern-boson-mass.html
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