Recent results on neutral particles spectra from the LHCf experiment Massimo Bongi - INFN (Florence, Italy) LHCf Collaboration 13th ICATPP Conference on Astroparticle, Particle, Space Physics and Detectors for Physics Applications Villa Olmo - Como, Oct 3 rd – 7 th , 2011
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Recent results on neutral particles spectra from the
LHCf experiment
Massimo Bongi - INFN (Florence, Italy)
LHCf Collaboration
13th ICATPP Conference onAstroparticle, Particle, Space Physics and Detectors for Physics
ApplicationsVilla Olmo - Como, Oct 3rd – 7th, 2011
Massimo Bongi – ICATPP – 3rd October 2011 – Como
High-energy cosmic rays
LHC
SPS
AUGER
Tevatron
E [eV]
Recent excellent observations (e.g. Auger, HiRes, TA) but the
origin and composition of HE CR is still unclear
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Massimo Bongi – ICATPP – 3rd October 2011 – Como
Development of atmospheric showers
LHC forward (LHCf) experiment
1019 eV proton
The dominant contribution to the shower development comes from particles emitted at low angles (forward region).
Experimental tests of hadron interaction models are necessary
LHC gives us the unique opportunity to study hadronic interactions at 1017eV
7 TeV + 7 TeV→ Elab ≈ 1 x 1017 eV
3.5 TeV + 3.5 TeV → Elab ≈ 3 x 1016 eV
450 GeV + 450 GeV → Elab ≈ 4 x 1014 eV
The depth of the maximum of the shower Xmax in the atmosphere depends on energy and type of the primary particle
Several Monte Carlo simulations (different hadronic interaction models) are used and they give different answers about composition
Solar-Terrestrial Environment Laboratory, Nagoya University, JapanH.Menjo Kobayashi-Maskawa Institute, Nagoya University, JapanK.Yoshida Shibaura Institute of Technology, Japan
K.Kasahara, T.Suzuki, S.Torii Waseda University, JapanY.Shimizu JAXA, Japan
T.Tamura Kanagawa University, Japan
M.Haguenauer Ecole Polytechnique, France
W.C.Turner LBNL, Berkeley, USA
O.Adriani, L.Bonechi, M.Bongi, R.D’Alessandro, M.Grandi, P.Papini, S.Ricciarini, G.Castellini INFN and Universita’ di Firenze, ItalyK.Noda, A.Tricomi INFN and Universita’ di Catania, Italy
J.Velasco, A.Faus IFIC, Centro Mixto CSIC-UVEG, Spain
Preliminary π0 spectra Mass range selection: +/- 10 MeV
around the measured peak
Acceptance depends on energy and
transverse momentum (lowest energy is
limited by maximum angle between
photons)
Comparison with MC is on-going
Extend the analysis
to events with two
photons in the same
towerm ≈ θ√(E1xE2)Eπ = E1+E2
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Massimo Bongi – ICATPP – 3rd October 2011 – Como
Summary and outlook Single photon analysis at 3.5 TeV + 3.5 TeV:
• first comparison of various hadronic interaction models with experimental data in a challenging phase space region
• very safe estimation of systematics• no model perfectly reproduces LHCf data, especially at high
energynew input data for model developersimplications for HE CR physics under study
Neutral pion analysis at 3.5 TeV + 3.5 TeV is in progress:• compare pion spectra with MC• include events with two gammas hitting the same tower• the same analysis can be extended to η and K0 particles
Other analysis: complete the analysis at 450 GeV + 450 GeV, neutrons, transverse momentum distributions, extend pseudo-rapidity range,…
We are upgrading the detectors to improve their radiation hardness (GSO scintillators):• we will come back on the LHC beam for the 7 TeV + 7 TeV runs• discussion is under way to come back for possible p-Pb runs in
2013
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Backup
Massimo Bongi – ICATPP – 3rd October 2011 – Como
AGASA SystematicsTotal ±18%
Hadr Model ~10% (Takeda et al., 2003)
Open Issues on UHECR spectrum
M NaganoNew Journal of Physics 11 (2009) 065012
Depth of the max of the shower Xmax in the atmosphere
AUGERHiRes
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Massimo Bongi – ICATPP – 3rd October 2011 – Como
Front counters• Thin scintillators with 8x8cm2 acceptance,
which have been installed in front of each main detector.
• To monitor beam condition. • For background rejection of
beam-residual gas collisions by coincidence analysis
Schematic view of Front counter
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Detector vertical position and acceptance Remotely changed by a manipulator( with accuracy of 50 mm)
Distance from neutral center Beam pipe aperture
Data taking modewith different positionto cover PT gap
N
L
G
All g from IP
Viewed from IP
Neutral flux center
N
L
7TeV collisions
Collisions with a crossing angle lower the neutral flux center thus enlarging Pt acceptance
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Massimo Bongi – ICATPP – 3rd October 2011 – Como
Expected results @ 14 TeV collisions
n0
Energy spectra and transverse momentum distribution of:
• photons (E > 100 GeV): E/E < 5%
• neutral pions (E > 500 GeV): E/E < 3%
• neutrons (E > few 100 GeV): E/E ~ 30%
in the pseudo-rapidity range > 8.4
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Massimo Bongi – ICATPP – 3rd October 2011 – Como
LHCf energy resolution
2.5 x 2.5 cm2 tower 2.0 x 2.0 cm2 tower
Energy resolution < 5% at high energy, even for the smallest tower
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Massimo Bongi – ICATPP – 3rd October 2011 – Como
Arm1 position resolutionN
um
ber
of
even
tN
um
ber
of
even
t
x-pos[mm]
y-pos[mm]
200 GeV electrons
E[GeV]
E[GeV]
σX=172µm
σY=159µmσ X
[mm
]σ Y
[mm
]
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Massimo Bongi – ICATPP – 3rd October 2011 – Como
Arm2 position resolutionPosition Resolution X Side
0
20
40
60
80
100
120
0 50 100 150 200 250
Energy (GeV)
Re
so
luti
on
(m
icro
ns
)
Data
Simulation Spread Out
Position Resolution Y Side
0
20
40
60
80
100
120
140
160
0 50 100 150 200 250
Energy (GeV)
Re
so
luti
on
(m
icro
ns
)
Data
Simulation Spread Out
x-pos[mm]
y-pos[mm]
Alignment has been taken into account
200 GeV electrons
E[GeV]
E[GeV]
σX=40µm
σY=64µmσ X
[µm
]σ Y
[µm
]
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Massimo Bongi – ICATPP – 3rd October 2011 – Como
Estimation of pile-up
!)(
N
eNP
N
• When the circulated bunch is 1x1, the probability of N collisions per crossing is:
• The ratio of the pile-up event is:
• The maximum luminosity per bunch during runs used for the analysis is
2.3x1028cm-2s-1
• So the probability of pile-up is estimated to be 7.2%, with σ=71.5mb and
frev = 11.2 kHz
• Taking into account our calorimeter acceptance for an inelastic collision
(~0.03) only 0.2% of events have multi-hit due to pile-up
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Massimo Bongi – ICATPP – 3rd October 2011 – Como
Luminosity estimation• Luminosity for the analysis is calculated from Front
Counter rates:
•The conversion factor CF is estimated from luminosity measured during Van der Meer scan
VDM scan
Beam sizes sx and sy measured directly by LHCf
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Massimo Bongi – ICATPP – 3rd October 2011 – Como
p0 mass vs p0 energy
Arm2 data
No strong energy dependence of reconstructed
mass
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Massimo Bongi – ICATPP – 3rd October 2011 – Como
2g invariant mass spectrum @ 7 TeV
Arm2 detector, all runs with zero crossing angleTrue η mass: 547.9 MeVMC reconstructed η mass peak: 548.5 ± 1.0 MeVData reconstructed η mass peak: 562.2 ± 1.8 MeV (2.6% shift)
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Massimo Bongi – ICATPP – 3rd October 2011 – Como
Effect of mass shift
Energy rescaling NOT applied but included in energy error