Re: coordinate system

     Tim and Maury, thanks very much for your response to my question
regarding isotropy of neutrinos from the reactors.
     Getting back to coordinate systems, I don't know how far you all got
to at the last Veto meeting that I could not attend, but has anyone
considered using the "beam" direction from symmetry point between the two
reactors to the center of the detector as Tim mentioned earlier? It seems
to me that one could define two systems, each with beam direction from mid
point between reactors to center of each detector, with second axes
perpendicular to beam and parallel to earth's surface. The third axes
would be mutually orthogonal to the first two. This means the vertical
for the detector and veto would be tilted with respect to the third axes
(different amounts forthe two detectors). I don't think this is
important since the vertical direction may be a symmetry axis for the veto
but is of no special interest for the detectors, whereas the beam
directions are. The veto could do everything in earth vertical
coordinates and transform results into detector coordinates. Since the
two detectors are completely independent from each other, and ultimately
we are interested in flux direction from reactors to detectors, having two
coordinate systems seem to be a minor inconvenience, if any.
     I'd appreciate any comments on this suggestion.

Best regards,
Dick
 +----------------------------------------------------------------------+

On Thu, 23 Dec 2004, Maury Goodman wrote:

> The neutrinos are isotropic, but there is a geometry effect (I'm not
> sure if this is
> what Dick was referring to or not.) The core has a finite size, and
> because fuel rods are
> loaded to maximize power, the energy distribution of the neutrino source
> varies through the core.
> There is a small angular effect on the neutron in inverse beta decay.
> Applied together, there is
> a small effect on the near detector, and effectively none at the far
> detector. I have a memory that
> someone calculated this as a 0.1% difference, but I couldn't find it
> this afternoon. It can obviously
> be calculated with a good Monte Carlo, and then minimized further with
> some information about fuel
> loading, if needed.
> Maury
>
> "Bolton, Tim" wrote:
> >
> > Dick,
> >
> > I think the answer is that isotropy is assumed and highly likely. But I suspect that this has never been verified with the antineutrinos, although perhaps it has with the beta decay electrons.
> >
> > The immediate issue with the coordinate system is to define the veto system in simulation in a way that the nu detector simulation understand it and vice versa. But it's probably worth thinking about making a good overall choice.
> >
> > Happy Holidays
> >
> > TB
> >
> > Tim Bolton
> > Professor
> > High Energy Physics Group
> > Kansas State University
> > tbolton@ksu.edu
> > 785-532-1664
> >
> > ________________________________
> >
> > From: Richard K. Yamamoto [mailto:rky@mit.edu]
> > Sent: Thu 12/23/2004 1:42 PM
> > To: stefanski@fnal.gov
> > Cc: Bolton, Tim; Jonathan Link; braidwood@hep.uchicago.edu
> > Subject: Re: RE: coordinate system
> >
> > Hi Folks,
> >
> > I'd like to add my two cents, which is all what I say may be worth.
> > The details of coordinate systems, etc. seems to me somewhat minor,
> > since once defined, its just a matter of coordinate transformations,
> > regardless of how complicated this may end up being. I have a naive
> > question, not quite related to coordinates but may be a bigger sytematic
> > question: how well do we know the neutrino flux distribution in angle with
> > respect to, say, the surface of the ground? Since the detectors are at
> > different distances from the reactor core, if this distribution is not
> > known because it may not be isotropic, the relative flux between detectors
> > may not be able to be calculated to the precision we need. Perhaps this
> > can be studied through simulations, but can we ever measure this?
> > I'd be happy if someone can tell me I'm worrying about nothing, so I
> > can enjoy the Holidays.
> >
> > Best regards, and Happy Holidays!
> > Dick Yamamoto
> >
> > +----------------------------------------------------------------------+
> >
> > On Wed, 22 Dec 2004 stefanski@fnal.gov wrote:
> >
> > > Hi,
> > >
> > > 1. If "up" is determined by the liquid, each detector will have a slightly different vertical axis. The earth's curvature is about 6 micro-radians per mile. Small, but might be significant for the difference between near and far detector.
> > >
> > > 2. The reactor core may not be known precisely. Has anyone written a realistic model for the source? How do we define the "center of the core."
> > >
> > > 3. If we can define the core centers and draw a line between them, we would like to know the axis of symmetry, which would presumably be perpendicular to this line. The axis of symmetry could be defined as the intersection of the vertical and horizontal planes of symmetry, if they exist. Because we are dealing with extended sources, the vertical and horizontal planes of symmetry might not the orthoginal to each other.
> > >
> > > These will be small effects, but we should probably keep them in mind as we go along. I'm especially interested in knowing a bit more about the size and distribution of the reactor core.
> > >
> > > Cheers,
> > >
> > > Ray Stefanski
> > > Fermilab, MS122
> > > P.O. Box 500
> > > Batavia, Il 60510
> > > Phone: 630.8403872
> > >
> > > ----- Original Message -----
> > > From: "Bolton, Tim" <bolton@phys.ksu.edu>
> > > Date: Wednesday, December 22, 2004 8:16 am
> > > Subject: RE: coordinate system
> > >
> > > > Precisely. After talking with Glenn and Josh and looking at what
> > > > KAMLAND and SNO did, I think a more
> > > > sensible choice might be:
> > > >
> > > > z-axis -- plumb-line up, or zenith angle 0. Our liquid always
> > > > measures this.
> > > >
> > > > xy-plane is perpindicular to z.
> > > >
> > > > x-axis (phi=0) -- draw a line from the midpoint of the two
> > > > reactor cores to the center of the upstream near detector (if
> > > > there are two, then to the one most likely to be fixed. Project
> > > > the line to the xy-plane.
> > > >
> > > >
> > > > y = z X x.
> > > >
> > > > This way the z-axis is the one about which the detector has
> > > > rotational symmetry. The beam is mostly along the x axis with a
> > > > small -z component and a y component that typically averages to
> > > > zero. The x and y axes will also be approximate symmetry axes for
> > > > the cavern and veto structures.
> > > >
> > > > TB
> > > >
> > > >
> > > > Tim Bolton
> > > > Professor
> > > > High Energy Physics Group
> > > > Kansas State University
> > > > tbolton@ksu.edu
> > > > 785-532-1664
> > > >
> > > >
> > > >
> > > > -----Original Message-----
> > > > From: Jonathan Link [link@fnal.gov]
> > > > Sent: Tue 12/21/2004 10:52 PM
> > > > To: Bolton, Tim
> > > > Cc: reactor-vwg@mit.edu
> > > > Subject: Re: coordinate system
> > > >
> > > > Which beam? Reactor one or reactor two?
> > > >
> > > > Bolton, Tim wrote:
> > > >
> > > > >I'm not sure we have even made a basic convention for the
> > > > coordinate system.
> > > > >
> > > > >ReactorFsim tacitly assumes
> > > > >
> > > > >z = "beam direction", with z increasing as one moves away from
> > > > reactor.
> > > > >
> > > > >y = "up"
> > > > >
> > > > >x = y X z
> > > > >
> > > > >And x and y don't really matter.
> > > > >
> > > > >But there are subtleties.
> > > > >
> > > > >-- Where is x=y=z=0? Center of one detector (which one).
> > > > Midpoint between two reactor cores? Ed's office?
> > > > >
> > > > >-- Can we assume that all detectors are centered on the z-axis.
> > > > >
> > > > >-- y is not really "up" in this convention, because of "beam
> > > > tilt". Should it be "up" as in vertical or "up as perpindicular
> > > > to beam?
> > > > >
> > > > >Maybe there is a better choice. We should make it before we
> > > > start introducing elements that define direction.
> > > > >
> > > > >TB
> > > > >
> > > > >
> > > > >
> > > > >
> > > > >Tim Bolton
> > > > >Professor
> > > > >High Energy Physics Group
> > > > >Kansas State University
> > > > >tbolton@ksu.edu
> > > > >785-532-1664
> > > > >
> > > > >
> > > > >
> > > > >-----Original Message-----
> > > > >From: ELog@CYCLOTRON.mit.edu [ELog@CYCLOTRON.mit.edu]
> > > > >Sent: Tue 12/21/2004 9:26 AM
> > > > >To: reactor-vwg@MIT.EDU
> > > > >Subject: New ELOG entry
> > > > >
> > > > >A new entry has been submitted on cyclo.mit.edu
> > > > >
> > > > >Logbook : Veto Working Group
> > > > >Author : Peter Fisher
> > > > >Type : Agenda
> > > > >Category : General
> > > > >Subject : Short phone meeting Tuesday, 3:30 pm, 617-
> > > > 324-7520
> > > > >
> > > > >Logbook URL : http://cyclo.mit.edu:8080/Veto+Working+Group/6
> > > > >
> > > > >=================================
> > > > >
> > > > >Please note the meeting will start a half hour later than usual.
> > > > >
> > > > >Agenda
> > > > >------
> > > > >
> > > > >1. Nomenclature and general veto configurations - 10'
> > > > > At the last meeting with discussed some general configurations
> > > > for the
> > > > >veto simulation. I've made some simple sketches which are on the
> > > > E-log.
> > > > >I'm happy to change any label to be consistant with history, but
> > > > we should
> > > > >agree on what we call things.
> > > > >
> > > > >2. Simulation progress and plans - 15'
> > > > > Work has begun on flux functions for ReactorFsim and ther are
> > > > >opprotunities for people to contribute. We should briefly review
> > > > what is
> > > > >being done.
> > > > >
> > > > >The next meeting will be Jan. 4, 2004.
> > > > >
> > > > >Peter
> > > > >
> > > > >
> > > > >
> > > > >
> > > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > >
>
Received on Sat Dec 25 16:11:58 2004