Higgs, SUSY and non-SUSY BSM in ATLAS
-
Upload
rajah-salinas -
Category
Documents
-
view
37 -
download
1
description
Transcript of 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%
J. Haller Higgs, SUSY and non-SUSY BSM in ATLAS 3
Reality after ~15 years of preparation
Calorimeters
Muon chambers
Toroid coils
L ~ 46 m, ~ 22 m, 7000 tons~108 electronic channels
J. Haller Higgs, SUSY and non-SUSY BSM in ATLAS 4
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
J. Haller Higgs, SUSY and non-SUSY BSM in ATLAS 5
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
J. Haller Higgs, SUSY and non-SUSY BSM in ATLAS 6
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
J. Haller Higgs, SUSY and non-SUSY BSM in ATLAS 7
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
J. Haller Higgs, SUSY and non-SUSY BSM in ATLAS 8
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)
[su
bm.
to P
RL,
arX
iv:1
008:
246
1]
See talk by Frederik Ruehr
J. Haller Higgs, SUSY and non-SUSY BSM in ATLAS 9
Search for New Physics in dijet final states
mj1j2 =1.77 TeVpT (j1)= 1120 GeVpT (j2)= 480 GeVpT (j3)= 155 GeVpT (j4)= 95 GeV
J. Haller Higgs, SUSY and non-SUSY BSM in ATLAS 10
Search for New Physics in dijet final states
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
[su
bm.
to P
RL,
arX
iv:1
008:
246
1]
J. Haller Higgs, SUSY and non-SUSY BSM in ATLAS 11
Search for New Physics in dijet final states
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
[AT
LA
S-C
ON
F-2
010
-074
]
J. Haller Higgs, SUSY and non-SUSY BSM in ATLAS 12
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]
Search for New Physics in dijet final states
520 GeV <mjj < 680 GeV
η-ratio: Λ>760 GeVχ-spectrum: Λ>930 GeV
|| 21 yye
[AT
LA
S-C
ON
F-2
010
-074
]
J. Haller Higgs, SUSY and non-SUSY BSM in ATLAS 13
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
[AT
LA
S-C
ON
F-2
010
-088
]
signal region
J. Haller Higgs, SUSY and non-SUSY BSM in ATLAS 14
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
[AT
LA
S-C
ON
F-2
010
-076
]
see talk by Kristina Strandberg
J. Haller Higgs, SUSY and non-SUSY BSM in ATLAS 15
Neutral gauge bosons in ATLAS
ET (e+) = 40 GeVET (e-) = 45 GeVη(e+) = -0.38η(e-) = 0.21mee = 89 GeV
Z→ee candidate recorded on 9th May 2010
J. Haller Higgs, SUSY and non-SUSY BSM in ATLAS 16
for mZ’= 1.0 TeV already with ~100 pb-1 (early 2011)
luminosity needed for …
Neutral gauge bosons in ATLAS
))/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
[AT
L-P
HY
S-P
UB
-201
0-00
7]
J. Haller Higgs, SUSY and non-SUSY BSM in ATLAS 17
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
LA
S-C
ON
F-2
010
-089
]
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
J. Haller Higgs, SUSY and non-SUSY BSM in ATLAS 18
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
J. Haller Higgs, SUSY and non-SUSY BSM in ATLAS 19
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
luminosity needed for …
[AT
LA
S-C
ON
F-2
010
-089
, A
TL-
PH
YS
-PU
B-2
010-
007
]
95% CL exclusion limit: − 317 nb-1, e-channel only
excluded: mW’ < 465 GeV
• compare to Tevatron: mW’ <1 TeV
• expected (e+μ):
J. Haller Higgs, SUSY and non-SUSY BSM in ATLAS 20
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
R
01
qX
g
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
J. Haller Higgs, SUSY and non-SUSY BSM in ATLAS 21
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)
[AT
LA
S-C
ON
F-2
010
-065
]
J. Haller Higgs, SUSY and non-SUSY BSM in ATLAS 22
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 :
[AT
LA
S-C
ON
F-2
010
-066
]
J. Haller Higgs, SUSY and non-SUSY BSM in ATLAS 23
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
[AT
LA
S-C
ON
F-2
010
-042
, A
TLA
S-C
ON
F-2
010-
079]
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
J. Haller Higgs, SUSY and non-SUSY BSM in ATLAS 24
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
[AT
LA
S-C
ON
F-2
010
-079
]
1e + 1jet + 1b-jet
reasonable agreement data – MC
b-tagging promising tool
SM background under control
no sensitivity to mSugra signal yet
J. Haller Higgs, SUSY and non-SUSY BSM in ATLAS 25
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)
[AT
L-P
HY
S-P
UB
-201
0-01
0]
J. Haller Higgs, SUSY and non-SUSY BSM in ATLAS 26
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
[AT
L-P
HY
S-P
UB
-201
0-00
9]
J. Haller Higgs, SUSY and non-SUSY BSM in ATLAS 27
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:
[AT
L-P
HY
S-P
UB
-201
0-00
9]
J. Haller Higgs, SUSY and non-SUSY BSM in ATLAS 28
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
[AT
L-P
HY
S-P
UB
-201
0-00
9]
J. Haller Higgs, SUSY and non-SUSY BSM in ATLAS 29
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
[AT
L-P
HY
S-P
UB
-201
0-00
9]
J. Haller Higgs, SUSY and non-SUSY BSM in ATLAS 30
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
TL
-PH
YS
-PU
B-2
010-
009]
J. Haller Higgs, SUSY and non-SUSY BSM in ATLAS 31
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 !
J. Haller Higgs, SUSY and non-SUSY BSM in ATLAS 32
Search for heavy charged gauge bosons (W’)
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]
J. Haller Higgs, SUSY and non-SUSY BSM in ATLAS 33
Search for heavy charged gauge bosons (W’)
))/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
luminosity needed for …
[AT
L-P
HY
S-P
UB
-201
0-00
7]
J. Haller Higgs, SUSY and non-SUSY BSM in ATLAS 34
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
[AT
L-P
HY
S-P
UB
-201
0-00
7]
J. Haller Higgs, SUSY and non-SUSY BSM in ATLAS 35
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