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Prospects for New Physics at the LHCAyana T ArceAPS/AAPT MeetingFebruary 13, 2010

atlas

New Physics @ LHC

2

+Outline

New physics at the LHC

Looking for new physics with ATLAS and CMS

The art of the search

Possible discoveries using leptons, jets and lifetimes

Outlook

13 February 2010

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New Physics @ LHC

3New physics (to us)

Abell

22

18

; N

AS

A/S

TSci

Bulle

t;C

hand

ra

TeV-scale: age less than 1 picosecond

(very old physics!)

us

us

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New Physics @ LHC

4

+new physics with the

Large Hadron Collider

gaps up to 3 μs even in 2808x2808 mode

ATLAS

CMS

cosmics,beam halo

3.5 TeV

3.5 TeV

bunches can cross every 25 ns(small fraction filled in early 2010 )

<1 inelastic interaction per crossingexpected in early 2010

13 February 2010

New Physics @ LHC

5

+new physics with the

Large Hadron ColliderHow will the reduced energy for proton beams affect sensitivity?

Quig

g

arX

iv:0

90

8.3

66

0

unfavorable BG scaling

Studies in this talk: 10 and 14 TeV simulation

Bauer

et.

al

arX

iv:0

90

9.5

21

3v2

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New Physics @ LHC

6seeing new physics with

ATLAS and CMS

?

e

Mostly looking for ~stable SM particles from exotic decays

but we might also “see” a dark matter candidate

neutral, invisible, stable missing

transverse momentum (MET)

and we can’t rule out new nearly-stable interacting (or late-

decaying) particles

new = heavy, so slow to arrive at a sensor

ubiquitous: jets (quarks/gluons made

anonymous)

rare: isolated leptons

rare in SM collisions: missing energy

optimize efficiency, ‘fake’ rate, energy resolution for e, Υ, μ, jets

13 February 2010

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New Physics @ LHC

7seeing new physics with

ATLAS and CMS

ATLAS (pixel/strip sensors + straw transition radiation tracker) TRT sensitive toβ(e/π separation)

toroidal µ spectrometer combined ID+ µ: σ(pT )≈5%

(prompt µ from 1-TeV resonance)

CMS: (pixel/strip sensors) solenoidal µ spectrometer

combined tracker+muon pT resolution ≈5% @1 TeV

B=4TR=7.5m

B=2TR=11m

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JIN

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New Physics @ LHC

8seeing new physics with

ATLAS and CMS

LAr + Cu accordion EM calorimeter: σ(E)/E≈1% for 100 GeV e

fine strip granularity (.003 in η) 3 samplings: 4.3,16, 2 X0 in barrel

Fe + scintillating tile hadronic calorimeter: resolution at 1 TeV: 3%

PbWO4 crystal EM calorimeter: σ(E)/E≈0.5% for 120 GeV e

(0.0175)2 η×ϕ granularity

Cu +scintillator hadronic calorimeter: resolution at 1 TeV: 6%

muons

e,γ,jets

Q≠0

3 longitudinal segments

13 February 2010

JIN

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New Physics @ LHC

9The art of the search Tevatron m(squark, gluino) limits: ~300-400 GeV

m( )> 149 GeV if short-lived Z’-like resonances not seen below ~1 TeV Large extra dimensions scale > 1 TeV (N>4)

SM is “unknown” in p+p @7 TeV choose between model+luminosity or

‘sideband extrapolation’ uncertainty

absolute jet calibration: statistics+time (ϒ,Z+jets): uncertainties affect efficiency (degrade

limits) , and background rejection (reduce

significance)

& li

mit

ati

ons

know

your lim

its…

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New Physics @ LHC

10The art of discovery

Data-driven background methods (cf. sideband subtraction)

inclusive searches: greater challenge to prove backgrounds are understood

Beware bias from presence of signal (blunted sensitivity)

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New Physics @ LHC

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Searchesdilepton resonances

tt resonances

extra dimensions

supersymmetry

lifetime signatures

13 February 2010

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New Physics @ LHC

12early probes of new physics:

searching for dilepton pairs

dilepton resonances are generic to many models: GUTs, little Higgs, technicolor, Randall-Sundrum gravitons…

Background : predominantly Drell-Yan top, diboson: ~10% at higher mass

Sensitivity depends strongly on mass resolution

e, μ

e,μ

μe technique

Drell-Yan parameterization

ee: 14 TeV

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New Physics @ LHC

13early probes of new physics:

searching for dilepton pairs

Model width @ 1 TeV

Signal evts

Drell-Yan evts

SSM 30 GeV 16.9 0.11

Phi 6 GeV 4.33 0.60

GRS (c=0.1) 14 GeV 20.7 0.91

GRS (c=0.3) 3.5 GeV 4.87 .0036CMS100pb-1 @ 10 TeV

μμ14 TeV

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New Physics @ LHC

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2&3 TeV

Tags:jet masssecondary vertex tag

kT-like splitting scale

non-isolated muon

understanding the large top mass:

looking for tt resonances

can we explain mT ~ 175 GeV by enhanced couplings (Topcolor Z’; R-S with bulk fermions)?

Challenges: top identification; mass reconstruction with top quarks

escaping neutrinos

jets (heavy flavor)

angular separation decreases with energy

t Wb

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New Physics @ LHC

15understanding the large top mass:

looking for tt resonances

10TeV

CMS semileptonic:~4% signal efficiency @ 1 TeV

CMS all-hadronic ‘double tags’ signal

efficiency 0.34% @ 1 TeV

100pb-1

1 fb-1

ATLAS: strong rejectionfor 2 TeV Z’ search

t Wb

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New Physics @ LHC

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effects of strong gravity at distances ≤ 1/TeV:

black holes or stringballs (democratic decay to a large number of objects per event)

some searches for hidden dimensions:

BH events

Black holes

14 TeV

Cuts: 4 high-pt objects and a lepton

High pT objects (>200 GeV):

pass single jet triggers without prescale

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effects of strong gravity at distances ≤ 1/TeV:

black holes or stringballs (democratic decay to a large number of objects per event)

some searches for hidden dimensions:

BH events

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stringballs

10 TeV

High pT objects (>200 GeV):

pass single jet triggers without prescale

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New Physics @ LHC

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graviton+jet signature: “monojet” collision backgrounds:

invisible Z+jet top/single top: reducible “invisible W,” Wtau

also contaminated by cosmic rays, beam halo

14 TeV

Z/Winvisible background: normalize to Wmuon

some searches for hidden dimensions:

gG events

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New Physics @ LHC

19sparticles and dark matter: inclusive SUSY searches

ttbar-like events

Typically heavy squarks/gluinos

cascade to LSP:

energetic SM particles emitted at each decay

large missing energy from dark matter candidate

600-700 GeV squark/gluino masses accessible with 200 pb-1

Lead jet: 100-180 GeV

~40-50 GeV jets20 GeV leptons

missing E(T):~ 0.3*M(Eff)

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New Physics @ LHC

20sparticles and dark matter:

GMSB signature: nLSP

Photon “tracking” without conversions measure lifetime via displacement + TOF

few cm displacement

~50 GeV photon trigger (or multi- jets)

# photons

CER

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New Physics @ LHC

21other long-lived signatures:

charged massive particle ID charge allows velocity measurement

by time of flight and ionization

signalBG

track

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TRT high-threshold hits

10 TeV

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New Physics @ LHC

22working overtime:

searching for split SUSY R-hadrons can stop in the detector material

Note axis units! Uncertainties: gluino production model

exotic stopping power of CMS LHC operations

Selection BG rate Efficiency

Trigger 5Hz 31%

50 GeV jet 0.02 Hz 20%

Muon veto 0.005 Hz 19%

Cleaning cuts

0.4 mHz 16%

collisions

quiet time

13 February 2010

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New Physics @ LHC

23

+ New (timely!) theory ideas, bigger backgrounds, new

experimental challenges: analyses are maturing before high-energy data arrives

This was a truncated overview: the first discovery may not be in these slides… it may show

up as something entirely unexpected!

Outlook

13 February 2010