Challenges in the extraction of physics beyond the Standard Model from electron scattering

Abstract Precise measurements of electron and positron scattering, including parity violation, offer great promise in the search for physics beyond the Standard Model (SM). In this context it is crucial to understand the corrections which might arise from charge symmetry violation, as well as the less well known strange and charm quark distributions. Our analysis, using state of the art parton distributions, suggests that these contributions lead to corrections in the extraction of the weak couplings <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mi>g</mml:mi> <mml:mrow> <mml:mi>A</mml:mi> <mml:mi>V</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>e</mml:mi> <mml:mi>q</mml:mi> </mml:mrow> </mml:msubsup> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mi>g</mml:mi> <mml:mrow> <mml:mi>V</mml:mi> <mml:mi>A</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>e</mml:mi> <mml:mi>q</mml:mi> </mml:mrow> </mml:msubsup> </mml:math> of the order (1−2)%, while they are as large as 4% for <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mi>g</mml:mi> <mml:mrow> <mml:mi>A</mml:mi> <mml:mi>A</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>e</mml:mi> <mml:mi>q</mml:mi> </mml:mrow> </mml:msubsup> </mml:math> , at a typical scale of Q 2 = 10 GeV 2 . These results underline the importance of carrying out high precision measurements, which will not only provide information on physics beyond the SM but also reduce the current uncertainties on our knowledge of the strange and charm quark distributions in the proton.