# Presentation: 803354

## Recent Results from D0

- Vivek Jain
- Brookhaven National Lab
- (D0 Collaboration)
- Beauty 2003

## Slide 2

## Pre-shower detectors help in e-ID

- Barrels and Disks

## Excellent Tracking acceptance: 

- These are MC estimates – checking in data

- Efficiency

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

## All tracks

- Analysis cuts – pT>0.7 GeV

**σ****(DCA)≈53****μ****m @ P****t****=1GeV**
**and better @ higher P****t**

##  Excellent Lepton Acceptance

- Muon ID:

- MC:

- of reconstructed muon – very tight ID

- Overall efficiency (from data)
- plateaus at about 85-90%
-                - at    pT    4.5 GeV
-                         pT    3.5 GeV
-                - at   pT     2.5 GeV

## Electron ID:

-  Low pT electron ID is in progress
-  At present, we can detect electrons with pT>3 GeV and
-      Average efficiency is about 75%
-  Working to extend to higher values of         and lower pT
-      threshold

## Silicon Track Trigger is built and is being commissioned

- Silicon Track Trigger is built and is being commissioned
- Expect to start taking data soon after the shutdown

- Track Fit Card

## B Physics Program at D0

-  Unique opportunity to do B physics during the current run
-  Complementary to program at B-factories (SLAC, KEK)
-         mixing,
-  Rare decays:                      In some SUSY models rate is large
-  Beauty Baryons,          lifetime...
-  Other particles, e.g.,
-  Quarkonia -               production, polarization ...
-  No dedicated Particle ID – Silicon provides limited separation

- b production cross-section: In Run I, measd. Rates x(2-3) higher

## Is not used yet for PID

**Is not used yet for PID**

**Can provide**
** ****K/****π**** separation for P****tot****<400 MeV**
** ****p/****π****  separation for P****tot****<700 MeV**

##         Mixing is high priority 

- We need:
- Final State reconstruction (Eckhard Von Toerne’s talk on Wed.)
- Ability to measure B decay length (Daria Zieminska’s talk on Thurs.)
- B flavour at decay and production (Ting Miao’s talk on Thurs.)

- Significance of mixing
- measurement

## One can reconstruct           in hadronic and semi-leptonic modes

- Hadronic modes, e.g.,
-      Pros: Very good proper time resolution
-      Cons: Low branching fraction (              ), triggers
-  Semi-leptonic modes, e.g.,
-       Pros: Large Branching fraction              , triggers
-                Use both Muon & Electron final states
-       Cons: Poorer proper time resolution

## SL modes have large yields

## Use for           mixing, lifetimes, etc.  

- Use for           mixing, lifetimes, etc.

## Inclusive B lifetime using 

- Inclusive B lifetime using

##  Also looking at hadronic modes

-  Also looking at hadronic modes
-  Plan to reconstruct the semi-electronic final state
-  Working on getting an estimate of the proper time
-      resolution for the semi-leptonic mode – this is
-      crucial

## Flavour tagging

-  To get flavour of B at production use
-    Soft-lepton tags – High tagging power, low efficiency
-    (SL decay of other B)
-    Jet Charge tag    - Poorer tagging power, high efficiency
-    (track-jet from other b quark)
-    Same Side tagging - Poorer tagging power, high efficiency
-    (fragmentation, B**)

## Use the                       signal to benchmark the flavour tags

- 300 K events

## Make track jets for jetQ tag

- Require |Q| > 0.2

- MC

- (B+ MC)

## Same Side Tag Algorithm

- One source of pions for same side tags

- Make cone (dR<0.7) around
-  Remove tracks belonging to
-  Choose track with highest pT
-      (try other criteria too)
-                     means correct tag

## Same Side Tagging

- D0 RunII Preliminary

## Will also use electrons

| Method | Epsilon

 | Tagging power or
Dilution (D) | Figure of
Merit

    (%) |
| --- | --- | --- | --- |
| Soft Muon | 5% | 57% |                     |
| Jet Charge | 47% | 27% |  |
| Same Side | 79% | 26% |  |

- Results based on       signal – D0 RunII Preliminary

- Investigating with

## Triggers:

-  Most useful trigger for mixing is the low pT inclusive single muon trigger (pT > 2-4 GeV, depending on η)
-       We can use it for                              and
-                                  and                             -          used as flavour tag
-  Can also use dimuon trigger for semi-muonic mode
-  Investigating trigger/DAQ upgrade for B physics

## Projections for 500 

- Yield – 15K

- Single Muon Trigger:

- Di-Muon Trigger:

- Yield – 2K

- Also applies
- for electron
- events on
- Single Muon
- trigger line

- Current limit

## Projections for 500 

- Single Muon Trigger:

- Projections for 500

- Yield – 700

- one decay mode

- We can combine the SL and
- hadronic modes and obtain
- a better limit/result

## Quarkonia at D0

-      -   Cross-section as a function of pT and  η
-  Started to look at Upsilon production characteristics
-      - We presented a preliminary pT distribution at QWG’03
-      - Once we re-process our data, we will also produce
-         absolute cross-sections.

## Slide 27

## Conclusions

-  Making good progress in understanding
-      our detector – lifetimes, flavour tags ...
-  Measure           to benchmark analysis tools
-  Investigating Trigger/DAQ upgrade for
-      B physics
-  Exciting times ahead...

## Backup Slides

## Details of flavour tagging

| method | # N_total | #N_R | #N_W | Efficiency 
    (%) | Dilution
   (%) | (%) |
| --- | --- | --- | --- | --- | --- | --- |
| Muon | 1964 | 63 | 37 |  |  |  |
| JetQ | 1020±55 | 301±25 | 174±22 | 46.7±2.7 | 26.7±6.8 |  |
| Same Side | 1025±52 | 507±30 | 295±25 |  |  |  |

## 5. Estimating efficiency & dilution for signal events

-  This corresponds to 968.7 (1046.8) background (signal) events.
-  I’m using the sideband tagging efficiency (4.9±0.3)% as the background tagging efficiency
-  We have 100 tagged events in the mass window; (4.9±0.3%)×968.7 = 47.5±3.0 of those
-    must be background.
-  So, the # of signal events must be 100−47.5=52.5±3.0; this gives a signal efficiency
-    of 52.5/1046.8 = (5.0±0.7)%
-  If I write down the raw dilution as
-  after some math I end up with
- where *α*: the fraction of signal events in tagged sample (52.5/100)
- and *D*bgd: the sideband’s dilution (−8.2±6.4 %)

**5. Estimating efficiency & dilution for signal events**

## Same side tagging

## Track Fit Card (TFC) Design

-     Performs final silicon cluster filtering and track fitting
- Lookup table used to convert hardware (e.g., channel, etc.) to physical coordinates (        )
- 8 300-MHz 32-bit integer Texas Instruments DSPs perform a linearized track fit
- Fit using precomputed matrix stored in lookup table

##  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

## SM expectation 

- SM expectation

- (95% CL)