Proposed charge of activities for the Workshop on "The LHC early phase for the ILC" to start at Fermilab on April 12-14, 2007.

The LHC will produce its first physics data in 2008 and has the promise of making groundbreaking discoveries with the first few femtobarns of data. This will certainly have profound implications for the proposed ILC program. We propose to examine the scenarios that may occur in the early phase of the LHC operation and investigate their impact  for ILC physics.

There exists a world-wide consensus that a linear collider of up to at least 500 GeV, upgradeable to about a TeV, should be the next major project  at the high energy frontier. This consensus as well as the need for a timely realization of this machine has been clearly expressed in statements by ECFA, ACFA, HEPAP, ICFA, and other organizations, and has most recently been confirmed by the EPP2010 report.

The design of the International Linear Collider (ILC) is being addressed by a world-wide collaboration of physicists in the context of the Global Design Effort. The Mission of the Global Design Effort is to produce the design for the ILC in three stages, namely a Baseline Configuration (was completed by the end of 2005), a Reference Design (scheduled for the end of 2006) and a Technical Design (scheduled for 2009). The decision about the start of construction of the ILC will therefore be taken at a time when early data from the LHC are expected to be available.

It is therefore of interest to assess the impact of results from early data at the LHC on plans for the ILC. A scientifically well-founded investigation of this issue requires expertise on the experimental aspects at both the LHC and the ILC and on the possible theoretical interpretations of signals of new physics.

The charge of the working groups focussing on LHC / ILC interplay at the Fermilab 07 workshop is to investigate various possible scenarios of early LHC data. For the purpose of this workshop `early LHC data' should be understood as an integrated luminosity of about 10 fb^-1.
 
In particular, the following questions should be addressed:

1. What could be the impact of early LHC results on the choice of the
   ultimate ILC energy range and the ILC upgrade path? Could there be issues
   that would need to be implemented into the ILC machine and detectors
   design from the start?
   
   
2. Could there be cases that would change the consensus about the
   physics case for an ILC with an energy of about 500 GeV?
   
   
3. What are the prospects for LHC/ILC interplay based on early LHC data?
   
   

These questions should be investigated within the following classes of possible scenarios of results observed in the initial LHC runs:  

1. the detection of only one state with properties that are compatible with those of a Higgs boson;
   
   
2. no experimental evidence for a Higgs boson at the early stage of LHC;
   
   
3. the detection of new states of physics beyond the Standard Model.
   
   

In analyzing these scenarios, the working groups should clearly distinguish between assumed experimental signatures and their possible interpretations within certain models. Possible theoretical uncertainties should be carefully investigated.

The working groups will be formed according to the three scenarios:

i), ii), iii), with further subdivisions of iii) as listed below:

iii a. Missing Energy (+nothing, leptons, jets) signals

iii b. Leptonic resonances

iii c. Multi-Gauge-Boson signals

iii d. everything else.
 
The convenors will include one LHC experimentalist, one ILC experimentalist and one or two theorists for each group. Each group should identify the most promising physics channels for the class of events they are studying and have both detector as well as beam diagnostic experts as part of their working group.

The precision with which event and machine parameters can be measured needs to be convoluted with the anticipated signals to obtain meaningful ILC-LHC case studies in a uniform framework. The physics studies should identify the detector and machine specifications one needs to reach the physics goals. Where possible, the sensitivity of each process to critical detector and machine parameters ought to be studied.