Search for double-beta decay of ¹³⁶Xe to excited states of ¹³⁶Ba with the KamLAND-Zen experiment

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• 作者：K. Asakura^a ; A. Gando^a ; ^{azusa@awa.tohoku.ac.jp" class="auth_mail" title="E-mail the corresponding author} ; Y. Gando^a ; T. Hachiya^a ; S. Hayashida^a ; H. Ikeda^a ; K. Inoue^a ; ^b ; K. Ishidoshiro^a ; T. Ishikawa^a ; S. Ishio^a ; M. Koga^a ; ^b ; S. Matsuda^a ; T. Mitsui^a ; D. Motoki^a ; K. Nakamura^a ; ^b ; S. Obara^a ; M. Otani^a ; ¹ ; T. Oura^a ; I. Shimizu^a ; Y. Shirahata^a ; J. Shirai^a ; A. Suzuki^a ; H. Tachibana^a ; K. Tamae^a ; K. Ueshima^a ; H. Watanabe^a ; B.D. Xu^a ; ² ; H. Yoshida^a ; ³ ; A. Kozlov^b ; Y. Takemoto^b ; S. Yoshida^c ; K. Fushimi^d ; T.I. Banks^e ; B.E. Berger^e ; ^b ; B.K. Fujikawa^e ; ^b ; T. O'Donnell^e ; L.A. Winslow^f ; Y. Efremenko^g ; ^h ; ^b ; H.J. Karwowskiⁱ ; D.M. Markoffⁱ ; W. Tornowⁱ ; ^b ; J.A. Detwiler^j ; ^b ; S. Enomoto^j ; ^b ; M.P. Decowski^k ; ^b
• 关键词：Double-beta decay ; 136Xe ; Excited state
• 刊名：Nuclear Physics A
• 出版年：2016
• 出版时间：February 2016
• 年：2016
• 卷：946
• 期：Complete
• 页码：171-181
• 全文大小：618 K

文摘

A search for double-beta decays of ¹³⁶Xe to excited states of ¹³⁶Ba has been performed with the first phase data set of the KamLAND-Zen experiment. The issn=03759474&md5=3e8d6adf32ae6893e5a1f420ed8ca958">$0_1^{+}$, issn=03759474&md5=5b97f0f3fafd4b39f6e23bbc7130e681">$2_1^{+}$ and issn=03759474&md5=6a73bef336671d668075caec9f321760">$2_2^{+}$ transitions of issn=03759474&md5=c34b03801f7ec0e33a08a1f178821773" title="Click to view the MathML source">0νββ$0\nu \beta \beta$ decay were evaluated in an exposure of issn=03759474&md5=5c1df6e57827ed2dd26b0eb128d9b4a8">$89.5\text{kg}\cdot \text{yr}$ of ¹³⁶Xe, while the same transitions of issn=03759474&md5=8574a6a94c3e4ca037946834f4fa28bc" title="Click to view the MathML source">2νββ$2\nu \beta \beta$ decay were evaluated in an exposure of issn=03759474&md5=0e05e261d4e72ae276048dd21e7785bc">$61.8\text{kg}\cdot \text{yr}$. No excess over background was found for all decay modes. The lower half-life limits of the issn=03759474&md5=5b97f0f3fafd4b39f6e23bbc7130e681">$2_1^{+}$ state transitions of issn=03759474&md5=c34b03801f7ec0e33a08a1f178821773" title="Click to view the MathML source">0νββ$0\nu \beta \beta$ and issn=03759474&md5=8574a6a94c3e4ca037946834f4fa28bc" title="Click to view the MathML source">2νββ$2\nu \beta \beta$ decay were improved to issn=03759474&md5=b4628e9c36c110e1d9be96e29619f686">$T_{1/2}^{0\nu }(0^{+}\to 2_1^{+})>2.6\times {10}^{25}\text{yr}$ and issn=03759474&md5=541315f08115814b9a20f573d91a9a21">$T_{1/2}^{2\nu }(0^{+}\to 2_1^{+})>4.6\times {10}^{23}\text{yr}$ (90% C.L.), respectively. We report on the first experimental lower half-life limits for the transitions to the issn=03759474&md5=3e8d6adf32ae6893e5a1f420ed8ca958">$0_1^{+}$ state of ¹³⁶Xe for issn=03759474&md5=c34b03801f7ec0e33a08a1f178821773" title="Click to view the MathML source">0νββ$0\nu \beta \beta$ and issn=03759474&md5=8574a6a94c3e4ca037946834f4fa28bc" title="Click to view the MathML source">2νββ$2\nu \beta \beta$ decay. They are issn=03759474&md5=efcf6db719ddb553bb9b9bf3dd9da351">$T_{1/2}^{0\nu }(0^{+}\to 0_1^{+})>2.4\times {10}^{25}\text{yr}$ and issn=03759474&md5=1fbdfb4dc5e17b92608c9c4257c54408">$T_{1/2}^{2\nu }(0^{+}\to 0_1^{+})>8.3\times {10}^{23}\text{yr}$ (90% C.L.). The transitions to the issn=03759474&md5=6a73bef336671d668075caec9f321760">$2_2^{+}$ states are also evaluated for the first time to be issn=03759474&md5=a9ff1e7c94aed29982a846cb279bcc0d">$T_{1/2}^{0\nu }(0^{+}\to 2_2^{+})>2.6\times {10}^{25}\text{yr}$ and issn=03759474&md5=c5eaebf4982e5ae29f08c69c415c182d">$T_{1/2}^{2\nu }(0^{+}\to 2_2^{+})>9.0\times {10}^{23}\text{yr}$ (90% C.L.). These results are compared to recent theoretical predictions.