Neutrino search in AugerRicardo A. Vázquez

University of Santiago de Compostela, Spain

for the Pierre Auger collaboration

Beijing, April 2006

1.The Pierre Auger Observatory

2. Neutrino Search:

3. Fluorescence Detector (FD) Search

4. Surface Detector Search

5. Conclusions

The Pierre Auger Observatory

Aims at measuring The Highest Energy Cosmic Rays

Energy Spectrum - Direction – Composition - AnisotropyHybrid detection: Fluorescence and Surface detectors

Two Large Air Shower DetectorsMendoza Province, Argentina (under construction)Colorado, USA

The Auger CollaborationParticipating CountriesArgentina MexicoAustralia NetherlandsBolivia* PolandBrazil Slovenia Czech Republic SpainFrance United Kingdom Germany USAItaly Vietnam* *Associate

63 Institutions, 369 Collaborators

Surface Array100% duty cycleUniform sky coverageSimple robust detectorsMass determination using rise time,

& muon/em

Fluorescence DetectorCalorimetric energy measurementDirect view of shower development:Xmax measurement, mass

determinationGood angular resolution (< 1o)

Hybrid concept

Advantages• Independent measurement techniques allow cross

calibration and control of systematics

• More reliable energy and geometry reconstruction

• Primary mass

Hybrid concept:

Surface Detector Array and Fluorescence Detectors

Two observatories: allow full sky coverage

Auger Southern

Site

Mendoza province, Argentina

The Observatory Plan

Surface Array 1600 detector stations 1.5 km spacing 3000 km2

Fluorescence Detectors 4 Telescope enclosures 6 Telescopes per

enclosure 24 Telescopes total

The Auger Surface Detector

Three 8” PM Tubes

Plastic tank

White light diffusing liner

12 m2 of de-ionized water

Solar panel and electronic box

Commantenna

GPSantenna

Battery box

Fluorescence Detector Building

at Los Leones

The Fluorescence Detector

3.4 meter diameter segmented mirror

Aperture stop and optical filter

440 pixel camera

Atmospherecalibrated (movable) light sourcescloud monitors

LIDARlasers

balloon sondes

2. Intl Workshop Liebenzell Castle

Dec 11-14

On-line monitoring(Big Brother) • Detector elements are monitorized every 10 mins.• Alarms inform about anomalies.

Auger Center Building

Detector Assembly Building

Cerenkov detector tanks being prepared for deployment

The Auger Campus

The communications system

Rigging the antennas

Array status by the End 2004337 tanks deployed

~100% duty cycle

905 surface detector stations deployed

Three fluorescence buildings complete each with 6 telescopes

End of 2005

Status of the array @ March 2006 ~ 1000 stations

The First Data SetCollection period – 1 January

2004 to 5 June 2005

Zenith angles - 0 - 60º

Total acceptance – 1750km2 sr yr

(~ AGASA)

Surface array events (after quality cuts)

Current rate - 18,000 / month

Total -~180,000

Hybrid events (after quality cuts)

Current rate – 1800 / month

Total ~ 18000

Cumulative number of eventsJa

nu

ary

04

July

04

Jan

ua

ry 0

5

Official First FD Event

Surface Detector First 4 – fold event – 12 August

Flash ADC traces

Lateral density distribution

Hybrid Event Θ~ 30º, ~ 8 EeV

Fitted Electromagnetic Shower

from Fly's Eye 1985

Tim

e μ

sec

Angle Χ in the shower-detector plane

Hybrid EventΘ~ 30º, ~ 8 EeV

Tanks

Pixels

Example Event Θ~ 48º, ~ 70 EeV

Flash ADC tracesFlash ADC traces

Lateral density distribution

Typical flash ADC trace

Detector signal (VEM) vs time (ns)

PMT 1

PMT 2

PMT 3

Lateral density distribution

Surface Detector Event Θ~ 60º, ~ 86 EeV

Flash ADC traces

Flash ADC Trace for detector late in the shower

PMT 1

PMT 2

PMT 3

Hybrid event

Performance: Resolution of Core Position

Hybrid – SD only core position

Hybrid DataLaser Data

Core position resolution

– Hybrid: < 60 m Surface array: ~150 m

Laser position – Hybrid and FD only (m)

-500

+500

En

trie

s 5

01

M

ea

n

5.8

± 6

.5 m

RM

S

14

7 m

Entries 501 Mean 68 ± 8 m RMS 173 m

Performance: Angular Resolution

Surface array Angular resolution (68% CL)< 2.2º for 3 station events (E< 3EeV, θ <

60º )< 1.7º for 4 station events (3<E<10 EeV)< 1.4º for 5 or more station events (E>10

EeV)

Hybrid Angular resolution (68% CL) 0.6 degrees (mean)

Hybrid-SD only space angle difference

Hybrid Data

Angle in laser beam /FD detector plane

Laser Beam

Entries 269

σ(ψ) = 1.24º

Energy Determination and the Spectrum

The detector signal size at 1000 meters from the shower core - called the ground parameter or S(1000) - is determined for each surface detector event using the lateral density function. S(1000) is proportional to the primary energy.

The energy scale is based on fluorescence measurements without reliance on a specific interaction model or assumptions about the composition.

Zenith angle ~ 48º

Energy ~ 70EeV

Energy Determination and the Spectrum

The energy converter:

Compare ground parameter S(1000) with the fluorescence detector energy.

Transfer the energy converter to the surface array only events.

Log S(1000)

Log (

E/E

eV

) 10EeV

1 EeV

Hybrid EventsStrict event selection: track length >350g/cm2 Cherenkov contamination <10%

Auger Energy Spectrum

E/E~30%

E/E~50%

ICRC 2005 spectrum

Neutrino search in Auger• FD search

– Auger can detect neutrinos directly with the

fluorescence detector

• SD search– Deep inclined (neutrino) showers should have

a different time structure (risetime/falltime), curvature, etc. and electromagnetic component Different strategies

M. Roth et al., Karlsruhe

FD search

M. Roth, Karlsruhe

a real vertical event (20 deg)

Noise !

doublet

SD search

a real horizontal event (80 deg)

“single” peaks : fast rise + exp. light decay ( ~ 70 ns) accidental background signals are similar

Simulated + (5.1) 0(16.1) 1800 m above ground

EM signal in shower plane

Proton

1 EeV

θ = 80 deg

x shower plane [m]

y s

how

er

pla

ne

[m]

[VEM]

ρ, ε → Sμ,EM

3167 g/cm2

3306 g/cm2

3570 g/cm2

3968 g/cm2

4100 g/cm2

4238 g/cm2

4371 g/cm2

4503 g/cm2

4636 g/cm2

4768 g/cm2

4901 g/cm2

3438 g/cm2

3703 g/cm2

3035 g/cm2

Xinjection

J. Alvarez-Muniz

Downgoing showers

Controlled calculation: strategyWe need ΔX where neutrino triggers are expected → Effective volume

Calculate size of active region (where SEM>Sthreshold)

2D EM signal maps at ground

EM signal [VEM]

x [km]

y [km]

Proton, E = 1017 eV, hint = 0 m

θ = 90.1 deg θ = 90.5 deg θ = 91 deg θ = 110 deg θ = 92 deg θ = 93 deg θ = 95 deg θ = 100 deg θ = 105 deg

AIRES + SIBYLL 2.1

Fixed proton interaction height hint = 0 m

J. Alvarez-Muniz

Upcoming showers

2D EM signal maps at ground

EM signal [VEM]

x [km]

y [km]Proton, E = 1017 eV, θ = 91 deg.

hint = 0 m

AIRES + SIBYLL 2.1

hint = 50 mhint = 100 mhint = 300 mhint = 500 mhint = 1000 mhint = 3000 m

Fixed zenith angle θ = 91 deg.

J. Alvarez-Muniz

Event 850018

Event 1432390

= 71.5±0.02 = -57.2±0.02E ~ 50 EeV R= 22.9 km /dof =2.4NTanks =48

= 77.1± 0.01 = -36.1 ± 0.01E ~ 30 EeV R= 33.11 km/dof =1.81NTanks = 59

Some events

Event 767138

= 87.6 = -134.9E ~ 30 EeV/dof =1.7NTanks = 37

Post-San Valentin day eventEvent 1999991

= 83 = -102E ~ 40 EeV

/dof =2.3NTanks = 61

10% 50%• Risetime is defined as the time from 10% - 50% of the integrated pulse.• Falltime time from 50% - 90%

Risetime/Falltime S [VEM]

90%

Falltime vs Risetime (2 cuts)S ≥ 15 VEM & r ≥ 500 m

θ ≥ 70 deg.

θ ≤ 45 deg.

Neutrino candidates should have θ ≥ 70 deg and should show up here.

No events up to now!

L Cazon, RAV, A. Watson, E. Zas (Ap Phys 2004)

Curvature analysis

Arrival Time of first muon (& average)

-like delay large

p-like delay:small (flat)

L. Cazon, RAV, E. Zas

footprint analysis

Variables defined from the footprint (in any configuration, even aligned)

• length L and width W (major and minor axis of the ellipsoid of inertia)• “speed” for each pair of stations (distance/difference of time)

major axis

titjdij

P. Billoir & O. Blanch

candidate selection 2. Discriminating variables

cuts: L/W > 5 0.29 < av. Speed < 0.31 r.m.s. < 0.08

Search for long shaped configurations, compatible with a front moving horizontally at speed c, well contained inside the array(background: vertical or inclined showers, d/Dt > c )

from years 2004-2005: no real event survived…

Auger sensitivity

Points: 1 event / year / decade of energy

“pessimistic

” energy loss

un

cert

ain

ty

ran

ge

GRB

TD

AGN GZK

prelim

inary

P. Billoir & O. Blanch

3C2 & 4C42C1 & 3C2 & 4C4

2C1 & 4C23C1 & 4C2

not saturated yet at 1019 eV

compacity ofthe trigger matters !

L. Nellen, V. Van Elewyck & RAV

Log(E/eV)

Understanding the background: HAS

Optimal trigger?

Conclusions

-The Pierre Auger Observatory is performing well and steadily taking data

-Due to the Hybrid characteristics several neutrino searches are possible

-Need to understand the background, model dependence on the aperture, systematics,….

-We will keep looking for neutrinos !