The anomalous <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"><mml:mi>Z</mml:mi><mml:mi>b</mml:mi><mml:mover accent="true"><mml:mrow><mml:mi>b</mml:mi></mml:mrow><mml:mrow><mml:mo stretchy="false">¯</mml:mo></mml:mrow></mml:mover></mml:math> couplings at the HERA and EIC
Bin Yan, Zhite Yu, C.–P. Yuan
Abstract
To resolve the long-standing discrepancy between the precision measurement of bottom quark forward-backward asymmetry at LEP/SLC and the Standard Model prediction, we propose a novel method to probe the Zbb¯ coupling by measuring the single-spin asymmetry Aeb of the polarized lepton cross section in neutral current DIS processes with a b-tagged jet at HERA and EIC. Depending on the tagging efficiency of the final state b-jet, the measurement of Aeb at HERA can already partially break the degeneracy found in the anomalous Zbb¯ coupling, as implied by the LEP and SLC precision electroweak data. In the first year run of the EIC, the measurement of Aeb can already break the degeneracy, due to its much larger luminosity and higher electron beam polarization. With enough integrated luminosity collected at the EIC, it is possible to either verify or exclude the LEP data and resolve the AFBb puzzle. We also discuss the complementary roles between the proposed Aeb measurement at EIC and the measurement of gg→Zh cross section at the HL-LHC in constraining the anomalous Zbb¯ coupling.