# Presentation: 273307

## Alberto Sánchez Hernández
CINVESTAV (Mexico City)
DØ Collaboration

- CINVESTAV (Mexico City)
- DØ Collaboration

**Heavy Flavor Physics at DØ**

## DØ Detector

**DØ Detector**

## Tracker

**Trigger: muon+track covers |********|<2.2**

**SMT+ CFT**
******max**** = 1.65**

***8******×2 CFT layers***

**SMT region**
******max**** = 2.5**

***4****** SMT layers***

**Tracker**

****** ****= - ln (tan(********/2))**

## Tracking Performance

- Impact Parameter Resolution

- (DCA)53m @ Pt=1GeV
- and 15 m @ higher Pt

- Can provide
-    K/ separation for Ptot<400 MeV
-    p/ separation for Ptot<700 MeV
- NOT yet used for PID

- SMT dE/dx

**Tracking Performance**

**MC ******** Data**

## Tracking Performance

- || for kaons from D*D0

- pT spectrum of soft pion from D*D0

**Efficient muon and tracking system give us a**
**large sample of semileptonic B decays**

**Tracks are reconstructed**
** ****over a wide ******** range  **
** ****starting from p****T ****= 180 MeV**

**Data from semileptonic decays (B **  D X)

**Tracking Performance**

## A New Particle: X(3872)

-  possible charmonium state or an exotic 	meson molecule (?)
-  BELLE didn’t  find evidence for c1** **

-  X(3872)  J/  production in 	ppbar collisions has been confirmed  	by CDF

**A New Particle: X(3872)**

**BELLE: PRL91,262001,(2003)**

**CDF II: hep-ex/0312021**

## What can we say about the X(3872)?

** ****SMT hit > 1**
** ****num tracks < 100**
** ****pT(****J/********) > 4 GeV/c**
** ****2.8 < M(********+********-****) < 3.4 GeV/c****2**
** ****pT(********) > 0.4 GeV/c**
** ********’****s within same cone as J/******
** ****M(********+******** -****) > 0.52 GeV/c****2**
** ****M(********+********- ********+******** -****) -M(********+********-****) < 1.0 GeV/c****2**
** ********2 ****(********+********- ********+******** - ****- vertex) < 16**
** ****|z****vertex****| < 35 cm**

- 4.4effect

- M = 0.7684  0.0035 (stat)  0.0039 (sys) GeV/ c2

- 300  61  X(3872) candidates

**What can we say about the X(3872)?**

## Properties of X(3872)

** ****Look if  production  ****	****characteristics are similar to ****	********(2S).**
**  ****Data was  binned for ****	****different variables: decay-****	****length,  isolation, ******** (pseudo-****	****rapidity) pT, ********and ****	****helicity of  ****	****(********+******** -****)**

**Properties of X(3872)**

## X(3872) - (2S) comparison

- Within the current statistical uncertainties, the production of X(3872) has similar behavior as the cc(bar) state (2S)

**X(3872) - ********(2S) comparison**

**Yield given cut / Total Yield**

## What is X(3872)?

-  While observing radiative decays Xc1  would favor cc(bar) 	hypothesis** **
-  Both of these would require DØ to identify low  energy  and  	(work in progress)
-  Our tests show: production characteristics of X(3872) (in the 	used variables) seems similar to those from (2S) (within the 	statistical uncertainties),  this would tend to favor a cc(bar) 	hypothesis,  but we do not know (yet) how these characteristics 	look for an exotic meson-molecule (theoretical input needed).

**What is X(3872)?**

## B Semileptonic Samples

**Muon:**
**Pt > 2 GeV/c**
**nSMT > 1**
**nCFT > 1**

**Charged tracks:**
**pT > 0.7-1 GeV/c**
**Secondary Vertex**
**L****xy**** / ********L**** > 4**
**cos(********(L,P****D****))>0.95**

**B Semileptonic Samples**

**For Mixing and Lifetime studies**

## Bd,s Masses (J/ + K0*,,K0s)

**B****d,s**** Masses (J/******** + K****0*****,********,K****0****s****)**

**For CP and Lifetime studies**

## (Bd)/(Bs) =1±0.01
(0b)(b) < (Bd) < (-b) < (b)
(b)-(-b)  0.11±0.03  ps-1
0.9 < (b)/(Bd) <1

- Experimental Results

- (B)  = 1.573±0.008  ps
- (B0) = 1.534±0.013  ps
- (B+) = 1.652±0.014  ps
- (B+)/(B0) = 1.081±0.015

*B Lifetime Group (Summer 2003)*

- (BS)  = 1.439±0.053  ps
- (bbaryon)  = 1.210±0.051  ps
- (b) = 1.233+0.078   ps

- -0.076

- (Bd)/(Bs) =1±0.01
- (0b)(b) < (Bd) < (-b) < (b)
- (b)-(-b)  0.11±0.03  ps-1
- 0.9 < (b)/(Bd) <1

- Predictions

*Report of the B Physics *
*at the Tevatron Workshop (12/2001)*

**B Lifetime Measurements**

## Use J/+-  for tagging, vertex constraint, pT determination:

**J/******** Signal = 290.3k events**
**Mass = 3.0718±0.0002 GeV/c****2 **
****** ****= 0.0741±0.0002 GeV/c****2**

******’ ****Signal = 8.22K events**
**Mass = 3.668 ± 0.002 GeV/c****2 **
****** ****= 0.071 ± 0.002 GeV/c****2**

**114pb****-1**

- Use J/+-  for tagging, vertex constraint, pT determination:
- Clean signal
- Large statistics
- Good vertex resolution
- Good momenta resolution

- Large prompt J/ contamination
- Need Pt correction factor from MC

**Measuring Lifetime using B******** ****J/******** X,  ****J/******** ************+********-**

## B Lifetime from Inclusive BJ/+X

**F: correction factor to use the **
**pT(J/ ********) to estimate the ****momentum of the B to find proper time. Obtained from Monte Carlo**

- J/ from B’s = 18%

- Correction factor leads to the major systematic error

- b J/ X

****1.564  0.014  ps (PDG)

****1.562  0.013  0.045  ps** **

******£****dt********114 pb****-1**

**B Lifetime from Inclusive B********J/********+X**

## B± Lifetime from B±J/K±

- <B±>=1.65±0.083(stat)±0.123(syst)  ps

******£****dt********114 pb****-1**

- <B±>=** **1.671±0.018  ps (PDG)

- Fully reconstructedNo Correction Factor!

**B****±**** Lifetime from B****±********J/********K****±**

## Bd,s Lifetimes from B J/+K0*,

**Signal: 105±19**

**Signal: 69±13**

- Bd=1.51+0.19 (stat) ± 0.20(syst) ps

- -0.17

- Bs=1.19+0.19 (stat) ± 0.14(syst) ps

- -0.16

- Bs/ Bd=0.79 ± 0.14

- PDG: Bd = 1.537 ± 0.015 ps

- PDG: Bs = 1.461 ± 0.057 ps

- PDG: Bs/ Bd = 0.95 ± 0.038

**Similar kinematics****Some systematic errors  can be cancelled in ratio!**

******£****dt********114 pb****-1**

**B****d,s**** Lifetimes from B**** ********J/********+K****0*****,******

## K = Pt(D+) / PtB   (from MC) 

******Ldt********12 pb****-1**

** **B*  *=1.460 ± 0.083 (stat) ps

- c** **=** **LxyMbK/Pt(D+****)

- K = Pt(D+) / PtB   (from MC)

- We are able to measure Lifetime

**B Lifetime from Semileptonic Decays B**** ******** D****0********X**

- We will use this for mixing studies

## Mixing: Flavour tagging

- 		- Soft-lepton tags - High dilution power, low 			  efficiency (SL decay of other B)
- 		- Jet Charge tag - Poorer dilution power, high 		  	  efficiency (track-jet from other b quark)
- 		- Same Side tagging - Poorer dilution power, 			  high efficiency (fragmentation, B**)
-  We test this tools using B+  data sample

**Mixing: Flavour tagging**

##  

- Q – charge of muon with
-      the highest PT
- Classification:
- Q !=  QK : correct tag
- Q == QK : wrong tag
- No muon : No tag

- D = (57.0 ± 19.3)%
-   = ( 5.0  ±  0.7)%
- D2 = (1.6 ± 1.1)%

- B±J/K±

-  

**DØ RunII preliminary**

**Opposite Side Muon Tagging**

## PT > 0.5 GeV

- ZPV < 2 cm
- Classifications:
- |Q|>0.2 && sign(Q) !=  QK : correct tag
- |Q|>0.2 && sign(Q) == QK : wrong tag
- |Q|<0.2 : no tag

- B±J/K±

**Opposite Side Jet Charge Tagging**

## Excited B** decays into B and pion/kaon that carries the initial state flavor information

- Example: B**d B+-

- +** ********±**

**Same Side Tagging**

## Flavour Tagging results

| Method
Based on 
B+ Signal | Efficiency

 | Dilution | Tagging  Power
                  |
| --- | --- | --- | --- |
| Soft Muon | 5% | 57% |                     |
| Jet Charge | 47% | 27% |  |
| Same Side | 79% | 26% |  |

- Muon DATA, will also
-  use electrons

**DØ RunII Preliminary**

- Performance with B0/Bs is under study

**Flavour Tagging results**

## Search for Bs  +-

**Br(B****s**** ******** ********+********- ****) < 1.6 ******** 10****-6   ****at  90% CL**

******Ldt********100 pb****-1**

**MC**

## 
DØ has observed the X(3872) particle in 200 pb-1 data
Statistical significance of 4.4
M = 0.7684  0.0035 (stat)  0.0039 (sys)
Data separated into various regions, we found similar behaviour as (2S), within statistical uncertainties
Many other results as B physics program under way
We have reprocessed  200 pb-1 of data to better improve our analyses 
A lot more interesting results very soon!

- DØ has observed the X(3872) particle in 200 pb-1 data
- Statistical significance of 4.4
- M = 0.7684  0.0035 (stat)  0.0039 (sys)
- Data separated into various regions, we found similar behaviour as (2S), within statistical uncertainties
- Many other results as B physics program under way
- We have reprocessed  200 pb-1 of data to better improve our analyses
- A lot more interesting results very soon!

**Summary**

##  More Data

** ********Ldt ********114 pb****-1**

** ****Reprocessed  ********Ldt********200 pb****-1**