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)
>
> ########################################################################
> Use REPLY-ALL to reply to list
>
> To unsubscribe from the SNOWMASS-ELECTROWEAK list, click the following link:
> https://listserv.slac.stanford.edu/cgi-bin/wa?SUBED1=SNOWMASS-ELECTROWEAK&A=1
>
########################################################################
Use REPLY-ALL to reply to list
To unsubscribe from the SNOWMASS-ELECTROWEAK list, click the following link:
https://listserv.slac.stanford.edu/cgi-bin/wa?SUBED1=SNOWMASS-ELECTROWEAK&A=1
|