sPHENIX cold QCD topical group

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

Minutes:

 

Christine and Nils – News and Updates

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

Dedicated Wiki page now created for LOI, which collects reference information such as the energy configurations, polarizations, etc. as well as the detector scenarios to use for LOI studies:  https://wiki.bnl.gov/sPHENIX/index.php/EIC_SPHENIX_LOI_2018#2018_Letter_of_Intent_for_EIC-sPHENIX

 

There will be an extra, off-week meeting next Monday, May 21, at the usual time of 8:30 EDT. 

 

There will be a workfest at BNL June 3-4.  See previous e-mail announcement.  Note that this is NOT to work on simulations for the PAC meeting!  What might remain for the PAC meeting would be improving plotsmanship and finalizing the presentation slides.  Focus of workfest will be on studies beyond the PAC meeting that we hope to include in the LOI, and working on the LOI document itself.  Timing is not ideal, but we were not able to identify a better time later in the summer.

 

 

Nils – EIC-sPHENIX Envelopes and Acceptances

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

Latest CAD drawing of detector envelopes discussed.  5 different scenarios to be considered for LOI, mainly driven by whether the Central EMCal can be extended in either or both directions to avoid gaps in EMCal coverage.  Note that Scenario 5 sacrifices the electron-going RICH in order to move the Electron EMCal in and recover some of the pseudorapidity gap if the Central EMCal can’t be extended in the electron-going direction, but the acceptance recovered is almost definitely not worth the loss of the RICH.

Scenario 1: Ideal case (combines Scenario 2 & Scenario 3).
Scenario 2: Only extend CEMC in e-going direction.
Scenario 3: Only cut CEMC and inner HCAL corners + extend CEMC active area in h-going direction + extend RICH coverage in h-going direction.
Scenario 4: No changes to sPHENIX calorimeter.
Scenario 5: No changes to sPHENIX calorimeter, no ERICH.

 

It was noted that gaps in acceptance affect not only x-Q^2 coverage, but also hermeticity for kinematic reconstruction via the hadronic/jet activity, which in contrast to x-Q^2 coverage can’t be recovered by running at different energies.

 

 

Xu Sun – Likelihood method for mRICH PID

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

A lot of the code already merged with main sPHENIX GEANT simulation branch, additional code already pushed and under review to be merged.

 

May need 23 cm for forward mRICH, rather than 20 cm currently allocated, but shorter focal length also possible, at some cost to PID performance.  If extend detector layout farther out to fit 23 cm, lose some pseudorapidity coverage.  In the short-term for PAC meeting, will estimate the reduction in performance for 20 rather than 23 cm.

 

Extending established maximum likelihood method for RICH PID detectors to wider phase space.  Pion/kaon separation up to 10 GeV/c with perfect detector and 1x1 mm^2 pixel size.  Next steps are to simulate full phase space and add more realistic detector effects.  For parameterization, will need to decide binning for vertex x position, vertex y position, p, theta, and phi based on expected tracking performance.  These will be the variables of the parameterization look-up table.

 

Electron-going mRICH will also be added into sPHENIX GEANT, and electron-pion separation will be studied.  Currently 14 cm available according to configuration to be used for LOI studies.

 

 

Richard Milner – Spin-Dependent Inclusive DIS from Polarized Light Ions at EIC/eRHIC

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

Polarized 3He.  Also polarized light nuclei with J>=1.  Polarized 3He source R&D ongoing by MIT; first beam expected in RHIC in FY2020.  Max sqrt(s) for e+3He ~115 GeV rather than 140 GeV for e+p.  Max lumi ~2x lower.

 

g_1^n will be day-1 measurement at EIC—test Bjorken sum rule with unprecedented precision.  Note that technical development of Siberian snakes and 3He polarimeter in RHIC will also be needed.  Also presented ideas on using spectator tagging to make polarized p and d measurements using 3He beam.

 

“Nuclear gluonometry” – studying “exotic” gluons in a nucleus not associated with a single nucleon. Involves photon helicity flip of 2 units.  Inclusive DIS measurement, so straightforward to make once one has the appropriate beam.  Goes back to 1989 Jaffe + Manohar paper; several recent lattice papers, plus LOI for JLab experiment.  Lattice indicates a nonzero signal expected.  Need transversely aligned spin-1 nucleus (tensor polarized), unpolarized electron beam; lithium isotopes look promising, and polarized low-energy lithium beams have already been realized.  See talks at February workshop at Ghent on polarized light ions, https://www.jlab.org/indico/event/246/.  High-energy polarimetry will need to be developed for any of these polarized nuclei.

 

Richard will write up these ideas in a note, which will be posted on the Wiki page.

 

 

Enrique Gamez – DVCS Truth Studies for the EIC Detector

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

Previously a couple people expressed concern that the DVCS photon and electron clusters might sometimes be too close to distinguish, but simulation indicates that they’re always ~180 degrees apart in azimuth.  This would be expected from momentum conservation, and in the current simulations with no crossing angle, the deviations from 180 degrees apart are exactly balanced by the transverse momentum imparted to the scattered proton.  Note that with a nonzero crossing angle (22 mrad is the value in the draft eRHIC pre-CDR), there will be a small net nonzero transverse momentum in every collision.

 

p. 7 – Lower effective limit of eta = -3 for electron is due to Q^2 cut of 1 GeV^2 for 10 x 100 GeV^2 running.

 

Looked at loss in x-Q^2 coverage and number of events for the 5 detector acceptance scenarios described in Nils’s presentation.  For DVCS, given that the electron nearly always scatters within eta < 0 for 10 x 100 GeV^2 running, and the photon is most often produced at negative eta as well, the scenario with a gap in EMCal coverage at positive eta (the hadron-going direction) is not very damaging for DVCS.

 

As next steps, will make same plots of the different acceptance scenarios from the other official energy configurations after getting the MILOU files for these energies from Sal Fazio later this week, will run some statistics through the nominal GEANT configuration.  Will also look into detection of the scattered proton. 

 

Abhay will help get latest file from C-AD for magnet placement along the beamline out to z = 80 m, which will then be updated in Fun4All in order to consider scattered proton detection in more detail.

 

 

 

From: EIC-dsg-l <eic-dsg-l-bounces AT lists.bnl.gov> On Behalf Of Nils Feege
Sent: Friday, May 11, 2018 6:37 PM
To: sphenix-cold-qcd-l AT lists.bnl.gov; eic-dsg-l AT lists.bnl.gov
Subject: [EIC-dsg-l] Next EIC Detector Study Group / sPHENIX Cold QCD TG meeting on Monday, May 14th, evening at 8:30pm ET

 

Dear EIC and Cold QCD enthusiasts,

 

our next meeting is scheduled for

 

Monday, May 14th, 8:30pm ET.

 

The meeting is BlueJeans only (https://bluejeans.com/345777492) with the agenda evolving at https://indico.bnl.gov/event/4636/.

 

We look forward to hearing you at the meeting.

 

Best,

Christine Aidala & Nils Feege

 

--

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