LHCb Muon System Alessia Satta on behalf of

LHCb Muon System Alessia Satta on behalf of LHCb Muon System: CAGLIARI, CERN, LNF, FERRARA, FIRENZE, PNPI, RIO, ROMAII 13/09/2005 Milano Bicocca

Outline o o Introduction Detector design Detector construction Physics with of muon data

LHCb physics o o A beauty dedicated LHC experiment: Indirect search for new physics in flavour sector, complementary to direct observation goal for Atlas or CMS n n CP violations : measurements of a b g Unique access to Bs: measurements of Dm and DG and mixing angle Rare decays Unique access to all beauty hadrons ex. Lb , B c

LHCb: a dedicated b experiment Beauty production peaks in forward- backward directions: a fixed target like detector layout

Muons in LHCb o Trigger: n n o Muons are ~ 200 KHz out of the 1 MHz first level trigger rate Inclusive muon selections fill 75% of 2 k. Hz stored data Offline n n Decay channels with muons: § Bs J/Y f § Bs J/Y h § Bs mm (Bd mm + D 0 mm) § B K* mm § …. tagging

Muon system design Design driven by first level (harware) trigger (L 0) o A rejection factor of mb of ~1/100 o Medium Pt > 1 Ge. V/c Good momentum resolution is required n No B field in the detector a station in front of the calorimeter q Trigger requires 5 hits out of 5 inside BX high efficiency in 25 ns

Muon system layout x, y rectangular pads: optimized granularity ~ MS contribution to s(1/PT) o High P-q correlation n Better granularity high h o 4 concentric regions n n pad linear dimensions double from an inner to an outer region 20 different pad sizes min 6. 3 x 31 mm max 250 x 310 mm at

Adopted technology o Multi Wire Proportional chambers with 4 ORed gas gaps (2 gaps in M 1 to reduce X 0) high efficiency n o + GEM chambers 1% area (see next talk) 1 Front End per 2 gaps (1 in M 1) rate capability and robustness 5 mm gas gap 2 mm wire pitch FE Wire ø 30 mm Ar /CO 2 /CF 4= 40/ 55/ 5 FE

Realization of the layout Large variation in pad dimensions and occupancy in the 5 x 4 regions + technology and cost constraints the desired layout is obtained by o n n n Chambers with cathode, wire, cathode+wire readout Pads or horizontal and vertical strips Strips reduce from 55 k 26 k trigger channels To minimize capacitance and deadtime, pads smaller than required by granularity are connected to a FE 120 k ORed FE channels o

MWPC performance efficiency Wire r/o o o Time resolution RMS < 4 ns XTalk ~ 10% Cathode r/o

Rates and aging o Large radiation dose in the inner regions of station M 1 and M 2 n n Rate =80(M 1 R 2), 35(M 1 R 3, M 2 R 1), < 15 (rest) k. Hz/cm 2 Integrated Q= 0. 9(M 1 R 1), 0. 5(M 2 R 1), < 0. 3 (rest) C/cm 10 years of running + safety factor 2 (M 1) 3(M 2 -M 5) L=2*10 32 o 5 years of running of M 1 R 2 ( > 8 per M 2 R 1 and >10 for the rest) have been tested and chamber performance is ok, wire ok - some etching on cathode and panel due to CF 4 content 5% WIRE Guard strip Golden Pad

MWPC construction o 1368 chambers automatic tools Ferrara wiring machine CERN soldering machine Used many automatic measurement tools panel planarity, wire tension, wire pitch

Status of production o o ~ 45% of the chambers have been produced Chamber tests on 100% of production n gas tightness HV gain uniformity Gas gap gain uniformity PNPI Production status

Electronic chain o Front End boards CARDIAC: n n o CARIOCA : Custom front end chip (ASD+BLR) unipolar, peaking time 10 ns deadtime ~60 ns DIALOG : Custom chip OR FE’s to achieve the required granularity introduce the delays per FE Off detector boards: n SYNC, a custom chip with TDC to allow the synchronization of the apparatus

L 0 muon trigger Completely hardware and fully synchronous o Track search in M 1 -M 5 n Seed in M 3 n Hits in M 4 and M 5 define a m track (20 l. I) n M 2 and M 3 hits predict M 1 hit position n M 1 and M 2 hits define m direction after magnet o B-kick to calculate PT (PT kick ~ 1. 2 Ge. V/c)

L 0 Muon performance o o o PT resolution ~20% High efficiency Very robust against high background level in the detector 125 k. Hz output rate efficiency Nominal condition 46% 88% + safety factors 41% 82% safety factor 2 in M 1 and 3 in M 2 -M 5 b m. X B JYf

HLT muon streams Lifetime unbiased dimuon stream (600 Hz) n n High rate dimuon trigger will provide invaluable calibration tool Distinctive mass peaks: J/Ψ…, …, Z… § → can be used to fix mass scale Sample selected independent of lifetime dominated by prompt J/Ψ allow study of IP and proper time res. in data Overlap with other triggers will allow proper time acceptance to be studied True J/Ψ rate 130 Hz → 109 events / year !

HLT muon streams (II) Inclusive single muon (900 Hz) o providing unbiased selection of ‘other B’ in event, invaluable for studying biases in exclusive trigger selection o useful for ‘data-mining’ o Straightforward & robust trigger; a reassuring lifeboat for early operation o High beauty purity: 550 Hz of true b→μ events in the 900 Hz o 109 perfectly tagged B decays / year ! o Add ~ 10% of effective statistics with respect to exclusive selection o Useful to recover decay modes difficult to trigger exclusively (e. g. Bs->Ks Ks)

Offline performance o o o Bs->J/Y f + Bs->J/Y h n Mixing angle of Bs : s~0. 05 (1 y) n DG/G : s~ 0. 02 (1 y) Bs->mm: 5 Years @ LHCb ~1/7 (1/5) of the effective tagging power is due to muons in Bs (Bd) Bs tagged as not oscillated: 1 year

Conclusions o The LHCb muon detector has n o Good time resolution, high efficiency, robustness, high rate capability, aging resistance Construction well advanced IRON filters chips MWPC