Measurement of <math display="inline"><msup><mi>D</mi><mn>0</mn></msup></math> Meson Photoproduction in Ultraperipheral Heavy Ion Collisions
(2026) Physical Review Letters — Vol. 136 (2026)
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- This Letter reports the first measurement of photonuclear <math display="inline"><msup><mi>D</mi><mn>0</mn></msup></math> meson production in ultraperipheral heavy ion collisions. The study is performed using lead-lead collision data, with an integrated luminosity of <math display="inline"><mn>1.34</mn><mtext> </mtext><mtext> </mtext><msup><mi>nb</mi><mrow><mo>-</mo><mn>1</mn></mrow></msup></math>, collected by the CMS experiment at a nucleon-nucleon center-of-mass energy of 5.36 TeV. Photonuclear events, where one of the colliding nuclei breaks up and the other remains intact, are selected based on breakup neutron emissions and by requiring no particle activity in a large rapidity interval in the direction of the photon-emitting nucleus. The <math display="inline"><msup><mi>D</mi><mn>0</mn></msup></math> mesons are reconstructed via the <math display="inline"><msup><mi>D</mi><mn>0</mn></msup><mo stretchy="false">→</mo><msup><mi>K</mi><mo>-</mo></msup><msup><mi>π</mi><mo>+</mo></msup></math> decay channel, with the cross section measured as a function of <math display="inline"><msup><mi>D</mi><mn>0</mn></msup></math> meson transverse momentum and rapidity. The results are compared with next-to-leading-order perturbative QCD calculations that employ recent parametrizations of the lead nuclear parton distribution functions, as well as with predictions based on the color glass condensate framework. This measurement is the first photonuclear collision study characterizing parton distribution functions of lead nuclei for parton fractional momenta <math display="inline"><mi>x</mi></math> (relative to the nucleon) ranging approximately from a few <math display="inline"><msup><mn>10</mn><mrow><mo>-</mo><mn>4</mn></mrow></msup></math> to <math display="inline"><msup><mn>10</mn><mrow><mo>-</mo><mn>2</mn></mrow></msup></math> for different hard energy scale <math display="inline"><msup><mi>Q</mi><mn>2</mn></msup></math> selections.
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Bein, S., Benecke, A., Bethani, A., Bruno, G., Cappati, A., de Favereau de Jeneret, J., Delaere, C., Giammanco, A., Guzel, A. O., Jain, S., Jain, S., Lemaitre, V., Lidrych, J., Mastrapasqua, P., Turkcapar, S., CMS, & et al. (2026). Measurement of <math display=“inline”><msup><mi>D</mi><mn>0</mn></msup></math> Meson Photoproduction in Ultraperipheral Heavy Ion Collisions. Physical Review Letters, 136. https://doi.org/10.1103/lckg-sdh9 (Original work published 2026)