Naive $T$-odd Drell-Yan angular coefficients as a probe of the dimension-8 SMEFT

TL;DR

The paper targets CP-odd new physics in Drell-Yan processes by leveraging naive $T$-odd Collins-Soper moments $A_6$ and $A_7$, which are negligible in the SM and first arise at ${ m O}( olinebreak \alpha_s^2)$. It employs the SMEFT to parametrize heavy new physics with CP-odd, dimension-8 four-fermion operators that include a gluon field-strength, yielding high-$m_{ ilde{ ll}}$ and high-$p_T$ effects that shift $A_6$ and $A_7$, with observables linearized in Wilson coefficients. The analysis shows that HL-LHC with ${ m L}=3~{ m ab}^{-1}$ can probe Wilson coefficients up to a few TeV, though flat directions emerge when multiple operators are active, necessitating joint $A_6$ and $A_7$ fits and consideration of left- versus right-handed currents. Overall, the work extends SMEFT probes to dimension-8 CP-odd directions in Drell-Yan, offering guidance for experimental strategies to constrain UV completions of new physics.

Abstract

We propose the ``naive" $T$-odd Collins-Soper moments in the Drell-Yan process as probes of previously unexplored directions in the Standard Model Effective Field Theory (SMEFT) parameter space. We show that the moments $A_6$ and $A_7$ in the high invariant mass and transverse momentum region are sensitive to dimension-8 $CP$-odd semi-leptonic four-fermion operators with an additional gluon field strength tensor. Using the projected integrated luminosity of a future high-luminosity LHC, we show that effective ultraviolet scales in the few-TeV range can be probed with this process.

Figures (15)

• Figure 1: The tree-level Feynman diagrams describing the underlying partonic processes: (a) pair annihilation, (b) Compton scattering.
• Figure 2: The ratios of the inclusive SM and SMEFT cross sections to the $Z$-peak for the invariant mass bin $m_{\ell\ell}=[170, 350]$ GeV. The effective scale is set $\Lambda = 2 \ {\rm TeV}$, and the SMEFT contributions are amplified by a factor of 100 for the $CP$-even operators and 10,000 for the $CP$-odd operators.
• Figure 3: The same as Fig. \ref{['fig:smeft_contributions_to_xs_1']} but for $m_{\ell\ell} = [350, 1000]$ GeV.
• Figure 4: SMEFT corrections to the $A_6$ and $A_7$ moments as a function of $p_T$ in the invariant mass bin $76 < m_{ll} < 106$ GeV.
• Figure 5: The same as Fig. \ref{['fig:bin1']} but for $170 < m_{\ell\ell} < 350$ GeV.