All articles tagged with #standard model
The article explains that counting elementary particles isn’t straightforward: textbooks list 17, but including antiparticles, color charges, chirality, and polarization expands the tally; a 2011 theorem shows the Standard Model’s effective degrees of freedom total 995.5, meaning the true count depends on energy scale and how one defines particles.
Researchers at CERN's LHCb observed ~650 billion B-meson decays and found a four-sigma discrepancy with Standard Model predictions in rare penguin-like decays, a potential hint of new physics. If confirmed, explanations could involve a Z' boson or leptoquarks; further analysis of data since 2018 and upgrades planned for the 2030s are expected to clarify whether this is genuine new physics or a statistical fluctuation.
CERN’s LHCb reports a four-sigma deviation from Standard Model predictions in a rare penguin decay of B mesons to a kaon, a pion and two muons, suggesting possible undiscovered physics. The independent CMS results earlier in 2025 strengthen the case, but five-sigma confirmation is not yet reached; future LHC upgrades and larger datasets are planned to verify or refute the deviation.
LHCb’s study of a rare penguin decay—B mesons decaying to a kaon and two muons—shows angular distributions that differ from Standard Model predictions at about 4 sigma, hinting that new particles could enter the decay loop. Possible explanations include a heavier Z’ boson or leptoquarks, with CMS hinting at a compatible but less significant signal. The analysis uses ~650 billion decays from 2011–2018, making this one of the most intriguing LHC anomalies, though it could still be affected by charming-penguin effects. Further data are needed to confirm any new physics.
A long-standing puzzle about the muon's anomalous magnetic moment (g-2) is resolved by a new, ultra-precise lattice QCD calculation that aligns the Standard Model prediction with experimental measurements within half a standard deviation. The result removes the need for a hypothetical fifth force and reinforces quantum field theory as the foundation of particle physics, though it may still leave a narrow window for new physics to appear in future experiments.
Penn State researchers using a high-precision, grid-based QCD calculation have shown the muon’s magnetic moment now matches Standard Model predictions to 11 digits (0.5 sigma), resolving a decades‑long discrepancy and cooling expectations for new physics beyond the Standard Model.
A Nature paper using lattice QCD and hybrid simulations shows the muon's anomalous magnetic moment is consistent with the Standard Model within about half a standard deviation and 11 decimal places. The result suggests the earlier discrepancy hinting at a fifth force was a calculation artefact, not new physics, while tightening constraints on possible beyond‑SM explanations through a precise treatment of hadronic vacuum polarization.
New LHCb results on rare B-meson decays, corroborated by CMS data, show tensions with Standard Model predictions in electroweak penguin processes, hinting at heavy new particles such as leptoquarks. While not definitive, the anomalies are growing and future LHC upgrades and larger datasets may confirm a need for new physics beyond the Standard Model.
New results from CERN’s LHCb show a rare electroweak penguin decay of B mesons that disagrees with Standard Model predictions at about four standard deviations, hinting at possible new physics. The finding is supported by earlier CMS results and comes from analyzing roughly 650 billion B decays (2011–2018). Although intriguing, it does not reach the five-sigma discovery threshold; further data and upgrades planned for the 2030s could confirm whether this points to new particles or remains a heavy overlap within the current theory.
Two new measurements (Nature and PRL) yield a proton radius of about 0.84 femtometers, consistent with the 2010 muonic-hydrogen result and with electron-based experiments and theory, effectively resolving the proton-radius puzzle and finding no evidence for physics beyond the Standard Model.
CMS analyzed over 100 million W→μν decays from 2016 pp collisions at 13 TeV to extract mW using a highly granular, in-situ template fit of the muon pT, eta and charge distributions, aided by state-of-the-art NNLO+N3LL theory and data-driven PDFs; the result mW = 80,360.2 ± 9.9 MeV agrees with the Standard Model and helps address the prior CDF tension, with an additional W+ vs W− mass difference measurement of 57.0 ± 30.3 MeV. The analysis validates via Z-boson mass checks and a W-like mZ cross-check, and features robust muon momentum scale and hadronic recoil calibrations.
More than a decade after the Higgs discovery, particle physics has yet to find new physics beyond the Standard Model, prompting a crisis about the field’s direction. Proposals for big next-gen machines (the Future Circular Collider, muon colliders) and smaller-scale tests (axions, hidden valleys) mingle with advances in AI-assisted data analysis, but there’s no discovery guarantee and talent is drifting toward other fields. In short, particle physics isn’t dead, but it’s hard—and the path forward remains uncertain.
As 2025 concludes, the Standard Model of particle physics and cosmology remains robust despite numerous puzzles and challenges, with recent experiments reinforcing its predictions and no definitive evidence yet for physics beyond it. Key mysteries like dark matter, dark energy, and the matter-antimatter asymmetry persist, but current data strongly support the existing framework, emphasizing the need for continued investment in experimental and observational science to uncover deeper truths.
A new model suggests that the universe's rapid early expansion, or inflation, occurred in a warm environment filled with known elementary particles, primarily involving the strong force and hypothetical axion-like particles, making it testable with current experiments like MADMAX.
Chen-ning Yang, a Nobel Prize-winning physicist renowned for his work on the Yang–Mills theory which is fundamental to the Standard Model of particle physics, has died at age 103 in Beijing.