The BTeV Pixel Detector and Trigger System Simon Kwan Fermilab P.O. Box 500, Batavia, IL 60510, USA BEACH2002, June 29, 2002 Vancouver, Canada

The BTeV Spectrometer

Pixel Vertex Detector Reasons for Pixel Detector: Superior signal to noise Excellent spatial resolution microns depending on angle, etc Very Low occupancy Very fast Radiation hard Special features: It is used directly in the Level 1 trigger Pulse height is measured on every channel with a 3 bit FADC It is inside a dipole and gives a crude standalone momentum

Hybrid Silicon pixel devices Independent development and optimizations of readout chip and sensor n + pixels on n-type substrates: inter-pixel insulation technology under investigation Bump-bonding of flipped chip: 2 technologies being considered: Indium (In) and solder (SnPb) 0.25  m rad-hard FPIX2 chip

Comparing to other Pixel Detectors Experiment Property ALICE Pb-Pb Collider ATLAS p-p Collider CMS p-p Collider BTeV p-pbar Collider Pixel Size 50  x 425  50  x 400  150  x 150  50  x 400  Min. distance to beam 40 mm 43 mm (B) 101 mm 41 mm 70 mm 6 mm Number of Pixels 16 x x x x 10 6 Total Active Area 0.26 m m m m 2 Material X o per plane 1.4 % 1.80 % 1.62 % 1.65 % 2.3 % 1.2% Special Features 50 tracks/cm 2 4 bit TOT ADC Low luminosity inner layer Level 1 Trig 3 bit ADC Luminosity at FermiLab detectors 2x10 32 cm -2 sec -1 Luminosity at LHC detectors 1x10 34 cm -2 sec -1

BTeV Radiation Background (L=2·10 32 cm -2 s -1 ), charged hadrons Pixels, Z = (55 – 60) cm

Irradiation Results: Pixel ROC

Silicon Sensor R&D: V dep vs Fluence

High density flex circuit development 15 HDI delivered from CERN; only 4 without defects Preliminary performance assessment very satisfactory  design validation We need to do more extensive tests and find commercial vendor for large scale production

Built 10% Model

The Pixel Detector (2-D Side View)

Physics Performance of Pixel Detector Distribution in L/  of Reconstructed B s Primary-secondary vertex separation Minus generated.  = 138   proper (reconstructed) -  proper (generated)  = 46 fs Mean = 44

The BTeV Level I Vertex Trigger Key Points –This is made possible by a vertex detector with excellent spatial resolution, fast readout, low occupancy, and 3-d space points. –A heavily pipelined and parallel processing architecture using inexpensive processing nodes optimized for specific tasks ~ 3000 processors (DSPs). –Sufficient memory (~1 Terabyte) to buffer the event data while calculations are carried out. The trigger will reconstruct every beam crossing and look for TOPOLOGICAL evidence of a B decaying downstream of the primary vertex. Runs at 7.6 MHz!

Generate Level-1 accept if “detached” tracks in the BTeV pixel detector satisfy: (GeV/c) 2 cm L1 vertex trigger algorithm Execute Trigger

L1 trigger efficiencies ProcessEff. (%)Monte Carlo Minimum bias1BTeVGeant B s D + s K - 74BTeVGeant B 0 D* +  - 64BTeVGeant B 0  0  0 56BTeVGeant B 0 J/  s 50BTeVGeant B s J/  *0 68MCFast B - D 0  - 70MCFast B - K s  - 27MCFast B 0 2-body modes 63MCFast (             )

Level 2 Trigger Start with the Level 1 tracks from the ``triggering collision” within the crossing. Search for pixel hits along these tracks. Refit the tracks using a Kalman Filter. Resultant momenta are improved to about 5-10%. Resultant event must satisfy one of the two following criteria: –A secondary vertex must be present or –The collection of tracks must satisfy a minimum p T cut. The combined L1 and L2 rejection is Overall Efficiency is roughly 50% for most B decays of interest.

Summary Great progress has been achieved in the design of the sensor, front end electronics and module structure of the BTeV pixel detector We are making rapid progress towards a full system design that satisfies all the BTeV requirements This vertex system will be the key element of the Trigger algorithm that will enable efficient collection of a variety of beauty decays & provide a superb tool to challenge the Standard Model