above 1017.2 eV from the Hybrid Data of the Pierre Auger … · 2019. 8. 7. · Fluorescence Detector 2 High elevation Auger telescopes elevation 30 58 3 telescopes at Coihueco site

OBSERVATORY

Mass Composition of Cosmic Rays with Energies

above 1017.2 eV from the Hybrid Dataof the Pierre Auger Observatory

Alexey Yushkov∗ for the Pierre Auger Observatory†

∗ Institute of Physics of the Czech Academy of Sciences

† Av. San Martın Norte 304, 5613 Malargue, Argentina

http://www.auger.org/archive/authors icrc 2019.html

CRI2g (PoS 482)

Fluorescence Detector

2

High elevation Auger telescopes elevation 30◦ − 58◦

3 telescopes at Coihueco site

range of Xmax analysis: 1017.2 eV < E < 1018.1 eV

data: same to ICRC (2017) [J. Bellido, PoS(ICRC2017)506]

Standard telescopes elevation 1.5◦ − 30◦

24 telescopes at 4 sites

range of Xmax analysis: E > 1017.8 eV

compared to ICRC (2017): update with 2016− 2017 (+20% of statistics)

Figure 6: FD building at Los Leones during the day. Behind the building is a communication tower. Thisphoto was taken during daytime when shutters were opened because of maintenance.

Figure 7: Schematic view of a fluorescence telescope with a description of its main components.

Figure 8: Photo of a fluorescence telescope at Coihueco.

illuminating a camera in case of a malfunction of the shutter or a failure of the SlowControl System.

A simplified annular lens, which corrects spherical aberration and eliminates comaaberration, is mounted in the outer part of the aperture. The segmented corrector ringhas inner and outer radii of 850 and 1100 mm, respectively. Six corrector rings were

23

Measurements of the depth of shower maximum Xmax

3

event 102266222400

700 720 740 760 780 800 820]2 [g/cmmaxX

LL

LM

LA

CO

70 80 90 100 110E [EeV]

SD

LL

LM

LA

CO

]2slant depth [g/cm200 400 600 800 1000 1200

)]

2dE

/dX

[Pe

V/(

g/cm

0

20

40

60

80

100

120

140

47863 high-quality events

1020 events with E > 10 EeV

the highest energy 104± 9.5 EeV

systematics . 10 g cm−2

resolution

40 g cm−2 at 1017.2 eV

25 g cm−2 at 1017.8 eV

15 g cm−2 for E > 1019.0 eV

Rate of change of Xmax with energyOne of the most reliable observables for mass composition analysis

simulations: ≈ 60 [g cm−2/decade] for constant compositions

17.0 17.5 18.0 18.5 19.0 19.5 20.0lg(E/eV)

650675700725750775800825

X max

[g/

cm2 ]

[

[[

[ ± syst.

[

[

[

[ ± syst.

[

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[

[ ± syst.

[

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[ ± syst.

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[ ± syst.data ± stat

1018 1019 1020E[eV]

(77 ± 2) g/cm

2 /decade

(26 ± 2) g/cm2/decade

Composition is getting lighter below E0≈ 2 EeV and heavier afterwards4

Xmax moments: data vs simulations

5

Above E0≈ 2 EeV both Xmax moments are becoming compatible to MC predictions for heavier nuclei

17.0 17.5 18.0 18.5 19.0 19.5 20.0lg(E/eV)

600

650

700

750

800

850

X max

[g/

cm2 ]

proton

iron

± syst.

[

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EPOS-LHCSibyll2.3cQGSJetII-04

data ± stat

1018 1019 1020E[eV]

17.0 17.5 18.0 18.5 19.0 19.5 20.0lg(E/eV)

10

20

30

40

50

60

70

(Xm

ax)

[g/c

m2 ]

[

[

[

[

[

[

[

[ [

[

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1018 1019 1020E[eV]

Preliminary Preliminary

〈ln A〉 and σ2(ln A) from first two moments of Xmax distributions

0

1

2

3

4EPOS-LHC

lnA

± syst. data ± stat

17.0 17.5 18.0 18.5 19.0 19.5 20.02

1

0

1

2

3

4

2 (ln

A)

pure composition

QGSJETII 04

17.0 17.5 18.0 18.5 19.0 19.5 20.0

lg(E/eV)

SIBYLL 2.3c

p

He

N

Fe

17.0 17.5 18.0 18.5 19.0 19.5 20.0

PreliminaryPreliminaryPreliminary

PreliminaryPreliminary

Preliminary

Model-independent decrease of σ(ln A) until ∼ 1018.7 eV

Less model-dependent constraints on σ(ln A) near the ankle?6

Correlation between Xmax and signal in the surface detector

7

heavier nuclei produce shallower showers with larger signal (more muons)general characteristics of air showers / minor model dependence

[VEM]38* S

0 20 40 60 80 100

]-2

[g

cmm

ax* X

600

800

1000

19.0 − 18.5 = /eV)Elg( LHC - EPOS0.04 = Grproton,

0.12 = Griron,

LHC - EPOS0.04 = Grproton,

0.12 = Griron,

signal at 1000 m from the core scaled to 10 EeV, 38◦

Xm

axsc

ale

dto

10

EeV


7


[VEM]38* S

0 20 40 60 80 100

]-2

[g

cmm

ax* X

600

800

1000

19.0 − 18.5 = /eV)Elg( LHC - EPOS0.04 = Grproton,

0.12 = Griron,

LHC - EPOS0.04 = Grproton,

0.12 = Griron, Correlation for EPOS-LHC

pure beams σ(ln A) = 0

+0.04 for proton

+0.12 for iron

rG — ranking correlation coefficient [R. Gideon, R. Hollister, JASA 82 (1987) 656]


7


[VEM]38* S

0 20 40 60 80 100

]-2

[g

cmm

ax* X

600

800

1000

19.0 − 18.5 = /eV)Elg( LHC - EPOSp/Fe = 1/1

0.35− = Gr

LHC - EPOSp/Fe = 1/1

0.35− = Gr Correlation for EPOS-LHC


+0.04 for proton

+0.12 for iron

maximal mixing σ(ln A) ≈ 2

−0.35 for p/Fe= 1/1

rG — ranking correlation coefficient [R. Gideon, R. Hollister, JASA 82 (1987) 656]


7


[VEM]38* S

0 20 40 60 80 100

]-2

[g

cmm

ax* X

600

800

1000

19.0 − 18.5 = /eV)Elg( LHC - EPOSp/Fe = 1/1

0.35− = Gr

LHC - EPOSp/Fe = 1/1

0.35− = Gr Correlation for EPOS-LHC


+0.04 for proton

+0.12 for iron

maximal mixing σ(ln A) ≈ 2

−0.35 for p/Fe= 1/1

More negative correlation ⇒ more mixed composition

Correlation in data compared to pure beams

8

[VEM]38* S

0 20 40 60 80 100

]-2

[g

cmm

ax* X

600

800

1000

Auger19.0 − 18.5 = /eV)Elg(

0.017± 0.069 − = Gr2652 events

preliminary

correlation for protons

EPOS-LHC QGSJetII-04 Sibyll 2.3c+0.04 +0.12 +0.04

difference to data≈ 6.0σ ≈ 11.0σ ≈ 6.0σ

difference is larger for other pure beams

difference is > 5σ for all p−He mixes

primary composition near the ankle is mixed

nuclei with A > 4 needed to explain data

systematics plays only a minor role σsyst(rG) . +0.01−0.02

Dependence of correlation on σ(ln A)

)A(ln σ0.0 0.5 1.0 1.5 2.0

) 38* S,

max*

X (Gr

0.5−

0.4−

0.3−

0.2−

0.1−

0.0

0.1

0.2

0.3

QGSJET II.04

Data

0

1

2

3

4⟩ Aln ⟨

LHC - EPOS

0 > Grpure beams,

extreme mix p/Fe = 1/1

Mixtures of p, He, O, Fe(step in fractions = 10%)

9

Constraints on σ(ln A) from observed rG(X∗max, S∗38)

Data are compatible to 0.85 . σ(ln A) . 1.60

)A(ln σ0.0 0.5 1.0 1.5 2.0

) 38* S,

max*

X (Gr

0.5−

0.4−

0.3−

0.2−

0.1−

0.0

0.1

0.2

0.3

QGSJET II.04

Data

0

1

2

3

4⟩ Aln ⟨

LHC - EPOS

Auger

preliminary

19.0 − 18.5 = /eV)Elg(

10



)A(ln σ0.0 0.5 1.0 1.5 2.0

) 38* S,

max*

X (Gr

0.5−

0.4−

0.3−

0.2−

0.1−

0.0

0.1

0.2

0.3

QGSJET II.04

Data

0

1

2

3

4⟩ Aln ⟨

II.04 - QGSJet

Auger

preliminary

19.0 − 18.5 = /eV)Elg(

10



)A(ln σ0.0 0.5 1.0 1.5 2.0

) 38* S,

max*

X (Gr

0.5−

0.4−

0.3−

0.2−

0.1−

0.0

0.1

0.2

0.3

QGSJET II.04

Data

0

1

2

3

4⟩ Aln ⟨

2.3c Sibyll

Auger

preliminary

19.0 − 18.5 = /eV)Elg(

10

Energy dependence

new data are compatible to [Auger PLB 762 (2016)]: χ2/ndf = 5.4/4 (p-value = 0.25)

[eV]) / FDElg(18.5 19.0 19.5

) 38* S,

max*

X( Gr

0.5−

0.4−

0.3−

0.2−

0.1−

0.0

0.1

0.2

0.3

923 693

437

599

496

preliminary

LHC - EPOS proton iron p/Fe = 1/1

Auger ICRC 2019 Auger PLB (2016)Auger ICRC 2019 Auger PLB (2016)

11

Energy dependence

lg(E/eV) = 18.5− 18.7 (1616 events): rG = −0.141± 0.022, at 6.4σ from zero

[eV]) / FDElg(18.5 19.0 19.5

) 38* S,

max*

X( Gr

0.5−

0.4−

0.3−

0.2−

0.1−

0.0

0.1

0.2

0.3

923 693

437

599

496

preliminary



11

Energy dependence

above the ankle lg(E/eV) > 18.7 data are compatible to decrease of σ(ln A)

[eV]) / FDElg(18.5 19.0 19.5

) 38* S,

max*

X( Gr

0.5−

0.4−

0.3−

0.2−

0.1−

0.0

0.1

0.2

0.3

923 693

437

599

496

preliminary



11

Energy dependence

[eV]) / FDElg(18.5 19.0 19.5

) 38* S,

max*

X( Gr

0.5−

0.4−

0.3−

0.2−

0.1−

0.0

0.1

0.2

0.3

923 693

437

599

496

preliminary

2.3c Sibyll proton iron p/Fe = 1/1


11

Energy dependence

[eV]) / FDElg(18.5 19.0 19.5

) 38* S,

max*

X( Gr

0.5−

0.4−

0.3−

0.2−

0.1−

0.0

0.1

0.2

0.3

923 693

437

599

496

preliminary

II.04 - QGSJet proton iron p/Fe = 1/1


11

Results (independent of the hadronic models)

Xmax analysis

〈ln A〉: decreasing up to 2 EeV and increasing afterwards

σ(ln A): decreasing up to the ankle, more constant at higher energies

rG(X∗max, S∗38) analysis for lg(E/eV) = 18.5− 19.0

below the ankle the correlation in data is significantly, at 6.4σ from zero, negative

pure compositions and proton-helium mixes (all having rG > 0) are excluded

data are compatible to mixed compositions with σ(ln A) = 0.85− 1.60

above the ankle there are indications on decrease of σ(ln A) (more statistics is needed)

12

backups

13

The Pierre Auger Observatory

Fluorescence detector (FD)[longitudinal profile]

duty cycle 15 %

24 + 3 fluorescence telescopesat 4 locations

Surface detector (SD)[lateral distribution]

duty cycle 100 %

1660 water-Cherenkov stationsat 1500 m spacing, 3000 km2

61 water-Cherenkov stationsat 750 m spacing, 23.5 km2

Nucl. Instrum. Meth. A798 (2015) 172 Mendoza province, Argentina

14


15

FD telescopes at Los Morados

Figure 6: FD building at Los Leones during the day. Behind the building is a communication tower. Thisphoto was taken during daytime when shutters were opened because of maintenance.

Figure 7: Schematic view of a fluorescence telescope with a description of its main components.

Figure 8: Photo of a fluorescence telescope at Coihueco.

illuminating a camera in case of a malfunction of the shutter or a failure of the SlowControl System.

A simplified annular lens, which corrects spherical aberration and eliminates comaaberration, is mounted in the outer part of the aperture. The segmented corrector ringhas inner and outer radii of 850 and 1100 mm, respectively. Six corrector rings were

23

elevation 1.5◦ − 30◦


15

FD telescopes at Los Morados

]2slant depth [g/cm200 400 600 800 1000 1200

)]

2dE

/dX

[Pe

V/(

g/cm

0

20

40

60

80

100

120

140

Xmax, calorimetric energy

High Elevation Auger Telescopes (HEAT)

16

Detection of showers with E < 1018 eVelevation 30◦ − 58◦

High Elevation Auger Telescopes (HEAT)

16

Detection of showers with E < 1018 eV

$�

(*�+

FOV combined with Coihueco FD site

Surface detector

17

Water-Cherenkov station

Figure 3: A schematic view of a surface detector station in the field, showing its main components.

at around 1019 eV [41].

3. The surface detector

3.1. Overview

A surface detector station consists of a 3.6 m diameter water tank containing asealed liner with a reflective inner surface. The liner contains 12,000 liters of ultra-pure water. Three 9-inch diameter Photonis XP1805/D1 photomultiplier tubes (PMTs)are symmetrically distributed on the surface of the liner at a distance of 1.20 m fromthe tank center axis and look downward through windows of clear polyethylene intothe water. They record Cherenkov light produced by the passage of relativistic chargedparticles through the water. The tank height of 1.2 m makes it also sensitive to highenergy photons, which convert to electron-positron pairs in the water volume.

Each surface detector station is self-contained. A solar power system provides anaverage of 10 W for the PMTs and electronics package consisting of a processor, GPSreceiver, radio transceiver and power controller. The components of a surface detectorstation are shown in Figure 3. Ref. [42] describes the surface detector in detail.

Figure 1 shows the layout of the surface array and the FD buildings at its periphery.

3.2. The SD station

The tanks are made of polyethylene using the rotational molding, or rotomolding,process. This process, in simplified form, consists of putting a set amount of polyethy-lene resin inside a mold, then rotating the mold and heating it until the resin has meltedand uniformly coated the interior walls of the mold. The result is a low cost, tough,and uniform tank with robustness against the environmental elements. The carefullyselected, custom compounded polyethylene resins contained additives to enhance ul-traviolet protection. The interior two-thirds of the wall thickness was compounded with1% carbon black to guarantee light-tightness. The outer one-third was colored beigeto blend with the landscape. The tanks have an average wall thickness of 1.3 cm and anominal weight of 530 kg. The tanks do not exceed 1.6 m in height so that they can beshipped over the roads within transportation regulations.

15

Surface detector

17

Water-Cherenkov station signal at 1000 m from the core

[m]r500 1000 1500 2000 2500

Sig

nal [

VE

M]

1

10

210

310

E ∝ (1000) S

8 / /Ndf: 5.92χ

mass composition sensitivity: muons contribute from 40 to 90% to S(1000) depending on zenith angle

Documents

above 1017.2 eV from the Hybrid Data of the Pierre Auger … · 2019. 8. 7. · Fluorescence Detector 2 High elevation Auger telescopes elevation 30 58 3 telescopes at Coihueco site