Update on LHC Searches: experimental techniques and recent results - PowerPoint PPT Presentation

Update on LHC Searches: experimental techniques and recent results Ayana Arce ANL Lattice x BSM Workshop April 21 st 2016

Looking back… 900 H → γγ events 1380 colliding bunches (50 ns spacing) 20M dijet events 400 Hz for prompt analysis (+up to 600 Hz “delayed”) pileup: in ~5 cm! 2

Looking back… 900 H → γγ events 1380 colliding bunches (50 ns spacing) 20M dijet events 400 Hz for prompt analysis (+up to 600 Hz “delayed”) pileup: in ~5 cm! 0 non-SM observations 3

Recent developments 4

Recent developments WJS2013 100 ratios of LHC parton luminosities: 13 TeV / 8 TeV gg _ luminosity ratio Σ qq qg 10 MSTW2008NLO 1 100 1000 M X (GeV) long shutdown (2013-2015): • LHC splice repair to allow 13 TeV collisions – parton luminosity at 2 TeV increased more than 5x – 2x more colliding bunches ➜ experiments collected 1.9-3.2 fb -1 • detector upgrades in ATLAS/CMS

Recent developments • ATLAS: – new innermost tracking layer: better vertex reconstruction – muon trigger improvements new pixel layer in existing tracker new pixel layer in existing tracker • CMS: – more muon coverage (trigger improvements) – new luminosity detectors – new calorimeter trigger (pileup robust) 6

(atlas) Muon drift tubes + cathode strips Muon drift tubes + cathode strips μ -ID efficiency > 99% in tracker acceptance two magnets: ~3% m μμ resolution throughout Inner tracker: to | Inner tracker: to | η |~ 2.5 |~ 2.5 10-20 μ m in R- φ : ( ~30x c τ (B)) Central calorimeters (to | Central calorimeters (to | η |~2.5) |~2.5) granularity ~ 0.025 (EM, LAr) to 0.1 (HAD, Tile) 7

(cms) muon systems tracking < 2% p T resolution 10-20 μ m in R- φ : (Z → μμ , barrel) ( ~30x c τ (B)) LHC probes of new interactions: • leptons and photons • “missing energy” • jets • weak and Higgs bosons Barrel/endcap calorimeters (to | (to | η |~3) |~3) granularity ~ 0.0174 (EM, PbWO4) • photon momentum resolution ~1% (central, unconverted) 8

leptons +2% Dedicated reconstruction: clean signatures 9

photons CMS ATLAS inner detector material up to 2X 0 up to 2.5 X 0 energy resolution 1.5-3% (unconverted) 10%/ √ E (+) 1% energy scale 0.1-0.3% 0.2-0.5% 10

jets CMS Simulation s = 8 TeV 0.5 > GEN Anti-k , R=0.4 (PF+CHS) T 0.45 T /p | | < 1.3 η 0.4 T )/<p =0 µ 0.35 0 < 10 ≤ µ GEN 0.3 10 < 20 ≤ µ T /p 20 < 30 ≤ µ T 0.25 (p 30 < 40 ≤ µ σ 0.2 0.15 0.1 0.05 0 20 30 100 200 1000 GEN p [GeV] T better than 10% resolution above 0.1 TeV 11

b-jets +6% combine discriminating variables: ‣ N tracks , m vertex L xy ‣ vertex L xy significance ‣ track impact parameter d 0 ‣ vertex p T ratio d 0 ATLAS tracker upgrade ~doubles rejection power at 60% efficiency • b-jets identified by tracker properties: useful independence from calorimeter – muons, neutrinos in b-jets degrade jet energy response and resolution 12

W/Z bosons Efficient: pairs of quarks quarks Pure: isolated electrons and muons and/or missing transverse energy 13

t/W/Z jets ATLAS & CMS: gr groomed mass + oomed mass + substructure substructur e tags ⌫⌫ `` q ¯ q Z → (70%) (20%) (10%) – typical top tag: 50% efficiency, light jet rejection factor ~10 W → `⌫ (33%) 23% 7% 3% – typical boson tag: 50% efficiency, rejection q (67%) 47% 13% 7% W → q ¯ factor of 30-40 ` ´ P i p T i min ´ R (1 ;i ) ; ´ ´ ´ ; ´ R ( N;i ) fi N = P R jet i p T i 14

higgs bosons look in γ , τ , W, b pairs pure • optimal for low-p T BSM Higgs production efficient • better for higher p T or second tag – b decays degrade mass resolution 15

Impact of LS1 activities Excited quarks? TeV 8 TeV → 13 TeV gravity? new pixel layers (ATLAS) natural explanations for EWSB? new displaced vertex reconstruction (CMS) optimized boosted compositeness/warped ED hadronic decay tagging signatures improved muon reconstruction BSM higgs decays (CMS) new beam structure/ larger systematic uncertainties detector hardware (for now) 16

SEARCHES SEARCHES 17

Resonance searches with Higgs • Strategy: exploit ef efficiency ficiency – b-tags are powerful (but efficiency falls off at high m X due to b-tag merging) – top backgrounds can remain 18

Resonance searches in X → HH CMS CMS fully-hadronic search for 13 TeV → improved Run 2 b-tagging (72% efficient, rejection ~ 100) interpreted as G* and scalar search limit extended to 850 GeV 19

Resonance searches in X → HH 20

Resonance searches with W/Z • Look out for 2 TeV… • Strategy: • constrain BG to data • maintain/improve performance • increase overall acceptance 21

Increasing acceptance: Z → νν fit Z+jet, W+jet, top backgrounds in enriched sidebands * one or two leptons; b-tag 22

All-hadronic (ATLAS) • Same kinematic cuts as Run 1 • different boson tagging – ATLAS maintains cut on n(trk) to improve sensitivity 23

All-hadronic (CMS) check signal efficiencies tight selection 24

WZ summary (ATLAS) monojet monojet channel adds a str channel adds a strong ong constraint constraint no unusual featur no unusual features es one lepton all-hadronic monojet

WZ combination (CMS)

diphoton resonance search irr irreducible, smooth backgr educible, smooth background ound 27

diphoton resonance search irr irreducible, smooth backgr educible, smooth background? ound? 28

local local significance @ 750 GeV ATLAS TLAS CMS CMS 29

Testing the γγ excess Z γ with leptons with leptons Z γ with jets with jets

Testing the γγ excess 31

Testing the γγ excess CMS: similar sensitivity at 750 GeV (leptons only) CMS: similar sensitivity at 750 GeV (leptons only)

di-top ATLAS search in clean semileptonic • channel top tag efficiency and rejection • ~flat with p T 33

searches for vector-like quarks ATLAS t, b Q W ⌥ , Z 0 , H W ± , Z 0 , H ¯ Q t, ¯ ¯ b CMS ¯ b Q u d 34

VLQ search overview complex: final states simple: VLQ decay 35

search for heavy TT production ATLAS: single-lepton channel busy final state: use small radius jets and “reclustered” boson/top jets 36

search for heavy TT production 37

TT and single-T limits 38

Outlook • Collisions (now-2018)! Collisions (now-2018)! – intensity ramp thr intensity ramp through spring ough spring – July: ~6 fb July: ~6 fb -1 -1 • pileup increases: – modest in 2017, but tremendous for high- luminosity upgrade • boost increases: – b-tagging? Higgs and boson tagging? 39

Conclusions • New search results poured in from early Run 2 dataset… – new physics explanations for ATLAS VV excess are disfavored – a new diboson excess to make bets on for summer • A sure bet: LHC/detector improvements and new analysis tools play a starring role 40

handling high pileup standar standard gr d grooming ooming event-by-event corr event-by-event corrections ections 41

tracks vs. pileup and boost track-assisted substructure (bonus: simplified uncertainGes) track-based pileup removal 42

kilometers apart… CMS CMS ATLAS TLAS • HVT Model B • HVT Model A – CHM-like: suppressed – EGM-like: comparable fermion couplings fermion &vector couplings • RS model with k/M ~ 0.1 • RS model with k/M ~ 1 – higher cross-section, broader resonance 43

Higgs strategies Resolved analysis Resolved analysis Di- Di-higgs higgs signal ef signal efficiency ficiency 44

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Resonance searches with Higgs ATLAS searches for WH,ZH with H → bb: 46

1512.05099 combination of diboson searches aKer combinaGon, local excess significance is strongly reduced: (to 2.6 sigma) 47

CMS summary 48