Dear friends,

At the end of the last CMS week, Darin and Paris asked me to coordinate the Energy-Flow effort in CMS, and I immediately accepted, with pleasure. This was therefore announced in the Plenary CPT meeting on Thurday afternoon in Darin's presentation.

I intend to coordinate this effort along the lines presented in the talk I gave two months ago during Darin's kick-off meeting .

Of course, should new (good) ideas pop up in the process, these guidelines would immediately be upgraded accordingly.

To start with, and unusually enough, I would like to call for some basic preparatory work, instead of a meeting that we anyway already had in July. Indeed, many basic tools either are missing, or have not been advertized enough (so that I do not know about them), or have not been optimized towards the determination of the energy and particle flow in jets, but instead towards energetic, isolated particles. I would therefore like to see the situation improve and tools be developed in the following aspects.

For some of these aspects, I already got people starting the work, and other who manifested some interests. In this case, the names are indicated. By no means should these names discourage you to work on these items as well. It just means that some collaborative work should go on for the benefit of the Collaboration.

Here is a (probably non-exhaustive, but already long) list of the various items that I would like to be tackled. This list certainly requires a lot of cross-coordination between the detector PRS groups, which I am going to work out. Help from the PRS group coordinators is more than welcome. Please pick up your favourite topic.

1) Photon identification & energy measurement in jets

People working: Colin Bernet (CERN-CMA PRS e/gamma), PJ

* clustering in ECAL: - are our current clustering algorithms optimal for non-isolated (and even isolated) low-energy photons? - what is the identification efficiency and the energy/angular resolution of these algorithms? - How could one improve on these two aspects (the former is more important than the latter for energy flow, amazingly enough) - What threshold(s) for cells, seeds, etc... - Optimization as a function of energy / rapidity

* Track extrapolation - What "isolation" criterion for identifying photons in jets? (distance wrt the closest extrapolated track seems natural) - Optimization as a function of energy / rapidity

* Preshower - Is the preshower of some add'l use for increasing the photon ID efficiency? - Clustering in the preshower?

* Photons in ECAL cracks? In the Endcap/Barrel overlap?

2) Electron identification & energy measurement in jets

People working: PJ + ?

* Clustering in ECAL + preshower + cracks + overlap - see above

* Tracking and super-clustering - are our current algorithms optimal for non-isolated low-pT electrons? - How could one improve on the identification efficiency? On the energy resolution? - Optimization

* Preshower - Does it help the pion rejection (important!)? - Does it help the id efficiency? - How should we do for the barrel (no preshower... apart from the tracker)?

3) Muon identification

People Working: ? (Probably plenty, but the Muon PRS group conveners know more than me)

* Are our current GlobalMuon algorithm good at identifying muons in jets (non-isolated, small pT)

* How to improve on this algorithm (efficiency/purity-wise)?

* Determine the energy expected in ECAL/HCAL as a function of pT and eta

4) Neutral (and Charged) Hadron identification in ECAL+HCAL

People working: (for the clustering in ECAL/HCAL): C. Bernet, PJ (CERN) C. Foudas, F. Brekman, D. Colling, S. Greder (Imperial College) (for the energy calibration): D. Konstantinov, S. Abdullin

* Clustering in HCAL - To be done from scratch - possibly following the ECAL strategy, or do we need something different. - What threshold(s) for cells, seeds, etc... - Isolation criterion wrt to track extrapolation (as a function of E and eta) - ECAL / HCAL link

* Clustering in ECAL - reclustering in ECAL after photon Id. With different thresholds?

* Energy corrections - e/pi factor in ECAL = f(E_hcal, E_ecal, eta) : Table done for FAMOS,

by Salavat and Dmitri, based on OSCAR+ORCA simulation. Is it good enough? How should we include test beam results? - calibration in HCAL = f(E)

5) Electrons/Hadrons/Muons in VFCAL

People working: ?

* Is clustering useful there?

* What energy corrections?

6) Tracking

People working: (Probably plenty, but the Tracker b/tau group conveners know more than me)

* Extend the combinatorial track finder to - low pT tracks - tracks with less than two pixel hits - tracks not originating from the beam (V0's, nuclear interaction)

* Study the possibility of making the track finding in several steps, for speed, and probably, efficiency, consideration (i.e., apply first a normal combinatorial track finder, remove the hits used, search for low pT tracks within the remaining hits, remove the hits used, etc...)

* Identify tracks originating from pileup collisions

* Track extrapolation to/through calorimeters (also treated in 1, 2, 3, and 4, but it's good to have different views)

And then (when the rest is done):

7) Mixed clusters in calorimeters (charged + neutrals)

People working: Colin Bernet, PJ (CERN)

* Tracker/Preshower/ECAL/HCAL/Muon link

* Mixed photons in charged clusters - re-clustering?

* Mixed neutral hadrons in charged clusters - re-clustering

8) Evaluation of the performance

Here, we need to have some common tools to evaluate the performance of such and such algorithm. I'll get in touch with Arno Heister for this part, to start with. Note that it is possible to make all the developments within FAMOS, but the final evaluation can only be done with the full ORCA (and later with CMSSW).

We certainly also need to compare with (and continue to develop?) already existing methods, such as the JetPlusTracks algorithm. I'll get in touch with Sasha et al. to know what their plans are in this respect.

There we go. I'll schedule meetings only when there is sufficient work to be presented, instead of just listening to people about what they intend to do in the future. (Mail is good enough for that.) I also intend to develop a web page where the developed tools (and the related code) will be available and documented.

Please let me know of your plans, comment, suggestions, etc...



-- MariaSpiropulu - 11 Oct 2005

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