Martin zur Nedden, HU Berlin 1WS 2007/08: Physik am LHC
Kap 4: Heavy Quarks Physics
• Introduction and overview
• Measurement of heavy quarks
• Production of Heavy Quarks at TEVATRON:– b-selection methods– Cross section measuremtens
• Top search and mass measurement at TEVATRON
• Heavy quarks at LHC– BSM searches with rare B-decays– Top physics at LHC
Martin zur Nedden, HU Berlin 2WS 2007/08: Physik am LHC
Motivation
● Exploring the Big Band
– Quark-Gluon-Plasma (LHC: ALICE)
● Test of symmetry of forces
– CP-violation
● Kosmology
– dark Matter
● Structure of strong and weak
interaction
– Strong coupling constant
– Quark-Mixing-Matrix
● Search for new Physic (Beyond Standard Model)
– Precission measurements
Heavy Quarks are improtant tools for:
Martin zur Nedden, HU Berlin 3WS 2007/08: Physik am LHC
Quarks and Leptons
Masses in MeV
0
-1
+2/3
-1/3
CHARGE
the top-Quark mass Is huge (175 GeV) …
Martin zur Nedden, HU Berlin 4WS 2007/08: Physik am LHC
• “Hidden” Flavours: States wiht Quarks and corresponding Antiquarks• Analogy to Positronium• Spectroskopy of strong Interaction• c-Quarks: and excited states (Ψ’, χc, etc.)• b-Quarks: and excited states (Y’, Y’’, etc.)
• “Open” Flavours: States with other (light) Quarks/Antiquarks• c-Quarks: • b-Quarks:
• no bound states wiht top-Quarks• Decay channels
• J/Ψ , Υ e+e- , μ+μ- : easy to reconstruct• B0 J/Ψ + X : well measurable decay length • b c + μ + υμ : well measurable impact parameter
Particles with heavy Quarks
ccJ /
bb
etc. ,,0 dcDucD
etc. ,,, 00 ubBsbBdbB s
Martin zur Nedden, HU Berlin 5WS 2007/08: Physik am LHC
Decays of heavy Quarks
hadronic decay semi-leptonic decay
decay into a CP-Eigen state:
without B0 - Oscillation with B0 - Oscillation
Martin zur Nedden, HU Berlin 6WS 2007/08: Physik am LHC
Methods of b-tagging
momentum of myons relativ to Jet-Axix: ptrel
based on Jet (calorimeter) and MYON information: b-Jet
Decay length of B-hadrons:
track- und vertex-information necessary:
pp bb X J/ψ XY XY
measurement of secundary vertices
semi leptonic b quark decay
pp B+B- XY
Martin zur Nedden, HU Berlin 7WS 2007/08: Physik am LHC
Reconstruction of decay vertices
experiment D0 (Tevatron): Zbb
Martin zur Nedden, HU Berlin 8WS 2007/08: Physik am LHC
Production of heavy Flavours
ij
FRijFjFi dxdxppxfxf 2122
212
22
1 ),,,(ˆ),(),(
Production in hadronic interaction
Parton-Density Fuctions Partonic cross section
Hadronization:formation of hadrons withheavy quarks
faktorisation
Martin zur Nedden, HU Berlin 9WS 2007/08: Physik am LHC
Reconstruction of the Decay Length
decay length in the lab-system:
L = c t ß γ
Martin zur Nedden, HU Berlin 10WS 2007/08: Physik am LHC
Impact-Parameter in b-flavourd Jets
Martin zur Nedden, HU Berlin 11WS 2007/08: Physik am LHC
ATLAS Inner Detector (ID)
The Inner Detector (ID) is organized into four sub-systems:
Pixels (0.8 108 channels)Silicon Tracker (SCT)
(6 106 channels)Transition Radiation Tracker (TRT)
(4 105 channels)Common ID items
Martin zur Nedden, HU Berlin 12WS 2007/08: Physik am LHC
b-Reconstruktion from 2-Muon events
Martin zur Nedden, HU Berlin 13WS 2007/08: Physik am LHC
b production-cross section at TEVATRON
Martin zur Nedden, HU Berlin 14WS 2007/08: Physik am LHC
Pseudo-Proper time of the J/ψ
Martin zur Nedden, HU Berlin 15WS 2007/08: Physik am LHC
J/ψ for B-Hadron Identification at CDF
Martin zur Nedden, HU Berlin 16WS 2007/08: Physik am LHC
Search for Toponium…
Martin zur Nedden, HU Berlin 17WS 2007/08: Physik am LHC
Discovery of the top-Quark
1995 at TEVATRON in Proton-Antiproton interactions
Martin zur Nedden, HU Berlin 18WS 2007/08: Physik am LHC
Top-Decay Channels
Top production at TEVATRON dominated by quark – antiquark processes,At LHC by gluon-gluon interactions, decay channels are the same….
Martin zur Nedden, HU Berlin 19WS 2007/08: Physik am LHC
Observation in the Muon-Channel
Lepton + Jet channel:1 L + 2 J + 2 b-J + 1 MET
Martin zur Nedden, HU Berlin 20WS 2007/08: Physik am LHC
Observation in the Electron-Channel
2 Lepton channel:2 L + 2 b-J + 2 MET
Martin zur Nedden, HU Berlin 21WS 2007/08: Physik am LHC
Observation based on Jets
Jet channel:4 J + 2 b-J
Martin zur Nedden, HU Berlin 22WS 2007/08: Physik am LHC
Top-Event-Displays von D0 (Tevatron)
2 with Jets
with 4 Jets
Martin zur Nedden, HU Berlin 23WS 2007/08: Physik am LHC
Top-Eventdisplays of D0 (Tevatron)
e wiht 4 Jets
e with Jets
Martin zur Nedden, HU Berlin 24WS 2007/08: Physik am LHC
Example of a 2-myon Event
Martin zur Nedden, HU Berlin 25WS 2007/08: Physik am LHC
Signal/Background in top/Anti-top production
Top events are multi jet events
Martin zur Nedden, HU Berlin 26WS 2007/08: Physik am LHC
Top mass reconstruction
Martin zur Nedden, HU Berlin 27WS 2007/08: Physik am LHC
Mean Value of the Top-Mass (TEVATRON)
Martin zur Nedden, HU Berlin 28WS 2007/08: Physik am LHC
Cross Section Measurement
Martin zur Nedden, HU Berlin 29WS 2007/08: Physik am LHC
Mean Value of Top-Production Cross Section
Martin zur Nedden, HU Berlin 30WS 2007/08: Physik am LHC
• big bb productions-XS: ~ 500 µb (~ 1 bb pairs per 100 p-p collisions)
• high tt production-XS: ~830 pb (~ 80.000.000 tt pairs per year)
– LHC is a top-factory– important tool for detector- calibration and trigger comissioning
• Luminosity phases:– 2008: ~ 100 pb-1
– 2009: more than 1 fb-1
at an available luminosity of 1033 cm-2 s-1 (~10 fb-1 per year) – design: “High”-Luminosität: 1034 cm-2s-1 (~100 fb-1 per year)
Heavy Quarks at LHC
Martin zur Nedden, HU Berlin 31WS 2007/08: Physik am LHC
General Strategy for B Physics at LHC
• General-purpose experiments for discoveries: main emphasis on high-pT physics beyond the Standard Model
• B-physics programme depending on stages of the LHC operation:• Huge b-hadron production statistics allow precise measurements of their properties• Theoretical descriptions of heavy flavoured hadrons need input from LHC• Precision measurements already achievable after one year of data taking• Inclusive production cross section measurement in the initial phase
• Measurements extending the discovery potential for BSM physics measurements of CP violation parameters that are predicted to be small in the SM (e.g in Bs J/() )
measurements of rare B-decays (Bd K* , Bd K* , Bs , Bs , Bs , B )
• Focus on physics topics that will not be accessible for the B-factories mainly Bs, baryon and double heavy flavour hadrons (Bs Ds , Bs J/() , b J/0 , …)
Martin zur Nedden, HU Berlin 32WS 2007/08: Physik am LHC
Trigger Strategies for B-Physics
• limited bandwidth for B-triggers: highly efficient and selective trigger needed.• c- and b-events contain mostly low pT particles:
challenge to trigger on those events• many b-decays contain J/ψ :
useful for calibration, optimization and understanding of detector, trigger as well as B-physics
• B-trigger is based on single- and di-muons in final state BR ~ 10 %, but clean signature at early level in trigger and
give flavour tag
• lower lumi (< 2*1033 cm-2s-1) • LVL1 single -trigger with additional LVL1 signature or a jet in calorimeter at LVL2• use LVL1 Regions of Interest (RoI) to seed LVL2 reconstruction:
• Jet RoI: for hadronic final states (e.g. Bs → Ds(π)π)
• EM RoI: for e/ final states (e.g. J/ψ → ee, K*γ, γ)
• Muon RoI: to recover di-muon final-states in which second muon was missed at LVL1• LVL1 di-muon trigger
• high lumi (>2x1033 cm-2s-1)• LVL1 di-μ trigger• B → J/ψ() , rare decays (B → , B K0*μμ), double semi leptonic decays
all single-
all di-
h (hadron)b (beauty)c (charm)J/
ATLAS rates for 14 TeV and 1033cm-2s-1
Martin zur Nedden, HU Berlin 33WS 2007/08: Physik am LHC
b → d, s transitions (FCNC) are forbidden at the tree level in SM and occur at the lowest order through one-loop-diagrams “penguin” and “box”
Main points to study:
good test of SM and its possible extensions information of the long-distance QCD effectsdetermination of the |Vtd| and |Vts|
some of the rare decays as background to other rare decays(for example Bd0+- as bkg for Bd,s+- )
Searches: Rare B-Decays
Bsμ+μ-
Martin zur Nedden, HU Berlin 34WS 2007/08: Physik am LHC
Example: ATLAS offline analysis for Bs
Cuts B0s signal BG (bbX)
pT>6 GeV, ΔR<0.9 50 events 6.0×106 events
Mcut (Mμμ = MBs+140
-70 MeV) 0.77 2×10-2
Isolation cut:no charged tracks with pT > 0.8 GeV in cone < 15 degrees
0.36 5×10-2
Lxy/(Lxy)>11, 2<15
(transverse decay length)vertex fit with pointing to primary vertex constraint
0.4 < 0.7×10-4
All cuts 7 20±12
Expected signal v.s. inclusive bbμμX background
Background: lcl lBlBB ,,0
KKBKBBB sdsd ,,, 000
Martin zur Nedden, HU Berlin 35WS 2007/08: Physik am LHC
Projected upper limits: Bs
totalBs
bgs
nnNBBr
L2
,0
extraction of upper limit on Br(Bs μμ) (from 7 signal and (20±12) background events)
ATLAS experiment expects to reachthe sensitivity of SM prediction
Still factor of 10 aboveThe measurement of Bsμμ is still feasible at nominal LHC luminosity 1034cm-2s-1.
This would mean 100 fb-1 just in one year.
Tevatron projection
Martin zur Nedden, HU Berlin 36WS 2007/08: Physik am LHC
Top-Decay channels
bWt )JetJet( qqW
)Lepton( miss
ElW l
charakteristic Signal:Lepton + missing energy
only Jets in final state:dominant BG from QCD-multijet-events
Martin zur Nedden, HU Berlin 37WS 2007/08: Physik am LHC
Top – Physics at LHC/ATLAS
● measurement of the top-Quark mass– using mt = mjjb (mjj = mW)
● pairproduction of top-Quarks– Tag via leptons and ET
miss
● decay of top-Quarks– Branching ratios / coupplings– rare decays: t g//Z q (q=u,c: FCNC)
● Single top-Production● ideal “standard-candel”
– Detekctor calibration and trigger optimization
Martin zur Nedden, HU Berlin 38WS 2007/08: Physik am LHC
Single-Top Produktion
• direkte Bestimmung der Kopplungsstärke des t-W-b Vertex:• W-Gluon-Fusion: sensitiv auf Modifikationen der Kopplungen des top-Quarks an andere SM-Teilchen• Wt: sensitiv auf FCNC• W*: sensitiv auf neue, schwere W’-Bosonen
• wesentlich geringerer Anteil an der top-Produktion bei LHC
W-Gluon-Fusiont-Kanal
Direkte Produktion,Wt-Prozess
W*-Prozesss-Kanal
Martin zur Nedden, HU Berlin 39WS 2007/08: Physik am LHC
Connection of W- and Top-Masse
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