LHC Lumi Days 2025

10 Mar 2025, 11:30 → 12 Mar 2025, 18:00 Europe/Zurich

774/R-013 (CERN)

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

Monday 10 March

14:00 → 15:30 Luminosity determination in Run III, and associated uncertainties

Convener: Eric Torrence (University of Oregon (US))

14:00 Welcome – workshop program, goals and scope

Speaker: David Stickland (Princeton University (US))

14:10 Overview of ATLAS luminosity determination

Overview of ATLAS luminosity-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:
- calibration strategy: vdM, LSC, calibration-transfer / non-
linearity corrections, instrumental corrections, ...
- 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

Speaker: Brian Andrew Cole (Columbia University (US))

14:50 Overview of CMS luminosity determination

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

• Global view of
- calibration strategy: vdM, LSC, calibration-transfer / non-
linearity corrections, instrumental corrections, ...
- 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

Speaker: Gabriella Pasztor (Eötvös University, Budapest)

15:30 → 16:00 Tea/Coffee

16:00 → 17:40 Luminosity determination in Run III, and associated uncertainties

Convener: Gabriella Pasztor (Eötvös University, Budapest)

16:10 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

Speaker: Martino Gagliardi (Universita e INFN Torino (IT))

16:45 ALICE final Run-II luminosity measurements

Speaker: Prof. Jesus Guillermo Contreras Nuno (Czech Technical University in Prague (CZ))

17:05 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

Tuesday 11 March

09:00 → 10:30 Impact of beam dynamics on vdM calibrations

09:00 Overview of the accelerator issues that impact the absolute luminosity calibrations at the LHC

Speaker: Witold Kozanecki (University of Oregon (US))

09:40 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 Results of the 2024 Non-factorization MD: accelerator measurements

10:30 → 11:00 Tea/Coffee

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

Convener: Witold Kozanecki (University of Oregon (US))

11:00 LHCb non-factorization analyses

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

11:30 CMS non-factorization analyses

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

Speaker: Peter Major (University of Maryland (US))

12:00 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

14:00 → 15:30 Impact of beam dynamics on vdM calibrations

14:00 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

Speaker: Witold Kozanecki (University of Oregon (US))

14:35 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

15:05 Generalization of parameterized beam-beam corrections to 2-D vdM scans

Speaker: Ivan Kralik (Slovak Academy of Sciences (SK))

15:30 → 16:00 Tea/Coffee

16:00 → 17:35 Impact of accelerator instrumental issues on luminosity calibrations

Convener: Manuel Gonzalez Berges (CERN)

16:00 Tune measurements in vdM fills, before and during collisions

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

Speaker: Tom Levens (CERN)

16:20 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))

16:50 LHCb ghost-charge measurements

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

17:05 Follow-up questions and iscussion

Moderated by W. Kozanecki

Wednesday 12 March

09:00 → 11:35 Impact of accelerator instrumental issues on luminosity calibrations

Convener: David Stickland (Princeton University (US))

09:00 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

Speaker: Richard Hawkings (CERN)

09:35 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?

Speaker: Dr Marek Gasior (CERN)

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

Speaker: Vladislav Balagura (Centre National de la Recherche Scientifique (FR))

10:30 Coffee

11:00 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 → 12:35 Luminometer non-linearities and integration uncertainties

Convener: Martino Gagliardi (Universita e INFN Torino (IT))

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

Speaker: David Stickland (Princeton University (US))

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

Speaker: Francesco Romeo (Vanderbilt University)

14:00 → 14:35 Luminometer non-linearities and integration uncertainties

Convener: Martino Gagliardi (Universita e INFN Torino (IT))

14:00 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

Speaker: Giulia Ripellino (Uppsala University (SE))

14:35 → 15:35 What can we do better in the remainder of Run III, and looking to Run 4

Convener: Richard Hawkings (CERN)

14:35 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)

15:10 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

15:35 → 16:00 Tea/Coffee

16:00 → 17:30 What can we do better in the remainder of Run III, and looking to Run 4

Convener: Richard Hawkings (CERN)

16:00 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

16:20 Looking to Run 4: ATLAS Run-3 experience with LUCID prototypes for HL- LHC

Speaker: Vincent Hedberg

16:50 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)

Speaker: Alexey Shevelev (University of Maryland (US))

17:20 Discussion and Closeout