TDLI-PKU BSM workshop 2022: Electroweak lights the way

1 Aug 2022, 08:55 → 3 Aug 2022, 16:40 Asia/Shanghai

Tsung-Dao Lee Institute

Jason Evans (SJTU/TDLI), Jia Liu (Peking University), Shu Li (TDLI/SJTU), Yuichiro Nakai

An annual workshop on beyond the Standard Model physics organized by Tsung-Dao Lee Institute (TDLI) and Peking University (PKU). This year, our focus is on new physics around the electroweak scale for which there are several hints emerging. The workshop will consist of online talks from both theorists and experimentalists.

Invited Speakers

(Theorists)

Lorenzo Calibbi
JiJi Fan
Jiayin Gu
Teppei Kitahara
Xiaoping Wang
Ke-pan Xie
Tsutomu Yanagida
Norimi Yokozaki
Yongchao Zhang
 

(Experimentalists)

Fei Gao
Kim Siang Khaw
Kun Liu
Chen Zhou

 

Organizers:

Jason Evans (TDLI & SPA, SJTU)
Jia Liu (PKU)
Yuichiro Nakai (TDLI & SPA, SJTU)
Shu Li (TDLI & SPA, SJTU and CHEP, PKU)

Workshop Secretary：

Wen Wang (E-mail: wang.wen@sjtu.edu.cn)

Zoom link：

https://cern.zoom.us/j/69917956932?pwd=cFRXTmVHMWJPZmQ5UmxDOVh4cHFwUT09

Meeting ID: 699 1795 6932

Password: 945806

Monday, 1 August

08:55 → 09:00 Opening

Speaker: Jason Evans (SJTU/TDLI)

BSMOpening.pptx

09:00 → 09:40 Some lessons from recent experimental anomalies

Recently there have been two interesting and intriguing experimental results, one on the muon g-2 from Fermilab and one on the W boson mass from CDF. I will discuss some possible implications of these results for new physics, provided that they survive. For muon g-2, I will discuss a relatively new explanation using the loop effects of a heavy axion coupling to leptons and photons. I will provide an updated analysis of the necessary couplings, including two-loop contributions, and show that the new physics operators point to an axion decay constant on the order of 10s of GeV. I will also discuss the challenges to UV complete this explanation. For the W mass, I will discuss the implications using a set of six-dimensional operators in the SM effective field theory and comment on other further indirect tests of the physical origin for this anomalous discrepancy such as the Higgs couplings.

Speaker: JiJi Fan

TDLI-PKU 2022 .pdf

09:40 → 10:20 Recent progress in Muon g-2

Muon magnetic anomaly is a very sensitive probe to new physics beyond the Standard Model. It can be calculated with very high precision in the Standard Model and can be precisely measured using the magnetic storage ring approach. The first result from the Fermilab Muon g-2 experiment has triggered a worldwide effort in scrutinizing both the Standard Model predictions and experimental measurements of the muon magnetic anomaly. Moreover, a lot of BSM models were proposed to explain the apparent discrepancy. In this workshop, I will give a brief overview of the current status of the theoretical predictions, together with the progress of the Muon g-2 experiments at Fermilab and J-PARC.

Speaker: Kim Siang Khaw

TDLIPKU_BSMWorkshop_Khaw_20220801.pdf

10:20 → 10:40 Break

10:40 → 11:20 Supersymmetry is the Physics of this Century

Speaker: Tsutomu Yanagida

11:20 → 12:00 SMEFT at future lepton colliders

Speaker: Jiayin Gu

JiaYin-ees10.pdf

12:00 → 14:00 Break

14:00 → 14:40 B anomaly hunting at the LHC: tau b + missing search for leptoquarks

One of the long-standing B anomalies is the $b \to c \tau \nu$ anomaly, which remains at $\sim 4$ sigma level. This anomaly will be confirmed or disappeared by the ongoing Belle II and LHCb experiments. In this talk, we will discuss the possibility that another crosscheck could be possible by the LHC search. In our work arXiv:2111.04748, we study non-resonant searched for new physics at the LHC by considering final states with an energetic and hadronically decaying $\tau$ lepton, a $b$-jet and large missing transverse momentum ($pp \to \tau \b + E_T^{miss}$). This channel is related to the $b \to c \tau \nu$ process by the crossing symmetry of the amplitudes. We analyze them not only within the dimension-six EFT but also in explicit leptoquark models. Although the leptoquark models provide a weaker sensitivity than the EFT, it is found that the non-resonant search of $pp \to \tau \b + E_T^{miss}$ can improve the sensitivity by $\sim 40\%$ versus a conventional $pp \to \tau + E_T^{miss}$ search in the whole leptoquark mass region. Consequently, it is expected that most of the parameter regions suggested by the B anomaly can be probed at the HL-LHC. Also, it is shown that SU(2) doublet leptoquark scenario is accessible entirely once the LHC Run 2 data are analyzed. In addition, we discuss the angular correlations among $b, \tau$ and the missing transverse momentum to discriminate the LQ scenarios.

Speaker: Teppei Kitahara

Teppei_TDLI-PKU.pdf

14:40 → 17:40 Contributed talks (1)

14:40 Dark SHINE——Dark Photon fixed-target search experiment at SHINE Facility

This talk will present the R&D study of the prospect and feasibility to deploy the fixed-target experiment utilizing the high rate single electron beam from the SHINE facility under construction. The project is officially sponsored by NSFC Original Exploration Project 2021 and Shanghai pilot program for basic research.

Speaker: Jing Chen (SJTU/TDLI)

DarkShine_Jing_TPBSMW2022.pptx

15:00 Electroweak precision tests for triplet scalar

Electroweak precision observables are fundamental for testing the standard model (SM) or its extensions. The influences on observables from new physics within the electroweak sector will be expressed in terms of oblique parameters S, T, U. By performing the global fit with the CDF new W mass, we obtain $S=0.03 \pm 0.03$, $T=0.06 \pm 0.02$ and $U=0.16 \pm 0.03$ or $S=0.14 \pm 0.03$, $T=0.24 \pm 0.02$ with $U=0$, which strongly indicate the need of the new non-degenerate multiplets by extending SM. We discuss two different cases of simple extensions by a new hypercharge-one triplet scalar $\Delta$ or hyperchargeless real triplet scalar $\Sigma$. These triplets will firstly affect the oblique parameters and further observables so that we can directly choose the new triplet parameters to perform the global fit. For $Y=1$ case, we choose $m_H$, $\lambda_4$ and $v_\Delta$ as fit parameters and obtain $m_{H}=296.02 \pm 10.18$ GeV,
$\lambda_4=2.58 \pm 0.090$ and $v_\Delta=4.82 \pm 0.34$ GeV. For $Y=0$ case, the potential parameter $b_4$ gives the very stringent constraint so that we cannot find reasonable fit values. In the case of ignoring the $b_4$ constraint, we obtain $m_{H^+}=77.16 \pm 17.12$ GeV, $\Delta m=-14.27\pm4.22$ GeV and
$v_\Delta=3.20 \pm 0.30$ GeV. We conduct the specific phenomenological analysis, such as vacuum stability, perturbative unitarity, Higgs data and calculate the decay ratios of the new scalars. These can be further testified by future lepton colliders by pair production $H^{++}H^{--}$.

Speaker: Huang Fei (SJTU)

15:20 Search for HH-->4b production and H-->aa-->4b exotic decays with ATLAS and CEPC

This talk will present the HH-->4b analysis result at ATLAS and also the exotic decays of 125GeV SM Higgs to light singlet scalar pairs in 4b final states with future circular colliders such as CEPC.

Speaker: Zhen Wang (TDLI/SJTU)

15:40 Break

16:00 Search for Dark Higgs at ATLAS and potential to utilize the Xbb tagger

This talk will present the latest searches for Mono-H125 and Mono-Scalar productions with SM and BSM Higgs at ATLAS, as a direct probe to BSM portal of new physics and especially Dark Matter. A potential of utilizing the boosted Xbb tagger will be also discussed.

Speaker: Changqiao LI (SJTU/TDLI)

ChangqiaoLI_DarkHiggs.pdf

16:20 Muon Electric Dipole Moment as a Probe of Flavor-Diagonal CP Violation

Electric dipole moments (EDMs) of elementary particles are powerful probes of new physics with flavor-diagonal CP violation. The reported discrepancy in the muon anomalous magnetic moment motivates us to explore to what extent new physics with flavor-diagonal CP violation to address the discrepancy is probed by searches for the muon EDM. As a benchmark, we focus on a CP-violating two-Higgs-doublet model to explain the muon $g-2$ anomaly where the muon exclusively couples to one Higgs doublet. Since contributions to flavor violating processes as well as the electron EDM are suppressed, the muon EDM becomes an essential probe of the model. Our result shows that some viable parameter space leads to the muon EDM of around $d_{\mu} \simeq 6 \times 10^{-23} \, e \, \rm cm$ probed by the PSI experiment and most of the parameter space is covered by the proposed J-PARC experiment.

Speaker: Yoshihiro Shigekami (Tsung-Dao Lee Institute)

TDLI-PKU_Shigekami.pdf

Tuesday, 2 August

09:00 → 09:40 Muon g-2 and B anomalies from Dark Matter

We systematically build and discuss a class of models with minimal field content that can simultaneously provide: (i) a thermal Dark Matter (DM) candidate; (ii) large loop contributions to $b\to s\ell\ell$ processes able to address $R_K$ and the other $B$ anomalies; (iii) a natural solution to the muon $g-2$ discrepancy through chirally-enhanced contributions. We show what are the minimal ingredients and properties necessary to explain both anomalies through loop effects directly involving the DM particles and few other new fields. The general characteristic of this class of models is that the DM phenomenology is controlled by the same parameters that enter the flavour observables. As a consequence, they feature a high degree of correlation among DM, flavour and collider searches and thus an enhanced testability. The new particles are generally heavy enough to evade limits set by LHC searches, but could be in the reach of present and future colliders and direct detection experiments.

Speaker: Lorenzo Calibbi

calibbi-TDLI-PKU.pdf

09:40 → 10:20 Recent updates on Higgs properties measurement at CMS and ATLAS

After 10 years of the Higgs boson discovery, the leading Higgs production and decay channels have been observed at the Large Hadron Collider, i.e: ggF, VBF, WH, ZH, ttH and H→bb, WW, 𝛕𝛕, ZZ, 𝛄𝛄 etc. The measurement of Higgs couplings with vector bosons and with third generation of fermions has reached to 10%-15% level of precision. Moreover, Higgs self-coupling as well as Higgs couplings with muon-lepton and charm-quark are also constrained. All those measurements are in agreement with SM predictions, which plays strict constraints to new physics at the Electroweak scale. In this talk, latest updates of the Higgs properties measurements and prospectives at the LHC will be presented.

Speaker: Kun Liu (TDLI / SJTU)

HiggsUpdates2022TDLI-PKU.pdf

10:20 → 10:40 Break

10:40 → 11:20 Probing electroweak phase transition with multi-TeV muon colliders and gravitational waves

We study the complementarity of the proposed multi-TeV muon colliders and the near-future gravitational wave (GW) detectors to the first order electroweak phase transition (FOEWPT), taking the real scalar extended Standard Model as the representative model. A detailed collider simulation shows the FOEWPT parameter space can be greatly probed via the vector boson fusion production of the singlet, and its subsequent decay to the di-Higgs or di-boson channels. Especially, almost all the parameter space yielding detectable GW signals can be probed by the muon colliders. Therefore, if we could detect stochastic GWs in the future, a muon collider could provide a hopeful crosscheck to identify their origin. On the other hand, there is considerable parameter space that escapes GW detections but is within the reach of the muon colliders. The precision measurements of Higgs couplings could also probe the FOEWPT parameter space efficiently.

Speaker: Kepan Xie

TDLI-PKU_online.pdf

11:20 → 12:00 Higgs rare and exotic decays at CMS and ATLAS

This talk will discuss the recent results about the rare and exotic decays of the Higgs boson from the CMS and ATLAS experiments. These decay modes are important portals to refine our understanding of the electroweak sector and search for new physics.

Speaker: Chen Zhou

chenzhou_20220802.pdf

12:00 → 14:20 Break

14:20 → 17:10 Contributed talks (2)

14:20 Flavor-changing Majoron interactions with leptons

When the Standard Model Higgs sector is extended with a complex singlet that breaks global lepton number symmetry spontaneously, a massless Goldstone boson called the Majoron $J$ arises. In addition to increasing Higgs invisible decay through mixing, the Majoron can generally have flavor-changing interactions with fermions. We use the type-III seesaw mechanism to demonstrate the existence of such couplings with both charged leptons and neutrinos. This opens up new channels to search for the Majoron. We use the experimental data such as muonium-anti-muonium oscillation and flavor-changing neutrino and charged lepton decays to put constraints on the couplings. Besides, we propose a polarization asymmetry of flavor-changing $\ell \to \ell' J$ decays that can reveal the chiral information of the interactions.

Speaker: Jin Sun (Shanghai Jiao Tong University)

FC Majoron-Jin Sun.pdf

14:40 Vector Boson Scattering and new phenomena at LHC

Observations of Vector Boson Scattering processes (VBS) are one of the major achievements of EWSB and Higgs unitarization mechanism studies at LHC Run2. This talk will bring the latest news from LHC in VBS observations and highly evident measurements, as well as the bridge to new physics portal utilizing such scattering final states.

Speaker: Despoina Sampsonidou (Tsung-Dao Lee Institute, Shanghai Jiao Tong Univ.)

TDLI-PKU_BSM_08_2022_DSampsonidou.pdf

15:00 Charged Lepton Flavor Violation at the EIC

We present a comprehensive analysis of the potential sensitivity of the Electron-Ion Collider (EIC) to charged lepton flavor violation (CLFV)
in the channel $ep\to \tau X$, within the model-independent framework of the Standard Model Effective Field Theory (SMEFT).
We compute the relevant cross sections to leading order in QCD and electroweak corrections and perform simulations of signal and SM background events in various $\tau$ decay channels, suggesting simple cuts to enhance the associated estimated efficiencies. To assess the discovery potential of the EIC in $\tau$-$e$ transitions, we study the sensitivity of other probes of this physics across a broad range of energy scales, from $pp \to e \tau X$ at the Large Hadron Collider to decays of $B$ mesons and $\tau$ leptons,
such as $\tau \to e \gamma$, $\tau \to e \ell^+ \ell^-$, and crucially the hadronic modes $\tau \to e Y$ with $Y \in \{ \pi, K, \pi \pi, K \pi, ...\}$.
We find that electroweak dipole and four-fermion semi-leptonic operators involving light quarks are already strongly constrained by $\tau$ decays, while operators involving the $c$ and $b$ quarks present more promising discovery potential for the EIC. An analysis of three models of leptoquarks confirms the expectations based on the SMEFT results. We also identify future directions needed to maximize the reach of the EIC in CLFV searches: these include an optimization of the $\tau$ tagger in hadronic channels, an exploration of background suppression through tagging $b$ and $c$ jets in the final state, and a global fit by turning on all SMEFT couplings, which will likely reveal new discovery windows for the EIC.

Speaker: Bin Yan (IHEP)

15:20 Break

15:40 Search for top quark FCNC interactions at ATLAS

The large dataset collected by the ATLAS detector at allows to probe the presence of new physics that could enhance the rate of rare processes in the SM. The LHC can therefore gain considerable sensitivity for Flavour Changing Neutral Current (FCNC) interactions of the top quark. The ATLAS experiment has performed searches for FCNC couplings of the top quark with a photon, gluon, Z boson or Higgs boson. In this report, the most recent results are presented, which include the complete data set of 139/fb at 13 TeV during run 2 (2015-2018). The large data set, together with improvements in the analysis, yields a strong improvement of the expected sensitivity compared to previous experiments.

Speaker: Mingming Xia (Tsinghua University)

TDLI-PKU-BSMworkshop2022_mmx.pdf

16:00 CP-violating dark photon kinetic mixing and type-III seesaw model

The hypothetical dark photon portal connecting the visible and dark sectors of the Universe has received
considerable attention in recent years, with a focus on CP-conserving kinetic mixing between the Standard
Model hypercharge gauge boson and a new U(1)X gauge boson. In the effective field theory context, one
may write nonrenormalizable CP-violating kinetic mixing interactions involving the X and SU(2)L gauge
bosons. We construct for the first time a renormalizable model for CP-violating kinetic mixing that induces
CP-violating non-Abelian kinetic mixing at mass dimension 5. The model grows out of the type-III seesaw
model, with the lepton triplets containing right-handed neutrinos playing a crucial role in making the model
renormalizable and providing a bridge to the origin of the neutrino mass. This scenario also accommodates
electron electric dipole moments (EDM) as large as the current experimental bound, making future EDM
searches an important probe of this scenario.

Speaker: Yu Cheng

darkphoton_ChengYu.pdf

16:20 Type-II Seesaw Triplet Scalar Effects on Neutrino Trident Scattering

In Type-II seesaw model, an electroweak triplet scalar field $\Delta$ with a non-zero vacuum expectation value (vev) $v_\Delta$ is introduced to facilitate the generation of small neutrino masses. A non-zero $v_\Delta$ also affects the W mass through the electroweak $\rho$ parameter, making it to be less than 1 as predicted by standard model (SM). The component fields in $\Delta$ come along introduce additional contributions to reduce the SM rare neutrino trident scattering cross section. These fields also induce new processes not existed in SM, such as $l_i \to \overline{ l_j} l_k l_l$ and $l_i \to l_j \gamma$. There are severe constraints on these processes which limit the effects on neutrino trident scattering and the $\rho$ parameter and therefore the W mass. The newly measured W mass by CDF makes the central value of $\rho$ parameter to be larger than 1, even larger than previously expected. Combining neutrinoless double beta decay, direct neutrino mass and oscillation data, we find a lower limit for $v_\Delta$ as a function of the triplet scalar mass $m_\Delta$, $v_\Delta > (6.3 \sim 8.4) \mathrm{eV} (100 \mathrm{GeV}/m_\Delta)$. To have significant effect on $\rho$ in this model, $v_\Delta$ needs to be in the range of a GeV or so. However this implies a very small $m_\Delta$ which is ruled out by data. We conclude that the effect of triplet vev $v_\Delta$ on the W mass can be neglected. We also find that at 3$\sigma$ level, the deviation of the ratio for Type-II Seesaw to SM neutrino trident scattering cross section predictions is reduced to be below 1, but is restricted to be larger than 0.98.

Speaker: Mingwei Li (TDLI)

trident.pdf

Wednesday, 3 August

09:00 → 09:40 MeV new physics light from muon g-2

The muon g-2 is an interesting observable, since it can be measured with great precision and can be computed with excellent accuracy within the Standard Model (SM). The current experimental measurement of muon g-2 shows a deviation to the SM prediction, which may be a hint of new physics. A light particle, scalar or vector, can be nature new physics candidates to explain the current muon g-2 result. If it is a light scalar with a mass around 1 MeV. It can be connected to the origin of neutrino masses and simultaneously survive current bounds on relativistic degrees of freedom in the early universe. If it is a light scalar with mass around pion mass and a coupling to muons of the order of the Standard Model Higgs coupling, it can be tested in the KOTO experiment. If it is a complex scalar with real part around 200 MeV, it can explain muon g-2 and can be tested via electron g-2 experiment. If the light particle for muon g-2 is a dark photon and its mass is time-varying due to environmental effects, for mass around tens of MeV, the muon g–2 solution from the kinetic mixing dark photon becomes viable again. The scenario can be further tested by reanalyzing the existing data with timing information included.

Speaker: Xiaoping Wang

XPW-shanghai-2022-8-3.pdf

09:40 → 10:20 First Results from XENONnT

Speaker: Fei Gao

TDLI-PKU_BSM_workshop_xenon_fei.pdf

10:20 → 10:40 Break

10:40 → 11:20 CP/flavor-safe SUSY model for light sleptons

SUSY CP and flavor problems are central issues for SUSY scenarios with light sleptons whose masses are below or around the TeV scale. In particular, these problems are severe when SUSY is responsible for the muon g-2 anomaly: the CP problem is more difficult than naively thought, given the effects of anomaly mediation, etc. In this talk, I will introduce a CP/flavor-safe SUSY breaking mechanism using axion supermultiplet. The strong CP problem is also solved simultaneously. I will also show that the muon g-2 anomaly can indeed be explained while circumventing other phenomenological constraints.

Speaker: Norimi Yokozaki

tdli_yokozaki.pdf

11:20 → 12:00 Neutron-mirror-neutron oscillation and neutron star cooling

In the dense environment of neutron stars (NSs), neutrons $n$ can transit into mirror neutrons $n’$, which exist in some mirror models. Such a transition leads to exotic energy loss of NSs via emission of photons, which sets limit on the $n-n’$ mixing parameter $\delta_{nn’} \lesssim 10^{-17}$ eV. We point out that the beta decay of mirror neutrons and the subsequent formation of clouds of mirror electrons and deuterons inside the NSs will rob energy from the normal sector via $e - e'$ scattering. Given a wide range of milli-charge parameter $\epsilon$, the energy loss of NSs will be dominated by the emission of mirror photons $\gamma’$. Then the stringent bounds of NSs on $n-n'$ transition could be relaxed.

Speaker: Yongchao Zhang

mirror_neutron_TDLI.pdf

12:00 → 14:40 Break

14:40 → 16:40 Contributed talks (3)

14:40 Electroweak ALP Searches at a Muon Collider

A high-energy muon collider with center-of-mass energy around and above 10 TeV is also a vector boson fusion (VBF) machine, due to the significant virtual electroweak (EW) gauge boson content of high-energy muon beams. This feature, together with the clean environment, makes it an ideal collider to search for TeV-scale axion-like particles (ALP) coupling to Standard Model EW gauge bosons, which current and other future colliders have limited sensitivities to. We present detailed analyses of heavy ALP searches in both the VBF and associated production channels at a muon collider with different running benchmarks. We also show projected constraints on the ALP couplings in the effective field theory, including an operator with its coefficient not determined by the mixed Peccei-Quinn anomaly. We demonstrate that a muon collider could probe new ALP parameter space and push the sensitivities of the couplings between the ALP and EW gauge bosons by one order of magnitude compared to HL-LHC. The projected limits and search strategies for ALPs could also be applied to other types of resonances coupling to EW gauge bosons.

Speaker: Lingfeng Li (Brown U.)

EW_ALP_at_Muon_TDLI.pdf

15:00 Dark Hadrons at Lifetime Frontier Experiments

Dark hadrons are hypothetical particles which reside in the dark sector and originate from the confining gauge dynamics in the dark sector. These particles are proposed in several dark sector models, such as composite asymmetric dark matter models and strongly interacting massive particle models. The dark sector is feebly connected to our sector through dark photons which kinematically mix with our photons. While alleviating cosmological problems, dark photons make dark hadrons long-lived in terrestrial experiments. Moreover, the dark hadrons are produced through the very same dark photon. In this study, we discuss the visible decay searches for dark hadrons. For a few GeV dark hadrons, the LHC lifetime frontier, MATHUSLA and FASER, has a potential to discover their decay when kinetic mixing angle of dark photon is $\epsilon > 10^{-4}$. On the other hand, fixed-target experiments, in particular DarkQuest, will have a great sensitivity to dark hadrons with a mass below GeV and with kinetic mixing $\epsilon > 10^{-4}$ in addition to the LHC lifetime frontier. These projected sensitivities to dark hadrons in dark photon parameter space are comparable with the future sensitivities of dark photon searches, such as Belle-II and LHCb.

Speaker: Takumi Kuwahara (Peking U)

TDLI-PKU.pdf

15:20 Break

15:40 A search for heavy Higgs bosons decaying into vector bosons in same-sign two-lepton final states in $pp$ collisions at $\sqrt{s}=13$~TeV with the ATLAS detector

A search for heavy Higgs bosons decaying into a pair of vector bosons and produced in association with a vector boson is performed, using final states with two leptons of the same electric charge (electrons or muons), missing transverse momentum and jets. A data sample of proton-proton collisions at a centre-of-mass energy of 13 TeV recorded with the ATLAS detector at the Large Hadron Collider between 2015 and 2018 is used. The data correspond to a total integrated luminosity of $139~\mathrm{fb^{-1}}$. The observed data are in agreement with Standard Model background expectations. The results are interpreted using higher dimensional operators in an Effective Field Theory. The upper production cross-section limits at 95% confidence level are calculated as a function of the heavy Higgs boson mass and coupling strengths to vector bosons. Limits are set in the Higgs boson mass region 300 to 1500 GeV, and depend upon the assumed couplings. The highest heavy Higgs boson mass excluded with the coupling combinations explored is 900 GeV. Limits on coupling strength are also provided.

Speaker: Yue Xu

GHH_20220803.pdf

16:00 Precise Measurements of Z+photon final states and search for anomalous neutral gauge couplings with EFT at ATLAS

This talk will present the latest result of precise measurement of Z+photon+jets differential cross sections and the probe of BSM new physics via anomalous neutral gauge couplings parameterized with EFT formalism at ATLAS.

Speaker: Danning Liu (TDLI/SJTU)

Zgamma_Status_BSMWorkshop_Shanghai_DanningLiu.pdf

16:20 Dark photon kinetic mixing effects for the CDF W-mass measurement

A new $U(1)_X$ gauge boson $X$ primarily interacting with a dark sector can have renormalizable kinetic mixing with the standard model (SM) $U(1)_Y$ gauge boson $Y$. This mixing besides introduces interactions of dark photon and dark sector with SM particles, it also modifies interactions among SM particles. The modified interactions can be casted into the oblique $S$, $T$ and $U$ parameters. We find that with the dark photon mass larger than the $Z$ boson mass, the kinetic mixing effects can reduce the tension of the W mass excess problem reported recently by CDF from $7\sigma$ deviation to within $3 \sigma$ compared with theory prediction. If there is non-abelian kinetic mixing between $U(1)_X$ and $SU(2)_L$ gauge bosons, in simple renormalizable models of this type a triplet Higgs is required to generate the mixing. We find that this triplet with a vacuum expectation value of order 5 GeV can naturally explain the W mass excess.

Speaker: Zhi-peng Xing (TDLI)