The Trigger and Real-time Reconstruction at LHCb CPAD Instrumentation Frontier Workshop 2019 Daniel Craik on behalf of the LHCb collaboration Massachusetts Institute of Technology 9th December, 2019 Photo: User:Emery / Wikimedia Commons / CC-BY-SA-2.5
The LHCb detector Instrumented in the forward region to exploit forward-production of c - and b -hadrons b θ 1 z θ 2 b LHCb MC s = 14 TeV Located at point 8 of the LHC 0 π /4 General-purpose detector in the forward region 0 π /2 θ [rad] π /4 2 3 π /4 π /2 Specialised in studying b - and c -decays 3 π /4 π θ [rad] π 1 Dan Craik (MIT) Trigger & Real-time Reconstruction @ LHCb 2019-12-09 1 / 23
The LHCb detector JINST 3 (2008) S08005 Instrumentation in the forward region (2 < η < 5) Excellent secondary vertex reconstruction Precise tracking before and after magnet Good PID separation up to ∼ 100 GeV / c Dan Craik (MIT) Trigger & Real-time Reconstruction @ LHCb 2019-12-09 2 / 23
LHCb timeline Run I LS 1 Run II LS 2 Run III LS 3 Run IV LS 4 Runs V+ LHC HL-LHC 2010 2012 2014 2016 2018 2022 2024 2026 2028 2030 2032 now Phase I Upgrade Phase Ib Upgrade Phase II Upgrade Triggerless readout at 40 MHz Possible stepping stone Upgrade for HL 9 fb − 1 50 fb − 1 300 fb − 1 LHCb may be only dedicated B -physics experiment Belle 2 50 ab − 1 timetable may shift Dan Craik (MIT) Trigger & Real-time Reconstruction @ LHCb 2019-12-09 3 / 23
Real-time reconstruction in Run II “Offline”: grid computing “Online”: near detector Hardware 1st software 2nd software 40 MHz 1 MHz 100 kHz 5 kHz 5 kHz Reconstruction Analysis Run I: trigger trigger trigger Align + Calib high p T , E T partial reco full reco µ s ms Time from collision: hours weeks Online Offline Hardware 1st software 9PB buffer 2nd software 40 MHz 1 MHz 100 kHz 100 kHz 12 kHz Analysis Run II: trigger trigger Real-time trigger (Turbo) Align + Calib high p T , E T partial reco full reco µ s ms Time from collision: hours hours Calibration and alignment of Run I data performed “offline” weeks after data taking Trigger reconstruction different from offline In Run II, data buffered before final trigger stage Allows for real-time alignment and calibration Offline-like reconstruction within the trigger Many analyses use “Turbo-stream” data – online reconstruction, full raw event not saved Dan Craik (MIT) Trigger & Real-time Reconstruction @ LHCb 2019-12-09 4 / 23
Real-time reconstruction in Run II Real-time alignment and calibration performed for vertex locator, RICH detectors, tracking stations, calorimeter and muon stations Will focus on velo and RICH Alignment particularly important for velo, which opens and closes between fills Gas-filled RICH detectors also require frequent calibration Dan Craik (MIT) Trigger & Real-time Reconstruction @ LHCb 2019-12-09 5 / 23
Real-time reconstruction in Run II Each alignment task performed once per fill Alignment begins once a large enough dataset has been collected Calibration of RICH gas refractive index performed regularly to account for temperature/pressure changes within the radiator gas LHCb Preliminary LHCb Preliminary align + calib initial improved Dan Craik (MIT) Trigger & Real-time Reconstruction @ LHCb 2019-12-09 6 / 23
Real-time alignment of the Velo Vertex locator modules sit 5 mm from the LHC beam Consists of two retractable halves (one shown) Modules formed of two sections – one on each velo half During beam injection, velo retracted to 35 mm for safety Closed once LHC beams are stable Moves every fill → align every fill Dan Craik (MIT) Trigger & Real-time Reconstruction @ LHCb 2019-12-09 7 / 23
Real-time alignment of the Velo Alignment of velo based on minimising residuals between hits and ∆ Tx reconstructed tracks x Plot shows x and y translation between the two velo halves z m] 20 Tolerance of ± 2 µ m allowed without x-translation µ LHCb VELO Variation [ y-translation 15 alignment update (empty markers) Preliminary 10 5 Updates may also be caused by other 0 degrees of freedom − 5 e.g. offsets or rotations within a velo − 10 − half 15 − Empty markers = no update 17/04/2018 - 21/11/2018 20 100 200 Alignment number [a.u.] Dan Craik (MIT) Trigger & Real-time Reconstruction @ LHCb 2019-12-09 8 / 23
� � Real-time calibration of the RICH NIM A 12 (2016) 041 RICH detectors provide particle ID information based on angle of Cherenkov radiation Magnetic Shield Index of refraction of the gas radiators sensitive to Photon Detectors changes in temperature, pressure and composition 250 mrad These features are monitored but data-driven calibration Spherical also required Mirror C4F10 Beam pipe Compare recorded and expected Cherenkov angles (bottom left) Track VELO exit window Alignment of mirrors also calibrated (bottom right) Plane Rich1Gas Rec-Exp Cktheta | All photons Rich1Gas Rec-Exp Cktheta | All photons Entries 3.643921e+08 Mean 0.0002294 Mirror × 10 3 Std Dev 0.004334 Entries χ 2 / ndf 1711 / 90 2800 3 × 10 10 3 Run 182551 Gaus Constant 8.645e+05 0.002 × SF 1.025672 [rad] 0.002 Gaus Mean 0.0006738 AD 1100 Gaus Sigma 0.001926 R 2600 p3 1.905e+06 0.0015 θ 0.0015 p4 1.09e+07 θ 1100 ∆ ∆ p5 − 2.062e+09 1000 0.001 p6 1.113e+11 0.001 2400 1000 0.0005 0.0005 900 900 2200 0 0 800 -0.0005 800 -0.0005 2000 -0.001 0 100 200 z (cm) 700 -0.001 700 1800 -0.0015 -0.0015 600 600 -0.002 -0.002 1600 0 2 4 6 0 2 4 6 − 0.008 − 0.006 − 0.004 − 0.002 0 0.002 0.004 0.006 0.008 delta(Cherenkov Theta) / rad φ [rad] φ R AD Mon Aug 29 05:41:53 2016 � 3 Dan Craik (MIT) Trigger & Real-time Reconstruction @ LHCb 2019-12-09 9 / 23
JINST 14 (2019) P04006 The turbo stream Save only parts of the event needed for offline analysis Multiple persistence levels Only candidate ( ∼ 7 kB) Part of event ( ∼ 16 kB) Full event ( ∼ 48 kB) cf. Non-turbo ( ∼ 69 kB) Used by many analyses, e.g. × × 10 3 10 3 Candidates / σ [ m ( µ + µ − )]/ 2 7 10 2200 2 ) ) c 180 2 LHCb 2 LHCb LHCb prompt-like sample Candidates per 5 MeV/ LHCb 13 TeV 2000 ⇒ isolation c c 6000 6 √ s = 13 TeV Candidates / ( 0.1 MeV/ Candidates / ( 0.1 MeV/ 10 160 applied 1800 p T ( µ ) > 1 GeV, p ( µ ) > 20 GeV Data Data Data 140 5000 1600 Total 5 10 0 → − + 0 → π − π + prompt µ + µ − D K K 1400 D 120 Signal 4000 Background 1200 4 µ Q µ Q 100 Comb. bkg. Comb. bkg. 10 1000 3000 hh + hµ Q 80 3 800 10 60 2000 600 2 40 400 10 1000 20 200 0 0 0 3 4 5 2005 2010 2015 2020 2005 2010 2015 2020 10 10 10 3500 3600 3700 π + π + m ( µ + µ − ) [ MeV ] Ξ ++ ( 0 ) [MeV/ 2 ] ( 0 ) [MeV/ 2 ] m ( ) [MeV/ c 2 ] m D c m D c cand cc Observation of Ξ ++ CP violation in charm decays Search for dark photons decaying to dimuons cc PRL 122 (2019) 211803 PRL 120 (2018) 061801 PRL 119 (2017) 112001 Dan Craik (MIT) Trigger & Real-time Reconstruction @ LHCb 2019-12-09 10 / 23
Recommend
More recommend
