[Clas_cascades] pentaquark search with pK0Km skim

Thu Feb 18 18:33:13 EST 2010

hi, Igor

On 2/18/2010 5:49 PM, Igor Strakovsky wrote:
> On Thu, 18 Feb 2010 14:55:15 -0500, Zhiwen Zhao <zwzhao at jlab.org> wrote:
>
>> Hi, Igor
>>
>> I forgot to answer your questions about the slides.
>
> OK
>
>> The collinear cut is not applied for Lambda1520 cross section study
>> because the cut will enhance signals/background ration, but it will
>> cut away signals.
>> It's used for theta+ search to see it will help any structure stand out.
>
> Your argument sounds strange to me. What is the difference between two
> cases?
Some detailed study can be seen in ODU pentaquark note
http://www.jlab.org/Hall-B/secure/hadron/wiki/index.php/ODU_Analysis_of_Meson-baryon_Interference
Basicly, my idea is that for Lambda1520 cross section study, I can't afford to 
lose signal if the cut can't be well justified in acceptance study for 
simulation. For theta+ study, I am eager to enhance any small signal so I will 
put acceptance consideration aside first just to see if the cut will give me 
anything.
>
>> On the backup slide #24, the top right corner plot shows the K+K- and
>> PK- invariant mass, the crossing indicates where the interference
>> happens. It affects the t-slope below Egamma=2.5 Gev can be seen on
>> the slide 21. ODU had some study of this effect. I didn't show any
>> thing further because my talk focus on cross section only.
>
> Can you show something privately?
There's one talk by Chandra Nepali from ODU here, check page 14
http://www.jlab.org/Hall-B/secure/hadron/meetings/31oct08/cnepali_Lambda1520_Oct31_2008.pdf
But I am sure they have updated plots after they did some combined analysis with 
the Genova group
>
> Thanks, Igor
>
>> Zhiwen
>>
>> On 2/18/2010 1:30 PM, Igor Strakovsky wrote:
>>> Hi Zhiwen,
>>>
>>> Unfortunately, your analysis will not allow to accomplish FSI study. It
>>> requires theor calculations. They may be small but nobody knows how
>>> large
>>> they are.
>>>
>>> Two more small questions for your slides - I did not see your
>>> colleniarity
>>> cuts. Your #10 shown a selection for M(pi+pi-) only. Then your #24 said
>>> about \phi and L(1520) interference but no details
>>>
>>> Hall A data have been published recently Y. Qiang et al. (JLab Hall A
>>> Collaboration), Phys. Rev. C 75, 055208 (2007); arXiv:hep-ex/0609025 and
>>> we made analysis addressed to the determination of the L(1520)
>>> parameters
>>>
>>> Igor
>>>
>>>
>>> On Thu, 18 Feb 2010 12:07:19 -0500, Zhiwen Zhao <zwzhao at jlab.org> wrote:
>>>
>>>> hi, Igor
>>>>
>>>> The statistics won't allow me to study FSI, so I plan to cut on quasi
>>>> free reaction by limiting missing momentum later on.
>>>> I didn't know you are doing Lambda1502 in HallA. That's GREAT news.
>>>> Can you show me some notes or talks you already have?
>>>>
>>>> Thank you
>>>>
>>>> Zhiwen
>>>>
>>>> On 2/17/2010 9:04 PM, Igor Strakovsky wrote:
>>>>> Hi Zhiwen,
>>>>>
>>>>> On Wed, 17 Feb 2010 16:56:21 -0500, Zhiwen Zhao <zwzhao at jlab.org>
>>>>> wrote:
>>>>>
>>>>>> Hi,Igor
>>>>>>
>>>>>> On 2/14/2010 12:45 PM, Igor Strakovsky wrote:
>>>>>>> Hi Zhiwen,
>>>>>>>
>>>>>>> Thank you for your prompt reaction. I would afraid to make a claim
>>>>>>> until
>>>>>>> to get strong arguments. It sounds that you do not have them yet
>>>>>> Exactly, I am not making any claim
>>>>>>>
>>>>>>> A little bit more below
>>>>>>>
>>>>>>> On Sat, 13 Feb 2010 22:28:40 -0500, Zhiwen Zhao <zwzhao at jlab.org>
>>>>>>> wrote:
>>>>>>>
>>>>>>>> Hi, Igor
>>>>>>>>
>>>>>>>> No, I am not sure at this point as the result is just a first look
>>>>>>>> into the data, not even qualified as preliminary.
>>>>>>>> However these cuts I showed are supposed either to enhance the
>>>>>>>> theta+
>>>>>>>> signal or to match LEPS condition.
>>>>>>>
>>>>>>> As your slides shown that you did not do exact LEPS condition
>>>>>> For angle, LEPS has horizontal 20 degree and vertical 10 degree
>>>>>> coverage. So far I require theta < 20 degree and it's only for Km,
>>>>>> not
>>>>>> for all charged particles like LEPS. I will test more cuts.
>>>>>> For photon energy, my cut matches their condition 2-2.4GeV
>>>>>
>>>>> Well, as I said your condition does not fit LEPS configuration well;)
>>>>>
>>>>>>>> I have looked their Anti-cuts also, no sign of theta+ either.
>>>>>>>> Some cuts I didn't show such as photon selection,PID, fiducial,
>>>>>>>> vertex, sc dad counter etc, are mostly standard and similar to what
>>>>>>>> Hovanes used in his
>>>>>>>
>>>>>>> As far as you probably know, CLAS has so many standards. It is
>>>>>>> good to
>>>>>>> clarify them
>>>>>> Some cuts you can see from Hovanes's analysis note
>>>>>> http://clasweb.jlab.org/rungroups/eg3/wiki/index.php/Analysis_review_by_Hadron_Spectroscopy_Working_Group
>>>>>>
>>>>>>
>>>>>>
>>>>>> I am in the process of writing Lambda1520 note also.
>>>>>>>
>>>>>>>> eg3 pentaquark Phi-- upper limit analysis which is currently under
>>>>>>>> review.
>>>>>>>> The same PK0Km channel is used for Lambda1520 study which is my
>>>>>>>> thesis
>>>>>>>> topic, I have preliminary cross section now.
>>>>>>>
>>>>>>> Sorry, I know nothing about your theses and would love to see your
>>>>>>> Lambda(1520). Unfortunately, the size of your figures do not allow
>>>>>>> to see details
>>>>>> Here's a talk I gave for Lambda1520
>>>>>> http://clasweb.jlab.org/rungroups/eg3/wiki/images
>>>>>> /5/52/ApsApril2010_zwzhao_Lambda1520.pdf
>>>>>> I apologize for the figures, I will update them with better ones.
>>>>>
>>>>> Thank you for your figures, I missed them. It seems to me that our
>>>>> coming
>>>>> paper addressed to the analysis of the Hall A Lambda(1520)
>>>>> electroproduction
>>>>> data at small Q2 may be interesting for you. I hope we will submit
>>>>> it in
>>>>> 2-3 weeks.
>>>>>
>>>>> To be honest, your analysis of the neutron data is a big problem
>>>>> for me
>>>>> because you did not take into account FSI
>>>>>
>>>>>>>> I have MC for the Lambda1520 production, but not PK0Km yet.
>>>>>>>
>>>>>>> Can you show them, please? What did you use as the generator
>>>>>> will do.
>>>>>> I use fsgen which is a phase space generator with t-slope=2 as input
>>>>>> for my Lambda1520 channel.
>>>>>
>>>>> OK, thanks. Igor
>>>>>
>>>>>>>> I will add more stuff on the wiki when the analysis proceeds.
>>>>>>>> Any comment from you is greatly appreciated.
>>>>>>>
>>>>>>> Thanks, I look forward to learn more details from you
>>>>>>> Igor
>>>>>>>
>>>>>>>> Zhiwen
>>>>>>>>
>>>>>>>>
>>>>>>>> On 2/12/2010 1:14 AM, Igor Strakovsky wrote:
>>>>>>>>> Hi Zhiwen,
>>>>>>>>>
>>>>>>>>> How are so sure? You made so many cuts... Can you explain all of
>>>>>>>>> them?
>>>>>>>>> Can you show any well known resonances? Do you have MC?
>>>>>>>>>
>>>>>>>>> Igor
>>>>>>>>>
>>>>>>>>> On Fri, 12 Feb 2010 01:04:37 -0500, Zhiwen Zhao <zwzhao at jlab.org>
>>>>>>>>> wrote:
>>>>>>>>>
>>>>>>>>>> hi, Eg3er
>>>>>>>>>>
>>>>>>>>>> Here is some updates of the pentaquark search with pK0Km skim
>>>>>>>>>> http://clasweb.jlab.org/rungroups/eg3/wiki/index.php/PrtK0Km_theta1530
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> So far, there's no sign of pentaquark.
>>>>>>>>>> Any commend is appreciated.
>>>>>>>>>>
>>>>>>>>>> Zhiwen
>
> 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