feat(mixing): add OneBB1500W preset and 1BB1500W beam constants

[oksuzian]

Adds a one-booster-batch beam preset at 1500 W, and the Run1B constants it
derives from.

Why

The mixing presets cover full 1BB (1.58e7 protons/spill), full 2BB (3.93e7) and
1% of a single batch pulse (1.58e5). Run1B runs one booster batch at reduced
intensity, which is none of these, so every Run1B campaign has carried a bare
extendedMean override in its prodtools entry with no record of where the
number came from. Reconstructing it took a full pass through the accelerator
parameters.

The derivation

Protons per spill is POT per cycle divided by the number of 1695 ns spills that
fit in the onspill fraction of a cycle:

mode	power	POT/cycle / (DF × cycle / SPILL)	= protons/spill
1BB1500W	1.500 kW	1.556e12 / (0.323 × 1.33 / 1.695e-6)	6.141e6
1BB	3.855 kW	4e12 / (0.323 × 1.33 / 1.695e-6)	1.578e7
2BB	7.324 kW	8e12 / (0.246 × 1.40 / 1.695e-6)	3.937e7

This reproduces the two existing presets to their quoted precision, which is
what establishes that the relation is the right one. It also explains why 1BB
and 2BB are not a factor of two apart in protons per spill despite being a
factor of two in protons: 2BB delivers double the protons in a shorter spill,
0.344 s against 0.430 s. Power depends on POT/cycle and cycle time only — the
duty factor cancels.

cutMax follows the 6× convention of the other presets. OneBB1500W.fcl
includes OneBB.fcl rather than restating SDF, so the lognormal width stays
defined in one place and the file does not depend on include order.

Normalisation gap, documented but not closed

ensemble/python/constants.py carried only 1BB and 2BB. Normalising Run1B with
run_mode='1BB' assumes 1.58e7 protons/spill where the campaigns actually mix
5.92e6 — an overestimate of POT by 2.7×.

This PR adds ONEBB1500W_DF, ONEBB1500W_CYCLE, ONEBB1500W_POT_PER_CYCLE
and ONEBB1500W_PROTONS_PER_SPILL — named for the beam rather than the
campaign, following ONEBB_/TWOBB_, with '1BB1500W' as the natural run mode
string — but does not wire them in: get_duty_factor() and get_pot()
still branch on '1BB' and '2BB' only, so this normalisation continues to
require the custom method. Making it a first-class run mode touches four
branch sites across two functions and is better reviewed on its own. Worth
folding into that change: get_duty_factor() currently fails open, returning
the 1BB duty factor for any unrecognised mode with its warning commented out,
while get_pot() raises.

Effect on existing jobs

None. No existing fcl or campaign entry includes the new file, and nothing reads
the new constants. Verified: all three modes reproduce their stated
protons-per-spill from the constants as imported (Run1B −0.010%, 1BB −0.111%,
2BB +0.185%; the two existing figures are the rounded values the presets use).

[FNALbuild]

Hi @oksuzian,
You have proposed changes to files in these packages:

• JobConfig

which require these tests: build.

@Mu2e/write, @Mu2e/fnalbuild-users have access to CI actions on main.

⌛ The following tests have been triggered for c591efd: build (Build queue - API unavailable)

About FNALbuild. Code review on Mu2e/Offline.

[FNALbuild]

☀️ The build tests passed at c591efd.

Test	Result	Details
test with	✅	Command did not list any other PRs to include
merge	✅	Merged c591efd at bfa5e6c
build (prof)	✅	Log file. Build time: 04 min 20 sec
ceSimReco	✅	Log file.
g4test_03MT	✅	Log file.
transportOnly	✅	Log file.
POT	✅	Log file.
g4study	✅	Log file.
cosmicSimReco	✅	Log file.
cosmicOffSpill	✅	Log file.
ceSteps	✅	Log file.
ceDigi	✅	Log file.
muDauSteps	✅	Log file.
ceMix	✅	Log file.
rootOverlaps	✅	Log file.
g4surfaceCheck	✅	Log file.
FIXME, TODO	✅	TODO (0) FIXME (0) in 0 files
clang-tidy	✅	0 errors 0 warnings

N.B. These results were obtained from a build of this Pull Request at c591efd after being merged into the base branch at bfa5e6c.

For more information, please check the job page here.
Build artifacts are deleted after 5 days. If this is not desired, select Keep this build forever on the job page.

[oksuzian]

@FNALbuild run build test

[FNALbuild]

⌛ The following tests have been triggered for 947cccd: build (Build queue - API unavailable)

[FNALbuild]

☀️ The build tests passed at 947cccd.

Test	Result	Details
test with	✅	Command did not list any other PRs to include
merge	✅	Merged 947cccd at bfa5e6c
build (prof)	✅	Log file. Build time: 04 min 21 sec
ceSimReco	✅	Log file.
g4test_03MT	✅	Log file.
transportOnly	✅	Log file.
POT	✅	Log file.
g4study	✅	Log file.
cosmicSimReco	✅	Log file.
cosmicOffSpill	✅	Log file.
ceSteps	✅	Log file.
ceDigi	✅	Log file.
muDauSteps	✅	Log file.
ceMix	✅	Log file.
rootOverlaps	✅	Log file.
g4surfaceCheck	✅	Log file.
FIXME, TODO	✅	TODO (0) FIXME (0) in 0 files
clang-tidy	✅	0 errors 0 warnings

N.B. These results were obtained from a build of this Pull Request at 947cccd after being merged into the base branch at bfa5e6c.

For more information, please check the job page here.
Build artifacts are deleted after 5 days. If this is not desired, select Keep this build forever on the job page.

[michaelmackenzie]

Looks good to me, thanks!

[sophiemiddleton]

looks good