[esa-t474] Your submission (fwd)

[Yury Kolomensky]

I would agree with Eric. We can add a paragraph describing the impact  
of beam energy measurement and other techniques to determine the  
spectrum that help turn this into a physics tool. There is a sentence  
and a reference now; expanding this to a paragraph would be  
sufficient. I think we can safely claim that no other measurement can  
compete with precision. In the letter to the editor, we can point out  
that this is the paper about instrumentation, not a physics  
publication, so more detailed discussion is beyond the current scope.  
It is even beyond the scope of the next paper.

Yury

On Dec 19, 2007, at 7:59 AM, Eric Torrence wrote:

> Hi Stewart,
>
>    I would try to argue to the editor and reviewer that
> the topic of this paper is a measurement of beam energy.
> The reviewer is correct in saying that there are other
> issues regarding the use of this device in the ILC to
> measure root(s) spectrum, but this is not the topic of
> the current work.
>
>    This is NIM after all.  When people write papers on
> drift chambers, they don't explain in detail what kind
> of physics measurements they are going to do with them.
>
>    I would think that one intro paragraph (at most)
> discussing these issues in the broadest terms should be
> adequate.
>
> Regards,
> -Eric
>
> On Dec 18, 2007, at 2:42 PM, stewart boogert wrote:
>
>> Dear Eric, Mark and T474,
>>
>> The reviewers comments are quite interesting and all quite beyond the
>> scope of the paper, which is principally machine physics.
>>
>> 1) The peak of the spectrum is the most important feature with  
>> regards the
>> physics program. The luminosity spectrum at the collision point  
>> bounded at the
>> top by the spectrometer measurement. In fact for M_t and M_h this  
>> is the most important
>> feature. The effect of the luminosity spectrum is convoluted with  
>> the threshold structure
>> being investigated, so the large energy loss beamstrahlung events  
>> are suppressed and
>> only the peak really contributes.
>>
>> 2) Absolutely no physics measurement (particle flow, or even more  
>> exotic for
>> any physics process ) can provide a precision energy measurement  
>> at any
>> reasonable time scale. It is possible to measure the beam energy  
>> using
>> radiative returns to the Z but this analysis is incomplete and  
>> provides energy
>> measurements at similar frequencies to physics rate.
>>
>> 3) The measurement of Bhabha scattering can provide information on
>> the momentum imbalance between the two colliding beams on a more  
>> rapid time
>> scale, but this method as formulated in all treatments does not  
>> reconstruct the collision
>> centre of mass energy, only the fractional energy loss from the  
>> maximum beam energy.
>> Of course then one requires the energy spread of the machine too.  
>> From Bhabhas the momentum
>> mismatch between the beams \Delta p can be measured not what p  
>> actually is.
>>
>> 4) I would think that more important comments are that the energy  
>> loss from the measurement
>> location and just before collision are more important as it is  
>> quite difficult to measure this
>> effect. Bino is simulating now, but we do not yet know the answer.
>>
>> I can definitely add come text to the paper to this effect if the  
>> reviewer agrees.
>> There is little published in this area, something Eric. Mike and I  
>> have been trying
>> to correct for a while but without success.
>>
>> I'll add a little more text to Mike's paragraph in a few hours and  
>> send around.
>>
>> Cheers,
>> Stew
>>
>>
>> On 14 Dec 2007, at 18:02, 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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>>>
>>>
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>
>
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