First Measurement of the 𝐷+ 𝑠 →𝐾0⁢𝜇+⁢𝜈𝜇 Decay

BES III Collaboration; M. Ablikim; M. N. Achasov; P. Adlarson; X.C. Ai; R. Aliberti; A. Amoroso; Q. An; Nasser Kalantar-Nayestanaki; Myroslav Kavatsyuk

doi:10.1103/bk2n-lgps

First Measurement of the 𝐷+ 𝑠 →𝐾0⁢𝜇+⁢𝜈𝜇 Decay

BES III Collaboration
, M. Ablikim
, M. N. Achasov
, P. Adlarson
, X.C. Ai
, R. Aliberti
, A. Amoroso
, Q. An
, Nasser Kalantar-Nayestanaki
, Myroslav Kavatsyuk

Nuclear Energy

Research output: Contribution to journal › Article › Academic › peer-review

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Abstract

We report the first measurement of the semileptonic decay 𝐷+
𝑠→𝐾0⁢𝜇+⁢𝜈𝜇, using a sample of 𝑒+⁢𝑒− annihilation data corresponding to an integrated luminosity of 7.33 fb−1 collected at center-of-mass energies between 4.128 and 4.226 GeV with the BESIII detector at the BEPCII collider. The branching fraction of the decay is measured to be ℬ⁡(𝐷+
𝑠→𝐾0⁢𝜇+⁢𝜈𝜇)=(2.89±0.2⁢7stat±0.1⁢2syst)×10−3, where the first uncertainty is statistical and the second is systematic. Based on a simultaneous fit to the partial decay rates in 𝑞2 intervals measured in 𝐷+
𝑠→𝐾0⁢𝜇+⁢𝜈𝜇 and 𝐷+
𝑠 →𝐾0⁢𝑒+⁢𝜈𝑒 decays, the product value of the form factor 𝑓𝐾0
+⁡(0) and the Cabibbo-Kobayashi-Maskawa matrix element |𝑉𝑐⁢𝑑| is measured to be 𝑓𝐾0
+⁡(0)⁢|𝑉𝑐⁢𝑑|=0.140±0.00⁢8stat±0.00⁢3syst, which is the most precise determination to date. In addition, lepton flavor universality is tested for the first time with 𝐷+
𝑠→𝐾0⁢ℓ+⁢𝜈ℓ decays in full and separate 𝑞2 intervals. No violation is found.

Original language	English
Article number	161802
Number of pages	11
Journal	Physical Review Letters
Volume	136
Issue number	16
DOIs	https://doi.org/10.1103/bk2n-lgps
Publication status	Published - 22-Apr-2026

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@article{c95326c17c814d028585e5d861170d8c,

title = "First Measurement of the 𝐷+ 𝑠 →𝐾0⁢𝜇+⁢𝜈𝜇 Decay",

abstract = "We report the first measurement of the semileptonic decay 𝐷+ 𝑠→𝐾0⁢𝜇+⁢𝜈𝜇, using a sample of 𝑒+⁢𝑒− annihilation data corresponding to an integrated luminosity of 7.33 fb−1 collected at center-of-mass energies between 4.128 and 4.226 GeV with the BESIII detector at the BEPCII collider. The branching fraction of the decay is measured to be ℬ⁡(𝐷+ 𝑠→𝐾0⁢𝜇+⁢𝜈𝜇)=(2.89±0.2⁢7stat±0.1⁢2syst){\texttimes}10−3, where the first uncertainty is statistical and the second is systematic. Based on a simultaneous fit to the partial decay rates in 𝑞2 intervals measured in 𝐷+ 𝑠→𝐾0⁢𝜇+⁢𝜈𝜇 and 𝐷+ 𝑠 →𝐾0⁢𝑒+⁢𝜈𝑒 decays, the product value of the form factor 𝑓𝐾0 +⁡(0) and the Cabibbo-Kobayashi-Maskawa matrix element |𝑉𝑐⁢𝑑| is measured to be 𝑓𝐾0 +⁡(0)⁢|𝑉𝑐⁢𝑑|=0.140±0.00⁢8stat±0.00⁢3syst, which is the most precise determination to date. In addition, lepton flavor universality is tested for the first time with 𝐷+ 𝑠→𝐾0⁢ℓ+⁢𝜈ℓ decays in full and separate 𝑞2 intervals. No violation is found.",

author = "\{BES III Collaboration\} and M. Ablikim and Achasov, \{M. N.\} and P. Adlarson and X.C. Ai and R. Aliberti and A. Amoroso and Q. An and Nasser Kalantar-Nayestanaki and Myroslav Kavatsyuk",

year = "2026",

month = apr,

day = "22",

doi = "10.1103/bk2n-lgps",

language = "English",

volume = "136",

journal = "Physical Review Letters",

issn = "0031-9007",

publisher = "AMER PHYSICAL SOC",

number = "16",

}

TY - JOUR

T1 - First Measurement of the 𝐷+ 𝑠 →𝐾0⁢𝜇+⁢𝜈𝜇 Decay

AU - BES III Collaboration

AU - Ablikim, M.

AU - Achasov, M. N.

AU - Adlarson, P.

AU - Ai, X.C.

AU - Aliberti, R.

AU - Amoroso, A.

AU - An, Q.

AU - Kalantar-Nayestanaki, Nasser

AU - Kavatsyuk, Myroslav

PY - 2026/4/22

Y1 - 2026/4/22

N2 - We report the first measurement of the semileptonic decay 𝐷+ 𝑠→𝐾0⁢𝜇+⁢𝜈𝜇, using a sample of 𝑒+⁢𝑒− annihilation data corresponding to an integrated luminosity of 7.33 fb−1 collected at center-of-mass energies between 4.128 and 4.226 GeV with the BESIII detector at the BEPCII collider. The branching fraction of the decay is measured to be ℬ⁡(𝐷+ 𝑠→𝐾0⁢𝜇+⁢𝜈𝜇)=(2.89±0.2⁢7stat±0.1⁢2syst)×10−3, where the first uncertainty is statistical and the second is systematic. Based on a simultaneous fit to the partial decay rates in 𝑞2 intervals measured in 𝐷+ 𝑠→𝐾0⁢𝜇+⁢𝜈𝜇 and 𝐷+ 𝑠 →𝐾0⁢𝑒+⁢𝜈𝑒 decays, the product value of the form factor 𝑓𝐾0 +⁡(0) and the Cabibbo-Kobayashi-Maskawa matrix element |𝑉𝑐⁢𝑑| is measured to be 𝑓𝐾0 +⁡(0)⁢|𝑉𝑐⁢𝑑|=0.140±0.00⁢8stat±0.00⁢3syst, which is the most precise determination to date. In addition, lepton flavor universality is tested for the first time with 𝐷+ 𝑠→𝐾0⁢ℓ+⁢𝜈ℓ decays in full and separate 𝑞2 intervals. No violation is found.

AB - We report the first measurement of the semileptonic decay 𝐷+ 𝑠→𝐾0⁢𝜇+⁢𝜈𝜇, using a sample of 𝑒+⁢𝑒− annihilation data corresponding to an integrated luminosity of 7.33 fb−1 collected at center-of-mass energies between 4.128 and 4.226 GeV with the BESIII detector at the BEPCII collider. The branching fraction of the decay is measured to be ℬ⁡(𝐷+ 𝑠→𝐾0⁢𝜇+⁢𝜈𝜇)=(2.89±0.2⁢7stat±0.1⁢2syst)×10−3, where the first uncertainty is statistical and the second is systematic. Based on a simultaneous fit to the partial decay rates in 𝑞2 intervals measured in 𝐷+ 𝑠→𝐾0⁢𝜇+⁢𝜈𝜇 and 𝐷+ 𝑠 →𝐾0⁢𝑒+⁢𝜈𝑒 decays, the product value of the form factor 𝑓𝐾0 +⁡(0) and the Cabibbo-Kobayashi-Maskawa matrix element |𝑉𝑐⁢𝑑| is measured to be 𝑓𝐾0 +⁡(0)⁢|𝑉𝑐⁢𝑑|=0.140±0.00⁢8stat±0.00⁢3syst, which is the most precise determination to date. In addition, lepton flavor universality is tested for the first time with 𝐷+ 𝑠→𝐾0⁢ℓ+⁢𝜈ℓ decays in full and separate 𝑞2 intervals. No violation is found.

U2 - 10.1103/bk2n-lgps

DO - 10.1103/bk2n-lgps

M3 - Article

SN - 0031-9007

VL - 136

JO - Physical Review Letters

JF - Physical Review Letters

IS - 16

M1 - 161802

ER -

First Measurement of the 𝐷+ 𝑠 →𝐾0⁢𝜇+⁢𝜈𝜇 Decay

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