[Clas_lmd] Review of analysis procedure

Fri Jul 17 07:10:50 EDT 2015

Hi Volker,

This enhancement at 1020MeV might be a phi. Since the eta is missing 
maybe a photon got misinterpreted as an eta. The phi(1020) goes to pi pi 
gamma. But this peak gets totally suppressed after the Q-value method, 
so every misinterpreted gamma gets suppressed. I think I mentioned this 
problem during my talk, but maybe I forgot.
The text says right, maybe I misplaced the line a little bit.
For the plots your are asking for:
1) I cutted on the pi0 in the missing mass. The beam energy is as 
suggested. Tha angular distribution are in lab frame. Is this what you 
wanted or do you want it in the cms frame?
2) I cutted on the eta in the missing mass.The beam energy is: , due to 
statistics I had to go higher  to 1.7GeV <E_gamma <1.8 GEV. Also lab frame.
You could find them here: www.ep1.rub.de/~cathrina

Cheers,
Cathrina

On 07/16/15 23:20, Volker Crede wrote:
> Hi Cathrina,
>
> I also have a question, something I did not notice at the 
> collaboration meeting. On Slide 14, you are showing the unweighted "pi 
> pi eta" invariant mass which exhibits a clear peak for the eta' 
> including background just below 0.96 GeV … However, there is another 
> peak at 1.02 GeV = 1020 MeV = mass of the phi meson. Why do you see a 
> peak at 1020 MeV or am I missing something? According to the text, the 
> cut on the eta' is 0.9 GeV < m < 1.02 GeV but in the plot, the cut is 
> 0.9 GeV < m < 1.0 GeV.
>
> At FSU, we have found recently (this week) massive holes in the 3pi 
> mass distributions close to the omega threshold and in the forward 
> direction. Unfortunately, this affects our cross section below 1.5 GeV 
> in photon energy. This could be similar to a discussion we had in 
> FROST a while ago and be related to inefficiencies in the drift chamber:
>
> * Would you have a plot of your 3pi mass distribution, perhaps for 
> 1300 - 1400 MeV in incoming photon energy and cos(theta_3pi) > 0.5?
>
> * And a similar distribution for the "pi pi eta" invariant mass in the 
> forward direction, perhaps 200 - 300 MeV above the eta' threshold?
>
> Cheers,
>
> Volker
>
>
> On Jul 16, 2015, at 4:14 PM, Lei Guo <lguo at jlab.org 
> <mailto:lguo at jlab.org>> wrote:
>
>> Hi, Cathrina,
>>
>> Did you apply the track-dependent efficiency correction that g12 has 
>> been using (developed by MK)? You have three tracks in your final 
>> state, and that correction can add up to around 18% for some 
>> kinematic bins.
>>
>> Lei
>>
>>
>> Lei Guo
>> Assistant Professor
>> Physics Department
>> Florida International University
>> Miami, FL
>>
>> email: leguo at fiu.edu <mailto:leguo at fiu.edu> or lguo at jlab.org 
>> <mailto:lguo at jlab.org>
>> Office:305-348-0234
>>
>>> On Jul 16, 2015, at 3:48 PM, Eugene Pasyuk <pasyuk at jlab.org 
>>> <mailto:pasyuk at jlab.org>> wrote:
>>>
>>> Dear Cathrina,
>>>
>>> Can you briefly explain how did you resolve the issue with the 
>>> energy dependent scaling factor you had. What was the problem?
>>> Even though you eliminated this energy dependent normalization 
>>> factor there are still some discrepancies between g11 and g12 cross 
>>> sections. Sometimes as large as 20% or even more. Log scale somewhat 
>>> hides it but it is there. This needs to be studied further.
>>> I think you can show your cross sections but have to be careful with 
>>> your statement. You may say that in general the shape of the angular 
>>> distribution agrees well between the two datasets. Some 
>>> discrepancies are present and being investigated. Since this is 
>>> preliminary data make sure that all you cross section plots are 
>>> labeled as preliminary. Once you have your slides prepared please 
>>> distribute them before the conference.
>>>
>>> And one more suggestion for the future. Our mailing lists have 
>>> limitations on the maximum size of the message.
>>> I believe it is 40 kB or so. If you want to share some files post 
>>> them on the web somewhere and include the link in you mailing list post.
>>>
>>> Cheers,
>>>
>>> -Eugene
>>>
>>> ----- Original Message -----
>>>> From: "Cathrina Sowa" <cathrina at ep1.ruhr-uni-bochum.de 
>>>> <mailto:cathrina at ep1.ruhr-uni-bochum.de>>
>>>> To: "Eugene Pasyuk" <pasyuk at jlab.org <mailto:pasyuk at jlab.org>>, 
>>>> "DEVITA" <devita at ge.infn.it <mailto:devita at ge.infn.it>>, 
>>>> jordanka at physics.sc.edu <mailto:jordanka at physics.sc.edu>, 
>>>> "g12 at jlab.org <mailto:g12 at jlab.org>
>>>> g12 at jlab.org <mailto:g12 at jlab.org>" <g12 at jlab.org 
>>>> <mailto:g12 at jlab.org>>, "clas lmd" <clas_lmd at jlab.org 
>>>> <mailto:clas_lmd at jlab.org>>
>>>> Sent: Thursday, July 16, 2015 10:00:57 AM
>>>> Subject: Review of analysis procedure
>>>
>>>> Dear colleagues,
>>>>
>>>> I would like to present preliminary results of the analysis (gamma p ->
>>>> p pi+ pi- (eta))
>>>> I am working on at a parallel session at the upcoming EUNPC 2015
>>>> conference in Groningen.
>>>>
>>>> The analysis was presented at the CLAS collaboration meeting in 
>>>> June at the
>>>> the Hadron Spectroscopy session [1]. All concerns and comments raised
>>>> during the
>>>> discussion after the talk have been considered. The energy dependent
>>>> scaling factor for
>>>> the differential cross section for example is now no longer needed.
>>>>
>>>> In order to follow the required procedure, Johann and Mario advised 
>>>> me to
>>>> discuss the updated analysis with the g12 run group. Below I prepared a
>>>> summary of the
>>>> data selection and preliminary results I would like to include in my
>>>> presentation.
>>>>
>>>> I would be happy about any comments and suggestions from your side.
>>>>
>>>> Best regards,
>>>> Cathrina
>>>>
>>>> [1]: 
>>>> https://www.jlab.org/Hall-B/secure/hadron/meetings/18jun15/sowa.pdf
>>>>
>>>>
>>>> MOTIVATION
>>>> Study of excited eta states in photo production, with
>>>> emphasis on the production of the glueball candidate eta(1405). The
>>>> eta(1405)
>>>> production in photo-production can be compared to its production in
>>>> gluon-rich processes to shed further light on its nature.
>>>>
>>>> As a reference and validation for the upper limit of the eta(1405) 
>>>> cross
>>>> section, the
>>>> eta' differential cross section will be determined and compared to the
>>>> published g11
>>>> results.
>>>>
>>>>
>>>> DATA
>>>> - run numbers: 56520-56572, 56573-56594, 56608-56646 which were
>>>> event-sorted
>>>> according to 2-2pos1neg_not_1ckaon1ctrk
>>>>
>>>> - fulfilling the same trigger conditions: 3 charged tracks in 3
>>>> different sectors or
>>>> 2 charged track in 2 different sectors with a beam energy above 3.6 GeV
>>>>
>>>> EVENT SELECTION
>>>> - two positively-charged tracks for the proton and the pi+ as well as
>>>> one negatively-charged track for the pi−.
>>>>
>>>> - g12_ecor.hpp package is used for the beam energy corrections
>>>>
>>>> - g12_pcor.hpp package is used for momentum correction
>>>>
>>>> - Energyloss was accounted with the the standard eloss corrections
>>>>
>>>> - All three particles correspond to the same beam photon
>>>>
>>>> - Standard cuts on vertices (Fig1, Fig2), minimum momenta(Fig3), 
>>>> beta Vs
>>>> momentum(Fig4), fiducial volume (Fig5) and timing (Fig6) are included
>>>>
>>>> - Q-value method applied on the missing eta to achieve a better
>>>> background suppression (Fig7) (Black: Before, Blue: 1-Q weighted, 
>>>> Red: Q
>>>> weighted)
>>>>
>>>>
>>>> PRELIMINARY RESULTS
>>>>
>>>> Fig8: inv. eta pi+ pi- mass spectrum
>>>>
>>>> red w/ error bars: w/o Q-weight; blue: Q-weighted
>>>>
>>>> Fig9: differential eta' cross section
>>>> - GEANT based Monte Carlo events are used for efficiency correction
>>>> following the procedure documented in the g12 wiki
>>>>
>>>> - The photon flux is obtained as described in the g12 wiki
>>>>
>>>> - To compare to the published g11 results, the same W binning is used
>>>>
>>>> Fig8: Comparison of the diff. eta' cross section for g11 (pink) and g12
>>>> (black) data
>>>> The distributions are in good agreement now.
>>>>
>>>> --
>>>> M.Sc. Cathrina Sowa
>>>> Ph. D. student
>>>> Institut für Experimentalphysik I
>>>> Ruhr-Universität Bochum
>>>> Universitätsstr. 150
>>>> 44801 Bochum
>>>>
>>>> Office: NB 2/74
>>>> Tel.: 0234-32-23564
>>>> Web: www.ep1.rub.de <http://www.ep1.rub.de/>
>>>
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-- 
M.Sc. Cathrina Sowa
Ph. D. student
Institut für Experimentalphysik I
Ruhr-Universität Bochum
Universitätsstr. 150
44801 Bochum

Office: NB 2/74
Tel.: 0234-32-23564
Web:www.ep1.rub.de  

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