# Presentation: 741685

## Heavy Quarks at the Tevatron

**CDF**

**DO**

**Bottom**

**Barbro Åsman**
**Stockholm University**

**For the CDF and D****0**** Collaborations**

**TOP **

**Proton**

**Proton **

**LISHEP 06**
**Rio de Janeiro**

## Golden Eggs

**Mixing:**
**B****s****, B****d**

**New particles:**
**X(3872), Xb,**
**Pentaquarks,**** ...**

**Mass measurements:**
**B****c****, ********b****, B****s****, ...**

**Production properties:**
******(b), ********(J/y), ...**

**B and D**
**Branching ratios**

**Rare decay searches:**
**B****s **** -> μ+μ-,**
**D****0 **** -> μ+μ- , ...**

**CP Violation**

**Lifetimes:**
******, ********b****, B****s****, B****c**** ..**

**SURPRISES!?**

##      HOW ?

- Measuring  b(udb) Lifetime

**L****xy**

**PV**

******b**

****

****

**p**

****

****

**p**

**p**

**B****0**

**K****0**

****

** ****WHY ?****           **** ****A ~2******** Differance between theory and **
**                                ****experiment for ********(********b****)/********(B****0****).****  ****Theory = 0.86**** ** **± 0.05**

- xy-plane

## b  Lifetime

- Extract 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****)/********(B****0****) = 0.944 ± 0.089**

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

******b****)/********(B****0****) = 0.87 ****+0.17****-0.14**** ± 0.03**

- New

## 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 B****c**** ******** J/********e******

## Results

******(B****c****) = 0.474 ****+ 0.073****– 0.066**** ± 0.033 (sys) ps**

******B****c****)****= 0.448 ****+0.123**** ****– 0.096****  ****±**** 0.121 (sys) ps**

- 

**B****c**

**L****xy**

**XY - plane**

- 

- 

- e

**c********L****xy****           **

**   ****M****B**

**  *********K**

**  ****P****T**** (vis)   **

**Where  K = P****T(vis)**** / P****T****(B)**
** ****is given from MC**

- New

## Review of B0 System

**In the B****0**** system: physical mass eigenstates = flavor eigenstates**********

**where:********= ******** H****- ********L**** (lifetime difference)**
****** ****= (********H****+ ********L****)/2**
**             ********m = m****H****- m****L**** (mass difference)**** **

**Time evolution of the two states is governed by the time-dependent Schrödinger equation and in the limit ******** ******** m**

**Prob (B****0**** -> B****0****)  = 1⁄2 e****-********t****(1+cos********mt)**

**Prob (B****0**** -> B****0****)  = 1⁄2 e****-********t****(1-cos********mt)**

**oscillation frequency****(**** ********m****d**** ,  ********m****s****)**

**Ignoring CP violation**

## Extract  from Bs  K+K- lifetime

**• ****Measurement of B****s ****-> K****+****K****-**** lifetime (=********L****) in 360**** ****pb****-1**
**• ****Mass fit ****and**** ****l****ifetime fit:**

**•****Extraction of ******** (CP)/********(CP)****:**
**•****This measurement gives c********L ****= 458 ± 24 ± 6 μm**
**•****HFAG average gives weighted average: (********L****2**** +********H****2****) /(********L**** + ********H****)**
**•****Extract ********H**
**•****Thus derive******** =-0.080 ± 0.23 (stat) ±0.03 (syst)**

- New

## BS lifetime and 

**B****s****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**

- New

## Summary of 

## Bd and Bs Mixing

****

****

****

******m****d**** = (lots of QCD) x  V****td**
******m****s**** = (lots of QCD) x  V****ts**

******m****s****/********m****d**** = (much less QCD ) x  V****ts**** / V****td**** **

**V****ud ****     V****us****     V****ub**
**V****cd ****     V****cs****      V****cb**
**V****td****      V****ts****      V****tb**

**V    =**

**V****ud ****V****ub***** + V****cd****V****cb***** + V****td****V****tb***** = 0**

**-**

**1**

**= **

**V****td**

**  ****V****ts**

****

## Analysis Strategy

- Bs oscillations is more difficult than Bd  oscillations because of the fast mixing frequency

**In order to measure ******** m:**

** ****Reconstruct the B****s**** signal**
** ****Know the flavor of the meson at its **
**    ****production time (Flavor tagging) and**
**    ****get********D****2 **** (tagging power)**
**  ****Calculate Proper length resolution**

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

## Reconstruction

-                **Currently only using semileptonic decay of the B****s**** **
**                                 ****B****s   ****-> D****s ********X (D****s ****-> **************************

**μ****D****±****: 7,422±281**

**μ****D****±****: 7,422±281**

**μ****D****s****: 26,710±560**

**μ****D****±****: 1,519±96**

**μ****D****s****: 5,601±102**

## 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**

- b-hadron

- Jet Charge

**P.V**.

- Tagging Side

- Vertexing Side

**Secondary  Vertex  Charge  **

## Cross Check of Tagging   

**On a B****d**** sample**

******D****2**** = (2.48  0** **±****.21 ****+0.08**** ****-0.06 ****) %**

**Tagger tuned using B****d**** mixing measurement**** **

******m****d**** = 0.506  ± 0.020 ****± ****0.014**** **ps**-1**

**B****0**

**B****+**

## Bs Lifetime 

**c********L****xy****           **

**   ****M****B**

***K**

**  ****P****T**** (lD)   **

**Where  K = P****T****(lD) / P****T****(B)**
** ****is given from MC**

## Amplitude Fit Method 

**Prob**** (B****0**** -> B****0****)  = 1⁄2 e****-********t****(1+*****A*****cos********mt)**

**Fit  to data – A free parameter**

**Prob (B****0**** -> B****0****)  = 1⁄2 e****-********t****(1-*****A*****cos********mt)**

**Fit for oscillations amplitude *****A ***
**for a given ********m **

**Expect *****A***** = 1 for frequency = true ********m****s**
**Expect***** A***** = 0 for frequency = true ********m****s**

**If no signal observed :**
**Exclude ********m****s**** value at 95% C.L.**
**In region where *****A*****+1.65********A**** < 1**
**Sensitivity at 95% C.L. is at ********m****s ****value for which 1.65********A****=1**

**B****d**

**B****s**

## Bs Mixing Limit

*********m******s****** >  *****14.8 ps****-1**** @ 95% CL**

**Uppgrade to an event by event fit**

## Log Likelihood Scan

*********m******s****** <  *****21 ps****-1**** @ 90% CL**
**Most probable value of ***********m******s***** = 19 ps****-1**

**With the assumption A = 1**

## Top

**p**

**p**

**t**

**t**

**b**

**b**

**W**

**l**

**q**

**q**

****

- Production Cross Section

- Top Mass
- Top Charge
- Top Lifetime

**W**

- Rare/non SM Decays

- W Helicity

- Resonance Production

**Top**

**Notes:**
Decays before it hadronize.

## 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

## TOP DECAY

**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**

**Notes:**
Här måste t -> b W  

## 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

## 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 e********combined**

- CDF 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 e********topological)**

**** 8.6+1.9-1.7 (stat)±1.3  (syst) pb

- Primary Vertex

- Secondary Vertex

- Displaced Tracks

- Promt Tracks

- Lxy

- d0

## Lepton+Jets Cross Section

- Backgrounds
-  Physics : W+Jets
-  Instrumental:  QCD Multijet

- Signal Selection
-  1  high PT Leptons
-  4 high PT  Jets (2 b-jets)
-  Missing ET

- Topological /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

## Lepton+Jets Cross Section

- Secondary Vertex Tag

****** ****8.2± 0.9 (stat)****+0.9****-0.8**** (syst)  pb     **

****** ****8.2± 0.6 (stat) ****±1.0**** (syst)  pb     **

## Summary of Cross Section

## Single Top 

- Single Top

**  ****s-channel **

- Top production via the Weak Current

**SM**  :          ****** pb **± 8%                                     ********** = 1.98 pb **± 8%

- A lot of background : W + jets, ttbar etc

## 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**

****

**p**

**p**

**q**

## Single Top Search

**Likelihood 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**

-    Top Mass Measurement

## Why Interesting?

**Top mass is fundamentel parameter**
**Top mass can constrain the Higgs mass**
**trough the loop diagrams:  **

**Top mass can probe new physics**

## Hard to Measure

**e****/****μ**

-          **• ****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

## Top Mass Methodology

**TEMPLATES**** **
**One mass per event from kinematic fit.   **
**Create templates using event simulated **
**with different M****top****  values + background.**
**Perform maximum likelihood fit to **
**extract final mass.**

**MATRIX ELEMENT**
**Build likelihood directly from PDFs,**
**matrix element(s), and transfer**
**functions that connect quarks and jets.**
**Integrate over unmeasured quantities**
**Calibrate measured mass and error **
**using simulation****.**

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

**-****Use assignments with lowest χ****2**** **
**  ****to**** ****reconstruct top mass****.**
**- top masses equal**
**reconstructed W**** ****near M****W**
**Reconstructed W mass to calibrate JES **

## CDF Result

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

## 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(m****top****;JES)=-lnΠ P****evt****(x****i****;m****top****;JES)**

- Maximal use of information in each event:
-            Calculating event-by-event  probability to be signal or background,
-            based on the respective matrix elements:
***P******evt******(x;m******top******; JES) = f******top*******P******sgn******(x;m******top******; JES) + (1-f******top******) * P******bkg******(x;JES)***

**M****top**** = 170.6 ± 4.4 (stat.) ± 1.7 (syst.) GeV/c****2**
**                                             ****JES = 1.03 ****±  ****0.03**

## Top Mass in Dilepton Events

_**Pros:**_
-                 **Fewer combinations**
_**Cons:**_
**               ****Unconstrained kinematics: 2 neutrinos in final state**
**               ****Small branching fraction (5%)**

**CDF: 700 pb****-1**

**164.5 ± 4.5 (stat.) ± 3.1 (syst.) GeV/c****2**

**D0: 370 pb****-1**

**177 ± 11 (stat.) ± 4 (syst.) GeV/c****2**

**Notes:**
Expected background fraction is 21%.  To get mapping, backgrounds are fluctuated (separately or together) w/ poisson b/w 0 and 50%.

## Top Mass Result

## Are the other Properties of the Top Quark as Expected? Top Charge W-t-b

## Top Charge

- 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**

## 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.**

## _x0005_Top Decay Properties

_**measure it directly**__ as “R”:_
**The relative rates of ttbar events **
**with 0/1/2 b-tags is very sensitive to R**

- _x0005_Top Decay Properties

**  **_**We said t**__****__**Wb, but really 100%?**_

** ****Indirect measurement using  the CKM matrix**:
-   implies |Vtb| is  0.998 @ 90% CL

**R = 1.03****+0.19****-0.17 ****(stat + syst)**
**R > 0.64 @ 94% CL**
**V****tb ****> 0.80 @ 94% CL**

**R = 1.12****+0.27****-0.23 ****(stat + syst)**
**R > 0.61 @ 95% CL**
**V****tb ****> 0.78 @ 95% CL**

## Conclusion

**Lots of Exciting Results are pouring out from CDF and DO!**
** **

**What I have shown is just the**
**Top of the iceberg**

**And there are much more in the pipeline**

**Look forward to many more exciting results soon! **