Physics beyond the Standard Model in light of the CDF W boson mass anomaly

Friday 24 Jun 2022, 11:00 → 19:30 Asia/Seoul

8101 in building 8 (KIAS)

The long wait for a new physics signal beyond the Standard Model might have been answered: the recent W boson mass measurement by the CDF collaboration yields about a seven-sigma deviation from the Standard Model prediction.  The CDF's unprecedented precision of the W boson mass (see the talk by Prof. Ashutosh Kotwal on 31 May), if confirmed by other experiments, has profound implications for various new physics models.  In view of this, therefore, we bring together particle physicists working in the field of BSM for the explanation of the CDF W boson mass anomaly, after listening to how to determine the W boson mass at the Tevatron.

The meeting welcomes remote as well as in-person participants.  To the latter, social dinner shall be offered.  One can choose the form of attendance and sign up for dinner through registration which will be open until the 20th of June.  The registrants (and only they) will then receive the zoom link.

Invited speakers include:

• Emanuele Bagnaschi (CERN, Switzerland)
• Rick Gupta (TIFR, India)
• Sungwoo Hong (Chicago and ANL, USA)
• Joshua Isaacson (FNAL, USA)
• Tao Liu (HKUST, Hong Kong S.A.R.)
• Zuowei Liu (Nanjing U, China)
• Jeonghyun Song (KonKuk U, Korea)
• Dominik Stöckinger (TU Dresden, Germany)

See also:

• 31 May seminar by Ashutosh Kotwal (Duke U)

Organizers:

• Jongkuk Kim (KIAS)
• Pyungwon Ko (KIAS)
• Jae-hyeon Park (KIAS)
• Myeonghun Park (SeoulTech/KIAS)
• Jeonghyeon Song (Konkuk U)

1 How to measure the W Mass: A Theory Perspective

Speaker: Joshua Isaacson (Fermi National Accelerator Laboratory)

M_W__A_Theory_Overview__KIAS_.pdf

Video

12:00 lunch

2 2HDM in light of the CDF W boson mass and the muon anomalous magnetic moment

The recent W boson mass measurement by the CDF collaboration with unprecedented precision indicates a significant deviation from the standard model prediction. This has profound consequences in searching for physics beyond the SM. In the framework of two-Higgs-doublet models, we study the effect of the new W mass measurement on the parameter space. We impose other constraints, including theoretical requirements, flavor-changing neutral currents in physics, the cutoff scale above 1 TeV, Higgs precision data, and direct collider search limits from the LEP, Tevatron, and LHC experiments. We find that upper bounds exist on the masses of the heavy Higgs bosons. And type-II and type-Y in the inverted scenario are completely excluded. Simultaneous explanation including the muon g-2 and lepton flavor universality data is also discussed in the Higgs-phobic type-X.

Speaker: Jeonghyeon Song (Konkuk University)

220624-KIAS-Song.pdf

Video

3 Correlating the W Mass with Higgs Couplings

The recent updated measurements of W and Z masses by CDF-II collaboration, if correct, suggest that there may exist new physics at around 6 TeV if new physics effects come from tree-level physics or at around a few 100 GeV if they are loop-induced effects. The majority of BSM models seem to generate required S and T dimension-6 operators at loop-level, thereby rendering a couple of 100 GeV as a new target for BSM searches. In this talk, I discuss a rather generic correlation between the shift in W mass and Higgs couplings. For this, we note that Higgs-di-gluon and Higgs-di-photon couplings within the SM are one-loop induced, dominantly by the top-loop for the former and W-loop for the latter. New physics within the Higgs sector with mass scale a few 100 GeV (needed to make a significant shift in W mass) is then expected to make corrections to these SM couplings. Given that both are loop-induced with not so large scale separation, one should then expect these effects are rather significant, either imposing non-trivial constraints already or large enough size testable in the near future.

Speaker: Sungwoo Hong (Chicago and ANL)

Slides

Video

14:20 coffee

4 CDF W mass anomaly from a dark sector with a Stueckelberg-Higgs portal

We propose an explanation to the new W mass measurement recently reported by the CDF collaboration, which is larger than the standard model expectation by about 7 standard deviations. To alleviate the tensions that are imposed on the electroweak sector by the new W mass measurement, we carry out an analysis in the Stueckelberg extended standard model where a new neutral gauge boson appears which mixes with the two neutral gauge bosons in the electroweak sector both via the Stueckelberg mass terms and via the gauge invariant Stueckelberg-Higgs portal interaction and spoils the custodial symmetry at the tree level so that the simple relation between the W boson mass and the Z boson mass does not hold. We find that such an extension increases the W boson mass if the new gauge boson mass is larger than the Z boson mass. We further show that there exists a significant part of the parameter space in the extended model which includes the CDF mass anomaly and is consistent with the various observables at the Z pole and consistent with the ATLAS dilepton limits. The Stueckelberg Zprime boson, which resolves the CDF W mass anomaly, should be searchable in future LHC experiments.

Speaker: Zuowei Liu (Nanjing University)

Slides

Video

5 Running away from the T-parameter solution to the W mass anomaly

We show that it is essential to include renormalisation group (RG) effects for determining the SMEFT parameter space consistent with the CDF W-mass anomaly at the matching scale. We RG evolve the low energy SMEFT parameter space consistent with the anomaly to the matching scale and find a much larger allowed region. In particular we find that it is possible to have a vanishing or even negative T -parameter at the matching scale. This will hopefully lead to a larger set of UV completions that can explain the anomaly. This effect is possible because operators that are only weakly constrained—for instance those probed by diboson and Higgs data—can have a contribution to the W-boson mass via one-loop RG effects, that is comparable to the tree-level contribution of strongly constrained operators related to electroweak precision observables. For these one-loop contributions to be important a relatively low new physics scale around 800 GeV is required. This enhances the possibility of probing this new physics in direct and indirect searches in the recent future.

Speaker: Rick Gupta (Tata Institute of Fundamental Research)

Slides

Video

6 W-Boson Mass, SMEFT and Future Tests at e⁺e⁻ Collider

Recently the CDF collaboration reported a significant discrepancy between the direct measurement of the W-boson mass and its Standard Model (SM) prediction based on electroweak precision tests. In this talk we will present an SMEFT interpretation on this observation and discuss its implications for beyond-the-SM physics and tests at future e⁺e⁻ collider.

Speaker: Tao Liu (Hong Kong University of Science and Technology)

Slides

Video

16:40 coffee

7 SMEFT Analysis of the W boson mass in light of the recent CDF measurement

We use the Fitmaker tool to incorporate the recent CDF measurement of mW in a global fit to electroweak, Higgs, and diboson data in the Standard Model Effective Field Theory (SMEFT) including dimension-6 operators at linear order. We find that including any one of the SMEFT operators OHWB, OHD, Oℓℓ or O(3)Hℓ with a non-zero coefficient could provide a better fit than the Standard Model, with the strongest pull for OHD and no tension with other electroweak precision data. We then analyse which tree-level single-field extensions of the Standard Model could generate such operator coefficients with the appropriate sign, and discuss the masses and couplings of these fields that best fit the CDF measurement and other data. In particular, the global fit favours either a singlet Z′ vector boson, a scalar electroweak triplet with zero hypercharge, or a vector electroweak triplet with unit hypercharge, followed by a singlet heavy neutral lepton, all with masses in the multi-TeV range for unit coupling.

Speaker: Emanuele Angelo Bagnaschi (CERN)

MW-KIAS-BAGNASCHI.pdf

8 SM and BSM predictions of Mᴡ using different renormalization schemes—FlexibleSUSY implementation and the example of the MRSSM

Loop computations of Mᴡ in BSM scenarios can be done using different renormalization schemes such as on-shell, MSbar, or mixed schemes. We discuss the differences, pros and cons, and point out the possibility of numerically large fake effects. The current implementation in the program FlexibleSUSY avoids such effects and allows to compute Mᴡ in a wide range of BSM scenarios. As an example we mention the MRSSM (R-symmetric supersymmetric standard model), which leads to tree-level and one-loop contributions to Mᴡ and allows to accommodate the recent CDF measurement of Mᴡ.

Speaker: Dominik Stöckinger (Technische Universität Dresden)

Slides

Video

18:20 dinner