11th Workshop on Electronics for LHC and future Experiments

A Tracking Detector for Triggering at SLHC

16 Sept 2005, 11:30

25m

Heidelberg

Oral Plenary session P9

Speaker

Mr John Jones (Imperial College London)

Description

We report on preliminary design studies of a pixel detector for CMS at the Super-LHC. The goal of these studies was to investigate the possibility of designing an inner tracker pixel detector whose data could be used for selecting events at the First Level Trigger. The detector considered consists of two layers of 50x50 m2 pixels at very close radial proximity from each other so that coincidences of hits between the two layers amount to a track transverse momentum cut. This cut reduces the large amount of low momentum data expected at SLHC whilst it keeps the tracking efficiency very high for high transverse momentum tracks

Summary

Currently groups of researchers are actively discussing
possible scenarios of upgrades of the LHC machine. According to the
most financially realistic scenario the LHC will be upgraded to
provide proton beams of an order of magnitude larger intensity (1035
cm-2 sec-1) colliding at twice the frequency (80 MHz) of the
present design but have the same centre of mass energy. This machine
design is commonly referred as the Super LHC and it is expected to
be operational after 2015.
A consequence of this design is that the backgrounds due to minimum
bias events will increase by at least a factor of 5. This imposes
severe requirements on the CMS detector.

The occupancy of a tracking detector at SLHC has been calculated
using a Monte Carlo. As an example a pixel detector of 1.28cm1.28cm
with 256256 pixels 5050m2 each positioned at radius of 10 cm away
from the beam will suffer from a background of 4 hits/12.5nsec
dominated by low momentum particles. This is clearly an enormous
rate of data to be transported out of the detector and be used for
the trigger decision. Hence, there is an urgent need for a tracking
detector that has the capability to reject the large amount of low
momentum background locally.

A two layer pixel detector has been simulated using PYTHIA. The
radial separation is of the order of 1-2 mm. The two layers can
communicate with each other electronically and several algorithms
have been explored which put the hits from the two layers in
coincidence using fixed search windows. The effect of the layer
reparation versus data reduction and window size has been
extensively studied. It has been demonstrated that the data can be
reduced by several orders of magnitude without and lose of tracking
efficiency for high transverse energy tracks.

Presentation materials

Paper

paper

paper

Slides

slides