Transcript Document

7th International Conference on Radiation Effects on
Semiconductor Materials, Detectors and Devices (RESMDD)
15-17 October 2008
Florence
Astroparticle Physics at LHC:
the LHCf experiment ready for
data taking
Massimo Bongi - INFN Florence
LHCf Collaboration
Massimo Bongi - RESMDD08 - 15 October 2008 - Florence
Overview
• Cosmic-Ray Physics goals
– Ultra-High-Energy CR spectrum
– composition of High-Energy CR
(Monte Carlo codes calibration)
• LHCf detectors and experimental set-up
• Physics performance
• Current status
Massimo Bongi - RESMDD08 - 15 October 2008 - Florence
Ultra-High-Energy Cosmic Rays
Extensive Air Showers
Experimental observations:
(shower of secondary particles)
•lateral distribution
•longitudinal distribution
•particle type
•arrival direction
Air shower development
(particle interaction in the
atmosphere)
Astrophysical parameters:
(primary particles)
•spectrum
•composition
•source distribution
•origin and propagation
Massimo Bongi - RESMDD08 - 15 October 2008 - Florence
UHECR spectra and the GZK cutoff
AGASA x
HiRes x
Yakutsk x
Auger x
0.9
1.2
0.75
1.2
Massimo Bongi - RESMDD08 - 15 October 2008 - Florence
UHECR spectra and the GZK cutoff
GZK cutoff would limit energy to
1020eV (for protons, due to
Cosmic Microwave Background):
p + γ(2.7K)  Δ  N + π
Different hadronic interaction
models give different answers
for the primary CR energy
estimate.
Calibration of models with
experimental data
(for instance, AGASA reports
18% as systematic uncertainty in
energy determination, 10% being
due to the interaction model)
Massimo Bongi - RESMDD08 - 15 October 2008 - Florence
The depth of the
maximum of the
shower Xmax in the
atmosphere depends
on energy and type
of the primary
particle.
Xmax(g/cm2)
HECR composition
Different hadronic
interaction models
give different
answers about the
composition of
HECR.
UA7
LHCf
Massimo Bongi - RESMDD08 - 15 October 2008 - Florence
Energy(eV)
HECR composition
Xmax measurements
favors heavier
composition as the
energy increases
Auger
Anisotropy would
favor proton
primaries (AGN
correlation)
Massimo Bongi - RESMDD08 - 15 October 2008 - Florence
Development of atmospheric showers
1019 eV proton
The dominant contribution to the
shower development comes from
particles emitted at low angles in
the interaction of the primary CR
(forward region).
The knowledge of the π-production
cross-section in the forward
region is needed in order to
correctly estimate the energy of
the primary CR.
The highest-energy data currently
available are at 1014 eV
(UA7@SppS, 1990)
Massimo Bongi - RESMDD08 - 15 October 2008 - Florence
Astroparticle Physics at LHC
• LHCf will use the highest
energy particle accelerator to
provide useful data to
calibrate the hadronic
interaction models used in
Monte Carlo simulations of
atmospheric showers.
• 7 TeV + 7 TeV proton collisions at LHC (ECM = 14 TeV)
correspond to ELAB = 1017 eV (ELAB ≈ ECM2/(2mp))
Massimo Bongi - RESMDD08 - 15 October 2008 - Florence
The LHCf Collaboration
CERN
D.Macina, A.L. Perrot
USA
LBNL Berkeley:
W. Turner
FRANCE
Ecole Politechnique Paris:
M. Haguenauer
SPAIN
IFIC Valencia:
A.Fauss, J.Velasco
ITALY
Firenze University and INFN:
O.Adriani, L.Bonechi, M.Bongi,
G.Castellini, R.D’Alessandro,
P.Papini, S. Ricciarini, A. Viciani
Catania University and INFN:
A.Tricomi
JAPAN:
STE Laboratory Nagoya University:
K.Fukui,Y.Itow, T.Mase,
K.Masuda,Y.Matsubara,
H.Menjo,T.Sako, K.Taki, H. Watanabe
Waseda University: K. Kasahara, M.
Mizuishi, Y.Shimizu, S.Torii
Konan University: Y.Muraki
Kanagawa University Yokohama:
T.Tamura
Shibaura Institute of Technology: K.
Yoshida
Massimo Bongi - RESMDD08 - 15 October 2008 - Florence
The LHC ring
ATLAS (IP1)
Massimo Bongi - RESMDD08 - 15 October 2008 - Florence
Experimental set-up
Arm#1
Tungsten
Scintillator
Scintillating fibers
INTERACTION POINT
IP1 (ATLAS)
140 m
Arm#2
Tungsten
Scintillator
Silicon microstrips
140 m
Beam line
Two independent electromagnetic calorimeters equipped
with position sensitive layers, on both sides of IP1 will
measure energy and position of γ from π0 decays.
Massimo Bongi - RESMDD08 - 15 October 2008 - Florence
Protons
Experimental set-up
Charged particles
Neutral particles
Beam pipe
• The detectors are installed in the TAN region, where the beam pipe splits
into 2 separate tubes.
• Charged particles are deflected away, only neutral particles hit the
detectors.
LHCf
96 mm
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Arm#1 detector
 2 towers stacked vertically
with 5 mm gap
Scintillating Fibers
4 pairs of layers (6, 10, 32, 38 r.l.)
tracking measurements
 24 cm long
 upper: 4.0 cm x 4.0 cm area
 lower: 2.0 cm x 2.0 cm area
Absorber
22 tungsten layers
7mm – 14 mm thick
Plastic Scintillator
(W: X0 = 3.5mm, RM = 9mm)
16 layers
3 mm thick
trigger and energy profile measurements
Massimo Bongi - RESMDD08 - 15 October 2008 - Florence
Arm#2 detector
 2 towers stacked on their
edges and offset from one
Silicon Microstrip (from ATLAS SCT)
4 pairs of layers (6, 12, 30, 42 r.l.)
tracking measurements
another
 24 cm long
 upper: 3.2 cm x 3.2 cm area
 lower: 2.5 cm x 2.5 cm area
Absorber
22 tungsten layers
7mm – 14 mm thick
Plastic Scintillator
(W: X0 = 3.5mm, RM = 9mm)
16 layers
3 mm thick
trigger and energy profile measurements
Massimo Bongi - RESMDD08 - 15 October 2008 - Florence
The detectors are ready since
2007
Arm#1 detector
Arm#2 detector
Massimo Bongi - RESMDD08 - 15 October 2008 - Florence
Front Counter
• 2 Scintillator Counters
• installed in front of
Arm#1 and Arm#2
• segmented in 2 X and 2 Y
slices
• check the beam quality,
reduce background events
and decide whether to
move Arm#1 and Arm#2
in the operating position
from the “garage” position
Massimo Bongi - RESMDD08 - 15 October 2008 - Florence
LHCf Physics


Single photon spectrum
p0 mass reconstrucion (1 photon in each tower)
p0 reconstruction is an important tool for energy calibration (p0 invariant
mass constraint)
Basic concept:
•
2 towers for p0 reconstruction
•
Smallest tower on the beam (to reduce multiple hits)
•
Dimension of the tower  Moliere radius
•
Maximum acceptance (given the LHC and TAN constraints)
Simulation has been used to understand the physics performances
Beam tests in 2004, 2006 and 2007, to evaluate:
•
energy resolution
•
spatial resolution of the tracking part
Massimo Bongi - RESMDD08 - 15 October 2008 - Florence
LHCf acceptance on PT-E  plane
140
A vertical beam crossing angle > 0 will
increase the acceptance of LHCf
Massimo Bongi - RESMDD08 - 15 October 2008 - Florence
Beam
crossing
angle
LHCf single  geometrical acceptance
Mechanical manipulators allows to remotely move LHCf: some
runs with the detectors vertically shifted few cm will allow to
cover the whole kinematical range
Massimo Bongi - RESMDD08 - 15 October 2008 - Florence
LHCf : Monte Carlo discrimination
• 106 generated LHC
interactions
• ~ min exposure
@1029 cm-2s-1
luminosity
• already allows
discrimination
between various
models (5% energy
resolution included)
Massimo Bongi - RESMDD08 - 15 October 2008 - Florence
LHCf: model dependence of
neutron energy distribution
Neutron spectra at detector front
30% energy resolution included
Massimo Bongi - RESMDD08 - 15 October 2008 - Florence
LHCf energy resolution
2.5 x 2.5 cm2 tower
2.0 x 2.0 cm2 tower
Energy resolution ~ 3% at high energy,
even for the smallest tower
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Pion reconstruction
350 GeV Proton beam
Carbon target (3 cm)
in the slot used for beam monitor

9.15 m
(not in scale)

Arm#1
>107 proton on target (special setting from the SPS people)
Calorimeters
Shower Profile @ First SciFi Layer
40mm
X
Egamma=18GeV
Y
20mm
Egamma=46GeV
X
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Y
Pion mass reconstruction
 250 pion events triggered (in a quite big background)
Δm ~ 8 MeV
Δm/m ~ 6%
(MeV)
Massimo Bongi - RESMDD08 - 15 October 2008 - Florence
Arm#1 position resolution
200 GeV electrons
σX[mm]
Number of event
σX=172µm
x-pos[mm]
E[GeV]
Number of event
σY[mm]
σY=159µm
y-pos[mm]
E[GeV]
Massimo Bongi - RESMDD08 - 15 October 2008 - Florence
Arm#2 position resolution
200 GeV electrons
Position Resolution X Side
120
Data
Resolution (microns)
σX=40µm
σX[µm]
100
Simulation Spread Out
80
60
40
20
0
0
x-pos[mm]
50
100
E[GeV]
150
200
250
Energy (GeV)
Position Resolution Y Side
160
140
Data
Simulation Spread Out
Resolution (microns)
σY=64µm
σY[µm]
120
100
80
60
40
y-pos[mm]
20
0
Alignment has been taken
into account
E[GeV]
Massimo Bongi - RESMDD08 - 15 October 2008 - Florence
0
50
100
150
Energy (GeV)
200
250
Radiation damage studies
 Silicon detectors from ATLAS SCT (see next talk!)
 test of Scintillating fibers and scintillators
 Dose evaluation on the basis
of LHC reports on radiation
environment at IP1
 <10 Gy/day @ 1029 cm-2s-1
luminosity are expected
 some tens Gy during 1 week
operation lead to ~10% light
output decrease
 scintillators
will
be
monitored and decrease of
30 kGy
light output will be corrected
by laser calibration
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LHCf Arm#1 – Installation completed
Massimo Bongi - RESMDD08 - 15 October 2008 - Florence
LHCf Arm#2 – Installation completed
Massimo Bongi - RESMDD08 - 15 October 2008 - Florence
LHCf ready for data taking
The LHCf control
room in the ATLAS
area
Massimo Bongi - RESMDD08 - 15 October 2008 - Florence
Dummy event
Massimo Bongi - RESMDD08 - 15 October 2008 - Florence
LHCf ready for data taking
• On September 10 we observed some signals on Front Counters, with
Arm#1 and Arm#2 in garage position for safety reasons
That day the Atlas BPTX signal was still not available (no info on
the real bunches in the Atlas zone)
• On September 11 Atlas gave us the synchronized BPTX signals, and
we could take Front Counter data by using this signal (still in garage
position)
• We are measuring beam-gas interactions from beam2 on Arm#1 side
Massimo Bongi - RESMDD08 - 15 October 2008 - Florence
LHCf ready for data taking
Massimo Bongi - RESMDD08 - 15 October 2008 - Florence
Conclusions
 Detectors construction and installation
completed in 2008
 Preparation for running completed
 First beam gas events acquired
 We are ready for LHC data
Massimo Bongi - RESMDD08 - 15 October 2008 - Florence