[esa-t474] Proposed corrections

[Woods, Michael B.]

Hi Mark, should remove the word "upstream" in sentence "...in addition to this upstream energy measurement".  For the bhabha reference, suggest to also include 
Questions about the measurement of the e+ e- luminosity spectrum at a future linear collider, Stewart T. Boogert, David J. Millee; 2002. e-Print: hep-ex/0211021.
I think should give a little more explanation as well about the lumi spectrum which might satisfy the editor's comment on PFAs and physics analyses.  

Suggest something like following wording:

"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 physics analysis are particularly sensitive to the collision energy:  threshold cross-section measurements and reconstruction of particle resonances \cite{ref:theory_measurements}.  The goals for accurate mass determinations in these analyses require the fractional error on the incoming beam energy be better than $10^{-4}$. An additional complication for physics analyses is that the colliding particles can emit initial state radiation (ISR) or beamsstrahlung, resulting in a luminosity spectrum for the center-of-mass collision energy.  The luminosity spectrum is peaked at the sum of the incident electron and positron beam energies but has a long low energy tail.  In principle, ISR effects can be calculated but beamsstrahlung effects depend sensitively on the collision parameters and need to be
determined experimentally.~\cite{ref:instr_reqs}   The luminosity spectrum will be extracted using energy spectrometers and measurements of the acolinearity angle distribution in Bhabha events, a full discussion of which is beyond the scope of this paper~\cite{ref:bhabha}.  To measure the incoming energy to the required accuracy and to minimise the disruption of the beam, a magnetic spectrometer has been proposed."  

Cheers, mike
 

-----Original Message-----
From: Mark Slater [mailto:slater at hep.phy.cam.ac.uk] 
Sent: Monday, December 17, 2007 4:54 AM
To: esa-t474 at hep.ucl.ac.uk
Subject: [esa-t474] Proposed corrections

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
> > 
> > 
> > _______________________________________________
> > esa-t474 mailing list
> > esa-t474 at hep.ucl.ac.uk
> > https://mail.hep.ucl.ac.uk/mailman/listinfo/esa-t474
> > 
> 
> 

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