LHC-ATLAS実験における１レプトン終状態を用いたグルイーノ探索

学位の種別: 課程博士審査委員会委員 : （主査）東京大学准教授 小沢 恭一郎, 東京大学准教授 横山 将志, 東京大学准教授 今井 伸明, 東京大学教授 後田 裕, 東京大学准教授 伊部 昌宏University of Tokyo(東京大学

Quantum Enhancement in Dark Matter Detection with Quantum Computation

We propose a novel method to significantly enhance the signal rate in the qubit-based dark matter detection experiments with the help of quantum interference. Various quantum sensors possess ideal properties for detecting wave-like dark matter, and qubits, commonly employed in quantum computers, are excellent candidates for dark matter detectors. We demonstrate that, by designing an appropriate quantum circuit to manipulate the qubits, the signal rate scales proportionally to $n_{\rm q}^2$, with $n_{\rm q}$ being the number of sensor qubits, rather than linearly with $n_{\rm q}$. Consequently, in the dark matter detection with a substantial number of sensor qubits, a significant increase in the signal rate can be expected. We provide a specific example of a quantum circuit that achieves this enhancement by coherently combining the phase evolution in each individual qubit due to its interaction with dark matter. We also demonstrate that the circuit is fault tolerant to de-phasing noises, a critical quantum noise source in quantum computers. The enhancement mechanism proposed here is applicable to various modalities for quantum computers, provided that the quantum operations relevant to enhancing the dark matter signal can be applied to these devices.Comment: 7 pages, 2 figure

Detection of hidden photon dark matter using the direct excitation of transmon qubits

We propose a novel dark matter detection method utilizing the excitation of superconducting transmon qubits. Assuming the hidden photon dark matter of a mass of $O(10)\ \mu{\rm eV}$, the classical wave-matter oscillation induces an effective ac electric field via the small kinetic mixing with the ordinary photon. This serves as a coherent drive field for a qubit when it is resonant, evolving it from the ground state towards the first-excited state. We evaluate the rate of such evolution and observable excitations in the measurements, as well as the search sensitivity to the hidden photon dark matter. For a selected mass, one can reach $\epsilon \sim 10^{-12}-10^{-14}$ (where $\epsilon$ is the kinetic mixing parameter of the hidden photon) with a single standard transmon qubit. A simple extension to the frequency-tunable SQUID-based transmon enables the mass scan to cover the whole $4-40\ \mu{\rm eV}$ ($1-10$ GHz) range within a reasonable length of run time. The sensitivity scalability along the number of the qubits also makes it a promising platform in accord to the rapid evolution of the superconducting quantum computer technology.Comment: 7 pages, 1 figure, published versio

Reconstruction of primary vertices at the ATLAS experiment in Run 1 proton–proton collisions at the LHC

This paper presents the method and performance of primary vertex reconstruction in proton–proton collision data recorded by the ATLAS experiment during Run 1 of the LHC. The studies presented focus on data taken during 2012 at a centre-of-mass energy of √s=8 TeV. The performance has been measured as a function of the number of interactions per bunch crossing over a wide range, from one to seventy. The measurement of the position and size of the luminous region and its use as a constraint to improve the primary vertex resolution are discussed. A longitudinal vertex position resolution of about 30μm is achieved for events with high multiplicity of reconstructed tracks. The transverse position resolution is better than 20μm and is dominated by the precision on the size of the luminous region. An analytical model is proposed to describe the primary vertex reconstruction efficiency as a function of the number of interactions per bunch crossing and of the longitudinal size of the luminous region. Agreement between the data and the predictions of this model is better than 3% up to seventy interactions per bunch crossing

Screening of New Microsatellite DNA Markers from the Genome of Platyeriocheir formosa

The catadromous Platyeriocheir formosa is a crab endemic in Taiwan. To conserve P. formosa population diversity and ensure the sustainable use of this natural resource, we have developed new genetic markers, 17 polymorphic microsatellite loci, to promote the study of its population genetics in the future. In this study, more than 70 microsatellite sequences were found. Among these, 18 loci were selected to analyze the genetic diversity of P. formosa. With the exception of the Pfo15 locus, all of the remaining loci were polymorphic with allelic numbers ranging from 3–14. Heterozygosity within all 17 polymorphic loci ranged from 0.2–0.95 with an average of 0.55, which suggested that these loci are proper markers for studying population genetics. After we tested cross-specific amplification, eight and six primer sets could be successfully used for the amplification of microsatellite loci in morphologically similar Eriocheir sinensis and E. japonica, respectively; this suggests that they are useful markers for closely related species

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements