FLUKA as a new high energy cosmic ray generator G. Battistoni 2, A. Margiotta 1, S. Muraro 2, M....

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 Telescope Workshop 2009, Athens

Outline

Main features of FLUKA Motivations Code structure Geometry setup First results Conclusions

A. Margiotta, Athens 2009 2


FLUKA - Interaction and Transport Monte Carlo code

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

FLUKA authors: A. Fasso1, A. Ferrari2, J. Ranft3, P.R. Sala4

1 SLAC Stanford, 2 CERN, 3 Siegen University, 4 INFN Milan http://www.fluka.org


Motivations 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 muon-related secondaries) for some topic sites: presently LNGS, ANTARES and Capo Passero sites


Code structure Geometry description Generation of the kinematics (i.e. the source particles) ↔ primary cosmic ray

composition model 2 hadronic interaction models can be used:

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) 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

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)

A. Margiotta, Athens 2009

Earth

Geometry for underground sites

Spherical mountain whose radius isdynamically changed using a detailedtopographical map

Atmosphere

Primary injection point

z020

22 dcR2RdR

R

d

R0

z


Geometry setup: LNGS halls

LNGS underground halls

External (rock)volume to propagateall particles down to100 MeV

muon-producedsecondaries


Some results from the simulation

For a given site (e.g. Hall C at LNGS), possibility to parameterize all particle components reaching the underground level

muons

photons

electrons

log10 Ekin (GeV)

even

ts/y

ear

Vertexes of particles entering the Hall C at LNGS



Geometry setup (underwater)

Underwater case (e.g. ANTARES/KM3NeT)Earth ≡ sphere of perfectly absorbing mediumsea ≡ spherical shell of wateratmosphere ≡ 100 concentric atmospheric shellsCan ≡ virtual cylindrical surface bounding the

active volume (instrumented volume + 2-3 abs )

M. Sioli, Blois 2008 12

Atmosphere

Earth

Sea Can

Geometry for underwater sites


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

Aknee

A2

Aknee

A1

EE,EKdEdN

EE,EKdEdN

A2

A1

EEcut

~2.7÷3Ecut~3000 TeV


Technical issues (biasing)–underwater case■ initialize minimum energy for primary cosmic rays:

lower bound evaluated according to muon survival probabilities 2* Ethr

recompute “on the fly” energy thresholds: 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 !!!


Some results from the simulation -1

Vertexes of particles entering a KM3 detector canat 3500 m under sea level

Sea bottom = 3500 m

Can radius = 1000 m height = 1000 m

primaries sampled on a circle with R= 2000 m perpendicular to theirdirection and centered in the origin of the can

muons propagated from the sea level to theirgeometrical intercept withthe detector surface


Some results from the simulation -2

multiplicity

Log (energy/TeV)

primary energy

multiplicity @ can

meters

muon decoherence


Conclusions 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:

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

Further information: send me an e-mail.

spare slides


(ordinary) meson decay: dN/d cos~ 1/ cos

Primary C.R. proton/nucleus: A,E,isotropic

hadronic interaction: multiparticle production (A,E), dN/dx(A,E) extensive air shower

short-lifetime meson production

and prompt decay (e.g. charmed mesons)

Isotropic ang. distr.

detection: N(A,E), dN/dr

transverse size of bundle

Pt(A,E)

(TeV) muon propagation in water : radiative processes and fluctuations

Multi-TeV muon transport

Primary p, He, ..., Fe nuclei with lab. energy from 1 TeV/nucleon up to >10000 TeV/nucleon

The physics of CR TeV muons

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

low E π,K

Special

High Energy

DPM

hadronization

Hadron-Nucleus Nucleus-Nucleus

E < 5 GeV

PEANUT

Sophisticated GINC

Preequilibrium

Coalescence

High Energy

Glauber-Gribov

multiple interactions

Coarser GINC

Coalescence

E< 0.1GeV/u

BME

Complete fusion+

peripheral

0.1< E< 5 GeV/u

rQMD-2.4

modified

new QMD

E> 5 GeV/u

DPMJET

DPM+

Glauber+

GINC

Evaporation/Fission/Fermi break-up

deexcitation

> 5 GeV Elab

DPM: soft physics based on (multi)Pomeron exchangeDPMJET: soft physics of DPM plus 2+2 processes from pQCD

Relevant forRelevant forHE C.R. physicsHE C.R. physics

22

MINOSMINOS Charge Ratio at the Surface = 1.374 ± 0.004 (stat.) (sys.)

Phys. Rev. D 76, 052003 (2007)

RFLUKA μ+/μ− = 1.333 ± 0.007•Agreement between Agreement between FLUKA simulation and FLUKA simulation and MINOS data within 3%MINOS data within 3%

•Discrepancy Discrepancy systematically remarkablesystematically remarkable

•No dependence on muon No dependence on muon momentum in the momentum in the atmosphere in the range atmosphere in the range consideredconsidered

L3L3 ++ COSMICCOSMIC((hep-ex/0408114).RFLUKA= 1.29 0.05Rexp=1.285 0.003(stat.) ± 0.019(sys.)

012.0010.0

FLUKA as a new high energy cosmic ray generator G. Battistoni 2, A. Margiotta 1, S. Muraro 2, M....

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