The impact of HERA PDFs on LHC physics

1
x
x
Plots of xf vs. x for a variety of Q2 values,
showing errors due to uncertainty in quark
distribution (total sea contribution). This is
for d-type quark contributions (shown at recent
ATLAS physics week).
Oliver Harris, progress report 15/11/04
2
Q2 5x105
Q2 2x106
PDFs as a function of x, for 2 values of
Q2. Errors shown are contribution from ONE of
TWELVE parameters. Total errors are 1 order of
magnitude larger.
Oliver Harris, progress report 15/11/04
3
Q2 1x104
Q2 1x105
Plots of xf against Q2 are work-in-progess I
can plot these only with arbitrary axis scales
(output data has different scales for different
regimes in Q2 quite involved to rescale it for
a log scale in ROOT).
4
(after J. Stirling/J. Butterworth) Plot showing
kinematic regime of LHC compared to Tevatron and
HERA Q2max and x region of my analysis shown
in red box. Precise measurements of threshold
effects in, eg., Higgs, SUSY, top physics, will
require precise knowledge of PDFs at high Q2
mid-to-high x gluon esp. important for Higgs
production. Also vital for new forces, such as
ADD models (Ferrag et al).
5
To do/work-in-progress use new PDFs to generate
NLO x-sections up to pT of several TeV, use MC
to apply parton showering and hadronisation
corrections, then pass data though ATLFAST
simulation, investigate impact on x-sections for
key processes (Higgs, SUSY) and also QCD
background, compare errors on x-sections due to
gluon PDF uncertainties to statistical errors
after 100 fb-1 of data, perform feasibility
study on discovery channels for new
physics processes, in respect of uncertainties in
QCD, and maybe look at how the LHC itself can
constrain PDFs in early running phase. (HERA
wont be around forever!)