LHC Lumi Days 2025

Mar 10, 2025, 11:30 AM → Mar 12, 2025, 6:00 PM Europe/Zurich

774/R-013 (CERN)

David Stickland (Princeton University (US)), Witold Kozanecki (University of Oregon (US))

Mon, March 10

2:00 PM → 3:30 PM Luminosity determination in Run III, and associated uncertainties

2:00 PM Welcome – workshop program, goals and scope

2:10 PM Overview of ATLAS L-determination

Overview of ATLAS L-determination methodology in
Run III, and comparison to Run-II methodology (both pp and HI)
Introduction to common vdM [avoid duplication in next talk!]
• Global view of
o calibration strategy: vdM, LSC, calibration-transfer / non-
linearity corrections, instrumental corrections, ...
o long-term monitoring strategy, conceptual definition of CT +
LTS systematic uncertainties
• Description of calibration procedures (vdM scans, LSC,
calibration-transfer, instrumental corrections) & associated systs
• What was achieved; key issues

2:50 PM Overview of CMS L-determination

Overview of CMS L-determination methodology in
Run III, and comparison to Run-II methodology (both pp and HI)

• Global view of
o calibration strategy: vdM, LSC, calibration-transfer / non-
linearity corrections, instrumental corrections, ...
o long-term monitoring strategy, conceptual definition of CT +
LTS systematic uncertainties
• Description of calibration procedures (vdM scans, LSC,
calibration-transfer, instrumental corrections) & associated systs
• What was achieved; key issues

3:30 PM → 4:00 PM Tea/Coffee

4:00 PM → 5:40 PM Luminosity determination in Run III, and associated uncertainties

4:10 PM HI-specific vdM-calibration issues (ALICE Speaker)

For instance: fitting procedures with challenging scan shapes;
dealing with low-statistics in scan tails; BCID-dependent satellite
corrections; satellite collisions; NF corrections; use of ZDC as
high-statistics L monitor
Include HI-specific contributions from ATLAS & CMS

4:45 PM ALICE final Run-II luminosity measurements

5:05 PM LHCb methods & techniques for L measurements in pp collisions

• Reminder of what was used in Run II, and main results
• brief intro to the new LHCb luminometers in Run III
• possibly some preliminary results for LHCb Run-III luminosity

Tue, March 11

9:00 AM → 10:30 AM Impact of beam dynamics on vdM calibrations

9:00 AM Overview of the accelerator issues that impact the absolute luminosity calibrations at the LHC

9:40 AM Sources & mitigation of non-factorization in the injectors & the LHC

• mechanisms of generating non-factorization in the proton-density
distributions, and its transport through the injector chain
• optimized beam preparation for vdM beams — how to optimize
factorization already before the vdM fill (e.g. scraping
measurements in LHC at injection to confirm factorization, further
optimization of beam production schemes in the injectors
• collimation in the LHC?

Speaker: Foteini Asvesta (CERN)

10:10 AM Results of the 2024 Non-factorization MD: accelerator measurements

10:30 AM → 11:00 AM Tea/Coffee

11:00 AM → 12:30 PM Impact of beam dynamics on vdM calibrations

11:00 AM LHCb non-factorization analyses

• 2-D vdM analysis
• LHCb BGI results from the NF MD

11:30 AM CMS non-factorization analyses

• 2-D vdM, beam-beam imaging and LRE analyses
• Including CMS results from the NF MD?

12:00 PM ATLAS non-factorization analyses

• 2-D vdM and LRE analyses
• Including ATLAS results from the NF MD?
• Include some ALICE LRE results if so requested

2:00 PM → 3:30 PM Impact of beam dynamics on vdM calibrations: Impact of beam dynamics on L calibrations

2:00 PM Summary of beam-beam simulation studies during LS2

Summary of the beam-beam papers, with the emphasis on
(i) bb-related vdM uncertainties as currently understood, and
(ii) pending issues

2:35 PM Recent developments in beam-beam studies

For instance:
• Results of the 2022 beam-beam MD
• New simulation results on Lu/L0 ambiguity
• Interplay between beam-beam & non-factorization biases

Speaker: Joanna Wanczyk

3:05 PM Generalization of parameterized beam-beam corrections to 2-D vdM scans

3:30 PM → 4:00 PM Tea/Coffee

4:00 PM → 5:35 PM Impact of accelerator instrumental issues on L calibrations

4:00 PM Tune measurements in vdM fills, before and during collisions

• incl. BBQ post-processing updates, tune-uncertainty definition,
possibility of using ADT for bbb tunes

4:20 PM LHC bunch-population measurements in Run III & beyond: a status report

• DCCT, FBCT, BSRL: performance, issues, new developments.
• also: BPTX @ IP1 & IP5, w/ applicable functionalities; BQM
• also: 1-2 slides on planned HL-LHC upgrades of the beam
instrumentation relevant to bunch-current measurements?

Speaker: Alexander Nicholas Jury (University of Liverpool (GB))

4:50 PM LHCb ghost-charge measurements

• Run-III results and performance to date
• brief mention of plans for further improvements

5:05 PM Discussion

Wed, March 12

9:00 AM → 11:35 AM Impact of accelerator instrumental issues on L calibrations

9:00 AM Impact of magnetic non-linearities, BPM performance & x-y coupling on ATLAS length-scale calibrations

• including the systematic. uncertainties associated w/ DOROS-
BPM performance limitations, e.g. non-reproducibility of the
BPM length scale, their response to beam-beam deflections and
their apparent out-of-plane coupling

9:35 AM Status report on LHC beam-position measurements at the experimental IPs

• DOROS BPMs: improvements since the start of Run III,
performance, known limitations & issues
• Brief comments about Arc BPMS in the context of orbit-drift
monitoring?

10:00 AM BPM- and BGI-based beam-displacement measurements at IP8

10:30 AM Coffee

11:00 AM Emittance evolution in physics and luminosity-calibration fills: what S. Kostoglou +10 measurements do we have and what did we learn from them?

Speaker: Sofia Kostoglou (CERN)

11:35 AM → 12:35 PM Luminometer non-linearities and integration uncertainties

11:35 AM What have the Experiments learnt from emittance scans, and what can we do better?

Speaker: David Stickland (Princeton University (US))

12:00 PM Luminometer non-linearity corrections and integration uncertainties in CMS

2:00 PM → 2:35 PM Luminometer non-linearities and integration uncertainties

2:00 PM Calibration-transfer and long-term stability in ATLAS: corrections & systematic uncertainties.

Examples of corrections that could be mentioned:
• LUCID HV adjustments based on Bi calibrations
• LUCID non-linearity correction using track-counting-based L
Examples of systematics that could be discussed:
• CT uncertainty (from TILE/tracks)
• Anchoring uncertainty
• Long-term stability & consistency uncertainty

2:35 PM → 3:35 PM What can we do better in the remainder of Run III, and looking to Run 4

2:35 PM Use of reference physics processes for long-term relative-stability monitoring

For instance:
• in pp: Z-, but also J/psi- & Upsilon- counting
• in PbPb: UPC dimuons (CMS)
• in PbPb: photonuclear signatures in the ZDCs

Speaker: David Walter (CERN)

3:10 PM New LHCb luminometers in Run III

what has LHCB learnt from PLUME (and other luminometers) in
Run III, and how it informs the LHCb strategy for Run 4

3:35 PM → 4:00 PM Tea/Coffee

4:00 PM → 5:30 PM What can we do better in the remainder of Run III, and looking to Run 4

4:00 PM First experience with the ALICE FIT system as an online luminometer

experience with FIT in Run 3, and how it informs the ALICE
strategy for Run 4

4:20 PM Looking to Run 4: ATLAS Run-3 experience with LUCID prototypes for HL- LHC

4:50 PM Looking to Run 4 in CMS

For instance (under consideration; not an exhaustive list):
• experience with BCM1F in Run 3, and how it informs the CMS
strategy for Run 4
• proposal for very-high µ (µ > 120) fill with a mixture of indivs &
trains (as done in 2016) for characterizing the BCID-dependent
response, and the relative µ-dependence, of the CMS
luminometers (also of interest to ATLAS)
• scouting
• outer-tracker potential for L monitoring in Run 4 (simulation
results)

5:20 PM Discussion and Closeout