# Presentation: 295189

## Top mass and properties

*Yen-Chu Chen*
*Institute of Physics, Academia Sinica, *
*Taiwan, R.O.C. *
*For the CDF and D0 collaboration*

- Moriond EWK, La Thuile, Italy

- Mar. 1-8, 2008

## The mass is well measured.
Assuming that this is really the Top/Truth! 
Is it really Top/Truth of the Standard Model (SM)?
Studying the properties

*The mass is well measured.*
*Assuming that this is really the Top/Truth! *
*Is it really Top/Truth of the Standard Model (SM)?*
*Studying the properties*

- Moriond EWK, La Thuile, Italy

- Mar. 1-8, 2008

## Top quark physics

**P**

**P**

- 

***t***

***t***

- 

**X**

***b***

***b***

****

**W ******

**W ******

***l *******
***q ***

***l *********
***q ***

******
***q******'***

**_**

******
***q******'***

**_**

**_**

*Production Cross section*

*Top spin*

*Rare decays, charged Higgs, etc.*

*W helicity*

*Top charge*

*Top mass*

*Charge asymmetry*

*Life time, decay width*

*Production mechanism*

*FCNC*

*Br(t****→****Wb)/Br(t****→****Wq)*

- Moriond EWK, La Thuile, Italy

- Mar. 1-8, 2008

## Top mass measurement

*both W decay to leptons,*
*in practice uses **only e,****μ****.*
*Lepton+Jets (**LJ**)** channel: *
*one W decays to leptons,*
*the other decays to quarks.*
*Hadronic** channel:*
*both W decay to quarks.*

***t***

***t***

***W ******+***

***W******̅***

***b***

***b***

***e******+******, ******μ******+******, u, c***

***e ******–******, ******μ******–******, u, c***

- _

- _

- _

*********e******, ************μ****** ******, d, s ***

- _

- _

*********e******, ************μ****** ******, d, s ***

- _

- _

- _

- Moriond EWK, La Thuile, Italy

- Mar. 1-8, 2008

## Fit to reconstructed Top mass templates
In-situ jet energy calibration
Based on W->jj
Constraint on W boson mass
Using Matrix Element (ME):
Use leading order matrix element  
Integrating over the phase space
Find the probability density as a function of Top mass
Single sensitive variable, Lxy
Matrix weighting
Neutrino weighting
Other methos not described here :
Kinematic method, constraint to Xsection,..

- In-situ jet energy calibration
*Based on **W->jj*
*Constraint on W boson mass*
- Using Matrix Element (ME):
*Use **leading order** matrix element  *
*Integrating over the phase space*
*Find the **probability density** as a function of Top mass*
*Single sensitive variable**, Lxy*
*Matrix weighting*
*Neutrino weighting*
*Other methos not described here :*
*Kinematic method, constraint to Xsection,..*

**(CDF)**

- Top mass measurementthe techniques

- Moriond EWK, La Thuile, Italy

- Mar. 1-8, 2008

## Mt = 170.9 ± 1.8 GeV/c^2, 

**M****t**** = 170.9 ****± ****1.8 GeV/c^2, **
**from 1 fb****-1**** CDF+D0 combination**

- Moriond EWK, La Thuile, Italy

- Mar. 1-8, 2008

## Top mass measurement, CDF

- Use Neural Networks to select *DIL* Top candidates then perform ME, *2 fb**-1**.*
*This neural networks is **evolutional.*
*optimized on **improving uncertainty.*

- Moriond EWK, La Thuile, Italy

- Mar. 1-8, 2008

## Top mass measurement, CDF

- Top mass measurement, *CDF*

**m****t ****= 177.0 ± 3.7 (stat+JES) ± 1.6 (sys) GeV/c****2**

- Top mass template, all hadronic, *1.9 fb**-1*
*Use **Neural Networks** for event selection.*
*Require **b tagging.*
*Do** In-situ jet energy** **calibration.*

- Moriond EWK, La Thuile, Italy

- Mar. 1-8, 2008

## Top mass measurement, CDF

**m****t ****= 172.7 ± 1.2 (stat) ± 1.3 (JES) ± 1.2 (sys) GeV/c****2**

*Matrix Element**, **LJ*, *1.9 fb**-1*
*Use **Neural Networks** for event selection*
*Require **b tagging*
*Do** in-situ jet energy calibration*

- Moriond EWK, La Thuile, Italy

- Mar. 1-8, 2008

## Top mass measurement, CDF

*Lxy, **LJ,** **0.7 fb**-1*
*Lxy : **Transverse decay length*
* **Fit data to MC (sig+bkg) to find out Lxy.*

**m****t ****= 180.7 ****+15.5**** ****-13.4**** (stat) ± 8.6 (sys) GeV/c****2**

- Moriond EWK, La Thuile, Italy

- Mar. 1-8, 2008

## Top mass measurement, CDF

- Moriond EWK, La Thuile, Italy

- Mar. 1-8, 2008

## Top mass measurement, D0

- Matrix weighting, *DIL, 1 fb**-1*
*For a **given m**t** try to resolve for Top, anti-Top momenta.*
*Define **weight** for each solution.*
*Account for detector resolution.*
*Take into account the background.*
*Scan through m**t** to reach the **max. weight** and the **min. of likelihood**.*

**m****t ****= 175.2 ± 6.1 (stat) ± 3.4 (sys) GeV/c****2**

- Moriond EWK, La Thuile, Italy

- Mar. 1-8, 2008

## Top mass measurement, D0

- Neutrino weighting, *DIL, 1 fb**-1*
*Ignore E**t **measured.*
*given **m**t** **and **** for each ****; resolve for **** momenta.*
*For each event define **weight** based on E**t **calc. and measured.*
*Take into account detector resolution and background.*
*Define likelihood.*

**m****t ****= 172.5 ± 5.8 (stat) ± 3.5 (sys) GeV/c****2**

****

****

- Moriond EWK, La Thuile, Italy

- Mar. 1-8, 2008

## Top mass measurement, D0

- Matrix Element, *LJ,** **1 fb**-1* :
*Use **in-situ jet energy** calibration.*
*Result** without b tagging**:*
*Result** with b tagging**:*

*e*

**μ**

**m****t ****= 170.5 ± 2.4 (stat+JES) ± 1.2 (sys) GeV/c****2**

**m****t ****= 170.5 ± 2.5 (stat+JES) ± 1.4 (sys) GeV/c****2**

- Moriond EWK, La Thuile, Italy

- Mar. 1-8, 2008

## Top mass measurement, D0

- Moriond EWK, La Thuile, Italy

- Mar. 1-8, 2008

## Top mass measurement, the future

***Tevatron Top mass, 2007 Mar.***

- Reaching below 1% uncertainty!
*CDF* and *D0 **are **working together** on the common systematic issues to reduce uncertainty.*

- Moriond EWK, La Thuile, Italy

- Mar. 1-8, 2008

## The charge of Top quark

*SM*: *+2/3q**     XM: **-4/3q*
*Each event has lepton(s) and jets:*
*Pairing : **Top mass as input, M**lb**2*
*Jet charge** determination*
* **Odds of SM vs. XM:*
-  ***2 ************ Ln(B.F.)***
*0 – 2 : Not worth than a bare mention*
*2 – 6 : Positive*
*6 – 10: Strong*
*> 10 : Very strong*

**_**

**_**

***SM*** :   t → W+ b
***XM***:   t’ → W- b

- Moriond EWK, La Thuile, Italy

- Mar. 1-8, 2008

## The charge of Top quarkCDF

***CDF***** result (1.5 *****fb*****-1****): **
***2Ln(Bayse factor) = ******12.0***
***f+ = SM like / Total***
***         ******> 0.4 @ 95% CL***

**W charge ******** jet charge**

***probability***

***N******Q***

- CDF Run II preliminary L=1.5 fb-1

- The charge of Top quark*CDF*

- Moriond EWK, La Thuile, Italy

- Mar. 1-8, 2008

## W helicity in Top decay

- Theory:
*f**0** = 0.7, **longitudinal*
*f**–** = 0.3, **left handed*
*f**+** = 0, **right handed*

- Moriond EWK, La Thuile, Italy

- Mar. 1-8, 2008

## W helicity in Top decayCDF

***f******0****** = 0.65 ************ 0.19 (stat) ************ 0.03 (sys)***
***f******+****** = -0.03 ************ 0.07 (stat) ************ 0.03 (sys)***

***Fix f******0 ******to SM:***
***f******+****** = -0.04 ************ 0.04 (stat) ************ 0.03 (sys)***
***f******+****** < 0.07 @ 95% C.L.***

- Moriond EWK, La Thuile, Italy

- Mar. 1-8, 2008

## W helicity in Top decayD0

***f******+****** = -0.002 ************ 0.047 (stat) ************ 0.047 (sys)***
***f******+****** < 0.13 @ 95% C.L.***

- W helicity in Top decay*D0*

***f******0****** = 0.425 ************ 0.166 (stat) ************ 0.102 (sys)***
***f******+****** = 0.119 ************ 0.090 (stat) ************ 0.053 (sys)***

***LJ, Lep.***

***LJ, Had.***

***DIL***

- Moriond EWK, La Thuile, Italy

- Mar. 1-8, 2008

## R = Br(t→Wb)/ Br(t→Wq)D0

- Simultaneous fit to the production cross section and R.
*LJ , 0.9 fb**-1*
- R = *0.97 **+0.09** **-0.08** (stat + sys)*
*      **> 0.79** @ 95% CL*
*|V**tb**| **> 0.89** @ 95% CL*
***tt** = 8.18 **+0.90** **– 0.84** (stat+sys) *
*            **± **0.50 (lumi) pb*

- Moriond EWK, La Thuile, Italy

- Mar. 1-8, 2008

## Search for FCNC in Top decayCDF

*SM : B(t → Zq) = **O(10**–14**)*
*Beyond SM : up to O(10**–4**)*
*At **LEP** : **13.7%*
*Look for 2 lep. 4 jets.*
*Constraint on **masses of Top, Z and W**.*
*Best limit up to date: **3.7%*

- Moriond EWK, La Thuile, Italy

- Mar. 1-8, 2008

## Conclusion

- More than ten years after the Top quark discovery:
- Top quark mass is well measured to 1.1% level!
- Up to date, within uncertainties, all measured quantities are consistent with the Standard Model expectations.
- Top charge, W helicity *, **R**b*, *FCNC*
*Analysis in progress or not reported here,*
*Life time, decay width, top spin correlation, charged Higgs search, etc.*
- This is just the beginning of the sensitive studies of the Top quark properties! There are much room ahead for surprises!

- Moriond EWK, La Thuile, Italy

- Mar. 1-8, 2008