TY - JOUR

T1 - First Experimental Constraint on the Scalar Current in the 퐷0⁢(+) → ¯퐾⁢ℓ+⁢휈ℓ Transition

AU - BESIII Collaboration

AU - Ачасов, Михаил Николаевич

AU - Мучной, Николай Юрьевич

AU - Николаев, Иван Борисович

N1 - The BESIII Collaboration thanks the staff of BEPCII [64] and the IHEP computing center for their strong support. This work is supported in part by National Key R&D Program of China under Contracts No. 2023YFA1606000 and No. 2023YFA1606704; National Natural Science Foundation of China under Contracts No. 11635010, No. 11935015, No. 11935016, No. 11935018, No. 12025502, No. 12035009, No. 12035013, No. 12061131003, No. 12192260, No. 12192261, No. 12192262, No. 12192263, No. 12192264, No. 12192265, No. 12221005, No. 12225509, No. 12235017, No. 12342502, and No. 12361141819; the Chinese Academy of Sciences (CAS) Large-Scale Scientific Facility Program; the Strategic Priority Research Program of Chinese Academy of Sciences under Contract No. XDA0480600; CAS under Contract No. YSBR-101; 100 Talents Program of CAS; The Institute of Nuclear and Particle Physics and Shanghai Key Laboratory for Particle Physics and Cosmology; ERC under Contract No. 758462; German Research Foundation DFG under Contract No. FOR5327; Istituto Nazionale di Fisica Nucleare, Italy; Knut and Alice Wallenberg Foundation under Contracts No. 2021.0174, No. 2021.0299, and No. 2023.0315; Ministry of Development of Turkey under Contract No. DPT2006K-120470; National Research Foundation of Korea under Contract No. NRF-2022R1A2C1092335; National Science and Technology fund of Mongolia; Polish National Science Centre under Contract No. 2024/53/B/ST2/00975; STFC (United Kingdom); Swedish Research Council under Contract No. 2019.04595; and U.S. Department of Energy under Contract No. DE-FG02-05ER41374.

PY - 2026/8/27

Y1 - 2026/8/27

N2 - Using 20.3  fb−1 of 푒+⁢푒− collision data taken at the center-of-mass energy of √푠=3.773  GeV, we report the first experimental constraint on the scalar current in the 퐷0⁢(+) → ¯퐾⁢ℓ+⁢휈ℓ transitions, based on a simultaneous fit to the first measured forward-backward asymmetries and precisely determined partial decay rates. The parameters of the scalar current are determined to be Re⁡(푐휇푆)=0.017±0.00⁢8stat±0.00⁢6syst and Im⁡(푐휇푆)=±0.077±0.01⁢1stat±0.00⁢9syst), which deviates from the standard model by a significance of 2.3⁢휎. The branching fractions of 퐷0⁢(+) → ¯퐾⁢ℓ+⁢휈ℓ, the hadronic form factor 푓+⁡(0), and the modulus of the 푐 →푠 Cabibbo-Kobayahsi-Maskawa matrix element |푉푐⁢푠| are also determined with improved precision. In addition, lepton flavor universality is tested via the ratios of the decay rates between semimuonic and semielectronic decays in the full momentum transfer range and in subranges.

AB - Using 20.3  fb−1 of 푒+⁢푒− collision data taken at the center-of-mass energy of √푠=3.773  GeV, we report the first experimental constraint on the scalar current in the 퐷0⁢(+) → ¯퐾⁢ℓ+⁢휈ℓ transitions, based on a simultaneous fit to the first measured forward-backward asymmetries and precisely determined partial decay rates. The parameters of the scalar current are determined to be Re⁡(푐휇푆)=0.017±0.00⁢8stat±0.00⁢6syst and Im⁡(푐휇푆)=±0.077±0.01⁢1stat±0.00⁢9syst), which deviates from the standard model by a significance of 2.3⁢휎. The branching fractions of 퐷0⁢(+) → ¯퐾⁢ℓ+⁢휈ℓ, the hadronic form factor 푓+⁡(0), and the modulus of the 푐 →푠 Cabibbo-Kobayahsi-Maskawa matrix element |푉푐⁢푠| are also determined with improved precision. In addition, lepton flavor universality is tested via the ratios of the decay rates between semimuonic and semielectronic decays in the full momentum transfer range and in subranges.

KW - Cabibbo–Kobayashi–Maskawa matrix

KW - Electroweak interaction

KW - Charmed mesons

KW - Hypothetical scalars

UR - https://www.scopus.com/pages/publications/105050019046

U2 - 10.1103/2ygw-n5b1

DO - 10.1103/2ygw-n5b1

M3 - Article

VL - 137

JO - Physical Review Letters

JF - Physical Review Letters

SN - 0031-9007

IS - 9

M1 - 091803

ER -