Higgs, SUSY and non-SUSY BSM in ATLAS

Higgs, SUSY and non-SUSY BSM in ATLAS

Johannes Haller

(Universität Hamburg/DESY)

on behalf of the ATLAS collaboration

18th International Conference on Supersymmetry and Unification of

Fundamental Interaction August 23-28, 2010

Bonn, Germany

J. Haller Higgs, SUSY and non-SUSY BSM in ATLAS 2

ATLAS DetectorL ~ 46 m, ~ 22 m, 7000 tons~108 electronic channels

Muon Spectrometer: air-core toroids with gas-based muon chambers.trigger and meas. with momentum resolution < 10% up to E ~ 1 TeV

Trigger system: 3-levels reducing the IA rate from 40 MHz to ~200 Hz

Inner Tracker (||<2.5, B=2T): Si Pixels, Si strips, Trans. Rad. Det. Precise tracking and vertexing, e/ separation, momentum resolution: /pT ~ 0.04% pT (GeV) 1.5%

EM calorimeter: Pb-LAr Accordion, e/ trigger, id. and meas., energy res.: /E ~ 10%/E 0.7%

HAD calorimetry (||<5): Fe/scintillator Tiles (cen), Cu/W-LAr (fwd). trigger and meas. of jets and ET,miss, energy res.:/E ~ 50%/E 3%


Reality after ~15 years of preparation

Calorimeters

Muon chambers

Toroid coils

L ~ 46 m, ~ 22 m, 7000 tons~108 electronic channels


LHC status and plans

status: LHC delivers √s=7 TeV pp collisions and ATLAS records them

• int. luminosity so far: ∫Ldt~1.8 pb-1

short term: pp physics till 1. Nov• aim to get to L=1032cm-2s-1

− 432+432 bunches in trains− 10 pb-1/day, ∫Ldt ~ 100 pb-1

• followed by ion run/technical stop (end 2010/start 2011)

mid term: ∫Ldt=1fb-1 by end of 2011• followed by ~year of shutdown (2012)

− repair splices → √s=14 TeV

long term: 10 fb-1 at √s=14TeV by end of 2014

this talk:

•BSM/SUSY physics results with current data set

•example physics prospects with future √s=7 TeV data


The LHC physics landscape

7 TeVLHC detectors are looking for needles in the haystacks

• rare processes hiding in overwhelming background of “bread and butter” physics

• rates at 7 TeV and 1032 cm-2s-1

inelastic pp collision 107 Hz

b-quark pair production 104 Hz

jet production, ET>250 GeV 1 Hz

Wl 1 Hz

t-quark pair production 10-2 Hz

Z’ (m Z’ =1 TeV) 10-4 Hz

Higgs (mH=500 GeV) 10-5Hzintegra

ted lu

mino

sity/time

lumi today: ~1.8 pb-1 (less analysed) • study of SM bgr and detector behavior• starting to enter region with BSM sensitivity

1000 times more expected by end 2011


New Physics in initial running period?

current best competitor: Tevatron• typically ~5fb-1 with √s=1.96 TeV• disadvantage: loss in statistics:

− ∫Ldt=(5-10) fb-1→ ∫Ldt=(0.1-1) fb-1

• advantage: gain in cms energy− √s=2 TeV → √s=7 TeV

gain depends on initial state (gg or qq) and required invariant mass (MX)

• e.g. HWW at 160 GeV, gains factor ~15 (gg dominated)• e.g. 1 TeV Z’ (qq) gains factor ~100

(to be considered in full analysis: signal efficiencies, backgrounds etc.)

WJ Stirling

plenty of potential for new physics surprises even in 2010 run


General ATLAS performance

detector working very well• data taking efficiency > 95%

detector performance → A Belloni

trigger performance• L1 trigger rates scale nicely

• L1 trigger efficiencies for electrons, jets, muon, ET,miss high and steep

Higgs/SUSY/BSM events are read out and recorded efficiently

L1 e trigger efficiency L1 jet trigger efficiency


Search for New Physics in dijet final states

sensitivity to BSM in dijet final states already with small data sets

event distributions of QCD (fwd jets) and BSM (central jets) differ

search for dijet-resonances

event selection: (315 nb-1)

• jet1: pT> 80 GeV; jet2: pT> 30 GeV

• |ηj1|<2.5; |ηj2|<2.5 and |Δη|<1.3

scan mjj spectrum for resonances• resolution: mjj=200 GeV (1TeV): 13 % (6%)

• data described by smooth fit function

• many tests → p-values always > 50% no evidence for a

resonance

QCD (mjj~1TeV) q* (1TeV)

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See talk by Frederik Ruehr



mj1j2 =1.77 TeVpT (j1)= 1120 GeVpT (j2)= 480 GeVpT (j3)= 155 GeVpT (j4)= 95 GeV



95% CL exclusion limits• excited-quark model considered

− IA described by eff. Lagrangian:

− Λ: compositeness scale (here: Λ=mq*)

− f, f’, fs: coupl. parameters (f=f’=fs=1)

− fs≠0: qg-fusion production; dijets decays

excluded: 400 GeV < mq* < 1260 GeV

• compare CDF: 260 GeV < mq* < 870 GeV

[Phys. Rev. D79 112002 (2009)]

first published BSM result from LHC

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event selection (~61nb-1):

search for non-resonant BSM effects at high mjj

study directly the angular distribution of jets

two observables:

New Physics: isotropic,

widely separated jets

QCD: rather forward

jets (t-channel)

• jet1: pT> 60 GeV; jet2: pT> 30 GeV

• |ηj1|<2.8; |ηj2|<2.8;

• |y1+y2|<1.5

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data well described by SM prediction (LO Pythia)

limits in qqqq contact interaction scenario• 95 % CL exclusion limits:

− limit ~ measured mjj range: limit not physical, rather demonstrates current sensitivity− compare with D0: >2.8 TeV [PRL 103:191803,2009]


520 GeV <mjj < 680 GeV

η-ratio: Λ>760 GeVχ-spectrum: Λ>930 GeV

|| 21 yye

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Search in high multiplicity final states at high minv

model independent search in final states with high multiplicity

check: Minv of several (n≥3) high pT objects

• use: central jets (pT>40 GeV), e/ (pT>20 GeV), μ (pT>20 GeV)

• control region: normalization of MC to data− ΣpT > 300 GeV and 300 GeV < Minv < 800 GeV

• signal region: look for deviations − ΣpT > 700 GeV and Minv > 800 GeV

no deviation from SM exclusion limits• upper limit (95%CL) on σ*acc. = 0.34 nb

control region

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signal region


Neutral gauge bosons in ATLAS

many BSM models: new neutral bosons (Z’)• here: SM-like model (SSM)

• current best limit: CDF: mZ’ > 1 TeV (95%CL)

characteristics at the LHC with √s=7TeV• clear signatures : Z’→ l+l- (e or μ)

• σ*acc (ee+μμ): ~120 fb (mZ’=1TeV)

event selection:

• e channel: 2 e cand. with ET> 20 GeV, |η|<2.5

• μ channel: 2 μ cand. with pT >15 GeV, |η|<2.4

• opposite charges

mee and mμμ distribution described by SM

• σZ→ll ~0.96nb, QCD bgr: ~1%

• “observation of SM Z0→ll at LHC”

muon channel

electron channel

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see talk by Kristina Strandberg



ET (e+) = 40 GeVET (e-) = 45 GeVη(e+) = -0.38η(e-) = 0.21mee = 89 GeV

Z→ee candidate recorded on 9th May 2010


for mZ’= 1.0 TeV already with ~100 pb-1 (early 2011)

luminosity needed for …


))/1ln()((2 sbsbsS modified frequentist approach

It is getting interesting soon !

… a Z’ discovery: … an exclusion at 95% CL:

100 pb-1(early 2011): ~1300 GeV 1 fb-1 (end 2011): ~1800 GeV

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Search for heavy charged gauge bosons (W’)

dedicated W’ search in e-channel (317nb-1)

• isolated, central electron candidate with pT>20 GeV

• ET,miss> 25 GeV[AT

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many BSM models: W’

• again: SM-like model (SSM), currently: DØ: mW’ > 1TeV (95% CL)

characteristics at the LHC

• signature: W’→ lνl, crucial: pT reconstr. of energetic leptons

• σ*acc. (eνe): ~300 fb (mW’=1TeV)

no excess at high mT

• main background: SM W production →“observation of SM W± l±ν at LHC”

electron channel


Search for heavy charged gauge bosons (W/W’)

W→eν candidate event recorded on 5th April 2010

ET (e+) = 34 GeVη(e+) = -0.42ET,miss = 26 GeVMT = 57 GeV


Search for heavy charged gauge bosons (W/W’)

))/1ln()((2 sbsbsS

for mW’=1 TeV already with

~10-20 pb-1 (fall this year)

We are rapidly accessing unexplored regions

… a W’ discovery:

20 pb-1(fall 2010): ~1200 GeV

100 pb-1(early 2011): ~1600 GeV 1 fb-1 (end 2011): ~2300 GeV


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95% CL exclusion limit: − 317 nb-1, e-channel only

excluded: mW’ < 465 GeV

• compare to Tevatron: mW’ <1 TeV

• expected (e+μ):


Search for Supersymmetry

production at the LHC: strongly interacting particles

• depending on masses: large cross-sections (αs)

final states at the LHC: model-dependent• in general: long decay chains

− hadronic jets, (b-jets)

− ET,miss (LSP RPC CDM)

− (charged leptons)

• all detector components needed

strategy: inclusive searches• no resonances description of SM bgr in tails crucial

current best mSugra limits: Tevatron:

current LHC dataset: no sensitivity to unexplored regions yet (mSUGRA)

SUSY analyses rather background studies at this stage• loosen cuts → check control regions → compare with background MC →

check SUSY-sensitive variables → for fun: also look into the signal region

pg

Lq 02

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qX

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GeV 390)( GeV, 300 ,GeV 390 ~~~~ gqgq mmmm

compare with SU4, “low mass point” − σ(NLO, Prospino) = 59.9 pb− m(squarks, gluinos) ~ 410-420 GeV

− m0=200 GeV, m1/2=160 GeV,

A0=–400 GeV, tanβ=10 and μ>0


SUSY: data results in “jets + ET,miss”

highest discovery potential: in “jets+ET,miss+0lept” channelSee parallel talk byRenaud Bruneliere

final selection:

• ET,miss>40GeV, ΔΦ(ji, ET,miss)>0.2

• ET,miss/Meff> 0.3-0.2

normalization of LO Pythia MC to data: 2-jet channel after presel

• nice description of ET,miss and Meff (and many more) shapes by MC (QCD)

• signal region: 4 events, expected: 6.6±3 (mainly VB +jets)

pre-selection: (~70nb-1,L1 jet trigger)

• =1, ≥2, ≥3, ≥4 jets with pT>70 (30) GeV two jet channel:three jet channel:

three (four)-jet channel• after pre-selection: QCD bgr reasonably described by MC

• final selection: 0 (1) event in data; expected: 1.9 ± 0.9 (1.0±0.6)

four jet channel:

summary: in all channels agreement between data and MC SM background under control ! (but mSugra signal still too small)

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SUSY: data results in “jets + ET,miss + lepton(s)”

slightly different selection to select sufficient statistics• 70 nb-1, L1 muon or electron trigger

See parallel talk byYousuke Kataoka

one-lepton channel:

• =1 lepton (e or μ) with pT>20 GeV

• ≥two jets with pT>30 GeV

− signal effi for SU4 : ~ 5%

• QCD (Pythia) and W+jets (Alpgen) expectation normalized to data in dedicated control regions

electron channel:

SM background to SUSY searches under control

muon channel: after cut: ET,miss > 30 GeV & mT> 100 GeV :

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SUSY signals typically rich in b quarks• mixing chiral states (tan) small masses of

3rd generation sfermions

b-tagging algorithm: explicitly reconstruct secondary vertices

− decay length significance: L/> 6

− εb-tagging ~ O(50%)

SUSY: data results in “b-jets + ET,miss”See parallel talk by Mark Hodgkinson

data and MB MC

)(/ LL

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MC normalization performed in dedicated control regions:

• 0-lepton channels:− ≥2-j (70,30), ET,miss/√ΣET > 2 √GeV

− region dominated by QCD multijet− good agreement over entire range

• 1-lepton channels:− ≥2-j (70,30), ET,miss/√ΣET > 2 √GeV,

MT<40GeV → non-QCD bgr small


event selection (305 nb-1):

• always: ET,miss/√ΣET > 2 √GeV, at least one b-jet

• channels: “≥2 jets (pT>70, pT>30)”, “2 jets (pT>30,pT> 30) + ≥1 lepton (pT>20)”

SUSY: data results in “b-jets + ET,miss”

1jet + 1b-jet 1μ + 1jet + 1b-jet

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1e + 1jet + 1b-jet

reasonable agreement data – MC

b-tagging promising tool

SM background under control

no sensitivity to mSugra signal yet


SUSY: prospects for the √s=7 TeV run

new sensitivity study for √s=7 TeV• many inclusive channels

example: “ET,miss + 4 jets + 0 lept”

• best discovery reach

• dominant bgr: top, W

discovery reach in mSUGRA plane• expect bgr (from data) uncert. ~50 %

5σ: squarks and gluinos up to ~700 GeV

expect exclusion beyond Tevatron with ~O(10pb-

1)

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SM Higgs: prospects for the √s=7 TeV run

new sensitivity study for √s=7 TeV• cross section (NLO used) scaling from

full simulation studies at 10/14 TeV

• change 14→7 TeV: gg→H: 28%, W+Jets: 48%, ttbar: 18%, WW: 38%

highest production: gg→H• ~10-20x higher than Tevatron

clean signatures: , WW, ZZ

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most prolific channel at intermediate MH

signature: 2 l at high pT and large ET,miss

selection in “H+0jet”, “H+1jet”, “H+2jet”

main background: SM WW production

• qq dominated

• parton luminosities → better S/B compared to Tevatron

• LHC competitive with small data sets

expected 95%CL excluded regions:• first exclusion already with 250 pb-1

• 1fb-1: exclude 145 GeV <MH< 182 GeV

5σ discovery would need ∫Ldt>2.3 fb-1

SM Higgs: H→WW channel (7 TeV, 1fb-1)

number of exp. events after selection:

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SM Higgs: H→ZZ(*) channel (7 TeV, 1fb-1)

“golden channel” important at high MH

clean 4 lepton signature

• narrow minv peak above smooth bgr (irreducible ZZ(*)→4l)

width of the Higgs peak

• MH<220 GeV: detector mass resolution crucial → apply MZ constraint

• MH>220 GeV: detector mass resolution not crucial since ΓH>Γexp

expected exclusion limits (95% CL)• no exclusion possible for any mass

• highest sensitivity at MH~200 GeV

− note: results for large MH depend on ΓH prediction → result only valid in SM

2.5

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SM Higgs: H→ channel (7 TeV, 1fb-1)

channel important at small MH:

• low BR (~0.2%), but robust signal

early data: inclusive analysis strategy

• only discriminating variable: m

backgrounds• irreducible

− crucial: m resolution (~1.1%)

• reducible: -jet, multijets− critical to reach jet rejection O(5000)− π0: high granular ATLAS calorimeter

expected exclusion limit (7 TeV, 1fb-1)

• (σ*BR)95/SM = 4.4 – 5.8

• no exclusion possible, but significantly better than current Tevatron limits (~20)

Born Brem Box

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combination of , ZZ and WW channels• shown mass range: limit dominated by H→WW channel

• low mass region (MH<130 GeV): channel contributes

• high mass (MH>200 GeV): limit exclusively based on H→ZZ

expected 95 % CL excluded region is 135 GeV < MH < 188 GeV

• H→bb and H→channels will help to improve sensitivity in low mass region

SM Higgs: expected combined sensitivity[A

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Conclusion and Outlook

LHC and ATLAS collecting data at √s=7 TeV• remarkable performance of the detector

currently recorded data set: ~1.8 pb-1

• important for background and detector studies

• already now sensitivity in some BSM models− e.g. excited quarks: mq* >1260 GeV

BSM sensitivity will improve rapidly !• ~100 pb-1 by Nov 2010

− SUSY exclusion beyond Tevatron expected: ~10pb-1

• 1fb-1 by end of 2011− e.g. discover Z’ up to 1.6 TeV; W’ up to 2.1 TeV− e.g. discover squarks and gluinos up to ~700 GeV

− SM Higgs exclusion for 135 GeV<mH<188 GeV

The long awaited time of BSM/SUSY/Higgs data analysis at the LHC has just started !



prospects for the √s=7 TeV data period:• new sensitivity study available [ATL-PHYS-PUB-2010-007]

event selection:

• one isolated lepton with pT> 50 GeV and |η|<2.5

• missing transverse energy: ET,miss > 50 GeV

• specific cuts to suppress ttbar and dijet bgr

expected signal and background

electronchannel

muonchannel

MT[TeV]

exp. cross sections after selection:

MT[TeV]



))/1ln()((2 sbsbsS

modified frequentist approach

for mW’=1 TeV already with

~10-20 pb-1 (fall this year)

We are rapidly accessing unexplored regions

prospects with √s=7 TeV data

… a W’ discovery: … an exclusion at 95% CL:

20 pb-1(fall 2010): ~1200 GeV100 pb-1(early 2011): ~1600 GeV 1 fb-1 (end 2011): ~2300 GeV


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Search for heavy neutral gauge bosons (Z’)

current statistics too low What can we expect?• new sensitivity study performed for √s=7 TeV

event selection:

• two isolated leptons with pT>20 GeV and |η|<2.5

• skip requirement of opposite charges at beginning

expected signal and background:

• very clean signal: ~60 (6) fb for mZ’ = 1.0 (1.5) TeV

• small background (%-level) from Drell-Yan and ttbar.

exp. cross sections after sel.[fb]:

electron channel muon

channel

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SM Higgs: current situation

SM: Higgs needed for EWSB• EW precision data

− (Gfitter)

• exclusion from direct searches:− LEP : − Tevatron:

GeV2.84 3.303.23

HM

GeV 4.114HM

GeV 175GeV 158 HM

ICHEP 2010

prospects for Higgs evidence at Tevatron:

• end 2011:>2.4 σ for all MH

3σ for MH=115 GeV

• run III proposal:>3σ for MH< 185 GeV

4σ for MH =115 GeV

10 fb-1, end of 2011

16 fb-1, run III proposal

Documents

Higgs, SUSY and non-SUSY BSM in ATLAS