Eur. Phys. J. C (2020) 80: 935
https://doi.org/10.1140/epjc/s10052-020-08447-0

Regular Article - Experimental Physics

Measurement of the absolute branching fraction of the inclusive decay ${\mathrm{\Lambda }}_c^{+}\to K_S^{0}X$

(BESIII Collaboration)

¹ Institute of High Energy Physics, 100049, Beijing, People’s Republic of China
² Beihang University, 100191, Beijing, People’s Republic of China
³ Beijing Institute of Petrochemical Technology, 102617, Beijing, People’s Republic of China
⁴ Bochum Ruhr-University, 44780, Bochum, Germany
⁵ Carnegie Mellon University, 15213, Pittsburgh, PA, USA
⁶ Central China Normal University, 430079, Wuhan, People’s Republic of China
⁷ China Center of Advanced Science and Technology, 100190, Beijing, People’s Republic of China
⁸ COMSATS University Islamabad, Lahore Campus, Defence Road, Off Raiwind Road, 54000, Lahore, Pakistan
⁹ Fudan University, 200443, Shanghai, People’s Republic of China
¹⁰ G.I. Budker Institute of Nuclear Physics SB RAS (BINP), 630090, Novosibirsk, Russia
¹¹ GSI Helmholtz Centre for Heavy Ion Research GmbH, 64291, Darmstadt, Germany
¹² Guangxi Normal University, 541004, Guilin, People’s Republic of China
¹³ Guangxi University, 530004, Nanning, People’s Republic of China
¹⁴ Hangzhou Normal University, 310036, Hangzhou, People’s Republic of China
¹⁵ Helmholtz Institute Mainz, Johann-Joachim-Becher-Weg 45, 55099, Mainz, Germany
¹⁶ Henan Normal University, 453007, Xinxiang, People’s Republic of China
¹⁷ Henan University of Science and Technology, 471003, Luoyang, People’s Republic of China
¹⁸ Huangshan College, 245000, Huangshan, People’s Republic of China
¹⁹ Hunan Normal University, 410081, Changsha, People’s Republic of China
²⁰ Hunan University, 410082, Changsha, People’s Republic of China
²¹ Indian Institute of Technology Madras, 600036, Chennai, India
²² Indiana University, 47405, Bloomington, IN, USA
²³ INFN Laboratori Nazionali di Frascati, 00044 Frascati, Italy; INFN and University of Perugia, 06100, Perugia, Italy
²⁴ INFN Sezione di Ferrara, 44122 Ferrara, Italy; University of Ferrara, 44122, Ferrara, Italy
²⁵ Institute of Modern Physics, 730000, Lanzhou, People’s Republic of China
²⁶ Institute of Physics and Technology, Peace Ave. 54B, 13330, Ulaanbaatar, Mongolia
²⁷ Jilin University, 130012, Changchun, People’s Republic of China
²⁸ Johannes Gutenberg University of Mainz, Johann-Joachim-Becher-Weg 45, 55099, Mainz, Germany
²⁹ Joint Institute for Nuclear Research, 141980, Dubna, Moscow Region, Russia
³⁰ Justus-Liebig-Universitaet Giessen, II. Physikalisches Institut, Heinrich-Buff-Ring 16, 35392, Giessen, Germany
³¹ KVI-CART, University of Groningen, 9747 AA, Groningen, The Netherlands
³² Lanzhou University, 730000, Lanzhou, People’s Republic of China
³³ Liaoning Normal University, 116029, Dalian, People’s Republic of China
³⁴ Liaoning University, 110036, Shenyang, People’s Republic of China
³⁵ Nanjing Normal University, 210023, Nanjing, People’s Republic of China
³⁶ Nanjing University, 210093, Nanjing, People’s Republic of China
³⁷ Nankai University, 300071, Tianjin, People’s Republic of China
³⁸ Peking University, 100871, Beijing, People’s Republic of China
³⁹ Qufu Normal University, 273165, Qufu, People’s Republic of China
⁴⁰ Shandong Normal University, 250014, Jinan, People’s Republic of China
⁴¹ Shandong University, 250100, Jinan, People’s Republic of China
⁴² Shanghai Jiao Tong University, 200240, Shanghai, People’s Republic of China
⁴³ Shanxi Normal University, 041004, Linfen, People’s Republic of China
⁴⁴ Shanxi University, 030006, Taiyuan, People’s Republic of China
⁴⁵ Sichuan University, 610064, Chengdu, People’s Republic of China
⁴⁶ Soochow University, 215006, Suzhou, People’s Republic of China
⁴⁷ Southeast University, 211100, Nanjing, People’s Republic of China
⁴⁸ State Key Laboratory of Particle Detection and Electronics, Beijing 100049, 230026, Hefei, People’s Republic of China
⁴⁹ Sun Yat-Sen University, 510275, Guangzhou, People’s Republic of China
⁵⁰ Tsinghua University, 100084, Beijing, People’s Republic of China
⁵¹ Ankara University, Tandogan, 06100 Ankara, Turkey; Istanbul Bilgi University, 34060 Eyup, Istanbul, Turkey; Uludag University, 16059 Bursa, Turkey; Near East University, Mersin 10, Nicosia, North Cyprus, Turkey
⁵² University of Chinese Academy of Sciences, 100049, Beijing, People’s Republic of China
⁵³ University of Hawaii, 96822, Honolulu, HI, USA
⁵⁴ University of Jinan, 250022, Jinan, People’s Republic of China
⁵⁵ University of Manchester, Oxford Road, M13 9PL, Manchester, UK
⁵⁶ University of Minnesota, 55455, Minneapolis, MN, USA
⁵⁷ University of Muenster, Wilhelm-Klemm-Str. 9, 48149, Münster, Germany
⁵⁸ University of Oxford, Keble Rd, OX13RH, Oxford, UK
⁵⁹ University of Science and Technology Liaoning, 114051, Anshan, People’s Republic of China
⁶⁰ University of Science and Technology of China, 230026, Hefei, People’s Republic of China
⁶¹ University of South China, 421001, Hengyang, People’s Republic of China
⁶² University of the Punjab, 54590, Lahore, Pakistan
⁶³ University of Turin, 10125 Turin, Italy; University of Eastern Piedmont, 15121 Alessandria, Italy; INFN, 10125, Turin, Italy
⁶⁴ Uppsala University, Box 516, 75120, Uppsala, Sweden
⁶⁵ Wuhan University, 430072, Wuhan, People’s Republic of China
⁶⁶ Xinyang Normal University, 464000, Xinyang, People’s Republic of China
⁶⁷ Zhejiang University, 310027, Hangzhou, People’s Republic of China
⁶⁸ Zhengzhou University, 450001, Zhengzhou, People’s Republic of China

^ra wangbin@ihep.ac.cn

Received: 22 May 2020
Accepted: 8 September 2020
Published online: 10 October 2020

Abstract

We report the first measurement of the absolute branching fraction of the inclusive decay ${\mathrm{\Lambda }}_c^{+}\to K_S^{0}X$. The analysis is performed using an $e^{+}{e}^{-}$ collision data sample corresponding to an integrated luminosity of 567 ${\text{pb}}^{-1}$ taken at $\sqrt{s}$ = 4.6 GeV with the BESIII detector. Using eleven Cabibbo-favored ${\overline{\mathrm{\Lambda }}}_c^{-}$ decay modes and the double-tag technique, this absolute branching fraction is measured to be $\mathcal{B}({\mathrm{\Lambda }}_c^{+}\to K_S^{0}X)=(9.9\pm 0.6\pm 0.4)\%$, where the first uncertainty is statistical and the second systematic. The relative deviation between the branching fractions for the inclusive decay and the observed exclusive decays is $(18.7\pm 8.3)\%$, which indicates that there may be some unobserved decay modes with a neutron or excited baryons in the final state.