sPHENIX cold QCD topical group

["Aidala, Christine" <caidala AT bnl.gov>]

Minutes:

 

John Lajoie – Update on LOI simulations for Drell-Yan and Jets

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p. 4 – Left plot is old simulation, right plot is with updates/fixes.  High-mass background reduced by factor of ~2 with chi^2 cut.  Note that new simulations now include more realistic event vertex distribution.  Will consider updating plots with more realistic mass binning based on our momentum resolution.  Same integrated lumi for both signal and bg.

 

Still working on understanding D-Y background from secondaries and how this would be affected by event selection trigger.  Currently only events with a forward e+ or e- with pT > 0.5 GeV/c.  Will need to address one way or another in LOI.

 

Jets – Has now looked at calorimeter jets and track jets, PYTHIA6 and PYTHIA8.  Fixing memory leaks was especially important for jet simulations.   

 

p. 11 – 48-constituent cut on calorimeter jets—cut on number of towers.  ~3x3 = 9 towers per cluster, with clusters possible in both EMCal and HCal.

 

p. 14 – Still digesting apparent difference in eta distribution of calorimeter and track jets.  Perhaps due to edge effects of calorimeter jets—clusters can be partially within acceptance, whereas tracks are either in or out.  Possibly also leakage out the back of the calorimeter, or tracks with misreconstructed momentum?  Suggestion that maybe due to energy loss in plug.

 

Suggestion to look at jets of indeterminate origin in more detail—some from final-state radiation?  Correct to treat simply as dilution to asymmetries when comparing to calculations?  Should look into simulations in more detail, also check with theorist.

 

Thanks to John for all his work developing the simulations!

 

 

Paul Stankus + Takao Sakaguchi – fsPHENIX Heavy Ion Observables: 3-D Event Shapes

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Two proposed thrusts:

-Characterizing medium at non-central rapidity, in particular possible variation of QGP with baryon density. 

- Long-rapidity correlations are imprinted at early times, as long as any subsequent evolution is local (e.g. hydro)—access information on pre-QGP.  Look at full 3-D event shapes via forward-mid correlations. 

 

Unique to fsPHENIX (not ATLAS, CMS, ALICE, or STAR)—uniform, low-threshold calorimetry to eta ~4.  At ATLAS and CMS, calorimeter thresholds high; ALICE only has calorimetry at midrapidity. 

 

Observable:  d^2E_T/d\phi d\eta event-by-event to characterize final-state energy density in MB events.  Take 2-D Fourier transform of event and square.  Then average over events to get power spectrum.  Analogous to CMB power spectrum in cosmology, specifically the low-l (< 100) long-range correlations, imprinted from inflationary times because they’re too long-range to be causally connected via later-time evolution.

 

Doesn’t think correlations with Delta eta > ~4 would gain much, so only having one forward arm not a problem.  Gaps in coverage not a problem, either (think of how galactic plane excluded from CMB measurements).  Nor are statistical fluctuations in the response of the calorimeter.  Fourier transform handles nicely.

 

p. 5 – Delta eta in 2-D Fourier transform – can take as accessible window in eta (-1 to 4, i.e. 5 units of pseudorapidity) or as including unseen part all the way to beam rapidity of +-5.5, i.e. 11 units of pseudorapidity.  Get basically same information content.

 

p. 7 – Low k corresponds to long-range in eta.  Flat across k implies short-range correlations at all scales, perhaps due to statistical fluctuations in fragmentation—need to look into in more detail. 

 

Doesn’t require long running time!  Could already learn from minutes-to-hours of running! 

 

Suggestion to try to make plots more similar to CMB plots.  More directly comparable to a single heavy ion event—only one universe!  We instead can look at the correlations in many events.  Also thinks that keeping 2-D plots/information for heavy ion collisions important.  But could try to find more analogous quantities/plots--look at some kind of fluctuations around averages?

 

 

Nils + Christine – Update on LOI

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We’re behind on original goal of having a draft to discuss by today.  Maybe ~half of material currently in place in Overleaf.  Individuals who have agreed to write sections are encouraged to get the basic content, in particular figures, in by the end of this week, so content can be discussed at sPHENIX General Meeting on Friday.  Workfest to finalize LOI before release to the collaboration will take place at Stony Brook next Tuesday – Thursday.

 

 

From: sPHENIX-cold-QCD-l [mailto:sphenix-cold-qcd-l-bounces AT lists.bnl.gov] On Behalf Of Nils Feege
Sent: Thursday, May 4, 2017 10:35 AM
To: sphenix-cold-qcd-l AT lists.bnl.gov
Subject: [Sphenix-cold-qcd-l] Next sPHENIX Cold QCD Meeting Monday 5/8 Evening at 8:30pm EDT

 

Dear Cold QCD enthusiasts,

 

our next meeting will be

 

Monday, May 8, 8:30pm EDT (evening!).

 

The BlueJeans link is https://bluejeans.com/345777492 (no in-person meeting at BNL this time). The agenda is evolving at https://indico.bnl.gov/conferenceDisplay.py?confId=3126. Please let us know if you would like to present an update on your LOI-related study.

 

In this meeting, we need to finalize the content for the Forward instrumentation LOI and identify what's still missing, so that we can present it to the collaboration next week Friday (finalizing the text will happen later). Please have a look at the current draft on Overleaf before the meeting:

 

https://www.overleaf.com/9084879zgwhpckqrbmf

 

If you agreed to prepare one or more of the sections, please have at least a preliminary version of the figures and some rough text content in those sections.

 

We look forward to hearing you at the meeting.

 

Best,

Christine Aidala & Nils Feege

Co-conveners sPHENIX Cold QCD Topical Group

 

 

--

Dr. Nils Feege

Research Assistant Professor

 

SUNY at Stony Brook

Department of Physics & Astronomy

Stony Brook, NY 11794-3800

 

e-mail nils.feege AT stonybrook.edu

skype nils1920

phone +1-631-632-8710

 

www.linkedin.com/in/nilsfeege