We report the first measurement of the absolute branching fraction for Λ_{c}^{+}→Λe^{+}ν_{e}. This measurement is based on 567 pb^{-1} of e^{+}e^{-} annihilation data produced at sqrts=4.599 GeV, ...which is just above the Λ_{c}^{+}Λover ¯_{c}^{-} threshold. The data were collected with the BESIII detector at the BEPCII storage rings. The branching fraction is determined to be B(Λ_{c}^{+}→Λe^{+}ν_{e})=3.63±0.38(stat)±0.20(syst)%, representing a significant improvement in precision over the current indirect determination. As the branching fraction for Λ_{c}^{+}→Λe^{+}ν_{e} is the benchmark for those of other Λ_{c}^{+} semileptonic channels, our result provides a unique test of different theoretical models, which is the most stringent to date.
This letter describes a technology demonstrator for an incoherent optical code-division multiple-access scheme based on wavelength/time codes. The system supports 16 users operating at 1.25 ...Gsymbols/s/user while maintaining bit-error rate (BER) <10/sup -11/ for the correctly decoded signal. Experiments support previous simulations which show that coherent beat noise, occurring between the signal and multiple access interference, ultimately limits system performance.
The cross sections of e^{+}e^{-}→π^{+}π^{-}h_{c} at center-of-mass energies from 3.896 to 4.600 GeV are measured using data samples collected with the BESIII detector operating at the Beijing ...Electron Positron Collider. The cross sections are found to be of the same order of magnitude as those of e^{+}e^{-}→π^{+}π^{-}J/ψ and e^{+}e^{-}→π^{+}π^{-}ψ(2S), but the line shape is inconsistent with the Y states observed in the latter two modes. Two structures are observed in the e^{+}e^{-}→π^{+}π^{-}h_{c} cross sections around 4.22 and 4.39 GeV/c^{2}, which we call Y(4220) and Y(4390), respectively. A fit with a coherent sum of two Breit-Wigner functions results in a mass of (4218.4_{-4.5}^{+5.5}±0.9) MeV/c^{2} and a width of (66.0_{-8.3}^{+12.3}±0.4) MeV for the Y(4220), and a mass of (4391.5_{-6.8}^{+6.3}±1.0) MeV/c^{2} and a width of (139.5_{-20.6}^{+16.2}±0.6) MeV for the Y(4390), where the first uncertainties are statistical and the second ones systematic. The statistical significance of Y(4220) and Y(4390) is 10σ over one structure assumption.
The exclusive process e+e−→ΛΛ¯, with Λ→pπ− and Λ¯→p¯π+, has been studied at s=2.396 GeV for measurement of the timelike Λ electric and magnetic form factors, GE and GM. A data sample, corresponding ...to an integrated luminosity of 66.9 pb−1, was collected with the BESIII detector for this purpose. A multidimensional analysis with a complete decomposition of the spin structure of the reaction enables a determination of the modulus of the ratio R=|GE/GM| and, for the first time for any baryon, the relative phase ΔΦ=ΦE−ΦM. The resulting values are R=0.96±0.14(stat)±0.02(syst) and ΔΦ=37°±12°(stat)±6°(syst), respectively. These are obtained using the recently established and most precise value of the asymmetry parameter αΛ=0.750±0.010 measured by BESIII. In addition, the cross section is measured with unprecedented precision to be σ=118.7±5.3(stat)±5.1(syst) pb, which corresponds to an effective form factor of |G|=0.123±0.003(stat)±0.003(syst). The contribution from two-photon exchange is found to be negligible. Our result enables the first complete determination of baryon timelike electromagnetic form factors.
Here, in an analysis of a 2.92 fb–1 data sample taken at 3.773 GeV with the BESIII detector operated at the BEPCII collider, we measure the absolute decay branching fractions to be B(D0 → K–e+νe) = ...(3.505 ± 0.014 ± 0.033)% and B(D0 → π–e+νe) = (0.295 ± 0.004 ± 0.003)%. From a study of the differential decay rates we obtain the products of hadronic form factor and the magnitude of the CKM matrix element $f$ $^{K}_{+}$(0)|Vcs| = 0.7172 ± 0.0025 ± 0.0035 and $f$ $^{π}_{+}$(0)|Vcd| = 0.1435 ± 0.0018 ± 0.0009.
Measurements of the center-of-mass energies at BESIII via the di-muon process 麦迪娜 M. N. Achasov X. C. Ai O. Albayrak M. Albrecht D. J. Ambrose A. Amoroso 安芬芬 安琪 白景芝 R. Baldini Ferroli 班勇 D. W. Bennett J. V. Bennett M. Bertani D. Bettoni 边渐鸣 F. Bianchi E. Boger I. Boyko R. A. Briere 蔡浩 蔡啸 O. Cakir A. Calcaterra 曹国富 S. A. Cetin 常劲帆 G. Chelkov 陈刚 陈和生 陈海云 陈江川 陈玛丽 陈申见 谌炫 陈旭荣 陈元柏 程和平 褚新坤 G. Cibinetto 代洪亮 代建平 A. D beyssi D. Dedovich 邓子艳 A. Denig I. Denysenko M Destefanis F. De Mori 丁勇 董超 董静 董燎原 董明义 杜书先 段鹏飞 范荆州 方建 房双世 方馨 方易 L. Fava F. Feldbauer G. Felici 封常青 E. Fioravanti M. Fritsch 傅成栋 高清 高鑫磊 高旭阳 高原宁 高榛 I. Garzia K. Goetzen 龚文煊 W. Gradl M. Greco 顾旻皓 顾运厅 管颖慧 郭爱强 郭立波 郭玥 郭玉萍 Z. Haddadi A. Hafner 韩爽 郝喜庆 F. A. Harris 何康林 T. Held 衡月昆 侯治龙 胡琛 胡海明 胡继峰 胡涛 胡誉 黄光明 黄光顺 黄金书 黄性涛 黄勇 T. Hussain 纪全 姬清平 季晓斌 季筱璐 姜鲁文 江晓山 蒋兴雨 焦健斌 焦铮 金大鹏 金山 T. Johansson A. Julin N. Kalantar-Nayestanaki 康晓琳 康晓珅 M. Kavatsyuk B. C. Ke P.Kiese R. Kliemt B. Kloss O. B. Kolcu B. Kopf M. Kornicer W. Kuhn A. Kupsc J. S. Lange M. Lara P. Larin C. Leng 李翠 李澄 李德民 李飞 李峰云 李刚 李海波 李家才 李瑾 李康 李科 李蕾 李培荣 李腾 李卫东 李卫国 李晓玲 李小梅 李小男 李学潜 李志兵 梁昊 梁勇飞 梁羽铁 廖广睿 D. X. Lin 刘北江 刘春秀 刘栋 刘福虎 刘芳 刘峰 刘宏邦 刘欢欢 刘汇慧 刘怀民 刘杰 刘建北 刘觉平 刘晶译 刘凯 刘魁勇 刘兰雕 刘佩莲 刘倩 刘树彬 刘翔 刘玉斌 刘振安 刘智清 H. Loehner 娄辛丑 吕海江 吕军光 卢宇 卢云鹏 罗成林 罗民兴 T. Luo 罗小兰 吕晓睿 马凤才 马海龙 马连良 马秋梅 马天 马旭宁 马骁妍 F. E. Maas M. Maggiora 冒亚军 毛泽普 S. Marcello J. G. Messchendorp 闵建 R. E. Mitchell 莫晓虎 莫玉俊 C. Morales Morales K. Moriya N. Yu. Muchnoi H. Muramatsu y. Nefedov F. Nerling I. B. Nikolaev 宁哲 S．Nisar 牛顺利 牛讯伊 马鹏 欧阳群 S. Pacetti 潘越 P．Patteri M. Pelizaeus 彭海平 K．Peters J. Pettersson 平加伦 平荣刚 R. Poling V. Prasad 祁鸣 钱森 乔从丰 秦丽清 覃拈 秦小帅 秦中华 邱进发 K. H. Rashid C. F. Redmer M. Ripka 荣刚 Ch. Rosner 阮向东 V. Santoro A. Sarantsev M. Savrie K. Schoennin S. Schumann 单葳 邵明 沈成平 沈培迅 沈肖雁 盛华义 宋维民 宋欣颖 S. Sosio S. Spataro 孙功星 孙俊峰 孙胜森 孙勇杰 孙永昭 孙志嘉 孙振田 唐昌建 唐晓 I. Tapan E. H. Thorndike M. Tiemens M. Ullrich I. Uman G. S. Varner 王斌 王东 王大勇 王科 王亮亮 王灵淑 王萌 王平 王佩良 王思广 王炜 王维平 王雄飞 王雅迪 王贻芳 王亚乾 王铮 王志刚 王志宏 王至勇 T. Weber 魏代会 韦江波 P. Weidenkaff 文硕频 U. Wiedner M. Wolke 伍灵慧 吴智 夏磊 夏力钢 夏宇18 肖栋 肖浩 肖振军 谢宇广 修青磊 许国发 徐雷 徐庆君 徐新平 严亮 鄢文标 闫文成 颜永红 杨海军 杨洪勋 杨柳 杨迎 杨永栩 叶梅 叶铭汉 殷俊昊 俞伯祥 喻纯旭 俞浩晟 苑长征 袁文龙 袁野 A. Yuncu A. A. Zafar A.Zallo 曾云 曾哲 张丙新 张炳云 张弛29 张长春 张达华 张宏浩 章红宇 张佳佳 张杰磊 张敬庆 张家文 张建勇 张景芝 张坤 张磊 张学尧 张瑶 张宇宁 张银鸿 张亚腾 张宇 张正好 张子平 张振宇 赵光 赵京伟 赵静宜 赵京周 赵雷 赵玲 赵明刚 赵强 赵庆旺 赵书俊 赵天玲 赵天池 赵豫斌 赵政国 A. Zhemchugov 郑波 郑建平 郑文静 郑阳恒 钟彬 周莉 周详 周晓康 周小蓉 周注玉 朱凯 朱科军 朱帅 朱世海 朱相雷 朱莹春 朱永生 朱自安 庄建 L．Zotti 邹冰松 邹佳恒
Chinese physics C,
06/2016, Letnik:
40, Številka:
6
Journal Article
Recenzirano
Odprti dostop
From 2011 to 2014, the BESIII experiment collected about 5 fb^-1 data at center-of-mass energies around 4 GeV for the studies of the charmonium-like and higher excited charmonium states. By analyzing ...the di-muon process e＋e- →yma/Fsμ^＋μ^-, the center-of-mass energies of the data samples are measured with a precision of 0.8 MeV. The center-of-mass energy is found to be stable for most of the time during data taking.
B-flavor tagging at Belle II Akopov, N.; Banerjee, Sw; Bauer, M. ...
The European physical journal. C, Particles and fields,
04/2022, Letnik:
82, Številka:
4
Journal Article
Recenzirano
Odprti dostop
We report on new flavor tagging algorithms developed to determine the quark-flavor content of bottom (
) mesons at Belle II. The algorithms provide essential inputs for measurements of quark-flavor ...mixing and charge-parity violation. We validate and evaluate the performance of the algorithms using hadronic
decays with flavor-specific final states reconstructed in a data set corresponding to an integrated luminosity of 62.8 fb
-
1
, collected at the
resonance with the Belle II detector at the SuperKEKB collider. We measure the total effective tagging efficiency to be
ε
eff
=
(
30.0
±
1.2
(
stat
)
±
0.4
(
syst
)
)
%
for a category-based algorithm and
ε
eff
=
(
28.8
±
1.2
(
stat
)
±
0.4
(
syst
)
)
%
for a deep-learning-based algorithm.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Using a total of 11.0 fb^{-1} of e^{+}e^{-} collision data with center-of-mass energies between 4.009 and 4.6 GeV and collected with the BESIII detector at BEPCII, we measure fifteen exclusive cross ...sections and effective form factors for the process e^{+}e^{-}→Ξ^{-}Ξover ¯^{+} by means of a single baryon-tag method. After performing a fit to the dressed cross section of e^{+}e^{-}→Ξ^{-}Ξover ¯^{+}, no significant ψ(4230) or ψ(4260) resonance is observed in the Ξ^{-}Ξover ¯^{+} final states, and upper limits at the 90% confidence level on Γ_{ee}B for the processes ψ(4230)/ψ(4260)→Ξ^{-}Ξover ¯^{+} are determined. In addition, an excited Ξ baryon at 1820 MeV/c^{2} is observed with a statistical significance of 6.2-6.5σ by including the systematic uncertainty, and the mass and width are measured to be M=(1825.5±4.7±4.7) MeV/c^{2} and Γ=(17.0±15.0±7.9) MeV, which confirms the existence of the J^{P}=3/2^{-} state Ξ(1820).
We present the first measurement of the ratio of branching fractions of inclusive semileptonic $B$-meson decays, $R(X_{e/\mu}) = \mathcal{B}(B\to X \, e \, \nu) / \mathcal{B}(B\to X \, \mu \, \nu)$, ...a precision test of electron-muon universality, using data corresponding to $189\,\mathrm{fb}^{-1}$ from electron-positron collisions collected with the Belle II detector. In events where the partner $B$ meson is fully reconstructed, we use fits to the lepton momentum spectra above $1.3\,\mathrm{GeV}/c$ to obtain $R(X_{e/\mu}) = 1.007 \pm 0.009~(\mathrm{stat}) \pm 0.019~(\mathrm{syst})$, which is the most precise lepton-universality test of its kind and agrees with the standard-model expectation.
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