Week 2 – BRAVO Tuesday!

Well, here begins the researching of the research papers — time to find a literature-stated range for the Wilson coefficients we used (c_HB and c_HW).

Lucky me! The second paper I picked actually includes some of the data we need. It’s titled “The Effective Standard Model after LHC Run I” by John Ellis. See the two operators that include them — nice! I might check these limits with Jon in our next meeting (hopefully this week).

Let’s revise the relationship between coefficients, operators, coupling constants, and Lagrangians.

🎯 Coupling Constants

• A coupling constant tells us how strong an interaction is between fields or particles.
• Examples:
  • g: coupling between gauge bosons and fermions
  • y_f​: Yukawa coupling (Higgs–fermions)
  • g_hZZ: coupling strength between the Higgs and two Z bosons
• In the Standard Model, these are fixed constants.
• In EFT, these constants are shifted due to the presence of higher-dimensional operators.

From the same paper as above, it’s clear that they obtained similar results by varying c_HW​ (and likely c_HB as well) — showing a strong effect in the high-pTpT​region. This is because the operatormodifies the interaction between the Higgs and the W and Z bosons. After electroweak symmetry breaking (EWSB), it introduces momentum-dependent corrections to the Higgs–gauge boson vertices — especially hWW and hZZ. Thus, at low energies, the effect of cHW is suppressed.

The next paper by John Ellis (a legend, really), “Complete Higgs Sector Constraints on Dimension-6 Operators,” could also be interesting to look at, though it’s a bit more on the theoretical side. I’m still a little confused about linking the coefficients to the kappa framework, so I’ll need some clarification from Jon — and this time, I promise I’ll make notes on everything he says.

That’s enough paper reading for now — tomorrow is a project day off. 😌