Dear Colleague,

we are pleased to invite you to the


Brookhaven National Laboratory, Upton, NY

May 9-10, 2002

The US Linear Collider Working Group is organizing a working group on theoretical issues (higher-order calculations) at a future Linear e+e- Collider (LC). To kick off the activities of the NorthAmerican working group on "Radiative Corrections (LoopVerein)" and to prepare for the International Linear Collider workshop in Korea (, the LoopFest aims to provide a forum to coordinate the NorthAmerican activities within the international LoopVerein. The LoopVerein is an international initiative convened to meet the theoretical challenges posed by the ultra-high experimental precision of a future LC. For more information about the LoopVerein please visit and

A future LC will measure the properties of Standard Model particles at an unprecedented level of precision. If there is physics beyond the SM emerging at the TeV scale, the Tevatron and the LHC will most likely provide hints while a LC will enable systematic studies to disentangle different new physics scenarios. There are many examples of scenarios where a particle escapes detection at the Tevatron/LHC, but could be discovered at a LC, e.g. a light Higgs-boson with non-standard decay modes.

For an overview of the physics potential of a future LC we refer to the TESLA TDR, the White paper, and the "Orange book" part 1, part 2, part 3, part 4.

To fully exploit the physics potential of a future LC, theoretical predictions need to be of highest standards, too. At the LoopFest we are planning to discuss what is needed on the theory side in order to meet this challenge. To only name a few topics, this discussion could include precision measurements of the properties of

After having identified the theoretical issues, we are planning to discuss how to proceed towards attacking these issues.

Your expertise is extremely important to meet the theoretical challenges posed by the expected experimental precision at a future LC. We hope you will be able to attend and are looking forward to your reply.

Please let us know asap if you are interested in participating by e-mailing to one of the organizers. Please also indicate in your e-mail if you would like to give a brief presentation. We also would like to hear about any suggestion you may have in order to make the LoopFest a success.

Inexpensive dormitory rooms are available at BNL and can be reserved by e-mailing Information on limo and train service to BNL, along with a list of off-site hotels can be found at We will charge a small fee of $50 to pay for snacks and dinner on Thursday evening (details about the method of payment will follow in a separate E-mail).

We are looking forward to seeing you at the LoopFest.

With best regards,

the organizers

Ulrich Baur,
Sally Dawson,
Doreen Wackeroth,

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