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M. Takamura

Publications and source records attributed to M. Takamura.

9 recordsLinked to original sources
arXiv2023

A Large-Scale Pad-Sensor Based Prototype of the Silicon Tungsten Electromagnetic Calorimeter for the Forward Direction in ALICE at LHC

We constructed a large-scale electromagnetic calorimeter prototype as a part of the Forward Calorimeter upgrade project (FoCal) for the ALICE experiment at the Large Hadron Collider (LHC). The prototype, also known as ``Mini FoCal'', consists of 20 layers of silicon pad sensors and tungsten alloy plates with printed circuit boards and readout electronics. The constructed detector was tested at the test beam facility of the Super Proton Synchrotron (SPS) at CERN. We obtain an energy resolution of about 4.3% for electron beams at both 150 and 250 GeV/$c$, which is consistent with realistic detector response simulations. Longitudinal profiles of electromagnetic shower were also measured and found to agree with the simulations. The same prototype detector was installed in the ALICE experimental area about 7.5m away from the interaction point. It was used to measure inclusive electromagnetic cluster energy distributions and neutral-pion candidate invariant mass distributions for pseudo-rapidity of $\eta$=3.7-4.5 in proton-proton collisions at $\sqrt{s}$ = 13 TeV at LHC. The measured distributions in different $\eta$ regions are similar to those obtained from PYTHIA simulations.

physics.ins-det↗
arXiv2017

Search for Anisotropy in the Ultra High Energy Cosmic Ray Spectrum using the Telescope Array Surface Detector

The Telescope Array (TA) experiment is located in the western desert of Utah, USA, and observes ultra high energy cosmic rays (UHECRs) in the Northern hemisphere. At the highest energies, $E>10$~EeV, the shape of cosmic ray energy spectrum may carry an imprint of the source density distribution along the line of sight different in different directions of the sky. In this study, we search for such directional variations in the shape of the energy spectrum using events observed with the Telescope Array's surface detector. We divide the TA field of view into two nearly equal-exposure regions: the "on-source" region which we define as $\pm 30^\circ$ of the supergalactic plane containing mostly nearby structures, and the complementary "off-source" region where the sources are further away on average. We compare the UHECR spectra in these regions by fitting them to the broken power law and comparing the resulting parameters. We find that the off-source spectrum has an earlier break at highest energies. The chance probability to obtain such or larger difference in statistically equivalent distributions is estimated as $6.2\pm1.1\times10^{-4}$ ($3.2σ$) by a Monte-Carlo simulation. The observed difference in spectra is in a reasonable quantitative agreement with a simplified model that assumes that the UHECR sources trace the galaxy distribution from the 2MRS catalogue, primary particles are protons and the magnetic deflections can be neglected.

astro-ph.HE↗
arXiv2016

Search for EeV Protons of Galactic Origin

Cosmic rays in the energy range $10^{18.0}$ - $10^{18.5}$ eV are thought to have a light, probably protonic, composition. To study their origin one can search for anisotropy in their arrival directions. Extragalactic cosmic rays should be isotropic, but galactic cosmic rays of this type should be seen mostly along the galactic plane, and there should be a shortage of events coming from directions near the galactic anticenter. This is due to the fact that, under the influence of the galactic magnetic field, the transition from ballistic to diffusive behavior is well advanced, and this qualitative picture persists over the whole energy range. Guided by models of the galactic magnetic field that indicate that the enhancement along the galactic plane should have a standard deviation of about 20$^\circ$ in galactic latitude, and the deficit in the galactic anticenter direction should have a standard deviation of about 50$^\circ$ in galactic longitude, we use the data of the Telescope Array surface detector in $10^{18.0}$ to $10^{18.5}$ eV energy range to search for these effects. The data are isotropic. Neither an enhancement along the galactic plane nor a deficit in the galactic anticenter direction is found. Using these data we place an upper limit on the fraction of EeV cosmic rays of galactic origin at 1.3% at 95% confidence level.

astro-ph.HE↗
arXiv2015

Measurement of the Proton-Air Cross Section with Telescope Array's Middle Drum Detector and Surface Array in Hybrid Mode

In this work we are reporting on the measurement of the proton-air inelastic cross section $σ^{\rm inel}_{\rm p-air}$ using the Telescope Array (TA) detector. Based on the measurement of the $σ^{\rm inel}_{\rm p-air}$ the proton-proton cross section $σ_{\rm p-p}$ value is also determined at $\sqrt{s} = 95_{-8}^{+5}$ TeV. Detecting cosmic ray events at ultra high energies with Telescope Array enables us to study this fundamental parameter that we are otherwise unable to access with particle accelerators. The data used in this report is the hybrid events observed by the Middle Drum fluorescence detector together with the surface array detector collected over five years. The value of the $σ^{\rm inel}_{\rm p-air}$ is found to be equal to $567.0 \pm 70.5 [{\rm Stat.}] ^{+29}_{-25} [{\rm Sys.}]$ mb. The total proton-proton cross section is subsequently inferred from Glauber Formalism and Block, Halzen and Stanev QCD inspired fit and is found to be equal to $170_{-44}^{+48} [{\rm Stat.}] _{-17}^{+19} [{\rm Sys.}] $mb.

astro-ph.HE↗
arXiv2015

A Northern Sky Survey for Point-Like Sources of EeV Neutral Particles with the Telescope Array Experiment

We report on the search for steady point-like sources of neutral particles around 10$^{18}$ eV between 2008 May and 2013 May with the scintillator surface detector of the Telescope Array experiment. We found overall no significant point-like excess above 0.5 EeV in the northern sky. Subsequently, we also searched for coincidence with the Fermi bright Galactic sources. No significant coincidence was found within the statistical uncertainty. Hence, we set an upper limit on the neutron flux that corresponds to an averaged flux of 0.07 km$^{-2}$ yr$^{-1}$ for $E>1$ EeV in the northern sky at the 95% confidence level. This is the most stringent flux upper limit in a northern sky survey assuming point-like sources. The upper limit at the 95% confidence level on the neutron flux from Cygnus X-3 is also set to 0.2 km$^{-2}$ yr$^{-1}$ for $E>0.5$ EeV. This is an order of magnitude lower than previous flux measurements.

astro-ph.HE↗
arXiv2014

Study of Ultra-High Energy Cosmic Ray Composition Using Telescope Array's Middle Drum Detector and Surface Array in Hybrid Mode

Previous measurements of the composition of Ultra-High Energy Cosmic Rays(UHECRs) made by the High Resolution Fly's Eye(HiRes) and Pierre Auger Observatory(PAO) are seemingly contradictory, but utilize different detection methods, as HiRes was a stereo detector and PAO is a hybrid detector. The five year Telescope Array(TA) Middle Drum hybrid composition measurement is similar in some, but not all, respects in methodology to PAO, and good agreement is evident between data and a light, largely protonic, composition when comparing the measurements to predictions obtained with the QGSJetII-03 and QGSJet-01c models. These models are also in agreement with previous HiRes stereo measurements, confirming the equivalence of the stereo and hybrid methods. The data is incompatible with a pure iron composition, for all models examined, over the available range of energies. The elongation rate and mean values of Xmax are in good agreement with Pierre Auger Observatory data. This analysis is presented using two methods: data cuts using simple geometrical variables and a new pattern recognition technique.

astro-ph.HE↗
arXiv2014

Indications of Intermediate-Scale Anisotropy of Cosmic Rays with Energy Greater Than 57 EeV in the Northern Sky Measured with the Surface Detector of the Telescope Array Experiment

We have searched for intermediate-scale anisotropy in the arrival directions of ultrahigh-energy cosmic rays with energies above 57~EeV in the northern sky using data collected over a 5 year period by the surface detector of the Telescope Array experiment. We report on a cluster of events that we call the hotspot, found by oversampling using 20$^\circ$-radius circles. The hotspot has a Li-Ma statistical significance of 5.1$σ$, and is centered at R.A.=146.7$^{\circ}$, Dec.=43.2$^{\circ}$. The position of the hotspot is about 19$^{\circ}$ off of the supergalactic plane. The probability of a cluster of events of 5.1$σ$ significance, appearing by chance in an isotropic cosmic-ray sky, is estimated to be 3.7$\times$10$^{-4}$ (3.4$σ$).

astro-ph.HE↗