sPHENIX discussion of physics

[Cameron Thomas Dean <cameron.dean AT cern.ch>]

Hi all,

Please find the minutes of todays meeting below.

Introduction - Conveners

 

                Jin - Cameron and I had a discussion with the Jet TG conveners about tools and person power. The jet group is focused on developing calo jets just now. For the collaboration to use HF jets, we need to develop Particle Flow so we are looking for volounteers to develop these tools for AuAu. We have some people actively looking just now but would like one or two more people to assist.

 

                Tony - David Stewart has been working on the truth tracing for our tracking. This is nearing completion and we should expect an email very soon when this has been launched so that people can test and provide him feedback

 

Jet tools - Megan Connors

 

                Ming - on Particle Flow - Given the EM cal segmentation, can we expect good matching between calorimeter information and tracks, e.g. at high energy, do we have lots of clusters merging together?

                                Dennis - Certainly the EMCal is finely segmented and we expect good separation of the clusters in AuAu. It should be noted that even in pp we have overlapping showers (which is true of other experiments). This is part of the algorithm's free parameters that require tuning.

 

 

                Jin - One aspect of the HF jets we want to look at is the purity of the jet at low pT. What are the Jet TG plans to study this? Is there anything we can coordinate between groups?

                                Megan - Virginia Bailey was looking at this a year ago and her slides are linked here but we do need more person power for this effort

                                Tim - Another avenue is to look at fake jet rejection schemes. There are methods at the LHC that we can try to import here. ALso, D0-tagging helps with our rejection

                                Jin - Yes, we can use secondary vertex tagging to help with this rejection

 

Internal Radiation - Hugo

 

                Zhaozhong - I ran a study on J/psi in EvtGen this morning but did not notice a lower mass tail in the invariant mass distribution. It may be that too few events were run. Maybe we need to specifically encode this and look into the decay table

                                Hugo - We must ensure that this is enabled as it is modelled using PHOTOS. We need to check how EvtGen is integrated in F4A and how we add in PHOTOS

 

                Hugo - What is our current Upsion generator?

                                Tony - I believe it is our internal generator, not Pythia. It's a vector meson generator

                                Hugo - I think we need to implement another generator with radiation effects and compare the two together.

 

                Jin - It would be useful to check if EvtGen is calling PHOTOS. If we gun a particle gun of J/psi decays, we can confirm this. Also, a pythia event is handelled differently. Prompt decays such as J/psi and Upsilons are passed to pythia while EvtGen runs during the Geant stage and is called on long-lived particles.

                                Hugo - In ALICE, we explicitily tell pythia not to decay these channels and force EvtGen to be the decayer

                                Jin - This is a good suggestion

 

                Cameron - This radiative effect must have it's main impact on the systemtics?

                                Hugo - Yes, this starts as a mismodelling of the signal (where it is underestimated) which leads to a poor handle on the backgorund modelling.

 

Commissioning analyses

 

                Xuan - We would like to extend our D0-jet study to AuAu simulations. We also found a bug in the code which has been fixed. This resulted in a change in the p and pT resolutions so we would like to present at the next TG meeting.

Cheers,
Cameron, Jin, Marzia and Tony