E-rhic-ir-l mailing list

["Ptitsyn, Vadim" <vadimp AT bnl.gov>]

Dear Elke,

thank you for the comprehensive answer.

So, I understand that we could proceed first with creating a set of parameters for e-Au which maximizes the luminosity (and using the present IR magnet design configuration which satisfies the neutron acceptance).

Of course, it could be adjusted in the future if satisfying some specific acceptance requirements would be needed.

With best regards,
Dr. Vadim Ptitsyn
Brookhaven National Laboratory
Collider-Accelerator Department

On Feb 26, 2017, at 2:10 PM, Aschenauer Elke-Caroline <elke AT bnl.gov> wrote:

On Feb 23, 2017, at 9:15, Ptitsyn, Vadim <vadimp AT bnl.gov> wrote:

Dear Vadim,

let me go through things in order.

Both for He-3 and Deuterium forward tagging of the proton and neutron is critical. running polarized He-3 with out this would be pretty useless.

So Rich checked the tagged photon acceptance for He-3 just lately for the LR IR design and it was very good, for the RR-IR he will do of course as he now has the latest IR design from Bpb.

Now there comes your question about the proton acceptance of the eA collisions.

As we discussed in the past the most important to veto or tag on the Au break up is the forward going neutrons and all the IR designs we have been looking at take the neutron acceptance into account.

Now for the protons from a Au breakup. 

First of all a Au nucleus breaks up in many things protons, neutrons, alpha's and heavier fragments particles, Jlab says the can reconstruct all of fragments of the breakup, there is currently no EIC physics which requires this, So I don't think we can make this right now an requirement. I just discussed this week with Charles Hyde about it and he admitted that it is a nice to have, but they have not done detailed simulations to show they could really reconstruct the Au-nucleus from the different fragments.

There is one paper by Raju et al. https://arxiv.org/pdf/1411.0887.pdf which points out some advantage if you also detect the protons in addition to the neutrons for tagging centrality. The requirements are very loosely defined. I have contacted the authors to get some more details. I will update you what I learn. As they don't want to do imaging with these protons, such coverage in pt should be less critical.

Of course we can run also protons from Au decays through the IR.

I hope this answers your questions at least to some extend.

cheers elke

reference to raju's paper

Ballistic protons in incoherent exclusive vector meson production as a measure of rare parton fluctuations at an Electron-Ion Collider 
T. Lappi (Jyvaskyla U. & Helsinki Inst. of Phys.), H. Mäntysaari (Jyvaskyla U.), R. Venugopalan (Brookhaven). Nov 4, 2014. 5 pp. 
Published in Phys.Rev.Lett. 114 (2015) no.8, 082301 

Dear Elke,

as we proceed to defining beam parameters/luminosities for e-Au collisions, could you clarify once more, please, whether one should care at all in this case about satisfying forward acceptance ( 0.2<pt<1.3 GeV) and related hadron beam angular spread limitation.
Or it can be ignored, thus maximizing luminosity as much as possible.


For e-He3 collisions you mentioned before that forward proton (spectator proton) detection is needed.


With best regards,
Dr. Vadim Ptitsyn
Brookhaven National Laboratory
Collider-Accelerator Department

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