Physics with first data in ATLAS at the LHC
Frédéric Derue
Laboratoire de Physique Nucléaire et de Hautes Energies de Paris,
IN2P3-CNRS et Université Pierre et Marie Curie-Paris6
et Université Denis Diderot-Paris7
Reunión de Física de Altas Energias, FAE06
11-13 de Diciembre de 2006
Caracas
1. Status of the LHC
2. The ATLAS detector
3. Towards physics
4. Physics with first data
5. Conclusion
FAE06, Caracas, Dec 11th 2006
Physics with first data in ATLAS at the LHC – F. Derue (LPNHE Paris)
1
The Large Hadron Collider at CERN
LHC
• pp
s = 14 TeV
• Heavy ions
Ldesign = 1034 cm-2 s-1
(after 2009)
Linitial  few x 1033 cm-2 s-1 (until 2009)
(e.g. Pb-Pb at s ~ 1000 TeV)
TOTEM (integrated with CMS):
pp, cross-section, diffractive physics
ATLAS and CMS :
general purpose
TOTEM
27 km LEP ring
1232 superconducting
dipoles B=8.3 T
ALICE :
ion-ion,
p-ion
LHCb :
pp, B-physics, CP-violation
FAE06, Caracas, Dec 11th 2006
Physics with first data in ATLAS at the LHC – F. Derue (LPNHE Paris)
2
Status of the machine and schedule
Revised LHC schedule (cf. CERN council on 23 June 2006)
last magnet installed : March 2007
machine and experiments closed : 31 August 2007
first collisions (s=900 GeV, L~1029 cm-2 s-1) : November 2007
commissioning run at injection energy until end 2007, then shutdown (3 months ?)
first collisions at s=14 TeV (followed by first physics run) : spring 2008
goal: deliver integrated luminosity of few fb-1 by end 2008
LHC commissioning
sectors 7-8 and 8-1 will be fully commissioned up to 7 TeV in 2006-2007
If other sectors are commissioned up to 7 TeV no beam will circulate in 2007
the other sectors will be commissioned up to the field needed for de-Gaussing
initial operation will be at 900 GeV (CM) with a static machine (no ramp, no squeeze)
to debug machine and detectors
full commissioning up to 7 TeV will be done in the winter 2008 shutdown
FAE06, Caracas, Dec 11th 2006
Physics with first data in ATLAS at the LHC – F. Derue (LPNHE Paris)
3
The ATLAS collaboration
(As of the September 2006)
35 Countries
161 Institutions
1830 Scientific Authors total
(1470 with a PhD, for M&O share)
Albany, Alberta, NIKHEF Amsterdam, Ankara, LAPP Annecy, Argonne NL, Arizona, UT Arlington, Athens, NTU Athens, Baku,
IFAE Barcelona, Belgrade, Bergen, Berkeley LBL and UC, HU Berlin, Bern, Birmingham, Bologna, Bonn, Boston, Brandeis,
Bratislava/SAS Kosice, Brookhaven NL, Buenos Aires, Bucharest, Cambridge, Carleton, Casablanca/Rabat, CERN, Chinese
Cluster, Chicago, Clermont-Ferrand, Columbia, NBI Copenhagen, Cosenza, AGH UST Cracow, IFJ PAN Cracow, DESY,
Dortmund, TU Dresden, JINR Dubna, Duke, Frascati, Freiburg, Geneva, Genoa, Giessen, Glasgow, LPSC Grenoble, Technion Haifa,
Hampton,Harvard, Heidelberg, Hiroshima, Hiroshima IT, Indiana, Innsbruck, Iowa SU, Irvine UC, Istanbul Bogazici, KEK, Kobe, Kyoto,
Kyoto UE,Lancaster, UN La Plata, Lecce, Lisbon LIP, Liverpool, Ljubljana, QMW London, RHBNC London, UC London, Lund, UA Madrid,
Mainz, Manchester, Mannheim, CPPM Marseille, Massachusetts, MIT, Melbourne, Michigan, Michigan SU, Milano, Minsk NAS, Minsk
NCPHEP, Montreal, McGill Montreal, FIAN Moscow, ITEP Moscow, MEPhI Moscow, MSU Moscow, Munich LMU,
MPI Munich, Nagasaki IAS, Naples, New Mexico, New York, Nijmegen, BINP Novosibirsk, Ohio SU, Okayama, Oklahoma,
Oklahoma SU, Oregon, LAL Orsay, Osaka, Oslo, Oxford, Paris VI and VII, Pavia, Pennsylvania, Pisa, Pittsburgh, CAS Prague,
CU Prague, TU Prague, IHEP Protvino, Ritsumeikan, UFRJ Rio de Janeiro, Rochester, Rome I, Rome II, Rome III,
Rutherford Appleton Laboratory, DAPNIA Saclay, Santa Cruz UC, Sheffield, Shinshu, Siegen, Simon Fraser Burnaby, SLAC,
Southern Methodist Dallas, NPI Petersburg, Stockholm, KTH Stockholm, Stony Brook, Sydney, AS Taipei, Tbilisi, Tel Aviv,
Thessaloniki, Tokyo ICEPP, Tokyo MU, Toronto, TRIUMF, Tsukuba, Tufts, Udine, Uppsala, Urbana UI, Valencia, UBC
Vancouver, Victoria, Washington, Weizmann Rehovot, Wisconsin, Wuppertal, Yale, Yerevan
FAE06, Caracas, Dec 11th 2006
Physics with first data in ATLAS at the LHC – F. Derue (LPNHE Paris)
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How huge is ATLAS ?
Size of collaboration
ATLAS superimposed to
the 5 floors of building 40 in CERN
35 countries
161 institutions
1830 scientific authors (1470 with PhD for M&O share)
Size of detectors
volume : 20 000 m3
weight : 7000 tons
~80 million pixel readout channels near vertex
175 000 readout channels for the liquid argon electromagnetic calorimeter
1 million channels and 10 000 m2 area of muon chambers
very selective trigger/DAQ system (online rate reduction > 105)
large scale offline software and worldwide computing (GRID) share)
Time scale will have been about 25 years from first conceptual studies
(Lausanne 1984) to solid physics results confirming that LHC will have
taken over the high-energy frontier from Tevatron (Chicago) (early 2009 ?)
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Physics with first data in ATLAS at the LHC – F. Derue (LPNHE Paris)
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The ATLAS detector
Length : ~ 46 m
1800
physicists
Diametre : ~ 25 m
Muon spectrometer (|h|<2.7) :
air-core toroids
Muon spectrometer (|h|<2.7) :
with muon chambers
air-core toroids
with muon chambers
Weight
: ~ 7000 tons
~108 electronic channels
~3000 km of cables
Cost
: ~ 340 M€ / 10 y
y


x
Calorimeters (|h|<5)
(|h|<5) ::
Tracking system (|h|<2.5, B=2T): Calorimeters
Tracking
system
(|h|<2.5, B=2T): --- EM
EM :: Pb-LAr
Pb-LAr with
with
-- Si pixels
and strips
accordion
shape
-Si
pixels
and
strips
accordion shape
-- Transition radiation Detector
--- Transition
radiation
Detector
-- HAD:
HAD: Fe/scintillator
Fe/scintillator (central),
(central),
(e/p separation)
Cu/W-LAr
(e/p separation)
Cu/W-LAr (fwd)
(fwd)
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Physics with first data in ATLAS at the LHC – F. Derue (LPNHE Paris)
z
 2
h ln tan
Transverse plane projected physical
quantities are measured:
- pT
- ET, ETmiss
6
The underground cavern at pit-1 for the ATLAS detector
(Across the street from the CERN main entrance)
Length
Width
Height
Deep
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= 55 m
= 32 m
= 35 m
= 90 m
Physics with first data in ATLAS at the LHC – F. Derue (LPNHE Paris)
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Generic features required of ATLAS
Detectors must survive for ten years or so of operation
Radiation damage to materials and electronics component
Problem pervades whole experimental area (neutrons) : NEW !
Detectors must provide precise timing and be as fast as feasible
25 ns is the time interval to consider : NEW !
Detectors must have excellent spatial granularity
Need to minimise pile-up effects : NEW !
Detectors must identify extremely rare events, mostly in real time
Lepton identification above huge QCD background (e.g electron/jet ratio
at the LHC is ~10-5, i.e factor 50 worse than at Tevatron)
Signal cross-sections as low as 10-14 of total cross-section : NEW !
Online rejection to be achieved is ~107 : NEW !
Store huge data volumes to disk/tape
(~109 events of 1 Mbyte size per year) : NEW !
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Physics with first data in ATLAS at the LHC – F. Derue (LPNHE Paris)
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Generic features required of ATLAS
Detectors must measure and identify according to certain specificities
tracking and vertexing : ttH with Hbb
electromagnetic calorimetry : H and HZZ eeee
muon spectrometer HZZ mmmm
missing transverse energy : supersymmetry
Detectors must please
collaboration : physics optimisation, technology choices
funding agencies : affordable cost (originally set to 475 MCHF per experiment)
young physicist who will provide the main thrust to the scientific output
of the collaborations : how to minimise formal aspects ?
How to recognise individual contributions ?
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Physics with first data in ATLAS at the LHC – F. Derue (LPNHE Paris)
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Tracking of charged particles : the Inner Detector
The inner detector is organized into three sub-systems
pixels (0.8108 channels)
silicon tracker (SCT) 6106 channels
transition radiation tracker (TRT) 4105 channels
Three completed Pixel disks
(one end-cap) with 6.6 M channels
TRT
SCT
Magnet system
solenoid integrated with the LAr cryostat
2T field with a stored energy of 38 MJ
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Physics with first data in ATLAS at the LHC – F. Derue (LPNHE Paris)
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Tracking of charged particles : reconstruction
At high luminosity per bunch crossing (25 ns)
more than 200 tracks
about 15-20 vertex candidates
Lint/y (fb-1)
L (cm2/s)
s (TeV)
Minimum
bias/bco
LHC ( low L)
10
2x1033
14
5
LHC (high L)
100
1034
14
25
Complex task for tracking and Vertexing because of pile-up.
Triggering algorithms have to be fast and robust to avoid to miss rare events
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Physics with first data in ATLAS at the LHC – F. Derue (LPNHE Paris)
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Electron/ : the electromagnetic calorimeter
The electromagnetic calorimeter
EM barrel : (|n|<1.475) [Pb-LAr]
EM end-caps : (1.4<|n|<3.2) [Pb-LAr]
lead/Liquid argon sampling calorimeter
with accordion shape
Physics requirements
discovery potential of Higgs (into  or 4e)
determines most of the requirements
largest possible acceptance (accordion)
large dynamic range from 20 MeV to 2 TeV
energy resolution sE/E~10%/E0.7%
linearity ~0.1% (W-mass precision measurement)
particle identification
position and angular measurement : 50 mrad/E
E
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Physics with first data in ATLAS at the LHC – F. Derue (LPNHE Paris)
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Barrel/Encap LAr Calorimeter Installation
170 tons assembly
One end-cap calorimeter (LAr EM, LAr HAD, LAr Forward inside same cryostat,
surrounded by HAD Fe/Scintillator Tilecal) being moved inside the barrel toroid
FAE06, Caracas, Dec 11th 2006
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The hadronic calorimeter and jet reconstruction
November 4th 2005: Calorimeter barrel after its move into the
center of the ATLAS detector
FAE06, Caracas, Dec 11th 2006
Physics with first data in ATLAS at the LHC – F. Derue (LPNHE Paris)
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Muon spectrometer
The Muon Spectrometer is instrumented with precision
chambers and fast trigger chambers
Precision chambers:
Trigger chambers:
- MDTs in the barrel and end-caps
- RPCs in the barrel
- CSCs at large rapidity for the
- TGCs in the end-caps
innermost end-cap stations
TGC big wheel
Toroidal field to bend muons
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Physics with first data in ATLAS at the LHC – F. Derue (LPNHE Paris)
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Trigger system
25 ns is the time interval to consider !
Level 1 trigger
hardware trigger (2.5 ms latency)
calorimeter + muon chambers
defines Regions Of Interest (ROI)
40 MHz
75 kHz
Level 2
processing in parallel info from ROI,
uses ID information (latency 10 ms)
~2 kHz
Event Filter
uses tools similar to “offline” code
thanks to longer latency ~1s
~ 200 Hz
Challenge
have tracking, b-tagging and time information
at trigger level  speed !
FAE06, Caracas, Dec 11th 2006
Physics with first data in ATLAS at the LHC – F. Derue (LPNHE Paris)
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The data treatment at the LHC
Needs for LHC experiments
each event is independent of the others
computing power ~100000 PC (P4 3 GHz, 2 GB ram)
storage capacity for LHC experiments
20 petabytes/y on magnetic tape
1 petabyte/y on disc for the analysis
possibility to access data from institutes
production of Monte Carlo data necessary to the understanding
of results of the analysis (30 mn/event)
ATLAS computing model
first publication mid-2005 (Technical Design Report),
first modifications in 2006,
will have to adapt with first data
grid part
use as much as possible standard LCG (LHC Computing Grid) tools
have to be fully operational (low error rate in production, error monitoring …)
FAE06, Caracas, Dec 11th 2006
Physics with first data in ATLAS at the LHC – F. Derue (LPNHE Paris)
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Towards physics
1: Testbeams
2: Subdetector Installation,
Cosmic Ray Commissioning
2.5: Spring ’07: Global cosmic run
3: Single beam
4: First LHC collisions
5: First Physics
2005
FAE06, Caracas, Dec 11th 2006
2006
2007
Physics with first data in ATLAS at the LHC – F. Derue (LPNHE Paris)
2008
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Towards physics : test beams 2001-2002
H6 & H8 beam lines at CERN
TRT experimental setup
Beam chambers
LArEM series modules
Si layers
Cerenkov
counter
Calorimeter
TRT prototypes
p, e and m beam from 1-300 GeV
Studies presented :
- transition radiation
for e/p separation
FAE06, Caracas, Dec 11th 2006
4 barrel and 3 end-cap production modules
e and  beam from 10-300 GeV
Studies presented :
- energy resolution, constant term
- shower development
- /p separation
Physics with first data in ATLAS at the LHC – F. Derue (LPNHE Paris)
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Towards physics : combined test beam 2004
Full « vertical slice » of Atlas tested on CERN H8 beam line
between May-November 2004
G4 simulation
of subdetectors
setup
TRT
beam
Pixels + SCT
90 millions events collected
4.6 Tbytes of data
beams:
e±,p± 1250 GeV
m±,p±,p  350 GeV

~30 GeV
B from 01.4 T
Muon
LArEM
Tile
For the first time, all Atlas
sub-detectors integrated and
run together with:
- « final » electronics
- common DAQ
- slow control
- common Atlas software to
analyse the data
First experience with :
- Inner Detector alignment
- ID/Calo alignment
- ID/Calo track matching
- ID/Calo combined reconstruction
FAE06, Caracas, Dec 11th 2006
Physics with first data in ATLAS at the LHC – F. Derue (LPNHE Paris)
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e/p separation using the TRT
Electron identification makes use of the large energy depositions
due to the transition radiation (X-rays) when they traverse the radiators
Results from TB 2002
@20 GeV
Results from CTB2004
@9 GeV
Preliminary
Typical TR photon energy
depositions in the TRT are 8-10 keV
Pions deposit about 2 keV
FAE06, Caracas, Dec 11th 2006
90% electron efficiency
210-2 pion efficiency
Physics with first data in ATLAS at the LHC – F. Derue (LPNHE Paris)
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Performance of the LArEM
Calo TB 2001-2002
CTB 2004 (preliminary)
Energy resolution
10.00.1 % /E 0.210.03 %
Run 2102478
Ebeam=180 GeV
h = 0.3
sE/E ~0.83 %
@245 GeV
P13 production
module  > 7
4.5‰
rms  cL = 0.45 %
Energy (GeV)
Energy (GeV)
Constant term
@245 GeV
rms  cL=0.37%
h (middle cell unit)
h (middle cell unit)
Performance of the LArEM similar in both test beams
and in agreement with what expected
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Physics with first data in ATLAS at the LHC – F. Derue (LPNHE Paris)
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Electromagnetic shower shapes
LArEM beam test 2001-2002
Comparison between data and G4 standalone simulation
Longitudinal development
Lateral development
presampler
Fraction of E
rec. in 1st samp.
Ebeam = 10 GeV
Ebeam = 60 GeV
2rd samp.
Fraction of E
rec. in 3rd samp.
Ebeam = 100 GeV
Ebeam = 180 GeV
The p contamination and the non-uniform distribution of dead material located in the
beam line and not described in the Monte Carlo might explain the small discrepancy
Shower profile in agreement between data/simulation from 10 to 180 GeV
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Physics with first data in ATLAS at the LHC – F. Derue (LPNHE Paris)
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/p0 separation in full simulation and test beam
The identification of photons is based on set of cuts applied on calorimeters
information (no leakage in HCAL, narrow shower in EM2 Calorimeter).
After application of HCAL + EM2 criteria, the remaining background is
composed at ~80% of isolated p0’s produced by jet fragmentation
A /p0 separation ~3 is needed for =90%.
For this the fine granularity of the EM sampling 1 is used
Test beam 2002 @50 GeV
G4 full simulation

p0 → 
--- Data
--- G3 MC
E2nd max - Emin
R. Sacco (ATLAS Coll.)
NIM A(550), 2005
Fraction of energy
outside shower core
 = 90 %
Rp (G4) = 3.2 ± 0.2
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Rp (data) = 3.18 ± 0.12 (stat)
Rp (MC) = 3.29 ± 0.10 (stat)
Physics with first data in ATLAS at the LHC – F. Derue (LPNHE Paris)
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Towards physics : -conversions
ATLAS preliminary
Primary electron
ATLAS @ LHC:
-conversion probability in tracker
is > 30%  important to develop
(and validate !) efficient
reconstruction tools
Converted photon
Inner Detector tracks extrapolated
to ECAL and compared to calo clusters
 track
Run 2102857 event # 88

primary electron
converted 
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h
Physics with first data in ATLAS at the LHC – F. Derue (LPNHE Paris)
 cluster
25
Towards physics : m-system
The large-scale system test facility for alignment, mechanical,
and many other system aspects,
with sample series chamber station in the SPS H8 beam
Shown in this picture is the end-cap set-up, it is preceded
in the beam line by a barrel sector
Example of tracking the sagitta measurements, following the day-night variation due to thermal
variations of chamber and structures, and two forced displacements of the middle chamber
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Towards physics : cosmic rays runs
First cosmics rays
In December 2005 in MDTs
registered in the underground cavern
barrel muon chambers (MDT and RPC)
and level-1 m trigger
and in June 2006 in RPCs
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Towards physics : cosmic rays runs
Cosmic rays runs
event display in the barrel TRT and in the SCT
End of February 2006 the barrel SCT was inserted into
the barrel TRT, and this component will be ready
for the final installation in ATLAS in August 2006
after further commissioning at the surface with cosmics
Integrations of the two end-caps (SCT and TRT) are ongoing for installation end of 2006
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Towards physics : cosmic rays runs
Cosmic rays runs
event display from the first LAr+Tile calorimeter barrel cosmic run
The barrel LAr and scintillator tile calorimeters
have been since January 2005 in the cavern
in their ‘garage position’
(on one side, below the installation shaft)
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Towards physics : beam-halo events
From April-May 2007 ? Only one beam in the machine :
here physics data are beam-halo and beam-gas events
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Towards physics : beam-gas events
Collisions are essentially minimum bias
23 m : ~1.2105/s (integrated : 21011)
3 m : ~1.5104/s (21010; ID size)
20 cm : ~1103/s (2109; ID soft acceptance)
Particles : consider 3 m and ask pT>1 GeV
p : ~1.5109 over two months
 : ~5.5108 of one beam operation
spectrum is soft : few Hz of electromagnetic clusters with ET>2 GeV
trigger is an issue
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What samples in 2007 ?
First collisions (s = 900 GeV, L~1029 cm-2 s-1) : November 2007
commisioning run at injection energy until end 2007
30% data taking efficiency included (machine+detector) + trigger and analysis efficiencies
ATLAS preliminary s =900 GeV, L = 1029 cm-2 s-1
Jets pT > 15 GeV
(b-jets: ~1.5%)
Jets pT > 50 GeV
Jets pT > 70 GeV
 mm J/mm
W  e, m
Z  ee, mm
30 nb-1
100 nb-1
+ 1 million minimum-bias/day
start to commission triggers and detectors with collision data (min. bias, jets…)
in real LHC environment
may be first physics measurements (min. bias, underlying events, QCD jets..) ?
observe a few Wl, mm, J/ mm
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First physics run in 2008
First physics run (s = 1400 GeV, L~1032 cm-2 s-1) : spring 2008
1 fb-1 (100 pb-1)  6 months (few days) at L=1032 cm-2 s-1
with 50% data taking may collect a few fb-1 per experiment by end 2008
Process
s(pb)
N/s
N/year
Total collected
before start of LHC
W  l
3104
30
108
104 LEP / 107 FNAL
Zee
1.5103
1.5
107
107 LEP
1
107
104 Tevatron
106
1013
109 Belle/BaBar
tt
830
bb
5108
With these data
understand and calibrate detectors in situ using well-known physics samples
Zee,mm tracker, ECAL, muon chambers calibration and alignment, etc.
tt bl bjj jet energy scale from W jj, b-tagging performance, etc.
measure SM physics at s = 14 TeV : W, Z, tt, QCD jets…
(also because omnipresent backgrounds to New Physics)
 prepare the road to discovery …… it will take time …
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Top physics in 2008
Example of initial measurement: understanding detector
and physics with top events
can we observe an early top signal with limited detector performance ?
stt  250 pb for tt  bW bW  bl bjj
W.Verkerke
ATLAS preliminary
50 pb-1
4 jets pT> 40 GeV
3 jets with largest ∑ pT
2 jets M(jj) ~ M(W)
W+n jets (Alpgen) +
combinatorial background
Isolated lepton
pT> 20 GeV
NO b-tag !!
ETmiss > 20 GeV
in addition, excellent sample to :
commission b-tagging, set jet energy scale using W jj peak
understand detector performance for e, m, jets, b-jets, missing ET, …
understand / constrain theory and MC generators using e.g pT spectra
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Example of “early” discovery : Supersymmetry ?
If SUSY at TeV scale  could be found “quickly” … thanks to :
large q˜ , g˜ cross section ~10 events/day ar 1032 for m ( q˜ , g˜ ) ~ 1 TeV
spectacular signatures (many jets, leptons, missing ET)
M (TeV)
2.5
1.5
1
ATLAS + CMS
1
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q


Z
01
Our field, and planning for future
facilities, will benefit a lot from
quick determination of scale of
New Physics. e.g. with 100 (good)
pb-1 LHC could say if SUSY
accessible to a 1 TeV ILC
2
100 pb-1
q˜
02


q
g˜
10
100
BUT: understanding ETmiss
spectrum (and tails from instrumental effects) is one of the
most crucial and difficult
experimental issue for SUSY
searches at hadron colliders
Luminosity/expt (fb-1)
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Example of “early” discovery : Supersymmetry ?
Jets + ETmiss (0l)
ATLAS preliminary
Jets + 1l +ETmiss
S.Asai
1 fb-1
m ( q˜ , g˜ ) ~ 1 TeV

M eff (GeV) =
E
i=1,4
ETmiss
spectrum contaminated by cosmics,
beam-halo, machine/detector problems, etc.
T
(i)  E T
miss
Estimate physics backgrounds using
data (control samples)
ATLAS preliminary

1 fb-1
I.Okawa et al.
Run II
V. Shary CALOR04
after
cleaning
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no cleaning
R: Z() +jets
B: as estimated
from W(m)+jets
Missing ET (GeV)
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SM Higgs boson with first data
Current indications are for a ‘light Higgs’ : search for Higgs
in mass region 114<mH<200 GeV is crucial
*July 2006. Combination of CDF+D0 Run I+II results
mt = 171.4 1.2 (stat) 1.8 (syst) GeV
Signal cross section (including BR) can be as low as 10-14 the total cross section
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SM Higgs boson with first data
signal
H key ingredients :
rare decay mode with BR~10-3 (2.186 10-3 for mH=120 GeV)
the signal should be visible as a small peak
above the  continuum background
good energy resolution of
the electromagnetic calorimeter
background
Irreducible background consists of genuine photons pairs continuum.
~125 fb/GeV @ NLO for mH=120 GeV (after cuts and photon efficiency)
Reducible background comes from jet-jet and gamma-jet events
in which one or both jets are misidentified as photons
(reducible/irreducible cross section (LO-TDR) 2106 (jj) and ~8102 (j)
excellent jet rejection factor (>103) for 80%  efficiency
sever requirements on particle identification capabilities of the detector
especially the electromagnetic calorimeter
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SM Higgs boson with first data
3 (complementary) channels with similar (small) significances
H  
ttHttbb  blbjjbb
qqH  qq

b
H
b
S=130, B=4300, S/B=2
S=15, B=45, S/B=2.2

S=10, B=10, S/B=2.7
different production and decay modes
different backgrounds
different detector/performance requirements
ECAL crucial for H (in particular response uniformity) : s/m ~1% needed
b-tagging crucial for ttH : 4 b-tagged jets needed to reduce combinatorics
efficient jet reconstruction over |h|<5 crucial for qqHqq
(forward jet tag and central jet veto needed against background)
All three channels require very good understanding of detector
performance and background control to 1-10%
 convincing evidence likely to come later than 2008
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SM Higgs boson with first data
Needed Ldt (fb-1)
per experiment
10
H  m  m e e
muon
--- 98% C.L. exclusion
 1 fb-1 for 98% C.L. exclusion
 5 fb-1 for 5s discovery
over full allowed mass range
electron
electron
ATLAS + CMS
preliminary
10-1
Events / 0.5
GeV
1
Signal expected in ATLAS
after ‘early' LHC operation
mH (GeV)
here discovery easier with
gold-plated H  ZZ  4l
 by end 2008 ?
H  4l : narrow mass peak, small background
H  WW  ll (dominant at the Tevatron):
counting channel (no mass peak)
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B physics with first data
Dms with BsDsp
Nevents after trigger + offline rec. 30 fb-1
Signal
Bs→D-s p
Dms
Bs→D-sa1+
Models used in MC or to confront
experimental sensitivities.
Backgr
8250
<100%
4060
<100%
NP: Ball,Khalil,
Phys.Rev.D69:115011,2004
given the low value measured by CDF
ATLAS will be able to measure Dms with ~10 fb-1 (one year)
330.07 ps1
CDF:Dms 17.3100..18
D0 :17  Dms  21 ps1 @90% c.l.
CP violation in BsJ/ :s = -2l2h = -2 tiny in SM (-0.0360.003 from
CKMfitter) and not accessible by any of the LHC experiments
Nevents after trigger + offline rec. 30 fb-1
Signal
Bs→J/
s
DGs
270k
Backgr
15%

Models used in MC or to confront
experimental sensitivities.
SM: Fleisher CERN-TH-2000-101
NP: Ball,Khalil,
Phys.Rev.D69:115011,2004
New Physics could lead to enhanced and measurable CP violation
8 parameters extracted in maximum likelihood fir to angular distribution of the decay
A||(t=0), AT(t=0), d1, d2, Dms, DGs
to avoid failing a fit due to high xs-s correlation xs was fixed
xs
s(s)~0.046 for xs=20 ps-1, s(DGs)/DGs=13%, s(Gs)/Gs=1%
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BTW: why am I here ?
HELEN (High Energy Latin American European Network)
students in physics groups
engineers in computing groups
VenezuelaFrance
physics groups
A. Cimmarusti (ULA) in Paris for top quark
H. Martinez (ULA) in Paris for Higgs
computing groups
G. Diaz (CECALCULA) in Lyon for Tier1
V. Mendoza (Paris for Tier2)
new “bunch” ~March 2007
FranceVenezuela
physics groups
J. Malclès (Paris) in Mérida
F. Derue (Paris) in Mérida
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Conclusion
New LHC schedule
machine and experiments closed 31 August 2007
commissioning run at s=900 GeV end 2007
first physics run at 14 TeV starting in spring 2008
Experiments on track to meet above schedule.
Test-beam and cosmics results indicate they work as expected
All efforts now to continue installation and commissioning of machine
and detectors of unprecedented complexity, technology and performance
With the first collision data (1-100 pb-1) at 14 TeV: understand detector
performance in situ in the LHC environment,
and perform first physics measurements
measure particle multiplicity in minimum bias (a few hours of data taking…)
measure QCD jet cross-section to ~30% ?
(expect >103 events with ET(j)>1 TeV with 100 pb-1)
measure W, Z cross-sections to 10% with 100 pb-1 ?
observe a top signal with ~30 pb-1
measure tt cross-section to 20% and m(top) to 7-10 GeV with 100 pb-1 ?
improve knowledge of PDF (low-x gluons !) with W/Z with O(100) pb-1 ?
first tuning of MC (minimum bias, underlying event, tt, W/Z+jets, QCD jets…)
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Conclusion
And, more ambitiously
discover SUSY up to gluino masses of ~1.3 TeV ?
discover a Z’ up to masses of ~1.3 TeV ?
surprises ?
Later on the LHC will explore in detail the highly-motivated TeV-scale
with a direct discovery potential up to m~5-6 TeV
if New Physics is there, the LHC will find it
it will say the final word about the SM Higgs mechanism and many TeV-scale predictions
it may add crucial pieces to our knowledge of fundamental physics
 impact also on astroparticle physics and cosmology
most importantly : it will likely tell us which are the right questions to ask,
and how to go on
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