[Clas_cascades] Minutes 9/9/2010

[Eugene Pasyuk]

Igor, come on! Be serious.
There is nothing wrong with having 60 papers. They are all done with 
collaborators. Half of them conference talks, by the way.
You yourself have 18 for the same period of time. Is it good or bad? :)

-Eugene

Igor Strakovsky wrote, On 09/12/10 13:11:
> Dear Zhiwen,
>
> Thank you for your detail clarification and let me continue...
>
> On Thu, 09 Sep 2010 00:46:51 -0400, Zhiwen Zhao<zwzhao at jlab.org>  wrote:
>
>> On 09/03/2010 11:31 AM, Igor Strakovsky wrote:
>>> Dear Zhiwen,
>>>
>>> I have several questions to you...
>>>
>>> 1) I am a little bit confused - what is the purpose of your analysis? In
>>> particular, you pretend to compare with the LEPS experiment. But your
>>> plots show that you have practically no statistics below 20 deg. This is
>>> especially so for "on Lambda(1520)", where interference amplification
>>> could be expected.
>
>> The purpose of the study is search for Theta+ production on neutron by
>> detecting all particles pK0Km except the spectator proton. This not a
>
> Wait a minute.  You do not have a 'spectator' condition because CLAS
> cannot detect protons with momenta below 200 MeV/c (this fact is well known
> for the CLAS community).  So, it does not work for you.
>
>> direct comparison to LEPS result because they are looking at a different
>> decay channel nKpKm. If you believe Theta+ may decay into pk0 and nKp at
>> the same time, you should assume this study is meaningful.
>
> Do you mean, pK0p and/or nK+p  systems accompanying K- ?
>
>> And I believe this channel actually has some advantage because we can study
>> exclusive reaction, while the channel LEPS used depends on some models and
>> they could be questionable ( see the paper pointed out by Eugene here
>> http://arxiv.org/abs/1008.4978 ).
>
> Your final states are equally exclusive (or not exclusive) since you do not
> see explicitly one of protons, while LEPS does the same for the neutron. What
> about Oset's exercises, please see my comments below...
>
>> I heard LEPS is looking into the same
>> channel and I don't know what's their outcome yet.
>> I have some slides in the talk I gave last year about the background info.
>> http://www.jlab.org/Hall-B/secure/hadron/meetings/19mar10/hadron20100319_zwzhao_Lambda1520Theta+.pdf
>>
>> So again this's not a direct comparison to LEPS result, but a search for
>> the same physics. Therefore, some of conditions and cuts LEPS used could
>> be borrowed to see what we have.
>> For my understanding, LEPS didn't cut out Lambda1520, but their Theta+ signal
>> is well separated from Theta+, see the Fig 12(b) in their 2009 paper here
>> http://clasweb.jlab.org/rungroups/eg3/wiki/images/f/f4/PhysRevC.79.025210.pdf
>> We can decide to cut on Lambda1520 away or not, but in the plots, I shows
>> them all.
>
> If you do not want to make a direct comparison to LEPS result, why your
> slides are still doing that?  Specifically that you have null statistics
> for the LEPS configuration.
>
>>> BTW, Takashi Nakano told me that he tried to change his setting so to
>>> reproduce CLAS conditions, and it does not work for him.
>
>> This is a very interesting comment. As you know, LEPS have very different
>> coverage from common CLAS setting. They have the very forward angle
>> detector which CLAS only can do with negative field. eg3 is the only run
>> so far has the potential to have some overlap with LEPS coverage. I am
>> curious about what did not work for him.
>
> Nakano's plan was to build up a new detector with CLAS coverage.
>
>>> 2) Then, is it possible to see your Ks recoil spectrum? Its structure,
>>> with well known Sigma and Lambda states, would allow to estimare how
>>> good your selected pi+pi- pairs correspond to K0 decay products.
>
>> Lambda1520 production study is not completed yet, but in good shape. I
>> used pkm invariant mass for the study, not xk0 because it's not a free
>> target. but the K0 invariant mass plot can be seen at the same wiki page
>> and in my talks. However I have to study its large background more
>> carefully.
>
> I (let me hope that everybody as well) would love to see your KS plot.
> If your background condition is so bad, then you have a chance to miss
> events which you look for.
>
>>> 3) As far as I can see, your collinear cut is cos(theta)>0.9 while the
>>> ODU analysis demonstrated thar the optimal boundary is 0.98, and
>>> definitely not less than 0.95. Can you do such cut?
>
>> I can try to do a tighter cut, but I won't be left with good stat
>> because its an elusive reaction while ODU study is inclusive. And
>> again this related to K0 background which I have to deal more
>> carefully,
>
> So, that is a compromise between physics which you are willing to look
> for and your statistics.  In other words, you will have a chance to
> conclude that you do not have a sensitivity
>
>>> 4) For the pK-Ks events you show us the spectra M(pKs). But the ODU
>>> analysis has demonstrated that such spectra have a bad resolution,
>>> because of proton measurements in CLAS. Could you show instead the
>>> spectra of MM(K-)?
>
>> I have to study the resolution issue also the background from k0. but I
>> doubt MM(K-) will really help me because the D target. Anyway, I will
>> check it.
>
> I look forward to see how you check will go through.
>
> Now back to Oset...
>
> The fact is that Eulogio Oset has two papers addressed to his analysis
> of the LEPS Theta measurements
>
> arXiv:1003.1098
> Title: Study of the gd->K+K-np reaction and an alternative
>          explanation for the "Theta+(1540) pentaquark" peak
> Authors: A. Martinez Torres, E. Oset
> Journal-ref: Phys.Rev.C81:055202,2010
>
> arXiv:1008.4978
> Title: A novel interpretation of the "Theta+(1540) pentaquark" peak
> Authors: A. Martinez Torres, E. Oset
> Journal-ref: Phys. Rev. Lett. 105, 092001 (2010)
>
> You missed the recent show in Williamsburg where Eulogio presented his
> exercises which Phys Rev C published then
>
> Ken Hoks led this section and after Eulogio's talk we had an interesting
> discussion
>
> As Takashi Nakano pointed out that Oset's high statistics calculation
> does not show any narrow structure, and the papers lack any quantitative
> arguments. Their simulation is too simplified (it does not include decays
> in flights, momentum-dependent acceptances, detector resolutions and so
> on...). Moreover, their integration method is not consistent with a
> statistical law.
>
> I asked Oset to show what would be going on in his approach with the well
> known Lambda(1520), but Eulogio refused to do that.
>
> Overall, the fact is that only a better experiment can tell if an
> experimental result is due to fluctuations or not.
>
> One more curious thing...
> Qspires shows that Oset has 60 papers during 2009-2010
> http://www.slac.stanford.edu/spires/find/hep/www?rawcmd=FIND+A+OSET%2C+E.+AND+DATE+AFTER+2008&FORMAT=www&SEQUENCE=
>
> The question is - how a theorist can do 60 papers for less than 2 years?
>
> That is all by now,
> Igor
>
>>> Elton,
>>>
>>> Recently, your committee accused the ODU analysis for using a t-cut. Now
>>> your suggestion to Zhiwen is to do just the t-cut. Have you changed your
>>> mind?
>>>
>>> Thanks, Igor
>>>
>>>
>>> On Thu, 2 Sep 2010 09:29:21 -0400 (EDT), Elton Smith<elton at jlab.org>
>>> wrote:
>>>
>>>>
>>>> Present: Elton, Hovanes, Zhiwen, Kijun, Stepan
>>>> On the phone: Ralf<br>
>>>> Notes by Elton.
>>>>
>>>> == Announcements==
>>>> # Hovanes will run the next meeting, 8:00 am Sep 9
>>>>
>>>> == Draft of Phi-- Paper (Hovanes) ==
>>>> # Started including sections of the analysis note and submitted to cvs,
>>>> but not yet ready for other input
>>>> # There will be quite a long sections included, but they can then be cut
>>>> back
>>>> # Asked whether there should be discussions of two sets of cuts (liberal
>>>> and conservative): Elton: Focus on the set of cuts used for the upper
>>>> limit. It makes the paper simpler and easier to read.
>>>> # Stepan: Compare results to normal cascade cross sections
>>>>
>>>> == Theta+ (Zhiwen) ==
>>>> # Started looking at g n ->  K-K0p(p), with Theta+ ->  K0p.
>>>> # Advantages of eg3 are better acceptance for K- in forward direction,
>>>> and
>>>> larger overlap with LEPS kinematics compared to other CLAS analyses
>>>> # Invariant mass plots of (K0p) shown. No indication of a peak in the
>>>> region close to 1530-1540.
>>>> # Stepan: list of cuts to consider are a) Missing mass peak b) photon
>>>> energy cuts c) t-cuts.
>>>> # Elton: Suggests to only use missing mass cut for primary mass spectrum,
>>>> and use t-ranges as a selection only to compare to LEPS data.
>>>> # Elton: Try to get an estimate of an upper limit to see if it is
>>>> competitive with LEPS published results.
>>>>
>>>> == Next Meeting Sep 9, 8:00 am ==
>>>> # Phi-- Draft of paper (Hovanes)
>>>> # Theta+ update (Zhiwen)
>>>> # Analysis note for Lambda(1520)?
>>>>
>>>>
>>>> Elton Smith
>>>> Jefferson Lab MS 12H5
>>>> 12000 Jefferson Ave
>>>> Suite # 16
>>>> Newport News, VA 23606
>>>> elton at jlab.org
>>>> (757) 269-7625
>>>> (757) 269-6331 fax
>
> 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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