Transcript Document

FLUKA as a new high
energy cosmic ray
generator
G. Battistoni, A. Margiotta, S. Muraro, M. Sioli
(University and INFN of Bologna and Milano)
for the FLUKA Collaboration
Blois 2008, Challenges in Particle Astrophysics
Outline
Motivations
 Main features of FLUKA
 Code structure
 The geometry setup
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 The
underground case
 The underwater case
First results
 Conclusions
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Motivations
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Extend the existing FLUKA cosmic-ray library to include
the TeV region (primaries at the knee of the spectrum),
aimed to underground and underwater sites
Different approach with respect to past and present
cosmic ray generators: use of a unique framework
(FLUKA) for the whole simulation. From 1ry interaction in
the upper atmosphere up to the detector level (and the
detector itself, in principle)
Provide a prediction data set (muons and muon-related
secondaries) for some topic sites: presently for LNGS
and ANTARES sites
Cross check with other dedicated simulation packages
(HEMAS, CORSIKA, Cosmos)
Cross check with past experimental data (e.g. MACRO)
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Main features of FLUKA
FLUKA authors: A. Fasso1, A. Ferrari2, J. Ranft3, P.R. Sala4
1
SLAC Stanford, 2 CERN, 3 Siegen University, 4 INFN Milan
Official web site: www.fluka.org
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FLUKA is a general purpose Monte Carlo code for the interaction
and transport of particles in matter in a wide range of energies in
user-defined geometries
Applications span from shielding design, space physics, calorimetry,
dosimetry, medical physics, detector design, particle physics etc.
The code is maintained and developed under a CERN-INFN
agreement
More than 1000 users all over the world
Physics models (e.g. hadronic interaction models) are built
according to a theoretical microscopic point of view (no
parameterizations)  few free parameters, high predictivity but low
flexibility
Cosmic Ray physics with FLUKA “triggered” by:
 HEP physics (e.g. atmospheric neutrino flux calculations)
 radioprotection in space
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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
short-lifetime
meson production
and prompt decay
(e.g. charmed mesons)
Isotropic ang. distr.
(ordinary) meson decay: dNm/d cosq ~ 1/ cosq
p
m
m
transverse size of bundle
 Pt(A,E)
m
(TeV) muon propagation
in the rock: 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 see 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 interactions
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
Code structure
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Geometry description
Generation of the kinematics (i.e. the source
particles) ↔ 1ry cosmic ray composition model
Output file on an event by event basis (root tree
file):
 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
(otherwise different tools have to be patched together)
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Geometry setup (e.g. LNGS site)
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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 2ry 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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Geometry setup (underwater)
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Underwater case (e.g. ANTARES)
 100 atmospheric shells
 Simpler geometrical description (see ≡ concentrical
spherical shell of water)
 Can ≡ virtual cylindrical surface which set the
boundaries for the active volume (instrumented with
PM-equipped lines)
 Eventually include also here an “active layer” (for
secondary production and following)
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Geometry for underwater sites
m
Can
Earth
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Technical issues (biasing)
 initialize
energy band boundaries for 1ry
cosmic rays:
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lower bound is computed according to muon
survival probabilities
 recompute
“on the fly” energy thresholds:
kill particles with Ekin<800 GeV at mountain
entrance
 kill particles with Ekin<2 GeV inside mountain
 kill particle with Ekin<100 MeV inside rock shell
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Muon and 1ry thresholds
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In order to bias the deeply falling
spectrum, production is divided in 5
energy bins and 6 angular windows
Muons with E<Emmin have a probability < 10-5 to survive at hMIN
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Muon and 1ry thresholds
Minimum energy/nucleus
(TeV) for each mass group,
as the function of the angular
window
Energy/nucleus (TeV) for each mass group, for angular window W6
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Primary sampling
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Primary energy spectrum has the form:
~2.7÷3
A
dN
A
Ecut~3000 TeV
 K 1A E  1 , E  Eknee
dE
dN
A   2A
A
 K 2 E , E  Eknee
dE
Ecut
E
Possibility to choose among different spectra
(now MACRO-fit is implemented)
Sampling done re-adapting some HEMAS
routines
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Some results from the simulation
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For a given site (e.g.
Hall C at LNGS),
possibility to
parameterize all
particle components
reaching the
underground level
Vertexes of particles
entering in the Hall C
at LNGS
events/year
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photons
electrons muons
log10 Ekin (GeV)
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FLUKA and HEMAS-DPM comparison
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We cross-checked FLUKA with HEMAS-DPM code:
 HEMAS was a shower code extensively used in the MACRO
collaboration
 At the beginning (~1990), HEMAS was the name of both the shower
propagation code and of the embedded hadronic interaction model
(based on UA1 parameterizations) this version was used to
produce the so-called MACRO-fit 1ry composition model
 Later, HEMAS native interaction model was superseeded with
DPMJET-II.4 (HEMAS-DPM, Battistoni 1997)
 Muon transport in rock treated with another dedicated package
(PROPMU, Lipari-Stanev 1991)
HEMAS output (only muons) is on an infinite area at underground
levelmuons have to be sampled on the surface of a box surrounding
detector sensitive volumes
DIRECT comparison
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Normalized d to the same livetime
FLUKA and HEMAS-DPM comparison
HEMAS
( MACRO-fit + DPMJET-II.4 )
FLUKA
( MACRO-fit + DPMJET-II.53 )
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Normalized d to the same livetime
FLUKA and HEMAS-DPM comparison
HEMAS
( MACRO-fit + DPMJET-II.4 )
FLUKA
( MACRO-fit + DPMJET-II.53 )
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Normalized d to the same livetime
FLUKA and HEMAS-DPM comparison
HEMAS
( MACRO-fit + DPMJET-II.4 )
FLUKA
( MACRO-fit + DPMJET-II.53 )
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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
The package has been developed using LNGS and
ANTARES sites as examples; however, it can be easily
extended to other sites, provided the map of the rock
overburden or the depth of underwater sites
First comparisons with other dedicated MC codes
(HEMAS)
Next steps:
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Introduce other 1ry cosmic ray composition models
Comparisons with experimental data, e.g.:
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MACRO unfolded multiplicity distribution
MACRO unfolded decoherence distribution
Muon induced neutron flux at LNGS
Muon charge ratio with OPERA/MINOS spectrometers
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spares
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Rock map overburden @ LNGS
 A map
is an ascii file with three colums: zenith,
azimuth and the corresponding rock depth (in m)
 We have a topographical map from the Italian IGM
(up to 94 deg):
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Distances are related to the central part of Hall B (including
some badly known bins in the map)
Rock density from core sample campaign (2001)
 Starting from these data, it’s possible to reproduce
the map in every other place (Hall A, Hall C etc.) 
interpolation of scattered data
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