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

Tue Oct 23 09:22:17 EDT 2018

Hi Justin,

Plan looks great.  I have two small comments

- The min Eg is still unclear.  So, if one can possible to go a little bit
below 3 GeV then CLAS
g1c data for pi0 is reachable [DUGGER, PRC76, 025211(2007)]: Eg
= 2875, 2825, 2775 and so on

- I would not use  previous measuremen
<https://halldweb.jlab.org/DocDB/0008/000809/002/GlueX_doc_809.pdf>as the
source to compare with because most of data
came from brem Bonn measurements which systematics is out the control.

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, igor at jlab.org

On Tue, Oct 23, 2018 at 7:54 AM Justin Stevens <jrsteven at jlab.org> wrote:

> 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.
> 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> 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> 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, igor at jlab.org
>>
>>
>> On Mon, Oct 15, 2018 at 12:50 PM Justin Stevens <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
>>> ).
>>>
>>> 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> 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.
>>> Please let me know if you have something you would like to present.
>>>
>>> -Justin
>>> _______________________________________________
>>> Halld-physics mailing list
>>> Halld-physics at jlab.org
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>>>
>>>
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>>
>>
>>
>
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