Improved search for ψ(3770) → γη_c(1S, 2S) radiative transitions

@misc{collaboration2026improved,
  title = {{Improved search for $ψ(3770) \to γη_c(1S, 2S)$ radiative transitions}},
  author = {BESIII Collaboration and M. Ablikim and M. N. Achasov and P. Adlarson and X. C. Ai and C. S. Akondi and R. Aliberti and A. Amoroso and Q. An and Y. H. An and M. S. Anderson and Y. Bai and O. Bakina and H. R. Bao and X. L. Bao and M. Barbagiovanni and V. Batozskaya and K. Begzsuren and N. Berger and M. Berlowski and M. B. Bertani and D. Bettoni and F. Bianchi and E. Bianco and A. Bortone and I. Boyko and R. A. Briere and A. Brueggemann and D. Cabiati and H. Cai and M. H. Cai and X. Cai and A. Calcaterra and G. F. Cao and N. Cao and S. A. Cetin and X. Y. Chai and J. F. Chang and T. T. Chang and G. R. Che and Y. Z. Che and C. H. Chen and Chao Chen and G. Chen and H. S. Chen and H. Y. Chen and M. L. Chen and S. J. Chen and S. M. Chen and T. Chen and W. Chen and X. R. Chen and X. T. Chen and X. Y. Chen and Y. B. Chen and Y. Q. Chen and Z. K. Chen and J. Cheng and L. N. Cheng and S. K. Choi},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.33606},
  eprint = {2609.33606},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.33606},
  note = {CC BY 4.0},
}

TY  - UNPB
TI  - Improved search for ψ(3770) → γη_c(1S, 2S) radiative transitions
AU  - BESIII Collaboration
AU  - M. Ablikim
AU  - M. N. Achasov
AU  - P. Adlarson
AU  - X. C. Ai
AU  - C. S. Akondi
AU  - R. Aliberti
AU  - A. Amoroso
AU  - Q. An
AU  - Y. H. An
AU  - M. S. Anderson
AU  - Y. Bai
AU  - O. Bakina
AU  - H. R. Bao
AU  - X. L. Bao
AU  - M. Barbagiovanni
AU  - V. Batozskaya
AU  - K. Begzsuren
AU  - N. Berger
AU  - M. Berlowski
AU  - M. B. Bertani
AU  - D. Bettoni
AU  - F. Bianchi
AU  - E. Bianco
AU  - A. Bortone
AU  - I. Boyko
AU  - R. A. Briere
AU  - A. Brueggemann
AU  - D. Cabiati
AU  - H. Cai
AU  - M. H. Cai
AU  - X. Cai
AU  - A. Calcaterra
AU  - G. F. Cao
AU  - N. Cao
AU  - S. A. Cetin
AU  - X. Y. Chai
AU  - J. F. Chang
AU  - T. T. Chang
AU  - G. R. Che
AU  - Y. Z. Che
AU  - C. H. Chen
AU  - Chao Chen
AU  - G. Chen
AU  - H. S. Chen
AU  - H. Y. Chen
AU  - M. L. Chen
AU  - S. J. Chen
AU  - S. M. Chen
AU  - T. Chen
AU  - W. Chen
AU  - X. R. Chen
AU  - X. T. Chen
AU  - X. Y. Chen
AU  - Y. B. Chen
AU  - Y. Q. Chen
AU  - Z. K. Chen
AU  - J. Cheng
AU  - L. N. Cheng
AU  - S. K. Choi
PY  - 2026
DA  - 2026/09/27
PB  - arXiv
DO  - 10.48550/arxiv.2609.33606
UR  - https://arxiv.org/abs/2609.33606
AB  - Based on an integrated luminosity of 20.3 fb^−1 of e^+e^− annihilation data collected at a center-of-mass energy of 3.773 GeV with the BESIII detector operating at the BEPCII collider, an improved search for the radiative transitions ψ(3770) → γη_c(1S, 2S) is performed using the hadronic decays η_c(1S, 2S) → K^0_S K^± π^∓. No significant signal is observed. The corresponding 90% confidence level upper limits on the product branching fractions are set to be 5.0 × 10^−6 for the η_c(1S) transition and 3.7 × 10^−6 for the η_c(2S) transition. The 90% confidence level upper limits on the partial decay widths are also reported to be Γ(ψ(3770) → γη_c(1S)) < 5.5 keV and Γ(ψ(3770) → γη_c(2S)) < 29.4 keV. With about seven times larger integrated luminosity than used previously, these results lower the upper limits by approximately a factor of three and two for the η_c(1S) and η_c(2S) transitions, respectively.
ER  -