[Frost] Neutron Measurements with FROST

Mon May 24 22:42:34 EDT 2010

... three neutrals ...

On 5/24/10 10:39 PM, Volker Crede wrote:
> 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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