Minutes of "Physics Comparison and Generator Tunes" meeting 18. Oct 2013

	•	Intro:
	◦	2010 reprocessing
	◦	we should keep these data for tuning
	•	P. Skands
	◦	discussion whether results corrected to parton level make sense: -> should avoid parton level, since it is not well defined, at least provide results on observable level also
	◦	do not provide only central tunes
	◦	issue on systematic treatment of uncertainties, how can they be estimated 
	◦	alpha_s -> large values for LO is preferred (alpha_s ~ 0.14), but this is only good for specific processes, since it includes higher orders, but if transported to another process higher orders might be different...
	◦	dn/deta is not enough, need also RMS or multiplicity distribution
	◦	request to us in CMS:
	▪	tell which Rivet routines use old NSD definition
	•	
	•	Samantha:  energy dependence of tune
	◦	first steps to tune energy dependence presented
	▪	if x-section is needed for distributions, then special care has to be taken to properly propagate the x-section to the different energy histos
	◦	at low energie, problem with statistics
	▪	perhaps exclude bins at large pt (in professor )
	▪	use Rick's method to merge Min Bias and hard QCD samples
	◦	validate tunes with different observables
	◦	why is tune with so different parameters still giving similar results as Z2*lep ?
	▪	are parameters not really relevant for the distributions ?