| PANDA ToF Task Force Questions [message #8919] |
Fri, 26 June 2009 16:32  |
Lars Schmitt
Messages: 47
Registered: April 2004
Location: GSI
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continuous participant |
From: *pools.arcor-ip.net
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Dear colleagues,
In Turin it was decided that we collect a number of questions leading to a decision on the barrel Time-of-Flight detector of PANDA. The aim is to work on these in questions in a task force to find as many answers as possible until the next Collaboration Meeting in September.
In this forum we want to discuss until July 8th what these questions should be. As a starting point I put here the topics raised already at the Technical Board in March:
Detector Requirements
- Minimum time resolution, path length, detector resolution
- Required separation power
- Evaluation of relative timing
Implications on PANDA
- Interaction with EMC
- Minimum material budget, realistic material budget with r/o cables etc
Physics Impact
- Momentum window
- Rejection levels
- Improved global PID
- Channels requiring ToF
Criteria for ToF decision
- Physics case
- Control on conversions
- Budget/groups
Stan Belostotski agreed to coordinate the effort with my help.
We will compile the questions collected here to give them to the
various groups to work on them.
Best regards,
Lars
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| Re: PANDA ToF Task Force Questions [message #8979 is a reply to message #8957] |
Tue, 14 July 2009 12:32  |
Bertram Kopf
Messages: 110
Registered: March 2006
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continuous participant |
From: *ep1.ruhr-uni-bochum.de
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Dear Vladimir and all others,
sorry for the late reply to your posting. During last week I was out of office and even not online. But here - with a delay of few days  - are some answers to your questions/ideas.
| vikhrov wrote on Wed, 08 July 2009 13:49 |
concerning the implication of barrel TOF on PANDA EMC i would propose to make a plot - radiation length of all sub-detectors (MVD, STT/TPC, barrel TOF, barrel DIRC) until EMC versus polar angle. The similar plot was already done for beam & target pipes and MVD (look for example Rene Jakel report on collab. meeting 11.12.2007).
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You can find below the X0 plot for the geometry which we have used for our TOF simulation studies. The barrel ToF is not included here (see also EmcTDR and Physics Book):
| vikhrov wrote on Wed, 08 July 2009 13:49 |
Barrel TOF could be included in 3 options:
1) RPC (X/X0 ~6% as declared, but overlapping and realistic material budget should be taken into account)
2) Scintillator TOF with constant thickness in Z (let it be 4 cm)
3) so called "tapered" scintillator, with ~constant X/X0 versus Z
During the last collab. meeting Bertram Kopf presented the result of his MC simulation for the second option. He didn't found strong theta dependence in losses of efficiency of pi0 reconstruction and S/B ratio (pp. 10&11 of his report). This is what i would like to understand.
For the particles coming from the interaction point (it is true for the gammas from pi0 decay) radiation length depends on polar angle - if at theta=90deg barrel TOF has a X/X0=10% then at 30deg it will be 20% (two times!) and at 20deg will be 29%. But we see 2% drop in efficiency loss at 20deg only. If somebody understand this?
I think we need to continue our MC simulation to understand how barrel TOF material can affect on EMC versus polar angle.
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You are right! One can see just a slight theta dependence. The reason I think is that these plots are the average efficiency and S/B ratio over the hole pi0-momentum range (between 10MeV/c and ~1.6 GeV/c) and that the cos(theta) angle of the pi0 is plotted on the x-axis. As you know, the pi0 decays into two photons with a specific (minimum) opening angle.The plot at (this is just a web-link since it seams to be not possible to upload more than 1 file here):
http://www.ep1.rub.de/~bertram/plot14.png
shows the momentum dependency of the opening angle. That means that the the direction of the two photons can be strongly different to the pi0 direction.
Best regards,
Bertram.
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Attachment: X0.png
(Size: 16.88KB, Downloaded 574 times)
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| Re: PANDA ToF Task Force Questions [message #8990 is a reply to message #8988] |
Wed, 15 July 2009 17:55 |
Bertram Kopf
Messages: 110
Registered: March 2006
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continuous participant |
From: *ep1.ruhr-uni-bochum.de
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Dear Klaus,
| Klaus Föhl wrote on Wed, 15 July 2009 17:21 |
Our interest also involves gamma pi0, and in the context of signal and background channels I have been explained that pi0 pi0 is also an important channel. The simulations that you showed in Torino, are they based on the PandaROOT framework?
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the results from Torino are based on the full simulation with the old BaBar-like software. We have also studied the gamma pi0 channel w/ and w/o the Barrel ToF. I didn't show these results there because the efficiency loss and the decrease of the signal to background ratio originated by the Barrel ToF are similar in comparison to the results of the gamma gamma channel.
Best regards,
Bertram.
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