BSM at the LHC
Dirk Zerwas
LAL Orsay
• Lecture I:
• LHC and the Detectors
• Standard Model
• Lecture II:
• The standard model Higgs boson
• The supersymmetric Higgs bosons
• Lecture III:
• Supersymmetry
• Exotics
LHC
LHC
• proton-proton collisions
ILC • E
beam=7TeV
• s = 14TeV
• 0.15-20*s effective
• tunnel circumference: ~27km
2 Multi-purpose detectors:
ATLAS, CMS
B-Physics: LHCb
Heavy-ion physics: ALICE
Totem
LHC
R=p/(B q c)
B=8-9T
supraconducting
P=7TeV
c=3*108m/s
R=2.7km
LHC: 4.3km
Straight sections
ALL Dipoles
installed
1600 superconducting magnets….
Preparations started in 1990…
Installation started in 2001…
standard refrigerator: 276K
LHC: a 27 km fridge at 1.9K
37000 tons of equipment
1 year of cooldown
120 tons of Helium (1 truckload=5t)!
• energy in beams: a Boeing 737 at landing speed
• 60 kg of TNT (beam dump)
LHC: 2008/2009
Stage I
2008
Hardware
commissioning
5TeV
Machine
checkout
5TeV
No
beam
Beam
commissioning
5TeV
II
43 bunch
operatio
n
75ns ops
III
25ns ops I
Shutdown
Beam
We are here
III
2009
Shutdown
No
beam
Machine
checkout
7TeV
Beam
setup
25ns ops I
Shutdown
Beam
2008:
• Goal 5TeV (Magnets)
• 43/156 bunches per beam (of 2800)
• 75ns (13.3MHz)
• 25ns (nominal: 40MHz)
LHC: integrated Luminosity
kb
N
* 1,5
(m)
IBeam
proton
Luminosity
(cm-2s-1)
Events/
BC
43
4 1010
11
1.7 1012
7 1028
<< 1
156
9 1010
2
1.4 1013
1.1 1032
3.9
2808
5 1010
0.55
1.4
1014 of nominal
1.9 1033
~ 45%
I
3.6
Evolution of beam levels and luminosity
180
2.50E+33
43/156 Bunches
60
Stage III
0.55m, 25ns, 5 10
1.00E+33
25ns PhaseI
End 2008
40
1.50E+33
Luminosity
10
1m, 25ns, 5 10
10
75ns
2007/2008
10
10
L=1032cm-2s-1
1fb-1 p.a.
L=1033cm-2s-1
10fb-1 p.a.
2.00E+33
1m, 75ns, 9 10
2m, 75ns, 6 10 10
10
2m, 75ns, 4 10
11m, 75ns, 4 10 10
10
2m, 156 bunch, 9 10
2m, 156 bunch, 4 10 10
2m, 43 bunch, 4 10 10
80
11m, 43 bunch, 4 10
10
~ 25% of nominal I
100
Luminosity
Stage II
140
120
Event pileup
11m, 25ns, 4 10
12
• bunch 1011 protons
• every 8m
• 40Mhz
• reality ~ 32MHz
(empty bunches)
Stage I
160
Intensity(10 ), stored energy(MJ), event pileupx10
L: luminosity
N=σ∫Ldt
t typically 107s
Stored energy
2m, 25ns, 4 10 10
Beam intensity
5.00E+32
20
1.00E+32
0
0.00E+00
1
2
3
4
5
6
7
Operational phase
8
9
10
11
12
LHC: comparison to other Machines
(L=1034,
1011
Beam
1.1x
p/bunch)
• 60 kg TNT
• fully loaded Airbus 320 at landing speed
Rule of thumb:
• around 2010 ~10fb-1 p.a.
• well after 2010 ~100fb-1 p.a.
ATLAS and CMS
Length: 45m
Radius: 12m
Weight: 7000Tonnen
Readout Channels: 108
3000km cables
Track reconstruction (|η|<2.5, B=4T)
• Si Pixels and Strips
Calorimeter (|η|<5)
• EM: PbWO4 2%/E0.7%
• HAD: Brass/Scint., Fe/Quartz (fwd)
Muon chambers (|η|<2.7):
• Solenoid Return Yoke instrumented with
Muon chambers
Length: 22m
Radius: 7m
Weight: 12500Tonnen
Track Reconstruction (|η|<2.5, B=2T)
• Si Pixels and Strips
• Detector for Transition Radiation (TRT) for PID
Calorimeter (|η|<5)
• EM: Pb-LArgon 10%/E0.7%, long. Segm.
• HAD: Fe/Scintillator (central), Cu-W-Lar (fwd)
Muon chambers (|η|<2.7):
• Toroids with Muon chambers (MDT)
CMS = Compact Muon Solenoid
Length: 22m
Radius: 7m
Weight: 12500 tons
Length: 45m
Radius: 12m
Weight: 7000tons = 100 Boeing 747
Readout channels: 100Million
3000 km cables
ATLAS= A Toroidal Lhc ApparatuS
building 40
at CERN
6 stories
Event reconstruction
Muons: InnerDetector and
muon detectors
Electrons/photons: EM Calorimeter
Jets: Calorimeters
Tracks: InnerDetector
(with lifetime information
for b-tagging)
Electrons and Photons:
Before Physics: Calibration
Events per Second 1033 cm-2s-1
108
107
105
Events for 10fb-1:
W eν, μν
Z  ee, μμ, ττ
tt
Jets (>200GeV pT)
150
je 15
8
1000
M
M
M
M
Trigger
103
10
10-1
10-3
JES: 1%
LES: 0.1%
ETmiss: (0.5-1)/ET
Calibration and Alignment of the detectors:
Electronic Calibration
In situ Calibration and Alignment:
• Zee, Z μμ : Alignment, Calibration ECAL (Z mass),
Particle-ID, muon chambers
• W lν : Energy/Momentum Calorimeter/Tracker
• tt  bWbW  blν bjj : Reconstruction W from hadronic
decay
• Z  ττ: tau-Lepton Reconstruction (Z mass, Efficiency),
ETmiss
• γ+Jets, Z(ll) +Jets: Jet Calibration (Recoil against Z,γ)
Particle Reconstruction: electrons/photons
The reconstruction sequence for electrons and photons:
• Calibration of Electronics and Alignment
• Clustering (Sliding Window)
• Corrections at the cluster level:
• position corrections
• correction of local response variations
• corrections for losses in upstream
(Inner detector) material and longitudinal leakage
• Matching with Tracks
• Identification
• 2nd stage reco:
• Refinement of corrections depending on the particle type (e/γ)
• Bremfit/Gaussian Sum Filter
• uniformity 0.7% with a local uniformity
in ΔηXΔφ=0.2x0.4 better than 0.5%
• inter-calibrate region with Zee
Energy calibration for electrons and photons
Optimize Energy resolution AND linearity!
100GeV
Systematics at low energy ~0.1 %
Testbeam: Achieved better than 0.1 % over
20-180 GeV
0.1%-0.2% spread from 10GeV to 1TeV over all eta!
Essential to mesure particle masses correctly with the best precision
Vis
Vis
E rec  (a( E )  b( E ).EPS
 c( E )( EPS
.E1vis ) 0.5  d ( E ).i 1,3 Eicalo ).(1  f leak (depth)). f brem ( E ). f cell impact
E loss upstream of PS
E loss
PS and calo
calo sampling
fraction+ lateral
leakage E dependent
Longitudinal
leakage
Uniformity and Identification
rms
0.62%
0.45%
0.49%
Uniformity: ensure same energy response
 Higgs (later)
Identification: differentiate electrons from jets
 Large QCD cross section
Jets and ETmiss
Calibration e/pi response
Jet clustering
Jet resolution: 60%/E  3%
Jet energy scale: 1%
ETmiss
Typical signature of SUSY
compensation for dead matter etc
ETMiss at 2000GeV:
ATLAS σ=20GeV
CMS σ=40GeV
Trigger@LHC
Trigger@LHC: Example of a typical menu
Luminosity Measurements at the LHC
100fb-1  25 interactions per beam crossing
Instantaneous luminosity decreases with beam lifetime
Integrated Luminosity: N = σ * L (every rate/Xsection measurement depends on it)
1.Online measure events in 3<|η|<5
Counting zero ET towers (ET<0.5GeV):
2. Measure elastic cross section at small angles
TOTEM at 150m, 200m
Use optical theorem to relate total Xsection
to elastic cross section extrapolated to 0
Measurements done at 1028cm-2s-1
Extrapolation of beam optics necessary
Precision on σtot ~1%
Deviation at High Luminosity
3.Standard Candles:
W production: 300Hz
Z production: 30Hz (PDF uncertainty)
Minimum Bias
A glossary:
Minimum Bias: Trigger thresholds “minimal”,
measures the total Xsection
Underlying event:= “rest” when subtracting
“hard process”, e.g. production Z
Minimum Bias: Large uncertainties
for the extrapolation from TeVatron
to LHC
Parton collisions (ex quark):
1 1
  s
2 3
1  E  pz 

yW  ln 
2  E  pz 
Pseudo-rapidity:
-ln (tan θ/2)
(polar angle)
Masses neglected
x1, 2 
MW
exp  yW 
s
MRST2002-NLO
LHC
4
(nb)
Rapidity:
5
dW/dyW . Bl
s 
x1 = 0.12
x2 = 0.0003
x1 = 0.006
x2 = 0.006
x1 = 0.0003
x2 = 0.12
3
2
W±
1
0
-6
-4
-2
0
yW
2
4
6
Q2: square of momentum transfer
Standard Model: W production
x: fraction of proton momentum
gluon pdf
The LHC is a gluon-collider!
Standard Model: QCD
CMS
Jet-Production
• with 10fb-1
• compare with NLO
BUT:
• E-Calibration
• prediction for PT >1TeV
CMS
large errors
above 1TeV
• energy scale
• PDFs
The Standard Model: W Mass
Sensitivity to mW (leptonic decays, hadronic case hopeless)
The Standard Model: W Mass
10fb-1
Selection:
PT(lepton)>25GeV
ETmiss> 25GeV
Jet Veto PT>30GeV
Statistics
15
Tot. Exp.
<20
Scale Method:
Treat Z as W and shift spectra
muon
electron
BSM: Di-boson Production
TripleGaugeCouplings (TGC):
WW+γ ou WZ(ll)
300fb for PT(γ)>100GeV
Selection:
• PT(γ)>100GeV
• PT(Lepton)>40GeV
• mT>35GeV
• isolation of Photon and Lepton
• Jet Veto
Wγ frame
W rest frame
λγ=0.01
D0 (2005) (162pb-1):
-0.93<Δκγ<0.97
|λγ|<0.22
LEP:
g1Z=0.984±0.02
κγ=0.973±0.045
λγ=-0.028 ±0.021
The top quark
Indirect sensitivity to the Higgs boson mass
TeVatron 2008: 172.4 ± 1.2 GeV (0.7%)
Production and decay of top quarks
g
t
q
t
t
q
t
g
g
au Tevatron:
10%
90%
au LHC:
90%
10%
Decay (before hadronization):
• short lifetime : top ~ 410-25 s
• decay channels:
– t  W+b because mtop > MW
– with W+  e+e, + (, +)
– or:
– W+  ud, us, cs
σLHC = 833 pb = 100σTeV
Final states (classified according to W
decays, excluding taus):
• fully leptonic channel 5%
450000evts/year low bg
• semi-leptonic channel 30%
2,700,000evts/year good sg/bg
• fully hadronic channel 44%
4,000,000evts/year large bg QCD
ttb+jjb in ATLAS
muon
Hadronic jets
Missing energy
Hadronic jet
Measurement of the top quark mass: semi-leptonic channel
σ = 7.4 GeV
Nbtag = 2
•
•
Reconstruct the W bosons
– select (jj) minimizing |mjj – mW|
– W purity: 66%
– efficiency : ~80%
Light jet calibration of W
– Energy calibration 1-2%
Measurement of the top quark mass: semi-leptonic channel
•
•
•
Reconstruction of hadronic top quark top
– association of b jets with W boson:
– largest pTtop
– maximize ∆R(l,b)
– minimize ∆R(b,Wjj)
 purity top : 69%
 efficiency : 1.2%
Number of events
• ~30K (80K) events in 2 b-tag (≥1b-tag)
• physics background ~ 100 events !
resolution : σ ≈ 11 GeV
σ = 10.6 GeV
Measurement of the top quark mass
•
•
fully hadronic channel:
– 6 central jets (high pT) 2 b
– ~ 100,000 evts in 10 fb-1
combinations and selections:
– W jj (2W)
– t Wb (2t)
– 130 < |mjjb| < 200
– pTtop ≥ 200 GeV/c
– resolution 13 GeV/c^2
– S/B: 18/1
Δm (GeV)
t
 fully leptonic performance with 10 fb-1
– Evt/evt: mt  solve system  weight
– all evts: mean weight per m
– mtfit = mt w/ highest <weight>
 σ ≈ 13 GeV/c2
δmt
light jet energy scale
0.8
b-jet energy scale
0.7
Initial State Radiation
0.4
b-jet energy scale (1%)
0.6
Final State Radiation
2.8
b-quark fragmentation
0.7
b-quark fragmentation
0.3
ISR / FSR modeling
0.6
Background
0.4
Parton Distr. function
1.2
Total SYSTEMATIC
3.1
Total SYSTEMATIC
1.6
Total STATISTICAL
0.2
STATISTICS & method
0.3
W Polarisation and the Wtb coupling
•
Polarisation of the W boson in top decays: search for deviations from the standard model
– Decay t W+b
– 3 helicity states possible for a W boson: -1,0,+1
“Left”
“Longitudinal”
W
b
W
t
t
W
FL=mt2/(mt2+2mW2)
= 0.703

“Right”
lepton: sign and direction wrt W
reco of decay angle possible
t
b
b
F0=2mW2/(mt2+2mW2)
= 0.297
FR= 0.00
= 0.00
(standard model: f1L = Vtb1 , f1R = f2L = f2R=0)
L
g
W b  ( f1L PL  f1R PR )t 
2
g
 W b  ( f 2L PL  f 2R PR )t h.c.
2
Coupling
Determine FL, F0, FR and translate to fiL,R
Limit 2
(statsyst)
f1R
0.31
f 2L
0.14
f 2R
0.07
The final standard model topic: single top production
mecanisms:
t channel
NLO= 231± 9 pb
•
s channel
NLO= 10.1 ± 0.7 pb
Backgrounds: tt, W+jets, QCD-jets
Clear signal
W+t channel
LO= 60 ± 15 pb