sPHENIX discussion of physics

["Perepelitsa, Dennis" <dvp AT bnl.gov>]

Hi Jin and Anne,

Thanks for the followup discussion.

Jin - you raise a good point about the projected statistics. Actually, I was a bit surprised at how sharp the kinematic correlations between the photon and HF hadron were in their calculations. The processes that produce this final state are not like the generic photon+jet case, where things are back-to-back in the tree-level diagram. For example, if one has HF pair creation in the hard process, the photon has to be radiated in the parton shower, i.e. a fragmentation photon. Thus there is not as obvious of a “back to back” structure since the photon pT (& isolation?) requirement makes it a reasonably hard radiation. I think there are similar complications for the other HF creation processes, and so one would have to really study that, along with the statistics as you say.

Anne - I agree, that’s a great result from ATLAS and an excellent example of a “Day-1” sPHENIX physics measurement. Good motivation for folks in the Jet Structure TG to continue evaluating the reaction-plane-dependent underlying event subtraction!

Dennis 

On Nov 19, 2021, at 5:17 AM, Sickles, Anne M <sickles AT illinois.edu> wrote:

Hi all,

I just wanted to point out another paper which I think it is relevant to the jet drift paper below and sPHENIX jet physics in general.  

https://arxiv.org/abs/2111.06606 (ATLAS, main analyzer is Virginia Bailey) is a measurement of the jet vn in PbPb collisions which shows a non-zero v2 and v3 of calorimeter jets.  This kind of measurement is potentially a great early sPHENIX jet measurement because it doesn’t require a pp reference and it doesn’t have a large sensitivity to the jet energy scale.  Additionally the EPD will improve our ability to make these measurements in sPHENIX.  

Best,

Anne

---------------------------------------------------------

Anne Sickles

Associate Professor

University of Illinois at Urbana Champaign

sickles AT illinois.edu

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On Nov 11, 2021, at 8:18 PM, Perepelitsa, Dennis <dvp AT bnl.gov> wrote:

Dear sPHENIX colleagues,

If you have not yet done so, you may be very interested to take a look at an excellent recent review of jet physics by our collaborator Anne Sickles: https://urldefense.com/v3/__https://arxiv.org/abs/2110.14490__;!!DZ3fjg!tU_9tnsy9I2TSEduX5YKrp-VL6_As5gYCzBihmJJPiydC9AinhLu_MGcB9WlKOXwYw$  

This month, I wanted to highlight two recent theoretical papers which discuss sPHENIX-specific physics.

—

Jet Drift and Collective Flow in Heavy-Ion Collisions, arXiv link: https://urldefense.com/v3/__https://arxiv.org/abs/2110.03590__;!!DZ3fjg!tU_9tnsy9I2TSEduX5YKrp-VL6_As5gYCzBihmJJPiydC9AinhLu_MGcB9V2yOPdPg$  . The paper focuses on a possible (directional) modification to jet shapes from interactions of jet particles with a flowing medium [1]. The authors specifically mention sPHENIX as the place to make this measurement due to its access to low-pT photon+jets.

Probing the in-medium PT-broadening by gamma+HF angular de-correlations, arXiv link: https://urldefense.com/v3/__https://arxiv.org/abs/2107.12000__;!!DZ3fjg!tU_9tnsy9I2TSEduX5YKrp-VL6_As5gYCzBihmJJPiydC9AinhLu_MGcB9WsndsneQ$  . The paper proposes to study the in-medium diffusion of charm and bottom quarks through photon+HF correlations. The authors specifically note an advantage of RHIC kinematics that results in sharper initial kinematic correlations.

—

I was pleased to see that our colleagues in the theory community are thinking more concretely about sPHENIX-accessible physics. (I also found it interesting that both of these particular proposals rely on measuring high-pT photons - clearly this is a compelling capability for us!)

For me, a major question is how we can further encourage and direct this. In particular, I think it’s important that theorists are aware of our expected capabilities and statistical reach - so that predictions are really connected to reality.

Some ideas: Should the TGs occasionally invite theory speakers to their meetings (as was recently nicely done with the JETSCAPE speaker in the GM)? Should we organize, or ask our theory colleagues to organize, “last call for sPHENIX predictions” compilation papers (as was nicely done for p+Pb running at the LHC)? One could do this for HF predictions, jet structure predictions, etc.

Curious for your thoughts,

Dennis

[1] Some of you may remember similar ideas in older literature: https://urldefense.com/v3/__https://arxiv.org/abs/hep-ph/0405301__;!!DZ3fjg!tU_9tnsy9I2TSEduX5YKrp-VL6_As5gYCzBihmJJPiydC9AinhLu_MGcB9WkWy0d_Q$   

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Dennis V. Perepelitsa

Assistant Professor, Physics Department

University of Colorado Boulder