HEAT/AMIGA: the Pierre Auger Observatory at low energies

Federico Sánchez for the Pierre Auger Collaboration

UHECR 2014

Springdale Utah

OBSERVATORY

1

2

“In metaphorical terms the fluorescence technique resembles a beautiful prima donna who needs constant pampering. The she will sing with such beauty that shivers run up and down your spine. By contrast, the surface array technique reminds one of a chanteuse in a smoky bar who sings with the same passion no matter how she feels or how she is treated.” J. Cronin

With the enhancements, these two beautiful ladies are singing even better…

3

PIERRE AUGER OBSERVATORY ORIGINAL DESIGN

6060

6070

6080

6090

6100

6110

6120

6130

6140

440 450 460 470 480 490 500 510

Nor

thin

g(k

m)

Easting (km)

Main arrayFD Buildings

•  1600 water-Cherenkov in a triangular grid of 1500 m •  24 fluorescence telescopes in 4 sites on the periphery

Hybrid detector (FD)

(SD)

FD 0o x 30o FoV

10% duty cycle SD 10m2 stations 100% duty cycle Fully efficient at: •  3x1018 eV (SD alone) •  1x1018 eV (FD+SD)

Outstanding results on: •  energy spectrum •  arrival directions and •  composition

3000 km2 area SD

FD

(several reviews in this conference)

go for lower energies

4

PIERRE AUGER OBSERVATORY ENHANCED (POST 2008)

6060

6070

6080

6090

6100

6110

6120

6130

6140

440 450 460 470 480 490 500 510

Northing(km)

Easting (km)

AMIGA+

HEAT

Infill area

Main array

FD Buildings

•  1500 water-Cherenkov in a triangular grid of 1500 m •  24 fluorescence telescopes in 4 sites on the periphery •  3 extra FD telescopes with higher FoV •  42 extra water-Cherenkov stations with 750 m spacing •  61 new buried scintillator detectors

(FD) (SD) Multi-Hybrid

detector

(MD)

•  Reducing the grid spacing for SD and increasing the FoV range lower the Observatory energy threshold by 1 order of magnitude.

•  Several Auger results already extended.

23.5 km2 area

3000 km2 area

HEAT

AMIGA

FD extension 30o x 60o FoV

10% duty cycle SD 10m2 stations 100% duty cycle MD 30m2 buried scintillators Fully efficient at: •  3x1017 eV (SD alone) •  1x1017 eV (FD+SD)

5

Coihueco HEAT-down

Coihueco

HEAT-up 0o – 30o 0o – 30o

30o – 60o •  180 m from Coihueco FD •  3 tilt able telescopes •  AMIGA area in FoV (6 km) •  Operated as independent site

Horizontal mode: •  Full overlap with Coihueco FoV •  Service and maintenance •  Absolute calibration (drum) •  Cross-checks (alignment/pointing,

calibration)

HEAT: HIGH ELEVATION AUGER TELESCOPES CONCEPT

2011 ICRC, contribution #761, T.H.-J. Mathes

Upward mode: •  Main acquisition •  Allows low energy shower

detection •  Stably in operation since 06/2010

mcEntries 758Mean 0.01331RMS 0.1293

CO)/ECO-E

HEAT(E

-2 -1.5 -1 -0.5 0 0.5 1 1.5 2

no. e

vent

s in

dat

a

0

5

10

15

20

25

30

35

mcEntries 758Mean 0.01331RMS 0.1293

dataEntries 110Mean 0.01909RMS 0.1359

dataEntries 110Mean 0.01909RMS 0.1359

6

HEAT: HORIZONTAL POSITION

0o – 30o

Horizontal mode: •  Full overlap with Coihueco FOV •  Service and maintenance •  Absolute calibration (drum) •  Cross-checks (alignment/pointing,

calibration)

Coihueco HEAT-down

!"#$%&'()*+,&-.%/+*0,1,+2

• !"#$%&"'$()*&+,"$)-*-'"%#+• $).#/+)!+*(.*,"0)+'*.$+#1*)+0#$0$%#+

• -'"%$#$2+-*-(()*".'+&*!3")0+-• 1+4$"'$()-*5*1+-$0)*'(#+&")!+*6789

sensor at base-plate

sensor at base-plate – sensor at camera

Alignment: Tilting deviations < 0.1o

Relative change < 1%

Relative energy deviation wrt Coihueco FD around 1%

2011 ICRC, contribution #761, T.H.-J. Mathes

]2slant depth [g/cm300 400 500 600 700 800 900 10001100

)]2dE

/dX

[PeV

/(g/c

m

00.20.40.60.8

11.21.41.61.8

2 /Ndf= 265.8/3482

azimuth [deg]

elev

atio

n [d

eg]

0

10

20

30

40

50

60

6080100120140

7

HEAT: UPWARD POSITION

Coihueco

HEAT-up 0o – 30o

30o – 60o

Upward mode: •  Main acquisition •  Allows low energy shower

detection •  Stably in operation since 06/2010

2011 ICRC, contribution #761, T.H.-J. Mathes

8

HEAT: PERFORMANCE

Scheduled data-taking periods: •  Sun more than 18o below the

horizon •  Moon longer than 3 hours below

the horizon •  Illuminated fraction of the moon

less than 70% in the middle of night.

Hybrid on-time fraction

90% working efficiency

10% on-time

FD readiness

The mean length of the dark observation period is then 17 nights/month. HEAT trigger rate 0.026 Hz (0.012 Hz for standard FD)

2013 ICRC, contribution #1079, C. Bonifazi

20

E [eV]1018 1019 1020

�Xm

ax�[g

/cm

2 ]

650

700

750

800

850 data ± σstat± σsys

EPOS-LHCSibyll2.1QGSJetII-04

iron

proton

E [eV]1018 1019 1020

σ(X

max)[g

/cm

2 ]

0

10

20

30

40

50

60

70

80

iron

proton

Figure 13: Energy evolution of the first two central moments of the Xmax distribution compared to air-showersimulations for proton and iron primaries [80, 81, 95–98].

Figure 14: Average of the logarithmic mass and its variance estimated from data using different interaction models.The non-physical region of negative variance is indicated as the gray dashed region.

9

HEAT: PHYSICS RESULTS

From standard FD sites see V. De Souza’s talk on Wednesday

arXiv:1409.4809, submitted to Phys. Rev. D

20

E [eV]1018 1019 1020

�Xm

ax�[g

/cm

2 ]

650

700

750

800

850 data ± σstat± σsys

EPOS-LHCSibyll2.1QGSJetII-04

iron

proton

E [eV]1018 1019 1020

σ(X

max)[g

/cm

2 ]

0

10

20

30

40

50

60

70

80

iron

proton

Figure 13: Energy evolution of the first two central moments of the Xmax distribution compared to air-showersimulations for proton and iron primaries [80, 81, 95–98].

Figure 14: Average of the logarithmic mass and its variance estimated from data using different interaction models.The non-physical region of negative variance is indicated as the gray dashed region.

20

E [eV]1018 1019 1020

�Xm

ax�[g

/cm

2 ]

650

700

750

800

850 data ± σstat± σsys

EPOS-LHCSibyll2.1QGSJetII-04

iron

proton

E [eV]1018 1019 1020

σ(X

max)[g

/cm

2 ]

0

10

20

30

40

50

60

70

80

iron

proton

Figure 13: Energy evolution of the first two central moments of the Xmax distribution compared to air-showersimulations for proton and iron primaries [80, 81, 95–98].

Figure 14: Average of the logarithmic mass and its variance estimated from data using different interaction models.The non-physical region of negative variance is indicated as the gray dashed region.

10

HEAT: PHYSICS RESULTS

COMING SOON

J

1017

HEAT covers energy overlapping with other experiments (HiRes/MIA, Yakutsk, Tunka, TALE, …)

11

AMIGA: SD INFILL + BURIED SCINTILLATORS (MD)

SD infill completed in September 2012 MD unitary cell to be completed in 2014 (270m2 of scintillators in one hexagon)

19 regular & 42 extra SD stations 61 new MD stations (30m2 each)

Regular station (19) Extra stations (42)

23.5 km2 750 m spacing

MD Unitary Cell

Infilled SD stations identical to those of the main array: geometry reconstruction, exposure and energy estimator calculation, event selection criteria, LDFs, energy calibration calculation, all benefit from regular Auger array well proven algorithms

Analysis tools ready to go

12

AMIGA: SD INFILL TRIGGER EFFICIENCY

(E/eV)10

log17 17.5 18 18.5 19

3ToT

Effi

cien

cy

0

0.2

0.4

0.6

0.8

1

p, 750 m arrayFe, 750 m arrayp, 1500 m arrayFe, 1500 m array

Trigger e!ciency

From simulations

(E/eV)10

log17 17.5 18 18.5 19

3ToT

Effi

cien

cy

0

0.2

0.4

0.6

0.8

1

p infill arrayFe infill array

p regular arrayFe regular array

simulations

3 fold trigger, Time-over-Threshold,Lateral trigger probabilitiesparametrisation

dependency on zenith angle for < 100%

100% at 3! 1017 eV for zenith < 55!

From data

[VEM]35S10 20 30 40 100

/ nd

of2 !

1

10

100data

test the hypothesis of a flatdistribution in cos2 ! above ashower size (S35) value

100% at S35 " 20VEM

(" 3! 1017 eV)

Ioana C. Maris (Pierre Auger Collaboration) 2 / 11

Infill *

The 750 m spacing of the infill allows cosmic rays impinging with zenith angle < 55o to be detected down to an energy of 3×1017 eV with full efficiency. The muon

detectors (MD) trigger with the same SD signal.

Regular

From simulations: From data:

Test hypothesis of flat distribution in cos2θ 100% S35 > 20 VEMs (≈ 3 × 1017 eV )

(* Note: SD triggers MD)

Signal at reference distance (450m) and reference angle (35o)

1.  T3 trigger rate: (55±6) events/day/hexagon

2.  T5 (good quality): (28±3) events/day/hexagon

2011 ICRC, contribution #711, I. Maris 2011 ICRC, contribution #742, F. Sanchez

13

AMIGA: SD INFILL ANGULAR RESOLUTION & EXPOSURE

Events with more than 3 stations is better than 1.3o and is better

than 1o for events with more than 6 stations.

0

0.5

1

1.5

2

2.5

3

0 10 20 30 40 50 [o]

Ang

ular

reso

lutio

n [o ]

3 stations4 stations5 stations6 or more stations

17.0 17.5 18.0 18.5 19.0 19.5 20.0log10(E/eV)

101

102

103

104

105

expo

sure

� km2

sryr�

SD 1500 mSD inclinedHybridSD 750 m

08/2008 – 12/2012: 79±4 km2 sr yr

2011 ICRC, contribution #711, I. Maris 2013 ICRC, contribution #769, A. Schulz

[m]opt r300 400 500 600 700 800

entri

es

0

5000

10000

15000

20000

25000

30000 no saturation

50×saturation

14

1

10

100

1000

10000

200 400 600 800 1000 1200 1400 1600 1800

S(r)(V

EM)

r (m)

S(1000)=20.6±2.5

! = (27.5± 0.6)!

Lateral Distribution function S(r)Triggered stations

AMIGA: SD INFILL LDF, ROPT & ENERGY ESTIMATOR

1

10

100

1000

10000

200 400 600 800 1000 1200 1400 1600 1800

S(r)(V

EM)

r (m)

S(450)=276.6±11.4

! = (27.2± 0.2)!

Lateral Distribution function S(r)Triggered stations

non-Triggered stations

Regular only Infill

S(ropt) where shower-to-shower fluctuations and statistical uncertanties are minimal at (from LDF slope variations): ropt = 450 m

S35=S(450m,35o)

S35 is independent of the zenith angle and is used as energy estimator

2011 ICRC, contribution #711, I. Maris 2011 ICRC, contribution #742, F. Sanchez 2013 ICRC, contribution #693, D. Ravignani

E= 2.7 x 1018 eV θ = 27o

15

AMIGA: SD INFILL ENERGY CALIBRATION (WITH FD)

Golden hybrid events: events observed by the 750 m array in coincidence with telescopes of the

fluorescence detector located at the Coihueco and HEAT sites. 2013 ICRC, contribution #769, A. Schulz

16

AMIGA: SD INFILL PHYSICS RESULTS

17.5 18.0 18.5 19.0 19.5 20.0 20.5log10(E/eV)

1036

1037

1038

E3 J(E)

� eV2

km−

2sr

−1

yr−

1�

HybridSD 750 mSD 1500 mSD inclined

1018 1019 1020E [eV]

Auger 2013 preliminary

Spectrum

Not accessible

before

Anisotropy

Infill SD array + HEAT already started to deliver physics results 2013 ICRC, contribution #769, A. Schulz 2013 ICRC, contribution #739, I. Sidelnik 2013 ICRC, contribution #693, D. Ravignani

17

2013 ICRC, contribution #712, F. Suarez 2014, JINST 9 T04003, O. Wainberg et al.

2011, JINST 6 P06006, M. Platino et al.

AMIGA: BURIED SCINTILLATOR CONCEPT (MD)

≈ 25 radiation lengths in local soil

MD is an SD slave detector

•  No electromagetic contamination •  Ethreshold for muons of 1 GeV

320 MHz sampling (3.125 ns)

18 Black painted ends of each scintillator to

avoid reflection (fiber is also cut at 45o)

AMIGA: SCINTILLATOR MODULE CONSTRUCTION

64 polystyrene strips (1% PPO+0.03% POPOP) Each strip has TiO2 coating + WLS fiber glued

Signal read-out at only one end of the optical fibers

Buried detectors must be (at least):

1.  Robust 2.  Water-tight 3.  Free of maintenance 4.  Easy to manage 5.  …

Go to plastic!

Access to buried electronics through Small pipe (≈30 cm diameter)

Central dome to host electronics & PMT

19

2011 JINST, M. Platino et al. 2013 ICRC, contribution #748, S. Maldera

AMIGA: SCINTILLATOR MODULE TESTING

Algo de scanner acá d [mm]0 1000 2000 3000 4000 5000

µph

otoe

lect

rons

/

2

4

6

8

10

12

14

16

18

20

~15 phe

Avoid undercounting

Avoid overcounting

P(5,X < 2) = 0.04

~5 phe

Figure 5: The AMIGA scanner. The top panel shows a schematic of the interconnections between

the two micro controllers, the user PC, the motors and the security switches and speed monitors.

The bottom panel shows a photo of the scanner performing a test measurement on a scintillator

module before its shipment to the Pierre Auger Observatory.

The relative distance between the radioactive source and the top of the scintillator module 186

should not change in a factor greater than±1 cm in order not to affect the measurements due to the 187

dispersion of the radiation as it propagates away from its source into space. As can be seen in Figure 188

6, the radioactive source itself is mounted on a screw inside the cylinder at least 70 mm from the 189

bottom, which in turn is located at least 50 mm ± 10 mm from the scintillator bar, accounting for 190

a total distance of 120 mm ± 10 mm from the source itself to the scintillator. As the radiation flux 191

changes with distance following a r−2law, the maximum change in flux produced by a variation 192

in distance of 1 cm is ∼ 17%. This factor can lead to a measurement error if we do not take it 193

into account or compensate it accordingly. In order to do that, we align the module by carefully 194

– 8 –

Lab. automated scanning

20

AMIGA: SCINTILLATOR BURIED ELECTRONICS Two main features:

Buried electronics

With 1) and a counting strategy we get rid of PMT optical cross-talk and clipping-corner With 2) we get rid of muon pile-up due to finite segmentation close to the core

Common Dynode (integrator)

1) Signal 1-bit digitization over each individual strip (64 channels).

2) Signal integration over all strips (1 channel).

2014, JINST 9 T04003, O. Wainberg et al.

21

20 30 40 50 60 70 80 90

0

200

400

600

800

1000

Time (ns)

disc

rimin

ator

out

put v

olta

ge (m

V)

0

500

1000

1500

2000

2500

3000

discriminationlevel

outcomingpulse

discriminatoroutput

FPGAdigital

samples

fron

t-end

out

put v

olta

ge (m

V)

AMIGA: COUNTING STRATEGIES

000000011100000000000000100000… Raw “1-bit” trace per scintillator strip

If only “0” or “1” are in the event ¿What is the best strategy to identify a muon? (will depend on the amount of light + time width per muon)

2011 ICRC, contribution #341, B. Wundheiler

22

discrimination threshold (mV)60 80 100 120 140 160 180 200 220

coun

ted

/ im

ping

ing

muo

ns

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

1.4Main Pixel

2G30ns2C30ns2Q30ns

Neighbor Pixels2G30ns2C30ns2Q30ns

> le

vel

spe

~30%

<V

AMIGA: COUNTING STRATEGIES

Strategy: 2G30ns 1X1XXXX…XXXX …….1X1XXXX………….

Time window w1 Time window w2

Get rid of PMT cross-talk signals & clipping-corners

Robust reconstruction method that does not relies on the signal amplitude fluctuations nor on the impinging muon position over the strips. Only limited by detector segmentation (pile-up effect noticeable in close-to-the-core stations)

569 0000000000000000000000000000000000000000000000000000010000000000 570 0000000000000000000000000000000000000000000000000000010000000000 571 0000000000000000000000000000000000000000000000000000010000000000 577 0000000000000000000000000000000000000000000000000000000000001000 578 0000000000000000000000000000000000000000000000000000000000001000 579 0000000000000000000000000000000000000000000000000000000000101000 580 0000000000000000000000000000000000000000000000000000000000100000 589 0000000000000000000000000000000000001000000000000000000000000000 590 0000000000000000000000000100000000001000000000000000000000000000 591 0000000000000000000000000100000000000001000000000000000000000000 592 0000000000000000000000000100000000000001000000000000000000000000 593 0000000000000000000000000100000000000000000000000000000000000000 595 0000000000000000000000000100000000000000000000000000000000000000 596 0000000000000000000000000100000000000000000000000000000000000000 597 0000000000000000000000000100000000000000000000000000000000000000 598 0000000000000000000000000100000000000000000000000000000000000000

23

Example of a real raw event at 320 MHz: Ti

me

/ 3.1

25 n

s

64 Channels

Full null samples (64 “0”s) are not displayed (nor transmitted)

25 n

s

t2

Individual muon times (t1, t2, … tn) measured with 3.125 ns resolution

2014, JINST 9 T04003, O. Wainberg

t1

t3

+

+

3 muons Not a muon

muon

muon

muon

AMIGA: COUNTING STRATEGIES

=

24

•  22 modules fully installed (20 @ 2.5 m & 2 @ 1.3 m depth). •  1 module with SiPMs prototype •  2 twin detector pairs for validation and accuracy estimation

@ 1.3 m depth

AMIGA: MD UNITARY CELL

Twin detectors

Twin detectors

Access tubes to electronics

25

AMIGA: MD VALIDATION FROM TWINS

2013 ICRC, contribution #748, S. Maldera

The data from twin detectors will allow the counting procedure to be experimentally assessed

Preliminary

r [m]0 500 1000 1500 2000 2500 3000

]2/mµ

MD

[⎯

] 2SD

[VE

M/m

-110

1

10

210

310SD dataMD data

26

SD and MD reconstruction

E > 1019 eV & θ = 40 o

AMIGA: MD+SD EVENT EXAMPLE

First data from MD prototype hexagon demonstrate the potential of a dedicated muon detector observing (singing) alongside the SD and the FD

r [m]

200 400 600(450)

µ/

µ

1

10° < 30 < °0

° < 45 < °30

< °45

MD LDFs by angular bin

2013 ICRC, contribution #748, S. Maldera

27

CONCLUSION: 1.  AMIGA and HEAT have lowered the energy threshold of

Auger down to 1x1017 eV. 2.  Already provided results on the all-particle spectrum and

anisotropy.

3.  A dedicated muon detector is being built. It is foreseen to be fully operative by the end 2016 (prototype phase ends in 2014).

Thanks

BACKUP

28

PRINCIPLES OF OPERATION: DEPTH & SHIELDING

29

50 GeV µ- 50 GeV γ

Energy deposition in 1 strip irrespective of muon energy

If not shielded enough, energy deposition can occur in several strips

Soil Soil

¿depth?

Optimal depth should: 1.  Not stop too many muons 2.  Shield the electromagnetic component

Assessed by simulations and can be validated by data using module at different depths (2.5m Vs 1.3m)

G4 sims G4 sims

red path are e±

0 g/cm2

540 g/cm2 (~25 radiation

lengths)