hi Ayres and Sven,
				    I hear you - but we are talking more than 20 years in the future. 

I am amazed at the progress in theory of higher order calculations over the past 20 years.  No way do I see this "precision theory frontier" slowing down over the next 20 years. 

I am at the Instrumentation Frontier Snowmass workshop in Boulder and they talk of "grand challenges".  To me, the discussion below also suggests a "grand challenge" in EWPO. 

regards,
Ashutosh


On Apr 18, 2013, at 10:26 AM, Ayres Freitas <[log in to unmask]> wrote:

> Hi Michael,
> 
> I second Sven's comments. I think going beyond GigaZ will be extremely challenging, both in terms the uncertainty of input parameters (mtop, alpha(mz), alpha_s), as well as higher-order calculations. Concerning the latter, we would need (at least) complete NNNLO, which is not completely inconceivable, but will require a hugh amount of effort, and I'm not sure if placing so much effort there is the best way to advance our field (and I am writing this as someone who at least partially makes a living from these calculations). See attachment for some more quantitative, but rough estimates of uncertainties from higher-order corrections that I made recently.
> 
> Best,
> Ayres
> 
> 
> On Thu, 18 Apr 2013, Sven Heinemeyer wrote:
> 
>> Hi Michael,
>> 
>>> The question for you is, how much would the extra factor of 10 at the Z pole (or the
>>> extra factor of 100 beyond Giga-Z) buy you in terms of the physics?  My quick impression
>>> is that it is not easy to convert the extra luminosity into physics.  GF and MZ must be
>>> improved, and NNLO electroweak becomes relevant.   The uncertainty in alpha(mZ) also
>>> needs improvement, and I do not see a way to do that.
>> When we make GigaZ predictions for sin2eff, MW etc. we already use
>> a very optimistic assumption on delta(Delta alpha_had) = 5 x 10^-5,
>> resulting in an uncertainty of 1.8 x 10^-5 in sin2eff, i.e. even
>> larger than the anticipated GigaZ uncertainty, see p. 7 of my talk
>> at the BNL meeting a few weeks back:
>> http://www.ifca.unican.es/users/heinemey/uni/talks/2013/SnowmassBNLEWPO.pdf
>> 
>> On the next page I give an estimate of intrinsic uncertainties, i.e. due
>> to missing higher-order corrections. Also here in the future the
>> GigaZ result can be matched only "so-so", and even less so in the MSSM,
>> which is the *only* model so far in which these quantities have been evaluated to a precision roughly as in the SM, it is much worse in any other model.
>> 
>> Of course in the future many things are possible. But our expectations
>> now (which are not wild guesses ;-) would not profit from another
>> factor of 10 improvement.
>> 
>> Cheers,
>>   Sven
>> 
>> 
>> *******************************************************************************
>> Sven Heinemeyer (IFCA (CSIC-UC), Santander, Spain)   > The future is not set!
>> phone: ++34/942/20-1536, fax: -0935                  > There is NO FATE but
>> email: Sven.Heinemeyer(at)cern.ch                    > what we make for
>> WWW  : sven-heinemeyer.de                            > ourselves!
>> skype: sven.heinemeyer                               >       (Kyle Reese, T2)
>> 
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