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M. Hirose

Publications and source records attributed to M. Hirose.

9 recordsLinked to original sources
arXiv2021

Observation of Coulomb-assisted nuclear bound state of $Ξ^-$-$^{14}$N system

In an emulsion-counter hybrid experiment performed at J-PARC, a $Ξ^-$ absorption event was observed which decayed into twin single-$Λ$ hypernuclei. Kinematic calculations enabled a unique identification of the reaction process as $Ξ^{-} + ^{14}$N$\ \rightarrow\ ^{10}_Λ$Be + $^5_Λ$He. For the binding energy of the $Ξ^{-}$ hyperon in the $Ξ^-$-$^{14}$N system a value of $1.27 \pm 0.21$ MeV was deduced. The energy level of $Ξ^-$ is likely a nuclear $1p$ state which indicates a weak $ΞN$-$ΛΛ$ coupling.

nucl-ex↗
arXiv2020

Design and performance of a high-pressure xenon gas TPC as a prototype for a large-scale neutrinoless double-beta decay search

A high-pressure xenon gas time projection chamber, with a unique cellular readout structure based on electroluminescence, has been developed for a large-scale neutrinoless double-beta decay search. In order to evaluate the detector performance and validate its design, a 180~L size prototype is being constructed and its commissioning with partial detector has been performed. The obtained energy resolution at 4.0~bar is 1.73 $\pm$ 0.07% (FWHM) at 511 keV. The energy resolution at the $^{136}$Xe neutrinoless double-beta decay Q-value is estimated to be between 0.79 and 1.52% (FWHM) by extrapolation. Reconstructed event topologies show patterns peculiar to track end-point which can be used to distinguish $0νββ$ signals from gamma-ray backgrounds.

physics.ins-det↗
arXiv2019

AXEL: High-pressure Xe gas TPC for BG-free $0\nu2β$ decay search

AXEL is a high-pressure xenon gas time projection chamber for neutrinoless double-beta decay (0n2b) search. The AXEL has a unique readout system called ELCC which has a cellular structure and photosensors to detect electroluminescence light produced by ionization electrons. We demonstrated the performance of the ELCC with a small prototype detector (AXEL-HP10L). The obtained energy resolution corresponds to 0.82 -- 1.74% (FWHM) at the 0n2b Q-value. We are constructing a new prototype (AXEL-HP180L) in order to study the energy resolution at the Q-value of 0n2b with a new design of ELCC with unit structure, newly developed electronics board, field-shaping electrodes, and Cockcroft-Walton-type high voltage power supply. For a future 1-ton scale large AXEL detector, we are developing new background-reduction techniques; topology identification with machine learning, positive-ion detection, and active-shield options.

physics.ins-det↗
arXiv2019

Observation of a Be double-Lambda hypernucleus in the J-PARC E07 experiment

A double-$Λ$ hypernucleus, ${}_{ΛΛ}\mathrm{Be}$, was observed by the J-PARC E07 collaboration in nuclear emulsions tagged by the $(K^{-},K^{+})$ reaction. This event was interpreted as a production and decay of $ {}_{ΛΛ}^{\;10}\mathrm{Be}$, ${}_{ΛΛ}^{\;11}\mathrm{Be}$, or ${}_{ΛΛ}^{\;12}\mathrm{Be}^{*}$ via $Ξ^{-}$ capture in ${}^{16}\mathrm{O}$. By assuming the capture in the atomic 3D state, the binding energy of two $Λ$ hyperons$\,$($B_{ΛΛ}$) of these double-$Λ$ hypernuclei are obtained to be $15.05 \pm 0.11\,\mathrm{MeV}$, $19.07 \pm 0.11\,\mathrm{MeV}$, and $13.68 \pm 0.11\,\mathrm{MeV}$, respectively. Based on the kinematic fitting, ${}_{ΛΛ}^{\;11}\mathrm{Be}$ is the most likely explanation for the observed event.

nucl-ex↗
arXiv2018

Angular dependence of columnar recombination in high pressure xenon gas using time profile of scintillation emission

The angular dependence of the columnar recombination in xenon gas, if observed for low energy nuclear tracks, can be used for a direction-sensitive dark matter search. We measured both scintillation and ionization to study columnar recombination for 5.4 MeV alpha particles in a high pressure gas detector filled with 8 atm xenon. Since the recombination photons are emitted several~$μ$s after de-excitation emission, scintillation photons are separated to the fast and slow components. The fast component does not show dependence on the track angle relative to the drift electric field, on the other hand, the slow component increases when the track is aligned with the electric field. The result indicates that the track angle relative to the electric field can be reconstructed from the scintillation time profile.

astro-ph.IM↗
arXiv2017

Electroluminescence collection cell as a readout for a high energy resolution Xenon gas TPC

AXEL is a high pressure xenon gas TPC detector being developed for neutrinoless double-beta decay search. We use the proportional scintillation mode with a new electroluminescence light detection system to achieve high energy resolution in a large detector. The detector also has tracking capabilities, which enable significant background rejection. To demonstrate our detection technique, we constructed a 10L prototype detector filled with up to 10bar xenon gas. The FWHM energy resolution obtained by the prototype detector is 4.0 $\pm$ 0.30 $\%$ at 122 keV, which corresponds to 0.9 ~ 2.0 % when extrapolated to the Q value of the $0νββ$ decay of $^{136}$Xe.

physics.ins-det↗
arXiv2015

Time-optimal control with finite bandwidth

Optimal control theory provides recipes to achieve quantum operations with high fidelity and speed, as required in quantum technologies such as quantum sensing and computation. While technical advances have achieved the ultrastrong driving regime in many physical systems, these capabilities have yet to be fully exploited for the precise control of quantum systems, as other limitations, such as the generation of higher harmonics or the finite bandwidth of the control fields, prevent the implementation of theoretical time-optimal control. Here we present a method to achieve time-optimal control of qubit systems that can take advantage of fast driving beyond the rotating wave approximation. We exploit results from optimal control theory to design driving protocols that can be implemented with realistic, finite-bandwidth control and we find a relationship between bandwidth limitations and achievable control fidelity.

quant-ph↗