sPHENIX tracking discussion

[Carlos Perez <carlos.perezlara AT stonybrook.edu>]

Dear Ed,

Yes, the gas is the same.

1) The difference in volume affects the initial charge density (ICD) in two ways:

> The 1/r^2 dependence, increases it: Our TPC being closer to the IP.

> The reduction in the drift length decreases ICD.

> The mean multiplicity in sPhenix is smaller than in ALICE, that also decreases ICD.

> The IonFeedBack was considered to be 30% that of ALICE in its TDR, that decreases the ICD also.

With all those considerations the ICD was computed to be slightly higher than ALICE TDR (no bigger than 130 fC/cm^3)

2) Event with such ICD, since the volume is smaller, the deformation in the Electric Field is computed to be about half that of ALICE.

3) The total deformations in R is a path integral of Er/(Ez+E0). So the deformation is reduced two fold: first due to the smaller induced Er and second due to the smaller path length.

Putting all this together, the computations I presented on Friday expects us to have a factor 10 reduction compared to ALICE.

Regards,

P.S. Sorry for not replying before. Tom just forwarded me your email. I am not able to received mails from the tracking-list, even though I register myself twice already.

***************************

Carlos E. Perez Lara

Stony Brook University

Physics and Astronomy

New York, U.S.A.

***************************

On Apr 17, 2016, at 4:09 PM, Thomas K Hemmick <hemmick AT skipper.physics.sunysb.edu> wrote:

---------- Forwarded message ----------
From: EdwardOBrien <eobrien AT bnl.gov>
Date: Friday, April 15, 2016
Subject: [Sphenix-tracking-l] sPHENIX tracking meeting Friday, April 15 at 9:00 am ET
To:
Cc: sphenix-tracking-l AT lists.bnl.gov, eobrien AT bnl.gov, Carlos Perez <carlos.perezlara AT stonybrook.edu>, Thomas K Hemmick <hemmick AT skipper.physics.sunysb.edu>

    Hi Carlos,
     I wanted to understand better why the mean distortion in r
     that you show in slides 6-9 is an order of magnitude less
    in the model for the sPHENIX TPC than in the ALICE TPC.
    You presume the gas is the same, Ne-based, that
    the sPHENIX TPC has 1/3 the drift distance and 1/2 the
    gain. Are any other parameters important in creating
    this difference? Thanks.

    Ed

On 4/14/2016 11:15 AM, Frawley, Anthony wrote:

HI All,

We will have an sPHENIX tracking meeting tomorrow, Friday April 15, at 9:00 am ET. The Indico page is:

https://indico.bnl.gov/conferenceDisplay.py?confId=200

The agenda is still clarifying.

In addition to reports on the detector options, I would like to have a general discussion about what is needed to meet the ALD's charge on detector cost. Mainly I would like to discuss what we will need to do to characterize the physics deliverd by tracking options, and how we will do it.

Cheers

Tony

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