sPHENIX tracking discussion

[Thomas K Hemmick <hemmick AT skipper.physics.sunysb.edu>]

Hi Takao

Since the space charge is made up from hundreds to thousands of previous events with their positive ionization still lingering in the TPC volume.  The input is the mean multiplicity and these expressions are all averages of that.  The current calculation uses space charge distributed all over the full volume and calculates the distortion of tracks from all starting points.  However to summarize all this as a single number, we look at the distortion of the innermost part of the track for a z=0 particle.  We'll have to think whether that is the best way to compare things, but it certainly the scariest.

Later, you are correct that we need to throw a history of the thousands of events since the IBF consists of "pancakes" of charge.  In this case, you need to input the charged particle multiplicity distribution and throw each previous pancake with a total number of charges set by the multiplicity of each event.  You can then either:

a-  Assume that the space charge is a single static function of position & rate.

b-  Assume that you will used the measured event history to try to understand the details of every pancake.

STAR uses (a) and ALICE plans to use (b) since the situation will be more challenging.  The guess is that we might need to go with (b) and this will be the result of future simulations.  The good news is that Carlos really did a great job in getting to the first meaningful results, but as you point out, there is still much to do.  

Tom

On Fri, Jan 15, 2016 at 10:07 AM, Takao Sakaguchi <takao AT bnl.gov> wrote:

Hi Carlos,

 Thanks for clarification. What I understand from your

answer and Tom's slides from the last meeting is that

you focused both all the ionization electrons and ions

at z=0, which is good as the starting point.

 I assume that the next step is to distribute the 425

charged particles traversing TPC uniformly in phi-rapidity

space, which case that the IFB contribution may be

more significant.

Takao

On Fri, Jan 15, 2016 at 9:52 AM, Carlos Perez <carlos.perezlara AT stonybrook.edu> wrote:

Hi Takao,

The charge distribution is isotropic in phi. The dependence with eta is driven by the amount of time it takes to drift.

The charge density here is parametrised as

rho = A * (1 - |z|/B - D) / r^2

where:

 A is proportional to Multiplicty and Rate and gas conditions

 B is the drift length

 D is proportional to the percentage of back flow

You can find a more detail explanation in previous slides from Tom to the meeting.

Regards,

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

Carlos E. Perez Lara

Stony Brook University

Physics and Astronomy

New York, U.S.A.

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

On Jan 15, 2016, at 9:27 AM, Takao Sakaguchi <takao AT bnl.gov> wrote:

Hi Tom and Carlos,

 Very nice results on the space charge distribution!

 I just would like to ask one question on the result.

 In the distributions shown in slides 11 to 14, the caption

says that the multiplicity is 425 and the rate is 50KHz.

When you throw 425 particles in an event, did you

distribute the particles uniformly in phi-rapidity space?

Or, did you fix all the particles in z=0 plane?

Takao

On Fri, Jan 15, 2016 at 8:58 AM, Thomas K Hemmick <hemmick AT skipper.physics.sunysb.edu> wrote:

Let me go first and I will try to be fast...

There *ARE* initail space charge calculations.

They are about an hour old, so we need them to mature, but nonetheless, I want to credit all the hard work Carlos put in.

I will be on the line in about 4 minutes...

On Fri, Jan 15, 2016 at 8:54 AM, Frawley, Anthony <afrawley AT fsu.edu> wrote:

Would you like to go first, or later? We have three talks including yours, but the others may be shorter.

Thanks

Tony

---

From: tkhemmick AT gmail.com <tkhemmick AT gmail.com> on behalf of Thomas K Hemmick <hemmick AT skipper.physics.sunysb.edu>
Sent: Friday, January 15, 2016 8:52 AM
To: Frawley, Anthony; Carlos Perez
Cc: sphenix-tracking-l AT lists.bnl.gov
Subject: Re: [Sphenix-tracking-l] sPHENIX tracking meeting Friday January 15 at 9:00 am ET

 

Hi guys

Both Carlos and I have some conflicts regarding the meeting (Carlos VISA business at 9:30, Tom interview with candidate for a physics dept hire).  

We'll try to work around them and make a smooth presentation.

Tom

On Thu, Jan 14, 2016 at 2:14 PM, Frawley, Anthony <afrawley AT fsu.edu> wrote:

Hi All,

Here is an updated agenda for tomorrow morning's tracking meeting:

Tom Hemmick - TPC progress

Itaru Nakagawa - silicon strip tracker progress

Rachid Nouicer - Integration of the silicon pixels into sPHENIX

Tony

---

From: Frawley, Anthony
Sent: Thursday, January 14, 2016 11:07 AM
To: sphenix-tracking-l AT lists.bnl.gov
Cc: Frawley, Anthony
Subject: sPHENIX tracking meeting Friday January 15 at 9:00 am ET

 

HI All,

We will have an sPHENIX tracking meeting tomorow, January 15, at 9:00 am ET. The agenda is at:

https://indico.bnl.gov/conferenceDisplay.py?confId=1695

We will have a report from Tom Hemmick on TPC progress, and one from Itaru Nakagawa on silicon strip tracker progress.

Talk to you then

Tony

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--

Takao Sakaguchi
Brookhaven National Laboratory
Physics Department, Bldg. 510C
takao AT bnl.gov
Office: 1-631-344-3345

--

Takao Sakaguchi
Brookhaven National Laboratory
Physics Department, Bldg. 510C
takao AT bnl.gov
Office: 1-631-344-3345