[Frost] Neutron Measurements with FROST

[Volker Crede]

Barry,

I agree that bump-hunting is not the best idea. If I remember correctly, 
the neutron cross sections around 1600-1700 MeV are not a factor of 5 to 
10 lower than the proton cross sections, but even bigger.

However, I agree that acceptance is indeed a big problem with two neutrals 
in the final state ... my mistake.

     Volker


On Mon, 24 May 2010, Barry Ritchie wrote:

> As I've often said, I'm not a big fan of bump-hunting anyway, but this
> strikes me as very, very dicey motivation. Note that just finding a
> reasonable signal for photoproduction on the proton using FROST has been
> incredibly difficult because the target backgrounds are relatively
> ENORMOUS. Any event signature restrictions just makes the miniscule peak
> even smaller. I don't know whether Brian has anything up more recently,
> but I recall what he was getting in March:
> http://www.jlab.org/Hall-B/secure/g9/morrison/eta_scheme_tests/eta_schem
> e_testing.html
>
> The only thing we're likely seeing there is threshold photoproduction
> near 800 MeV. Up where you guys are talking about, the peak is probably
> not visible at this time.
>
> The neutron cross sections will be between factors of 5 to 10 lower than
> the proton cross sections, if we are to believe the GRAAL numbers. So,
> I'm not optimistic at all that looking for eta photoproduction on the
> neutron using FROST is going to be feasible.
>
> And, whatever the decision, you absolutely cannot break up a few-week
> run period and hope to see anything at all.
>
>
> ---BGR
>
> Professor  Barry G. Ritchie
> Department of Physics
> Arizona State University
> Tempe, AZ  85287-1504
>
> Telephone: (480) 965-4707
> Fax: (480) 965-7954
>
> -----Original Message-----
> From: frost-bounces at jlab.org [mailto:frost-bounces at jlab.org] On Behalf
> Of Volker Crede
> Sent: Monday, May 24, 2010 4:32 PM
> To: Igor Strakovsky
> Cc: FROST
> Subject: Re: [Frost] Neutron Measurements with FROST
>
> Igor,
>
> the D15(1675) resonance was just an idea; it's most likely not the
> reason
> for the narrow structure, but probably contributing in this mass range.
> The picture I sent out is actually from an internal CBELSA/TAPS note and
>
> has been the basis for some discussion about this narrow structure.
>
> The MAMI data I mentioned have not been published, yet. I also have not
> seen anything. Bernd Krusche told me about it (private communication);
> if
> I remember correctly he has a student working on this.
>
> Whatever the details, I think this is what we should do.
>
>     Volker
>
>
> On Mon, 24 May 2010, Igor Strakovsky wrote:
>
>> Hi Volker and Frosters,
>>
>> When I spoke to Eugene privately before meeting then my request was
> the
>> same - to study W = 1600 - 1750 MeV range first of all.  The reason
> was
>> exactly the same because GRAAL, CB-ELSA, and LNS observations agreed
>> with our predictions for the N(1680) which we found using modified piN
>> PWA [PRC69, 035208(2004)].  ChSA helped with some estimations for its
>> decay modes.  Let me say that prlm GRAAL data shown a good structure
> in
>> the K-Lambda final state as well. I do not know what MAMI (B or C)
> data
>> are you talking about but I will report CB at MAMI data for gp-->etaP
> in
>> two weeks on MENU10.  There is interesting behavior in the
> differential
>> cross section around W = 1670 MeV
>>
>> I do not think that idea that D15(1675) is responsible for this effect
>> makes any sense.  Let us collect new data to see what is going on
>>
>> Cheers, Igor
>>
>> On Mon, 24 May 010 17:33:50 -0400 (EDT), Volker Crede
>> <crede at hadron.physics.fsu.edu> wrote:
>>
>>>  Hi all,
>>>
>>>  last Wednesday in the FROST meeting, we started discussing the
> possible
>>> physics case for a short, three-week long FROST run for measurements
> off
>>> the neutron using deuterized butanol. In my opinion, the most
> interesting
>>> physics topic to advertize would be the study of the 1650-1700 MeV
> mass
>>> region in eta photoproduction. Using a linearly-polarized beam at 1.1
> GeV
>>> coherent edge position would be ideal; in combination with transverse
>
>>> target polarization, the observables H and P can be measured.
>>>
>>>  The reason why this interesting is the relatively narrow structure
> that
>>>  has
>>> been observed at 1680 MeV off neutrons bound in the deuteron at:
>>>
>>>  * GRAAL (width < 30 MeV): Kuznetsov et al., Phys. Lett. B647 (2007)
> 172.
>>>  * ELSA (width < 60 MeV): I. Jaegle et al., PRL 100 (2008) 252002.
>>>  * MAMI (width about < 40 MeV): not yet published
>>>  * Tohoku-LNS (width < 40 MeV):
>>>     F. Miyahara et al., Prog. Theor. Physics Supplement 168 (2007)
> 90.
>>>
>>>  A pronounced bump appears in the total cross section. Although the
> nucleon
>>> resonance, D15(1675), is not a likely cause of the narrow structure,
> it's
>>> role in this reaction is not entirely understood; it cannot be ruled
> out
>>> that significant contributions from this state in addition to the
> narrow
>>> structure cause the much slower fall-off of the neutron cross section
> in
>>> this energy region compared to the proton. I have attached a picture
> with
>>> sensitivity studies on the D15(1675) using MAID at 1 GeV. The solid,
> red
>>> curves indicate the full model; the dashed, blue curves without
> D15(1675).
>>> The model predicts asymmetries of measurable size for basically all
> pol.
>>> observables. The cross section data are from ELSA, the beam asymmetry
> was
>>> measured at GRAAL.
>>>
>>>  Taking data for all other reactions simultaneously is certainly also
>>>  useful,
>>> but since we have only three weeks, I think eta photoproduction
> offers this
>>> particular physics case. A dedicated run at 1.1 GeV for both
> transverse
>>> target polarizations (to get H and P) would be very useful.
>>>
>>>  What do you think?
>>>
>>>     Volker
>>
>> Igor Strakovsky, SAID CNS The George Washington University
>> Tel: 703-726-8344(NV),202-994-4742(FB),Skype: igors1945_2
>> Fax: 202-994-3001(FB),Emails: igor at va.gwu.edu, igor at jlab.org
>>
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