Constraints On New Theories Using Rivet : CONTUR version 3 release note

Imagine the universe as a giant, cosmic detective story. For decades, scientists have been trying to solve the mystery of what makes up the universe. They have a very good "suspect list" called the Standard Model, which explains how tiny particles like electrons and quarks behave. It's like a perfect rulebook for a game, but the players know the rulebook is missing a few pages—there are things like dark matter and gravity that the book doesn't explain yet. To find the missing pages, physicists smash particles together at incredible speeds in massive machines called the Large Hadron Collider (LHC). These collisions create a chaotic explosion of new particles, and scientists look for tiny clues that don't fit the rulebook. If they find a clue that breaks the rules, it could mean a whole new theory of physics is hiding in the data. But with millions of collisions happening every second, finding that one weird clue is like looking for a specific grain of sand on a beach the size of a continent.

This is where a new tool called CONTUR comes in. Think of CONTUR as a super-smart, automated detective that can instantly check a new theory against a massive library of past clues. The paper you are reading is a release note for version 3 of this tool, a major upgrade that makes it faster, smarter, and more powerful. The authors, a team of physicists from universities in the UK, Poland, and the USA, have updated the software to handle a huge new collection of data from the LHC. They've added better ways to do the math, new tools to draw pictures of the results, and they've plugged in over 1,000 different measurements from recent experiments. The main goal is simple: to quickly tell scientists if their new ideas about the universe are still possible or if the data has already ruled them out.

The core of this paper is about upgrading the "detective kit." In the past, scientists would simulate a new theory, mix it with the known Standard Model, and then compare it to the data to see if it fit. CONTUR 3 does this much more efficiently. It now uses a library of over 1,000 specific measurements from the LHC, covering everything from how top quarks are made to how energy disappears (missing energy). Instead of just guessing, the tool can now inject these new theories into the data and see exactly how well they match up. If a new theory makes the prediction worse than the Standard Model alone, the tool flags it as "excluded" with a high degree of confidence.

One of the biggest changes in this version is how it handles the math. The new CONTUR 3 includes a better way to deal with the "noise" and uncertainties in the data, using something called covariance matrices to understand how different measurements are connected. It also introduces a new way to estimate what the LHC will be able to find in the future, specifically when it gets upgraded to the High-Luminosity LHC. This is like a weather forecast for particle physics; it gives a rough idea of how far the telescope can see if we keep collecting data for years, though the authors admit this is a "simplified estimate" and the real reach might be even better.

The paper also highlights a new feature that lets the tool work with another program called SPEY. This allows scientists to not just say "no" to a theory, but to find the "best fit" for how strong a new signal might be. It's the difference between saying "this suspect is innocent" and saying "this suspect might be innocent, but if they did it, here is exactly how much evidence would be needed to prove it." This helps researchers understand if a theory is just slightly off or if it's completely wrong.

To show off these new powers, the authors ran a test using a model of "Composite Dark Matter," which imagines dark matter is made of smaller, hidden particles. They used the new CONTUR 3 to check this model against real data from the LHC. The results were interesting: the tool found that for certain versions of this model, the data actually ruled them out with very high confidence (99.57% exclusion). Interestingly, the tool also showed that the "expected" limits (what they thought they would find) were much weaker than the "actual" limits. This happened because the Standard Model predictions were already a bit higher than the data in some areas, so adding the new theory pushed the prediction even further away, making the exclusion stronger than expected.

The paper concludes by noting that this new version of CONTUR is ready for use and is available for scientists to download. It works with the latest versions of the software that analyzes the raw data from the collider. While the tool itself doesn't discover new particles, it acts as a powerful filter, helping the physics community quickly sort through thousands of ideas and focus only on the ones that still have a chance of being true. It's a vital step in the ongoing quest to rewrite the rulebook of the universe, ensuring that when a new discovery is made, it's because the data demanded it, not because the math was too messy to see the truth.