1. Particle rate in M1 and M2 Muon Meeting 13-02-2004

2. Why “new” particle rate ? The rate values and consequently the expected integrated charge used as upper limit for aging validation are derived from the TDR number. Unfortunately those numbers are not valid anymore. –The TDR simulation is obsolete, it includes many bugs now fixed –The beam pipe shielding -which affects the rate largely – has been reduced ( realistic now !) –Too high threshold was used for simulation in the past – particles with kinetic energy < 100KeV did not leave signal in the detector better use the rate resulting from new simulation

3. New rate estimation M1M2 R120036 R28412 R3283 R4120.6 Max rate in the regions over few cm 2 area Background safety factor applied: multiplied by 2 the rate in M1; multiplied by 5 the low energy hits in M2 Luminosity = 2x10 32 cm -2 s -1 Rate of particles crossing one gap ( KHz/cm 2 )

4. Integrated charge estimation (I) Since the charge deposit is proportional to track length in gas the rate reported in previous slide must be corrected including the track angle M1M2 R125663 R210823 R3406 R4161.5 Effective rate (KHz/cm2) including track length

5. Integrated charge (II) Due to different particle composition and momentum in the different regions of the detector we should also take into account the different dE/dx According to the simulation the average energy deposit in the different stations is similar within 10% The average dE/dx is that of a particle with  100 (pions of ~10GeV)  dE/dx (a.u.)

6. Integrated charge (III) Combining the previous number and assuming –0.88pC is the charge deposit by a 10GeV pion penetrating perpendicularly the gas gap –M1 and M2R1-R2 uses sym. Readout –2mm wire pitch M1M2 R12.20.55 R20.950.20 R30.350.10 R40.120.03 C/cm in 10 LHCb year

7. Integrated charge (IV) The integrated charge reported in previous slide refers to the most irradiated part in each region. Since the rate varies more than a factor 4 from the most to the less irradiated point within a region, just reshuffling the chambers after 5 years it is possible to halve the integrated charge Particles rate in M2R1

8. Inefficiency due to deadtime in M1 using the new rate assuming a deadtime long ~ 3 bunch crossing assuming a 80% fraction of the rate due to long tracks (i.e. tracks traversing both gaps) Rate KHz/ cm 2 Corr. rate Ch. Size (cm 2 ) Deadti me R12001602.54% R2846853.4% R32822204.4% R41210808% The deadtime inefficiency in table refers to the most irradiated channels.