STAR Correlations and Fluctuations PWG

[Helen Caines <helen.caines AT yale.edu>]

Hi All,

  At this week’s LBNL BES workshop there was a brief discussion triggered by the difference in shapes of our reported HBT R_out^2 - R_side^2 vs sqrt(s) which might be related to an extended emission duration due passing through a first order phase transition, and the excess dilepton yield per pion which is also theoretically related to the lifetime of the source.

The HBT result shows a wide peak around 20 GeV while the dilepton results appear flat. See for example slides 18 and 20 of my presentation here: https://drupal.star.bnl.gov/STAR/files/STARPlansBES-II_0.pdf

I know that the two measurements measure different timescales so the absolute values don’t need to agree, but I thought both should be sensitive to potential extended freeze-outs generated via a first order phase transition. I was therefore wondering of this group if we see this HBT peaking in other species? Or rather, since the BES-II data are only just coming in, will we have the statistic to look at this and is someone currently planning to make the measurements?

Also, at the start of RHIC/STAR there were measurements of “total time of collision” being extracted from HBT+ spectra blast wave fits. I haven’t seen anyone attempting this in quite some time. Is it still considered a valid analysis technique? If so and we perform the study do we see a similar peaking? 

Thanks

Helen

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