Kap 4 Heavy Quarks Physics Introduction and overview

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 WS 2007/08: Physik am LHC 1

Motivation Heavy Quarks are improtant tools for: ● Exploring the Big Band – ● Test of symmetry of forces – ● CP-violation Kosmology – ● Quark-Gluon-Plasma (LHC: ALICE) dark Matter Structure of strong and weak interaction ● – Strong coupling constant – Quark-Mixing-Matrix Search for new Physic (Beyond Standard Model) – Precission measurements Martin zur Nedden, HU Berlin WS 2007/08: Physik am LHC 2

Quarks and Leptons Masses in Me. V CHARGE the top-Quark mass Is huge (175 Ge. V) … 0 -1 +2/3 -1/3 Martin zur Nedden, HU Berlin WS 2007/08: Physik am LHC 3

Particles with heavy Quarks • “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 • B 0 J/Ψ + X : well measurable decay length • b c + μ + υμ : well measurable impact parameter Martin zur Nedden, HU Berlin WS 2007/08: Physik am LHC 4

Decays of heavy Quarks semi-leptonic decay hadronic decay into a CP-Eigen state: without B 0 - Oscillation Martin zur Nedden, HU Berlin WS 2007/08: Physik am LHC with B 0 - Oscillation 5

Methods of b-tagging momentum of myons relativ to Jet-Axix: ptrel based on Jet (calorimeter) and MYON information: b-Jet pp B+B- XY semi leptonic b quark decay Decay length of B-hadrons: track- und vertex-information necessary: pp bb X J/ψ XY XY measurement of secundary vertices Martin zur Nedden, HU Berlin WS 2007/08: Physik am LHC 6

Reconstruction of decay vertices experiment D 0 (Tevatron): Z bb Martin zur Nedden, HU Berlin WS 2007/08: Physik am LHC 7

Production of heavy Flavours Parton-Density Fuctions Partonic cross section Hadronization: formation of hadrons with heavy quarks faktorisation Production in hadronic interaction Martin zur Nedden, HU Berlin WS 2007/08: Physik am LHC 8

Reconstruction of the Decay Length deca L= Martin zur Nedden, HU Berlin WS 2007/08: Physik am LHC 9

Impact-Parameter in b-flavourd Jets Martin zur Nedden, HU Berlin WS 2007/08: Physik am LHC 10

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 WS 2007/08: Physik am LHC 11

b-Reconstruktion from 2 -Muon events Martin zur Nedden, HU Berlin WS 2007/08: Physik am LHC 12

b production-cross section at TEVATRON Martin zur Nedden, HU Berlin WS 2007/08: Physik am LHC 13

Pseudo-Proper time of the J/ψ Martin zur Nedden, HU Berlin WS 2007/08: Physik am LHC 14

J/ψ for B-Hadron Identification at CDF Martin zur Nedden, HU Berlin WS 2007/08: Physik am LHC 15

Search for Toponium… Martin zur Nedden, HU Berlin WS 2007/08: Physik am LHC 16

Discovery of the top-Quark 1995 at TEVATRON in Proton-Antiproton interactions Martin zur Nedden, HU Berlin WS 2007/08: Physik am LHC 17

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 WS 2007/08: Physik am LHC 18

Observation in the Muon-Channel Lep 1 L Martin zur Nedden, HU Berlin WS 2007/08: Physik am LHC 19

Observation in the Electron-Channel 2 Lepton channel: 2 L + 2 b-J + 2 MET Martin zur Nedden, HU Berlin WS 2007/08: Physik am LHC 20

Observation based on Jets Jet channel: 4 J + 2 b-J Martin zur Nedden, HU Berlin WS 2007/08: Physik am LHC 21

Top-Event-Displays von D 0 (Tevatron) 2 with Jets Martin zur Nedden, HU Berlin WS 2007/08: Physik am LHC 22

Top-Eventdisplays of D 0 (Tevatron) WS 2007/08: Physik am LHC e wiht 4 Jets Martin zur Nedden, HU Berlin 23

Example of a 2 -myon Event Martin zur Nedden, HU Berlin WS 2007/08: Physik am LHC 24

Signal/Background in top/Anti-top production Top events are multi jet events Martin zur Nedden, HU Berlin WS 2007/08: Physik am LHC 25

Top mass reconstruction Martin zur Nedden, HU Berlin WS 2007/08: Physik am LHC 26

Mean Value of the Top-Mass (TEVATRON) Martin zur Nedden, HU Berlin WS 2007/08: Physik am LHC 27

Cross Section Measurement Martin zur Nedden, HU Berlin WS 2007/08: Physik am LHC 28

Mean Value of Top-Production Cross Section Martin zur Nedden, HU Berlin WS 2007/08: Physik am LHC 29

Heavy Quarks at LHC • big bb productions-XS: ~ 500 µb (~ 1 bb pairs per 100 p-p collisions) • high tt production-XS: ~830 pb (~ 80. 000 tt pairs per year) – LHC is a top-factory – important tool for detectorcalibration 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-2 s-1 (~100 fb-1 per year) Martin zur Nedden, HU Berlin WS 2007/08: Physik am LHC 30

General Strategy for B Physics at LHC • General-purpose experiments for discoveries: main emphasis on high-p. T 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 , 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 WS 2007/08: Physik am LHC 31

Trigger Strategies for B-Physics • • • ATLAS -rates for 14 Te. V and 10 cm s limited bandwidth for B-triggers: highly efficient and selective trigger needed. h (hadron) c- and b-events contain mostly low p. T particles: all single- b (beauty) challenge to trigger on those events c (charm) many b-decays contain J/ψ : J/Y useful for calibration, optimization and understanding of detector, trigger as well as B-physics 33 • 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-2 s-1) • LVL 1 single -trigger with additional LVL 1 signature or a jet in calorimeter at LVL 2 • use LVL 1 Regions of Interest (Ro. I) to seed LVL 2 reconstruction: • Jet Ro. I: for hadronic final states (e. g. Bs → Ds( π)π) • EM Ro. I: for e/g final states (e. g. J/ψ → ee, K*γ, γ) • Muon Ro. I: to recover di-muon final-states in which second muon was missed at LVL 1 • LVL 1 di-muon trigger • high lumi (>2 x 1033 cm-2 s-1) • LVL 1 di-μ trigger • B → J/ψ( ) , rare decays (B → , B K 0*μμ), double semi leptonic decays Martin zur Nedden, HU Berlin WS 2007/08: Physik am LHC -2 -1 all di- 32

Searches: Rare B-Decays 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 effects determination of the |Vtd| and |Vts| some of the rare decays as background to other rare decays (for example Bd 0 + - as bkg for Bd, s + - ) Bs μ+μ- Martin zur Nedden, HU Berlin WS 2007/08: Physik am LHC 33

Example: ATLAS offline analysis for Bs Expected signal v. s. inclusive bb μμX background Cuts p. T>6 Ge. V, ΔR <0. 9 M cut (Mμμ = MBs+140 -70 Me. V) B 0 s signal BG (bb X) 50 events 6. 0× 106 events 0. 77 2× 10 -2 0. 36 5× 10 -2 0. 4 < 0. 7× 10 -4 7 20± 12 Isolation cut: no charged tracks with p. T > 0. 8 Ge. V in cone q < 15 degrees Lxy/s(Lxy)>11, c 2<15 (transverse decay length) vertex fit with pointing to primary vertex constraint All cuts Background: Martin zur Nedden, HU Berlin WS 2007/08: Physik am LHC 34

Projected upper limits: Bs extraction of upper limit on Br(Bs μμ) (from 7 signal and (20± 12) background events) ATLAS experiment expects to reach the sensitivity of SM prediction Tevatron projection Still factor of 10 above Martin zur Nedden, HU Berlin The measurement of Bs μμ is still feasible at nominal LHC luminosity 1034 cm-2 s-1. This would mean 100 fb-1 just in one year. WS 2007/08: Physik am LHC 35

Top-Decay channels charakteristic Signal: Lepton + missing energy only Jets in final state: dominant BG from QCD-multijet-events Martin zur Nedden, HU Berlin WS 2007/08: Physik am LHC 36

Top – Physics at LHC/ATLAS ● measurement of the top-Quark mass – ● pairproduction of top-Quarks – ● using mt = mjjb (mjj = m. W) Tag via leptons and ETmiss 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 WS 2007/08: Physik am LHC 37

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-Fusion t-Kanal Martin zur Nedden, HU Berlin Direkte Produktion, Wt-Prozess WS 2007/08: Physik am LHC W*-Prozess s-Kanal 38

Connection of W- and Top-Masse Martin zur Nedden, HU Berlin WS 2007/08: Physik am LHC 39