Transcript Document

FLUKA as a new high
energy cosmic ray
generator
G. Battistoni2, A. Margiotta1, S. Muraro2, M. Sioli1
University and INFN of 1) Bologna and 2) Milano
for the FLUKA Collaboration
Very Large Volume n Telescope Workshop 2009, Athens
Outline
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Main features of FLUKA
Motivations
Code structure
Geometry setup
First results
Conclusions
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FLUKA - Interaction and Transport Monte Carlo code
FLUKA authors: A. Fasso1, A. Ferrari2, J. Ranft3, P.R. Sala4
1
SLAC Stanford, 2 CERN, 3 Siegen University, 4 INFN Milan
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http://www.fluka.org
FLUKA is a general purpose tool for calculations of particle transport and
interactions with matter, covering an extended range of applications
(Shielding, Radiobiology, High energy physics, Cosmic Ray physics,
Nuclear and reactor physics).
Built and maintained with the aim of including the best possible physical
models in terms of completeness and precision.
Continuously benchmarked with a wide set of experimental data from well
controlled accelerator experiments.
More than 2000 users all over the world
Physics models (e.g. hadronic interaction models) built according to a
theoretical microscopic point of view (no parameterizations) => High
predictivity also in regions where experimental data are not available
Cosmic Ray physics with FLUKA “triggered” by:
 HEP physics (e.g. atmospheric neutrino flux calculations)
 radioprotection in space
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Motivations
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extension of the existing FLUKA cosmic-ray library
to high energy region (primaries at the knee of the
spectrum)  use in underground and underwater sites
use of a unique framework with high quality
physics models (FLUKA) for the whole simulation,
from primary interaction in the upper atmosphere to
the detector level (and through the detector itself, in
principle)
creation of a prediction data set (muons and muonrelated secondaries) for some topic sites: presently
LNGS, ANTARES and Capo Passero sites
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Code structure
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Geometry description
Generation of the kinematics (i.e. the source particles) ↔
primary cosmic ray composition model
2 hadronic interaction models can be used:
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DPMJET-II.53
FLUKA
Output file on an event by event basis – interface between
standard and user output (presently ASCII “ANTARES-like”
and root output)
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information on primary cosmic ray generating the shower
for each particle reaching the detector level, stores all the relevant
parameters (particle ID, 3-momenta, vertex coordinates, momentum in
atmosphere, information on the parent mesons etc)
N.B. With FLUKA, shower generation, transport in the sea/rock, and
particle folding in the detector is performed inside the same framework
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Geometry setup (e.g. LNGS site)
 100 atmospheric shells
 1 spherical body for the
mountain, whose radius is
dynamically changed, according to primary direction and to
the Gran Sasso mountain map (direction  rock depth)
 1 rock box surrounding the experimental underground
halls, where muon-induced secondary are activated (e.m.
and hadron showers from photo-nuclear interactions)
 Underground halls: one box + one semi-cylinder
 Possibility to include simultaneously more than one
experimental Hall to study large transverse momentum
secondaries with detector coincidences)
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Geometry for underground sites
z
Spherical mountain whose radius is
dynamically changed using a detailed
topographical map
Primary injection point
d
R0
R 2  d2  R 02  2R 0dcz
R
Earth
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Geometry setup: LNGS halls
m
External (rock)
volume to propagate
all particles down to
100 MeV
muon-produced
secondaries
LNGS underground halls
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Some results from the simulation
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Vertexes of particles
entering the Hall C at
LNGS
For a given site (e.g.
Hall C at LNGS),
possibility to
parameterize all particle
components reaching
the underground level
events/year
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photons
electrons muons
log10 Ekin (GeV)
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Geometry setup (underwater)
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Underwater case (e.g. ANTARES/KM3NeT)
 Earth ≡ sphere of perfectly absorbing medium
 sea ≡ spherical shell of water
 atmosphere ≡ 100 concentric atmospheric shells
 Can ≡ virtual cylindrical surface bounding the
active volume (instrumented volume + 2-3 labs )
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Geometry for underwater sites
m
Can
Earth
M. Sioli, Blois 2008
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Primary sampling
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Primary energy spectrum has the form:
dN
A   1A
A
 K 1 E , E  Eknee
dE
dN
A   2A
A
 K 2 E , E  Eknee
dE
~2.7÷3
Ecut~3000 TeV
Ecut
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E
Possibility to choose among different spectra (now MACROfit is implemented)
Sampling done re-adapting some HEMAS routines
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Technical issues (biasing)–underwater case
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initialize minimum energy for primary cosmic rays:
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recompute “on the fly” energy thresholds:
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lower bound evaluated according to muon survival probabilities  2*
Ethrm
muon survival probabilities for various depths in sea water and various
muon energies at surface, evaluated with MUSIC (V. Kudryatsev)
muon energy at sea level  survival probability < 10-5
function obtained with a fit  multiplied by 0.9
underground case : thresholds are evaluated according
to the rock map
kill in atmosphere all particles with energy lower than
this threshold.
only muons with E> 20/100 GeV at the can are stored.
CPU time request optimized : FULL MC !!!
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Some results from the simulation -1
Sea bottom = 3500 m
Can radius = 1000 m
height = 1000 m
primaries sampled on
a circle with R= 2000 m
perpendicular to their
direction and centered in the
origin of the can
Vertexes of particles entering a KM3 detector can
at 3500 m under sea level
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muons propagated from
the sea level to their
geometrical intercept with
the detector surface
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Some results from the simulation -2
multiplicity @ can
muon decoherence
multiplicity
meters
primary energy
Log (energy/TeV)
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Conclusions
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FLUKA can be used as a new high energy cosmic ray generator for
underground and underwater physics.
Package developed using LNGS and neutrino telescope sites as examples.
It cannot substitute MUPAGE for fast simulation of atmospheric muon
background.
Unique framework  significant simplification of the FULL MC chain
Next steps:
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Introduce other primary cosmic ray composition models
 Extensive studies with FLUKA hadronic model in progress: very encouraging
results!
 Some space for code optimization.
 Sea level sampling
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Further information: send me an e-mail.
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spare slides
The physics of CR TeV muons
Primary C.R. proton/nucleus: A,E,isotropic
hadronic interaction: multiparticle production s(A,E), dN/dx(A,E)
 extensive air shower
Primary p, He, ..., Fe nuclei with lab. energy from 1
TeV/nucleon up to >10000 TeV/nucleon
K
(ordinary) meson decay: dNm/d cosq ~ 1/ cosq
p
short-lifetime meson production
and prompt decay (e.g. charmed mesons)
Isotropic ang. distr.
m
m
transverse size of bundle
 Pt(A,E)
m
(TeV) muon propagation
in water : radiative processes and
fluctuations
Multi-TeV muon transport
detection: Nm(A,E), dNm/dr
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The FLUKA hadronic interaction models
(for a detailed study of their validity for CR studies :hep-ph/0612075 and 0711.2044)
Hadron-Hadron
Elastic,exchange
Phase shifts
data, eikonal
P<3-5GeV/c
Resonance prod
and decay
Hadron-Nucleus
E < 5 GeV
PEANUT
Sophisticated GINC
Preequilibrium
Coalescence
High Energy
Glauber-Gribov
multiple interaction
s
Coarser GINC
Coalescence
> 5 GeV Elab
low E π,K
Special
High Energy
DPM
hadronization
Nucleus-Nucleus
E< 0.1GeV/u
BME
Complete
fusion+
peripheral
0.1< E< 5
GeV/u
rQMD-2.4
modified
new QMD
Evaporation/Fission/Fermi break-up
 deexcitation
E> 5 GeV/u
DPMJET
DPM+
Glauber+
GINC
Relevant for
HE C.R. physics
DPM: soft physics based on (multi)Pomeron exchange
DPMJET: soft physics of DPM plus 2+2 processes from pQCD
Phys. Rev. D 76, 052003 (2007)
MINOS
0.012
Charge Ratio at the Surface = 1.374 ± 0.004 (stat.) 0.010 (sys.)
•Agreement between
FLUKA simulation and
MINOS data within 3%
RFLUKA μ+/μ− = 1.333 ± 0.007
•Discrepancy
systematically remarkable
•No dependence on muon
momentum in the
atmosphere in the range
considered
L3 + COSMIC
(hep-ex/0408114).
RFLUKA= 1.29  0.05
Rexp=
1.285  0.003(stat.) ± 0.019(sys.)
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