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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 !