Simultaneous Probe of the Charm and Bottom Quark Yukawa Couplings Using tt[over ¯]H Events

Area of Science:

• High Energy Physics
• Particle Physics
• Standard Model Physics

Background:

• The Standard Model (SM) of particle physics describes fundamental particles and forces.
• The Higgs boson is a key particle in the SM, responsible for mass.
• Understanding Higgs boson couplings to different quarks is crucial for testing the SM.

Purpose of the Study:

• To search for the rare decay of the Higgs boson into a charm quark-antiquark pair (H→cc[over ¯]).
• To measure the Higgs boson decay to bottom quark-antiquark pairs (H→bb[over ¯]) in association with top quark-antiquark pairs (tt[over ¯]H).
• To constrain the Higgs-charm Yukawa coupling modifier (κc).

Main Methods:

• Analysis of proton-proton collision data at sqrt[s]=13 TeV with 138 fb⁻¹ integrated luminosity.
• Utilized advanced machine learning for jet flavor identification and event classification.
• Simultaneous measurement of tt[over ¯]H production with H→bb[over ¯] and H→cc[over ¯] decays.

Main Results:

• The observed event rate for tt[over ¯]H(H→bb[over ¯]) was 0.91_{-0.22}^{+0.26} relative to the SM prediction.
• An upper limit on σ(tt[over ¯]H)B(H→cc[over ¯]) was set at 0.11 pb (observed) and 0.13 pb (expected) at 95% confidence level.
• Combined with previous results, the observed 95% confidence interval for |κc| is <3.5, and expected is <2.7.

Conclusions:

• The study sets the most stringent limit to date on the Higgs-charm Yukawa coupling.
• The results are consistent with the Standard Model predictions.
• This search advances our understanding of Higgs boson interactions with light quarks.