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Background Simulations

17 February 2003. Computing Meeting. Background Simulations. Where are we? Background in the muon system LHC Machine background ( Radiation levels ). G.Corti, CERN/EP. Simulation of background in the Muon System.

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Background Simulations

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  1. 17 February 2003 Computing Meeting Background Simulations Where are we? Background in the muon system LHC Machine background ( Radiation levels ) G.Corti, CERN/EP

  2. Simulation of background in the Muon System • Neutron induced background is relevant in the muon system where hits multiplicity is relatively low. • Also when looking at radiation levels • High thresholds are normally applied in the muon shields. • 500 MeV • Dedicated SICBMC + GCalor simulation with low thresholds • GCALOR is a library interfaced with GEANT3 • used to simulate hadronic nuclear interactions instead of G-GHEISHA (G-FLUKA) • uses G-FLUKA for projectile energies > 10 GeV • CPU time intensive ( ~ 300 sec /event on a CERN machine) • CMT package: simgcal • library for GCalor v1.05 • sicbgcal application build in SICBMC package for special studies • need to override guphad, guhadr • HADR = 4 card • available for use in $LHCBHOME/group/background • will be released in the next 2 weeks G.Corti

  3. Simulation of background in the Muon System • Additional infrastructures like the cavern are added for these studies. • Cards: GEOM ‘CAVE’ 3 ‘FRWD’ 4 ‘BWRD’ 4 • Cave.cdf • Very low thresholds also in muon shields • 30 KeV for electrons and gammas, 1 MeV charged hadrons, 10-14 eV for neutrons • Very long time hits contributions ToF of hits in M2 G.Corti

  4. Results obtained are compared to standard simulation to produce parameterization of background hits to add in production Default added at end of SICBMC Various levels of background can be added Before digitization of muon chambers in BRUNEL New algorithm to read in parameterization from histograms New RAWH events recently produced by Rome group ( R.Santacesaria and A. Satta ) Analysis in progress New algorithm with new data expected to be available in ~ 1 month Histograms are standard simulation + parameterized background Points are from full simulation with SICB +GCalor Muon Background Studies with GCalor Total hits multiplicity in Muon Stations G.Corti

  5. CMS IP5 Dump BCS Sector 78 Ring 1 Sector 81 IP8 LHCb Injection Ring 2 LHC Machine background • Fraction of beam particles lost in the machine due to beam-gas and beam-beam interactions. • Products can reach the experiment • Proportional to to beam intensity ( i.e. Luminosity of IP1/5 ) • Particularly important for muon system and trigger • Beam losses calculated for both rings and products of beam-gas interaction transported to LHCb cavern • files of surviving particles for different b* for the 2 rings • STRUCT + MARS ATLAS IP1 G.Corti

  6. Evaluation of LHC background • Each file is given per unity of linear density of proton interaction with the gas nuclei [1 inelastic interaction x m-1 ] • muons, pions and kaons, protons, neutrons • Each particle has a weight • The z of the initial interaction and gas nuclei is provided • This allows to normalized to effective number of interactions per meter provided the density of the residual gases and the their cross section • A certain gas density and composition has been assumed to produce the files and has to be unfolded • 1996 numbers used • New calculations available last summer from Vacuum Groups for various running conditions: • Y1 beginning, Y1+70 days, Y2 beginning, Y2+10 days, Y3+90 days G.Corti

  7. LHC machine background evaluation • Obtain directly distributions and rates of particles per filled bunch in different running conditions for both beams for separate type of particles • Integrate with SICBMC to study effect on detectors and trigger of this background alone or “merged” with pp-collisions r distributions of muon halo per bunch Ring1 Year 2+10days G.Corti

  8. Implementation in SICBMC • Files used as they are for input • particle parameters correlations are taken into account • weights renormalized respect to a specific running condition at initialization • cdf file with running conditions (beam current, gas densities) • background associated with each filled bunch is generated • Poisson distribution of number of particles per beam crossing, corresponding to normalization ( n = Sum (weigth) ) • Pre-integration method (“envelope”), dividing input set in sub-sets, local integrations for each sub-sets • After selection of sub-set a second random choice inside sub-set and corresponding particle from source is taken • generate this background stand-alone • SIFL 6=1, EGEN = 99 • in simpgen package • New normalization and generation for both files (n1 + n2 bunches) under final test, expect to be released after LHCb week ( D.Dominici in Rome + G.Corti ) • Private version used last year by muon trigger • output in RAWH format G.Corti

  9. “Merge” LHC background with pp collisions • Combine LHC background and pp collisions before digitization • evaluate different background conditions • In Y2+10 days ~ 0.2 particles/filled bunch • similar to spill-over problem but: • Zebra complications when many files are read in BRUNEL • This will need to be done for GAUSS as well • Proposal: • Produce RAWH files with SICBMC • Convert straight away into a OORAWH (no digitization) • Read OORAWH with pp-collision file before digitization • Expect this to be available around the end of March • On longer time scale replace generator algorithm now in SICBMC with similar algorithm in GAUSS G.Corti

  10. Radiation levels • For radiation levels estimation dedicated simulation of LHCb detector and infrastructures with FLUKA. • its own geometry interface and material description • Stand-alone and completely independent. x (cm) Dose (Gy/year) z (cm) Radiation dose in LHCb for y = 0 G.Corti

  11. Long term plans • LHC background integration in GAUSS • Generator algorithm equivalent to what now in simpgen • Merging at digitization stage identical to what planned for Brunel • Low energy background in muon system • GCalor is strongly related to GEANT3 • Is there something equivalent in GEANT4? If not is it planned? • Investigation will have to start in next year • Radiation levels • Ideal would be to use only one geometry database • FLUGG = FLUka with Geant4 Geometry ? • extention of FLUKA that uses the GEANT4 geometry package in C++ for the geometry description and the FLUKA simulation of the physics processes in FORTRAN • Project to input/output interface to ROOT • Investigation is necessary G.Corti

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