A Method of Combined D0 and D+ Single and Double Tags to Measure Their Branching Fractions and Its Application

  • A method of combined D0 and D+ single and double tags to measure their branching fractions is reported. With this method, we can measure the inclusive and exclusive branching fractions of D0 and D+ based on the data taken at s=4.03GeV using BES detector at BEPC collider. As well known, it is very difficult to study D physics with the data taken at s=4.03GeV. Compared with the data taken at s=3.77GeV, where it is just at the threshold of the pure pairs of D+D and D0D0 productions. While at s=4.03 GeV D* and D*D* can also be produced and then the so-called contaminated final states D+D0 and DD0 can be produced via the cascade decays of the D*+ to charged and neutral D. This makes some trouble for the study. The key to solve this problem is how to determine the ratios β, which denotes the recoil D0 production agaist the tagged D+, and η, which denotes the recoil D production agaist the tagged D0. We developed the double tag method and single tag method to determine these two parameters, and compared them with cross section method developed by us before. They are consistent with each other within errors, so that the validity of this method was proved. As an example of its application, we set the upper limit for D+→e+ν decay to be Br(D+→e+ν)<1.6% at 90% C. L.. This value is consistent with that BES Collaboration published.
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  • [1] . BAI Jing-Zhi et al. N. I. M., 1994. A344: 319-334; DING Hui-Liang et al. HEP NP, 1992. 16(9): 669 (in Chinese)丁慧良等.高能物理与核物理,1992,16(9):669)2. RONG Gang. Recent Perliminary Results on D Meson Decays from BES. In: Alan Astbury, Proceedings of the 29th International Conferenceon High Energy Physics(VolumeⅡ), Vancouver, Canada: World Scientific, 1998. 1242—12463. LUO Chun-Hui. Determination of the Branching Fractions for 上 D0(D+)→K± X Based on the Data Taken at √s=4.03GeV. Master Thesis, Institute of High Energy Physics, The Chinese Academy of Sciences, 1997(in Chinese)(罗春晖. 在4.03GeV能量上D0(D+)→K± X 衰变分支比的确定. 硕士论文, 中国科学院高能物理研究所, 1997) 4. XU Chun-Cheng. Study of Inclusive Semi-Leptonic(μ)Decays of D Mesons. PhD. Thesis, Institute of High Energy Physics, The Chinese Academy of Sciences, 1997(in Chinese)(徐春成. D介子的单举μ子半轻子衰变的研究. 博士论文, 中国科学院高能物理研究所, 1997)5. HENG Yue-Kun, RONG Gang, YAN Wu-Guang. Measurement of the Branching Fractions for the Decays D0→K– e+ ν and D0→π– e+ν. In: Proceedings of the Chinese National Conferenceon High Energy Physics, Chengde, 1999. 274(in Chinese); (衡月昆, 荣刚, 严武光. D0→K– e+ν和D0→π– e+ν 的分支比的测量. 见: 高能物理学会第五届会员代表大会暨全国高能物理大会会议集, 承德, 1998, 274)HENG Yue-Kun. Study of the Exclusive Semi-Leptonic Decays of D Mesons. PhD. Thesis, Institute of High Energy Physics, The Chinese Academy of Sciences, 1999(in Chinese)(衡月昆. D介子的遍举半轻子衰变的研究. 博士论文, 中国科学院高能物理研究所, 1999)6. ZHAO Jia-Wei, RONG Gang, CHEN Hong-Fang. Measurement of Inclusive Semi-Leptonic(electronic)Decay Branching Fractions of D0 and D+. In: Proceedings of the Chinese National Conferenceon High Energy Physics, Chengde, 1999, 291(in Chinese); (赵家伟, 荣刚, 陈宏芳. D0, D+介子单举半轻子(电子)衰变分支比的测量. 见: 高能物理学会第五届会员代表大会暨全国高能物理大会会议集, 承德, 1998, 219)ZHAO Jia-Wei. Test of QED with the Rections of e+ e–→γγ(γ)at LEP2000 and Study of the Inclusive Semi-Leptonic Decays of D0 and D+ Mesons at BES. PhD. Thesis, University of Science and Technology of China, 2001(in Chinese)(赵家伟. 在LEP2000上利用e+ e–→γγ(γ)反应检验QED以及在北京谱仪上D介子单举半轻子衰变的研究. 博士论文, 中国科学技术大学, 2001)7. RONG Gang(BES Collab.). Recent Results on Study of D Physics from BES. In: Proceedings of the Chinese National Confer enceon High Energy Physics, Chengde, 1999, 68—79(in Chinese)(荣刚(BES合作组). 北京谱仪D物理研究的近期结果. 见: 高能物理学会第五届会员代表大会暨全国高能物理大会会议集. 承德, 1998, 68—79)8. BAI Jing-Zhi et al. HEP NP, to be published(in Chinese)(白景芝等. 高能物理与核物理, 待发表)9. Baltrusaitis R M et al(MARK-Ⅲ Collab.). PRL, 1995, 54: 1976; BAI Jing-Zhi et al(BES Collab.). PRD, 1997, 56: 377910. BAI Jing-Zhi et al(BES Collab.). PRD, 2000, 62: 05200111. Particle Data Group. The European Physical Journal C, 2000, 15: 1—4 12. ZHAO Hai-Wen, YAN Wu-Guang, MAO Hui-Shun. Mesurement of the D (2010)Branching Fractions and D Meson Prduction Cross sectionin e+ e–Annihilation at Ec.m=4.03GeV. In: Proceedings of the 5th BES Annual Meeting, Zhang jia-jie, Hunan, June1996, 229—23913. RONG Gang, LUO Chun-Hui, YAN Wu-Guang. Measurement of Inclusivedecay Branching Fractions o fD+(D0)Mesons and Search for D+→e+ν. In: Proceedings of the 5th Annual Meeting, Zhang jia-jie, Hunan, June1996, 131—143; RONG Gang, YAN Wu-Guang, XU Chun-Cheng et al. Study of K0 and K 0 Inclusive Decays of D+(D0)Mesons at √s=4.03GeV .In: Proceedings of the 5th Annual Meeting, Zhang jia-jie, Hunan, June1996, 143—148
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RONG Gang, ZHAO Jia-Wei, LUO Chun-Hui, YAN Wu-Guang, XU Chun-Cheng, ZHANG Da-Hua, HENG Yue-Kun, HE Kang-Lin, ZHAO Hai-Wen, MAO Hui-Shun, MA Ji-Mao, CHEN Hong-Fang and ZHANG Chun. A Method of Combined D0 and D+ Single and Double Tags to Measure Their Branching Fractions and Its Application[J]. Chinese Physics C, 2002, 26(3): 207-215.
RONG Gang, ZHAO Jia-Wei, LUO Chun-Hui, YAN Wu-Guang, XU Chun-Cheng, ZHANG Da-Hua, HENG Yue-Kun, HE Kang-Lin, ZHAO Hai-Wen, MAO Hui-Shun, MA Ji-Mao, CHEN Hong-Fang and ZHANG Chun. A Method of Combined D0 and D+ Single and Double Tags to Measure Their Branching Fractions and Its Application[J]. Chinese Physics C, 2002, 26(3): 207-215. shu
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A Method of Combined D0 and D+ Single and Double Tags to Measure Their Branching Fractions and Its Application

    Corresponding author: RONG Gang,
  • Institute of High Energy Physics, CAS, Beijing 100039, China1 Department of Modern Physics, University of Science and Technology of China, Hefei 230027, China

Abstract: A method of combined D0 and D+ single and double tags to measure their branching fractions is reported. With this method, we can measure the inclusive and exclusive branching fractions of D0 and D+ based on the data taken at s=4.03GeV using BES detector at BEPC collider. As well known, it is very difficult to study D physics with the data taken at s=4.03GeV. Compared with the data taken at s=3.77GeV, where it is just at the threshold of the pure pairs of D+D and D0D0 productions. While at s=4.03 GeV D* and D*D* can also be produced and then the so-called contaminated final states D+D0 and DD0 can be produced via the cascade decays of the D*+ to charged and neutral D. This makes some trouble for the study. The key to solve this problem is how to determine the ratios β, which denotes the recoil D0 production agaist the tagged D+, and η, which denotes the recoil D production agaist the tagged D0. We developed the double tag method and single tag method to determine these two parameters, and compared them with cross section method developed by us before. They are consistent with each other within errors, so that the validity of this method was proved. As an example of its application, we set the upper limit for D+→e+ν decay to be Br(D+→e+ν)<1.6% at 90% C. L.. This value is consistent with that BES Collaboration published.

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