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S. Komamiya

Publications and source records attributed to S. Komamiya.

12 recordsLinked to original sources
arXiv2020

Experimental Search for Non-Newtonian Forces in the Nanometer Scale with Slow Neutrons

Improved limits for new gravity-like short-range interactions, in which a scattering potential is modeled by the Yukawa-type parametrization, have been obtained by measuring the angular distribution of 6 Å neutrons scattering from atomic xenon gas. We have collected approximately $1.4 \times 10^8$ small-angle neutron scattering events. The data are interpreted as no evidence of new forces and show improved upper limits on the coupling strength in the interaction range of $0.3$ nm to $9$ nm. These improved constraints are also interpreted as new limits for a model, in which a charge of the new forces is expressed as a linear combination of the baryon number and the lepton number.

hep-ex↗
arXiv2015

Constraints on New Gravitylike Forces in the Nanometer Range

We report on a new constraint on gravitylike short-range forces, in which the interaction charge is mass, obtained by measuring the angular distribution of 5 A neutrons scattering off atomic xenon gas. Around 10^7 scattering events were collected at the 40 m small angle neutron scattering beam line located at the HANARO research reactor of the Korean Atomic Energy Research Institute. The extracted coupling strengths of new forces in the Yukawa-type parametrization are g^2 = (0.2 \pm 6.8 \pm 2.0) \times 10^-15 GeV^2 and g^2 = (-5.3 \pm 9.0 + 2.7 -2.8) \times 10^-17 GeV^2 for interaction ranges of 0.1 and 1.0 nm, respectively. These strengths correspond to 95% confidence level limits of g^2 < (1.4 \pm 0.2) \times 10^-14 GeV^-2 and g^2 < (1.3 \pm 0.2) \times 10^-16 GeV^-2, improving the current limits for interaction ranges between 4 and 0.04 nm by a factor of up to 10.

hep-ex↗
arXiv2015

Precision Measurement of the Position-space Wave Functions of Gravitationally Bound Ultracold Neutrons

Gravity is the most familiar force at our natural length scale. However, it is still exotic from the view point of particle physics. The first experimental study of quantum effects under gravity was performed using a cold neutron beam in 1975. Following this, an investigation of gravitationally bound quantum states using ultracold neutrons was started in 2002. This quantum bound system is now well understood, and one can use it as a tunable tool to probe gravity. In this paper, we review a recent measurement of position-space wave functions of such gravitationally bound states, and discuss issues related to this analysis, such as neutron loss models in a thin neutron guide, the formulation of phase space quantum mechanics, and UCN position sensitive detectors. The quantum modulation of neutron bound states measured in this experiment shows good agreement with the prediction from quantum mechanics.

hep-ex↗
arXiv2014

Observation of $χ_{c1}$ decays into vector meson pairs $ϕϕ$, $ωω$, and $ωϕ$

Decays of $χ_{c1}$ to vector meson pairs $ϕϕ$, $ωω$ and $ωϕ$ are observed for the first time using $(106\pm4)\times 10^6$ $\psip$ events accumulated at the BESIII detector at the BEPCII $e^+e^-$ collider. The branching fractions are measured to be $(4.4\pm 0.3\pm 0.5)\times 10^{-4}$, $(6.0\pm 0.3\pm 0.7)\times 10^{-4}$, and $(2.2\pm 0.6\pm 0.2)\times 10^{-5}$, for $χ_{c1}\to ϕϕ$, $ωω$, and $ωϕ$, respectively. The observation of $χ_{c1}$ decays into a pair of vector mesons $ϕϕ$, $ωω$ and $ωϕ$ indicates that the hadron helicity selection rule is significantly violated in $χ_{cJ}$ decays. In addition, the measurement of $χ_{cJ}\to ωϕ$ gives the rate of doubly OZI-suppressed decay. Branching fractions for $χ_{c0}$ and $χ_{c2}$ decays into other vector meson pairs are also measured with improved precision.

hep-ex↗
arXiv2014

Observation of the Spatial Distribution of Gravitationally Bound Quantum States of Ultracold Neutrons and Its Derivation Using the Wigner Function

Ultracold neutrons (UCNs) can be bound by the potential of terrestrial gravity and a reflecting mirror. The wave function of the bound state has characteristic modulations. We carried out an experiment to observe the vertical distribution of the UCNs above such a mirror at Institut Laue-Langevin in 2011. The observed modulation is in good agreement with that prediction by quantum mechanics using the Wigner function. The spatial resolution of the detector system is estimated to be 0.7 micro meter. This is the first observation of gravitationally bound states of UCNs with submicron spatial resolution.

hep-ex↗
arXiv2012

Present status and first results of the final focus beam line at the KEK Accelerator Test Facility

ATF2 is a final-focus test beam line which aims to focus the low emittance beam from the ATF damping ring to a vertical size of about 37 nm and to demonstrate nanometer level beam stability. Several advanced beam diagnostics and feedback tools are used. In December 2008, construction and installation were completed and beam commissioning started, supported by an international team of Asian, European, and U.S. scientists. The present status and first results are described.

physics.acc-ph↗
arXiv2010

Shintake Monitor in ATF2: Performance Evaluation

The beam test for the Shintake monitor succeeded in measuring signal modulation with the laser interference fringe pattern in November 2009. We have studied the error sources, and evaluated the systematic error to be less than 30% for 1 minute measurements. This paper centers on the evaluation of the Shintake monitor performance through analyzing beam tests deta. Most systematic error sources are well understood, enabling accurate measurement of the beam size when it reaches 37 nm.

physics.ins-det↗
arXiv2010

Development of a Pixel Detector for Ultra-Cold Neutrons

A pixel detector with high spatial resolution and temporal information for ultra-cold neutrons is developed based on a commercial CCD on which a neutron converter is attached. 10B and 6Li are tested for the neutron converter and 10B is found to be more suitable based on efficiency and spatial resolution. The pixel detector has an efficiency of 44.1 +- 1.1% and a spatial resolution of 2.9 +- 0.1 um (1 sigma).

physics.ins-det↗
arXiv2009

Proposal for measuring the quantum states of neutrons in the gravitational field with a CCD-based pixel sensor

An experimental setup is proposed for the precise measurement of the quantum states of ultracold neutrons bound in the earth's gravitational field. The experiment utilizes a CCD-based pixel sensor and magnification system to observe the fine structure of the neutron distribution. In this work, we analyzed the sensor's deposited energy measurement capability and found that its spatial resolution was 5.3 um. A magnifying power of two orders of magnitude was realized by using a cylindrical rod as a convex mirror.

physics.ins-det↗
arXiv2007

R&D Status of ATF2 IP Beam Size Monitor (Shintake Monitor)

Shintake monitor is a nanometer-scale electron beam size monitor. It probes a electron beam by an interference fringe pattern formed by split laser beams. Minimum measurable beam size by this method is less than 1/10 of laser wavelength. In ATF2, Shintake monitor will be used for the IP beam size monitor to measure 37 nm (design) beam size. Development status of the Shintake monitor, including fringe phase monitoring and stabilization, gamma detector and collimators, is described. In addition, we discuss the beam size measurement by Shintake monitor in ILC.

physics.acc-ph↗
arXiv1996

Searches For New Physics

Review of prospects for discovery of new physics signals at LEP2. The areas covered include SUSY, exotic fermions, BESS models, leptoquarks, virtual effects and CP violating observables.

hep-ph↗