MWDays23 workshop

17 Apr 2023, 08:50 → 20 Apr 2023, 21:00 Europe/Zurich

4/3-006 - TH Conference Room (CERN)

Emanuele Angelo Bagnaschi (INFN Laboratori Nazionali di Frascati)

After about one year from the release of the new $M_W$ determination from CDF, the MWDays23 workshop would like to give the opportunity to the community to  gather together in order to discuss and summarize the outcome of the recent developments related to the MW determination, and the implications of $M_W$ for BSM physics. We plan to discuss the experimental determination at hadron colliders (with an outlook to e+e- colliders and related challenges), the theory elements related to the experimental effort, the prediction of MW in the SM, the SMEFT interpretation of the measured values, and the MW prediction in explicit BSM models. One day will be assigned to each topic. 

The workshop will be held in person (if you are interested in registering for remote attendance, please contact Emanuele Bagnaschi -- emanuele.bagnaschi@cern.ch).

Confirmed speakers:

• M. Boonekamp (ATLAS, MW combination working group)
• D. Froidevaux (ATLAS, LHC Electroweak working group)
• J. Bendavid (CMS)
• S. Camarda (ATLAS)
• C. Hays / A. Kotwal (CDF)
• M. Ramos Pernas (LHCb)
• G. Wilson (future $e^+e^-$ colliders)
• L. Cieri (SM theory)
• S. Dittmaier (SM theory)
• W. Hollik (SM theory)
• A. Huss (SM theory)
• T. Neumann (SM theory)
• A. Vicini (SM theory)
• P. Nadolsky (PDF)
• M. Ubiali (PDF)
• L. Silvestrini (SM/SMEFT EW fits)
• K. Mimasu (SMEFT global fits)
• J. Erler (PDG)
• G. Arcadi (BSM)
• J. Braathen (BSM)
• C.-W Chiang (BSM)
• A. Crivellin (BSM)
• J. Evans (BSM)
• R. Pasechnik (BSM)
• F. Sannino (BSM)

 

Organizing committee

• E. Bagnaschi (CERN/INFN Laboratori Nazionali di Frascati, LOC)
• P. Monni (CERN, LOC)
• P. Giardino (IGFAE)
• S. Heinemeyer (IFT Madrid)
• D. Wackeroth (U. Buffalo)
• G. Weiglein (DESY)

Monday, 17 April

1 A couple of words from the organizing committee

Speaker: Emanuele Angelo Bagnaschi (INFN Laboratori Nazionali di Frascati)

LOC-MWDays23.pdf

2 High-precision measurement of the W boson mass with the CDF II detector (30' talk + 30' discussion)

The mass of the W boson, a mediator of the weak force between elementary particles, is tightly constrained by the symmetries of the standard model of particle physics. The Higgs boson was the last missing component of the model. After observation of the Higgs boson, a measurement of the W boson mass provides a stringent test of the model. We measure the W boson mass, MW, using data corresponding to 8.8 inverse femtobarns of integrated luminosity collected in proton-antiproton collisions at a 1.96 TeV center-of-mass energy with the CDF II detector at the Fermilab Tevatron collider. A sample of approximately 4 million W boson candidates is used to obtain MW=80,433.5±6.4stat±6.9syst=80,433.5±9.4 MeV/c2, the precision of which exceeds that of all previous measurements combined. This measurement is in significant tension with the standard model expectation.

Speaker: Ashutosh Kotwal (Duke University (US))

AshutoshKotwal-MwDays23-17April23.pdf

3 ATLAS measurement of mW (30' talk + 30' discussion)

This talk will review the ATLAS measurement of the W-boson mass, with an emphasis on the recent reanalysis of 7 TeV data, and on the uncertainties due to the modelling of the vector boson production and decay.

Speaker: Stefano Camarda (CERN)

atlasmw.pdf

11:00 Coffee break

4 Precision W Boson Measurements at CMS (30' talk + 30' discussion)

Precision measurements of W Boson production are of great interest in improving understanding of the proton structure, and as a precursor to measurements of the W mass. Measurements of differential and polarized W production cross sections will be discussed, including implications for improving knowledge of the proton PDF. Preliminary studies of experimental aspects of W mass measurements using Z events as a proxy
will also be discussed.

Speaker: Josh Bendavid (Massachusetts Inst. of Technology (US))

Precision W Measurements in CMS.pdf

12:30 Lunch

5 Towards a full Run 2 W mass measurement at LHCb (30' talk + 30' discussion)

With the analysis of 2016 data provided by the LHC, the LHCb Collaboration demonstrated its capability in a measurement of the W boson mass. By including data collected in 2017 and 2018, the statistical precision will be improved by roughly a factor of two. Many efforts are being put in-place in order to reduce both the experimental and theoretical systematic uncertainties via a more detailed study of the detector effects and the modelling of the W boson production at the LHC.

The LHCb Collaboration is currently analyzing all the data collected in the Run 2 (2016-2018) of the LHC following a more careful treatment of the curvature biases and detector efficiencies, as well as exploring the most recent developments in the event generators and parton distribution functions (PDFs). The measurement of the W mass at LHCb is particularly interesting due to the anti-correlation of the PDF uncertainties with respect to ATLAS and CMS, since it provides a complementary coverage in pseudorapidity.

A combination of all the measurements at the LHC will allow to achieve a sensitivity closer to the global EW fit, and help to clarify the picture around the W boson mass after the most recent results.

Speaker: Miguel Ramos Pernas (University of Warwick (GB))

Miguel_Ramos_Pernas-Towards_a_full_Run_2_W_mass_measurement_at_LHCb.pdf

6 MW combination working group (30' talk)

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

mWdays_170423.pdf

7 Experimental and theoretical uncertainties related to W mass measurement at hadron colliders: CDF/ATLAS/LHCb (30' talk)

This talk will attempt to summarise the main issues related to achieving a 10-15 MeV precision on a W mass measurement at hadron colliders today. These cover crucial experimental aspects (muon momentum scale, hadronic recoil, pile-up) and also physics modelling issues, mostly related to the theoretical knowledge of pTW/pTZ in a region where resummation, heavy flavour, and non-perturbative contributions matter more than fixed-order perturbative calculations.

Speaker: Daniel Froidevaux (CERN)

mWuncertainties_17042023_v2.pdf

16:00 Coffee break

8 Discussion session of the previous two talks (45' discussion)

Speakers: Daniel Froidevaux (CERN), Maarten Boonekamp (Université Paris-Saclay (FR))

Tuesday, 18 April

9 Precision QCD predictions for the Drell-Yan process (30' talk + 20' discussion)

The calculation of fixed-order predictions at the third perturbative order (N3LO) in the NNLOJET framework is presented, as well predictions further matched to transverse momentum resummation at N3LL with the RadISH framework. A focus will be paced on the phenomenological impact of these corrections, the associated theory uncertainties, and the computational challenges.

Speaker: Alexander Yohei Huss (CERN)

MWDays_Huss.pdf

10 Precise QCD resummed predictions for the Drell-Yan process (30' talk + 20' discussion)

In this talk we will present selected QCD resummed predictions for the Drell-Yan process. In particular, the recent N4LL QCD calculation will be discussed and also the QCD+QED NLL results will be presented.

Speaker: Leandro Cieri

Lcieri-MWDays23.pdf

10:40 Coffee break

11 High-precision measurements of the Z-boson transverse momentum and $\alpha_s$ with the ATLAS experiment [EP seminar -- we move to the council chamber]

This seminar presents a precise measurement of the production properties of the Z-boson in the full phase space of the decay leptons, based on 8 TeV pp collision data collected by the ATLAS experiment in 2012. The double-differential cross-section distributions in Z-boson transverse momentum and rapidity are measured in the pole region. In a novel approach, the measured Z transverse momentum is used to determine the strong coupling constant. The analysis uses state-of-the-art predictions at third order accuracy in perturbative QCD, supplemented by resummation of logarithmically-enhanced contributions in the small transverse-momentum region of the lepton pairs. The extracted $\alpha_s(m_Z)$ result is the most precise single measurement to date.

See also https://indico.cern.ch/event/1231802/ .

Speaker: Stefano Camarda (CERN)

12:00 Lunch

12 DY QCD predictions at $\alpha_s^3$ with CuTe-MCFM & LHC EWWG activity overview (30' talk + 30' discussion)

High-precision DY predictions are a crucial ingredient in current W-boson mass analyses. I present predictions at the level of $\alpha_s^3$ at fixed-order and including transverse-momentum resummation and put them in the context of remaining effects that need to be included at that level of precision. I will propose steps towards bringing the baseline modeling of the W-mass analyses from alphas to $\alpha_s^3$.

In a second part I give a brief overview of the activities of the LHC EWWG, where various groups benchmark DY transverse-momentum resummation and push developments towards more precise DY modeling.

Speaker: Tobias Neumann

Neumann_Tobias_MWDays.pdf

Talk (HTML)

13 MW determination at hadron colliders (30' talk + 30' discussion)

I will review the traditional approach for the determination of the W boson mass at hadron colliders from the kinematical distributions of the charged-current Drell-Yan process. I will then present a new observable which allows this determination, with the possibility of a simple discussion and estimate of the associated QCD uncertainties.

Speaker: Alessandro Vicini (Università degli Studi e INFN Milano (IT))

Vicini-MW-asymmetry.pdf

14 Electroweak Corrections to W/Z Resonances (30' talk + 30' discussion)

The calculation of radiative corrections to resonance processes poses issues with gauge invariance owing to the necessary mix of perturbative orders after some Dyson summation of the potentially resonant propagator corrections. The talk reviews various schemes proposed to cure this problem and quantifies the corresponding theory uncertainties in the evaluation of electroweak corrections to Drell-Yan-like W/Z production. NLO electroweak corrections to W/Z production are also discussed for some scenarios of physics beyond the Standard Model such as a singlet Higgs extension, the Two-Higgs-Doublet Model, and the Minimal Supersymmetric Standard Model.

Speaker: Stefan Dittmaier (Albert Ludwigs Universitaet Freiburg (DE))

mwdays23.pdf

16:30 Coffe break

15 Robust PDF determination for precise electroweak measurements (30' talk + 30' discussion)

The determination of Parton Distribution Functions (PDFs) is a crucial theoretical input for precise electroweak measurements at hadron colliders, in particular for the W mass measurements at the LHC. In this talk, I will describe the methodological advances in modern PDF determinations, with a particular focus on NNPDF. I will then mention new interesting challenges that modern fits of PDFs face at the precision frontier, in which it is crucial to assess the robustness of the uncertainties associated with the theory predictions.

Speaker: Maria Ubiali

Ubiali_MWdays.pdf

16 Quantification of the epistemic PDF uncertainty and CTEQ-TEA update (30' talk + 30' discussion)

How well do we know the inner structure of protons? The answer depends not only on the precision of experimental measurements and theoretical predictions but, as was pointed out recently, on the procedure of sampling of the allowed PDF solutions over the multidimensional parameter space. With large data samples, phenomenological PDF fits are at a risk of the big-data paradox, which takes over the law of large numbers and implies that more experimental data do not automatically raise the accuracy of PDFs. Close attention to the data quality and sampling of possible PDF solutions is as essential, as well as the distinction between aleatory and epistemic uncertainties. I will summarize efforts in the CTEQ-TEA group to understand and reduce all such PDF uncertainties and provide independent methods to validate PDF uncertainty estimates in precision EW measurements.

Speaker: Prof. Pavel Nadolsky (Southern Methodist University)

n418.pdf

17 Social dinner in Geneva

For those who have expressed interest, we have reserved a place for us at the "Le Gruyérien - Plainpalais" at 20.30.

Restaurant Le Gruyérien
Boulevard de Saint-Georges 65
1205 Genève
Tél. +41 22 320 81 84
https://www.le-gruyerien.ch/gruyerien/plainpalais/

https://goo.gl/maps/HJizqEXBDF9nQd9w6

Wednesday, 19 April

18 Prospects for Precision mW Measurements at Future e+e- Colliders (30' talk + 30' discussion)

This talk will give an overview of the prospects for future e+e- colliders to make incisive measurements of the W mass with techniques that are highly complementary to the hadron collider approach. Examples will be drawn from ILC and other accelerator designs such as FCC-ee and ReLiC and will cover threshold lineshape based measurements and continuum reconstruction of the W mass as was already established at LEP2.

The bottom line is that the next generation of colliders designed for exploring the Higgs will also be very well equipped for advancing our knowledge of the W mass to MeV level precision either concurrently with ZH production operation or with operation near WW threshold.

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

Wmass_mWDays.pdf

19 W mass calculation in the Standard Model (30' talk + 30' discussion)

An overview is given on the the various steps to get precise SM predictions of the W-boson mass from a given set of input parameters (Fermi constant, electromagnetic fine structure constant, Z-boson mass, top-quark and Higgs-boson masses, strong coupling constant), in the on-shell scheme and the MS-bar scheme. The current status is reviewed, topical predictions and their uncertainties are presented and discussed.

Speaker: Wolfgang Hollik

Wmass_hollik.pdf

20 MW in the context of global fits in the SM and beyond (30' talk + 30' discussion)

We discuss the role of MW in the context of global fits of electroweak precision observables, and the compatibility of the current experimental value with the SM. We then generalize the analysis to physics beyond the SM, considering oblique NP and the SMEFT.

Speaker: Luca Silvestrini (INFN, Rome)

Silvestrini@MWDays23.pdf

12:30 Lunch

21 MW in the SMEFT (30' talk + 30' discussion)

I will discuss the interpretation of the recent CDF W mass measurement as part of a global analysis in the SMEFT framework at linear, dimension-6 level. Combining data from EW precision observables, Higgs signal strengths and diboson production allows for the identification of the preferred regions of parameter space in light of this measurement. I will also discuss how one can use the SMEFT results to determine which single-field extensions of the SM are able to account for the deviation. Finally I will comment on the impact of dimension-8 effects in a model with a hyper charge-zero electroweak triplet scalar in relation to the W-mass anomaly.

Speaker: Ken Mimasu (King's College London)

Mimasu_MWdays_flat.pdf

Mimasu_MWdays_presentation.pdf

22 Considerations on the combination procedure of correlated errors (30' talk + 30' discussion)

I will discuss the combination procedure of measurements with correlated uncertainties, including a brief description of the general formalism assuming multivariate Gaussian distributions,as well as concrete examples of a simplified approach. I will also comment on PDG scale factors and an alternative.

Speaker: Prof. Jens Erler (JGU Mainz)

MWDays23.pdf

16:00 Coffee break

23 Round table/discussion session

Speakers: Josh Bendavid (Massachusetts Inst. of Technology (US)), Alessandro Vicini (Università degli Studi e INFN Milano (IT)), Chris Hays (University of Oxford (GB)), Miguel Ramos Pernas (University of Warwick (GB)), Stefan Dittmaier (Albert Ludwigs Universitaet Freiburg (DE))

MWDays Discussion Points.pdf

Thursday, 20 April

24 W mass and (g-2)_mu within the 2HDM+a (30' talk + 15' discussion)

I will investigate the capability of the 2HDM+a of accommodating the recently reported anomalies in the measurements of the mass of the W and g-2. Potential connections with the DM puzzle will be also investigated.

Speaker: Giorgio Arcadi

MW23_arcadi.pdf

25 Two-loop investigation of new physics effects on the W-boson mass from a doublet extension of the SM Higgs sector (30' talk + 15' discussion)

One year ago, the CDF collaboration reported a new precision measurement of the $W$-boson mass $M_W$, exhibiting a large deviation from the value predicted by the Standard Model (SM).
In this talk, I will investigate possible new physics contributions to $M_W$ from extended Higgs sectors, focusing as a specific example on the Two-Higgs-Doublet Model (2HDM). Employing predictions for the electroweak precision observables in the 2HDM at the two-loop level and taking into account further theoretical and experimental constraints, I will identify regions of the 2HDM parameter space in which the prediction for $M_W$ is close to the new CDF value. I will additionally discuss the compatibility of these regions with precision measurements of the effective weak mixing angle and the total width of the $Z$ boson, as well as the impact and importance of the two-loop corrections to $M_W$.

Speaker: Johannes Braathen (DESY)

Braathen_MWDay23.pdf

11:00 Coffee break

26 Non Standard Model Higgs and the future of composite dynamics (30' talk + 15' discussion)

We critically analyse the future of composite dynamics via the impact of non standard model Higgs on the (non) observed g-2 and W-mass anomalies.

Speaker: Francesco Sannino (Syddansk Universitet (DK))

2nd-Francesco-CERN-Portoroz-2023.pdf

12:15 Lunch

27 W mass in extended Georgi-Machacek model (30' talk + 15' discussion)

We show that a larger W boson mass can be explained by nonaligned vacuum expectation values of isospin triplet scalar fields in the Georgi-Machacek model extended with custodial symmetry-breaking terms in the potential. The latter is required to avoid an undesirable Nambu-Goldstone boson as well as to be the consistent treatment of radiative corrections. With the W mass as one of the renormalization inputs at the one-loop level, we derive the required difference in the triplet vacuum expectation values, followed by a discussion of phenomenological consequences in the scenario.

Speaker: Prof. Cheng-Wei Chiang (National Taiwan University)

CERN MWDays23 Workshop - W mass in extended GM model - Chiang.pdf

28 W Boson Mass and Grand Unification (30' talk + 15' discussion)

It is known that the recently reported shift of the W boson mass can be easily explained by an $SU(2)_L$ triplet Higgs boson with zero hypercharge if it obtains a vacuum expectation value of O(1) GeV.

Surprisingly, the addition of a TeV scale complex triplet Higgs boson to the standard model leads to a precise unification of the gauge couplings at around $10^14$ GeV.

Although it seems the proton decay constraints would doom such a low uni cation scale, I will show that the constraints can be avoided by introducing vector-like fermions which mix with the SM fermions through mass terms involving the GUT breaking Higgs field.

As I will discuss, this will lead to a scenario which is not ruled out but could be tested in near future proton decay experiments. Importantly, the simplest viable model only requires the addition of one pair of vector-like fermions transforming 10 and 10.

I will also discuss a minor tweak to this model which will allow us to identify the other triplet as dark matter. Lastly, I will discuss the more general ramifications of the W boson mass for grand unification .

Speaker: Prof. Jason Evans (Shanghai Jiaotong University/TDLI)

JasonEvansMWdays.pdf

JasonEvansMWdays.pptx

15:30 Coffee break

29 The W mass and beyond (30' talk + 15' discussion)

In this talk I consider the W mass, assuming that a measured value different from the SM prediction is due to BSM physics, within the bigger picture of signs for new physics (anomalies). In particular, a positive shift in the W mass can be obtained with leptoquarks, vector-like quarks, Z' bosons and a scalar triplet (Y=0). I discuss which anomalies can be explained by these particles as well and to which interesting experimental signals these SM extensions lead.

Speaker: Andreas Crivellin (University of Zurich (CH))

WmassCERN2023.pdf

WmassCERN2023.pptx

30 Confronting the W mass anomaly with a possible observation of primordial gravitational waves (30' talk + 15' discussion)

We discuss a possibility to probe a large class of scenarios beyond the Standard Model simultaneously explaining the recent CDF II measurement of the W boson mass and predicting first-order phase transitions testable in future gravitational-wave experiments. We discuss this methodology focusing on a specific example of the Standard Model extension with an additional scalar $SU(2)_L$ triplet coupled to the Higgs boson.

Speaker: Roman Pasechnik (Lund university)

MWdays23-Pasechnik.pdf