The LHC The First Few Years WHEPPX, Chennai, India 3108

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The LHCThe First Few YearsWHEPP-X, Chennai,
India 3/1/08
Albert De Roeck CERN and
University of Antwerp and the IPPP Durham
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Contents

• Introduction
• Machine status update
• News from CMS ATLAS
• First physics at the LHC
• Some new signatures (the unexpected?)
• Needs from the LHC at start-up
• After the Champagne
• Outlook

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The LHC a proton proton collider
7 TeV 7 TeV P P

• Primary physics targets
• Origin of mass
• Nature of Dark Matter
• Understanding space time
• Matter versus antimatter
• Primordial plasma

The LHC will determine the Future course of High
Energy Physics The LHC will
start operation this year
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The LHC Machine and Experiments
Luminosity First phase 2?1033
cm-2s-1 High lumi phase 1034 cm-2s-1
LHCf
(moedal)
pp collisions at 14 TeV
totem
?High Energy ? factor 7 increase
w.r.t. present accelerators ?High Luminosity (
events/cross section/time) ? factor 100 increase
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LHC General Schedule
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Completing the LHC
7 November 2007 Connecting the last Dipoles of
the LHC
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Present schedule Scenario of Maximal
Success First 14 TeV collisions
June/July ?Collect 0.1-(1) fb-1 in 2008
? ?Collect 5-10 fb-1 in 2009? gt10 fb-1 in
2010?
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General Purpose Detectors at the LHC
? Tracker ? EM calorimeter ? Hadron calorim. ?
Muon detectors
In total about 100 000 000 electronic
channels Each channel checked 40 000 000
times per second (collision rate is 40 MHz)
Amount of data of just one collisions gt1 500
000 Bytes Trigger (online event selection)
Reduce 40 MHz collision rate to 100 Hz data
recording rate Readout to disk 100
collisions/sec ? pentaBytes of data/year
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CMS Status
Si Tracker ready
Barrel ECAL installed Endcaps to be installed
April and June 08
Pixel det to be completed in Jan 08
December 2007 8/11 elements have been
lowered Remaining in Jan 08
180 institutions 38 countries 2000 authors
Muon detectors installed
HCAL ready since 2006
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Cosmics in central barrel ring
HB
Bottom wedges
YB0
Top wedges
Eta tower
phi tower
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ATLAS Status
ATLAS instalation nearing completion Wall-wheels
being assembled (the last missing components)
164 institutions 35 countries 1800
scientific authors
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Event Display of a Cosmic
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Physics at the LHC pp _at_ 14 TeV
Extra Dimensions?
Black Holes???
Higgs!
Supersymmetry?
QGP?
CP triangle!
Precision measurements e.g top!
?LHC will explore directly the highly-motivated
TeV-scale and say the final word about the SM
Higgs mechanism and many TeV-scale New Physics
predictions ?Also LHC will be a great machine
for QCD, B-physics, Heavy Ions, EW precision..
The LHC will be the new collider energy frontier
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pp collisons complications
Protons have structure
Parton distributions
Underlying event
Huge cross sections
Pile-up
New physics ?
Close collaboration with theory will be essential
!!
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Pile-up at the LHC
Pile-up ? additional -mostly soft- interactions
per bunch crossing Startup luminosity
2?1033cm-2s-1 ? 4 events per bunch crossing High
luminosity 1034cm-2s-1 ? 20 events per
bunch crossing Luminosity upgrade
1035cm-2s-1 ? 200 events per bunch crossing
SUSY event (no pileup)
SUSY event (1034cm-2s-1)
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Event filtering the trigger system
Collision rate is 40 MHz Event size 1
Mbyte 2007 technology (and budget) allows only to
write 100 Hz of events to tape
need a factor 107 online filtering!!
lost forever!!
written to disk for offline analysis
The event trigger is one of the biggest
challenges at the LHC ? Based on hard scattering
signatures jets, leptons, photons, missing Et,
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Start-up Physics 2008
0.1-1 fb-1
In 2008 we have to rediscover the Standard Model
at 14 TeV and compare to calculations and
generators. And tune generators
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Early Soft Minimum-Bias Measurements
The pile-up for the future 4 events at low and
20 events at high luminosity
Charged particle density
LHC?

• Energy dependence of dN/dh ?
• Vital for tuning UE model
• Only requires a few thousand events.

• PYTHIA models favour ln2(s)
• PHOJET suggests a ln(s) dependence.

At 14 TeV startup!!
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QCD Studies _at_ LHC
Huge cross sections Eg for 1 fb-1 10000
events with ETgt 1 TeV
100 events with ETgt 2 TeV
E.g. Jet Physics

• ? PDFs
• Jet shape
• Underlying event
• ?s?
• Diffraction
• BFKL studies
• low-x
• New physics?

?Understanding QCD at 14 TeV will be one of the
first topics at LHC
and a whole b-physics and top-physics program
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Top quarks
First top quarks in Europe!
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Higgs Physics
? What is the origin of Electro-weak Symmetry
Breaking? ? If Higgs field at least one new
scalar particle should exist The Higgs One
of the main missions of LHC discover the Higgs
for mHlt 1 TeV
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SM Higgs Search Channels
Low mass MH ? 200 GeV
Intermediate mass (200 GeV ? MH ?700 GeV)
High mass (MH ? 700 GeV)
VBF qqH ? ZZ ? ll?? VBF qqH ? WW ? l?jj
inclusive H ? WW inclusive H ? ZZ
H ? ?? and H ? ZZ ? 4l are the only channels
with a very good mass resolution 1
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Higgs Searches
High MH gt 500 GeV/c2
Medium 130ltMHlt500 GeV/c2
Low MH lt 140 GeV/c2
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First days Higgs ???
? Requires O(10) fb-1
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Higgs search with more luminosity
Gianottij ADR et al.
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Beyond the Standard Model
New physics expected around the TeV scale
? Stabelize Higgs mass, Hierarchy problem,
Unification of gauge couplings, CDM,
Supersymmetry
Extra dimensions

a lot of other ideas/studies Split SUSY,
Little Higgs models, new gauge bosons,
technicolor, compositeness, heavy leptons..
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Early discoveries? E.g. Di-lepton Resonance
If we are lucky a signal could be seen very
early on
First months of operation
CMS PTDR
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Supersymmetry
SUSY could be at the rendez-vous very early on!
10fb-1
Therefore SUSY one of the priorities of
the search program
Main signal lots of activity (jets, leptons,
taus, missing ET) Needs however good
understanding of the detector SM processes!!
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Missing Transverse Energy
Tevatron experience! Clean up cuts cosmics, beam
halo, dead channels, QCD
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Events with bad missing ET
F. Paige CTEQ meeting May 07
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Detailed Simulation Missing ET
Low mass SUSY
Missing ET is a difficult measurement for the
experiments
CMS PTDR
Signal over background in ETmiss for the LM1
point
Normalizing Z??? ETmiss to Z??? using data
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SUSYBSM Inclusive SUSY Searches
Searches based on different signatures
CMS PTDR

• Low mass SUSY(mgluino500 GeV) shows excess for
  O(100) pb-1
• Time for discovery determined by
• Time to understand the detector performance,
  Etmiss tails,
• jet scale,lepton id
• ?Time collect SM control samples such as Wjets,
  Zjets, top..

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Early SUSY?
F. Gianotti, ADR et al.
Something to watch for the ILC
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Sparticle Mass Reconstruction
D. Miller et al use also the shapes
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Dark Matter

• Fit the model parameters of the assumed SUSY
  breaking model to the measured SUSY particle
  masses ???h2
• Typical precision

ILC international linear collider ee-
collider _at_ 0.5-1 TeV
WMAP
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Is it SUSY?
Example Universal
Extra Dimensions Phenomenology a Kaluza
Klein tower pattern like a SUSY mass spectrum
Can the LHC
distinguish?
e.g. Cheng, Matchev, Schmaltz hep-ph/0205314
Look for variables sensitive to the particle spin
eg. lepton charge asymmetries in squark/KKquark
decay chains Barr hep-ph/0405052 Smillie
Webber hep-ph/0507170
Needs 10 fb-1 or more.
KK like spectrum (small mass splitting)
SPS1a benchmark type spectrum
Method works better or worse depending on
(s)particles spectrum
More discriminating variables needed!!
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Spin measurements
Recently lot of new ideas being proposed (see T.
Plehn HCP07, Elba) Most still need
the detailed test of the experimental reality
Kilic-Wang-Yavin Spin measurements in cascade
decays Angular correlations in decays Alves-Ebol
i Sbottom spin Alves-Eboli-Plehn Spins in Gluino
Decays Athanasiou-Lester-Smillie-Webber Distingui
shing spins in decay chains at the
LHC Choi-Hagiwara-Kim-Mawatari-Zerwas Tau
polarization in SUSY cascade decays Further
Wang Yavin, S. Thomas et al,
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ADD Extra Dimensions
ADD Arkani Ahmed, Dimopolous,Dvali
Graviton production! Graviton escapes detection
Signal single jet large missing ET
Signal single photon large missing ET
Hinchliffe, Vacavant
30fb-1
PT photongt 400 GeV
Test MD to 4 TeV for 100 fb-1
2.5 TeV for 10 fb-1
Test MD to 7-9 TeV for 100 fb-1
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Curved Space RS Extra Dimensions
phenomenology
Study the channel pp?Graviton? ee-
signal Drell-Yan backgr.
sensitivity
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Z/Randal-Sundrum ED graviton Reach
New Study RS decays into 2 photons
Z
RS
CMS PTDR
RS Combined plots for electron and muon (and ?
?) channel Most of the relevant RS
parameter space is covered already with 10 fb-1
Z Low lumi 0.1 fb-1 discovery of 1-1.7 TeV
possible, beyond Tevatron run-II High lumi
100 fb-1 extend range to 3.4-4.6 TeV
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New W Bosons
3.5-4.7 TeV W is observable with 1-10
fb-1 Studied in the W??? channel
CMS PTDR
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Black Holes Production
If the Planck scale in TeV region can expect
Black Hole production
These BH decay within 10-26 sec
sphericity
Spherical events Many high energy jets
leptons, photons etc. Spectacular
Signals! Quantum Gravity in the lab?
Simulation of a black hole event with MBH 8
TeV in ATLAS
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Black Holes
Warning cross section could be much less than
optimistic estimates
Black Hole cross section????

• For 10 fb-1
• Classical approximation to cross-section large!
  Black Holes up to 8-10 TeV
• Apparent horizon (AH), not all energy trapped
  see eg. hep-ph/0609055
• Black holes up to 4-5 TeV

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Black Holes Hunters at the LHC
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Little Higgs Model AH and ZH
Littlest Higgs Model
Signal di-lepton resonance
Arkani-Hamed et al., Han et al.
Reach up to 5.7 TeV depending on the ? angle
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Contact Interactions
Using dijet event ratios
New!
Test up to ? 10 TeV during 08/09 already
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New Physics in the B sector (LHCb)
L. Camilleri Cairo March 07
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New Physics in the B sector (LHCb)
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Recent Studies New Signatures
Arkani-Hamed, Dimopoulos hep-th/0405159

• Split Supersymmetry
• Assumes nature is fine tuned and SUSY is broken
  at some high scale
• The only light particles are the Higgs and the
  gauginos
• - Gluino can live long sec, min, years!
• - R-hadron formation slow, heavy particles
  containing a heavy gluino.
• Unusual interactions with material
• eg. with the calorimeters of the
  experiments!
• Gravitino Dark Matter and GMSB
• In some models/phase space the gravitino is the
  LSP
• Then the NLSP (neutralino, stau lepton) can live
  long

K. Hamaguchi,M Nijori,ADR hep-ph/0612060 ADR, J.
Ellis et al. hep-ph/0508198
Sparticles stopped in the detector,walls of the
cavern, or dense stopper detector. They decay
after hours---months
?Challenge to the experiments!
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New CMS Analyses
? GMSB Non-pointing photons
GMSB parameters
non-pointing
pointing
? ct lifetime extraction with 20 precision
? GMSB long living staus
GMSB parameters
Timing (?) in muon detectors
stau mass extraction with a few precision
? R-hadrons
de/dx in the tracker

• ?-tracker
• ?-muons

trigger/mass meas. for region ? gt 0.6
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Split SUSY
Arvanitaki et al.
? Requires special triggers/analysis
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Hidden Valley Physics?
String Theory inspired (M. Strassler)
Eg. Strassler Zurek hep-ph/0604261
New possible phenomena that could occur in these
models
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Some Hidden Valley Signals
H? 4 b
Production rates for v-hadrons
Valley quark production
The Fear Factor A real challenge for the
triggers at the LHC
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Hidden Valleys?
String Theory inspired (M. Strassler)
Eg. Strassler Zurek hep-ph/0604261
Example H? 4 b
The Fear Factor A real challenge for the
triggers at the LHC
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Unparticles
Top decay

• QFT possibility sector that is scale invariant
• (CFT) leading to new physics weakly coupled
• to SM through heavy mediators
• ?Unparticle stuff (Georgi, 07 gt100 new papers)

Georgi
Missing ET
arXivhep-ph/0703260

• Real unparticle production
• Monophotons at LEP ee- ? ? U
• Monojets at Tevatron, LHC g g ? g U
• Virtual unparticle exchange
• Scalar unparticles f f ? U ? ? ?- ,
• gg, ZZ, No interference with SM
• Vector unparticles ee- ? Um ? ? ? -, qq,
• Other signatures funny jets
• high multiple
  photon rates

Decaying unparticles
Rizzo
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Macro-Strings at the LHC?
New strong interactions with small ? new quarks
mQgt several hundered GeV
Markus Luty/Aspen 07
? Strings do not break up ? Stringy objects in
the detector. ? End points are massive quarks
(quirks) ? The strings can oscillate? strange
signature in detectors
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BSM and SM backgrounds
M. Peskin SUSYtools Annecy 06
There are more signals (topjets, ) that will be
used, but it illustrates the point
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Tools Theoretical Estimates
The LHC will be a precision and hopefully
discovery machine But it needs
strong collaboration with theorists

• 
  Examples
• Precision predictions of cross sections (W,Z,
  Drell Yan) at 14 TeV
• Estimates SM processes for backgrounds to new
  physics and uncertainties !!!
• Examples QCD multjets events, W,Z,t.. njets,
  diboson production.
• Monte Carlo programs (tuned) for SM processes
  MEparton showers, PDF4MCs
• Monte Carlo programs for some new physics
  signals (EDs, new signatures)
• Higher order calculations both QCD and
  electroweak corrections
• New phenomenology/signatures to look for ? make
  sure the trigger is prepared
• Discriminating variables among different
  theories what are the footprints?
• Characterizing new physics E.g. getting spin
  information from particles, CP
• Prepare Tools to interprete the new signals in
  an as model independent way as possible
  (MARMOSET, other?). Resolving degeneracies
• Prepare/complete tools to test new model phase
  space with current constraints

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Requirements tools and calculations

• Les Houches 05 What are the real uncertainty
  bands (from higher orders,scale uncertainties,
  PDFs). This has not yet been done even for some
  simple cases!
• We will obviously try to use our own data as
  much as possible (sidebands, independent
  measurements) but tuned Monte Carlos will play an
  important role in the analysis. Hence Standard
  Model processes will be important particularly
  W,Z jets, tt jets , bb jets, n-jets
• ? Calculations and generators NLO, NNLO
  MEPS matching
• Upgrade MC_at_NLO for
• WW, WZ with spin correlations, DY, Wjets
• MC_at_NLOPYTHIA
• Event generator including EW effects
• Event generator based on Ariadne QCD treatement
• PYTHIA6.3 tuned version
• Underlying event/minimum bias event decriptions
• Toolkits for SM and BSM processes (via
  LH-accords)

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Effective Mass
Old estimate
Old PYTHIA BG New ALPGEN BG
New estimate
All jets Final state
Reach lower?
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Higher QCD corrections/K factors
Effect on Higgs discovery
?Many cross sections now calculated to NLO ?K
factors? Not always sufficient/can be huge in
some phase space parts ?Reweighting Monte Carlo?
Select key weighting variables Complete NLO
Monte Carlo! Quite some progress in the last
years. More processes wanted ?!!
Priority wish list from the experiments
hep-ph/0604120 (Les Houches 05)
Zbb, Hbb
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Constraints of present data
LHC weather forecasts
CMSSM with non-Universal Higgs masses
? arXiv0707.3447
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After the Champagne

• WHEN new physics is discovered at the LHC, how
  well can we determine what it is? Does a
  specific experimental signature map back into a
  unique theory with a fixed set of parameters?
• Even within a very specific context, e.g., the
  MSSM, can one uniquely determine the values of,
  e.g., the weak scale Lagrangian parameters from
  LHC data alone?

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The Inverse Mapping of Data there are many
possible outcomes.
Much of the time a specific set of data maps
back into many distinct islands/points in the
model parameter space ? model degeneracy
Arkani-Hamed, Kane, Thaler, Wang,
hep-ph/0512190 Kane, Kumar and Shao,
arXiv0709.4259 J. Hewett et aL. arXiv0711.
The efforts to understand the problems and design
strategies - even before data- are very important!
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The Inverse Problem
MARMOSET
hep-ph/0703088, N. Arkani-Ahmed et al
Looks like an interesting communication tool with
theorist
Lester et al., hep-ph/0508143
Kane et al., arXiv0709.4259
Other
footprints
? Common ground of interest for theorist and
experimentalists
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Summary

• The LHC and its experiments are on track for
  collisions at 14 TeV starting middle 2008
  onwards, if no significant problems come up
• Challenge commissioning of machine and detectors
  of unprecedented scale, complexity, technology
  and performance
• The LHC will break new ground in exploring the
  TeV scale and hunt for new physics (SUSY?, EDs?
  Z? Quirks? Unparticles...)
• Will it be easy and fast with the first
  luminosities as we all hope, or shall we have to
  sweat through years of data taking and hard work
  before we can claim a discovery ? Watch out for
  weird signatures!
• Once discovered, characterizing the new physics
  and determine the underlying theory will be the
  new challenges
• Theory ? Exp. must work close together

In 2008() the real games will be on
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What can we expect in 2010 with 10 fb-1?
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Backup slides