# Presentation: 076294

## The BaBar Program at LBNL (part 2)

**Intro, Online Computing, Offline Computing, Trigger**
**  ****Bob Jacobsen**
**DIRC, SVT, Physics Analysis**
**  ****David Brown**

## DIRC: Detection of Internally Reflected Cerenkov (light)

**Notes:**
Novel PID system, in addition to traditional dE/dx in SVT and DCH

How does it work?  Very well, thank you!

## Current DIRC Members at LBNL

**Physicists**
**R. Aleksan****	****DIRC subsystem Co-Manager (Saclay visitor)**
**D. Brown****	****	****DIRC Commissioner and Online Coordinator**
**J. Kadyk**
**R. W. Kadel****	****Production Manager, ****gas system, water dump**
**G. Lynch****	****	****Offline software**
**M. Pripstein****	****LBNL DIRC group coordinator**
**V. Shelkov ****	****DIRC Online Coordinator and Calibration expert**
**W. Wenzel**
**A. V. Telnov****	****Humidity detection system**
**Division technical support**
**S. Dardin**
**T. Weber**

**Plus LOTS of expert assistance from LBNL engineering**

- Green = former responsibility

## DIRC Components

**DIRC Components**

**Stand Off Box**
**(H****2****O + PMTs)**

**Strong Support**
**(magnet steel)**

**Central Support**
** ****Cylinder**

- Bucking
-     Coil

**Barbox**

- Quartz
- window

- wedges

**Quartz**
**bars**

**Plus...**
** ****Electronics**
** ****Online Software**
** ****Offline Software**
** ****Gas and Water**

**Notes:**
Point out BaBar contributions

## DIRC Milestones

**LBNL Major Mechanical deliverables finished in early 1998.**
**Barbox “****-1****” installed for cosmic ray run in August 1998.**
**Gas and water systems installed in early 1999.**
**Barboxes in slots ****4****,****5**** & ****6**** installed for BaBar commissioning run in March 1999.**
**Successful commissioning of DAQ and calibration system from March-December 1999. **
**Barbox “****-1****” removed, and Barboxes ****0-4****, ****9-11**** installed in-place on PEP-II during 2 week shutdown in October 1999.  BaBar DIRC fully functional.**

**Notes:**
Tooling from LBNL

## DIRC online calibration

***Calibration changes over 8 months***

**March 1, 2000****	****	****                          Nov. 1, 2000**

**Photon Yield**

**Single photo-electron t****0**

**Single photo-electron charge**

- No measurable change in efficiency

**10ns**

**Arb. units**

**Arb. units**

- Stability much better than intrinsic resolution

- Few %/year gain loss

**Notes:**
If you have time, say that DIRC reco was pioneered by Gautier while he was here.

## DIRC Performance

- Angle and timing resolution per photon (3-D device)

***May 2000, Elba Italy                                                                                                                               Vasia  Shelkov, LBNL***

** ********C ****= 9.8 mrad**

** ********t**** ****= 1.71 ns**

- Photon Yield

- Very near to design parameters

** ****N****C**** photons-vs-dip angle**

- Data
- Monte-Carlo

**Notes:**
Want to concentrate on the timing plot next

## PID Performance

********************

**No PID**

**one K id**

**two K ids**

******separation******

**3******** separation to 3.4 GeV/c**

**Notes:**
Natalie will talk about combined PID, but I just couldn’t resist showing some plots at this point

That’s all I have.  My intermediate summary, theme if you like, is “LBNL took on the big, unsung infrastructure jobs critical to long term success, and did them.”

## B0+– and B0 K+–  BR

**BELLE**

## Silicon Vertex Tracker

- Precision Tracking
- Vertexing, Z of B-decays
-    angle at DIRC
- Low-momentum track finding
- Below ~100MeV
- dE/dx for low-momentum PID
- ionization measurement from time over threshold
- High radiation, low accessibility
- Extreme mechanical and thermal constraints

## LBNL Participation

- SVT roles 1994 - 1999
- System  co-manager - N. Roe
- Mechanical Coordinator -    L. Kerth
- Project Mechanical Engineer - F. Goozen
- Electronics Coordinator - F. Manfredi (LBNL/Pavia)
- Project Electronics Engineer -   M. Nyman
- SVT Software Coordinator - G. Lynch
- Cosmic Commissioning Coordinator, Operations Deputy - B. Abbott
- SVT Alignment - S. Kluth
- Current participation
- Replacement module installation - N. Roe
- AToM prouduction and testing, Online Software - Amedeo Perazzo
- Mechanical/Cooling Systems - L. Kerth, F. Goozen
- SVT Alignment - D. Brown, G. Lynch, A. Gritsan

- Green = Left LBNL

## LBNL SVT Contributions

- Mechanical
- Mechanical/cooling system design,integration and  construction
- Optical survey and cosmic test
- Assembly onto beamline
-  Electronics
- Electronics coordination and integration
- AToM IC design (w/UCSC, Pavia)
- AToM production and testing
- DAQ teststands
- Grounding & shielding design
-  Software
- Hit finding, tracking, alignment
- Online software development

## AToM chip for SVT readout 

- A Time-over-threshold Machine
- First deadtime-less silicon readout IC installed in a major experiment
- Designed by LBNL, UCSC and Pavia
- Radiation hard, 4 bit TOT + 5 bit timestamp output
- 193 deep SRAM + 4 output buffers
- sparse readout
- Selectable rise-time & threshold
- built-in calibration
- Installed electronics met all requirements
- No chip failures to-date
- New production run in progress
- Replace bend-plane modules + spares

## ELEFANT chip for Drift Chamber readout

- ELE**ctronics **F**or **A**mplitude **‘N  T**iming - first complete timing and amplitude system for drift chambers on a chip **
**LBNL innovation allows complete DCH readout system to be mounted on the DCH endcap**
**Greatly reduced cable plant, easing mechanical constraints and eliminating >280 off-detector VME cards**
**Designed at LBNL using Mentor CAD technology**
- 0.25M gates, fabricated in 0.8 um CMOS process
**Basic Functionality:**
- TDC with 1 ns bins for drift time
- 6-bit 15 MHz FADC for dE/dx
- Latency and readout buffering, with sparsification
- Prompt trigger output for charged track trigger
- Low power, 8 channels/chip
**All channels are  installed and working, no failures so far**
**Drift chamber performance meets design targets**

## SVT Performance

- Hit Efficiency v Layer

- DOCA resolution

- Hit Resolution vs Theta for Layer 1
-       Data  vs   Monte Carlo

- 90%

- 100%

- 40 um

## SVT Particle ID

**ln(p)**

**Define PID using combined likelihood from all subsystems**
**e = blue****, ********yellow************red****, ****K = green****, ****proton = purple**
**G. Lynch**

**SVT**

- √ **dE/dx**

**curves should**
**go as 1/******

## B-meson Lifetime Results

** ****t****0 ****= 1.506 ± 0.052(stat) ± 0.029(syst) ps**
** ****t****± ****= 1.602 ± 0.049(stat) ± 0.035(syst) ps**
** ****t****±****/t****0**** = 1.065 ± 0.044 ± 0.021**
***             ***

**PDG2000**
**t****0 ****= 1.548 ± 0.032**
**t****± ****= 1.653 ± 0.028**
**t****±****/t****0**** = 1.062 ± 0.029**
**single best**
**t****0 ****= 1.474 ± 0.039 ± 0.051 (CDF)**
**t****± ****= 1.643 ± 0.037 ± 0.025 (OPAL)**
**t****±****/t****0**** = 1.110 ± 0.065 ± 0.033 (CDF)**
** **

- B0 ,B0

- B±

- Presented at ICHEP 2000

## Radiation Dose

- Radiation budget being met
- Highest dose is localized
- Inner modules
- Bend plane
- Abort system is protecting against catastrophic damage
- Small performance loss
- Signal/noise

## SVT Maintenance and Development

- BaBar will maintain the present SVT through 2004
- Must survive £ > 1034 cm-2 s-1, ∫£ > 200 fb-1
- Intervention Is forseen for summer 2002
- Replace modules with highest radiation dose
**inner layers, modules in bend plane**
- LBNL is responsible for:
- AToM procurement and testing
- Removal of SVT from beamline, transport to LBNL
- Dis-assembly of all detector modules, re-assembly, and test
- Re-installation at SLAC
- Test AToM radiation hardness up to 5MRad

## Tracking

**LBNL has made substantial contributions to tracking**
**Kalman fit, material model, SVT reco, ...**
**BaBar tracking still needs work**
**Analysis is currently done with ‘pseudo-tracks’**
**Alternative (non ********) mass hypothesis fits not used**
**Decay length of K****0****s**** , ******** not corrected (material)**
**SVT local alignment is not yet publication quality**
**Problems mostly understood, fixes under development**
**SVT pattern recognition not yet optimized**
**Internal Hit information currently ignored**
**LBNL group is still actively developing (and maintaining!) software**

## Kalman Filter Track Fit

- Helix Fit

- Kalman Fit

**** **Momentum**
**vs dip angle**

- 100MeV

## Survey vs Track-based Alignment

- Wafer-to-wafer spacing from the track-based alignment  were found to be larger than is mechanically possible!
- LBNL has modified the tracking alignment code to include reliable and accurate survey measurements as constraints.

- A. Gritsan

- Layer 5

- Survey - Alignment
- Wafer Z position

## Physics Analysis at LBNL

**BaBar is now contributing to HEP knowledge**
**13 papers submitted to ICHEP 2000**
**World-class measurements on mixing, cp-violation,B-lifetimes, ...**
**LBNL made a few direct contributions to these papers**
**Sin2******** dilutions, resolution error propagation**
**Members on review boards of several papers**
**LBNL made substantial enabling contributions**
**LBNL is very involved in ‘2nd year’ physics analyses**
**Precision results**
**Low-rate signals**

## Analysis Efforts at LBNL

**B****0**** ********D* l ********mixing, form factors)**
**B. Abbott****, B. Cahn, ****K. Copic****, ****C. Flacco****, ****M. Gill****,****	****C. LeClerc****, ****T. Liu****, N. Roe**
**B ********V V (rare charmless decays, direct ****CP****)**
**D. Brown, ****A. Breon****, A. Gritsan**
-  ** ********K(********) ******
**V. Shelkov, ****Y. Grossman**
**B ********a****0********Angle ********)********B. Cahn, V. Shelkov**
**BR (B ********l********) (f****b****) ****	****	****G. Abrams**
**V****ub ****from q****2**** (B ********l******** X)****	****	****A. Romosan**
**BR(B ********D********P. Strother**
** **** ****lifetime****	****	****	****	****A. Meyers**

- Student
- Left LBNL

## B0 D* l mixing (md)

- z = ct ~ 260m

** ********m****d ****sensitive to |V****td****V****tb*****|**
**First time-dependent measurement on ********4s**
**B****0**** ********D* l ********is experimentally clean**
**D*********D******** is very narrow (little phase space)**
**Background rate low**
** ********m****d**** systematics can be well controled**
**Thesis subject of C. LeClerc**

- Signal B
- B0 D* l 

- ‘tag’ B
- B0  X l 
-  K X,
-  hadrons

## B0 D* l mixing (md)

******t between ****D* l ********and tag B****0**

- Unmixed (tag charge ≠ l charge)

- Mixed (tag charge = l charge)

- Mixed-Unmixed
- Mixed+Unmixed

- ±1

- ±5 ps

- = D cosmdt

- Very Preliminary

## B0 D* l Form Factors

**Why study Form factors?**
**FF relate decay rates to fundamental physics**
**CKM matrix parameter |V****cb****|**
**FF can be compared to models (HQET)**
**Why B****0**** ********D* l ********?**
**Large BR (~5%)**
**Experimentally tractable**
**Measure angles**
**BaBar should improve ~x3****	****	****	****	****	****world average precision**
**Statistically limited measurement**
**Thesis topic of M. Gill**

##  K() 

**Existing measurements (CLEO) are incomplete**
**B(**** ********K************(2.7±0.6)x10****-4**
**B(**** ********K*************(3.4±0.9)x10****-4**
**Resonant substructure unknown**
**Cleo has a limit B(**** ************1.4x10****-4**
**SM expectation ~1.6x10****-5 ****(2nd class current)**
**Sensitive to up,down mass difference**
**a****0****(980) resonance channel**
**Background from **** **************
**Both measurements need high statistics, PID!**

##   K

- Very Preliminary

**Standard ********, ****K identification**
**Use ****sidebands to determine the combinatoric backgrounds**
**~100% feeddown K*(1410) ********K**

## B V V (charmless)

**Sensitive to**
**b********s, b********u transitions**
**direct ****CP**
**Fully hadronic final states**
**must reduce backgrounds!**
**Polarization, Energy + momentum constraints**
**New ‘skim’ needed to select these states**
**High efficiency (>50%)**
**Low total rate (<10%)**
**Lots of modes**
**First results expected****	****	****	****	****	****early next year**

## B a0Angle )

**Angle ******** measurement with B ********hh is difficult**
**B ********suffers penguin ‘pollution’**
**B ********K********rate large (dominant?)**
**B ********may be more promising**
**Requires isospin analysis to extract ******
**Resolve hadronic phase ambiguities**
**Many cross-terms must be evaluated**
**B ********a****0********may be even more promising**
**Rate ~comparable to B ******
**a****0**** resonance is 3X narrower than ******
**Cleaner signal, lower interference**
**Fewer isospin cross terms**
**a****0**** is scalar, ******** is vector**

## B a0

**Promising new analysis (V. Shelkov)**

**Plot of ********E (B - beam) difference against reconstructed mass**

- Simulation

- BaBar

**Intentionally left**
**Blank (blind analysis)**

## BR (B l) (fb)

**Physically very relevant**
**Connects semi-leptonic rate to |V****ub****|**
**Connects ********Md to |V****td****|**
**Experimentally difficult**
**Low rate to ********,e (helicity suppression)**
** ******** ****mode (BR~5x10****-5****) has many neutrinos**
**Must reconstruct opposite B**
**reduce backgrounds**
**Need partial B reconstruction**
**B ********D* X (********,********,...)**
**D********s****Y**
**Efficiency ~ 60% for B ********D*******

- CLEO
- Monte Carlo

**B******

## Summary

**LBNL has been essential to the success of BaBar**
**major hardware, software & leadership roles**
**We continue to play important roles in many areas**
**We need to maintain our involvement with BaBar while focusing more effort on physics analysis **
**To accomplish this, we need more postdocs**
**Six**** have left (or are leaving) for tenure-track positions since January 1 2000**
**One**** (+one) has been hired**
**In spite of our staffing problems, we are making good headway into the physics of BaBar**
**Look for conference results next year**