Transcript Status of LHC and ATLAS

Физика на больших
детекторах LHC
How to observe new physics at LHC
Alexandre Rozanov
16.01.2011
1
Outlook
•
•
•
•
•
Standard Model at 7 TeV
Higgs
SUSY
New physics from dijets (q*,Black Holes, contact interactions)
new W
2
LHC status
Instant luminosity record 2010 2 10 32 cm-2 s-1
Integrated luminosity today 45 pb-1
Hope to collect at end of 2011 1000 pb-1
3
tt cross section
• ATLAS and CMS measured on small sample tt cross-section compatible with SM
4
Quark-gluon plasma in Pb-Pb collisions
• jet quenching in Pb-Pb collisions
• J/ψ yield
• Z yield
5
Quark-gluon plasma in Pb-Pb collisions
• jet quenching : centrality dependent di-jet asymmetry
• centrality dependent suppression in the normalised J/ψ yield
• no visible effect for Z
6
Spectacular events observed
The first ZZ4µ event
Spectacular events observed
Highest mass dijet: Mjj =3.7 TeV
ET jet1 ~ 670 GeV
ET jet2 ~ 610 GeV
Decisions after Chamonix meeting
• Run in 2011
• 2011 max peak luminosity 1.3-2.0 1033 s-1 cm-2
• Integrated luminosity: 1 fb-1 in 2011 (but
potentiality to get much more)
• Energy 3.5 x 3.5 = 7 TeV in 2011
• Squeeze β*= 1.5 m
• Bunch separation 75 ns or 50 ns
• Number of bunches nb=936-1404
9
Decisions after Chamonix meeting
• Continue run in 2012
• Integrated luminosity: 5 fb-1 in 2012 (but
potentiality to get much more)
• Reconsider 8 TeV for 2012 (depends on the
results of the splice measurements with
“Thermal Amplifier”)
• Longer 2011/2012 Xmas stop for
electrical/ventilation maintenance
10
LHC versus Tevatron
Tevatron ~5-10 fb-1 with √s=1.96 TeV
LHC ~1 fb-1 with √s=7 TeV at end of 2011
LHC advantage – gain in energy 2->7 TeV
LHC temporary disadvantage – loss in luminosity
H->WW at mH=160 GeV LHC gain factor 15 (gg)
Z’ at mZ’=1 TeV LHC gain factor 100 (qq)
11
Higgs
• Higgs production at LHC
SM Higgs branching ratios
Higgs branching ratios
bb

ττ
WW
ZZ
Motivation for low mass Higgs
mH  114.4 GeV/c2 (LEP) et (WW scattering unitarity) mH  1 TeV/c2
2
mH  90 27
22 GeV/c (electroweak fits) mH < 149 GeV at 95% CL
mh < 90 GeV in MSSM without radiative corrections
mh < 130 GeV in MSSM with radiative corrections
Aleph LEP Higgs candidate mH=115 GeV
14
How Higgs →   should looks like
15
First   results in ATLAS
• L = 37 pb-1
16
Projected sensitivity for H→  
• L = 1 fb-1 in 2011
• Possibility to exclude Higgs with mH=110-140 GeV
at 3.2-4.3 σSM 95% CL
17
W H→ bb
• also ZH, ttH
• good b-tagging, better signal when H is boosted
18
qq H→ ττ
• production via Vector boson fusion
• good b-tagging, better signal when H is boosted
19
SM Higgs with mH > 130 GeV
•
•
•
Events observed with
4e, 4 and 2e2 final states
Clear mass peak with S/B >> 1
most sensitive around mH=200 GeV
SM Higgs, H->ZZ->4l
•
•
•
Very clean signature
– Narrow resonance
– Small background contribution
Main experimental issues
– Lepton isolation
• Zbb and ttbb rejection
Good for discovery in wide Higgs mass range
– 130 < MH < 600 GeV
ATLAS
Search for H W W* l  l 
0 jets
1 jets
2 jets
•
•
•
•
•
•
H W W* dominates
need H W W* l  l 
no peak, shape close to background
mT=√((∑Eti)2 - (∑pi)2)
0j – gluon fusion
1j or 2 j – Vector Boson Fusion
SM Higgs with mH = 130-300 GeV
•
•
•
•
•
•
H W W* dominates
need H W W* l  l 
no peak, shape close to background
mT=√((∑Eti)2 - (∑pi)2)
0j – gluon fusion
1j or 2 j – Vector Boson Fusion
Higgs discovery potential 2011-2012
24
Higgs exclusion potential
25
Higgs discovery-exclusion potential
•
•
•
95% CL exclusion is possible in 2011-2012 in the full mass range
3 sigma Higgs observation looks possible in the full mass range in 2011-2012,
especially if optimization of analysis will be done at low mass and partial
running at 8 TeV
5 sigma discovery at low and very high mass Higgs should wait for design
energy and luminosity after 2015
26
MSSM Higgs
•
Minimal super-symmetric extension of Higgs sector
– Five Higgs: h (light), H(CP-even), A(CP-odd), H (heavy)
– Parameter space reduced to two: MA,tanβ (ratio of vev of two Higgs doublets)
– Theoretical limit on light MSSM Higgs: h<135 GeV
A.Rozanov ITEP Winter School of Physics February 2006
27
MSSM Higgs
•
•
Large multiplicity of discovery modes:
– SUSY particles heavy:
• SM-like: h,bb,,WW; H4l
• MSSM-specific: A/H,,tt; Hhh, AZh; H, c s
– SUSY accessible:
• H/A  02 02, 02  h 01
• Small impact on Higgs branching ratio to SM particles
Consider different MSSM scenarios
– Different upper limits to light MSSM Higgs (h)
28
H/A →µµ
• Associated production with b-quarks dominate bbH
• Very clean signature of two muons and b-jets
• Typical branching B=4 10-4 and σ =100 pb for mA/H=150 GeV tanβ=40
• Background Z+jets, tt (leptonical)
29
H/A →cs
•
•
•
•
•
tanβ <1, mH < mt , production tt→bH+ bW
triger by leptonic W decay
signature of lepton, missing ET , two light jets and two b-jets
mH reconstructed from two light jets
Background : semi-leptonic tt
30
H/A →τν
•
•
•
•
•
tanβ > 1, mH < mt , production tt→bH+ bW
triger by leptonic W decay and leptonic τ decay
signature of two opposite charge leptons, missing ET and two b-jets
exploit stronger peaking to -1 of lepton on H side
Background : leptonic tt
31
Early LHC SUSY search
SUSY stabilizes mH  SUSY at TeV scale  spectacular signatures at LHC
• see lecture of D.Kazakov СУСИ расширение
Стандартной Модели
• SUSY best candidate for early discovery
• Gluino ans Squark strongly produced
• QCD comparable cross-section – 100 events/day at
L=1033 and m(gluino)~ 1 TeV
• ETmiss from LSP escaping detection
• High ET jets if unification of gaugino mass assumed
• Spherical events: Tevatron - Mg,q > 400 GeV
• Multiple leptons: decay of charginos/neutralinos
•
•
A typical SUSY event at LHC will contain hard
jets + n leptons and large missing transverse
energy, ET .
The SUSY mass scale:
MSUSY  min(m~g , m~q )
•
The effective Mass gives a handle on the
SUSY mass scale
4
M eff   pTi  ETmiss  M SUSY
i
•
Cuts to reject SM background
– 4 jets with PT > 50GeV
– 2 jets with PT > 100GeV
– ET > max(0.2Meff,100GeV)
– no lepton
Inclusive SUSY
signatures
p
~χ 0
1
~g
q
~
qL
q
~χ 0
2
h,Z
ATLAS
20.6fb−1
SUSY signal (full sim.)
SM background
33
•
Plot MSUSY vs. the peak value of
the Meff (from full simulation).
•
MSUSY vs. Effective
mass
ATLAS
Repeat this for different mSUGRA
models. (Minimal Supergravity
Mediated SUSY breaking)
•
Correlation line from fast
simulation
•
Meff can be used over a broad
range of mSUGRA models.
Meff is a good variable for the estimation of the SUSY mass scale
34
SUSY
q
g~
q~
q
02
Z
01
Backgrounds for ETmiss
• Real ETmiss from neutrino in W, Z+jets,tt
• Instrumental ETmiss from mismeasured multi-jets
(dead/hot cells, non-gaussian tails, gaps in acceptance
etc)
• Reject events with fake ETmiss : beam-gas, displaced
vertexes, hot cells, ETmiss along jets, jets in gaps.
• All detector and machine garbage end up in ETmiss
trigger
Performance of missing ET
• Based on calorimeters and muons
• some cleaning from cosmics and beam backgrounds
37
SUSY search without lepton
•
•
•
•
Direct gluino pairs (A)
Associated gluino-squark (B)
Low mass squark anti-squark (C)
High mass squark anti-squark (D)
event’s maximal lower bound for the mass for either primary
outgoing particle (e.g. squark in the signal) under the
assumption that each decayed to one of the leading two jets in
additionto a source of ~PTmiss (e.g. a neutralino, assumed to
be massless)
38
SUSY search without lepton
ATLAS preliminary
ATLAS preliminary
ATLAS preliminary
ATLAS preliminary
39
mSUGRA limits without lepton
mgluino(mSUGRA) <775 GeV at 95% CL
40
SM background –
1 lepton
p
Signal reduced to 20-40% of no lepton
mode
• S/B better than in 0-lepton mode. Clean
discovery mode
~g
q
~q
L
q
~χ 0
2
• QCD-multijets suppressed with fake
leptons
• tt- dominant, but more predictable
SM cuts+1lepton
~
l
l
~χ 0
1
l
SUSY search with one lepton
•
•
•
•
•
•
•
at least 3 jets pT > 60, 30, 30 GeV
One lepton pT > 20 GeV
mT > 100 GeV
MET/meff > 0.25
meff > 100 GeV
backgrounds W+jets, tt, single top,QCD
Extrapolation from control regions to signal region
• 95% CL limits
• Electron 0.065 pb (2.2 events)
• Muon 0.073 pb (2.5 events)
42
mSUGRA limits with one lepton
mgluino(mSUGRA) <700 GeV at 95% CL
43
Perpectives SUSY in 2011
Cosmologicaly interesting
44
Di-jet event
mj1j2 =1.77 TeV
pT j1= 1.1 TeV
pT j2= 0.48 teV
pT j3= 0.16 TeV
pT j4= 0.10TeV
45
Di-jet resonances
• pT j1> 80 GeV pT j2> 30 GeV
• |ηj1|<2.5 |ηj2|<2.5 |Δη|<1.3
46
Exclusion of the exited quark
• qg-fusion production and dijets
decays
• Λ=mq* compositeness scale
• f=f’= fs=1 coupling parameters
• 95% CL limit
• ATLAS exclude mq* < 2.15 TeV
• CDF exclude mq* < 870 GeV
47
Black Holes At The LHC
If Mpl ~ O(1 TeV)  Black Hole Production possible at LHC
N.Arkani-Hamed, S. Dimopoulos and G.R.Dvali [hep-ph/9803315]
S.Dimopoulos and G. Landsberg [hep-ph/0106295]
 σ ~ πRS2 ~ O(100)pb
 LHC  Black Hole Factory
 BH lifetime ~ 10-27 – 10-25
MBH = √S
Parton
seconds
 Decays with equal probability to
all particles via Hawking
Radiation
MBH~MPL: Study Quantum
Gravity at the LHC
Rs
Parton
Rs = Schwarzschild radius 
2GM BH
c2
Black Holes
 Randall-Meade Quantum Black Hole model
 quantum gravity mass scale MD
 BlackMax black hole
event generator
MD > 3.67 TeV for n = 6
extra dimensions
49
Gravitons
 Gravitons be
produced with a range
of masses at LHC
 Randall-Sundrum
(RS) gravitons
 no limit yet as
expected rate is too low
50
Contact interactions in di-jets
• QDC background: rather forward jets, mainly in t-channel g exchange
• New contact interactions: isotropic widely separated jets
• pT j1 > 60 GeV pT j2 > 30 GeV
• |ηj1|<2.8 |ηj2|<2.8
• rapidity y = 0.5 ln((E+pz)/(E-pz)) , y*=0.5(y1-y2)
• |y1+y2|<1.5
•
•
Fχ = N (|y*| < 0.6) / N (|y*| < 1.7)
η or
Fχ
51
Dijet contact interaction
52
Dijet contact interaction
• Data well described by standard model (QCD Pythia)
53
Dijet contact interaction limit
•
•
•
•
•
qqqq contact interaction
From Fχ ratio mq* > 2.6 TeV at 95% CL
Limit on the scale of contact interaction Λ > 7.9 TeV at 95% CL from Fχ
Preveous limit from Tevatron Λ > 2.0 TeV
54
Search for W’ or W* in ATLAS
• W’ same couplings as in Standard Model, W* - magnetic type couplings
• W’ with mW’ =1 TeV at √s=7TeV expect σ*Acceptance (eνe): ~300fb
• D0 result mW’ < 1 TeV at 95% CL
• e candidate with ET> 20 GeV |η|<2.5
• ETmiss >25 GeV
• mW’ < 1.49 TeV at 95 % CL
• mW* < 1.49 TeV at 95 % CL
55
After 2012
•
Long 19 months shutdown in 2013-2014:
• replace all splices with new clamped and Cu shunted
• add pressure relief valves DN200
• train magnets with lost memory up to 7 TeV
• cryo collimators upgrade-1
• several smaller scale repairs and consolidations (leaks, belows, screens etc)
• 2014 Physics 6.5x6.5 TeV, peak luminosity 1.4 x10 33 cm-2 s-1 , integrated
luminosity of ~8 fb-1
• 2015 Physics 7x7 TeV, peak luminosity 3.0 x10 33 cm-2 s-1 , integrated luminosity of
~24 fb-1
56
HL LHC upgrade
• 2016-2017 : SLHC Phase 1 peak luminosity up to 2 x10 34 cm-2 s-1
•
•
•
•
•
Linac4 (160 MeV, H- ) or earlier 2014???
preparation for new large aperture triplets
radiation tolerant electronics/new shafts for LHC
ATLAS install 4th-pixel layer at R=3.5 cm (probably earlier in 2014), CMS new 4layer pixel system
2021: SLHC Phase 2 peak average luminosity 5.0 x10 34 cm-2 s-1
•
•
•
•
•
•
•
•
luminosity leveling
crab cavities
large aperture triplets
PS consolidation
PSB upgrade (2 GeV injection to PS)
SPS consolidation
ATLAS and CMS install new Inner Detectors
~10 years collecting data, total luminosity 3000 fb-1
57
Conclusions
•
•
•
•
•
•
•
•
•
•
ATLAS and CMS were ready for data at 99% level
World record of 7 TeV collision energy
ATLAS and CMS rediscovered most of the results from Tevatron
Start to be competitive with Tevatron
Collected 45 pb-1 in 2010
Heavy ions in November -December2010 was unexpected success
In 2011 expect at least 1 fb-1 of integrated luminosity at √s =7 TeV
In 2012 expect at least 5 fb-1 of integrated luminosity at √s =7 TeV
or 8 TeV
Looking forward to 2015 to reach design energy 14 TeV and
increase in luminosity
HL LHC upgrade efforts are on the way already
58
SPARES
59
dE/dx in pixel detectors
60
gamma gamma data driven
background
61
Tevatron exclusion
62
Black
Hole
Event
in
ATLAS
BH evaporates into
(q and g : leptons : Z and W :  and G : H) = (72%:11%:8%:6%:2%:1%)
(hadron : lepton) is (5 : 1) accounting for t, W, Z and H decays
S.B. Giddings, S. Thomas, Phys.Rev.D65(2002)056010
gamma
Decay of 6.1 TeV
Black Hole
High multiplicity
events
Muon
Event Multiplicity
Number of Extra
dimensions
2
4
6
64
Reconstructed BH Mass
 BH will be produced with a range of masses at LHC
 Mass reconstruction by Σ P of all decay products
65
Black Holes
 BH will be produced with a range of masses at LHC
66
Multibody final states
•
•
•
•
•
•
Minv of n≥3 high pT objects
pT j et >40 GeV pT e/ >20 GeV pT μ >20 GeV E Tmiss
control region ΣpT > 300 GeV and 300 GeV < Minv < 800 GeV , MC normalized to data
signal region ΣpT > 700 GeV and Minv > 800 GeV
no deviations from Standard Model observed
σ*Acceptance < 0.34 nb at 95% CL
67
Performance of missing ET
• small differences data/MC for events with jets at high pT, smearing jets in
MC to get agreement
• some cleaning from cosmics and beam backgrounds
Calibrated
pT [GeV]
68