# Presentation: 758900

## Measurements of top quark   properties at CDF

**Aafke Kraan** **(University of Pennsylvania)**
**On behalf of the CDF collaboration**

**ICHEP      26 July - 2 August 2006, Moskou**

## Motivations

**Why is it so important to study top quark properties?**
**Top quark is a elementairy** **Standard Model** **particle!**
**Top mass is fundamental parameter (~172 GeV)**
**Is the top quark we observe really the Standard Model top?**
**Top properties could be modifies by** **new physics**....
**Top production: new resonances? **
**Top decay:**
**Still relatively little is known about the top quark !**
**The Tevatron at Fermilab is the only place where top properties    can be studied with high precision for the next 2-3(?) years! **

**Is it t********W****+**** b?**
**Is it a b? Or is it a q?**
**Is it a W****+****? Or a W-? Or is it a H****+****?**
**Is it a V-A weak decay?**

## Top quark properties

**b**

**l**

****** **

**W**

**Production:**
**Single production*****
**Pair production**
-     **-Cross sections***
**    ****-Mechanism**
**           ****-gg/qq***
**           ****-Spin correlation**
**         ****-Resonances?**

**Characteristics**
-    **Mass ****
**   ****Lifetime   **
**   ****Spin**
**   ****Charge**

**Top quark decay**
**B(t********Wb/t********Wq)**
**Non SM decays: **
**   ****t********H****+****b, ****t********τ νq,**
**   ****FCNC, ...**
**W-helicity**

**t**

-     ***: C. Hill, HQ**
**  ******: F. Canelli, EW**
*****: W.Wagner, EW**

**new 2006**

**new 2006**

**This talk:**
-  **New measurements!!**
-  **Summary of other        **
**    ****measurements.**

**    ****new  ICHEP!**

## Top pair production: resonances?

**Motivation:**  **Resonances predicted in models **
**	****	****      ****with dynamical EW symmetry **
**	****	****      ****breaking:[topcolor models **
**	****	****      ****Hill, Phys.Lett.B266, 418,1991]**
**Sample:** **lepton+jets >=4jets, 680 pb-1**
**	****	**** ****no b-tagging.**
**Method:**
**Observable: invariant mass M****tt**
**Use matrix element technique to **
**      ****assign for each event jets to partons **
**      **
**Result:** **No resonances seen...**
- 	**Cross section limits set...**
- 	**If X****0****=leptophobic Z’: Mx>725 GeV**
**      ****(Run1: 480 GeV) **

**t**

**t**

**X****0**

**q**

**q**

**new 2006**

**682 pb****-1**

## Top decay: W-helicity 

- Top decay: W-helicity

**Top quark decays via weak interaction **
**to spin-1 W****+**** boson and spin-1/2 b quark**
**Weak interaction is** **V-A****, so massless b-quark **
**must be left-handed.**
**W****+**** boson helicities (J•P)  ****	****  ****V-A(SM)    ****   ****	****            ****V+A**
**Motivation:**** ****is SM prediction**** modified** **beyond the standard model??**
**Left-right symmetric models? Mirror fermions?**
- 	        **Models:** 	 **Kane,Yuan et al.:         **
**	****	****	**** ****Beg, Mohapatra et al.: **
**	****	**** ****	**** ****Triantaphyllou:             **
**	****      ****	****	**** ****Tait,Yuan, He et al.:**

**f****0**** = 70%**
**f****--****  = 0% **
**f****+   ****= 30%**

**f****0**** = 70%**
**f****--****  = 30% **
**f****+  ****= 0%**

**J•P =   0:  longitudinal**
**J•P =  -1:  left-handed  **
**J•P = +1:  right-handed**

**Phys.Rev.D45:1241,1992,**
**Phys.Rev.Lett.38:1252, 1977.**
**J.Phys.G26:99,2000,**
**Phys.Rev.D62:011702,2000**
**Phys.Rev.D65:053002,2002 **

**V-A  t-W-b vertex****       **

**V+A  t-W-b vertex**

**θ***** is polar angle of charged lepton in W boson rest frame.                         The z-axis  is defined by the W boson direction in top quark rest frame.****    **

**Assume nothing new in W****+****→**** l****+****ν**** decay: neutrino is left-handed**

## W-helicity: analysis techniques

**W-helicity: analysis techniques**

**Sensitive ****observables ****to W helicity **
**are all from t****→Wb→l****ν****b**
**1. Lepton P****T**
-    **Sample:** **lepton+jets**
**           ****dileptons **
**2. M****lb ****2 ****:**** ****invariant mass squared of    **
**    ****lepton and b-quark**
-    **Sample:** **lepton+jets**
**	****  ****dileptons**
**3. Cos ***********: **reconstruct full ttbar event **
**    ****and boost to top and W rest frames**
-     **Sample:** **lepton+jets only**

**lepton and b **
**from same top**

-  **M****2****lb**** = 1/2 (M****2****t**** – M****2****W****)(1 + cos ****θ*********)**

**Note:**

**complexity**

##      W-helicity: Mlb2 method

**  ****Method: ****Use  inv. mass squared of lepton+b-jet**
**  ****Samples:**
**	**** ****	**** **

**    ****new  ICHEP!!**

**L+J 1b-tag after sim+reconstruction**

**Dilepton and 2 highest **
**E****T**** jets (no b-tagging):**

**Lepton+****≥3 ****jets with **
**2 b-tagged jets**

**Lepton+****≥3 ****jets with  **
**1 b-tagged jet**

**t**

**t**

**W**

**W**

**b**

**b**

****

**l**

**q**

**q**

**p**

**p**

**p**

**t**

**t**

**W**

**W**

**b**

**b**

****

**l**

**p**

****

**l**

**t**

**t**

**W**

**W**

**b**

**b**

****

**l**

**q**

**q**

**p**

**p**

**Result:**

**long. f****0****=0.7 fixed!**
**f****+****=-0.02  ± 0.08**
**f****+****< 0.09 at 95% CL**

**SVX**

**SVX**

**SVX**

**750 pb****-1**

**f****+****=0.3f ****V+A**** **

## W-helicity: cos*method

**W-helicity: cos*************method**

**Result :**
**f****0****=0.61 ± 0.14 with f****+****=0**
**f****+****=-0.06± 0. 07 with f****0****=0.7**
**f****+****< 0.11 @95% CL**

**Result:**
**f****0****=0.59± 0.14 with f****+****=0**
**f****+****=-0.03± 0.07 with f****0****=0.7**
**f****+****< 0.10 @95% CL**

**Sample:**** ****Lepton+****≥4 ****jets + b-tagging**
**Method: ****- Get cos ************* from 4-vectors of  lepton, W, top**
**	****   ****- Reconstruct fully top production+decay**
**   ****	****   ****-  Pick best hypothesis, based on:**

**improved kinematic fitter for b-tagging**

**  ****top mass kinematic fitter**

**    ****new  ICHEP!!**

**955 pb****-1**

**955 pb****-1**

**Remember:**
**SM: f****0****=0.7 **
**        ****f****+****=0**
**        **

## Top quark lifetime

**Motivation:** **top is heavy********decays promptly: lifetime ******** = h/********t**** ~10****-25 ****s ****	****         First direct limit!**
**Sample:** **lepton+jets >=3 j+btagging, 320 pb****-1**
**Method:**
**Determine resolution from**
**      ****lepton trigger data ****	**
**Measure impact parameter d0 for **
**     ****lepton tracks in top data sample.**
**Result: ****Upper limit****:**
**	****	****95% CL limit : **
**	****	****cτ****t**** < 52.5 μm ~ 1.8*10****-13**** s**

**t**

**l**

**b**

****

**W**

- d0>0?

**Production**

**Decay**

**318 pb****-1**

## Summary & plans

**Summary & plans**

**High luminosity samples ******** ****very**** nice measurements possible!**
**CDF+D0 are the only places for top data analyses for the next years!!**

**Publication status**
**                                 **
**PRL 95, 102002,2005****	****	****  ****	****           **
**PRL 95 022001, 2004****	****	****	****           **
**PRL 96, 042003,2005    ****	****	****  ****	****           **
**hep-ex/0510063, ****Apr 2006****	****            **
**CDF-conf 8104,  ****Feb 2006**
**CDF-conf XXX, ****July 2006****	****	****	****            **
**CDF-conf 8003,  ****Mar 2006****                                              **
**CDF-conf 8087,  ****Mar 2006**
**PRD 73 111103 ****	****	****     ****	****	**
**CDF-conf 8250, ****Apr 2006****                                               **
**CDF-conf 8280, ****May 2006**
**CDF-conf 8363, ****Jun 2006****	**
**Result coming soon! ****	****     ****	**
**Result coming soon! **
**Result coming soon!**
**Result coming soon!****	**
**	****	****	**

**Luminosity (pb****-1****)**
**162**
**194**
**194**
**350**
**320**
**330**
**760**
**680**
**    **
**162+run1 **
**320**
**750**
**955**
**1 fb****-1**
**1 fb****-1**** **
**1 fb****-1**
**	****	**

**Property**
**Br(t********Wb / t********Wq)**
**Anomalous kinematics **
**t->H****+****b**
**t->τ νq**
**Top lifetime**** **
**Production gg/qq            **
**Search for t’ **
**tt Resonances**
**W-helicity****    M****lb****+p****T****lepton ****	**
**    ****cos *************	****	**** **
**    ****M****lb**** ****	****	****  **
**    ****cos *************                           **
**Top charge                      **
**FCNC****	**
**Anomalous couplings Front/back asymmetry**
**	****	**

**Results/updates see** http://www-cdf.fnal.gov/physics/new/top/top.html**	**

## Mlb2 method: dileptons