1. Adam Phillips, Fergus Wilson
The Herwig Minimum
Bias Model
University of Bristol
Adam Phillips, Fergus Wilson
& Nick Brook
Final Tuned Version
Herwig vs Tevatron
Herwig vs Pythia
Conclusions and Plans

2. Preferred parameter set for tuned Herwig minimum bias model:
pmbm1 = 0.1
pmbm2 = 9.0
pmbn1 = 8.0
pmbn2 = 0.12
pmbn3 = -7.0
pmbk1 = 0.03
pmbk2 = 0.12
pmbp1 = 6.5
pmbp2 = 5.0
pmbp3 = 7.5

3. Model gives reasonable
description of data

4. But, not entirely satisfactory - Improves on default model...
but unable
to recreate
energy
dependence
over whole
UA5 energy
range

5. Herwig vs Tevatron
Comparison to dnch/dh
from CDF
It fits!

6. Herwig vs Pythia minimum bias at 14TeV Choice of scale chosen to be
the same in the 2 generators:
as at same order
Single diffraction turned off in Pythia
Same pdf’s…

7. Herwig vs Pythia at LHC and multiplicity Pseudorapidity
Pythia  larger h’s and greater nch with
larger tails

8. Conclusions and Plans Herwig can describe (most) data
from UA5 and Tevatron (1 order of magnitude)
Herwig vs Pythia: same ballpark but significant differences
Plans: further comparisons
diffraction
b physics
sensitivity to pdf’s