the$upgrade$program$of$the$lhcb$ … · the$upgrade$program$of$the$lhcb$...
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The upgrade program of the LHCb experiment at the Large Hadron
Collider Rudolf Oldeman
INFN Sezione di Cagliari and Università di Cagliari
On behalf of the LHCb collaboraCon
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The Large Hadron Collider
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Collides protons on protons head-‐on with Ecm=8 TeV every 50ns (13 TeV, 25ns in 2015)
The LHCb experiment
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~1/100 pp collisions produces b hadron decays in few ps (~few mm)
Cherenkov detectors
Tracking
calorimeters
~600 physicists from ~20 countries
muon detector
performance parameters: * 2<η<5 * σPV,xy~10μm * Δp/p 0.4%-‐0.6% * P(h→μ)~1%
LHCb trigger and readout • Maximum readout rate: 1MHz • Hardware trigger requires high-‐E µ or h
• ~90% eff for B→µ+µ-(X) • ~30% eff for B→hadrons • ~10% eff for charm
• full reconstrucCon @1MHz in 30k CPU ‘farm’ • pp bunch crossing every 50 ns (25ns in 2015) • with ~2 collisions each
– kept constant though luminosity levelling – achieved by displacing beams at coll. point
• ‘opCmum’ L=4x1032cm-‐2s-‐1 – rise in trigger threshold would overshadow gains
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LHCb highlights from 2011-‐2012 data
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• Strong evidence for Bs→µ+µ- decays arXiv:1307.5024
• CP-‐violaCng phase
LHCb-‐CONF-‐2013-‐006
• ObservaCon of D0 mixing PRL 110, 101802(2013)
• and 135 other published results... – See talks of S Perazzini, L. Anderlini, A.A.Alves Jr., M Zangoli and S. Amerio at this conference
Timeline
• 2011: 1p-‐1 at Ecm=7TeV, 50ns b-‐b • 2012: 2p-‐1 at Ecm=8TeV, 50ns b-‐b • 2013-‐2014: LS1 (first long shutdown) • 2015-‐2017: 5p-‐1 at Ecm=13TeV 25ns b-‐b • 2018: LS2 INSTALL LHCb UPGRADE • 2019-‐2021: 15p-‐1 • 2022-‐2023: LS3 (third long shutdown) • 2024-‐??: 10p-‐1 per year
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LHCb upgrade requirements
• instantaneous luminosity (1-‐2)x1033cm-‐2s-‐1 – on average 5 collisions per bunch crossing – integrated luminosity 50p-‐1
• full detector readout at every bunch crossing – to cope with higher luminosity – doubles B-‐>hadron efficiency
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Challenges • Fine segmentaCon
– to cope with <n>=5 • RadiaCon hardness
– 50p-‐1 • Low mass
– equal to or less then current • Fast readout
– 40MHz • Tremendous dataflow
– 40Tb/s • Complex networking for event building
– 12k fibers to 50k CPU • CompuCng power
– full event reconstrucCon @ 1-‐40MHz
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The LHCb upgrade
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kept parCally kept replaced removed
VELO upgrade: strips -‐> pixels 55x55µm, 40Mpixel Thin (200µm) sensor, ASIC 26 layers, 0.8%X0 each micro-‐channel CO2 cooling -‐20oC RF foil thinner: 300-‐>150µm, Si closer to beam: 8-‐>5.2mm
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The upstream tracker (UT)
• To replace the present TT – large-‐area tracking upstream of dipole magnet
– long lever arm improves dp/p – Crucial for Ks→π+π-‐, Λ→pπ-‐
• Keep 4 layers (0o,+5o,-‐5o,0o) • Thin (250µm) sensors, -‐5oC • Challenge for material budget <5%X0 • smaller pitch, length near center • Inner sensors circular cut
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Downstream tracking
• 3x4 planes 5x6m2
• present: IT(Si)+OT 4mm tubes (50ns dri{ Cme) • Too high mulCplicity for upgrade condiCons • Two opCons under consideraCon: – more silicon, shorter tubes – parCal or complete replacement with fiber tracker
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larger IT opCon
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• Increase fracCon of surface covered by Silicon • remake part of OT with shorter straws
ultra light-‐weight support structure
present half IT
half IT in upgrade
ScinCllaCng fiber opCon now baseline op<on
• 5-‐layer 250µm fibers. – 2.5m long, mirrored ends – 8000km to cover 12x (5x6m2)
• SiPM (1100x250µm) readout @ -‐50oC
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Ring Imaging Cherenkov detectors RICH1 aerogel+C4F10 RICH2 CF4
• Present: Hybrid photodetectors – silicon pixel inside image intensifier – pixel readout <=1MHz – need replacement
• New choice: ‘classic’ 8x8 MulC-‐Anode PMTs – square shape-‐>be|er surface packing than
cylindrical hybrids
• Remove aerogel from RICH1 • Increase radius of mirrors 2.7→3.8m
– both reduce occupancy • In LS3: TOF (TORCH) system behind RICH2 to
recover low-‐p PID?
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Calorimeter
• remove two ‘thin’ detectors in front of ECAL – ScinCllaCng pad detector, SPD – preshower, PRS
• not needed in 40MHz readout • reduce PMT HV to reduce ageing – 5x gain reducCon
• New low-‐noise high-‐gain frontend with 40MHz readout
• replace some inner modules in LS3
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Muon system
• Remove pre-‐CALO staCon M1 – was only used for trigger
• New off-‐detector electronics for 40HMz readout
• Replace some inner modules at LS3
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Readout&trigger
• ~12k opCcal fibers with 3.2Gb/s each • Straight to the surface – present LHCb has most electronics in cavern
• Common readout board • Full event reconstrucCon in farm • IniCally, farm won’t be able to handle 40MHz • Use exisCng hardware trigger (L0) as rate limiter (LLT) 10-‐40MHz
• Allow 20kHz to ‘tape’
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Physics prospects
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Many key measurements have small SM theory uncertainCes
Conclusion
• LHCb is preparing for major upgrade for 2019 • ‘Triggerless’ readout and higher granularity • Aim to run at 5xluminosity, 2xefficiency (for h) • AcCve R&D to make final technology choices • ImperaCve to reach full sensiCvity to new physics in the flavour sector at the LHC
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