1. Monte Carlo Simulation Tools for an undersea Neutrino Telescope A.Margiotta 30 – Jan– 2013 KM3NeT meeting - Marseille

2. Most KM3NeT software is taken from ANTARES. Short summary of what we have now and what we can do with it. No details on the codes. Do we need anything else? In the following slides some personal comments in red and italics

3. “Typical” MC simulation chain event generators Cherenkov light emission and propagation response of the PMT and digitization atmospheric muons neutrinos Environmental parameters Detector geometry Environmental parameters Detector geometry background (electronic noise, light from environment) acq conditions background (electronic noise, light from environment) acq conditions Physics models “diverse” physics

4. physics generators Atmospheric muons neutrinos CORSIKA MUPAGE Developed in Bologna Parametric formulae Not flexible Fast simulation Fundamental role in KM3NeT studies Full simulation Huge CPU time Full user control It is worth making an effort to create a large “database” of muon showers at sea level for a KM3 detector  ANTARES RBR Hadronic interaction model GOOD CHOICE ! Recent results from LHC validate QGSJET in the energy region of interest for -TELESCOPES Primary composition model QGSJET-II.03 Horandel NSU (Bugaev et al.) Other user models can be easily defined Other user models can be easily defined MUSIC muon propagator compared to experimental results and to other codes MMC) Important step  it repeats the same operation thousand times. a small systematic error can diverge

5. GENIE GENHEN physics generators Atmospheric muons Neutrinos 3 ν NC & CC Neutrinos 3 ν NC & CC MUSIC + GEANT3 μ & particles propagation MUSIC + GEANT3 μ & particles propagation Some bugs corrected. Some new features introduced: original release guaranteed up to 10 8 GeV  recently extended to 10 10 GeV (for   only)  extended sources considered GENHEN : fast simulation reliable between 5 GeV and 10 8-9 GeV almost orphan code GENIE: used by IC people for PINGU simulation interesting collaboration between ANTARES and IceCube slower than GENHEN does not cover the full energy (< 300 GeV): next vrs  1 PeV fully maintained and updated

6. Bartol Flux ν μ + anti-ν μ (Kamioka Solar Minimum), 1 year GenHen: 8.27e+06 gSeaGen: 7.30e+06 Ratio: 1.13 13% difference due to the specific Bartol model used in the 2 packages and to the way interactions are treated inside the code. by C. Distefano

7. What do we miss ? Atmospheric muons: can we make MUPAGE more flexible? Can we introduce additional parameterizations to account for the relative chemical composition of primary CRs? Neutrinos: do we need EHE neutrino simulation ? How far should we go? >10 10 GeV ? Some contacts with the IceCube group working on JULIeT. What do we have now? several alternatives for quick (parameterized) and full simulation of atmospheric muons and for neutrinos  It helps debugging and comparison. What can we do with it? more or less, all we need…..

8. Cherenkov light emission and propagation photon tables KM3 Cherenkov light from muons (track and em showers individual photons tracked to create “photon fields” around the emission points convolution with OMs to fill hit probability tables water models and OMs description quick simulation different approaches are possible individual photon propagation clsim each photon is tracked individually water & ice models OMs description huge CPU time request - GPU cards necessary Do we really need for mass production? Sea water is a homogeneus medium (not true for SouthPole ice) ESSENTIAL FOR TEST PURPOSES Dramatic improvements during last year: corrected several bugs/incoherences much better description of light scattering One Particle Approximation for shower-like events (NC & e )  GEASIM not required  much faster simulation + light scattering OPA NOT good for ORCA GEASIM (Geant3) Shower simulation (up to 100 GeV for  CC events) No light scattering preliminary fit quality parameter parameterization/ana lytical approach Sirene (under test) Sirene (under test)

9. One Particle Approximation Replace all non-muonic products with a single electron of ‘equivalent’ energy Why? Allow km3mc to handle shower events Allow treatment of scattered photons for showers Speed up simulations! Used in shower-like events (NC and e events) and for hadronic showers in CC  events. It will used in the next ANTARES Monte Carlo production.

10. Some technical details on OPA (C. James)

11. What do we miss ? Common repository and common releases are desirable and already under construction. What do we have now? several alternatives for quick and full simulation of light production and propagation. possibility of comparing different approaches  level of approximation/detail can be fixed. What can we do with it? more or less, all we need….. KM3Net MC software has been taken from the ANTARES software. Some modifications required to adapt the original code to the new situation  geometry, optical properties… Some bugs found and corrected during this revision work Some new features added (extended source simulation, …)

12. response of the PMT + trigger sim background (electronic noise, light from environment) acq conditions background (electronic noise, light from environment) acq conditions TriggerEfficiency does the job: adds the optical background applies trigger algorithms ANTARES Undersea neutrino telescope: variable BG dominated by environment In ANTARES  Run-by-Run simulation follow time evolution of the data acquisition ONE DATA RUN  ONE MC RUN ALL RUNS PROCESSED – NO QUALITY SELECTION a fraction of each run LT simulated for MUPAGE and CORSIKA (20-30%) a fixed number of neutrinos simulated creation of a muon showers repository for CORSIKA events KM3NeT Old ANTARES code (modk40) to simulate 40 K background in a time window to assign the correct hit time and hit charge according to experimental distributions. to apply some trigger algorithms.

13. How RBR works LOOP OVER MC EVENTS: random position selected along the data run extraction of a group of timeslices information concerning nb of hits, triggers, active OMs…. read from timeslices and used for optical background definition and data filtering for a group of events (1 timeslice  1 MC event) charge for each hit extracted from the measured charge distribution BG hits added to MC events (only active OMs in that timeslice are considered) info on calibrations, HV thresholds, setup of the run, etc read from the DB. data filtering according to the active triggers in the run

14. Disadvantages: large CPU time requirement, but affordable. Advantages: “puntual” representation of the BG (baseline and burst fraction) easy checking of the time evolution of data taking easy reprocessing : updated codes, new values of parameters,etc… good for all analyses /run selection etc. easy to use: events reconstructed with different strategies directly available moderate storage requirements: sea level showers produced with CORSIKA stored + all final files with reconstructed events  MUPAGE + neutrinos 2007-2012  ≈ 1.4 TB

15. Present situation: MUPAGE and all neutrino flavors and interactions (no tau neutrinos) simulated. Bottle necks: KM3 is a slow code if compared to MUPAGE or GENHEN. Keep in mind it is around 150 times faster than clsim – In our RBR, a typical run lasting around 3 hours takes about 17 real hours in Lyon batch farm, for the simulation of MUPAGE + (NC+CC) nu_mu and nu_e. – It takes about 3 real days to simulate CORSIKA showers to sea level. Ready to start a new RBR simulation (V3) with updated input parameters.

16. What do we miss ? ANTARES: continuos improvement of MC ingredients KM3NeT : data  checking the reliability of MC simulations. What do we have now? well established procedure for Run-by-Run simulation in ANTARES more generic procedure for BG / electronics/ trigger simulation in KM3neT What can we do with it? follow time evolution of data acquisition in ANTARES estimate the detector response in KM3NeT

17. Conclusions Monte Carlo simulations in ANTARES and in KM3NeT rely on a complete set of efficient, reliable and well performing software packages. Hopefully, KM3NeT will exploit the experience of the ANTARES experiment and evolve quickly (much more quickly than in ANTARES, which is a pioneer, by construction…), towards a stable situation, with no need to explore several solutions, as done in ANTARES.

18. Diiferent hadronic models used in IC and ANTARES All particle spectrum  AT LEAST 2 ingredients primary cosmic ray composition hadronic interaction description An opportune combination of composition and hadronic interaction models can represent experimental data:

19. ANTARES 5 mass groups (p, He, C,Mg,Fe) E -2 spectrum for generation (1<E<10 5 TeV/nucleon) only muons @ sea level (E>500 GeV/1TeV) primary composition weight applied by the user all-purpose MC (for the time being….) Horandel (polygonato) spectrum as default  too low muon flux alternative models often used (Nikolsky et al, private communications…) muons propagated to the detector level with MUSIC program 3D code (scattering included), all main energy loss processes simulated MUPAGE NSU model (Bugaev)

20. GENHEN in ANTARES ν e ν  CC + all NC only vertices inside the “can” volume all particles processed for light production ν μ CC muon energy range accounted for only muons are propagated to the “can” and considered for light production LEPTO for nu interaction CTEQ6 structure function PYTHIA/JETSET for hadronization DIS+RES+QE processes PRESENT MC: E -1.4 spectrum + reweighting 5 GeV< E<10 8 GeV absorption probability accounted for in the weight relevant to low energy