Epic-backward-hcal-l mailing list

[Leszek Kosarzewski <leszek.kosarzewski AT gmail.com>]

Dear Colleagues

We plan to have a meeting with Elke to discuss the follow up on the backward HCal discussions from the ePIC meeting. The meeting will take place at 1000h on Friday 2024.8.2, but please let me know if you are away or can't connect at that time. I also included Oleg, let me know if the time is ok for you.

Here are the slides:

https://indico.bnl.gov/event/20727/contributions/94427/

And the meeting link:

https://indico.bnl.gov/event/24337/

https://osu.zoom.us/j/99011057540?pwd=QmNhTDBrNmMyckdWYnJqcmFLMHl5QT09

The main comments were:

1. Slide 16:

Resolution for r>140 cm is not very precise ~50 cm due to scattering/showers in ~5 interaction lengths of the materials in front (support structures). People suggested not covering this area with nHCal. We need to improve this plot, because the dR_xy is measured between reconstructed cluster and straight lnie projection. This neglects scattering. We need to improve this plot. Most likely dR_xy shoudl be measured between reco and truth clusters. I would expect that the truth clusters are basically a proxy for where the scattered neutron ended up. The may be also an issue with clustering there, because we expect small energy deposits scattered over a large area.

2. Slides 17-19:

Pions leave more energy compared to neutrons and steal the reconstructed cluster. We need to improve the calculation of shared energy od the hit to include fractions from pion and neutron. Right now only the highest energy deposit points to pion for a reconstructed hit. This assumes all energy is due to pion, neglecting the neutron.

3. Slide 20:

The 20% improvement in resolution when vetoing jets with neutrals didn't seem  a good justification to people. Some even claimed that it can just be unfolded with MC. I don't think that's true, besides it would be model dependent. If we don't make the actual measurement, unfolding will just increase the uncertainties. I think they need to demonstrate that to prove their point.

4. Slide 25:

It looks like a lot of J/psi are produced in the backward direction. This is for exclusive diffractive production of J/psi in DIS regime with Sartre. We need to double check that.

Other points include:

5. Diffractive dijets for motivation - softer than standard jets, need to be investigated

6. Electron identification for motivation - use EMCal+HCal info for high momentum scattered electron identification. See Tyler's slides (probably slide 10-11 low-x and low Q^2): https://indico.bnl.gov/event/21766/#3-acceptance-and-resolution-st

7. Hadron beam background veto for dRICH similar to east and west EPD in STAR. See Oleg's slides: https://indico.bnl.gov/event/20727/contributions/94377/

Some people were a bit skeptical, but later I spoke to John and he said that the detector is included in ePIC, as there is a need for nHCal. We just need to finalize the motivation points to clearly demonstrate that and we are on the right track to do this.

Best regards, Leszek