Flavor physics at the EIC with b-jet tagging

TL;DR

This paper proposes using $b$-jet counting at the Electron-Ion Collider (EIC) to detect new flavor-changing interactions involving third-generation quarks, achieving sensitivity to new physics scales up to around 5 TeV.

Contribution

It introduces a novel $b$-parity based method to probe TeV-scale flavor physics at the EIC, significantly extending the collider's sensitivity beyond its center-of-mass energy.

Findings

Counting $b$-jets can probe new physics scales up to 5 TeV.

Single $b$-jet channel is more sensitive than di-jet channel.

Sensitivity depends on $b$-tagging efficiency and electron beam polarization.

Abstract

We employ an approximate conserved quantum number (defined as "$b$-Parity" in [1]) of the Standard Model (SM): $b_P=(-1)^n$, where $n$ is the number of produced $b$-jets in the reaction $e + p/A \to n \cdot j_b +X$, to explore new TeV-scale flavor-changing interactions involving the 3rd generation quarks at the EIC; simply by counting the number of $b$-jets in the final state. In particular, the SM single and di-jet production at the EIC which occur through charge current interactions, $e + p/A \to j + \!\not\!E_T$ and $e + p/A \to 2\cdot j + \!\not\!E_T$, are $b_P$-even since the $b_P$-violating (i.e, $b_P=-1$) SM signals for these processes are necessarily CKM suppressed and, therefore, have a vanishingly small production rate. In contrast, new flavor physics can generate $b_P=-1$ signals at the EIC whose only significant SM background is due to $b$-jet misidentification. We thus show that $b_P$ can be used as a simple and sensitive probe of new flavor violating physics; specifically, we find that counting single $b$-jet events in $e + p/A \to j + \!\not\!E_T$ at the EIC with a center-of-mass (CM) energy of $\sqrt{s} \sim 140$ GeV, can probe scales of new physics up to $\Lambda \sim {\cal O}(5)$ TeV for a certain type of new chiral flavor-changing physics in 3rd generation interactions. This is remarkably more than 30 times larger than the assumed EIC CM energy and it critically depends on the $b$-tagging efficiency and purity as well as the feasibility of electron-beam polarization. The sensitivity of the di-jet process, $e + p/A \to 2j + \!\not\!E_T$, to these type of new physics is reduced compared to the single-jet channel.