We are searching for the decay KL→π0νν¯ in the KOTO experiment at J-PARC. The signal is identified by detecting two photons from the π0 decay with a calorimeter composed of undoped CsI crystals. The ...main background "hadron cluster background" is caused by a neutron hitting the calorimeter to form two clusters: a neutron in the beam halo hits the calorimeter to generate the first cluster, and a secondary neutron generated in the interaction creates the second separated cluster. In order to reduce this background, we upgraded the calorimeter to have both-end readout by attaching MPPCs on the upstream face of each CsI crystal in addition to the original PMT attached on the downstream face. The background can be rejected exploiting the timing difference between the MPPC and PMT, since neutrons tend to interact deeper inside the crystals. We installed the MPPCs in 2018, and evaluated the performance with data taken in 2019. The principle in the calorimeter upgrade and the performance of the background reduction are reported.
We report, for the first time, the long-awaited detection of diffuse gamma rays with energies between 100 TeV and 1 PeV in the Galactic disk. Particularly, all gamma rays above 398 TeV are observed ...apart from known TeV gamma-ray sources and compatible with expectations from the hadronic emission scenario in which gamma rays originate from the decay of π^{0}'s produced through the interaction of protons with the interstellar medium in the Galaxy. This is strong evidence that cosmic rays are accelerated beyond PeV energies in our Galaxy and spread over the Galactic disk.
We report observations of gamma-ray emissions with energies in the 100-TeV energy region from the Cygnus region in our Galaxy. Two sources are significantly detected in the directions of the Cygnus ...OB1 and OB2 associations. Based on their positional coincidences, we associate one with a pulsar PSR J2032 + 4127 and the other mainly with a pulsar wind nebula PWN G75.2 + 0.1, with the pulsar moving away from its original birthplace situated around the centroid of the observed gamma-ray emission. This work would stimulate further studies of particle acceleration mechanisms at these gamma-ray sources.
Abstract
HESS J1843–033 is a very high energy gamma-ray source whose origin remains unidentified. This work presents, for the first time, the energy spectrum of gamma rays beyond 100 TeV from the ...HESS J1843–033 region using the data recorded by the Tibet air shower array and its underground muon detector array. A gamma-ray source with an extension of 0.°34 ± 0.°12 is successfully detected above 25 TeV at (
α
,
δ
) = (281.°09 ± 0.°10, −3.°76 ± 0.°09) near HESS J1843–033 with a statistical significance of 6.2
σ
, and the source is named TASG J1844–038. The position of TASG J1844–038 is consistent with those of HESS J1843–033, eHWC J1842–035, and LHAASO J1843–0338. The measured gamma-ray energy spectrum in 25 TeV <
E
< 130 TeV is described with
dN
/
dE
=
(
9.70
±
1.89
)
×
10
−
16
(
E
/40 TeV)
−3.26±0.30
TeV
−1
cm
−2
s
−1
, and the spectral fit to the combined spectra of HESS J1843–033, LHAASO J1843–0338, and TASG J1844–038 implies the existence of a cutoff at 49.5 ± 9.0 TeV. Associations of TASG J1844–038 with SNR G28.6–0.1 and PSR J1844–0346 are also discussed in detail for the first time.
Abstract
Gamma rays from HESS J1849−000, a middle-aged TeV pulsar wind nebula (PWN), are observed by the Tibet air shower array and the muon detector array. The detection significance of gamma rays ...reaches 4.0
σ
and 4.4
σ
levels above 25 TeV and 100 TeV, respectively, in units of the Gaussian standard deviation
σ
. The energy spectrum measured between 40 TeV <
E
< 320 TeV for the first time is described with a simple power-law function of
dN
/
dE
=
(
2.86
±
1.44
)
×
10
−
16
(
E
/
40
TeV
)
−
2.24
±
0.41
TeV
−
1
cm
−
2
s
−
1
. The gamma-ray energy spectrum from the sub-TeV (
E
< 1 TeV) to sub-PeV (100 TeV <
E
< 1 PeV) ranges, including the results of previous studies, can be modeled with the leptonic scenario, i.e., inverse Compton scattering by high-energy electrons accelerated by the PWN of PSR J1849−0001. On the other hand, the gamma-ray energy spectrum can also be modeled with the hadronic scenario in which gamma rays are generated from the decay of neutral pions produced by collisions between accelerated cosmic-ray protons and the ambient molecular cloud found in the gamma-ray-emitting region. The cutoff energy of cosmic-ray protons
E
p,cut
is estimated as
log
10
(
E
p
,
cut
/
TeV
)
=
3.73
−
0.66
+
2.98
, suggesting that protons are accelerated up to the PeV energy range. Our study thus proposes that HESS J1849−000 should be further investigated as a new candidate as a Galactic PeV cosmic-ray accelerator, or “PeVatron.”
Display omitted
► The as-prepared TiO
2 thin film by anodization method is amorphous. ► The amorphous TiO
2 can be changed into anatase phase after heat treatment in the range of 400–500
°C. ► ...Polymer substrates cannot withstand heat up to 450
°C, but the clay substrate can withstand heat up to 460
°C. ► The aim of this work is preparation and characterization of nanocrystalline ITO thin films on transparent flexible clay substrates for flexible dye sensitized solar cell application.
Nanocrystalline indium tin oxide (ITO) thin films were prepared on clay-1 (Clay-TPP-LP-SA), clay-2 (Clay-TPP-SA) and glass substrates using ion-beam sputter deposition method. X-ray diffraction (XRD) patterns showed that the as-deposited ITO films on both clay-1 and clay-2 substrates were a mixture of amorphous and polycrystalline. But the as-deposited ITO films on glass substrates were polycrystalline. The surface morphologies of as-deposited ITO/glass has smooth surface; in contrast, ITO/clay-1 has rough surface. The surface roughnesses of ITO thin films on glass and clay-1 substrate were calculated as 4.3 and 83
nm, respectively. From the AFM and SEM analyses, the particle sizes of nanocrystalline ITO for a film thickness of 712
nm were calculated as 19.5 and 20
nm, respectively. Optical study showed that the optical transmittance of ITO/clay-2 was higher than that of ITO/clay-1. The sheet resistances of as-deposited ITO/clay-1 and ITO/clay-2 were calculated as 76.0 and 63.0
Ω/□, respectively. The figure of merit value for as-deposited ITO/clay-2 (12.70
×
10
−3/Ω) was also higher than that of ITO/clay-1 (9.6
×
10
−3/Ω), respectively. The flexibilities of ITO/clay-1 and ITO/clay-2 were evaluated as 13 and 12
mm, respectively. However, the ITO-coated clay-2 substrate showed much better optical and electrical properties as well as flexibility as compared to clay-1.
Workshop summary: Kaons@CERN 2023 Anzivino, G.; Cuendis, Sergio Arguedas; Bernard, V. ...
The European physical journal. C, Particles and fields,
04/2024, Letnik:
84, Številka:
4
Journal Article
Recenzirano
Odprti dostop
Kaon physics is at a turning point – while the rare-kaon experiments NA62 and KOTO are in full swing, the end of their lifetime is approaching and the future experimental landscape needs to be ...defined. With HIKE, KOTO-II and LHCb-Phase-II on the table and under scrutiny, it is a very good moment in time to take stock and contemplate about the opportunities these experiments and theoretical developments provide for particle physics in the coming decade and beyond. This paper provides a compact summary of talks and discussions from the Kaons@CERN 2023 workshop, held in September 2023 at CERN.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
8.
Anisotropy and Corotation of Galactic Cosmic Rays Amenomori, M; Ayabe, S; Bi, X.J ...
Science (American Association for the Advancement of Science),
10/2006, Letnik:
314, Številka:
5798
Journal Article
Recenzirano
Odprti dostop
The intensity of Galactic cosmic rays is nearly isotropic because of the influence of magnetic fields in the Milky Way. Here, we present two-dimensional high-precision anisotropy measurement for ...energies from a few to several hundred teraelectronvolts (TeV), using the large data sample of the Tibet Air Shower Arrays. Besides revealing finer details of the known anisotropies, a new component of Galactic cosmic ray anisotropy in sidereal time is uncovered around the Cygnus region direction. For cosmic-ray energies up to a few hundred TeV, all components of anisotropies fade away, showing a corotation of Galactic cosmic rays with the local Galactic magnetic environment. These results have broad implications for a comprehensive understanding of cosmic rays, supernovae, magnetic fields, and heliospheric and Galactic dynamic environments.
CsI calorimeter for the J-PARC KOTO experiment Sato, K.; Lee, J.W.; Banno, S. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2020, Letnik:
982, Številka:
C
Journal Article
Recenzirano
Odprti dostop
An electromagnetic calorimeter made of undoped CsI crystals is used in the J-PARC KOTO experiment to search for new physics beyond the standard model with the KL→π0νν̄ decay. The calorimeter is ...designed to operate in vacuum of 0.1 Pa and in a high-rate environment where the counting rate due to KL decays is O(100) kHz. A special method to calibrate the calorimeter during the data taking without using a tracking system for charged particles is reported. The energy, position, and timing resolutions of the calorimeter were evaluated in several beam tests, and the resolutions satisfy the required performance. The energy resolution with the total energy E is 0.66⊕1.81∕EGeV% in the inner region of the calorimeter.
We report on a clear solar-cycle variation of the Sun’s shadow in the 10 TeV cosmic-ray flux observed by the Tibet air shower array during a full solar cycle from 1996 to 2009. In order to clarify ...the physical implications of the observed solar cycle variation, we develop numerical simulations of the Sun’s shadow, using the potential field source surface model and the current sheet source surface (CSSS) model for the coronal magnetic field. We find that the intensity deficit in the simulated Sun’s shadow is very sensitive to the coronal magnetic field structure, and the observed variation of the Sun’s shadow is better reproduced by the CSSS model. This is the first successful attempt to evaluate the coronal magnetic field models by using the Sun’s shadow observed in the TeV cosmic-ray flux.
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