Pion misidentification in several IFR configurations Francesco Fabozzi Università degli Studi di Napoli Federico II INFN Sezione di Napoli
Introduction Several configurations proposed for an IFR upgrade aiming to improve muon efficiency New high-efficiency chambers Double gaps RPC reduce pion misid. Increase of the overall thickness of the absorber material Where? Replacement of intermediate RPC layers Addition of absorber before the last RPC layer (easy in the Forward Endcap) IFR Improv. Workshop - Jan 18 2001 Francesco Fabozzi 2
Pion misidentification Which is the level of pion misidentification in some of the proposed IFR configurations? Generation of MC single pions IFR simulated in 3 different configurations Current muon selector Tight and Very Tight criteria applied Bulk of the pion misid. Looking at the MC-truth we can distinguish Pions never interacting in the material: punch-through Pions decaying in flight IFR Improv. Workshop - Jan 18 2001 Francesco Fabozzi 3
Pion decays and punch-through A simple model of the BABAR detector Fraction 1 0.9 0.8 01/01/05 12.43 No No muon muon selection applied applied No inelastic interactions (stop or escape) 0.7 0.6 I.P. 81cm 0.5 DCH EMC IFR 136cm 0.4 0.3 0.2 0.1-102cm -156cm 175cm 256cm 0 0 0.25 0.5 0.75 1 1.25 1.5 1.75 2 2.25 2.5 p (GeV/c) IFR Improv. Workshop - Jan 18 2001 Francesco Fabozzi 4
Configurations 1. Simple upgrade: just chambers replacement New double-gap RPCs in all the IFR Layer efficiency = 99% No replacement of the layer 19 in the Barrel It was considered OFF 10 cm of iron are lost 2. New chambers + more absorber Layers 7, 9, 11, 13, 15 replaced by 2 cm of Fe-equiv. More iron in the Forward Endcap Recover the lost iron in the Barrel 3. New chambers + more absorber + 10 cm Fe-equiv. more in the Forward Endcap IFR Improv. Workshop - Jan 18 2001 Francesco Fabozzi 5
Simple upgrade: configuration 1 10 cm of iron in the Barrel are lost λ distribution for pions towards lower values increase of the misid. λ distribution: increase of the # of measured interaction length with momentum Barrel Forward λ λ λ < 1 λ p(gev/c) p(gev/c) IFR Improv. Workshop - Jan 18 2001 Francesco Fabozzi 6
Configuration 1: performances Performances are lower in the barrel also the bulk misid. is higher all all theta theta forward forward Punch-through Decays in the IFR Decays in the EMC Decays in the DCH Tight Tight Tight barrel barrel p(gev/c) p(gev/c) p(gev/c) Very tight Very tight Very tight p(gev/c) p(gev/c) p(gev/c) IFR Improv. Workshop - Jan 18 2001 Francesco Fabozzi 7
Addition of absorber: configuration 2 Barrel Forward Absorber thickness in the Barrel < absorber thickness in the Forward the peak of the Barrel distribution is still at a lower λ Recover of the absorber thickness in the Barrel the # of tracks with λ < 1 is not so different in the two sectors λ IFR Improv. Workshop - Jan 18 2001 Francesco Fabozzi 8
Configuration 2: performances The punch-through in the Barrel has been significantly reduced Also the increase of misid. with momentum has been reduced all all theta theta forward forward barrel barrel Tight Tight Tight p(gev/c) p(gev/c) p(gev/c) Very tight Very tight Very tight p(gev/c) p(gev/c) p(gev/c) IFR Improv. Workshop - Jan 18 2001 Francesco Fabozzi 9
More iron in the forward: configuration 3 Barrel Forward The supplementary 10 cm Feequiv. of absorber in the Forward change significantly the λ distribution more tracks with a high value of λ λ IFR Improv. Workshop - Jan 18 2001 Francesco Fabozzi 10
Configuration 3: performances The bulk of the misid. in the Forward has been further reduced warning: low statistics for this MC sample all all theta theta forward forward barrel barrel Tight Tight Tight p(gev/c) p(gev/c) p(gev/c) Very tight Very tight Very tight p(gev/c) p(gev/c) p(gev/c) IFR Improv. Workshop - Jan 18 2001 Francesco Fabozzi 11
Conclusions Adding more absorber in the IFR helps: not to decrease performances of the muon selection in the Barrel if layer 19 won t be replaced Improve performances of the muon selection in the Forward With the addition of a total of 20 cm Fe-equiv. in the Forward we can significantly reduce the pion misidentification in that sector IFR Improv. Workshop - Jan 18 2001 Francesco Fabozzi 12