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Re: [Sphenix-l] Question about upsilon statistics in descoping document

From: Anthony Frawley <afrawley AT fsu.edu>
To: Marzia Rosati <marziarosati AT gmail.com>, Craig Woody <woody AT bnl.gov>
Cc: "sphenix-l AT lists.bnl.gov" <sphenix-l AT lists.bnl.gov>
Subject: Re: [Sphenix-l] Question about upsilon statistics in descoping document
Date: Tue, 7 Nov 2017 02:32:12 +0000

Hello Craig,

If I did the arithmetic correctly, the difference between eta values of 0.82 and 0.72 at a radius of 90 cm is about 12 cm (reduction of 82.35 cm to 70.55 cm in the positive Z direction). Is there really that large an unusable strip at the edge of the CEMC?

Thanks

Tony

From: sPHENIX-l <sphenix-l-bounces AT lists.bnl.gov> on behalf of Marzia Rosati <marziarosati AT gmail.com>
Sent: Monday, November 6, 2017 8:58 PM
To: Craig Woody
Cc: sphenix-l AT lists.bnl.gov
Subject: Re: [Sphenix-l] Question about upsilon statistics in descoping document

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://urldefense.proofpoint.com/v2/url?u=https-3A__www.dropbox.com_s_5wyutbndogozm5q_sPH-2DGEN-2D2017-2D002-5Fv1.pdf-3Fdl-3D0&d=DwIGaQ&c=HPMtquzZjKY31rtkyGRFnQ&r=O5IMywjiKCp6dNXW0Blu_Q&m=dAtQl10U-VVI4qIq1cZR9SqfSaie9weexvFXTuLd4II&s=EjkVyJ3_MjUVb2JOYCmuKhHLS_h2XlBvYK4eRca_ZV8&e=

sPH-GEN-2017-002_v1.pdf

urldefense.proofpoint.com

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Re: [Sphenix-l] Question about upsilon statistics in descoping document, Marzia Rosati, 11/06/2017
- Re: [Sphenix-l] Question about upsilon statistics in descoping document, Anthony Frawley, 11/06/2017
- Re: [Sphenix-l] Question about upsilon statistics in descoping document, Gunther M Roland, 11/06/2017
- Re: [Sphenix-l] Question about upsilon statistics in descoping document, Craig Woody, 11/07/2017
  - Re: [Sphenix-l] Question about upsilon statistics in descoping document, Anthony Frawley, 11/07/2017
    - Re: [Sphenix-l] Question about upsilon statistics in descoping document, Marzia Rosati, 11/07/2017
      - Re: [Sphenix-l] Question about upsilon statistics in descoping document, Craig Woody, 11/07/2017