CMS Precision EWK Workshop: Open Symposium on W mass

2 Mar 2026, 08:00 → 3 Mar 2026, 18:30 Europe/Zurich

Main Auditorium ("Le Benedettine" Conference Center, Pisa)

Ankita Mehta (CERN), Chiara Aime' (Universita & INFN Pisa (IT)), Christoph Paus (Massachusetts Inst. of Technology (US)), Jan Eysermans (Massachusetts Inst. of Technology (US)), Josh Bendavid (CERN), Kenneth Long (Massachusetts Inst. of Technology (US)), Lorenzo Bianchini (Universita & INFN Pisa (IT)), Marco Cipriani (Universita & INFN Pisa (IT)), Yurii Maravin (Kansas State University (US))

This workshop will focus on the EWK precision physics program pursued by the CMS Collaboration. It is the first event of this kind after the CMS mW Hackathon at MIT. It comes about one year after the announcement of the first CMS mW measurement. Since then, the scope of our physics program has enlarged: the goal of this workshop is to review and discuss progress in this fruitful and evolving field. 

The Open Symposium on W mass is an introductory event to the CMS Workshop where prominent experts in the field will be invited to discuss crucial apsects of past, present, and future measurements of the W boson mass, one of the key targets of the CMS EWK precision program.

This event will also represent a conclusive symposium for the ERC-funded project ASYMOW, which has given an important contribution to the success of the CMS measurement.

The Symposium will be followed by a closed session restricted to members of the CMS Collaboration. Note that a separate indico page has been created for the latter event. 

Invited speakers are selected based on their expertise in the field. Only plenaries sessions. No fees for registration (financial support will be provided by local organizing committee).

Confirmed speakers:

• A. Bacchetta (Università & INFN Pavia ) 
• J. Bendavid (CERN)
• M. Boonekamp (Université Paris-Saclay)
• L. Buonocore (CERN)
• T. Cridge (University of Manchester)
• R. Franceschini (Università Roma Tre)
• C. Hays (University of Oxford)
• K. Long (CNRS)
• C. Paus (MIT)
• A. Pinto (LPNHE)
• R. Poncelet (IFJ PAN Krakow)
• L. Rottoli (Università & INFN Milano-Bicocca)
• L. Silvestrini (INFN Roma)
• M. Vesterinen (University of Warwick)
• M. Wiesemann (Max Plank Institute for Physics)
• G. Wilson (University of Kansas)

group_picture.jpg

Poster.pdf

Monday 2 March

08:30 Registration

1 Welcome and Opening by Local Organizers

Speaker: Lorenzo Bianchini (Universita & INFN Pisa (IT))

CMSWorkshop_introduction.pdf

2 mW in ATLAS : past results, ongoing work and future projects

Speaker: Maarten Boonekamp (Université Paris-Saclay (FR))

mw_pisa_02032026.pdf

3 W boson mass measurements with the LHCb experiment

In this talk I will present LHCb’s measurement of the W boson mass using forward W decays in the muon channel, highlighting the unique features of the LHCb approach and its complementarity to ATLAS and CMS. I will discuss the main experimental and theoretical uncertainties and outline prospects for future improvements.

Speaker: Mika Anton Vesterinen (University of Warwick (GB))

2026_March_Pisa_workshop.pdf

10:40 Coffee break

4 The CDF W mass measurement and considerations for reanalysis

I will review the CDF W mass measurement, which is a significant outlier with respect to other measurements, while also being the most precise. As such it merits additional scrunity, and I will discuss aspects of the measurement that could be revisited as part of a reanalysis. I will focus largely on the measurement of the charged-particle momentum in the outer tracker, but will also discuss a few broader and more general avenues for pursuit.

Speaker: Chris Hays (University of Oxford (GB))

Pisa2026.pdf

5 High-precision measurement of the W boson mass with the CMS detector

Particle masses and the coupling strengths of the forces are fundamentally experimental parameters that must be measured and input into the standard model of particle physics (SM). While the SM does not predict their values, it does predict precise relationships between them. Physics beyond the standard model can change these relationships, making it of paramount importance to measure these parameters with the highest possible precision. While the mass of the Z boson is known to the remarkable precision of 22 parts per million, the W boson mass is known much less precisely. Furthermore, the most precise measurement of the W boson mass, performed by the CDF Collaboration at Fermilab in 2022, is in significant tension with the standard model expectation from indirect measurements. Recently, the CMS Collaboration at the LHC has performed its first measurement of the W boson mass. The measurement is based on a highly granular maximum likelihood fit performed with a sample of W boson events decaying to a muon and a neutrino. The significant in situ constraints of theoretical inputs and their corresponding uncertainties provided by this novel approach, together with an accurate determination of the experimental effects, lead to a very precise W boson mass measurement, 80360.2 ± 9.9 MeV. The result is in agreement with the standard model prediction and in disagreement with the measurement of the CDF Collaboration. I will discuss the measurement procedure and the experimental and theoretical advancements that enabled this striking result.

Speaker: Kenneth Long (Massachusetts Inst. of Technology (US))

2026_03_Long_CMSmW_Pisa.pdf

12:20 Lunch

6 The W-Boson Mass: Current Measurements and World Average

Speaker: Andres Pinto (Centre National de la Recherche Scientifique (FR))

AP_CMSPrecisionEWKWorkshop_20260302.pdf

7 Precision PDFs and their uncertainties

PDFs are a critical theoretical input for precision measurements at the LHC, including for electroweak physics and Standard Model parameter determinations, where percent-level accuracy is required to fully exploit LHC data. Key Standard Model parameters determined at the LHC are now fundamentally limited by the PDFs and their uncertainties, from the W boson mass to the weak mixing angle. Achieving robust precision therefore demands consistent treatments of the PDFs and their uncertainties. I will summarise the current status of PDFs for precision LHC physics in this context, focusing on the challenges and considerations required. I will also outline ongoing work on this and present its impacts on Standard Model parameter extraction.

Speaker: Thomas Cridge (DESY)

TCridge_PDFs_for_precision_PISA.pdf

8 Quark transverse-momentum effects and the W mass

I will discuss how the nonperturbative components of the quark transverse-momentum distributions (TMDs) can affect the determination of the W mass and emphasize the importance of a taking them into account when quantifying M_W uncertainties.

Speakers: Prof. Alessandro Bacchetta, Alessandro Bacchetta

PISA_CMS_MW_Bacchetta_new.pdf

15:45 Coffee break

9 Drell-Yan Lepton Pair Production in the High-Precision Era

The pursuit of high-precision predictions for Drell-Yan processes at hadron colliders has driven substantial theoretical advancements in recent years. Experiments aim for increasingly accurate determinations of Standard Model parameters such as the weak mixing angle, the strong coupling and the W-boson mass. Central to this progress is the incorporation of higher-order QCD and electroweak corrections within fiducial phase-space regions relevant to LHC analyses. NNLO QCD predictions are now available through multiple public codes, whose reliability is crucial to achieve the precision demanded by experimental measurements. Achieving N3LO accuracy for fiducial observables, matched with next-to-next-to-next-to-leading logarithmic (N3LL) resummation, has established a new benchmark in theoretical precision, reducing uncertainties to the percent level. In this talk, I will discuss recent progress toward a fully consistent, high-accuracy description of Drell-Yan pair production that will underpin current and future precision measurements at hadron colliders.

Speaker: Luca Rottoli (Universita & INFN, Milano-Bicocca (IT))

rottoli_resummation_CMS@PISA_2026.pdf

10 Higher-Order Event Generators for Precision Electroweak Physics

I will present recent progress in precision simulations for electroweak processes at the LHC, with a focus on event generation at NNLO accuracy matched to parton showers. After reviewing the main theoretical approaches and currently available tools, I will discuss their relevance for electroweak precision studies, in particular for Drell–Yan production. I will also highlight recent developments in electroweak production in association with heavy quarks. Finally, I will outline ongoing and future directions aimed at further improving higher-order Monte Carlo simulations, including the incorporation of electroweak corrections, more accurate parton showers, and matching at third order in perturbation theory.

Speaker: Marius Wiesemann (Max Planck Institute for Physics)

Wiesemann_CMS_EWK_Precision_Workshop_on_mW.pdf

19:30 Social Dinner

The social dinner will be offered to all registered participants at the roof-top restaurant of Grand Hotel Duomo.

Tuesday 3 March

11 Electroweak and Mixed QCD–Electroweak Effects in Precision Drell–Yan Measurements at the LHC

Precision measurements of Drell–Yan production at the LHC are essential for extracting electroweak parameters, parton distribution functions, and the strong coupling constant. As experimental uncertainties reach the per-mille level for many normalized observables, theoretical uncertainties become dominant, making subleading radiative effects increasingly relevant. This talk discusses electroweak and mixed QCD–electroweak corrections and their impact on the LHC precision physics program.

Speaker: Luca Buonocore (CERN)

PISA_EW-QCD-LB.pdf

12 Uncertainties from missing higher orders for precision measurements (ONLINE)

Precision computations for standard candle processes are a staple of the physics programme at colliders such as the Large Hadron Collider, and the highest precision can be achieved in perturbative computations. In perturbation theory, however, calculations truncated at a fixed (logarithmic) order inevitably have inherent theoretical uncertainty. Traditionally, scale variation has been employed to estimate this uncertainty. In this talk, I discuss prescriptions for directly incorporating these missing higher-order terms via Theory Nuisance Parameters and their application to electroweak precision measurements.

Speaker: Rene Poncelet (IFJ PAN Krakow)

2026.03.03-CMS-wmass-workshop-poncelet.pdf

10:10 Coffee break

13 MW and global fits in the SM and beyond

We briefly review the role of MW in global fits in the SM and in its extensions, including Oblique NP and the SMEFT.

Speaker: Luca Silvestrini (INFN, Rome)

MW.pdf

14 Lepton collider measurement prospects for mW

I will discuss some of the measurement techniques for mW that can be
available at future lepton colliders referring as appropriate to methods
used already at LEP. Key aspects are related to center-of-mass energy and
background control, understanding of hadronization, 4-fermion effects,
and tracker momentum and hadronic mass scales. The utility of longitudinally polarized beams and e-gamma based measurements will be emphasized, and recent work towards using light mesons with well-known daughter masses for tracker momentum scale determination will be presented.

Speaker: Graham Wilson (The University of Kansas (US))

Wmass_Pisa_GWW_V1.pdf

15 Looking ahead: ideas and plans for the Summer

Speaker: Christoph Paus (Massachusetts Inst. of Technology (US))

ewk-future.pdf

12:20 Picture Time

12:30 Lunch

16 An experimentalist perspective on mW

Speaker: Josh Bendavid (CERN)

mWPisaDiscussion.pdf

17 A light new physics perspective on mW

Speaker: Roberto Franceschini (Rome 3 U.)

Franceschini - A light BSM perspective on W boson mass.pdf

18 Concluding remarks

Speaker: Lorenzo Bianchini (Universita & INFN Pisa (IT))

16:10 Coffe break