sPHENIX is a new detector at RHIC.

[David Morrison <morrison AT bnl.gov>]

Dear BUP enthusiasts!

Here are my comments on the nice BUP draft.

Dave

5: "twenty years with new" - "twenty years, and it will bring new"
7: "Long Range Plan, and the" - "Long Range Plan.  The"

15: "The effort to construct the experiment is officially underway
with the DOE Major Item of Equipment (MIE) project having been granted
PD-2/3 approval in September 2019." - "The DOE Major Item of Equipment
(MIE) project was granted PD-2/3 approval in September 2019."

18: "These are funded as Brookhaven National Laboratory capital
projects (e.g., the micro-vertex detector, MVTX), or realized as
contributions from collaborating institutions (e.g., the intermediate
silicon strip tracker, INTT)." - "These are funded as Brookhaven
National Laboratory capital projects (e.g., the micro-vertex detector,
MVTX), realized as contributions from collaborating institutions
(e.g., the intermediate silicon strip tracker, INTT), or via NSF
funding (the event plane detector, sEPD)."

67: CD-1/3a -> CD-1/3A (capital)

173 "Fudan University" - "Fudan University, Peking University, and
CIAE"

Section 1.4.5: An opportunity to mention that we'll be using STAR's
HFT beampipe.

199: "providing an extra space point" - "providing, for tracks in
select fraction of the acceptance, a space point at a known location"

216: Could be useful to clarify that "10%-str" means that the readout
is fully capable of streaming the tracking detectors, but that we're
limited to allocating 10% of the bandwidth to streaming readout by
storage considerations.

253ff: "However, the new guidance suggests a moderate (up to 20%)
potential reduction in the expected p+p luminosity in 2024
running. Given the short time frame, the projections in this BUP were
not able to be updated to account for the decreased p+p baseline. A
qualitative way to understand the impact would be increase the
statistical uncertainty by 10% on all measurements which use the full
sampled p+p luminosity (jets, photons, Upsilons). However, many
measurements would also become increasingly sensitive to uncertainties
where large statistics are needed to study systematic effects in data
(e.g. isolated track-to-calorimeter matching for inter-detector energy
calibration, γ+jet calibration of the energy scale in p+p) in a way
that is difficult to quantify quickly."

I'd avoid seeming apologetic, and I'd highlight the potential impact
of the reduced guidance in an additional way.  How about:

"The recent C-AD guidance contains a reduction (~ 20%) in the expected
p+p luminosity in 2024 running relative to previous guidance.  The
quantitative projections in this BUP continue to be based on the the
previous guidance.  However, a rough estimate of the impact of the
decreased luminosity guidace would be to increase the statistical
uncertainty by 10% on all measurements which use the full sampled p+p
luminosity (jets, photons, Upsilons).  Other measurements would become
increasingly sensitive to uncertainties where large statistics are
needed to study systematic effects in data (e.g. isolated
track-to-calorimeter matching for inter-detector energy calibration,
γ+jet calibration of the energy scale in p+p) in a way that is
difficult to quantify quickly.  We note that in the 2021 BUP, the
collaboration chose to eliminate p+Au running entirely in the 20
cryo-week scenario (a 20% reduction from the 24 cro-week scenario) to
preserve sufficient run time to accumulate needed p+p reference
statistics."

353: "multiplicities conditions." - "multiplicity conditions."

Figure 4.2 caption: "balance, xJfl," - "balance, xJγ,"

Appendix D: might note that plan for 2026-2027 was requested by
then-ALD Berndt Mueller in 2017.  IOW, we didn't make it up.

--
David Morrison  Brookhaven National Laboratory  phone: 631-344-5840
                Physics Department, Bldg 510 C    fax: 631-344-3253
                          Upton, NY 11973-5000  email: dave AT bnl.gov