1

PP Minimum Bias Triggering Simulations

Alan DionStony Brook University

2

A simple event generator to simplify simulations

Geometry

Triggering algorithm

Results without noise

Results with noise

Conclusions

Outline

3

Event generator for pp minimum bias events

Nch given by a negative binomial distribution

P n , n , k n k 1k 1

n k1 n k

n1

1 n k k for s 200 Gev , n 21.2k 4.8

Kinematic distribution of particles: assume pt , h, and f factorize

Random distribution in f

For h, assume constant distribution for |h| < 2, and distribution decreases linearly to 0 at h = 6

4

For pt , use fit to UA1 spectrum

Ed 3

dp3A

1 pt p0h for s 200GeV ,

A 315mb GeV 2

p0 1.72GeVh 11.77

Ed 3

dp3 ~ dNd pt

21

2 pt

dNdpt

and so dNdpt

~pt

1 pt p0h

Simple field approximation

Df Df/2

Df/2h

R1

Constant 1.2 T cylindrical field with detector layers at R1 and 2 R1

.3 Bdlpt

with Bdl 1.2 T .05 m .018

pt is in GeV/c

2 arctan hR1

~ hR1

tan .009pt

~ .009pt

h R1 tan2

5

Geometry

2 pixel layers, one at R=2.5 cm and the other at R=5 cm

Utilize the fast OR of all pixels in a given chip

For given z, inner layer has 10 channels and outer layer has 20 (in f)

Each layer has 16 channels in z for given f

2 30 degree gaps in f coverage

95% channel efficiency

6

Triggering algorithm Find all f channels in the inner layer which have a hit and a

corresponding hit in one of the 2 channels in outer layer with the same f

For each such channel, pair each outer hit and inner hit, and fill 3 bins along the beam axis. Each bin has the same size as a detector channel.

Find the bins on the beam axis which have the maximum number of hits. If all such bins are within the acceptance, then we trigger.

7

Dependence on zvertex

8

Dependence on Nch

9

Noise

Efficiency = # triggered events in acceptance / # events in acceptance

Rejection = # non-triggered events outside acceptance / # events outside acceptance

10

To do

Get realistic figures for the channel efficiency, geometry, etc.

Get estimate for the noise per chip

The algorithm can easily be improved to make noise less of a problem