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 21st 2016

Looking back…

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1380 colliding bunches (50 ns spacing)

pileup: in ~5 cm!

900 H → γγ events 20M dijet events 400 Hz for prompt analysis (+up to 600 Hz “delayed”)

Looking back…

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1380 colliding bunches (50 ns spacing)

pileup: in ~5 cm!

900 H → γγ events 20M dijet events 400 Hz for prompt analysis (+up to 600 Hz “delayed”) 0 non-SM

• bservations

Recent developments

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Recent developments

100 1000 1 10 100

gg Σqq qg

WJS2013

ratios of LHC parton luminosities: 13 TeV / 8 TeV

luminosity ratio MX (GeV)

MSTW2008NLO

_

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

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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)

(atlas)

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

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(cms)

LHC probes of new interactions:

• leptons and photons
• “missing energy”
• jets
• weak and Higgs bosons

tracking 10-20 μm in R-φ: (~30x cτ(B)) muon systems < 2% pT resolution (Z →μμ, barrel) Barrel/endcap calorimeters (to | (to |η|~3) |~3) granularity ~ 0.0174 (EM, PbWO4)

• photon momentum resolution ~1%

(central, unconverted)

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leptons

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+2%

Dedicated reconstruction: clean signatures

photons

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CMS ATLAS inner detector material up to 2X0 up to 2.5 X0 energy resolution 1.5-3% (unconverted) 10%/√E (+) 1% energy scale 0.1-0.3% 0.2-0.5%

jets

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[GeV]

GEN T

p

20 30 100 200 1000

>

GEN T

/p

T

)/<p

GEN T

/p

T

(p σ

0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5

=0 µ < 10 µ ≤ < 20 µ ≤ 10 < 30 µ ≤ 20 < 40 µ ≤ 30

= 8 TeV s CMS Simulation

, R=0.4 (PF+CHS)

T

Anti-k | < 1.3 η |

better than 10% resolution above 0.1 TeV

b-jets

• b-jets identified by tracker properties: useful independence

from calorimeter

– muons, neutrinos in b-jets degrade jet energy response and resolution

combine discriminating variables:

• Ntracks, mvertex
• vertex Lxy significance
• track impact parameter d0
• vertex pT ratio

ATLAS tracker upgrade ~doubles rejection power at 60% efficiency Lxy d0

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+6%

W/Z bosons

Pure: isolated electrons and muons and/or missing transverse energy

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Efficient: pairs of quarks quarks

t/W/Z jets

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fiN = P

i pTi min

` ´R(1;i); ´ ´ ´ ; ´R(N;i) ´ Rjet P

i pTi

ATLAS & CMS: gr groomed mass +

• omed mass +

substructur substructure e tags

– typical top tag: 50% efficiency, light jet rejection factor ~10 – typical boson tag: 50% efficiency, rejection factor of 30-40

Z → q ¯ q ⌫⌫ `` (70%) (20%) (10%) W → `⌫ (33%) 23% 7% 3% W → q ¯ q (67%) 47% 13% 7%

higgs bosons

• optimal for low-pT BSM

Higgs production

• better for higher pT or

second tag

– b decays degrade mass resolution

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efficient pure

look in γ, τ, W, b pairs

Impact of LS1 activities

8 TeV → 13 TeV Excited quarks? TeV gravity?

new pixel layers (ATLAS)

natural explanations for EWSB?

new displaced vertex reconstruction (CMS)

• ptimized boosted

hadronic decay tagging compositeness/warped ED signatures

improved muon reconstruction (CMS) BSM higgs decays

new beam structure/ detector hardware larger systematic uncertainties (for now)

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SEARCHES SEARCHES

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Resonance searches with Higgs

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• Strategy: exploit ef

efficiency ficiency

– b-tags are powerful (but efficiency falls off at high mX due to b-tag merging) – top backgrounds can remain

Resonance searches in X→ HH

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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

Resonance searches in X→ HH

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Resonance searches with W/Z

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• Look out for 2 TeV…
• Strategy:
• constrain BG to data
• maintain/improve performance
• increase overall acceptance

Increasing acceptance: Z → νν

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fit Z+jet, W+jet, top backgrounds in enriched sidebands * one or two leptons; b-tag

All-hadronic (ATLAS)

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• Same kinematic cuts

as Run 1

• different boson

tagging

– ATLAS maintains cut

• n n(trk) to improve

sensitivity

All-hadronic (CMS)

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check signal efficiencies tight selection

WZ summary (ATLAS)

• ne lepton

monojet all-hadronic

monojet monojet channel adds a str channel adds a strong

• ng

constraint constraint no unusual featur no unusual features es

WZ combination (CMS)

diphoton resonance search

irr irreducible, smooth backgr educible, smooth background

• und

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diphoton resonance search

irr irreducible, smooth backgr educible, smooth background?

• und?

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local local significance @ 750 GeV

ATLAS TLAS CMS CMS

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Testing the γγ excess

Zγ with leptons with leptons Zγ with jets with jets

Testing the γγ excess

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Testing the γγ excess

CMS: similar sensitivity at 750 GeV (leptons only) CMS: similar sensitivity at 750 GeV (leptons only)

di-top

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• ATLAS search in clean semileptonic

channel

• top tag efficiency and rejection

~flat with pT

searches for vector-like quarks

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ATLAS CMS

u ¯ b d Q

Q ¯ Q ¯ t, ¯ b W ±, Z0, H W ⌥, Z0, H t, b

VLQ search overview

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complex: final states simple: VLQ decay

search for heavy TT production

ATLAS: single-lepton channel busy final state: use small radius jets and “reclustered” boson/top jets

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search for heavy TT production

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TT and single-T limits

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Outlook

• Collisions (now-2018)!

Collisions (now-2018)!

– intensity ramp thr intensity ramp through spring

• ugh 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?

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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

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handling high pileup

event-by-event corr event-by-event corrections ections standar standard gr d grooming

• oming

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tracks vs. pileup and boost

42 track-assisted substructure (bonus: simplified uncertainGes) track-based pileup removal

kilometers apart…

CMS CMS

• HVT Model B

– CHM-like: suppressed fermion couplings

• RS model with k/M ~ 0.1

ATLAS TLAS

• HVT Model A

– EGM-like: comparable fermion &vector couplings

• RS model with k/M ~ 1

– higher cross-section, broader resonance

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Higgs strategies

Resolved analysis Resolved analysis Di- Di-higgs higgs signal ef signal efficiency ficiency

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Resonance searches with Higgs

ATLAS searches for WH,ZH with H → bb:

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combination of diboson searches

1512.05099

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aKer combinaGon, local excess significance is strongly reduced: (to 2.6 sigma)

CMS summary

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