# Presentation: 103204

## Lifetimes 
        Bs->J/       B->J/ 0 
        Bd->J/ K*      B0->J/ Ks
at D∅

 P.L.M  Podesta-Lerma  

CINVESTAV-MEXICO 

-         Bs->J/       B->J/ 0
-         Bd->J/ K*      B0->J/ Ks
- at D∅
-  P.L.M  Podesta-Lerma
- CINVESTAV-MEXICO

## Motivations
Topology
Data
Cuts
Fitting technique
Systematics
Crosschecks  

- Topology
- Data
- Cuts
- Fitting technique
- Systematics
- Crosschecks

- Outline

## Motivations:b-baryon discrepancy:

- Motivations:b-baryon discrepancy:

## Motivations: Current measurements:

- Motivations: Current measurements:

## 4 track  Vertex Topology 

- PV ~ 20 m

- SV ~ 40 m

- +

- -

- K-(-)

- K+

- Bs(Bd)

- J/

- (K*)

- Lxy = XB- Xprim

- LBxy = Lxy ° pTB
-                      | pTB  |

-  cB =B =LBxy (MB/pTB)

## 3 track  Vertex Topology 

- 3 track  Vertex Topology

- PV ~ 20 m

- SV ~ 40 m

- +

- -

- -(-)

- p(+)

- B(Bd)

- J/

- 0(Ks)

- 7.9 (2.9) cm

## J/ cuts
 J/ mass [2.9,3.25] GeV
 Smt hits in muon >1 
 Distance from PV to J/psi vertex <10 cm 
 Al least one PV reconstructed
 Track measurements downstream (<1) to the vertex and misses upstream (<5)

-   J/  +-

**J/******** cuts**
-  J/ mass [2.9,3.25] GeV
-  Smt hits in muon >1
-  Distance from PV to J/psi vertex <10 cm
-  Al least one PV reconstructed
-  Track measurements downstream (<1) to the vertex and misses upstream (<5)

##  cuts
 Mass windows [1.008,1.032] GeV, 
 2 opposite charge tracks that make a vertex of 4 tracks with the Jpsi vertex  
 SMT hits > 0 for each track

-     K+K-

**** **cuts**
-  Mass windows [1.008,1.032] GeV,
-  2 opposite charge tracks that make a vertex of 4 tracks with the Jpsi vertex
-  SMT hits > 0 for each track

## 
K* cuts
 Mass windows (0.85,0.93) GeV 
 2 opposite charge tracks that make a vertex of 4 tracks with the Jpsi vertex  
 SMT hits > 0 for each track

- K* **cuts**
-  Mass windows (0.85,0.93) GeV
-  2 opposite charge tracks that make a vertex of 4 tracks with the Jpsi vertex
-  SMT hits > 0 for each track

-   K* K+-

## 
 cuts
 Mass windows (0.85,0.93) GeV 
 2 opposite charge tracks that make a vertex of 4 tracks with the Jpsi vertex  
 SMT hits > 0 for each track

-  **cuts**
-  Mass windows (0.85,0.93) GeV
-  2 opposite charge tracks that make a vertex of 4 tracks with the Jpsi vertex
-  SMT hits > 0 for each track

-    K+-

## 
Ks cuts
 Mass windows (0.85,0.93) GeV 
 2 opposite charge tracks that make a vertex of 4 tracks with the Jpsi vertex  
 SMT hits > 0 for each track

- Ks **cuts**
-  Mass windows (0.85,0.93) GeV
-  2 opposite charge tracks that make a vertex of 4 tracks with the Jpsi vertex
-  SMT hits > 0 for each track

-  Ks-+

## PDF models:

- SM : Gaussian
- BM : First(Second)-order polynomial background
- Resolution Model
- Gaussian using event-per-event lifetime error & “s” scale factor

## PDF models:

- Lifetime models
- SLF : Signal lifetime PDF
- Convolution(Exponential decay, Resolution)
- BLF : Background lifetime PDF
- Resolution + negative exp. decay + 2 positive exp. decays
- 2Dim PDF:

## Lifetime distribution models

- ⊗

- =

- +

- +2

## Slide 15

## Slide 16

## B->J/ 0 

- N = 61 ± 12 Events

- B->J/ 0

## B0->J/ Ks 

- N = 291 ± 23 Events

- B0->J/ Ks

## Systematics

**J/psi Vertex**

-  Run with a different geometry.

**  **

**Alignment **

**Fitting  **

-  Use J/ vertex instead of B vertex.

-  Use toy MC to test or Fit code.

- Use a  quadratic  polynomial in Mass
- Convolute exponentials
- Use two decays for long lifetime.
- Cross feed  contamination Bs⇔Bd

**Background **

**Resolution **

-  Use different Model for resolution

##      J/ Vertex

- For ideal B candidates, B and J/ vertex should be equal. J/vertex may be inaccurate when two tracks are very close (collinear).  We got a sytematic errors of 3 m for Bs and 4 m for  Bd.

- Preliminary

##      Background

- We have that the c distributions  from the “sideband”.  Hi and Low are not equal.  Sytematic Error of 3 m for Bs, Bd.

- Fitted PDL  Low(left) and High(right) mass regions for the Bd

## Fitting Code 

- We generated a 1000 samples with the Bs PDF, and parameters. We fit using same code. This told us how well our fitting method is.

- Difference = 0.3 ± 0.9 m

- Difference = 0.2 ± 0.5 m

-   Bs

-   Bd

## B0(J/Ks)

- B0(J/Ks)

- Λb(J/)

- Cross-feed contamination (estimated from MC)

## Systematics summary 

## MC studies

**Vertex studies (Pulls and resolutions)  **

-  Make the resolution studies
-  Cross feed Bs Bd
-  Estimate linearity of our Fit.

**Fit  in  J/psi X Inclusive  MC sample  **

**Fit in a Bs, Bd  MC sample.  **

-  Our vertexes is working. Errors are meaningful.
-  Find a possible bias

-  Long Lifetime component, better understanding of the background.

##   Understanding Long Lifetime Background I

- Low

- Signal

- Hi

##   Understanding Long Lifetime Background II

## consistency studies

**Full analysis test   **

- We have tested our code in a full simulated MC sample . For the Bs the input was 439 m . We  got  437.3 +/- 5.4 m , same behavior was observed  for Bd .

- Red  All contributions, Green signal,  blue combinatorial: mainly from misreconstruted.

## consistency studies

**Range of Mass selection   **

**Dependence of the Mass **

- All D0 mass peak are slightly shifted  due to magnetic and material uncertainties, instead of use the PDG mass in the PDL definition (slide )  we use the central value of our fit . We found a difference of 0.75 microns.

## We have explored two additional set of cuts , 1)  Maximum S/B (low statistics),  2)Maximum yield (large background). We also split  the sample in several ways.   

- We have explored two additional set of cuts , 1)  Maximum S/B (low statistics),  2)Maximum yield (large background). We also split  the sample in several ways.

-  c(Bs) m

-    Check

-  c(Bd) m

## Linearity     

-  In a Full simulated MC, we fit using various lifetimes  inputs.  Our results are consistents with linear.

- Test of linearity of the lifetime fit, Left Bs MC, right Bd MC.

##  Sumary Results I 

-     With approximately 220 pb-1  in D∅ detector up to february2004. We reconstructed 337(1370) Bs(Bd) candidates  and we have measured the lifetime.
-       (Bs) = 1.444 +0.098 (stat) ± 0.020 (syst) ps.
-      (Bd) = 1.473 +0.052 (stat) ±0.023 (syst) ps.
-       And the ratio
-    (Bs)/(Bd)  = 0.980 +0.075  (stat) ± 0.003 syst
-    D0 conference and analysis notes at:
-   http://www-d0.fnal.gov/cinvestav/d0_private/Analysis/Bs/Bs.html

- -0.090

- -0.050

- -0.070

## Comparison

-    The current world best single measurement.

## Summary results II :

## In progress 

-  Add more  available data.
-  Bd, Bs Angular analysis, integrated in the time.
-  Bs, Bd  time dependent Transversity Analysis.
-  Bs lifetime in the semileptonic channel.

## Backup slides 

## Data Samples

- Luminosity ~ 220 pb-1
- Remove all bad data.

## Bs->J/  

- Bd->J/ K*

- Mass  Distributions with a c/(c) >5

-   N = 259 ± 14

-   N = 1028 ±  36

- Preliminary

- Preliminary

## Establishing the b signal

- (1)

- (2)

- (3)

- (4)