1

Heavy Quarks at the Tevatron

CDF

DOBottom

Barbro Åsman

Stockholm University

For the CDF and D0 Collaborations TO

P

Proton

Proton LISHEP 06

Rio de Janeiro

2

Golden Eggs

Mixing:

Bs, Bd

New particles:

X(3872), Xb,

Pentaquarks, …

Mass measurements:

Bc, b, Bs, …

Production properties:

(b), (J/y), …

B and D

Branching ratios

Rare decay searches:

Bs -> µ+µ-,

D0 -> µ+µ- , …

CP Violation

Lifetimes:

, b, Bs, Bc ..SURPRISES!?

3

HOW ?

Measuring b(udb) Lifetime

Lxy

PV

cLxy MB

PT

b

p

p

p

B0K0

WHY ? A ~2 Differance between theory and

experiment for (b)/(B0). Theory =

0.86 ± 0.05

xy-plane

4

b LifetimeExtract lifetime with unbinned likelihood fit to proper decay length and mass event information.

(b)=1.45 + 0.14 – 0.13 ± 0.02 (sys) ps

b)/(B0) = 0.944 ± 0.089

(b)=1.22 + 0.22 – 0.18 ± 0.04 (sys) ps

b)/(B0) = 0.87 +0.17

-0.14 ± 0.03

5

Bc Contains Two Heavy Quarks

Unique system with two heavy quarks of different flavor

Probes heavy-quark theories in the region between the cc and bb

Decays in 3 different ways: b or c decays or bc annihilation

Low production rate B+,B0: 40%,Bs,B baryons: 10%, Bc~ .05%

Reconstruct Bc J/e

6

Results

(Bc) = 0.474 + 0.073– 0.066 ± 0.033 (sys) ps

Bc)= 0.448 +0.123 – 0.096 ± 0.121 (sys) ps

Bc

Lxy

XY - plane

e

cLxy MB *K PT (vis)

Where K = PT(vis) / PT(B)

is given from MC

7

Review of B0 SystemIn the B0 system: physical mass eigenstates = flavor eigenstates

where:= H- L (lifetime difference)

= (H+ L)/2

m = mH- mL (mass difference)

BL = B0 + B0

BH = B0 - B0

Time evolution of the two states is governed by the time-dependent Schrödinger equation and in the limit

m

Prob (B0 -> B0) = ½ e-t(1+cosmt)

Prob (B0 -> B0) = ½ e-t(1-cosmt)

oscillation frequency( md , ms)

Ignoring CP violation

8

Extract from Bs K+K- lifetime

• Measurement of Bs -> K+K- lifetime (=L) in 360 pb-1

• Mass fit and lifetime fit:

•Extraction of (CP)/(CP):

•This measurement gives cL = 458 ± 24 ± 6 µm

•HFAG average gives weighted average: (L2 +H

2) /(L + H)

•Extract H

•Thus derive =-0.080 ± 0.23 (stat) ±0.03 (syst)

9

BS lifetime and Bs

0 -> J/

= 1.53 ± 0.08 +0.01 -0.04 ps

= 0.15 ± 0.10 +0.03 -0.04 ps

Gives rise to both CP-even and CP-odd

final states

10

Summary of

11

Bd and Bs Mixing

00H

00L

BqBpB

BqBpB

W W

b

d(s)

d(s)t

Vtb

Vtb Vtd(s)

Vtd(s)t b

md = (lots of QCD) x Vtd

ms = (lots of QCD) x Vtsms/md = (much less QCD ) x Vts /

Vtd

Vud Vus Vub

Vcd Vcs Vcb

Vtd Vts Vtb

V =

Vud Vub* + VcdVcb* + VtdVtb* = 0

VtdVtb*VcdVcb*VudVub*

VcdVcb*-

1

= Vtd

Vts

12

Analysis StrategyBs oscillations is more difficult than Bd oscillations because of the fast mixing frequency

In order to measure m:

Reconstruct the Bs signal

Know the flavor of the meson at its

production time (Flavor tagging) and

getD2 (tagging power)

Calculate Proper length resolution

S = signal events D2 = tagging pow er S/B = signal/background t = proper time resolution

13

Reconstruction Currently only using semileptonic decay of the Bs

Bs -> Ds X (Ds -> μD±: 7,422±281

μD±: 7,422±281

μDs: 26,710±560μD±: 1,519±96

μDs: 5,601±102

14

Flavor Tagging

Soft lepton

Soft Lepton Tagging ( or e ):

Charge of the leptons together with the jet charge gives the flavor of b

Jet Charge Tagging :

Sign of the weighted average charge of opposite B jet gives the flavor of b

Ds

Bs

b-hadronJe

t Char

ge

P.V.

Tagging SideVertexing Side

Secondary Vertex Charge

T

TEV p

qpQ

15

Cross Check of Tagging On a Bd sample

D2 = (2.48 0 ±.21 +0.08 -0.06 ) %

Tagger tuned using Bd mixing measurement

md = 0.506 ± 0.020 ± 0.014 ps-1

B0B+

)()(

)()()(

tNtN

tNtNtA

oscoscno

oscoscno

16

Bs Lifetime

Ds

Bs XY plane Lxy

cLxy MB *K PT (lD)

Where K = PT(lD) / PT(B)

is given from MC

17

Amplitude Fit Method

Prob (B0 -> B0) = ½ e-t(1+Acosmt)

Fit to data – A free parameter

Prob (B0 -> B0) = ½ e-t(1-Acosmt)

Fit for oscillations amplitude A

for a given m

Expect A = 1 for frequency = true ms

Expect A = 0 for frequency = true ms

If no signal observed :

Exclude ms value at 95% C.L.

In region where A+1.65A < 1

Sensitivity at 95% C.L. is at ms

value for which 1.65A=1

Bd

Bs

18

Bs Mixing Limit

ms > 14.8 ps-1 @ 95% CL

Uppgrade to an event by event fit

19

Log Likelihood Scan

ms < 21 ps-1 @ 90% CLMost probable value of ms = 19 ps-1

With the assumption A = 1

20

Top

p p

t

t

b

b

W

l

q

q

Branching Ratios

Production Cross Section

Top Mass

Top Charge

Top Lifetime

W

Rare/non SM Decays

W Helicity

Resonance Production

Top

21

TOP PAIR PRODUCTION

~85% ~15%q

t

t

q t

t

Standard model pair production via the strong interaction

Discovered in Run I

= 6.77 ± 0.42 pb for mtop = 175 GeV

22

TOP DECAY

20%

14.6%

14.6%1.2%2.4%

46%

1.2%

DILEPTON [ ee, mm, em,+ 2 b jets ] Small BR ~ 5%Smallest background

LEPTON + JETS[ e, m + 4 jets (2 b jets) ]Large BR ~ 30%Moderate background

ALL HADRON[ 6 jets (2 b jets) ] Large BR ~ 46% Larges background

23

DILEPTON CROSS SECTION

Signal Selection :

2 high PTLeptons

2 high PT Jets

Large missing ET

Veto invariant mass =

Z Background :Physics (from MC) :

Z /g *→ , Dibosons

Instrumental (from Data):

Faked Missing ET and

Faked Leptons

24

DILEPTONS

8.3 ± 1.5(stat) ± 1.0(syst) ± 0.5(lumi)  pb

8.6. +2.3-2.0 (stat) +1.2 -1.0

(syst)  pb

Results (Topological

cuts): ee, and ecombinedCDF 750 pb-1 preliminary

D0 350 pb-1 preliminary

Result (b-tag):

lepton + Track/b-tagging

7.1+2.6-2.2 (stat)±1.3 (syst) pb

D0 350 pb-1 preliminary

Combined with etopological)

8.6+1.9-1.7 (stat)±1.3 (syst) pb

Primary Vertex

Secondary Vertex Displace

d Tracks

Promt Tracks

Lxy

d0

25

Lepton+Jets Cross SectionBackgrounds Physics : W+Jets Instrumental: QCD Multijet

Signal Selection 1 high PT Leptons 4 high PT Jets (2 b-

jets) Missing ETTopological /Kinematics Analyses

6.7+1.4-1.3 (stat)+0.9

-0.8 (syst) pb

6.0± 0.6 (stat) ±0.9 (syst) pb

Likelihood Discriminant

Neural Network

26

Lepton+Jets Cross SectionSecondary Vertex Tag

8.2± 0.9 (stat)+0.9-0.8 (syst)

pb 8.2± 0.6 (stat) ±1.0 (syst) pb

27

Summary of Cross Section

28

t-channel

Single Top

q

q'

W t

b

u d

b t

W

tb

qq' s-channel

Top production via the Weak Current

SM : pb ± 8% = 1.98 pb ± 8%

A lot of background : W + jets, ttbar etc

29

Selecting Single Top

b

S channel: - W

- High PT lepton - Missing ET

-2 b – jets - At least 1 b-tagged jet

T channel: - W

- High PT lepton - Missing ET

-2 b – jets - At least 1 b-tagged jet

- 1 extra jet

t

W

b

l

pp

q

30

Single Top SearchLikelihood Discriminant Method Separate Single top from Backgrounds

Dzero limits with 370 pb-1 95% C.L.: s < 5.0 pb t < 4.4 pb

CDF limits with 695 pb-1 95% C.L.: s < 3.2. pb t < 3.1 pb

31

Top Mass Measurement

3232

Why Interesting?Top mass is fundamentel parameter

Top mass can constrain the Higgs mass

trough the loop diagrams:

W W

W W

b

t

H

Top mass can probe new physics

33

jet

jet

jet

jet

e/μ

b-tag jet

jet

jet

jet

b-tag jet

b-

tag

jet

jet

jet

Hard to Measure • Complicated events

– 12 ways to interpret 4 jets

• Reconstruction of jet energy scale is

distorted by:

additional interactions

electronic noise

pileup from previous buch-crossing

energy deposition outside jet cone

different response for different particles

20% of b-jets have muon and neutrino

• Background contamination

•

lepton

34

Top Mass MethodologyTEMPLATES

One mass per event from kinematic fit.

Create templates using event simulated with different Mtop values +

background.

Perform maximum likelihood fit to extract final mass.

MATRIX ELEMENTBuild likelihood directly from PDFs,matrix element(s), and transferfunctions that connect quarks and

jets.

Integrate over unmeasured quantities

Calibrate measured mass and error using simulation.

35

CDF Template Method

Four samples with different S/B and sensitivity to top:

0 b-tag 4 jets > 21 GeV 1 b-tag 3 jets > 15 GeV , 4th : 8 GeV < Et < 15 GeV 1 b-tag 4 jets > 15 GeV 2 b-tag 3 jets > 15 GeV , 4th > 8 >GeV

-Use assignments with lowest χ2 to reconstruct top mass.

- top masses equal

-reconstructed W near MW

Reconstructed W mass to calibrate JES

36

CDF Result

173.4+-2.5(stat+JES)+-1.3(syst).

37

D0 Matrix Element Method

x: reconstructed lepton and jets kinematics JES from MW constraint. Signal and background probabilities: from differential cross-sections All events are combined in a likelihood

-ln L(mtop;JES)=-lnΠ Pevt(xi;mtop;JES)

Maximal use of information in each event:

Calculating event-by-event probability to be signal or background,

based on the respective matrix elements:

Pevt(x;mtop; JES) = ftop*Psgn(x;mtop; JES) + (1-ftop) * Pbkg(x;JES)

Mtop = 170.6 ± 4.4 (stat.) ± 1.7 (syst.) GeV/c2

JES = 1.03 ± 0.03

38

Top Mass in Dilepton Events

Pros: Fewer combinationsCons: Unconstrained kinematics: 2 neutrinos in final

state Small branching fraction (5%)

CDF: 700 pb-1

164.5 ± 4.5 (stat.) ± 3.1 (syst.) GeV/c2

D0: 370 pb-1

177 ± 11 (stat.) ± 4 (syst.) GeV/c2

39

Top Mass Result

40

Are the other Properties of the Top Quark as Expected?

Top Charge

W-t-b

41

Top Charge

t

b

W

l

+2/3

-1/3

+1

+1

0

t

b

W

l

-4/3

-1/3

-1

-1

0

Standard Model

Exotic 4th Generation

Assiciate lepton + b-jet to a top quark

Kinematic fit for the ttbar hypothesis

Determine charge of the b-jet

PT weighted sum of tracks in the b-jet

Analys method

42

Top Charge II

D0 RunII (365pb-1)

- 17 candidate events with two tagged b-jets,

lepton, missing ET, 4 jets or more.

- two entries per event for top and anti-top.

- discriminate b and b with jet charge algorithm

- calibrate Monte Carlo with data using two jet

heavy flavor sample with opposite jet tagged

with charge.

- excluded the hypothesis of an exotic quark

with charge = -4/3 e at 95% confidence level.

43

With top quark samples we can measure it directly as “R”:

The relative rates of ttbar events with 0/1/2 b-tags is very sensitive to R

Top Decay Properties We said tWb, but really 100%?

Indirect measurement using the CKM matrix:

• implies |Vtb| is 0.998 @ 90% CL

R BR(t Wb)

BR(t Wq)

Vtb2

Vtd2 Vts

2 Vtb2

R = 1.03+0.19-0.17 (stat +

syst)

R > 0.64 @ 95% CL

Vtb > 0.80 @ 95% CL

R = 1.12+0.27-0.23 (stat +

syst)

R > 0.61 @ 95% CL

Vtb > 0.78 @ 95% CL

44

ConclusionLots of Exciting Results are pouring out from CDF and DO!

What I have shown is just theTop of the iceberg

And there are much more in the pipeline

Look forward to many more exciting results soon!