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 01+, 21+ and 22+ transitions of 0νββ decay were ...evaluated in an exposure of 89.5 kg⋅yr of 136Xe, while the same transitions of 2νββ decay were evaluated in an exposure of 61.8 kg⋅yr. No excess over background was found for all decay modes. The lower half-life limits of the 21+ state transitions of 0νββ and 2νββ decay were improved to T1/20ν(0+→21+)>2.6×1025 yr and T1/22ν(0+→21+)>4.6×1023 yr (90% C.L.), respectively. We report on the first experimental lower half-life limits for the transitions to the 01+ state of 136Xe for 0νββ and 2νββ decay. They are T1/20ν(0+→01+)>2.4×1025 yr and T1/22ν(0+→01+)>8.3×1023 yr (90% C.L.). The transitions to the 22+ states are also evaluated for the first time to be T1/20ν(0+→22+)>2.6×1025 yr and T1/22ν(0+→22+)>9.0×1023 yr (90% C.L.). These results are compared to recent theoretical predictions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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 01+ , 21+ and 22+ transitions of 0νββ decay ...were evaluated in an exposure of 89.5 kg•yr of 136Xe, while the same transitions of 2νββ decay were evaluated in an exposure of 61.8 kg•yr. No excess over background was found for all decay modes. The lower half-life limits of the 21+ state transitions of 0νββ and 2νββ decay were improved to T$0v\atop{1/2}$(0+ →21+) > 2.6×1025 yr and T$2v\atop{1/2}$ (0+ →21+) > 4.6×1023 yr (90% C.L.), respectively. We report on the first experimental lower half-life limits for the transitions to the 01+ state of 136Xe for 0νββ and 2νββ decay. They are T$0v\atop{1/2}$(0+ →01+) > 2.4×1025 yr and T$2v\atop{1/2}$(0+ →01+) > 8.3×1023 yr (90% C.L.). The transitions to the 22+ states are also evaluated for the first time to be T$0v\atop{1/2}$(0+ →22+) > 2.6×1025 yr and T$2v\atop{1/2}$(0+ →22+) > 9.0×1023 yr (90% C.L.). Finally, these results are compared to recent theoretical predictions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
B-modes are special patterns in cosmic microwave background (CMB) polarization. Degree-scale B-modes are smoking-gun signatures of primordial gravitational waves. The generic strategy of CMB ...polarization experiments is to employ a large number of polarimeters for improving the statistics. The Q/U Imaging ExperimenT-II (QUIET-II) has been proposed to detect B-modes by using the world's largest coherent polarimeter array (2,000 channels). A unique detection technique using QUIET's polarimeters, which comprises a modulation/demodulation scheme, enables us to directly extract polarization signals. The extracted signals are free from unpolarized components and intrinsic 1/f noise. We developed a data readout system for the QUIET-II experiment. We employed a "master" clock strategy, on-board demodulation functions, and end-to-end Ethernet connections for logical simplicity and high-density compact electronics for physical compactness. A clock module acts as a single master and guarantees phase matching between the modulation by the polarimeters and the on-board demodulation by ADC modules. Each ADC module has 64 ADC chips in the VME-6U single slot size. Both modules have hardware processors for Ethernet TCP/UDP. All these modules and control computers are connected via end-to-end Ethernet. Physical compactness and logical simplicity enable us to easily handle a large number of polarimeters, while maintaining quality of the B-mode experiments. The developed electronics (the clock modules and the ADC modules) fulfill these requirements. Tests with a setup similar to that of the real experiment proved that the system works appropriately. The performance of all system components is validated to be suitable for B-mode measurements.
We report a measurement of the neutrino-electron elastic scattering rate of 862 keV 7Be solar neutrinos based on a 165.4 kt d exposure of KamLAND. The observed rate is 582±94(kt d)₋1, which ...corresponds to an 862-keV 7Be solar neutrino flux of (3.26±0.52)×109cm₋2s₋1, assuming a pure electron-flavor flux. Comparing this flux with the standard solar model prediction and further assuming three-flavor mixing, a νe survival probability of 0.66±0.15 is determined from the KamLAND data. Lastly, utilizing a global three-flavor oscillation analysis, we obtain a total 7Be solar neutrino flux of (5.82±1.02)×109cm₋2s₋1, which is consistent with the standard solar model predictions.
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(ProQuest: ... denotes formulae and/or non-USASCII text omitted) The recent long-term shutdown of Japanese nuclear reactors has resulted in a significantly reduced reactor nu sub(e) flux at KamLAND. ...This running condition provides a unique opportunity to confirm and constrain backgrounds for the reactor nu sub(e) oscillation analysis. The data set also has improved sensitivity for other nu sub(e) signals, in particular nu sub(e)'s produced in beta -decays from super(238)U and super(232)Th within the Earth's interior, whose energy spectrum overlaps with that of reactor nu sub(e)'s. Including constraints on theta sub(13) from accelerator and short-baseline reactor neutrino experiments, a combined three-flavor analysis of solar and KamLAND data gives fit values for the oscillation parameters of tan super(2)theta sub(12) = ..., ... = ..., and sin super(2)theta sub(13) = ... Assuming a chondritic Th/U mass ratio, we obtain ... nu sub(e) events from super(238)U and super(232)Th, corresponding to a geo nu sub(e) flux of ... x 10 super(6) cm super(-2) s super(-1) at the KamLAND location. We evaluate various bulk silicate Earth composition models using the observed geo nu sub(e) rate.
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