[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: Thoughts on motivating tof for Review
Hi Alex -
thanks for summarizing the contents of this note. I believe that
the p-pi separation in the BCAL is something that we have
been claiming for quite some time now. The fact that it works
with a "pesimistic" timing resolution in the BCAL is indeed very
good.
If we couple this result with what Matt Bellis has been showing
about what we can do with a kinematic fit, we see that separation
of pi and K is possible, but with a well designed PID system, the
separation and acceptance will go way up.
Cheers -- Curtis
On Mon February 25 2008, Alex Dzierba wrote:
> Hi Elke
>
> I wanted to add to your comments....
>
> With regard to BCAL and timing w.r.t to PID, as you once pointed
> BCAL might be used for pi/proton separation but not for pi/K.
> In my kinematics note (GlueX-doc-838) I showed the momentum
> spectrum for charged particles hitting BCAL from the K*K*p
> reaction (K-pi-K-pi p). There are no particles with momentum
> less than 1 GeV and the pion spectrum peaks at 2 GeV and the
> K spectrum at about 3 GeV. (Fig 25c). The charged particles
> have to have pt > 0.435 GeV to hit BCAL. Even with the pessimistic
> timing for MIP, the BCAL timing resolution of about 420 ps for
> MIPS is sufficient to separate any proton reaching BCAL from
> a pion. Recall that Stefano felt that our current estimate of
> BCAL timing for MIPS (based on cosmic rays) was probably too
> pessimistic - I think he said KLOE achieved 300 ps. But even this
> would not suffice for pi/K separation. It is true that we are
> working on overall timing for BCAL -- especially for photons
> (time difference and mean time) -- and I think we'll have solid
> results soon but they will not change the overall conclusions
> above re PID. And one last comment here: Stefano also said
> that the KLOE calorimeter could also be used to identify
> protons via their characteristic energy deposition. I think
> Zisis is studying this for BCAL>
>
> One more comment - I agree that Pythia is great for understanding
> the backgrounds. I also found that the K*K*p reaction, leading to
> two K's and two pi's, kinematically describes most of the interesting
> signal reactions that will lead to this final state (e.g. K_1-K where
> K_1 ->K* pi, etc....). The conclusion is that we need a well-performing
> forward TOF AND a RICH.
>
> For those doing the PID and tracking studies, GlueX-doc-838 has
> more information about relevant kinematics - including the challenge
> of measuring rho decays - in particular with respect to helicity angles.
>
> Cheers
> Alex
>
>
> At 5:52 AM -0500 2/25/08, Elke-Caroline Aschenauer wrote:
> >On Fri, 22 Feb 2008, Elton Smith wrote:
> >
> >Elton,
> >
> >did you discuss this on Friday?
> >
> >Okay, I think before we can talk about PID we need to know the performance
> >of the detectors. So I would think we need to make sure we know the timing
> >performance of the BCal and the latest mails on this indicate we need a
> >bit of work on this, but are already very close.
> >For the forward tof we need the hardware performance, the uncertainty on
> >the momentum and path length. If we have this we can look into the
> >performance.
> >
> >I don't need a MC to know we basically have in the full momentum angle
> >range a factor 1 to 10 for kaons to pions, so we will have a hard time to
> >get kaon id. so all comes to pion to proton separation. Actually there
> >will be also protons in the forward direction.
> >If you talk about pid, than we might also consider some wider physics
> >program, like we want to discuss in a week and than we need also electron
> >id, which of course is not to difficult to get with our em-calorimeters,
> >e/p gives normally a factor 100 suppression of hadrons in the lepton
> >sample. Which might be okay, not great but ...
> >
> >As I was saying I asked Eugene to repeat his studies he did some time ago
> >for the Cerenkov more focusing on the tof in the BCal and the forward.
> >I think pythia gives a very nice possibility to do this, we could for
> >example look to sigmas or lambda(1520) reconstruction if we want to make
> >statements on kaons.
> >
> >For getting a good particle id you actually best measure parent
> >distributions of your final detector with beam and than use the Bayes
> >theorem to get probabilities. I showed this in my talk on the Hermes pid
> >in the collab meeting last October.
> >
> >for the trigger and your timing questions. we should not to much focus on
> >10^7, because as I said in my other email the start counter will have a
> >rough time at 10^8 and so will the tagger, so we should from the beginning
> >have a start time which will work for all rates 10^7 and 10^8. So again
> >what is wrong with the machine clock.
> >
> >For the trigger, I'm not sure how much we have to discuss in detail the
> >trigger, because there we look for hits. I think the new material budget
> >in the beam brings the rates down by a factor of 5 ( I have not all
> >numbers here) so this will give us a certain hit rate in 100ns per paddle.
> >We could make the inner paddles a factor of 2 smaller in width, this is
> >not at all a cost problem. Actually one test would be to make the air in
> >the beam pipe He and see what that helps in addition.
> >
> >I think in the barrel dE/dx has to be included in the picture, of course
> >the threshold for protons coming out of the target is an issue, because it
> >is close to what the range of protons is which can be detected by the CDC.
> >This is something we have to look into very carefully, because the start
> >counter contributes to this threshold for sure quite a bit.
> >
> >If the final pid includes a aerogel rich, which with the improvements in
> >aerogel lello presented is the best thing to do, we will have actually
> >pion id from 0.5 geV on, which is very nice, because having 2 pid
> >detectors overlapping will increase your purity a lot. that is also true
> >combining the rich and the em-calos for leptons.
> >
> >One other thing we have to make sure that the beam hole in the tof is
> >matched to the one of the FDC.
> >
> >so this has become a long email, but as I was not present at the
> >discussion, I thought I type some of my ideas into an email.
> >I guess we will have a detailed discussion on Friday. I can be available
> >for a phone meeting earlier if needed.
> >
> >cheers elke
> >
> >
> >> Friends,
> >>
> >> I spent some time with Matt and Beni to go over the motivation/arguments
> >> for tof in the detector, given that kaon id is very limited. I put these
> >> out for comments/discussion especially in order to define what
> >> calculations/work might need to be done in preparation for the review. We
> >> came up with the following points
> >>
> >> - pion purity (how often are we fooled by other topologies?)
> >> - positive proton id (mostly in the barrel)
> >> - forward tof input to trigger
> >> - timing information for analysis (start time for drift times, rejection
> >> of accidentals coincidences with the tagger)
> >> - part of future comprehensive pid detector package for detector (covering
> >> pi/K id below 2 GeV).
> >>
> >> I would appreciate comments suggestions on what to emphasize and priority
> >> for any studies that are required.
> >>
> >>
> >> Questions:
> >> - What is the granularity (segmetation) required due to rate
> >> considerations?
> >> - What is the spectra of all particle species (pi,K,p) over the detector
> >> (e.g. what is the ratio of particle types in the Bcal and the TOF?)
> >> - Study acceptance of charge particles (actual trajectories in B field)
> >> for the 1deg beam hole and at the largest angles?
> >>
> >>
> >>
> >>
> >>
> >>
> >> Elton Smith
> >> Jefferson Lab MS 12H5
> >> 12000 Jefferson Ave
> >> Suite # 16
> >> Newport News, VA 23606
> >> elton@jlab.org
> >> (757) 269-7625
> >> (757) 269-6331 fax
> >>
> >
> > ( `,_' )+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=
> > ) `\ -
> > / '. | +
> > | `, Elke-Caroline Aschenauer =
> > \,_ `-/ -
> > ,&&&&&V Jefferson Lab +
> > ,&&&&&&&&: HALL-D 12C / F381 121-A Atlantic Avenue =
> >,&&&&&&&&&&; Suite 8 Hampton, VA 23664 -
> >| |&&&&&&&;\ 12000 Jefferson Ave +
> >| | :_) _ Newport News, VA 23606 Tel.: 001-757-224-1216 =
> >| | ;--' | Mail: elke@jlab.org Mobil: 001-757-256-5224 -
> >'--' `-.--. | +
> > \_ | |---' Tel.: 001-757-269-5352 =
> > `-._\__/ Fax.: 001-757-269-6331 -
> > +=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+
>
>
--
Professor Curtis A. Meyer Department of Physics
Phone: (412) 268-2745 Carnegie Mellon University
Fax: (412) 681-0648 Pittsburgh PA 15213-3890
cmeyer@ernest.phys.cmu.edu http://www.curtismeyer.com/