CMS Looks Deep Inside Quarks

Why It Matters

Confirming quarks as point‑like particles reinforces the Standard Model and guides future high‑energy collider designs. A tighter compositeness limit narrows the parameter space for theories proposing sub‑quark constituents, influencing both particle physics research and related technologies.

Key Takeaways

• CMS probes quark structure down to 10⁻²⁰ m scale
• No deviation from point‑like behavior observed in Run 2 data
• Compositeness limit set at 37 TeV, highest to date
• Future HL‑LHC runs aim to push sensitivity below 10⁻²⁰ m

Pulse Analysis

The quest to uncover ever‑smaller building blocks of matter has a storied history, from Rutherford’s gold‑foil experiment to the discovery of quarks in the 1960s. Modern particle physics now asks whether quarks themselves are elementary or composed of yet‑unknown constituents. This question drives the most energetic collisions at the Large Hadron Collider, where the CMS detector captures the spray of particles—jets—produced when quarks scatter off each other at unprecedented energies.

In a recent CMS analysis of Run 2 data, physicists reconstructed the scattering angles of dijet events to compare with the predictions for a truly point‑like quark. The observed angular distribution matched the Standard Model expectation, allowing the collaboration to set the most stringent compositeness limit to date: an energy scale of 37 TeV, corresponding to a spatial resolution of roughly 10⁻²⁰ metres. This result effectively rules out a wide class of models that predict quark substructure at lower energies, reinforcing confidence in the current theoretical framework.

Looking ahead, the High‑Luminosity LHC upgrade promises a tenfold increase in data volume and higher collision energies, which will sharpen the statistical precision of jet‑angle measurements. By reducing uncertainties, future analyses could probe distances below the current 10⁻²⁰ metre threshold, potentially revealing subtle deviations or confirming quark indivisibility with even greater certainty. Such advances not only deepen our understanding of fundamental physics but also drive innovations in detector technology, data processing, and high‑energy accelerator design, with ripple effects across scientific and industrial domains.