Minutes from the video meeting of the PDF subgroup
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March 30 2005 10am CST


Agreed to collect relevant information and link to the PDF Subgroup Web page:

  http://hep.pa.msu.edu/~wkt/Conf/TeV4LhcPdf/

- Wu Ki's talk from the First Fermi Tev4LHC meeting gave a broad
  outline

- Joey's list presented at Brookhaven and at HERA4LHC included more
  specific projects

- Markus Wobisch: A fast computation of cross sections in hadron-induced
  processes.

- Link to collection of simulated data sets


Wu Ki wrote a agenda for the group which is linked to the page. This outlined
topics and projects for which we intend to work on.

There was a discussion about adding a non-perturbative (intrinsic) component
for heavy flavors and see what would be allowed by the current data. Provide
extreme PDF fits and extrapolate to LHC energies to see how the prediction for
some important cross section would change.

- W/Z production
- Impact on single top production
- Higgs production


We talked about going from the abstract (Feynman diagrams) to a concrete
measurement. It is not immediately clear what distributions would be the best
to use nor what measurements would actually be possible.

There should be an interplay between theorists and experimentalists to define
the set of measurements

- Pt distribution
- Rapidity distribution
- how low/high in pt
- how far in rapidity

For example tagged heavy flavor was one area that would be interesting to
help constrain the PDFs. To see if the measurement is actually possible one
can do "back of the envelope" calculations to see if the signal can be
extracted. This would roughly take into account acceptance, eta, pt,
efficiencies and consider systematic errors.


We thought it would be useful to catalog the current measurements that CDF and
D0 are working on, to see what has already been published and what will be
available soon. We can then discuss what is missing and if other specific
distributions would be useful.

People are encouraged to think creatively about what can be measured in order
to reduce the PDF uncertainties.

- ratios to cancel systemic errors and theoretical errors

We would like to construct simulated datasets that fold in detector
acceptance, binning and have realistic statistical errors for these
measurements. We talked about presenting errors in such a way that the PDF
fits can use them. Going through the process of constructing these datasets
would help in establishing a format that is useful to use as input to the
fits.

These simulated datasets would allow us to do "what if" studies.
Some questions that these "what if" studies could help answer.

- allow for intrinsic heavy flavor
  - what is allowed by current data and what is allowed by newer data
  - what impact does this have on future important processes
    - single top
    - Higgs
  - with new Tevatron data can we better constrain heavy flavor
  - are there particular measurements
- identify measurements/distributions that can be used as input
- identify measurements/distributions that can be used as consistency checks
- relate measurements to what is being constrained in the PDF fit
- explore the possibility of extending measurements and quantify the
  impact of doing so
  - higher/lower Et
  - forward eta
- study the impact of specific systematic errors to see if we can
  identify those that led to greater uncertainty
- quantify the impact of measurements for different integrated luminocities
  - how much data is needed before the measurement is interesting

Markus brought up the issue of speeding up the calculation for cross section
calculations. More details were provided in a separate email to this list.

We would like to have a followup meeting in two weeks and will try to engage
members from the other working groups.