FLUKA as a new high energy cosmic ray generator

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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 CollaborationBlois 2008,
  Challenges in Particle Astrophysics

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Outline

• Motivations
• Main features of FLUKA
• Code structure
• The geometry setup
• The underground case
• The underwater case
• First results
• Conclusions

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Motivations

• 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

• 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
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 gt10000 TeV/nucleon
K
(ordinary) meson decay dNm/d cosq 1/ cosq
p
m
short-lifetime meson production and prompt
decay (e.g. charmed mesons) Isotropic ang. distr.
transverse size of bundle ? Pt(A,E)
m
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 Hadron-Hadron Hadron-Hadron Hadron-Hadron Hadron-Hadron Hadron-Hadron Hadron-Hadron Hadron-Hadron
Elastic,exchange Phase shifts data, eikonal Elastic,exchange Phase shifts data, eikonal Plt3-5GeV/c Resonance prod and decay Plt3-5GeV/c Resonance prod and decay low E p,K Special low E p,K Special High Energy DPM hadronization High Energy DPM hadronization
Hadron-Nucleus Hadron-Nucleus Hadron-Nucleus Nucleus-Nucleus Nucleus-Nucleus Nucleus-Nucleus Nucleus-Nucleus Nucleus-Nucleus
E lt 5 GeV PEANUT Sophisticated GINC Preequilibrium Coalescence High Energy Glauber-Gribov multiple interactions Coarser GINC Coalescence High Energy Glauber-Gribov multiple interactions Coarser GINC Coalescence Elt 0.1GeV/u BME Complete fusion peripheral Elt 0.1GeV/u BME Complete fusion peripheral 0.1lt Elt 5 GeV/u rQMD-2.4 modified new QMD 0.1lt Elt 5 GeV/u rQMD-2.4 modified new QMD Egt 5 GeV/u DPMJET DPM Glauber GINC
Evaporation/Fission/Fermi break-up ? deexcitation Evaporation/Fission/Fermi break-up ? deexcitation Evaporation/Fission/Fermi break-up ? deexcitation Evaporation/Fission/Fermi break-up ? deexcitation Evaporation/Fission/Fermi break-up ? deexcitation Evaporation/Fission/Fermi break-up ? deexcitation Evaporation/Fission/Fermi break-up ? deexcitation Evaporation/Fission/Fermi break-up ? deexcitation
gt 5 GeV Elab
DPM soft physics based on (multi)Pomeron
exchange DPMJET soft physics of DPM plus 22
processes from pQCD
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Code structure

• 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)

• 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
Atmosphere
R0
R
Earth
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Geometry setup LNGS halls
External (rock) volume to propagate all particles
down to 100 MeV
m
muon-produced secondaries
LNGS underground halls
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Geometry setup (underwater)

• 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
Atmosphere
m
Sea
Can
Earth
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Technical issues (biasing)

• initialize energy band boundaries for 1ry cosmic
  rays
• lower bound is computed according to muon
  survival probabilities
• recompute on the fly energy thresholds
• kill particles with Ekinlt800 GeV at mountain
  entrance
• kill particles with Ekinlt2 GeV inside mountain
• kill particle with Ekinlt100 MeV inside rock shell

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Muon and 1ry thresholds

• In order to bias the deeply falling spectrum,
  production is divided in 5 energy bins and 6
  angular windows

Muons with EltEmmin have a probability lt 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

• Primary energy spectrum has the form
• Possibility to choose among different spectra
  (now MACRO-fit is implemented)
• Sampling done re-adapting some HEMAS routines

g2.73 Ecut3000 TeV
Ecut
E
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Some results from the simulation

• Vertexes of particles entering in 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

photons
events/year
electrons
muons
log10 Ekin (GeV)
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FLUKA and HEMAS-DPM comparison

• 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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FLUKA and HEMAS-DPM comparison
Normalized d to the same livetime
HEMAS
( MACRO-fit DPMJET-II.4 )
FLUKA
( MACRO-fit DPMJET-II.53 )
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FLUKA and HEMAS-DPM comparison
Normalized d to the same livetime
HEMAS
( MACRO-fit DPMJET-II.4 )
FLUKA
( MACRO-fit DPMJET-II.53 )
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FLUKA and HEMAS-DPM comparison
Normalized d to the same livetime
HEMAS
( MACRO-fit DPMJET-II.4 )
FLUKA
( MACRO-fit DPMJET-II.53 )
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Conclusions

• 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
• Introduce other 1ry cosmic ray composition models
• Comparisons with experimental data, e.g.
• 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 _at_ 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)
• 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, its possible to
  reproduce the map in every other place (Hall A,
  Hall C etc.) ? interpolation of scattered data