Physicists detect subtle asymmetry in particle decay using record-breaking collider data
Researchers have measured CP asymmetry in a rare D meson decay with unprecedented precision using the latest Large Hadron Collider data. The finding helps test fundamental physics theories and could inform future particle detector designs and high-energy physics research priorities.
Originaltitel: Measurement of CP asymmetry in $$ {D}^0\to {K}_{\textrm{S}}^0{K}_{\textrm{S}}^0 $$ decays with Run 3 data
A bstract A measurement of CP asymmetry in $$ {D}^0\to {K}_{\textrm{S}}^0{K}_{\textrm{S}}^0 $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mi>D</mml:mi> <mml:mn>0</mml:mn> </mml:msup> <mml:mo>→</mml:mo> <mml:msubsup> <mml:mi>K</mml:mi> <mml:mi>S</mml:mi> <mml:mn>0</mml:mn> </mml:msubsup> <mml:msubsup> <mml:mi>K</mml:mi> <mml:mi>S</mml:mi> <mml:mn>0</mml:mn> </mml:msubsup> </mml:math> decays is reported, based on a data sample of proton-proton collisions collected with the LHCb detector in 2024 at a centre-of-mass energy of 13.6 TeV, corresponding to an integrated luminosity of 6.2 fb − 1 . The $$ {D}^0\to {K}_{\textrm{S}}^0{\pi}^{+}{\pi}^{-} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mi>D</mml:mi> <mml:mn>0</mml:mn> </mml:msup> <mml:mo>→</mml:mo> <mml:msubsup> <mml:mi>K</mml:mi> <mml:mi>S</mml:mi> <mml:mn>0</mml:mn> </mml:msubsup> <mml:msup> <mml:mi>π</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msup> <mml:mi>π</mml:mi> <mml:mo>−</mml:mo> </mml:msup> </mml:math> decay is used as calibration channel to cancel residual detection and production asymmetries. The time-integrated CP asymmetry for the $$ {D}^0\to {K}_{\textrm{S}}^0{K}_{\textrm{S}}^0 $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mi>D</mml:mi> <mml:mn>0</mml:mn> </mml:msup> <mml:mo>→</mml:mo> <mml:msubsup> <mml:mi>K</mml:mi> <mml:mi>S</mml:mi> <mml:mn>0</mml:mn> </mml:msubsup> <mml:msubsup> <mml:mi>K</mml:mi> <mml:mi>S</mml:mi> <mml:mn>0</mml:mn> </mml:msubsup> </mml:math> mode is measured to be $$ {\mathcal{A}}^{CP}\left({D}^0\to {K}_{\textrm{S}}^0{K}_{\textrm{S}}^0\right)=\left(1.86\pm 1.04\pm 0.41\right)\%, $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mi>A</mml:mi> <mml:mi>CP</mml:mi> </mml:msup> <mml:mfenced> <mml:mrow> <mml:msup> <mml:mi>D</mml:mi> <mml:mn>0</mml:mn> </mml:msup> <mml:mo>→</mml:mo> <mml:msubsup> <mml:mi>K</mml:mi> <mml:mi>S</mml:mi> <mml:mn>0</mml:mn> </mml:msubsup> <mml:msubsup> <mml:mi>K</mml:mi> <mml:mi>S</mml:mi> <mml:mn>0</mml:mn> </mml:msubsup> </mml:mrow> </mml:mfenced> <mml:mo>=</mml:mo> <mml:mfenced> <mml:mrow> <mml:mn>1.86</mml:mn> <mml:mo>±</mml:mo> <mml:mn>1.04</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.41</mml:mn> </mml:mrow> </mml:mfenced> <mml:mo>%</mml:mo> <mml:mo>,</mml:mo> </mml:math> where the first uncertainty is statistical, and the second is systematic. This measurement represents the most precise single-experiment determination of this quantity to date.