$2νββ$ decay of $^{76}$Ge into excited states with GERDA Phase I
M. Agostini, M. Allardt, A. M. Bakalyarov, M. Balata, I. Barabanov, N. Barros, L. Baudis, C. Bauer, N. Becerici-Schmidt, E. Bellotti, S. Belogurov, S. T. Belyae… 展开作者
M. Agostini, M. Allardt, A. M. Bakalyarov, M. Balata, I. Barabanov, N. Barros, L. Baudis, C. Bauer, N. Becerici-Schmidt, E. Bellotti, S. Belogurov, S. T. Belyaev, G. Benato, A. Bettini, L. Bezrukov, T. Bode, D. Borowicz, V. Brudanin, R. Brugnera, D. Budjáš, A. Caldwell, C. Cattadori, A. Chernogorov, V. D'Andrea, E. V. Demidova, A. di Vacri, A. Domula, E. Doroshkevich, V. Egorov, R. Falkenstein, O. Fedorova, K. Freund, N. Frodyma, A. Gangapshev, A. Garfagnini, C. Gooch, P. Grabmayr, V. Gurentsov, K. Gusev, A. Hegai, M. Heisel, S. Hemmer, G. Heusser, W. Hofmann, M. Hult, L. V. Inzhechik, J. Janicskó Csáthy, J. Jochum, M. Junker, V. Kazalov, T. Kihm, I. V. Kirpichnikov, A. Kirsch, A. Klimenko, K. T. Knöpfle, O. Kochetov, V. N. Kornoukhov, V. V. Kuzminov, M. Laubenstein, A. Lazzaro, V. I. Lebedev, B. Lehnert, H. Y. Liao, M. Lindner, I. Lippi, A. Lubashevskiy, B. Lubsandorzhiev, G. Lutter, C. Macolino, B. Majorovits, W. Maneschg, E. Medinaceli, Y. Mi, M. Misiaszek, P. Moseev, I. Nemchenok, D. Palioselitis, K. Panas, L. Pandola, K. Pelczar, A. Pullia, S. Riboldi, N. Rumyantseva, C. Sada, M. Salathe, C. Schmitt, B. Schneider, J. Schreiner, O. Schulz, B. Schwingenheuer, S. Schönert, A-K. Schütz, O. Selivanenko, M. Shirchenko, H. Simgen, A. Smolnikov, L. Stanco, M. Stepaniuk, C. A. Ur, L. Vanhoefer, A. A. Vasenko, A. Veresnikova, K. von Sturm, V. Wagner, M. Walter, A. Wegmann, T. Wester, H. Wilsenach, M. Wojcik, E. Yanovich, P. Zavarise, I. Zhitnikov, S. V. Zhukov, D. Zinatulina, K. Zuber, G. Zuzel
Two neutrino double beta decay of $^{76}$Ge to excited states of $^{76}$Se has been studied using data from Phase I of the GERDA experiment. An array composed of up to 14 germanium detectors including detectors that have been isotopically enriched in $^{76}$Ge was deployed in liquid argon. The analysis of various possible transitions to excited final states is based on coincidence events between pairs of detectors where a de-excitation $γ$ ray is detected in one detector and the two electrons in the other.
No signal has been observed and an event counting profile likelihood analysis has been used to determine Frequentist 90\,\% C.L. bounds for three transitions: ${0^+_{\rm g.s.}-2^+_1}$: $T^{2ν}_{1/2}>$1.6$\cdot10^{23}$ yr, ${0^+_{\rm g.s.}-0^+_1}$: $T^{2ν}_{1/2}>$3.7$\cdot10^{23}$ yr and ${0^+_{\rm g.s.}-2^+_2}$: $T^{2ν}_{1/2}>$2.3$\cdot10^{23}$ yr. These bounds are more than two orders of magnitude larger than those reported previously. Bayesian 90\,\% credibility bounds were extracted and used to exclude several models for the ${0^+_{\rm g.s.}-0^+_1}$ transition.
Results on neutrinoless double beta decay from GERDA Phase I
锗探测器阵列（GERDA）是用于探测$^{76}$ Ge的无中微子双β（0 $νββ$）衰变的探测器，它安装在意大利INFN的国立大萨索实验室（LNGS）。本文介绍了GERDA的探测原理和探测器设置。并对GERDA第一阶段的主要物理结果进行了讨论。它们包括测量2 $νββ$衰变的半衰期、能谱的背景分解和根据信号的脉冲形状辨别背景的技术。在本文的最后一部分，我们估计了0-$νββ$的半衰期（$T^{0ν}_{1/2} >2.1\cdot 10^{25}$ yr at 90% C. L.）并与前人的结果进行了比较。来自第一阶段的GERDA数据强烈反对最近基于海德堡-莫斯科实验数据发现0 $νββ$的说法。
Final Results of GERDA on the Search for Neutrinoless Double-$β$ Decay
锗探测器阵列（GERDA）实验寻找$^{76}$ Ge的轻子数破坏的无中微子双$β$（$0νββ$）衰变，其发现将在宇宙学和粒子物理学中产生深远的影响。通过在有源液氩屏蔽中操作富含$^{76}$ Ge的裸锗二极管，GERDA在信号区实现了前所未有的低本底指数$5.2\times10^{-4}$计数/（keV $\cdot$ kg $\cdot$ yr），并满足了在无本底状态下收集100 kg $\cdot$ yr暴露量的设计目标。当结合第一阶段的结果时，在127.2 kg $\cdot$/年的总暴露量后未观察到信号。$^{76}$ Ge中$0νββ$衰变半衰期的限值设定为90% C.L.时的$T_{1/2}>1.8\times10^{26}$年，这与假定没有信号时的灵敏度一致。
Pulse shape discrimination performance of Inverted Coaxial Ge detectors
我们报告的两个倒置的同轴锗探测器的特性的背景下，在未来的$^{76}$锗无中微子双β（$0νββ$）衰变实验。与目前在GERDA $0νββ$衰变实验中使用的平面宽能Ge探测器（BEGe）相比，这样的探测器可以用更大的Ge质量来生产，这是一个优点。由于电缆、电子器件和支架的减少，这将导致搜索$0νββ$衰减的背景降低。在$^{76}$ Ge Q值附近的2039 keV测量分辨率为2.5 keV，它们的脉冲形状特性与BEGe探测器相似。得出的结论是，这种类型的Ge探测器适合用于$^{76}$ Ge $0νββ$衰变实验。
Exclusive semileptonic B decays to radially excited D mesons
在一级重夸克展开下研究了B衰变到径向激发粲介子的排斥性半轻子衰变。在相对论夸克模型的框架下计算了产生的主导和次主导Isgur-Wise函数。发现1/mQ修正起着重要的作用，并对结果有很大的修正。结果表明，不同修正量之间存在着一种有趣的相互作用，1/m_Q修正量使B-> D 'e ν衰变的分支比显著增加，而对B-> D' e ν衰变的分支比影响很小。
