sPHENIX discussion of software

["Huang, Jin" <jhuang AT bnl.gov>]

Hi, Kurt

Thanks for continuing the efforts on the particle flow algorithm. 

> Even at substantial energy, the purely electromagnetic showers from the 
> single electrons have a significant chance to produce a prob value of near 
> 0. Is this expected?

Interesting. Sasha may better comment on it. 

Meanwhile, there is a non-negligible chance for the electrons to produce a 
hard radiative photon in the tracking detectors prior to indenting the EMCal. 
Then it can be pulled away from the photon by the magnetic field and produce 
two cluster or a prolonged cluster, depending on how much is the magnetic 
pull. The latter case could make the electron shower non-standard and low 
prob. 


> ; I assume the default energy scale given to the EMC is calibrated to 
> electromagnetic showers.

Correct.
 

> If so, is the EMC hadronic energy scale known, or should I calculate it? 
> Any advice here would be appreciated.

User has to define and apply it. 

It depends on the shower development (MIP through or initiate a shower) and 
energy (lower and higher energy has different scale). In the leading order, 
one may choose a constant scale factor to convert the EM-shower energy scale 
to hadronic energy scale, and then deal with the dependencies in the next 
order corrections. 

Songkyo may talk about that tomorrow in the simulation meeting. 


> I plan to call into the simulations meeting tomorrow, so we could chat 
> about it then if there is time.

Sounds great. Would you like to be added to the agenda? 


Cheers

Jin


______________________________

Jin HUANG

Associate Physicist
Brookhaven National Laboratory
Physics Department, Bldg 510 C
Upton, NY 11973-5000

Office: 631-344-5898
Cell:   757-604-9946
______________________________

From: sPHENIX-software-l [mailto:sphenix-software-l-bounces AT lists.bnl.gov] On 
Behalf Of Kurt Keys Hill
Sent: Monday, November 6, 2017 7:28 PM
To: sphenix-software-l AT lists.bnl.gov
Subject: [Sphenix-software-l] Looking into PHENIX clustering in sPHENIX

Hi All,

The Colorado group is interested in particle flow jet reconstruction in 
sPHENIX. As a first step, we would like to separate electromagnetic from 
hadronic EMCal clusters within the jet and apply the appropriate energy scale 
to each type. We plan to eventually apply a track-cluster replacement scheme 
as a next step.

Moving toward EMCal cluster identification, I have merged Sasha's pull 
request into a local copy of g4cemc. I ran single pions and electrons through 
an otherwise default sPHENIX and plotted the chi2 and prob distributions in 
four different EMC cluster energy selections (see attached slides). In the 
lowest energy (0-1 GeV) the charged pion deposits MI energy which seem to 
look a lot like low energy EM showers. At higher energy, there seems to be 
fairly good separation between the EM and hadronic showers, and at the 
highest energies the pi0 curve separates from the electrons - presumably as 
the two photon showers merge.

Even at substantial energy, the purely electromagnetic showers from the 
single electrons have a significant chance to produce a prob value of near 0. 
Is this expected? 

As an aside, I would like to understand the current applied calorimeter 
calibrations better. I am using the calibrated calorimeter towers and 
clusters; I assume the default energy scale given to the EMC is calibrated to 
electromagnetic showers. If so, is the EMC hadronic energy scale known, or 
should I calculate it? Any advice here would be appreciated.

I plan to call into the simulations meeting tomorrow, so we could chat about 
it then if there is time.

Thanks,
Kurt