anna lipniacka, the large hadron collider , the first …...the bright universe in a nutshell...
TRANSCRIPT
Anna Lipniacka,
The L
HC
, initial physics
The Large Hadron Collider , the first 3 minutes
The state of the Universe
Brief history of particle physics
LHC physics, a simplified hitchhiker guide.
(Supersymmetry and Higgs boson ) (B physics, heavy ions in other talks)
The LHC in a nutshell
Anna Lipniacka,
The L
HC
, initial physics
Disclaimer
The LHC is starting in ~1.5 year. This is VERY SOON..
The LHC initial physics is an OLD SUBJECT studied for years withenormous detail by many a theoretician and experimentalist. Thousandsof publications and presentations exist.
The focus now is on how are we actually going to commission initialphysics in practice: interplay of quick understanding of the detector and“standard physics” to pave the road for discovery.
My approach here: show you few “standard slides” on physics commissioning. Then take an old fashioned approach to remindyou why physics is interesting. Go back to details on initial LHC physics.
Anna Lipniacka , Course in Particle Physics, L8
LEP : e+e-, Ecms~ 209 GeVLHC : pp, Ecms~ 14000 GeV
CERN
4 LEP experiments: 2 LHC general experiments
© PhotoC
ERN
DELPHI2 more special LHCB
Replacing LEP with the LHC
One ring to find them all...
Anna Lipniacka,
The L
HC
, initial physics
The LHC tunnel to be
27km of vacuum pipe
8.3Tesla bending magnets,
3o above absolute zero
© PhotoCERN
Energy limited by SC magnets technology and cost p
pF
F
B
B
N
N
S
Atlas detector
Compact Muon Solenoid
Magnets
The choice of magnetdetermines the characteristicsof the detector
Anna Lipniacka,
The L
HC
, initial physics
ATLAS cavern, October 2005
Anna Lipniacka,
The L
HC
, initial physics
Atlas in statu nascendi
Anna Lipniacka,
The L
HC
, initial physics
Atlas, the general purpose detector
Anna Lipniacka,
The L
HC
, initial physics
Cosmic muons in ATLAS pit in 0.01 s ….
From full simulation of ATLAS (including cavern, overburden, surface buildings) + measurementswith scintillators in the cavern:
~ 106 events in ~ 3 months of data taking enough for initial detector shakedown
(catalog problems, gain operation experience, some alignment/calibration, detector synchronization, … )
Throughgoing muons ~ 25 Hz(hits in ID + top and bottom muon chambers)
Pass by origin ~ 0.5 Hz(|z| < 60 cm, R < 20 cm, hits in ID)
Useful for ECAL calibration ~ 0.5 Hz (|z| < 30 cm, E cell > 100 MeV, ~ 900 )
First cosmic muonsobserved by ATLAS in the pit on June 20th(recorded by hadronTilecal calorimeter)
Tower energies:~ 2.5 GeV
Tracking and alignment in Muon Spectrometer
BIL on rotating frameBIL on rotating frameCSC
MBPS
BOS+BIS
MBPL
Scintillators
TGC
MDT’s
RPC’s
3996 channels out of 4000 working
Muon chamber installation in ATLAS pit
Combined test beam
Atlas pit
Tracking and alignment in Inner Detectorcombined test beam
xy
z
6 pixel modules and 8 SCT modules (inside B=0→1.4 T)6TRT modules (outside field)
Anna Lipniacka,
The L
HC
, initial physics
Strategy for Physics commissioning
Before data taking starts: Understand and calibrate (part of) detector with test beams, cosmics, … Prepare software tools: simulation, reconstruction, calibration/alignment procedures
In particular : realistic description of detector “as built and as installed” (actual placement, mis-calibrations, HV problems, dead channels, etc.) Develop (theorists), validate (with Tevatron and HERA data), compare MC generators
After data taking starts:
Commission/calibrate detector and trigger in situ with physics samples (Z→ ll, tt,…) Understand SM physics at √s =14 TeV (minimum bias, W, Z, tt, QCD jets, …) Validate and tune MC generators Measure backgrounds to New Physics (W/Z+jets, tt+jets, QCD multijets, …)
prepare the road to discovery
Anna Lipniacka,
The L
HC
, initial physics
LHC schedule...
Everything depends on how much LUMINOSITY LHC will provideat the start: number of events=(luminosity)*(cross-section)
Anna Lipniacka,
The L
HC
, initial physics
How many events in ATLAS at the beginning ? And when ?
1 fb1 ≡ 6 month
at 1032, ε=50%
5 fb1 ≡ 3 month at 1032
+ 3 month at 1033, ε=50%
→ end 2007 ? → end 2008 ?
similar statisticsto CDF, D0 today
10 pb1 ≡ 1 monthat 1030 + < 2 weeks
at 1031, ε=50%
100 pb1 ≡ few days
at 1032 , ε=50%
L=1033 cm−2 /s10 / fb yearxsections mbar− fbarn 10−3−10−15barn
Anna Lipniacka,
The L
HC
, initial physics
The state of the Universe
Consists of :
Is 13.7 +- 1% billion years old and expands at a rate 71+-5% km/s/MPC
and it will most probably expand forever.
What is Dark Energy?: we do not know.. it isan energy component which effectively makes theUniverse to accelerate its expansion. Also observedlooking at distant supernovas
Wilkinson Microwave Anisotropy Probe
What is Dark Matter ?: we do not know.. It mustbe made of weakly interacting heavy particles ( heavier than 50 proton masses). Observed as wellin rotational velocities of spiral galaxies. Localdensity ~ 0.3 proton mass/cm close to five Dark Matter particles in your coffee cup
3
WMAP satellite
But exactly how many ?
Ωtot= Ωbaryons+ ΩCDM+ ΩΛ=1
Anna Lipniacka,
The L
HC
, initial physics
The WMAP satellite
Detecting 10 “ripples” in microwave background radiation-6
Anna Lipniacka,
The L
HC
, initial physics
If not enough matter, the objects in galaxies would fly apart F. Zwicky, Astrophys. J. 86 (1937) 217.
Dynamical evidence for massive halos in 1970’s M.S. Roberts, A.H. Rots, Astrophys. 26 (1973) 483.
Galaxy rotation curves
L. Bergström,University of Stockholm Rep.Prog.Phys. 2000
Most of the matter in the universe is dark: it does not emit light
The Dark Side
Anna Lipniacka,
The L
HC
, initial physics
VIRGOHI21 is a dark matter galaxy with neutral hydrogen mass of ~108M , while the mass of the galaxy is ~1011M. .
R. Minchin, J. Davies, M. Disney, P. Boyce, D. Garcia, C. Jordan, V. Kilborn, R. Lang, S. Roberts, A. Sabatini, W. van Driel, ApJ 622 (2005) L21 (press release on Feb 23, 2005):
The Dark Side
Anna Lipniacka,
The L
HC
, initial physics
“There is no Light without Darkness”
How to learn about the Dark and the Bright Side of the Universe?
3K
6000K~1 eV
10 K~ 1 MeV
1s
10
3 min
300000years
13.7 billion years
10 K 15100 GeV
10-10s
10 GeV14
10 s-34
DM
Anna Lipniacka,
The L
HC
, initial physics
Recreate the past?
Recreate the energy available per particle in the Early Universe:
Accelerate particles
Collide them -> “small Big Bang”
Hope that particle species which existed in the appropriate“energy epoch” be produced, try to find them outin the series of “ small Big Bangs”
Take charged, stable, easily available particles, preferablywith no internal structure.
(LEP, Tevatron, SSC and the LHC)
Anna Lipniacka,
The L
HC
, initial physics
Probe the present with high precision?
In QFT all virtually existing states affect all real states. Every particle “drags” behind a cloud of virtual particles.
Vacuum polarization effects make charges and masses dependent on the distance (energy of our probe).
There are many measurable examples: Lamb shift, dependenceof electromagnetic charge on the energy...
Thus if we measure properties of known particles at severaldistances, with very high precision we might learn about otherpossibly existing states.
Anna Lipniacka,
The L
HC
, initial physics
The Bright Universe in a nutshellNewton, Optics (1680) :Now the smallest Particles of Matter may cohere by strongest Attractions, and compose bigger Particles of weaker Virtue. There are therefore Agents in Nature able to make Particles of Bodies stick together by very strong Attractions. And it is the business of experimental Philosophy to find them out.Particles of Matter (fermions) Agents in Nature (bosons)
A bit of history of discovering:
1898-1909 : Dividing the Atom, the electron and nucleus observed
1919-1931: Dividing the Nucleus.Proton and Neutron discovered maybe there is even a (anti) neutrino . Happy but short era of " all three elementary particles" needed to build matter around us known
1931-1947 : Who ordered the rest ?? Antimatter (the positron) found by Diracin his equation, and observed by AndersonMuon (heavy electron) appears incosmic rays.
1680- Era of Light ~1680 : corpuscular theory of light~1800: wave theory of light~1873: electric and magnetic interactions propagate as a wave in vaccum-> light~1895 X-rays discovered 1905 electromagnetic radiation appears to be quantized~1923 X-rays behave like particles- photons. The first field quantum established.
1920-1940 : There must be other forces in Nature.. Nucleus must be held together by some strong interaction.Weak interactions and charges proposed to explainbeta decay
1953-1964 The Particle Explosion1953- Proliferation of discoveries of new , strongly interacting particles. Some ordering principle was badly needed.1953-1957 Substructure revealed insideprotons and neutrons. In spite of that, theywere still regarded as elementary.... 1962 - 1995 Towards the Family Picture
1964 -Quarks (3) were proposed to build strongly interacting particles. Quarks were searched for and not found- the concept was largely ignored 1968-69 semi-free, point-like particles found in the nucleons. They were named partons, in spite of being consistent with quarks
1953-1976 Strong Interactions Responding to Particle Explosion Main Stream Physicists study various theories of strong interactions: Regge poles, S-matrix theory, dispersion relations, hadron democracy, bootstrap models....
Important steps in the right direction in the corner...1964 Color property proposed for quarks,identified later with the charge of strong interactions1967-1973 Glashow-Weinberg-Salam model of electro-weak interactions was proposed, involving field quanta, W+-, Z and the photon. It needs another boson-the Higgs and a new type of neutrino interaction, which was later observed. The fourth quark-charmed proposed tokeep the model consistent with reality.QF theory proposed for Strong Interaction-with qluons as field quanta
Anna Lipniacka,
The L
HC
, initial physics
The Bright Universe , recent history
In 1994 LEP “measures” top quark masswith 15% accuracy. Tevatron, Fermilabreports 3σ evidence. Discovery reported in 1995
In 1977 , at FERMILAB, Chicago, theparticle composed from b (bottom) quark and b antiquark was discovered.
In 1976 the τ lepton was discovered at Stanford, California. This was a completely unexpected discovery, since the two knownfamilies were already "complete".
Perhaps there are much more families, with light neutrinos associated with them ???
ν τ ν4
ν5 ν6..
LEP says NO to New Familiesand to ...many new particles
Anna Lipniacka,
The L
HC
, initial physics
Amazing Weak Interactions
The only known interactions which need massive field quanta, to explain the shortrange of the interactions at low energies.
The only know interactions in which scattered particle can change to something else:
ν µ W+ d u
-g
2
g
2
Or perhaps it really does not ? From the point of viewof CC Weak Interactions neutrino and muon are justdifferent "spin" states of the same particle, "muontrino"But there is a difference between these "spin" states, the mass.....
How do you make two spin states to look different? If the space was a ferromagnet, there would be spontaneous magnetic field (B) there, and it would make spins "along" and "anti along" B look different.
The Higgs mechanism is a spontaneous "higgsization" of the space, which makes the muon and the neutrino look different
Energy
magnetization
B B
Anna Lipniacka,
The L
HC
, initial physics
The Higgs
The only known example so far:
Peter Higgs, professor emeritus at Edinburgh
Anna Lipniacka,
The L
HC
, initial physics
Dark Matter from SUPERSYMMETRY?
Symmetry between "Particles of Bodies" and "Agents in Nature "
Asks for three spin=0 "shadow" Sfermion families and for spin=1/2 field quanta (Inos).Mirror families have the same interaction charges as usual families. Thus the Minimal Supersymmetric Standard Model looks very much like the Standard Model, it does not contradict present precise verifications, if sparticles are heavier than ~50 GeV.
Mirror families and interactions
~
~~
~~
~
~
~
~~
~
~
S
SS
gluinos
winos, zinos
photinosLightest Supersymmetric Particleis an ideal Dark Matter Particle.
Still, many years of searching for it
Anna Lipniacka,
The L
HC
, initial physics
Golfand, Likhtman, JETP Lett. 1971Volkov, Akulov, Phys.Lett. B, 1973Wess, Zumino, Nucl. Phys. B, Phys. Lett. B, 1974
The main phenomenological motivation for SUSY comes from the problematic Higgs sector of the Standard Model: radiative corrections to Higgs mass are unnaturally large, if Standard Model is valid to large energy scales.
[ ] ...8
1 22
2
2 +Λ−= fermionscalarhm λλπ
δ
scalarλ
hhh h
fermionλ fermionλ In SUSY, the mass correction proportional to SUSY breaking.
SUPERSYMMETRY and Higgs boson(s)
Higgs boson “glues” so strongly to virtual top quarks, that it becomesheavy.. we need scalar stop quark to screen it.
There are 5 Higgs bosons in MSSM, the lightest one is lighter than ~130 GeV
2
In the Standard Model particles get masses by gluing themselvesto the Higgs field in the vacuum.
Anna Lipniacka,
The L
HC
, initial physics
any→∝Ω
χχσχ(
1
v
X
level) at σ2( 129.0094.0 2 ≤Ω≤ hCDM
h=0.70−0.030.04
Particle physics candidates for dark matter:
Neutrinos
Axions
Supersymmetric candidates:- neutralinos - sneutrinos- gravitinos- axinos
Kaluza-Klein states
... and many more ...
X
The Dark Side
Anna Lipniacka,
The L
HC
, initial physics
Before the LHC ,LEP searched for Higgs and SUSY...And?
DELPHIL3
ALEPH OPAL
Four experiments-laboratories: ALEPH,DELPHI, L3 and OPAL were recording the collisions.
Large Electron-Positron Collider, 27 kmlong, largest accelerator ever built.
Electron and positron beams crossed in LEP
10 times in 1989-2000 (start and end ).
Energy in Elementary Collisions:in 1989-1995:CMS Energy: 91 GeV (mass of Zr nucleus)in 1995-2000:CMS Energy 130-208 GeV ( Cs-Pb nuclea)
The energy of electrons exceeded their mass200 000-400 000 times - like it was 0.1 nsec after the Big Bang.
12
Anna Lipniacka,
The L
HC
, initial physics
LEP , the initial model of Large Collaboration
~1500 physicists in ~150 scientific institutions in Europe, Americas, Asia, Australia, Africa,New Zealand.
ALEPH, DELPHI, L3 and OPAL Collaborations
Built four detectors of ~1000 cubic meters each, comprising several millions of electronic channelsand spent two million person-hours "baby sitting" them.
analyzed several millions of "events" of electron-positron collisions,and wrote several millions of lines of programming code
Published more than 1200 papers in refereed scientific journals, ~400 doctorate theses, ~5000public scientific (conference) notes Life of LEP:
First Idea: 1976 Beginning of the construction : 1983 Largest European civil engineering Project in 1983-88 Start data taking : 13 of August 1989 End data taking : November 2000 Consumed 0.01% electricity of Europe, less power consumption than of a flying Jumbo-Jet
The data are STILL ! being analyzed forscientific publications, and in educationalprojects
Anna Lipniacka,
The L
HC
, initial physics
DELPHI at LEP, obituary, after dismantling
Hadroniccalori-meter
Tracking detectors
Electro magnetic calorimeter .
magnet, super-conductingweight 2500 t, used 890 l of liquidhelium
Anna Lipniacka,
The L
HC
, initial physics
LEP1, there must be New Particles
(strong)
(weak)
(EM)
-1
-1
-1
Vacuum polarization effects make all the charges (coupling constants) energy (distance)dependent. Also the electric charge "runs"due to screening, thus decreases with distance
LEP precise measurements revealed that chargesnot really unify at small distances (high energy)
em M Z =1
127.8±0.2
1137
atomic ,eV
sin2 W =0.2333±0.0008
strong M Z =0.113±0.003
Vacuum polarization effects depend on whichparticles are there to "polarize" the vacuum.
Scenario of GRAND DESERT does notwork for Grand Unificationlog of energy scale
Anna Lipniacka,
The L
HC
, initial physics
LEP1, evidence for supersymmetry ?
Charges of Electromagnetic, Weak and Stronginteractions unify at small distances (high energy ) if we introduce SUSY (MSSM)with mass ~ 1 TeV.
or
-log(R) [fm]
Unification occurs at 10 GeV, high enough toavoid problems with proton decay.
16
So 10 s after the Big Bang all fermions and sfermions had interaction charge of around 2.3 of present day electron charge.
-40
Anna Lipniacka,
The L
HC
, initial physics
LEP1.5, Rb and the Dark SideAround 21.5% of Z boson decays to quarks are to b b (Rb) .
In 95' due to small changes in the numbers, the measured value Rb appeared 3.7 σ away from the SM prediction. This could mean SUSY !
Z b
b
-
Winomass
stopmass
Z b
b
-
wino
stop
If SUSY, stop and wino had to be lighter than 80 GeV
And LEP machine was about to raise CM energyfrom 91 to 130-140 GeV , to test newly installedcavities, and prepare for higher energy run.
LEP 1.5:
favored corner..
Z/γe+
e-
W
W
10
10
Major backgroundto Wino productionis WW production andit is absent below160 GeV CM.We expected tosee WINO at 130-140!
Anna Lipniacka,
The L
HC
, initial physics
( 2) LEP1.5, Rb and the Dark Side
Soon after LEP switched on for the FIRST TIME to higher energies we saw this event:
e+
e-
beam µ−
Could these be Wino production?
Z/γe+
e-1
0W
For Wino decays itis more probable thatproduced charged lep-tons are of different fla-vour and go more"back to back".
e+W 2
0
Z/γe+
e-1
0
It could be associatedproduction of neutral bosons partners (Zinos,Higgsinos), which we need to give 23% of the mass of the Universe
as Dark Matter
20
10
DM particles
The Dark Side of the story was, that we did not see any more of these in a while... and Rb came slowly back to SM value, after understanding better ADLO correlated systematics
Anna Lipniacka,
The L
HC
, initial physics
Sparticle production at LEP-life was simple !
e+ e-W - W +q q ' q q '
e+ e- - +W + W -00
e+ e- 20 1
0 10 1
0e+ e-W - W +-+
e+ e- 10 1
0e+ e- - +W + W -00
e+ e- Z /Z *q qe+ e- Z /Z *q q
e+ e- 20 1
0 10 1
0 q q
Anna Lipniacka,
The L
HC
, initial physics
Limits on the Higgs boson Putting all electroweak measurements together we could determine preferred valueof the mass of the Higgs boson (LEP, Tevatron)
M Higgs=91−3245 GeV ,
M Higgs205 GeV 95% CL
Why did not we see the Higgs in direct searches at LEP ?
Z h
Z
e
e
b
b
q , ν, l
q ,ν ,l
-
- -
-
++
M =116
M Higgs114.1GeV
Small, 1.7σ "excess" consistent with M = 116 GeV
H
Q=L(S+B)/L(B)
Anna Lipniacka,
The L
HC
, initial physics
The Dark Side of LEP
LEP found neither supersymmetry nor Higgs bosonbut surprisingly(?) made them more plausibleThanks to precise measurements at LEP, Tevatron,neutrino experiments, we know:
The Higgs boson is light ( as SUSY would like it)
Light SUSY makes for unified gauge couplings
We have explored large living space of Higgs bosonand SUSY and this was quite difficult. Perhaps this wasone of the reasons to do it ?
The Dark Side is here and we have to continue the exploration
Anna Lipniacka,
The L
HC
, initial physics
Why LEP reached only 208 GeV?
Thus looked “only” to the 10 s after the Big Bang ? -10
Radiated energy at 100 GeV / beam: 4.2 GeV /turn/particle 40KW “shining” into your equipment RF power not sufficient to increase energy
Synchrotron radiation:
Charged particle emits radiation whenmoving on a “circle” --> accelerating
E radiated
t≃q a2≃
pm0
4 q2
R2
E radiated / turn≃Em0
4 q2
R
Anna Lipniacka,
The L
HC
, initial physics
What can we do to increase the energy?
Take heavier particles? -> protons --> Large Hadron Collider
Increase R ? --> go “linear” --> ?TESLA example2X15km accelerating sections21,024 X 1m SC cavities (2K)1.2 GHz , 23-35 MV/m
Project cost : 3000 MEURO---cavities : 1000 MEURO
Anna Lipniacka,
The L
HC
, initial physics
The price to pay for protons
Protons are composite objects:
d u
du
u- d
u
du
u-
7000 GeV 7000 GeV
They are full of gluonsquarks and antiquarks,
Each of them carries mostof the time only a very smallfraction of the proton energyCollisions with 14000 GeVenergy will nearly never occur
p p
Collisions with energy > 1000 GeV will occur 10 - 10 of cases
Collisions with energy > 3000 GeV will occur 10 - 10 of cases
-7 -6 -9 -8
And only some of them will lead to something interesting
Design choice: 40 MHz beam crossing rate (25 ns), 10 protonsper bunch , ~18 collisions / beam crossing -> GHz event rate
11
Anna Lipniacka,
The L
HC
, initial physics
The Puzzle
10 cm
18 superimposedpp collisions inthe internal part ofthe CMS centraltracker
Among them 4energetic muonsfrom decay of a heavy particle(Higgs boson)
Find them !
Anna Lipniacka,
The L
HC
, initial physics
The solution
Reconstructed trackswith momentum above 2 GeV/c
Among them fourmuons from thedecay of the Higgs particle
Anna Lipniacka,
The L
HC
, initial physics
Rate of events at the LHC
total collision
Dark matter production
Interesting “bangs” will at most one ina million
100 Hz to “tape”
Anna Lipniacka,
The L
HC
, initial physics
Online selection challenge
Anna Lipniacka,
The L
HC
, initial physics
Trigger and Data Acquisition challenge
Anna Lipniacka,
The L
HC
, initial physics
Needle in a hay stack ?
Imaginea spam filteras good asthis
Anna Lipniacka,
The L
HC
, initial physics
Initial physics
-Lots of “spectacular” Standard Model processes :tt production, (W, Z +jets) production, b-jets. Used for“callibration”
-If there is supersymmetry, it can be seen pretty soon.
-Search for Higgs boson production is a must- even ifit needs more than just “initial” data to be visible
Anna Lipniacka,
The L
HC
, initial physics
Triggering on data samples for calibration and control
Wellknown, clean processes from standard trigger menu: e.g.
Z → ee : ECAL intercalibration, absolute Escale, etc. Z → µµ : pscale in tracker and Muon Spectrometer, etc. tt → b ν bjj : absolute jetscale from W → jj, btag performance, reconstruction of complex final states (for ttH), etc.
~ 6 x 104 evts/day after cuts
~ 104 evts/day after cuts, S/B ~ 65
Additional lowerthresholds samples needed (esp. at the beginning) → prescaled triggers
• Minimumbias events : pp interaction properties, MC tuning, LVL1 efficiency, radiation background in Muon chambers, etc.
• QCD jets (20. ET . 400 GeV) : QCD crosssections and MC tuning, trigger efficiency, calorimeter intercalibration, jet algorithms, background to SUSY, etc.
• Inclusive e± pT > 10 GeV : trigger efficiency, ECAL calibration, ID alignment,
E/p, e± reconstruction at lowpT, etc.
• Inclusive µ± pT > 6 GeV : trigger efficiency, µ± reconstruction at lowpT,
ID alignment, Eloss in calorimeters, etc.
~ 107 events per sample
Rate : ~ 10 Hz/sample first weeks~ few Hz/sample under normal operation
These are few examples …
however, we will get 10**6 per samplealready 1st day-> we need fast feed-back!
Anna Lipniacka,
The L
HC
, initial physics
• Initial luminosity is now Lpeak = 2 x 1033
• LHC Computing Review• HLT/DAQ deferrals (Bphysics …)
Total trigger rate to storage reduced
from ~ 270 Hz at 1 x 1033 (HLT/DAQ TP, 2000)
to ~ 200 Hz at 2 x 1033 (now)Event size reduced from 2.4 MB to 1.6 MB
Selection (examples …) Rate at 2x1033 (Hz) Physics motivations (examples …)
e25i, 2e15i ~ 40 (55% W/b/c → eX) Lowmass Higgs (ttH, H→ 4 , qqττ) µ20, 2µ10 ~ 40 (85% W/b/c → µX) W, Z, top, New Physics ? γ60i, 2γ20i ~ 40 (57% prompt γ) H → γγ, New Physics
(e.g. X → γ xx mX~ 500 GeV ) ?j400, 3j165, 4j110 ~ 25 Overlap with Tevatron for new
X → jj in danger …j70 + xE70 ~ 20 SUSY : 400 GeV squarks/gluinosτ35 + xE45 ~ 5 MSSM Higgs, New Physics
(3rd family !) ? More difficult high L 2µ6 (+ mB ) ~ 10 Rare decays B → µµX
Others ~ 20 Only 10% of total ! (prescaled, exclusive, …) Total ~ 200 Hz No safety factor included. “Signal” (W, γ, etc.) : ~ 100 Hz
trigger list+constraints
Anna Lipniacka,
The L
HC
, initial physics
Knowledge of SM physics on day 1 ?
W, Z cross-sections: to 3-4% (NNLO calculation → dominated by PDF)
tt cross-section to ~7% (NLO+PDF)
LHC ?
<Nch> at η =0 for generic
pp collisions (minimum bias)
Candidate to very early measurement:
few 104 events enough to get dNch/dη, dNch/dpT
→ tuning of MC models
→ understand basics of pp collisions, occupancy, pileup, …
— AlpGen
Lot of progress with NLO matrix elementMC interfaced to parton shower MC(MC@ NLO, AlpGen,.. )
Anna Lipniacka,
The L
HC
, initial physics
Commissioning ATLAS detector and physics with top events, background study
σtt (LHC) ≈ 250 pb
for goldplated semileptonic channel
Can we observe an early top signal with limited detector performance ?Can we use such a signal to understand detector and physics ?
YES !
TOP CANDIDATE
W CANDIDATE
use simple and robust selection cuts: pT (l) > 20 GeV
ET miss > 20 GeV ε ~ 5%
only 4 jets with pT > 40 GeV
no btagging required (early days …)
m (top → jjj) from invariant mass of 3 jets giving highest top pT
m (W→jj) from 2 jets with highest momentum in jjj CM frame
Total efficiency, including mjjj inside mtop
mass bin : ~ 1.5% (preliminary and conservative …)
m (top→jjj)
B
S
S/B = 0.45
m(W→jj)
S/B = 1.77
L=300 pb-1
m (top→jjj)
Expect ~ 100 events inside mass peak for 30 pb-1 → top signal observable in early days with no b-tagging and simple analysis
tt is excellent sample to: -- commission b-tagging, set jet E-scale using W → jj peak and W-mass contraint -- understand detector performance and reconstruction tools for many physics objects
(e, µ, jets, b-jets, missing ET, ..)
-- understand / tune MC generators using e.g. pT spectra
W+jets background can be understood with MC+data (Z+jets)
S : MC @ NLOB : AlpGen x 2 to account for W+3,5 partons (pessimistic)
|mjjmW| < 10 GeV
Bentvelsen at al.
Anna Lipniacka,
The L
HC
, initial physics
Dark Matter production in the ATLAS detector
Can we see it ?
LHC: hadronic cascades:
leptonsjetsE
qgqqggpp
missT ++→
→
~~,~~,~~
g~b
b~
b
02
~χ 01
~χl
±l±l
~
Anna Lipniacka,
The L
HC
, initial physics
Can we see “generic” Dark Matter production ?
A DM production model
qq,tt,VVWX,ZX
GeV
The “transverse momenta” of all produced particles should sum up to zero- momentum conservation. Weakly interacting DM particles will not be detected-> “missing transverse energy”
Anna Lipniacka,
The L
HC
, initial physics
Seeing The Dark (Matter)
~ 1 day : up to 1.5 TeV
~ 10 days : up to 2 TeV
~ 100 days : up to 2.3 TeV
Fantasy plot?
But allowed x-sectionsare still large and it wouldbe pity to miss SUSYDark Matter if it isthere.
Many signatures providean interesting focus forthe start-up time.
Anna Lipniacka,
The L
HC
, initial physics
What do we need to see SUSY in "10 days"?
- Calorimeter working down to η<5 with no "holes". Otherwise "instrumentalmissing Et is too large.
ATLAS study : full simulation of Z + jet(s) events, with Z → µµ and pT (Z) > 200 GeV
reconstructed MET spectrumIf leading jets undetected
2 events with MET > 200 GeVcontain a highpT neutrino
Events with MET > 50 GeV
“crack” barrel/ extended barrel Tilecal
Particles parallel to Tilecal scintillating tiles
Anna Lipniacka,
The L
HC
, initial physics
Main backgrounds to SUSY searches in Jets + MET topology at Hadron Colliders from:
-- W/Z + jets with Z → νν, W → τν ; tt; etc. -- QCD multijet events with fake MET from jet mis-measurements (detector resolution, cracks)
CDF, 84 pb1 , MET >70 GeV + ≥ 3 jets sample
Data : 74 events SM prediction : 76± 13 events (35 W/Z/tt + 41 QCD)
Missing ET (GeV)
Understanding the missing ET spectrum (and tailsfrom instrumental effects) is one of most crucial and difficult experimental issues for SUSY searches at Hadron Colliders
Can we calibrate missing ET (MET) with 1/fb ?
But here CDF manages to understandmissing Et with ~0.1/fb, we shouldhave this in 2007!
Anna Lipniacka,
The L
HC
, initial physics
Susy model parameters
Anna Lipniacka,
The L
HC
, initial physics
One possible focus, “stau co- annihilation”
“End-points factory” in Bergen and Oslo
01
~χ τ
τ~ γτ~
stau-LSP
129.0094.0 2 ≤Ω≤ hχleptonsjetsE
qgqqggpp
missT ++→
→
~~,~~,~~
g~b
b~
b
02
~χ 01
~χl
±l±l
~
taus
tau
stau tau
11 fb -1
Tau reconstruction, nice collaboration between tracking and all calorimeters. Improving the “official” ATLAS one.
Anna Lipniacka,
The L
HC
, initial physics
The Higgs boson
Anna Lipniacka,
The L
HC
, initial physics
Anna Lipniacka,
The L
HC
, initial physics
Gluon fusion channel
Anna Lipniacka,
The L
HC
, initial physics
Anna Lipniacka,
The L
HC
, initial physics
Anna Lipniacka,
The L
HC
, initial physics
Anna Lipniacka,
The L
HC
, initial physics
Anna Lipniacka,
The L
HC
, initial physics
Many challenges of the LHC
Radiation hardness of detectors an electronicsPrecision manufacturing, positioning, monitoring of largescale detectorsReliability and quality assuranceof multi-component, long lifetime systemsLarge scale cryogenicsThese challenges are being met !
MANAGEMENT challenge
Last but not least: The Data Challenge
ATLAS will produce 1200CDs of “to tape” real data/minute. Close to 1000CDs/Atlas member/day. We need simulated data in addition.How to handle this ?
Anna Lipniacka,
The L
HC
, initial physics
Production System Architecture
PANDA
Common Executor
CondorG
II
DQDQDQDQ
Eowyn
Is this simpler than SUSY ?
~ 7000 cpu's ~ 3000 cpu's
~ 5000 cpu's (800 for Atlas)
(management)------------------------------ <<1(people doing real work)
Anna Lipniacka,
The L
HC
, initial physics
More on Atlas in Norway
STEP project provides a tool which transports or propagates track parameters and the associated uncertainties ("errors") through regions with inhomogeneous magnetic fields and potentially large amounts of material
Level 6 of HS on US side
SCT type IV cables
15% of SCT modules in SC
QCD, EW, B-physics, top, Higgs, SUSY, Exotics, MC generators, tau performance,
A beamgas event in ATLAS (full sim.)
Beamhalo muons in ATLAS (full sim.)
Trigger ?
Scintillator counters inside ID cavity, in front of endcap cryostats (replacing part of moderator),
covering R=15→ 90 cmProvide trigger on beamhalo at low R (TGC at large R), beamgas, andminimum bias for initial LHC operation
Anna Lipniacka,
The L
HC
, initial physics Why do we need football?
Why do we need particle physics?
Why do we need Physics at all ? Yes, electricity, WWW, CD, TV etc etc
Physics (and Particle Physics) has a cultural dimension like Art.
It is a guardian of Scientific Method and Scientific Thinking.
Physics is a romantic adventure of discovering New Lands and a great educational magnet.
This isthe formulafor gravitation
No questions, we continue
But I HAVE a question!
What IS gravitation!WHY bodies attracteach other ?
This will not be on the exam..
So you do not know!
This onlyI know..
Perhaps we need to teach it in a different way
But why do we need football ?
We need people who ask question! What are your assumptions? What is your method? How did you check these? What is the probability of success?We need more physics students!
Anna Lipniacka,
The L
HC
, initial physics
What will happen in the next 7 years?After 8 years of Tevatrons RunII and 2 years of the LHC....
Lets play the "scenarios" game.....
htop
stop
h
The TeVatron finds the Higgs, mass below 135 GeV. Can this be the Standard Model Higgs boson? Fine tuned mass or New Physics at ~1 TeV
For example SUSY, to cancel top loops with stops
The "funding agencies" scenario...
M h=M h New Physics Scale+−New Physics Scale2
Can we get a hint on the SUSY scale ?
We measure better the top quark mass and the W mass at the Tevatron, and determinethe SUSY scale to be around 1 TeV. We are swamped with sparticles at the LHC.
We publish first Sparticle data book and consider machines to study Supersymetry breaking.
Anna Lipniacka,
The L
HC
, initial physics
LHC, the brave New World
CMS energy in proton proton collision 14 TeV , beam collision rate 40 MHz.
proton-proton
2007
-1
Proton -Proton collision, 14 TeV CM, 40 MHz beam crossing rate:
8-80 millions of tt events per year/experiment-
CMS energy in elementary gluon-gluon collisions:> 1 TeV at 10 -100 Hz > 3 TeV at 0.1- 1 Hz
bb rate ~ 0.1 MHz -
2-20 thousands WH events per year/experiment
New Physics:If below ~4 TeV will be observed after few years of running.
Rare Decays:Example : SM will be observable after 2 years of lower luminosity run.SUSY ( 1 TeV) predicts
Br Bs~10−9
Bs~10−8
OLD ~115 GeV Higgs boson?5 σ signal after 1 year of running50% of sensitivity in h -> γγ
Luminosity 10-100 fb per year/experiment
Anna Lipniacka,
The L
HC
, initial physics
In the realm of WW
LEP 1.5 soon grown up to become LEP2, and with CM energies above 160 GeV we couldproduce WW pairs, measure WW cross-section and W mass.
Textbook result: Massive cancellations betweenamplitudes, required by electroweak theoryprecisely veryfied.
While we continued looking for Winoand other Ino's pair production, with negative results...