チベット実験・アルパカ実験
グループガイダンス
﨏さこ 隆志
•
•
•
•
•
•
•

研究室の紹介
銀河宇宙線の謎
最⾼エネルギーガンマ線天⽂学〜宇宙最⾼エネルギーの光⼦〜
空気シャワーの観測
チベット実験
アルパカ実験
⼤学院⽣の⽣活・研究テーマ
1

研究室・研究グループの体制• 教授：瀧⽥正⼈（新規修⼠学⽣の受け⼊れなし）• 准教授：さこ隆志（修⼠学⽣の受け⼊れ可）• 助教：⼤⻄宗博、川⽥和正、佐古崇志• PD：Marcos Anzorena、加藤勢• ⼤学院⽣：横江、川島、⽔野• 秘書：⽩神• 国内共同研究者：横浜国⽴⼤学、信州⼤学、神奈川⼤学、⽇本⼤学、⼤阪公⽴⼤学、宇都宮
⼤学、⼤阪電気通信⼤学、中部⼤学、他• 国外共同研究者：中国国家天⽂台（中国）、サンアンドレス⼤学（ボリビア）、グアダラハ
ラ⼤学（メキシコ）、他
2銀河宇宙線起源の謎
Knee
~4PeV

系内起源?

• 宇宙線＝宇宙を⾶び交う⾼エネルギーの放射線• 主成分＝原⼦核（陽⼦を含む）• 起源＝不明：天体周りの衝撃波が有⼒候補• 超新星残骸？
• 中性⼦星？
• 星⽣成領域？
• ブラックホール？
• 未知の粒⼦（暗⿊物質）の対消滅や崩壊？

2nd Knee~200PeV
Ankle
~5EeV

系外起源?

1015eV
Gaisser et al. Front.Phys.(Beijing) 8 (2013) 748

1020eV• 定説：• 銀河系内では陽⼦は4x1015eV (PeV)まで加速• 原⼦核はZ倍なので鉄原⼦核は1017eV• それより上は銀河系外起源？
• 宇宙の限界は1020eV
ここはテレスコープアレイ実験• 我々がやるべきこと・やりたいこと：• 銀河系内の陽⼦加速の限界は？
• 限界加速はどこで起きているのか？
• ⾼エネルギーで原⼦核種はどう変化するのか？
3• 新物理の証拠を探す（ダークマター、原始BH、…）

何が問題？
1015eV

？

宇宙線の起源
超新星残骸？

宇宙線は荷電粒⼦
宇宙には磁場がある＝まっすぐ⾶んでこない4ガンマ線で探る宇宙線の起源
1015eV？

1014eV 𝛾

宇宙線の起源
超新星残骸？

Interstellar
Matter1015eV CR
𝜋0𝛾5⾼エネルギーガンマ線の観測
宇宙磁場

宇宙線原⼦核宇宙線の伝播宇宙線の起源
宇宙線陽⼦
星間物質

超PeV宇宙線

sub-PeVガンマ線

6⾼エネルギーガンマ線の観測
宇宙磁場

宇宙線原⼦核宇宙線の伝播宇宙線の起源
宇宙線陽⼦
星間物質

超PeV宇宙線

sub-PeVガンマ線

宇宙線空気シャワー

空気シャワーアレイ実験
7

Shadow Observed by
Air Shower Arraywata
ty of Tokyo, JapanAS Collaboration

32nd ICRC, Aug.ust 17, Beijing

Yangbajing Cosmic Ray Observatory

1

Beijing
1.5 hours drive from Lhasa
Yangbajing

Lhasa

Chengdu90゜522E, 30゜102N, 4,300 m a.s.l. (606g/cm2)
8

チベット空気シャワー観測装置

p チベット (90.522oE, 30.102oN) 標高4300 m
現行スペックp シンチレーション検出器数 0.5 m2 x 597
p 空気シャワー有効面積~65,700 m2
p 観測エネルギー>TeV
p 角度分解能~0.5 @10TeV g~0.2 @100TeV g
p エネルギー分解能~40%@10TeV g~20%@100TeV g
p視野
~2 sr
à空気シャワー中の二次粒子(主にe+/-,γ)を観測し一次宇宙線エネルギー、方向を決定

9宇宙線シャワーとガンマ線シャワーの区別• 宇宙線シャワーの頻度 >> ガンマ線シャワーの頻度• 宇宙線シャワーにはミュー粒⼦が多い。ミュー粒⼦は地下2mまで到達• 地下のミュー粒⼦検出器で宇宙線イベントを排除！

Air shower MC

200TeV gamma showerelectron・positron・muon

200TeV proton showerelectron・positron・muon

Ground surface10羊八井高原,中国, チベット

海抜4300 m . = 606 g/cm2

Google Map

Google map

チベット空気シャワーアレイと地下ミューオン検出器
1110% for 100 and 400 TeV, respectively. The
rgy scale uncertainty was estimated to be 12%
tward displacement of the Moon’s shadow center
NATURE ASTRONOMYLETTERSomagnetic field [21]. The live time of the dataset
NATURE ASTRONOMYLETTERS
NATURE ASTRONOMYnom February 2014 to May 2017, and the average
a
b
cocoo
a
ection time for the Galactic plane observation isgnusyTibet AS 𝛾 Collaboration,C
RSF
Nature Astron., 5, 460-464 (2021)
ly 3700 h at the zenith angle
lessthan 40°. The
NATUREASTRONOMYLETTERSn criteria are the same in our previous work [12]e muon cut condition. According to the CASA2.7
106.3+
2
ment, the marginal excess along the Galactic
SN R G
sub-PeVenergies is 1.63 σ, and the fraction of(b) E >100 TeV
smic-ray abackgroundbe45, 025002 (2021)
ASO-KM2Aef
a ce d events is estimated
Chi . Phto. C
ly 3 × 10−5 [18]. In order to search for signals
mall excess fraction, we adopt a tight muon cut innalyses requiring for gamma-ray-like events to
Fig. 2 | Spectral energy distribution of the γ-ray emission and cosmic ray demeasured by different γ-ray instruments. Here, Φ is the γ-ray flux, which is g
Collaboration,
NatureAstron.,5, 465-471 (2021)< 2.1 × 10−4 ðΣρÞ1.2 or ΣN μ < 0.4, where ΣN μ
Fig. 1 | Significance map of the Cocoon region before and after subtraction of the known HAWC
sources at theregion. a, Significance mapof the Cocoon
region.
measurements
for the Cocoon
in this study. The errors on the flux points are
Extended Data Fig. 1 | Spectral gamma-ray energy distribution of G106.3+2.7.Thea, Thepointswith 1σ statisticalmeasurements
mapflux
is indata
Galactic
coordinates,
where berror
and l bars
refer include
to latitude
and longitude, respectively. It is produced as described in ref. . The blue contours areby the ARGO observatory shown in grey squares . The red a
by Tibet
AS+MD(redunderground
dots; this work), Fermi (blue squares), VERITAS (purple
pentagons)
and theDominionRadio AstrophysicalObservatory’sTable 1. The green contour is the ROI used for themeasurements
number of muons detected
in
the
four
annuli centred
at theOB2 association
as listed in Supplementary
study, which masks the brightrespectively.
The(γ
grey
triangles
Synthesis Telescope (turquoise blue dots). The two red downward arrows above
10 4 eVshow
99% C.L. b,
upper
limits obtainedby thiswork.
Noteafterthatsubtracting HAWC J2031+415 (PWN) and 2HWC
source2HWC
J2019+367.
Significancemap of the
CocoonregionJ2020+403
Cygni).
The are from the Fermi-LAT analysis in ref. . The
all theorder
VERITAS data
are raised by a factor of 1.62 to account for the spill-overof gamma-ray
signalsoutside theirwindowof 0.32 radius.
of thefrom
region.
(The leptonic modelling results are provided in Extenlight-blue,
medium-blueand dark-bluedashedlines sizeare contours
for 0.16, 0.24 and 0.32 photons per 0.1°!×!0.1° spatialmodellingbin, respectively,
Fermi-LATor array. This is just one
ofpointsmagnitude
The best-fit gamma-ray energy spectrum in the leptonic model is shown by the Cocoon
black solid
curve,
withfluxassuming
by the electron
synchrotron(the. Bothmaps
arethemade
a 0.5° extended
disk radiation
source anda spectral index of −2.6 with 1,343 days of HAWC
data.
rings (0–15!pc,
15–29!pc, 29–44!pc and 44–55!pc) centred at the OB2 associaorange solid curve),
the IC scattering
CMB photons (the green dashed curve) and the IC scattering of IR photons (the light blue dash-dotted curve). The
he criterion used in our previous
work[12].ofTheusing HAWC γ-ray data. The y errors are the statistical errors and the x error
gray open diamond shows the flux of PSR J2229+6114 obtained in the 2!−!10 keV range . b, The best-fit gamma-ray energy spectrum in the hadronic model(signature of the continuous particle injection) and constant profile (signatu
is shown
by the turquoise
curve. The lower panels show the residual Δσofthe fit. (dec.) = 41.51° ± 0.04°), which is a slightly extended to be peaked toward the stellar clusters, but rather trace the difdeclination
urvivalratio
this tightmuon
cutblueissolidexperTibet
AS 𝛾withCollaboration,
symmetry for the γ-ray emission region and by averaging the density profile
source with a Gaussian width of 0.27° and is possibly associated fuse dust emission across the entire Cocoon. This adds difficulty toby the PRL
Tibet123,
AS+MD
array(2019)
for (a) E > 10
and for (b)localandcosmicray density
051101−6TeV
with the PWN TeV J2032+4130 (refs. ), and HAWC J2030+409, the task of distinguishing the leptonic
hadronic
originsaboveof the10!TeV based on Alpha Magnetic Spectromet
imatedtobeapproximately
10
above
400
TeV,
pulsar position.
from ref.
. emissionof the Cygnus
Cocoonwhich is a very-high-energy counterpart of the GeV Cygnus γ-ray radiation. The measurements100!GeV
a ce e ed
he C ab Neb la a h ee e e gLHAASO
a ge . σ Collaboration,i he ig a f he 2-di e i
Cocoon (Methods). The region after subtraction of HAWC above 10 TeV break the degeneracy of the two origins. As shown
mma-rayratio
is estimated
30%
by
KM2A. The c lsurvivale e e>56TeV
heig ifica
ce. S iChin.
he aPhys.
i to be
al
e
i
he
a
.
J2031+415 (PWN) and 2HWC J2020+403 (γ Cygni) is shown in Extended Data Fig. 1, we find it unlikely that a single electron
C45, 023002 (2021)
produces γ rays fromcosmic
GeV toray
the density
highest energy
in Fig. 1b.
profileby
above 100 GeV from ref. , which clearly
ASURED
BY THEMD ARRAY
lation. The
comparison
between the cosmic-ray
futostheetotal flux detected population
inverse-Compton emission without
its synchrotron
radiationAlternatively,
vioHAWC J2030+409 contributes
f~90%
favours
the 1/r profile.
the 1/r profile is less striking
DaitestC abi i (R.A. =1
at the ROI and is detected withstatistic (equation (1), likeli- lating the flux constraints posed by radio and X-ray observations.
62time.
for TeV cosmic rays becauseof their escapeeheMC
simulation
is described in Fig. S1 inhood ratio test), TS, of 195.2 at the position RA = 307.65° ± 0.30°, The leptonic origin of the γ-ray radiation by the Cygnus Cocoon0
is 8 + 0⌃Nh) MDsa e h(i.e.
i Fig.
µ ) is used as the parameter to discriminate
9
The angularoftheCygnus
Cocoon is about 2.1°, which trans1
forO
the sizeobserved
GeV
dec. = 40.93° ± 0.26°. The extension is well described by a therefore disfavoured as uniquely responsibleJ
ilshowers.
b ai edAs ishowng he in Fig. 2 in the paper, the muon cut
lates
intoS
a radius of r = 55 pc at 1.4?
kpc. The size of the Cocoon isMaterial[22].
A
Gaussian profile with a width of 2.13° ± 0.15° (stat.) ± 0.06° (syst.). and TeV flux.
A
L Hsimilar
ortional
The location and the Gaussian width of the source are consistent
The cosmic ray energy density
above a protonof 10and
TeVN
he a c to energy,aal eand ⌃⇢ = 1000 roughly corresponds toin bothenergy
the TeV
GeVR
energy range. Assuming a loss-free
S
,?
N
nd
1 shows arrival direcpc fromthe
OB2
(Fig.
2b).
with the measurements by Fermi-LAT from above 1 GeV to a few is calculated for four annuli up to 55
regime,particles
fromWetens of GeV to hundreds of TeV diffuse
W
e e discussion.—Figure
gie , e b ai
PallCyghundred GeV.
find that the cosmic ray energy density
spatialis larger
HAWC◦ 0.014 ◦ . events is more than 100, whilein theinregion
overbins
a timet given by t = r /(2D) (ref. ), where D
y035
backgroundthe Collaboration,
muon
2.0 cut±
The spectral energy distribution of the Cygnus Cocoon than the local cosmic ray energy density of 10 eVLHAASO
cm based onCollaboration,
mma-ray-likeeventsin(a)100ð¼10Þ
<E<
ApJ 881:134
is the particle
diffusion
If D(E ) = β D (E ), where D (E )ngedonb⌃⇢.KM2A
As a result,
we successfully suppress
99.92%(2019)of
has beenfrom 10 TeV PRL
in the 126,
previously
published
Alpha Magnetic Spectrometer measurements. Therefore,
as forcoefficient.
the
Tibet
AS 𝛾extended
Collaboration,
141101(2021)f
12 at a given energy E
2.2 the muon cut.
2.6
is theaveragediffusioncoefficientin the Galaxy
Nature,594, 33-36(2021)
measurementby thedirection
ARGO observatory
to 200 TeVgamma-ray-likein this GeV γ rays , TeV event
γ rays come fromthe freshly
accelerated
cosmicFIG. 1. The
arrivalof each
TeV,
(b)
ÞTeV,
aerve
gle24
le photon-likeha 158ð¼1050 ◦ , events afterÞ<E<398ð¼10andthanβ is fromthe suppression
coefficient, then at 10 GeV
analysis. The measurement above 0.75 TeV can be described rays inside the Cygnus Cocoon, rather
the older Galactic

sub-PeVガンマ線天⽂学の始まり
250

6Dec. (deg.)

23

3
2

22

1
0

21

-1

2

86

84
R.A. (deg.)

82

–1

336

Fig. 1 | Significance map around SNR G106.3+2.7 as observed by
Tibet AS+MD above 10!TeV. The inset figure shows our point spreadfunction (PSF). The red star with a 1σ statistical position error circle isthe centroid of gamma-ray emissions determined by this work, whereas
the magenta open cross, the black X mark and the blue triangle are thecentroids determined by VERITAS14, Fermi29 and HAWC15, respectively The
black contours indicate 1,420!MHz radio emissions from the Dominion
Radio Astrophysical Observatory synthesis telescope16,17, and the cyan
contours indicate 12CO emissions from the Five College Radio Astronomy
Observatory survey3. The grey diamond at the northeast corner of the radio
emission marks the pulsar PSR J2229+6114.
14

1

-3

The Astrophysical Journal, 881:134 (13pp), 2019 August 20

S

bution above 100 TeV for the Crab nebula events. Rµ is

package18, which allows us to estimate the parent particle spectrum
to best reproduce the observed gamma-ray energy spectrum.
For10
the energy distribution of the parent particles, we assume an exponential cut-off power-law form of dN=dE / E!α expð!E=Ecut Þ.
IWe provide the best-fit gamma-ray spectra
for hadronic6 and leptonic models (Extended Data Fig. 1) and list the best-fit parameters (Supplementary Table 2). In the hadronic model, we obtain
Ecut ≈ 0.5 PeV and α ≈ 1.8. The value of α falls between that preAbeysekara
et al.
dicted in thestandard
diffusive shock acceleration (α = 2) and theasymptotic limit of the very efficient proton acceleration (α = 1.5)
(refs. 19,20). The total energy of protons with energies10>1 GeV(>0.5 PeV) is estimated to be ~5.0 × 1047 erg (3.0 × 1046 erg) for a target gas density of 10 cm−3. One might argue that, considering theestimated SNR age of 10 kyr, PeV protons escape the SNR muchearlier than the present time in the standard theory of cosmic-ray
acceleration. Given that Ecut ≈ 0.5 PeV and that the maximum energy
of protons that remain inside an SNR is proportional to τ−0.5 whereτ is the SNR age21, protons should be accelerated up to ~1.6 PeV at
τ = 1 kyr in the case of G106.3+2.7. This suggests that the acceleration of protons at G106.3+2.7 should be efficient enough21 to pushtheir maximum energy up to ~1.6 PeV during the SNR free expansion phase. In addition, G106.3+2.7 has a dense molecular cloudnearby that is indispensable for accelerated protons to produce
TeV gamma rays via π0 production. With α ≈ 1.8, the proton energy
spectrum does not appear softened, which implies that protons may
not be able to escape the SNR easily owing to the suppression of the
diffusion coefficient (Supplementary Information). Future observations of the physical parameters of G106.3+2.7 such as the magnetic
field and the particle density could provide useful information forthese theoretical studies on its mechanisms of particle acceleration

0.5

HAWC J2030 + 409

1.0

1.5

–2

2.0

2.5

3.0

ϕ2 (deg2)

2
1
0

3.5

4.0

–1
–2

–3
Fig. 2 | Projected angular distribution of events observed above 10!TeV.
The–4 horizontal axis ϕ2 represents the square of the opening angle between
the estimated event arrival direction and the centroid of gamma-ray
emissions determined by this work. The red circles with 1σ statistical error
85 84 83 82 81 80 79 78 77 76 75 74
bars are the experimental data with the best-fit black curve (Methods).

–3
–4

–4

–2

0

2

4

6

8

10

12

14

10–11

HAWC

Fermi 4FGL

10–12

85 84 83 82 81 80 79 78 77 76 75 74 10(°) distribution by our Monte Carlo
The blue histogram is the expectedlevent
simulation assuming a point-like gamma-ray source.

Alternatively, the observed
gamma-rayemission might result
Significance(σ)
from protons accelerated by the SNR up to 0.1 PeV and thenre-accelerated up to 1 PeV by the adiabatic compression of the
Boomerang pulsar wind nebula (PWN) inside the SNR22. If theadiabatic compression ended at an age of 5 kyr as estimated in ref. 22,
accelerated PeV protons need to travel a distance of 6 pc from the
Boomerang PWN to the molecular cloud during the lapse timeof T = 5 kyr until the present time. The diffusion coeffiicient of a
0.5 PeV proton in the interstellar medium with a∘ magnetic field of
30
2 −1
23
3 μG would be p
Dffi≈
ffiffiffiffi2ffiffi × 10 cm s (ref. ), which gives a diffusion
length of L ! 2 DT = 380 pc (ref. 24) for T = 5 kyr. As the diffusion
I an SNR could be shorter by a factor of 10 or more25,
length around
we then estimate L ≲ 38 pc. As this is much larger than 6 pc, it would
be possible for 0.5 PeV protons to diffuse from the Boomerang
PWN to the molecular cloud and emit TeV gamma rays through π0
production. This scenario might not be natural, however, consid12,13
ering that TeV gamma-ray
emissions have not been detected fromother molecular cloud clumps around the source (Fig. 1, green contours) although protons should also be able to diffuse up to them,and considering that the proton spectrum needs to be kept hardwith α ≈ 1.8 after the diffusion of 6 pc for T = 5 kyr.
In the leptonic model, we obtain Ecut ≈ 190 TeV, α ≈ 2.3 and an
SNR magnetic field strength of ~9 μG. The total energy of relativistic
electrons with energies >10 MeV is estimated to be ~1.4 × 1047 erg.
We estimate (Supplementary Information) that electrons need to be
newly accelerated within 1 kyr if they originate from the SNR, andthat electrons provided by the Boomerang PWN are not likely to
produce the observed gamma-ray emission in view of the energy
budget and the gamma-ray morphology. The X-ray flux for thesmall 2′-radius region at PSR J2229+6114 has been measured in the
2−10 keV range6, whereas the X-ray flux for the extended regionof our gamma-ray emission region with the 1σ extent of 0.24° has
not been published yet, although X-ray data of the region observedby Suzaku, XMM-Newton and Chandra are publicly available(https://www.darts.isas.jaxa.jp/astro/suzaku/data/public_list/). We
point out that a flux upper limit14on the synchrotron spectrum at
the X-ray band would provide important information to rule out
the leptonic scenario for particle acceleration atΓ the gamma-rayФγ (TeV cm–2 s–1)

–1 0 0

10–10

3

b (°)

Number of events

2HWC J2031+ 415

HAWC J2031+ 415

0

A recent burst

4

2HWC J2019 + 367

338

Right ascension (deg)

30

-2

20

340

150

Continuous injection

5

Fermi-LAT Collaboration (2011)
Aharonian et al. (2019)

7

4

59

2

10–9

6

+ 36

C ra b
5

24

3
100

OB2 Association

0

4

7

019
C J2
2HW

1

5

150

3
+ 40
020
9
C J2
+ 40
2HW
030
C J2
415
HAW
031+
C J2
HAW

2

PSF

b (°)

3

60

6

4

Significance (σ)

Declination (deg)61

2HWC J2020 + 403

7

200

5

10

l (°)

–4

–2

0

2

4

6

8

10

12

ARGO

–13

9

1010

1011

1012

Eγ (eV)

1013

1014

1015

14

Significance (σ)

γ

11

14

19

19

19

16

10

17

Extended Data Fig. 5 | Phenomenological fits to the γ−ray observations of
diff
LHAASO J1908+0621, and previous observationsof potential
counterparts.
−3−3
The inset shows the KM2A significance map, indicating the potential
counterparts of the UHE γ-ray source.18
The colour bar shows the significance( TS ). The green circle indicates the PSF of LHAASO. The Fermi LAT points for
LHAASO J1908+0621 analysed in this work, as well as ARGO48, HESS 49 and
HAWC4 data, are shown together with the LHAASO measurements. The dottedcurve shows the leptonic model of radiation, assuming an injection of electron/
positron pairs according to the pulsar’s spin-down behaviour, with a breaking

20 Two types of
The solid curves correspond to2
the hadronic model of radiation.
diffenergy distributions
are assumed for the parent proton population: (i) a single* protons, N(E) ≈ E−1.85* exp[−E/(380 TeV)] (thin solid *power-law spectrum of parent
0 an exponential cutoff of parent
0
curve); (ii) a broken power-law spectrum with*
protons, with indices 1.2 and 2.7 below and above 25 TeV, respectively, and acutoff energy of 1.3 PeV (thick solid curve). In the inset sky map, the black
diamond shows the position of PSR J1907+0602, the black contours correspondto the location of supernova remnant SNR G40.5-0.5 and the white circle is the
position and size of HESS J1908+063. The cyan regions are the dense clumps

10% for 100 and 400 TeV, respectively. The
rgy scale uncertainty was estimated to be 12%
tward displacement of the Moon’s shadow center
NATURE ASTRONOMYLETTERSomagnetic field [21]. The live time of the dataset
NATURE ASTRONOMYLETTERS
NATURE ASTRONOMYnom February 2014 to May 2017, and the average
a
b
cocoo
a
ection time for the Galactic plane observation isgnusyTibet AS 𝛾 Collaboration,C
RSF
Nature Astron., 5, 460-464 (2021)
ly 3700 h at the zenith angle
lessthan 40°. The
NATUREASTRONOMYLETTERSn criteria are the same in our previous work [12]e muon cut condition. According to the CASA2.7
106.3+
2
ment, the marginal excess along the Galactic
SN R G
sub-PeVenergies is 1.63 σ, and the fraction of(b) E >100 TeV
smic-ray abackgroundbe45, 025002 (2021)
ASO-KM2Aef
a ce d events is estimated
Chi . Phto. C
ly 3 × 10−5 [18]. In order to search for signals
mall excess fraction, we adopt a tight muon cut innalyses requiring for gamma-ray-like events to
Fig. 2 | Spectral energy distribution of the γ-ray emission and cosmic ray demeasured by different γ-ray instruments. Here, Φ is the γ-ray flux, which is g
Collaboration,
NatureAstron.,5, 465-471 (2021)< 2.1 × 10−4 ðΣρÞ1.2 or ΣN μ < 0.4, where ΣN μ
Fig. 1 | Significance map of the Cocoon region before and after subtraction of the known HAWC
sources at theregion. a, Significance mapof the Cocoon
region.
measurements
for the Cocoon
in this study. The errors on the flux points are
Extended Data Fig. 1 | Spectral gamma-ray energy distribution of G106.3+2.7.Thea, Thepointswith 1σ statisticalmeasurements
mapflux
is indata
Galactic
coordinates,
where berror
and l bars
refer include
to latitude
and longitude, respectively. It is produced as described in ref. . The blue contours areby the ARGO observatory shown in grey squares . The red a
by Tibet
AS+MD(redunderground
dots; this work), Fermi (blue squares), VERITAS (purple
pentagons)
and theDominionRadio AstrophysicalObservatory’sTable 1. The green contour is the ROI used for themeasurements
number of muons detected
in
the
four
annuli centred
at theOB2 association
as listed in Supplementary
study, which masks the brightrespectively.
The(γ
grey
triangles
Synthesis Telescope (turquoise blue dots). The two red downward arrows above
10 4 eVshow
99% C.L. b,
upper
limits obtainedby thiswork.
Noteafterthatsubtracting HAWC J2031+415 (PWN) and 2HWC
source2HWC
J2019+367.
Significancemap of the
CocoonregionJ2020+403
Cygni).
The are from the Fermi-LAT analysis in ref. . The
all theorder
VERITAS data
are raised by a factor of 1.62 to account for the spill-overof gamma-ray
signalsoutside theirwindowof 0.32 radius.
of thefrom
region.
(The leptonic modelling results are provided in Extenlight-blue,
medium-blueand dark-bluedashedlines sizeare contours
for 0.16, 0.24 and 0.32 photons per 0.1°!×!0.1° spatialmodellingbin, respectively,
Fermi-LATor array. This is just one
ofpointsmagnitude
The best-fit gamma-ray energy spectrum in the leptonic model is shown by the Cocoon
black solid
curve,
withfluxassuming
by the electron
synchrotron(the. Bothmaps
arethemade
a 0.5° extended
disk radiation
source anda spectral index of −2.6 with 1,343 days of HAWC
data.
rings (0–15!pc,
15–29!pc, 29–44!pc and 44–55!pc) centred at the OB2 associaorange solid curve),
the IC scattering
CMB photons (the green dashed curve) and the IC scattering of IR photons (the light blue dash-dotted curve). The
he criterion used in our previous
work[12].ofTheusing HAWC γ-ray data. The y errors are the statistical errors and the x error
gray open diamond shows the flux of PSR J2229+6114 obtained in the 2!−!10 keV range . b, The best-fit gamma-ray energy spectrum in the hadronic model(signature of the continuous particle injection) and constant profile (signatu
is shown
by the turquoise
curve. The lower panels show the residual Δσofthe fit. (dec.) = 41.51° ± 0.04°), which is a slightly extended to be peaked toward the stellar clusters, but rather trace the difdeclination
urvivalratio
this tightmuon
cutblueissolidexperTibet
AS 𝛾withCollaboration,
symmetry for the γ-ray emission region and by averaging the density profile
source with a Gaussian width of 0.27° and is possibly associated fuse dust emission across the entire Cocoon. This adds difficulty toby the PRL
Tibet123,
AS+MD
array(2019)
for (a) E > 10
and for (b)localandcosmicray density
051101−6TeV
with the PWN TeV J2032+4130 (refs. ), and HAWC J2030+409, the task of distinguishing the leptonic
hadronic
originsaboveof the10!TeV based on Alpha Magnetic Spectromet
imatedtobeapproximately
10
above
400
TeV,
pulsar position.
from ref.
. emissionof the Cygnus
Cocoonwhich is a very-high-energy counterpart of the GeV Cygnus γ-ray radiation. The measurements100!GeV
a ce e ed
he C ab Neb la a h ee e e gLHAASO
a ge . σ Collaboration,i he ig a f he 2-di e i
Cocoon (Methods). The region after subtraction of HAWC above 10 TeV break the degeneracy of the two origins. As shown
mma-rayratio
is estimated
30%
by
KM2A. The c lsurvivale e e>56TeV
heig ifica
ce. S iChin.
he aPhys.
i to be
al
e
i
he
a
.
J2031+415 (PWN) and 2HWC J2020+403 (γ Cygni) is shown in Extended Data Fig. 1, we find it unlikely that a single electron
C45, 023002 (2021)
produces γ rays fromcosmic
GeV toray
the density
highest energy
in Fig. 1b.
profileby
above 100 GeV from ref. , which clearly
ASURED
BY THEMD ARRAY
lation. The
comparison
between the cosmic-ray
futostheetotal flux detected population
inverse-Compton emission without
its synchrotron
radiationAlternatively,
vioHAWC J2030+409 contributes
f~90%
favours
the 1/r profile.
the 1/r profile is less striking
DaitestC abi i (R.A. =1
at the ROI and is detected withstatistic (equation (1), likeli- lating the flux constraints posed by radio and X-ray observations.
62time.
for TeV cosmic rays becauseof their escapeeheMC
simulation
is described in Fig. S1 inhood ratio test), TS, of 195.2 at the position RA = 307.65° ± 0.30°, The leptonic origin of the γ-ray radiation by the Cygnus Cocoon0
is 8 + 0⌃Nh) MDsa e h(i.e.
i Fig.
µ ) is used as the parameter to discriminate
9
The angularoftheCygnus
Cocoon is about 2.1°, which trans1
forO
the sizeobserved
GeV
dec. = 40.93° ± 0.26°. The extension is well described by a therefore disfavoured as uniquely responsibleJ
ilshowers.
b ai edAs ishowng he in Fig. 2 in the paper, the muon cut
lates
intoS
a radius of r = 55 pc at 1.4?
kpc. The size of the Cocoon isMaterial[22].
A
Gaussian profile with a width of 2.13° ± 0.15° (stat.) ± 0.06° (syst.). and TeV flux.
A
L Hsimilar
ortional
The location and the Gaussian width of the source are consistent
The cosmic ray energy density
above a protonof 10and
TeVN
he a c to energy,aal eand ⌃⇢ = 1000 roughly corresponds toin bothenergy
the TeV
GeVR
energy range. Assuming a loss-free
S
,?
N
nd
1 shows arrival direcpc fromthe
OB2
(Fig.
2b).
with the measurements by Fermi-LAT from above 1 GeV to a few is calculated for four annuli up to 55
regime,particles
fromWetens of GeV to hundreds of TeV diffuse
W
e e discussion.—Figure
gie , e b ai
PallCyghundred GeV.
find that the cosmic ray energy density
spatialis larger
HAWC◦ 0.014 ◦ . events is more than 100, whilein theinregion
overbins
a timet given by t = r /(2D) (ref. ), where D
y035
backgroundthe Collaboration,
muon
2.0 cut±
The spectral energy distribution of the Cygnus Cocoon than the local cosmic ray energy density of 10 eVLHAASO
cm based onCollaboration,
mma-ray-likeeventsin(a)100ð¼10Þ
<E<
ApJ 881:134
is the particle
diffusion
If D(E ) = β D (E ), where D (E )ngedonb⌃⇢.KM2A
As a result,
we successfully suppress
99.92%(2019)of
has beenfrom 10 TeV PRL
in the 126,
previously
published
Alpha Magnetic Spectrometer measurements. Therefore,
as forcoefficient.
the
Tibet
AS 𝛾extended
Collaboration,
141101(2021)f
13 at a given energy E
2.2 the muon cut.
2.6
is theaveragediffusioncoefficientin the Galaxy
Nature,594, 33-36(2021)
measurementby thedirection
ARGO observatory
to 200 TeVgamma-ray-likein this GeV γ rays , TeV event
γ rays come fromthe freshly
accelerated
cosmicFIG. 1. The
arrivalof each
TeV,
(b)
ÞTeV,
aerve
gle24
le photon-likeha 158ð¼1050 ◦ , events afterÞ<E<398ð¼10andthanβ is fromthe suppression
coefficient, then at 10 GeV
analysis. The measurement above 0.75 TeV can be described rays inside the Cygnus Cocoon, rather
the older Galactic

sub-PeVガンマ線天⽂学の始まり
250

6Dec. (deg.)

23

3
2

22

1
0

21

-1

2

86

84
R.A. (deg.)

82

–1

336

The Astrophysical Journal, 881:134 (13pp), 2019 August 20

S

bution above 100 TeV for the Crab nebula events. Rµ is

HAWC J2030 + 409

1.0

1.5

–2

2.0

2.5

3.0

ϕ2 (deg2)

2
1
0

3.5

4.0

–1
–2

–3
Fig. 2 | Projected angular distribution of events observed above 10!TeV.
The–4 horizontal axis ϕ2 represents the square of the opening angle between
the estimated event arrival direction and the centroid of gamma-ray
emissions determined by this work. The red circles with 1σ statistical error
85 84 83 82 81 80 79 78 77 76 75 74
bars are the experimental data with the best-fit black curve (Methods).

–3
–4

14

package18, which allows us to estimate the parent particle spectrum
to best reproduce the observed gamma-ray energy spectrum.
For10
the energy distribution of the parent particles, we assume an exponential cut-off power-law form of dN=dE / E!α expð!E=Ecut Þ.
IWe provide the best-fit gamma-ray spectra
for hadronic6 and leptonic models (Extended Data Fig. 1) and list the best-fit parameters (Supplementary Table 2). In the hadronic model, we obtain
Ecut ≈ 0.5 PeV and α ≈ 1.8. The value of α falls between that preAbeysekara
et al.
dicted in thestandard
diffusive shock acceleration (α = 2) and theasymptotic limit of the very efficient proton acceleration (α = 1.5)
(refs. 19,20). The total energy of protons with energies10>1 GeV(>0.5 PeV) is estimated to be ~5.0 × 1047 erg (3.0 × 1046 erg) for a target gas density of 10 cm−3. One might argue that, considering theestimated SNR age of 10 kyr, PeV protons escape the SNR muchearlier than the present time in the standard theory of cosmic-ray
acceleration. Given that Ecut ≈ 0.5 PeV and that the maximum energy
of protons that remain inside an SNR is proportional to τ−0.5 whereτ is the SNR age21, protons should be accelerated up to ~1.6 PeV at
τ = 1 kyr in the case of G106.3+2.7. This suggests that the acceleration of protons at G106.3+2.7 should be efficient enough21 to pushtheir maximum energy up to ~1.6 PeV during the SNR free expansion phase. In addition, G106.3+2.7 has a dense molecular cloudnearby that is indispensable for accelerated protons to produce
TeV gamma rays via π0 production. With α ≈ 1.8, the proton energy
spectrum does not appear softened, which implies that protons may
not be able to escape the SNR easily owing to the suppression of the
diffusion coefficient (Supplementary Information). Future observations of the physical parameters of G106.3+2.7 such as the magnetic
field and the particle density could provide useful information forthese theoretical studies on its mechanisms of particle acceleration

–4

–2

0

2

4

6

8

10

12

14

10–11

HAWC

Fermi 4FGL

10–12

85 84 83 82 81 80 79 78 77 76 75 74 10(°) distribution by our Monte Carlo
The blue histogram is the expectedlevent
simulation assuming a point-like gamma-ray source.

Alternatively, the observed
gamma-rayemission might result
Significance(σ)
from protons accelerated by the SNR up to 0.1 PeV and thenre-accelerated up to 1 PeV by the adiabatic compression of the
Boomerang pulsar wind nebula (PWN) inside the SNR22. If theadiabatic compression ended at an age of 5 kyr as estimated in ref. 22,
accelerated PeV protons need to travel a distance of 6 pc from the
Boomerang PWN to the molecular cloud during the lapse timeof T = 5 kyr until the present time. The diffusion coeffiicient of a
0.5 PeV proton in the interstellar medium with a∘ magnetic field of
30
2 −1
23
3 μG would be p
Dffi≈
ffiffiffiffi2ffiffi × 10 cm s (ref. ), which gives a diffusion
length of L ! 2 DT = 380 pc (ref. 24) for T = 5 kyr. As the diffusion
I an SNR could be shorter by a factor of 10 or more25,
length around
we then estimate L ≲ 38 pc. As this is much larger than 6 pc, it would
be possible for 0.5 PeV protons to diffuse from the Boomerang
PWN to the molecular cloud and emit TeV gamma rays through π0
production. This scenario might not be natural, however, consid12,13
ering that TeV gamma-ray
emissions have not been detected fromother molecular cloud clumps around the source (Fig. 1, green contours) although protons should also be able to diffuse up to them,and considering that the proton spectrum needs to be kept hardwith α ≈ 1.8 after the diffusion of 6 pc for T = 5 kyr.
In the leptonic model, we obtain Ecut ≈ 190 TeV, α ≈ 2.3 and an
SNR magnetic field strength of ~9 μG. The total energy of relativistic
electrons with energies >10 MeV is estimated to be ~1.4 × 1047 erg.
We estimate (Supplementary Information) that electrons need to be
newly accelerated within 1 kyr if they originate from the SNR, andthat electrons provided by the Boomerang PWN are not likely to
produce the observed gamma-ray emission in view of the energy
budget and the gamma-ray morphology. The X-ray flux for thesmall 2′-radius region at PSR J2229+6114 has been measured in the
2−10 keV range6, whereas the X-ray flux for the extended regionof our gamma-ray emission region with the 1σ extent of 0.24° has
not been published yet, although X-ray data of the region observedby Suzaku, XMM-Newton and Chandra are publicly available(https://www.darts.isas.jaxa.jp/astro/suzaku/data/public_list/). We
point out that a flux upper limit14on the synchrotron spectrum at
the X-ray band would provide important information to rule out
the leptonic scenario for particle acceleration atΓ the gamma-rayФγ (TeV cm–2 s–1)

0.5

3

b (°)

2HWC J2031+ 415

Number of events–1 0 0

10–10

全て北半球！
Fig. 1 | Significance map around SNR G106.3+2.7 as observed by
Tibet AS+MD above 10!TeV. The inset figure shows our point spreadfunction (PSF). The red star with a 1σ statistical position error circle isthe centroid of gamma-ray emissions determined by this work, whereas
the magenta open cross, the black X mark and the blue triangle are thecentroids determined by VERITAS14, Fermi29 and HAWC15, respectively The
black contours indicate 1,420!MHz radio emissions from the Dominion
Radio Astrophysical Observatory synthesis telescope16,17, and the cyan
contours indicate 12CO emissions from the Five College Radio Astronomy
Observatory survey3. The grey diamond at the northeast corner of the radio
emission marks the pulsar PSR J2229+6114.
1-3

HAWC J2031+ 415

0

A recent burst

4

2HWC J2019 + 367

338

Right ascension (deg)

30

-2

20

340

150

Continuous injection

5

Fermi-LAT Collaboration (2011)
Aharonian et al. (2019)

7

4

59

2

10–9

6

+ 36

C ra b
5

24

3
100

OB2 Association

0

4

7

019
C J2
2HW

1

5

150

3
+ 40
020
9
C J2
+ 40
2HW
030
C J2
415
HAW
031+
C J2
HAW

2

PSF

b (°)

3

60

6

4

Significance (σ)

Declination (deg)61

2HWC J2020 + 403

7

200

5

10

l (°)

–4

–2

0

2

4

6

8

10

12

ARGO

–13

9

1010

1011

1012

Eγ (eV)

1013

1014

1015

14

Significance (σ)

γ

11

14

19

19

19

16

10

17

Extended Data Fig. 5 | Phenomenological fits to the γ−ray observations of
diff
LHAASO J1908+0621, and previous observationsof potential
counterparts.
−3−3
The inset shows the KM2A significance map, indicating the potential
counterparts of the UHE γ-ray source.18
The colour bar shows the significance( TS ). The green circle indicates the PSF of LHAASO. The Fermi LAT points for
LHAASO J1908+0621 analysed in this work, as well as ARGO48, HESS 49 and
HAWC4 data, are shown together with the LHAASO measurements. The dottedcurve shows the leptonic model of radiation, assuming an injection of electron/
positron pairs according to the pulsar’s spin-down behaviour, with a breaking

20 Two types of
The solid curves correspond to2
the hadronic model of radiation.
diffenergy distributions
are assumed for the parent proton population: (i) a single* protons, N(E) ≈ E−1.85* exp[−E/(380 TeV)] (thin solid *power-law spectrum of parent
0 an exponential cutoff of parent
0
curve); (ii) a broken power-law spectrum with*
protons, with indices 1.2 and 2.7 below and above 25 TeV, respectively, and acutoff energy of 1.3 PeV (thick solid curve). In the inset sky map, the black
diamond shows the position of PSR J1907+0602, the black contours correspondto the location of supernova remnant SNR G40.5-0.5 and the white circle is the
position and size of HESS J1908+063. The cyan regions are the dense clumps

ガンマ線で見た宇宙https://fermi.gsfc.nasa.gov/ssc/

GeVの宇宙• ⼈⼯衛星を利⽤• 輝く天の川（宇宙線と星間物質の反応）• 銀河系内外の多様な天体
14ガンマ線で見た宇宙https://fermi.gsfc.nasa.gov/ssc/

TeVの宇宙http://tevcat.uchicago.edu
http://magic.scphys.kyoto-u.ac.jp/Science/science.html• チェレンコフ望遠鏡による地上からの観測• 銀河系内外の多様な天体• 個々の天体を詳しく観測するが「地図」が描けない

15

ガンマ線で見た宇宙
Tibet
ASγ

https://fermi.gsfc.nasa.gov/ssc/

http://tevcat.uchicago.edu

Sub PeVの宇宙• チベット実験による地上からの観測• 輝く天の川銀河（注：既知天体の寄与は除いた図）• 銀河系の中⼼⽅向はどうなってるの？GeVもTeVの華やか！
16

ALPACA(Andes Large area PArticle detector
for Cosmic ray physics and Astronomy)

480
0m Observatory
UMSA CR
5200 m a.s.l.

Mt. Chacaltaya, Bolivia

46

44

42

40

00

00

00

00

m

m

m

ALPACA site
4740 m a.s.l.
4,740 m above sea level(16゜23’ S, 68゜08’ W)m

チベットの成功を南半球で！

La Paz1
177

ALPAQUITA construction in June 2022

• 2022年6⽉から建設再開（コロナ中断）• 97台の地上検出器設置完了• 2022年9⽉にデータ収集開始

18

Big Events!

E ~100 TeV
19

Moon Shadow
200

ALPAQUITA Moon Shadow
Angular Resolution = 1.0deg

Cumulative deficit events

100
0
-100

-1s

-200

-2s

-300
-400

-3s

-500

-4s

-600
-700
0

Observation time ~118 days

5000
10000
15000
Number of background events

20000

before calibration of the PMT transit time20

研究の状況
• チベット実験• データ収集の継続・解析• 過去のデータの新しい解析（機械学習の導⼊等）• ALPACA実験（修⼠では新しい装置の建設や⽴ち上げを学んでもらう）• 地上検出器の 97台が稼働中。これで初期性能確認。
このデータでM論• 地下ミュー粒⼦検出器1号機の建設（2023-2024年）• 地下ミュー粒⼦検出器1台＋地上100台でのガンマ線天⽂学開始（2024年-）• 地下ミューオン検出器2-4号機の建設（2025年）• フルスケール（地上400台＋地下4台）での運転(2025 or 2026年-)
みなさんはこのデータでD論を書く

21

⼤学院⽣の研究テーマ

素粒⼦物理

データ解析
• ALPACA初期データによる装置性能の検証• ⽉・太陽による宇宙線の影ー装置の性能＋太陽磁場変動の研究• ガンマ線天体の探索
シミュレーション• ガンマ線突発天体の探索• 暗⿊物質・原始ブラックホール等からのガンマ線の探索
機械学習• ミュー粒⼦を⽤いた宇宙線原⼦核組成の研究
宇宙物理• 空気シャワーの新しい解析⽅法の研究（機械学習）• 雷電場の空気シャワーへの影響
宇宙天気• ⾼エネルギー太陽フレア粒⼦の研究• ALPACA低エネルギー拡張の研究
新しい装置で新しいデータ（世界初）
BGの宇宙線も貴重なデータ• 将来計画Mega-ALPACAの研究
宇宙天気や地球⼤気も関係

装置の設置
装置の較正

フィールド
ワーク

22

⼤学院⽣の⽣活• M1前期：本郷の授業を優先して単位を取得• 授業のない⽇に柏で輪講ゼミ、論⽂紹介ゼミ（TAグループと合同）• 週に⼀回柏（+オンライン）で研究進捗報告会• ⼆ヶ⽉に⼀度、国内グループ会議• 隔週：海外共同研究者とオンライン会議（主にスタッフのみ）• 観測サイト出張は 1回/年程度、⼀ヶ⽉（南⽶・4,700mなので応相談）• M1後半から国内学会デビュー• M2：国内の国際会議デビュー• D：海外の国際会議デビュー、投稿論⽂執筆
23

銀河宇宙線・ガンマ線• 宇宙線の起源、Pevatronを探せ！
• PeVatronからのsub-PeV領域ガンマ線の検出!

﨏（Ａ８）⽐較的⼩規模でユニークな研究が好きな⽅、お待ちしております。
午後の個別説明会は宇宙線研建物の412室です
テレスコープアレイグループ（414室）と合わせてどうぞ

瀧田（Ａ８）（新規受け⼊れはなし）