ATLAS/CMS Upgrades Yasuyuki Horii Nagoya University on Behalf of the ATLAS and CMS Collaborations
Outline 2 /26 LHC/HL-LHC plan ATLAS/CMS upgrades Physics prospects
LHC/HL-LHC Plan
Overview 4 /26 SM precision studies and BSM searches with 13-14 TeV and 3000 fb -1 . Peak instantaneous luminosity: 5-7x10 34 cm -2 s -1 — a lot of challenges. Two upgrade phases: Phase 1 (2019-2020) and Phase 2 (2024-2026). http://hilumilhc.web.cern.ch/about/hl-lhc-project
Luminosity levelling 5 /26 The average luminosity is almost the same. HL-LHC is designed to operate with levelling. Lower pileup in the experimental detectors Lower energy deposition by the collisions in the interaction region magnets CERN-ACC-2015-0140
ATLAS/CMS Upgrades
Challenges 7 /26 Increased luminosity provides a significant challenge for the experiments. Upgrades are essential to exploit the full potential of LHC and HL-LHC. Higher radiation dose Replacement of some of the detectors Higher pileup Replacement of the electronics → Higher particle rate Overall modifications Higher event rate on the trigger and readout scheme
Inner tracker 8 /26 ATLAS CMS Inner trackers will be in an extreme environment at HL-LHC. 1 MeV neutron equivalent fluence up to 2 x 10 16 /cm 2 . Ionisation dose up to 10 MGy. Particle rates up to 2 GHz/cm 2 — high occupancy, high bandwidth. Pileup 140 expected at L = 5 x 10 34 cm -2 s -1 CMS CERN-LHCC-2015-010; LHCC-P-008
Inner tracker 9 /26 ATLAS Phase 2 Entire tracker replacement (all-silicon tracker) at the Phase 2 upgrade. Radiation tolerance, increased granularity, reduced material, extension to forward, … Ratio of reconstructed to generated tracks No pileup dependence with ≧ 11 hits Channel occupancy [%] for 200 pileups Pixel thickness possibly 150 µm, pixel size possibly 50 x 50 µm 2 CERN-LHCC-2012-022; LHCC-I-023. CERN-LHCC-2015-020; LHCC-G-166.
Inner tracker 10 /26 CMS Phase 1/2 Pixel detector replacement in the end of 2016 (as a Phase 1 project). Entire tracker replacement at the Phase 2 upgrade. Strip Pixel +Strip Pixel Pixel size considered: 25x100 µm 2 and 50x50 µm 2 Radiation tolerance, increased granularity, reduced material, extension to forward, … CERN-LHCC-2015-010; LHCC-P-008
Calorimeter 11 /26 CMS Phase 2 Endcap calorimeter will be replaced — longevity and performance issues. Hadron fluence 2 x 10 14 /cm 2 at | η | = 2.6. A high-granularity sampling calorimeter Defects in lead tungstate scintillating crystal with a tungsten/silicon electromagnetic of the electromagnetic calorimeter. part (EE) followed by brass/silicon (FH) and brass/scintillator (BH) hadronic parts. Fraction of the response Light transmission loss Response degradation also expected High performance at high pileup for the hadron calorimeter. CERN-LHCC-2015-010; LHCC-P-008
Muon spectrometer 12 /26 ATLAS Phase 1 New Small Wheel will be installed to cope with a relatively high hit rate (~15 kHz/cm 2 at L = 7 x 10 34 cm -2 s -1 ) and also to improve muon trigger. Micro-mesh gaseous detector (MM) Both MM and sTGC for precision tracking and trigger. Position resolution per layer: ~100 µm. Segment angle resolution at first-level trigger: ~1 mrad. Coverage: 1.3 < | η | < 2.7. CERN-LHCC-2013-006; ATLAS-TDR-020
Trigger 13 /26 ATLAS CMS More luminosity — more interesting events but also more background. Without changes, trigger rates exceed the limits of trigger/readout system. Choice of ATLAS and CMS at Phase 2 upgrades Increase trigger rates. First level: ~100 kHz → 750-1000 kHz Storage level: ~1 kHz → 5-10 kHz Increase latency — improve algorithm. First level: ~3 µs → 6-12.5 µs Simply increasing the threshold Electronics replacements for all sub-systems. would kill the signal. CERN-LHCC-2012-022; LHCC-I-023. CERN-LHCC-2015-019; LHCC-G-165. CERN-LHCC-2015-020; LHCC-G-166.
Trigger 14 /26 CMS Phase 2 Track trigger implementation in the first-level trigger. Benefits: improved p T determination, better identification of charged leptons, … Technologies: studies ongoing for Associative Memories, FPGA, … Electron trigger Muon trigger CERN-LHCC-2015-010; LHCC-P-008.
Trigger 15 /26 ATLAS Calorimeter trigger upgrade Muon trigger upgrade Higher granularity information Extend muon trigger acceptance provided at first-level trigger. in the barrel by additional chambers. Less sensitive to pileup. Phase 2 Current Additional RPCs Phase 1 Muon A x ε in barrel could be improved from ~70% to ~95%. Trigger rate reduction for e, γ , … CERN-LHCC-2013-017; ATLAS-TDR-022-2013. O. Kortner, VCI 2016.
Physics Prospects — Examples
ttH 17 /26 Direct probe of Higgs-top coupling. Events / ( 2 GeV ) ATLAS Simulation Preliminary 300 ∫ -1 L dt = 3000 fb , s =14 TeV Simulation 200 Background Fit 100 0 100 120 140 160 200 Background subtracted events Signal Fit 0 gg → H and H →γγ indirect (loops). 100 120 140 160 m [GeV] γ γ Observation expected for ttH, H →γγ . ATLAS expected: 8.2 σ (3000 fb -1 ). ATL-PHYS-PUB-2014-012
H → bb 18 /26 Access to Higgs-bottom coupling. Events / 20 GeV Events / 20 GeV 90000 ZH x 10 ATLAS Simulation VH(bb)x10 ATLAS Simulation Diboson VZ Preliminary 80000 Preliminary 2500 WW t t -1 s = 14 TeV, 3000 fb , < > = 140 Multijet µ Z+bb -1 70000 s = 14 TeV ∫ L dt = 3000 fb < > = 140 t t µ Z+bl Z 2 lep, 2 jets, 2 tags, p > 200 GeV t, s+t-chan T Z+cc 2000 V 1 lep., 2 jets, p > 200 GeV Wt 60000 Z+cl T W+bb Z+l W+bl 50000 Unc. W+cc 1500 W+cl W+l 40000 Z+bb Unc. 1000 30000 20000 500 10000 0 0 50 100 150 200 250 50 100 150 200 250 m [GeV] m [GeV] bb bb Observation expected for VH, H → bb (V = Z or W). ATLAS expected significance at 3000 (300) fb -1 : 8.8 σ (3.9 σ ). ATL-PHYS-PUB-2014-011
H → µµ 19 /26 Access to Higgs-muon coupling. 5000 (Data - Background) / 0.5 GeV Events / 0.5 GeV 10 10 ATLAS Simulation Preliminary ATLAS Simulation Preliminary 4000 = 14 TeV s s = 14 TeV 9 10 3000 H , m =125 GeV -1 → µ µ L dt = 3000 fb -1 ∫ ∫ L dt = 3000 fb H 8 Z → µ µ 10 2000 t t 7 1000 10 WW → µ ν µ ν 0 6 10 -1000 5 10 -2000 S+B toy Monte Carlo 4 10 -3000 S+B model 3 10 -4000 B-only model 2 -5000 10 80 100 120 140 160 180 200 100 110 120 130 140 150 160 m [GeV] m [GeV] µ µ µ µ Reduction of the material and better Observation expected for H → µµ. spacial resolution for tracking at Phase 2. Mass resolution expected: ATLAS expected: 7.0 σ (3000 fb -1 ). 40% better with respect to ‘Phase 1 aged’ (radiation damage for 1000 fb -1 assumed). CERN-LHCC-2015-010; LHCC-P-008. ATL-PHYS-PUB-2013-014.
Higgs couplings 20 /26 ATLAS Simulation Preliminary Fit with a fully generic parametrisation -1 -1 ∫ ∫ s = 14 TeV: Ldt=300 fb ; Ldt=3000 fb No assumption on the total width κ gZ κ gZ (= κ g κ Z / κ H ) overall scale parameter λ WZ common to all signal channels λ tg No assumption on new particle contribution λ through loops bZ λ Z τ Hashed areas: current theory systematic uncertainties λ Z µ λ gZ For various coupling scale factor ratios, λ γ Z the precision of % level expected at 3000 fb -1 . λ (Z γ )Z Similar precision expected for ATLAS and CMS. 0 0.05 0.1 0.15 0.2 0.25 κ X = ( ) ∆ λ ∆ κ XY Y ATL-PHYS-PUB-2014-016. arXiv:1307.1347 [hep-ph].
Higgs couplings 21 /26 -1 3000 fb (14 TeV) 1/2 CMS or (g/2v) t Projection 1 WZ 68% CL -1 10 λ b τ -2 10 µ -3 10 -4 10 0.1 1 10 100 mass (GeV) Significant improvement expected with 14 TeV, 3000 fb -1 . Precision test of Yukawa terms for various ‘flavors’: t, b, τ , and µ. CERN-LHCC-2015-019; LHCC-G-165
B s,d → µµ 22 /26 B s,d → µµ decays are only proceed CMS and LHCb, Nature 522, 68 (2015) through FCNC processes B (B s → µµ) = (2.8 +0.7-0.6 ) x 10 -9 and are highly suppressed in SM. B (B d → µµ) = (3.9 +1.6-1.4 ) x 10 -10 C. Bobeth, et al., PRL 112, 101801 (2014) ATLAS, arXiv:1604.04263 [hep-ex] B (B s → µµ) = (3.65 ± 0.23) x 10 -9 B (B s → µµ) = (0.9 +1.1-0.8 ) x 10 -9 B (B d → µµ) = (1.06 ± 0.09) x 10 -10 B (B d → µµ) < 4.2 x 10 -10 (95% CL) D. M. Straub, arXiv:1012.3893 Some of new physics scenarios may boost the B s,d → µµ decay rates. B s /B d ratio provides a stringent test of various models beyond SM.
B s,d → µµ 23 /26 300 fb -1 3000 fb -1 S/(S+B) Weighted Events / ( 0.02 GeV) S/(S+B) Weighted Events / ( 0.01 GeV) 500 CMS Simulation CMS Simulation 120 -1 -1 Scaled to L = 3000 fb Scaled to L = 300 fb data data | ( )|<1.4 | ( )|<1.4 η µ η µ full PDF full PDF 400 100 - + B - → µ µ + B → µ µ s s - + B → µ µ - + B → µ µ d d combinatorial bkg combinatorial bkg 80 300 semileptonic bkg semileptonic bkg peaking bkg peaking bkg 60 200 40 100 20 0 0 4.9 5 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 4.9 5 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 m (GeV) m (GeV) µ µ µ µ B (B s → µµ) precision: 13% B (B s → µµ) precision: 11% B (B d → µµ) precision: 48% (2.2 σ ) B (B d → µµ) precision: 18% (6.8 σ ) σ x B predicted by SM assumed. CERN-LHCC-2015-010; LHCC-P-008. K. F. Chen, EPS-HEP 2015.
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