# Presentation: 832038

**B Reconstruction **
**& **
**Spectroscopy **
**at DO**
**Eckhard von Toerne**
**Kansas State U.**
**October 15****th****, 2003**
**(presented by Vivek Jain)**

## B Spectroscopy at the Tevatron

**Positive aspects:**
**All b hadrons are produced (B0 B+ Bs Bc ********b****)**
**Huge cross section -  **
**Negative aspects:**
**Almost overwhelming QCD background**
**Reliable reconstruction necessary**
**Efficient triggers needed**
**Soft Pt spectrum ******** lower boost compared to LEP**

## Accelerator performance

|  | Run Ib | Run IIa | Run IIb |
| --- | --- | --- | --- |
| # bunches | 6X6 | 36X36 | 140X133 |
|                
    (TeV) | 1.8 | 1.96 | 1.96 |
|  | 1.6E31 | 8E31 | 2-5E32 |
| Bunch x-ing
(ns) | 3500 | 396 | 132(?) |
| Int./x-ing | 2.8 | 2.4 | 2-5 |

- Currently

**Have**

## Track Reconstruction

** **

**Pre-showers used**
**for electron-ID**

**Tracker radius 20-50 cm**

##  Silicon Microstrip Tracker:

-  Silicon Microstrip Tracker:
-  6 Barrels: 4-layers, Single/Double sided,
-     2/90 deg. stereo,  |z|<0.6 cm, Radius: 2.7-10 cm
-  12 Central F disks: D-Sided,      15 deg stereo
-   4 Forward H disks: S-sided,     7.5 deg stereo,
-         |z| =     1.1/1.2 m, Radius: 9.5-20 cm
-  Tracking to

- Rad. hard to
- 1 MRad

- 793K channels
- >95% active

- Hit resolution is 10
- Signal/Noise > 10

## Excellent Tracking acceptance: 

- These are MC estimates – checking in data

- Efficiency

- SMT+CFT for |η|<2
- SMT only for |η|>2

## Muon ID

-  Central and Forward regions,
-  Three layers: one inside Toroid, two outside
-  Muon system can be used standalone to get pT information
-  Fast enough to be in L1 trigger
-  Overall Efficiency plateaus at about 85-90% (measd. in data)

## Triggers

** ****Data were taken with**
**    ****- Dimuon trigger **
**    ****- Single Muon trigger (matched to L1 track)**
** ****Muon pT>2-4 (function of η)**
** ****Dimuon trigger is unprescaled**
** ****Single Muon trigger is (at times) prescaled **

## Basic Particles

## Basic Particles (contd.)

****events

**Trigger on soft dimuons**

**Single Muon trigger**

**also used for incl. **B **lifetime**

## Benchmark B decays

**157 events**

**509 events**

**1235 events**

**Flavour tag studies**

## Bs andb

- Need to fix our mass scale
-  and

**    ****- **
**    ****-                       **
**    ****-                              **
**    ****-                          **
**    ****-**
** **

- Range is from
- CDF RunI yield,
- Ratio of Bc/B+  prod.
- (               )
- and our B+ yield

- Extrapolated from B+ had/SL br. fractions

**Event Estimates for **

**Also study **
**other B-baryons**

**All modes use,**

## Bs Semileptonic samples

- Use for Mixing studies

-  Impact Parameter cuts on
-     charm meson daughters
-  Pt of π/K > (0.7-1.0) GeV

## Bs  

**Rare B decays allow us (among other things) to search for new physics**
**Need to consider processes where Standard ****model contribution is small**
**Good example: b******** s ******** or**** ****B****s**** ******** ******

**SM prediction BR(B****s********±**********
**MSSM [large tan(********)] models can enhance rate by**
**   ****2-3 orders of magnitude**

## Lot of background

**Lot of background**

## Bs  

**Background rejection via**
**Decay length**
**P****t**
**Muon Isolation**
**At the moment,**
**  ****used “square” cuts.**
**  ****Looking into Neural**
**  ****Net/Likelihood approach**
**  ****Eff could increase by**
**  ****20-30%**

##  Bs  

**BR(********s********) < 1.6 10****-6**
**@ (90% CL)**

**No candidate excess in signal window **
**Observed 3**
**Expected 3.4 BG**
**   ****(****Feldman-Cousins****)**

**Normalize to B+/Bs **
**       ****final states**

## Single Muon Samples

** ****small opposite-sign background**

## Single Muon Samples

-  No explicit pT cuts
-      on K/π tracks
-  Imp. Parameter cuts

-  Much tighter cuts,
- e.g., IP of K/π > 7 or
- pT > 2

## B**0

**4 different unresolved B** states expected**
**   ****(within 150 MeV)**
**N=65 ****± ****17**
**Mass = 5.71****±****0.016 GeV**

**Compare to PDG: M= 5.698****±****0.008 GeV**

## Chi_c Reconstruction

**In Run I, large production rate for direct J/Psi ****(1-2 orders of magnitude larger than model expectations, e.g., Colour Singlet)**
**Expectation was that most of the direct charmonium would be****     (CDF measured the**
**  ****fraction of J/Psi from     to be        )**
** ****Use                mode, where            **
**   ****good resolution**

##  pT(γ) > 1.0 GeV

-  X-ray of the detector!
-  Also use to tune material
-      in MC (we are now seeing
-      capacitors on SMT
-      hybrid!)
-  pT(γ) > 1.0 GeV

##  Need to understand

-  Need to understand
-     efficiency before we
-     can make a statement
-     about relative production
-     ratio of the two states

## Conclusions & Outlook

** ****Making good progress in understanding**
**    ****detector, e.g., mass scale...**
** ****Lots of fully reconstructed B hadrons**
** ****Look for B-baryons,    ...**
** ****Exciting results down the road**