Physicists measure rare top quark interactions with unprecedented precision
Researchers at CERN have completed the most detailed measurements yet of how top quarks pair with W bosons—a rare process that tests the limits of our understanding of particle physics. The findings reveal slight deviations from theory that could point toward undiscovered particles, with implications for how accurately scientists can model fundamental forces.
Originaltitel: Measurements of $$ \textrm{t}\overline{\textrm{t}}\textrm{W} $$ differential cross sections and the leptonic charge asymmetry at $$ \sqrt{s}=13 $$ TeV
A bstract Measurements of properties of top quark-antiquark pair production in association with a W boson in proton-proton collisions at a center-of-mass energy of 13 TeV are presented, using a data sample corresponding to an integrated luminosity of 138 fb − 1 , recorded by the CMS experiment at the CERN LHC. Events are selected based on the presence of either two leptons with the same electric charge or three leptons, and multiple jets and b-tagged jets. We present measurements of differential production cross sections as a function of kinematic variables sensitive to different aspects of the process modeling, using a multivariate discriminator in the two-lepton selection region and a simple selection-based method in the three-lepton region. The normalized cross section measurements are generally consistent with the standard model expectations, while we observe larger values compared to the expectations in the absolute cross section measurements, consistent with previous inclusive cross section measurements. In addition, we measure the leptonic charge asymmetry of this process, obtaining an observed value of $$ {A}_c^{\ell }=-{0.19}_{-0.18}^{+0.16} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mi>A</mml:mi> <mml:mi>c</mml:mi> <mml:mi>ℓ</mml:mi> </mml:msubsup> <mml:mo>=</mml:mo> <mml:mo>−</mml:mo> <mml:msubsup> <mml:mn>0.19</mml:mn> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.18</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.16</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> , consistent with the expectation of − 0.085 ± 0.006 predicted by next-to-leading order simulations.