[Frost] Neutron Measurements with FROST

Mon May 24 22:31:12 EDT 2010

Barry,

If we are to explore the bump, we need to determine if there is a usable 
signal to exploit.

I talked today with Eugene regarding the eta channel with a FROST deuteron 
target. The eta is a no go. We would have to pick up the neutron and 
reconstruct the eta. This would kill the signal. There is some talk about 
using kaons and going for a fully charged final state.

To go the kaon route, we would have to know how likely it would be to get 
a usable signal. I am not current on the FROST kaon analyses. We need the 
people experienced with these analyses to inform us as to the needed 
statistics to do fine energy binning in the region of interest.

Since time is running short, it is important to narrow down the possible 
physics motivations quickly.

-Michael

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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