sPHENIX is a new detector at RHIC.

[Gunther M Roland <rolandg AT mit.edu>]

Hi Marzia et al,

For the present purpose (i.e., the discussion we had with Berndt and as an 
answer to one of the Director's review questions) the current generator level 
plots are fine. I don't think refining these particular estimates, both in 
terms of cost and of exact percentage of statistics loss, is highest priority 
at the moment. To avoid confusion, I also want to add that there is no |eta| 
< 0.6 scenario being discussed at this point. As we stated in the document, 
and repeated in the DOE meeting (and DOE understood), final baselining will 
happen at the CD-2/CD-3b step - May 2019, if things go well.

Best,

Gunther


> On Nov 6, 2017, at 8:58 PM, Marzia Rosati <marziarosati AT gmail.com> wrote:
> 
> 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.
>>>>> _______________________________________________
>>>>> sPHENIX-l mailing list
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>>>> 
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