sPHENIX is a new detector at RHIC.

[Marzia Rosati <marziarosati AT gmail.com>]

Craig and sPHENIX list,
since this is a general interest question I am responding to the list.

The plot I sent to Gunther was generated with Pythia Upsilon(1S) 
particles decaying into dielectrons, so the Upsilon and electrons have a 
realistic pt distribution and account for the decay kinematics.

I made simple acceptance cuts on the two electrons from Upsilon decays 
as stated in the legend: |eta|<1, |eta|<0.85, |eta|<0.6. The reduced eta 
coverage implies a Upsilon signal loss of 24% for |eta|<0.85 and 59% 
loss for |eta|<0.6, relative to eta<1.

If the actual detector coverage is different than what stated in the 
Figures, I can easily generate new numbers but those were the eta values 
requested by Gunther and Dave. I assume the |eta|<0.72 coverage will 
imply an acceptance loss very close to the half way value in between the 
0.6 and 0.85 values i.e.  40-45% loss.

If I follow your logic, I assume the 0.6 descoping scenario would result 
in slightly different coverage too. I can generate new plots if needed 
we just have to settle on the detector plans and actual coverage for 
various descoping scenario first....

Best regards
Marzia

On 11/6/17 6:11 AM, Craig Woody wrote:
> Hi Marzia,
>    I was looking at the descoping document that they turned in and there 
> is something in there that bothers me. It says we need to cut down the 
> EMCAL acceptance from eta = 1.1 to eta = 0.85 and that this would lead 
> to a reduction of 25% in upsilon statistics (see p.6), which I presume 
> is based on the plot you made shown in Fig. 2.4 . I know the 0.85 number 
> came from Ed who just scaled the total cost of the EMCAL to save the 
> $1.1M that was needed to get within the budget limit. I did a more 
> accurate estimate by looking at the items we could actually cut, keeping 
> the fixed costs the same, and I came with a number of 0.82. This was 
> surprisingly close to the scaling estimate, but the 0.82 (which is 
> probably more like 0.8 in reality) needs to have a fiducial cut applied 
> for doing any sort of physics analysis, since we can't measure right to 
> the edge of the detector. That's why the baseline design goes out to eta 
> =1.1 in order to measure within eta = 1.0. Therefore, you need to reduce 
> the 0.82 to 0.72 when comparing to the statistics that we would measure 
> out to eta = 1.0. If you look at Fig 2.4 in the descoping document, the 
> loss in statistics for this is clearly more than 25%. Take Pt = 4 GeV 
> for the upsilon, and the acceptance for eta = 1 is about 0.32. It looks 
> like the acceptance for eta ~ 0.7 would be about 0.17, which would give 
> a ratio to eta = 1.0 of 0.53, or almost 50% loss in statistics. This 
> ratio is more or less constant across the Pt spectrum, so it's pretty 
> clear to me that we're going to loose a lot more than 25% in upsilon 
> statistics. Am I missing something here, or do these losses seem to be 
> underestimated ?
>
> Thanks,
> Craig
>
> P.S. I'm also copying Jin on this in case he has any comments.
>
>
>
> On 10/23/2017 8:57 PM, Marzia Rosati wrote:
> > Gunther et al.,
> > attached is a the upsilon efficiency vs pt for all 3 eta ranges to be 
> > used as the right hand side plot in figure 1.4.
> >
> > I am not sure what is meant by line 124-126. "While these losses are 
> > not catastrophic, it is worth noting that within the sPHENIX run plan 
> > a 25% loss is equal to the statistics collected in one of the RHIC run 
> > periods".
> >
> > As far as I understand this statement is not correct. The acceptance 
> > in PHENIX is about 18 times smaller than sPHENIX so we our stats are 
> > much smaller. STAR has a similar acceptance to sPHENIX but readout 
> > much slower and limited PiD so I don't think they ever collected 
> > upsilon samples in any beam species (pp AuAu) which are 1/4 of the 
> > expected sPHENIX stats.
> >
> > Best regards
> > Marzia
> >
> > On 10/23/17 5:54 PM, Gunther M Roland wrote:
> > > A friendly reminder that comments on this important document are 
> > > still being accepted! Thanks to everyone who shared their 
> > > thoughts/corrections already. We will work on an updated draft 
> > > tomorrow and then take it from there.
> > >
> > > Best,
> > >
> > > Gunther and Dave
> > >
> > > > On Oct 21, 2017, at 12:02 AM, Gunther M Roland <rolandg AT mit.edu> wrote:
> > > >
> > > >
> > > > Friends,
> > > >
> > > > As discussed at the General Meeting today, we are forwarding draft 1 
> > > > of our document outlining the detector scope for a $32M cost cap. 
> > > > The pdf file can be found at
> > > > https://www.dropbox.com/s/5wyutbndogozm5q/sPH-GEN-2017-002_v1.pdf?dl=0
> > > > (we'll provide another link tomorrow for those that can't access 
> > > > dropbox)
> > > >
> > > > Please send your comments in reply to this mail, keeping the 
> > > > [sPH-GEN-2017-002] tag in the subject line***. Comments received by 
> > > > close-of-business on Monday, 10/23, will be most useful.
> > > >
> > > > Cheers,
> > > >
> > > > Gunther and Dave
> > > >
> > > > ***we will move future reviews to an sphenix-notes-l AT bnl.gov list, 
> > > > but the list couldn't be generated in time for this note.
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