Subject: Paper on Fast Monopoles
From: Ivan De Mitri (ivan.demitri@le.infn.it)
Date: Thu Mar 08 2001 - 04:15:26 EST
Dear Erik,
here you can find the answers to all of your
questions/comments to the fast monopole paper.
You will find attached 2 figures (see below).
Let us know.
....Waiting for a prompt reply,
Ivan & Fausto
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> I remain rather purplexed from your statement that you can
> not provide the numbers on the effects of your various cuts
> of the analysis. You mentioned that this analysis is going to
> analyze the remainder of the MACRO data, so even if these
> numbers were not kept in a compact form at the time the proposed
> analysis was carried out, it must be rather straightforward
> to reproduce it. Being a technical paper, I feel, the effects
> of the various cuts on the background rejection is a very important
> piece of information- people who might be reading this paper
> and designing new experiments will probably look for these
> numbers.
The analysis goes throught the following steps:
(a) run selection (run legth > 0.5h and absence of evident hw problems)
(b) event selection (trigger)
(c) event reconstruction (in the ST and in the SC)
(d) cut on dE > 150 MeV
(e) cut on the ST charge
(f) possible scanning of CR39
The informaion about (a) is given by the live time.
Information about (b) and (c) are given in the efficiency and acceptance
evaluations.
The step (d) reduces the number of events to ~10^3/yr.
The step (e) reduces the number of events to ~3/yr.
Therefore, once an event has been reconstructed, the background rejection
is made by just 2 cuts. Their effect is given above.
The effects of the various "micro-cuts" during the event reconstruction
are integrated in the efficiency evaluation, fully discussed in the paper.
What is difficult for us to provide is the effect of each single micro-cut
during event reconstruction. Of course this is not technically impossible, but
it would require energies that we do not have now.
Obviuosly in the past each step has been checked to work properly with the
maximum care, but we do not have now all the number for all the micro-cuts.
We do not think that this is really needed in the paper.
The important information for those who might be designing new experiments are
are given above.
The effect of each single micro-cut in the event reconstruction is not reported
in the other macro technical papers on monopoles.
It is not done even the the neutrino papers (where to give this information
might be much more important) or in those on muons.
So we think that adding the information on (d) and (e) is what you are asking for.
Also remember that the numbers on some micro-cuts are given in the paper in the
reconstruction sections. See for example fig.1, fig.15 (or fig.2 that you
proposed to cut since it refers to calibrations [see below] and we substantially
agree with you)
....
> My proposal to you is to eliminate any discussion on the calibrations-
> let it be done properly in the technical paper.
Ok, this is one possibility. Since you asked for the source file
you may also put, as you suggested, this section in a good shape.
....
> The only thing that I would actually keep out of the entire
> calibration discussion
> is the dE/dx plot and the Landau fit that you had in your
> original draft but not in this one. I think this is a key plot
> that should be re-inserted (after you correct the axis and give
> more info on the fit).
This plot did not have any fit , even in its first version.
You are right as far as the axis is concerned. Probably
(by mistake) (de/dx)*rho is plotted instead of (de/dx)/rho.
We have such a plot in the correct form (see attachment).
The peak is located at 1.8 MeV/cm as it should be.
However we do not think that this plot is really necessary
in the paper, once the discussion on energy calibration is
done properly in the technical paper.
We leave such decision to the editorial board.
.....
> Back on the dE/dx vs. beta point: I think the paper cries for
> a plot like that when you write at the end of p.13 "the measured
> values of energy loss and beta of surviving candidates have been
> compared with the expected monopole signal as a function
> of its velocity..." What can be drawn from a plot like that
> is how close to the monopole curve the point lies especially
> after showing their errors on energy which could potentially
> justify their checking on the CR39.
We did not include this plot in the paper because the final cut of the analysis
is the scanning of the CR-39.
This is possible as a consequence of the very low number of events/yr
which are left.
We do not want the final cut of our analysis to be the cut in the dL/dx vs beta
plot. We do not need. The use of this cut might have the drawback on dE/dx
that we were referring to during the last macro-rare wg (dE/dx vs dE cuts).
However, since, we have this tool ready for use, we cited it in the paper.
We can put the plot but , it should be remebered that this is just for a
redundant check. We leave such decision to the editorial board.
In attachment you can find the dL/dx vs beta plot for the events that
have been scanned in CR39. Remember that only 3 of them survive the cuts
while the other 3 just are very close to the cut curve.
Out of these 6 events one has two boxes selected in the analysis
so the beta can be evaluated.
For the other 5 events the beta reconstructed by ST is reported.
Remember that the ST resolution on ToF is greater than 100% above 2*10^-2.
Therefore beta for these candidates is > 2*10^-3. This is sufficient
as you can see from the plot.
The dE values for these events are around 180MeV. Therefore the error
on the Y axis is essentially dictated from the energy resolution at that
level. This is very small compared to the distance to the monopole
curve.
As you can see all the candidates are well below the expected monopole
light yield, even taking into account of the famous factor 2.
.....
> You are concerned about the size of the paper and so am I.
> I think there is a number of plots that can easily be removed
> without any impact on the significance of the paper- these are:
> 1) ERP ADC vs Light Output (fig 3) -- already shown in ref.
> not relevant for this search
> 2) Efficiency vs Scintillator ID number (fig 9) -- too detailed
> 3) Fig 10 fraction of scint wiwth e>0.95
> 4) Fig 2 - that makes part of the calibration discussion
> 5) Fig 11 - too technical
The editorial board can decide to cut them out. The risk is to cut out
all the stuff concerning the scintillator. Remember that this is a
combined analysis
....
> Some disconnected comments and
> questions that came up at the second reading of the paper:
> Fig. 1 is the Streamer Tube position in this figured obtained
> from fast or slow tracking?
This is obtained by the use of the slow tracking, i.e. the same that
it is used in the whole analysis. See the
section concerning event reconstruction in the ST.
....
> If you analyze any further ERP data
> or re-analyze any past data, please make sure you use the new ERP
> constants.
We already produced calibrated dst's for the whole data sample.
....
> If you provide me with the source tex file I can
> work on shaping the scintillator calibrations section together
> with direct editing of some phrasing/english suggestions that
> I have or I can fax you the pages.
Ok. We will send you the .tex file
> PS: I think you should still look items #3,4,6 of my September note where
> there are minor discrepancies that need to be corrected.
We already gave you answers to your questions (see below).
Please tell us what are your problems with them.
_________________________________________
EK wrote:
3) section 3.2 (end of p.5 beginning of p.6): a connection is made here between
the average PMT pulse width (50ns) to the fact that saturation effects will
start for pulses from particles traveling in a counter for more than 135ns.
This is not obvious to me-- would you like to elaborate? The instrinsic PMT
response is rather irrelevant for pulses lasting more than this.
(4) section 3.2 (top of p.6),derivation of the 470MeV energy deposition of a
5x10^-3 beta monopole. If x30Imin is the rate of energy deposition then for
20cm I come up with something of the order of 1GeV-- am I missing something
here (energy loss vs. scintillation light- I believe we are always talking
about scintillation light here)?
(6) section 5.3 (p.11) derivation of minimum E through eqn 4: a 1.8 MeV/(gr/cm2)
value is used for Imin which is then multiplied by the scintillator density.
I guess this is another mystery number for MACRO. In the ERP energy
calibration code the muon peak is fixed at 1.8 MeV/cm (notice the
difference in units with what you are using). Now, being this a rather
critical issue in our analyses, over the last few months, Charlie Peck at
Caltech has performed a detailed derivation of the energy loss of CR muons
in MACRO using as realistic counter folding as possible based on all-time
ERP calibrations. The result will appear in the ERP energy calibration
section of the technical papers (1.8 MeV/cm is your number though.)
Answers:
3) The 60ns is somehow a measurement of the signal fall time
(the box crossing time for muons is of course irrelevent).
For slower particles the pulse duration should be equal to
the box crossing time + the signal fall time.
Given that, we think that the text is pretty clear.
4) You obtain ~ 1GeV since you do not take into account the
factor two uncertanty quoted in the Ahlen-Tarle' paper.
Therefore in the worst case, which is what has to be
considered in estimating the analysis efficiency, one must
take into account this factor 2 (--> ~470 MeV).
6) As far as eq.4 is concerned you can take the (dE/dx)min from
the PDG by considering the energy loss of muons in carbon
at the minimum of the Bethe-Block curve (1.8 MeV/gcm2).
If we take the de/dx of muons with energy equal to the
average energy of the atmospheric muons we have in MACRO
(i.e. ~ 200 GeV) we opbtain ~ 2.1-2.2 MeV/gcm2 which
is compatible (throught the ~ 0.87g/cm3 density of the scint.)
with the 1.8 MeV/cm.
We agree with you that we have to fix this number.
This numbers can be put in the paper once we agree on that.
In practice this has no consequence on the analysis, since
going from 1.8MeV/gcm2 to 2.1MeV/gcm2 even raise the efficiency
of the 150 MeV cut.
______________________________________________________________________
> If you have a postscript version of your 1997 related MACRO/MEMO
> I'll be glad to read it through. Or if you fax it to me at
> 001 617 253 7014.
We will send you the .ps file
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