The LHCb Muon System and LAPE Participation Burkhard Schmidt CERN - EP/LHB Presented at the CNPq Workshop Rio de Janeiro, 12 January 1999

12/1/1999B. Schmidt / CERN Outline Introduction Muon identification in particle physics experiments The LHCb Muon System - Overview - Muon detector technologies and prototype studies - Frontend-electronics - Level 0 muon trigger Muon System Schedule LAPE Participation Conclusion

12/1/1999B. Schmidt / CERN Introduction Lepton identification: Many discoveries in particle physics are based on lepton (e,  identification: J/  Neutral Currents, W ± and Z 0, top etc. Lepton identification in LHCb is important for the B d J/  s and B d J/  (ee)  s decay channels electrons and muons give complementary signatures due to huge differences in radiative losses: - electrons are identified by calorimetry and E/p matching - muons are identified by their penetration power The complementarity of e and  signatures is a powerful tool in particle physics

12/1/1999B. Schmidt / CERN The LHCb Detector

12/1/1999B. Schmidt / CERN The LHCb Detector

12/1/1999B. Schmidt / CERN Introduction Hadron punch-through: The probability for a hadron to traverse material of thickness L and nuclear interaction length without interacting is e -L/. Punch-through indicates the debris exiting an absorber and causes wrong identification of a hadron as a prompt muon. The length of a hadron absorber must be sufficient to reduce the punch-through trigger rate well below the prompt  rate. Minimum absorber length ~ 10 Total thickness of LHCb hadron absorber (muon shield) : ~ 23

12/1/1999B. Schmidt / CERN Overview Background sources in the LHC environment: primary background (correlated in time with the p-p interaction): - hadron punch-through including muons generated in the hadron shower -  K  X decays, predominantly with P T < 10 GeV radiation background: neutron and photon “gas” (MeV energies from radiative n-capture) generated by hadrons interacting in the absorber. Its impact depends on the efficiency of the chamber material for photon conversions. machine background: energetic muons produced in beam-gas interactions and in machine elements upstream of the experimental areas.

12/1/1999B. Schmidt / CERN Overview Particle fluxes in the muon stations The highest rates are expected in M1 (not protected by the shield) and in the inner part of Stations 2-5. In the outer part of station 2-5 a technology with moderate rate capability can be used.

12/1/1999B. Schmidt / CERN LHCb Muon System The Muon System must provide: Muon identification Reliable beam-crossing identification (good timing resolution) Reasonable momentum resolution for a robust P T -selective trigger (L0 muon trigger) Good performance for the duration of LHC in a high rate environment

12/1/1999B. Schmidt / CERN Muon Detector Layout Chamber pad structure: Muon stations are devided in 4 regions with different pad size Pad dimension scales with station number Projectivity to interaction point Required precision in the bending plane (x) leads to x/y aspect ratio of 1/2 in stations M1 and M2. “Physical” pads in outer region and in the various planes per station are grouped together to “logical” pads. total number of physical pads: ~240 k total number of logical pads: ~45k

12/1/1999B. Schmidt / CERN Muon System Technologies Cathode Pad Chambers (CPC) : Wire Chamber operated in proportional mode with cathode pads (strips) providing the spatial resolution. wire-spacing s determines time resolution at present: s = 2mm Characterized by very high rate capability and moderate time resolution 30% CO 2, 60% Ar and 10% CF 4 is prefered gas mixture CPC have good aging properties: 4C/cm equiv. to 50kHz/cm 2 /s for 10years

12/1/1999B. Schmidt / CERN Muon System Technologies Status of CPC R&D: A first prototype with pads of different sizes has been constructed together with its frontend-electronics at PNPI and tested using the CERN-PS beam. good signal/noise separations have been obtained time resolutions are better then expected

12/1/1999B. Schmidt / CERN Muon System Technologies Resistive Plate chambers (RPC) : Type of parallel plate chamber (therefore simple construction) with plates of a bulk resistivity of  ~  cm Gas mixture normally used: C 2 F 4 H 2 + few % isobutane + 1% SF 6 RPCs provide excellent time resolution and a moderate rate capability.

12/1/1999B. Schmidt / CERN Muon System Technologies Multigap RPCs (MRPC) : Improve timing properties of RPC further and reduce streamer formation

12/1/1999B. Schmidt / CERN Muon System Technologies MRPC R&D: Participants: CERN and UFRJ-Rio Objectives: - Studies of resistive plates (materials) - Development of construction techniques - Performance studies in testbeam Status: - First (small) prototype has been tested last year - prototype of 130cm x 230cm is under construction and will be studied this year using testbeams.

12/1/1999B. Schmidt / CERN Muon Frontend Electronics

12/1/1999B. Schmidt / CERN L0 Muon Trigger Algorithm (I) : start with pad hit in M3 (seed) extrapolate to M4 and M5 and look for hits within field of interest (FOI) search for hits in M2 and M1 and take hits closest to centre of search window calculate x- and y-slopes and find y-intercept at z=0

12/1/1999B. Schmidt / CERN L0 Muon Trigger Muon Momentum Measurement: Muon momenta are measured by means of the magnet spectrometer. In the bending plane the deflection angle  is given by: The transverse momentum P T is given by: P T = P tan  2 dim. tan  ) The momentum resolution is limited by: multiple scattering (material between IP andM2) the granularity of the muon chamber pads magnetic field map and alignment

12/1/1999B. Schmidt / CERN L0 Muon Trigger Distributions of P and P T for muons:

12/1/1999B. Schmidt / CERN L0 Muon Trigger Algorithm (II): calculate muon P T (P T -resolution is ~25%) apply cut on P T : 1GeV< P T <2GeV B  X efficiency of 8% -14% MB-retention of 1% - 3% (region of LHCb operation)

12/1/1999B. Schmidt / CERN Muon System Schedule Optimization of the muon detector Study of MRPC and CPC (WPC) prototypes in testbeam Design and and develop FE-electronics Accommodate L0 muon trigger to detector layout Choice of technologies for detector and electronics Finalize detecotor design Construction and test of full scale prototypes Technical Design Report (TDR) Construction and test of muon chambers Installation and commissioning of the muon system January 2000 July January

12/1/1999B. Schmidt / CERN LAPE Participation in the Muon Group Present situation: Physicists from UFRJ Rio de Janeiro are involved in various aspects of the muon system, in particular : - the research and development of MRPC, - the development of the related frontend-electronics, - the implementation of the L0 muon trigger. Future Possibilities: UFRJ can be a major production-center of the muon chambers and the frontend electronics. This will open a door to brazilian industry and result in an important technology transfer.

12/1/1999B. Schmidt / CERN Conclusion Physicists form UFRJ Rio de Janeiro are making a major contribution to the muon project of the LHCb experiment. The contribution of LAPE to LHCb is important for the experiment and has certainly a positive impact for science and industry in Brazil.