# Presentation: 662809

## EbE Vertexing for Mixing

- Alex
- For the LBLB group

## Improved studies on pulls

- Increased sample’s statistics
- Full ~350 pb-1
- Working on including K3 and K
- Tested the effect of run# dependent hourglass parameters
- Improved fit (core of pulls now defined as 2)
- G3X refit: no difference in pulls
- Started work on SV pulls
- The current situation is summarized in the next table... (same trends, slightly different numbers)

- New this week!!!

## Extended x-checks

|  | BD0[K] |  |  |  |  | BD+[K] |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| Beam constr. |  |  |  |  |  |  |  |  |  |  |
| Hourglass from DB |  |  |  |  |  |  |  |  |  |  |
| Exclude DB-less |  |  |  |  |  |  |  |  |  |  |
| PV scale factor | 1.0 | 1.38 | 1.38 | 1.38 | 1.38 | 1.0 | 1.38 | 1.38 | 1.38 | 1.38 |
| d0 Beam (hourglass) | 1.17 | 1.17 | 1.19 | 1.13 | 1.12 | 1.15 | 1.1 | 1.12 | 1.07 | 1.05 |
| d0 EbE | 1.33 | 1.07 | 1.18 | 1.17 | 1.15 | 1.30 | 1.11 | 1.15 | 1.14 | 1.13 |
| d0 EbE (SV rescale) | 1.24 | 1.02 | 1.10 | 1.10 | 1.09 | 1.26 | 1.06 | 1.09 | 1.08 | 1.07 |
| X1-X2 | 1.40 | 1.02 |  |  |  | 1.39 | 1.02 |  |  |  |
| Y1-Y2 | 1.40 | 1.01 |  |  |  | 1.36 | 1.0 |  |  |  |
| Z1-Z2 | 1.39 | 1.00 |  |  |  | 1.31 | 1.1 |  |  |  |

## How universal is the PV Scale Factor?

## Scale factors From SecVtx code

- X 4.11.1

- Y 4.11.1

- Z 4.11.1

- X 5.3.1

- Y 5.3.1

- Z 5.3.1

## Z dependency in D samples

- Z dependency in D samples

- D+ and D0 samples
- No indication of a structure (flat?)
- Smaller statistics, but main features should be visible!
- Final statistics will be ~2x

## # tracks dependency in D samples

- # tracks dependency in D samples

## # tracks Pt>2 dependency in D samples

- # tracks Pt>2 dependency in D samples

## <Pt> dependency in D samples

- <Pt> dependency in D samples

## Bottomline for PV scale factor

- The scale factor seems pretty universal
- No dependency on:
- Z, #tracks, momentum
- Will improve statistics (D0K, BK(*)
- Contribution to Lxy scale factor from the PV seems pretty consolidated at this point
- ...on to the Secondary Vertex!

## Secondary Vertex

## Scale factor from B decays

- BK+
- Fit  to a single vertex
- Measure Lxy wrt B vertex
- Pull is a proxy for a “seconday vertex” pull!

- K

- 

- 

- B

- Primary Vertex

## First look at dependancies

- Z

- Pt

- Lxy

## Conclusions, so far

- A scale factor is needed for SV too
- Not too different from the PV sf
- Statistics of sample too small to get dependencies!
- Alternative samples:
- D+, BK*, tracks from primary

## Moving along the plans for improvements!

- Understand beamline parameterization:
- Is it modeled correctly
- Is it measured correctly
-  Include our best knowledge of it!
- Are secondary vertex pulls ok?
- Check with montecarlo truth
- Use n-prong vertices (J/K, K+/0, K+/0)
- Investigate dependencies (Pt, z,multiplicity, ) with full statistics

## Backup

## Outline

- Current status
- What was used for the mixing results
- What is the current understanding of Ebe
- Plans for improvements
- How can we improve?

## Current status

- Hourglass

- EbE: itearative track selection/pruning algorithm to provide an unbiased estimate of the PV position on an Event-by-Event basis
- Hadronic analyses used a flat ~25um beamline!
- Possible improvements:
- Move to “hourglass”
- Move to EbE
- EbE + Hourglass
- One of the 1⁄2 leptonic
- analyses used this with
- fixed hourglass parameters

## What do we know about EbE?

- Unbiased estimator of PVTX

|  | Transverse | Z |
| --- | --- | --- |
| Data (V1-V2) | 1.330.035 | 1.370.035 |
| MC (V1-V2) | 1.1920.034 | 1.260.035 |
| MC (V-truth) | 1.240.036 | 1.230.032 |
| J/ Prompt Peak | 1.2360.024 | ~ND~ |
| J/ d0/ | 1.1760.019 | ~ND~ |

- Reasonable (~5%) control of systematics

## Cross checks using I.P.(B)

- Lxy involves three ingredients:
- EbE
- Secondary vertex
- Beamline (in beamline constrained fits)

- Z dep. Beamline improves pulls!

- Scale factors work!

- Something funny when beamline is used!

- B

- d0

- Lxy

## Time dependence of Hourglass parameters

- Implementing DB access of time-dependent parameters

## What do we gain?

- 15-20% In vertex resolution!
- Better control of systematics (hard to evaluate)
- Correct EbE resolution (it is not clear that it is correct now)

- Red arrow is the effect of 1. Only
- Point 2. Affects mostly the green area (tiny ?)
- Point 3. Has an effect qualitatively similar to 1., but hard to evaluate

- Euphemism

## Hadronic analysis systematics

- ct scale factor                        0.000   0.024   0.061   0.090  0.144

## Hourglass parameters from DBProfiles

## SV contribution

- 

- 

- K

- d0(K)

- Moments to the rescue:
- Example BK
- Fit  vertex alone
- Look at d0(K) wrt  vertex
- Can repeat this study with other multi-prong vertices (D+, D0 etc.). Result might depend on:
- Momentum
- Vertex multiplicity
- Plenty of statistics to study all this

- Cross check the study on MC, after shimming L00 efficiency

## X1-X2 pulls binned in 10 Z bins in (-51.0,51.0) cm

- X1-X2 pulls binned in 10 Z bins in (-51.0,51.0) cm

## Y1-Y2 pulls binned in 10 Z bins in (-51.0,51.0) cm

- Y1-Y2 pulls binned in 10 Z bins in (-51.0,51.0) cm

## Z1-Z2 pulls binned in 10 Z bins in (-51.0,51.0) cm

- Z1-Z2 pulls binned in 10 Z bins in (-51.0,51.0) cm

## Planned Improvements:

- PV pulls w Beam Constraint  need to revisit modeling of beamline
- Use of run dependent hourglass parameters
- Hints of difference in the relative contributions of PV/SV to Lxy and d0  need additional methods to study SV resolution

- Where are we?

## The tools

- Prompt peak
- V-truth
- V1-V2
- d0/

- B

- d0

- Lxy

## Relative PV/BV contribution to d0 and Lxy pulls

- B

- d0

- Lxy

- PV and BV are linear combinations of the same covariances (PV, SV), with different coefficients
- Lxy sensitive to the major axis of SV
- Relative weight of PV and SV covariances different for Lxy and d0
- Look at:

- w

- w

- Note: the two Lxy (or d0) pieces do not linearly add to 1!

## Relative PV/BV contribution to IP and Lxy pulls

- B

- d0

- Lxy

- Not Beam Constrained
- Beam constrained
- Beam constrained with run-dep. hourglass

## Bottomline:

- SV and PV enter very differently in Lxy and d0
- Relative contribution depends strongly on PV and SV scales
- Beam constraint squeezes the PV resolution significantly. Becomes second order on Lxy!
- We are in a regime where the SV scale factor is critical!
- ... now let’s get more quantitative!