[Halld-physics] Physics Working Group Meeting: Tuesday, October 16 @ 11:15 am

Tue Oct 23 07:54:36 EDT 2018

Hi Igor, All,

Yes, as we discussed at the Physics WG meeting last week, there are 2 possibilities for low energy measurements which correspond to your bullets below.  The priority was given to proposing a run plan for this Fall, since time is limited.  Thanks to Sean for collecting the relevant data and rate estimates for this Fall’s proposal at https://halldweb.jlab.org/wiki-private/index.php/2018_Low_energy_measurements <https://halldweb.jlab.org/wiki-private/index.php/2018_Low_energy_measurements>.  The short summary is that we would like to propose a ~5 day run with a lower PS field setting to give statistical errors <10% on cross sections for comparison to previous measurements, and this is on the agenda for today’s bi-weekly meeting.

This Fall’s proposal of course does not preclude running in Summer 2019, but would give us some data in the short term to compare with previously measured cross sections.  To make a decision on Summer 2019 running, we would need a similar proposal with the stated goals, rate estimates, and required running time.

-Justin

> On Oct 17, 2018, at 4:34 PM, Igor Strakovsky <igor at gwu.edu> wrote:
> 
> Hi Justin,
> 
> According to my understanding there are two different run periods
> 
> - this fall which will allow to cover 4-9 GeV or so.  CLAS6 does not have pol measurements
> 
> - next summer which is a low energy run which you spelled out. that is different story
> 
> Cheers, igor
> 
> 
> On Wed, Oct 17, 2018 at 1:15 PM Justin Stevens <jrsteven at jlab.org <mailto:jrsteven at jlab.org>> wrote:
> Hi Igor,
> 
> Thanks for your feedback.  My understanding is the accelerator would run at half energy (Ee ~ 5.5 GeV), and as usual we could choose to set the coherent peak as we prefer.  The hodoscope in this case would cover Eg ~ 1.5 GeV to the endpoint, although it will still be only half instrumented (sampling) between 1.5 and 3.5 GeV.  So data below Eg = 4 GeV could be possible in this scenario, but at a lower efficiency.
> 
> -Justin
> 
>> On Oct 15, 2018, at 3:11 PM, Igor Strakovsky <igor at gwu.edu <mailto:igor at gwu.edu>> wrote:
>> 
>> Hi Justin,
>> 
>> It would be good to spell out a possible Eg range and our goals for summer of 2019.  Then all depends.  
>> 
>> I reported twice that if our range is limited by 4 - 6 GeV and our main goal is diff cross sections then 
>> g12 from CLAS6 will work for us.  There are no CLAS pol measurements in this case.  So, we have 
>> gp-->pi0p cross sections published several month ago and Volker's analyses for gp-->etap and 
>> gp-->omegap are under the HW group review now.
>> 
>> If one can possible to go below 3 GeV then we will have more options including polarized 
>> measurements. Additional benefit will come from the ability to use the PWA technology to evaluate
>> new data and possibility to provide "good" event generators for MC.  See my slides at DB
>> 
>> Cheers, igor
>> 
>> 
>> 
>> -----
>> Igor Strakovsky, SAID INS The George Washington University
>> Tel: 571-553-8344(VC),202-994-4742(FB),Skype: igors1945_2, 
>> Cell: 703-728-5627,Emails: igor at gwu.edu <mailto:igor at gwu.edu>, igor at jlab.org <mailto:igor at jlab.org>
>> 
>> On Mon, Oct 15, 2018 at 12:50 PM Justin Stevens <jrsteven at jlab.org <mailto:jrsteven at jlab.org>> wrote:
>> Hi All,
>> 
>> There’s been a proposal to have a short discussion about a potential low-energy run in Summer 2019 during tomorrow’s physics meeting.  To frame the discussion: the accelerator plans to run at ~half energy during June/July 2018 and GlueX could potentially run parasitically during this period.  
>> 
>> We had some discussion about the potential usefulness of low-energy running earlier this year (comparison to cross section measurements from CLAS, energy-dependence of polarization observables, etc.), but that was in a different context of using the full energy electron beam with lower coherent peak settings (see https://halldweb.jlab.org/wiki-private/index.php/Aug_7,_2018,_Physics_Working_Group <https://halldweb.jlab.org/wiki-private/index.php/Aug_7,_2018,_Physics_Working_Group>).
>> 
>> If you have something you would like to contribute to the discussion, please let me know.
>> 
>> -Justin
>> 
>>> On Oct 14, 2018, at 1:46 PM, Justin Stevens <jrsteven at jlab.org <mailto:jrsteven at jlab.org>> wrote:
>>> 
>>> Hi All,
>>> 
>>> Our next Physics WG meeting we be Tuesday, October 16 at 11:15 am, https://halldweb.jlab.org/wiki-private/index.php/Oct_16,_2018,_Physics_Working_Group <https://halldweb.jlab.org/wiki-private/index.php/Oct_16,_2018,_Physics_Working_Group>.  Please let me know if you have something you would like to present.
>>> 
>>> -Justin
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