( ATLAS was designed for LHC: L=10 34 cm -2 s -1 ) [ Now we expect 7.5 x instantaneous and 10 x integrated luminosity ] PILEUP: from ~30 >200 proton collisions/BC Impact: High occupancy limits performance in vertex reconstruction and calorimeter. Maintain threshold for single isolated leptons as low as possible rejecting the pileup Strategy : higher granularity and faster tracking detectors: time is a fourth coordinate smarter Trigger DAQ 24/02/2016 G. Aielli - RPC 2016
Consequence on detectors Boosted objects up to =6 coverage High pileup and fast BC very fast and granular detectors Momentum resolution ≈15% at pT=10TeV ~1ns sharp BCID Particle flow capability for calorimeters with high granularity 25 mrad^2 Fine timing against pileup < 100 pS 24/02/2016 G. Aielli - RPC 2016
24/02/2016 G. Aielli - RPC 2016 s=10 mm 2 t=2ns t(ns)
24/02/2016 G. Aielli - RPC 2016 Absolute resolution fluctuations w.r.t. an external coherent source Relative resolution fluctuations of multiple pickup of the same external signal (2D, CS..) Time (ns) Amplitude (mV) Duration about 3 nsec Duration about 1.7 nsec Duration about 1.0 nsec
24/02/2016 G. Aielli - RPC 2016 1.2 mm 1 mm
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24/02/2016 G. Aielli - RPC 2016 (x1;t1) (x2;t2) L doi: /j.nima
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d >> CS z 1 d y mm Classic ATLAS case, spatial resolution limited by the strip pitch (y l ;t yl ;q yl clus ) (y k ;t yk ;q yk clus ) (x i ;t xi ;q xi clus ) (x j ;t xj ;q xj clus ) Definitions t 0 = real impact time v= signal propagation velocity (~0.15 m/ns) 2 = avalanche signal distribution width (FWHM) d= strip pitch t n = lowest time of a given cluster x n = strip id with the lowest time of a given cluster y n = strip id with the lowest time of a given cluster q yl clus = q yl estimated charge of the cluster (through ToT) Cluster list: y l ; y k ; x i ; x j ; Real hit list: (x i ; y l ) (x j ; y k ) Fake hit list: (x i ; y k ) (x j ; y l ) Pitch and CS 22 24/02/2016 G. Aielli - RPC 2016
(y l ;t yl ;q yl clus ) (y k ;t yk ;q yk clus ) (x i ;t xi ;q xi clus ) (x j ;t xj ;q xj clus ) Cluster list: y l ; y k ; x i ; x j ; Real hit list: (x i ; y l ) (x j ; y k ) Fake hit list: (x i ; y k ) (x j ; y l ) 24/02/2016 G. Aielli - RPC 2016
24/02/2016 1 mm gas gap 1.2 mm electrodes 100 x 50 cm^2 single gap 25 mm pitch strips New Front end G. Aielli - RPC 2016
Calibration The distribution of i 1, or t 0 i 1 (for single hits) gives the the measure of v/d and uncertainty distribution calibration. It’s a property of the system Uncertainty TDC bin; cable length, amplifier saturation, charge dispersion, strip pitch… FE noise contribution negligible 15.9 cm/ns cm/ns 24/02/2016 G. Aielli - RPC 2016
Compatibility with a real hit 62% fake cut Calibration curve with single hits Fake hits distribution The peak is displaced by taking wrongly coupled hits, the width is broadened by taking different avalanches 24/02/2016 G. Aielli - RPC 2016
1cm 200 ps resolution 100 ps resolution 24/02/2016 G. Aielli - RPC 2016
24/02/2016 G. Aielli - RPC % fake cut 95.5% efficiency
24/02/2016 G. Aielli - RPC ns 5 ns 20 ns
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No RPCs in the inner layer just MDTs 24/02/2016 G. Aielli - RPC 2016 OUTER LAYER for High pT trigger One doublet chamber MIDDLE LAYER for Low pT trigger Two doublet chambers IN TOTAL 6 independent layers measuring Eta and Phi Hard wired trigger system (on chamber)
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24/02/2016 G. Aielli - RPC 2016 increase the redundancy by adding the RPC inner layer 9 layers instead of 6 4 chambers instead of 3 This idea was already considered in the original project of the barrel trigger detector, but at that time the need for the 3 rd station was not stringent and it was canceled when a substantial downgrade was required to Atlas BM.CO BM.PI BO BI
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24/02/2016 G. Aielli - RPC 2016 BO BI BM Bunch crossing T0 T1 T2 5m 7,2m 9,5m
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24/02/2016 G. Aielli - RPC 2016 CERN-PH-EP arXiv: v2 [hep-ex] 25 Mar 2013
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24/02/2016G. Aielli - RPC 2016 The combination of a new electronics and an additional layer in the inner region will permit to gain several key advantages: