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[Alexander Bazilevsky <shura AT bnl.gov>]

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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Alexander Bazilevsky
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