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Re: [E-rhic-ir-l] action items from todays meeting

From: Aschenauer Elke-Caroline <elke AT bnl.gov>
To: Bazilevsky Alexander <shura AT bnl.gov>
Cc: E-rhic-ir-l AT lists.bnl.gov
Subject: Re: [E-rhic-ir-l] action items from todays meeting
Date: Sat, 18 Mar 2017 18:38:10 -0400

On Mar 18, 2017, at 18:11, Alexander Bazilevsky <shura AT bnl.gov> wrote:

Sasha,

there are several physics processes which need neutrons

- veto nuclear breakup --> this needs a suppression of 10^5 and more in eA --> so a very high neutron detection efficency more then we have right now.

- we need to do geometry detection of the collision --->

- we want to do exclusive PS and VM reactions like DVCs, where you don't detect the scattered neutron instead of the proton,

and reconstruct t from the neutron --> the t-spectrum needs good resolution

- for light nuclei we want to reconstruct the nucleus detecting the breakup protons and neutrons to understand nucleon-nucleon forces

- the long list of things the JLab people always talk about

there has been a EIC R&D proposal on this https://wiki.bnl.gov/conferences/images/9/97/ZDC-2014-EIC-RD_2.pdf, which wanted to go for 30%/sqrt(E)

I'm not requesting we have 0.6 m, but EIC is a high precision machine and to design everything from the beginning to the limit is not a good strategy.

Because in 10 y from now there might be more and different hot physics topics which need neutron detection.

Unfortunately for many things we have not yet a definite hardware design for the detector, like the zdc, if we could say 40 cm is okay.

I think one thing is clear the rhic ZDCs are not good enough for the EIC physics.

So I think 40 cm is the absolute minimum, 60 cm would be excellent

I hope my answer helps, more details can only be obtained from simulations of different hardware solutions and physics processes.

Cheers elke

Dear Elke,

This is ZDC for fixed target WA80, where people usually don't have such strict space restrictions as at a collider, so they can afford such a good (and large) calorimeter. E.g at LHC the ZDC size is similar to RHIC's one ~10cm.

What are physics driven requirements for ZDC at eRHIC? The energy resolution of RHIC's ZDC is 65%/sqrt(E)+15%. Is it too bad? I guess the large const term comes from energy leakage in transverse and long. directions. Another important characteristics is the EMCal nonuniformity across the acceptance (over transverse plane), so here we would like to be reasonably far away from the edge. For RHIC's ZDC design (assuming its infinite lateral size) the lateral energy leakage is <5% if we're >5cm away from the edge, while the resolution stays almost const. Isn't it enough for eRHIC physics?

So, accounting the +/-4 mrad neutron cone (which is +/-12 cm at 30m) and reserving 5cm from the edge, I'd derive the ZDC size +/-17cm (or 34 cm) - I see Bob uses something like 30cm in his slides. With such a transverse dimensions and if we make it even longer than RHIC's ZDC, we could somewhat reduce the constant term, if it is crucial.

... my naive thinking.

Regards,

Sasha.

On 3/18/17 12:45 PM, Aschenauer Elke-Caroline wrote:

On Mar 17, 2017, at 17:54, Aschenauer Elke-Caroline <elke AT bnl.gov> wrote:

Hi Hi,

some info on point 2 the size of a zdc

cheers elke

Dear All,

so here just a quick summary of the info we need to get to Bob for his talk.

1. what is the crossing angle we need to have for the high bunch option to avoid parasitic collisions

2. what is the size of a ZDC for EIC

if you look to Nuclear Instruments and Methods in Physics Research A279 (1989) 503-517 a high resolution ZDC would be roughly 0.6 m x 0.6 m x 2.5 m

Of course the width depends also on the z position of the ZDC. The =/-4 mrad neutron cone has at 30 m a transverse size of +/- 12cm

3. what is the size of the lumi-monitor system

4. what is the size for the RP system

---> we should try to have only vertical plots which circumference the beam, the length in z is roughly 5 - 6m

Did I forget something.

cheers elke

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| `, Elke-Caroline Aschenauer =

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( `,_' )+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=

) `\ -

/ '. | +

| `, Elke-Caroline Aschenauer =

\,_ `-/ -

,&&&&&V Brookhaven National Lab +

,&&&&&&&&: Physics Dept., 25 Corona Road =

,&&&&&&&&&&; Bldg. 510 /2-195 Rocky Point, NY, -

| |&&&&&&&;\ 20 Pennsylvania Avenue 11778 +

| | :_) _ Upton, NY 11973 =

| | ;--' | Tel.: 001-631-344-4769 Tel.: 001-631-569-4290 -

'--' `-.--. | Cell: 001-757-256-5224 +

\_ | |---' =

`-._\__/ Mail: elke AT bnl.gov elke.caroline AT me.com -

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Alexander Bazilevsky
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