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

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

M. Sioli, Blois 2008 2

Outline

Motivations Main features of FLUKA Code structure The geometry setup

The underground caseThe underwater case

First results Conclusions


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)


Main features of FLUKA

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

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


(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-lifetimemeson 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 the rock: radiative processes andfluctuations

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 see hep-ph/0612075 and 0711.2044)

Hadron-HadronElastic,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


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)


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)

M. Sioli, Blois 2008 9Earth

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


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)


Atmosphere

Earth

Sea Can

Geometry for underwater sites


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 Ekin<800 GeV at mountain

entrance kill particles with Ekin<2 GeV inside mountain kill particle with Ekin<100 MeV inside rock shell


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 E<Emin have a probability < 10-5 to survive at hMIN


Minimum energy/nucleus(TeV) for each mass group,as the function of the angularwindow

Energy/nucleus (TeV) for each mass group, for angular window W6

Muon and 1ry thresholds


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


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 in the Hall C at LNGS


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 levelmuons have to be sampled on the surface of a box surrounding detector sensitive volumes

DIRECT comparison


FLUKA and HEMAS-DPM comparison

HEMAS

FLUKA

( MACRO-fit + DPMJET-II.4 )


Nor

mal

ized

d t

o th

e sa

me

livet

ime



HEMAS

FLUKA



Nor

mal

ized

d t

o th

e sa

me

livet

ime


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


spares


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):

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

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

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