Fwd: [Bispud-pipeline-list] Toy model for negative TQ - Bicep2-list

12 Mar 2013

Chao-Lin

----- Forwarded Message -----
From: "Chao-Lin Kuo" &lt;clkuo(a)stanford.edu&gt;
To: "John Kovac" &lt;jmkovac(a)cfa.harvard.edu&gt;
Cc: "bispud-pipeline-list" &lt;bispud-pipeline-list(a)lists.fas.harvard.edu&gt;
Sent: Friday, March 8, 2013 10:45:32 PM
Subject: Re: [Bispud-pipeline-list] Toy model for negative TQ

The toy model should obviously be replaced by the more appropriate 
radiation transfer analysis in this paper. But just to set the 
record straight the model now looks like the attached cartoon. 

The original one had two sign errors (that cancel) and one spelling 
error. 

Chao-Lin

----- Original Message -----
...

 This is the Italian paper we made reference to on the telecon today.

 http://www.sat.ltu.se/members/viju/publication/cmb/mnr_11464.pdf

 I remain skeptical that this effect could produce a signal that
 evades
 temporal jackknives, but I strongly encourage people to think about
 it.

 Regardless, this could be the explanation for the large-scale average
 polarization signal that appears to align with the prevailing wind.
 Exploring this signal in B1, B2, and Keck could certainly be
 scientifically interesting (i.e. eventually publishable) on its own
 merits, even if it isn't the problem we're dealing with in B2.

 J

 On 3/5/13 6:39 PM, Chao-Lin Kuo wrote:
   Negative
TQ seems strong and convincing to me. Like I said in
 the telecon I don't think it is consistent with ground screen
 reflections
 though. The sky signal reflected into the telescope is not visible
 to
 the main beam so why would there be any correlation, positive or
 negative?  Ok, If the reflected signal generates T , which is then polarized
 by the ground screen, that could generate a TQ. Sarah is reading
 through Denis' thesis to see whether this has the right sign.

  However if a big blob of cloud at low elevation
intercepts the
 far side lobe, it could introduce both a T signal and a Q signal
 that
 would be anti-correlated. See the attached cartoon.

 This can also break the positive-negative symmetry: most clouds
 have
 crystals align vertically. So there is no fluctuation to 'cancel'
 the
 negative correlation.

 Looking at

 http://bmode.caltech.edu/~spuder/analysis_logbook/analysis/20130304_azmaps/

 section 3, we know the negative correlation isn't perfect though,
 before
 ground subtraction.

 Chao-Lin

 <TQ_from_cloud.gif>
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 ___________________________________________________________________
    John Kovac                             jmkovac(a)cfa.harvard.edu

    Assistant Professor, Astronomy and Physics, Harvard University
    160 Concord Ave rm 310, Cambridge MA 02138, 617-496-0611

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