[esa-t474] Proposed corrections

[Mark Slater]

Dear all,

Following the editors comments, here are my proposed changes to the 
starting paragraph of the introduction:

The physics potential of the International Linear Collider (ILC) depends
greatly on precise energy measurements of the electron and positron beams
at the interaction point (IP). Two types of analysis are particularly
sensitive to the collision energy:  threshold cross-section measurement
and reconstruction of particle resonances \cite{ref:theory_measurements}.
The required accuracy for the mass measurements dictate that the
fractional error on the determination of the incoming beam energy must be
better than $10^{-4}$. To fully reconstruct particle resonances, studies
of beam-beam effects such as beamstrahlung have shown that knowledge of
the luminosity spectrum to $1\%$ is also required in addition to this
upstream energy measurement~\cite{ref:instr_reqs}. To measure the
luminosity spectrum, it is planned to use the acolinearity of Bhabha
scattered events, a discussion of which is beyond the scope of this
paper~\cite{ref:bhabha}. However, an absolute energy measurement is still
essential to the proposed physics progamme. To measure the incoming energy
to the required accuracy and to minimise the disruption of the beam, a
magnetic spectrometer has been proposed.


with:

\bibitem{ref:instr_reqs}
D.~Cinebro, E.~Torrence, M.~Woods, %{Status of Linear Collider Beam 
Instrument
%Design},
URL http://www.slac.stanford.edu/xorg/lcd/ipbi/notes/white.pdf (2003).

\bibitem{ref:bhabha}
M.~N.~Frary, D.~J.~Miller, %{Monitoring the Luminosity Spectrum},
DESY-92-123A (1991) 379



I wasn't sure what to include in the comments to the editor about the
PFAs, etc. as my knowldege of these is practically zero. Does anyone have
any ideas? As far as I know, with the measurment of the luminosity
spectrum from bhabha scatterin, the resonances and thresholds can be
extracted without the need for anything more. Is this correct? If so,
shall I just say that in the comments?

Any suggestions/corrections more than welcome!

Thanks,

Mark




On Fri, 14 Dec 2007, Eric Torrence wrote:

> Hi Mark,
> 
>    I think Mike has already given some good pointers
> on this, but just to reiterate it should be clearly
> stated that measuring the mean beam energy before
> collisions is a necessary (but certainly not sufficient)
> part of determining the collision spectrum needed for
> the ILC program.  For both direct reconstruction like
> M_H and threshold scans like M_t, the peak of the
> spectrum is the most important feature.  There are
> plenty of corrections, including energy loss in magnets
> and beamstrahlung, which need to be applied, but without
> a calibrated mean beam energy measurement you have no hope.
> 
> Regards,
> -Eric
> 
> On Dec 14, 2007, at 3:18 AM, Mark Slater wrote:
> 
> > Dear All,
> > 
> > Here are the first comments from the reviewer. Does anyone have a good
> > answer to this?
> > 
> > Thanks,
> > 
> > Mark
> > 
> > ---------- Forwarded message ----------
> > Date: Thu, 13 Dec 2007 21:08:00 -0000
> > From: nim at lbl.gov
> > To: slater at hep.phy.cam.ac.uk
> > Subject: Your submission
> > 
> > Nuclear Inst. and Methods in Physics Research, A
> > Title: Cavity BPM System Tests for the ILC Energy Spectrometer
> > 
> > Dear Dr. Slater,
> > 
> > Thank you for your recent submission to Nuclear Inst. and Methods in
> > Physics Research, A.
> > 
> > Before proceeding further with the review process, I would like you to
> > address in detail the following issue.  Beamstahlung will spread the
> > energy of the electrons and positrons at the collision point by an amount
> > far greater than the precision of the instrument that you propose. Indeed,
> > for the purposes of data analysis new approaches, such as particle flow
> > analysis, must be developed because one cannot balance momentum in the
> > beam direction. Your treatment of this issue should speak to how the
> > information from the proposed instrument would be used as an input to the
> > new physics analysis approaches.
> > 
> > Sincerely,
> > 
> > William A. Barletta
> > Editor
> > Nuclear Inst. and Methods in Physics Research, A
> > 
> > 
> > _______________________________________________
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> > 
> 
>