Light Scalar and Lepton Anomalous Magnetic Moments

Light Scalar and Lepton Anomalous Magnetic Moments Vishnu Padmanabhan Kovilakam Oklahoma State University Based on: Phys.Rev.D 101 (2020) 11, 115037 (in collaboration with Sudip Jana and Shaikh Saad) Oklahoma State University 1 Muon Magnetic Moment ◦ Magnetic moment of Leptons: ◦ Lande’ g- factor: ◦ Due to Quantum corrections, (𝒈 − 𝟐)µ ≠ 𝟎. ◦ Anomalous Magnetic Moment: 2 Current Status of muon (g-2) 116591810 43 𝐒𝐌 1011 𝒂𝝁 = ቊ 116592040 54 𝐄𝐱𝐩 Δ𝒂𝝁 = 𝒂𝝁 𝒆𝒙𝒑 − 𝒂𝝁 𝑺𝑴 = 251 59 × 10−11 4.2 𝒔𝒊𝒈𝒎𝒂 Fermilab Muon g-2 Collaboration, B. Abi et al. (2021) 3 Possible Explanations in different contexts.. 4 Current Status of electron (g-2) Recent improved determination of the fine structure constant, leads to a negative discrepancy between the measured AMM of electron and the corresponding SM prediction. 1159652181.61 23 𝐒𝐌 1012 𝒂𝒆 = ቊ 1159652180.73 28 𝐄𝐱𝐩 Δ𝒂𝒆 = 𝒂𝒆 𝒆𝒙𝒑 − 𝒂𝒆 𝑺𝑴 = −87 36 × 10−14 2.4 𝜎 R. H. Parker, C. Yu, W. Zhong, B. Estey, and H. Mueller (2018) 5 Challenges A simultaneous explanation of these two anomalies is challenging ➢ Opposite Sign: 6 Possible Explanations ❑ With Lepto-quarks: I. Dorsner, S. Fajfer,S. Saad (2020) I. Bigaran, and R. R. Volkas (2020) ❑ With additional Fermions and Scalars: K.F.Chen,,C.W.Chiang, and K.Yagyu (2020) S. Jana, VPK, S. Saad, W. Rodejohann (2020) ❑ With light Z’: A. Bodas, R. Coy, and S. King (2021) 7 Possible Explanations ❑ With light Z’: A. Bodas, R. Coy, and S. King (2021) Is it possible to resolve these two anomalies in a more minimal setup? ❑ With additional Fermions andextension Scalars: Without any 1. gauge 2. BSM fermions 3. Colored scalars K.F.Chen,,C.W.Chiang, and K.Yagyu (2020) S. Jana, VPK, S. Saad, W. Rodejohann (2020) ❑ With Lepto-quarks: I. Dorsner, S. Fajfer,S. Saad (2020) I. Bigaran, and R. R. Volkas (2020) 8 Light Scalar ❑ A light neutral scalar that has coupling with the charged leptons can possibly resolve these two anomalies simultaneously. ❑ Muon AMM can be explained via a one-loop contribution, whereas the electron AMM via a two-loop Barr-Zee diagram. H. Davoudiasl, W. J. Marciano (2018) S. Jana, VPK, S. Saad (2020) 9 Light Scalar However, such a light scalar also leads to a two-loop contribution to muon AMM and a one-loop contribution to electron AMM. 10 Light Scalar However, such a light scalar also leads to a two-loop contribution to muon AMM and a one-loop contribution to electron AMM. Is it possible with singlet scalar extension of SM? 11 Light Scalar However, such a light scalar also leads to a two-loop contribution to muon AMM and a one-loop contribution to electron AMM. Is it possible with singlet scalar extension of SM? No! small Yukawa couplings. 12 Light Scalar However, such a light scalar also leads to a two-loop contribution to muon AMM and a one-loop contribution to electron AMM. What about in Two Higgs Doublet Model? 13 Light Scalar: 2HDM Scalar Sector: Alignment Limit: 𝜶 ≈ 𝜷 , SM Higgs decouples from the other CP-even Higgs. Considering 𝒎𝟐𝑯 ≪ 𝒎𝟐𝑯+ ≈ 𝒎𝟐𝑨 ∼ 𝓞 𝟏𝟏𝟎 𝑮𝒆𝑽 14 Light Scalar: 2HDM Yukawa Sector: For 𝒀𝒍 , we assume a diagonal texture 𝒀𝒍 = 𝒅𝒊𝒂𝒈(𝒚𝒆 , 𝒚µ , 𝒚𝞽 ). 15 Light Scalar: from 2HDM Muon AMM Electron AMM 16 Light Scalar: from 2HDM Setting 𝒎𝟐𝑯 ≪ 𝒎𝟐𝑯+ ≈ 𝒎𝟐𝑨 ∼ 𝓞 𝟏𝟏𝟎 𝑮𝒆𝑽 S. Jana, VPK, S. Saad (2020) 17 Other Constraints ❖ Fixed Target Experiments: Electron beam dump experiments put a severe constraint on the light scalar that has coupling with electrons. ❖ Dark Photon Searches: KLOE collaboration and BaBar collaboration searches for the dark photons 𝑨𝒅 through the process:𝒆+ 𝒆− → 𝜸𝑨𝒅 , with 𝑨𝒅 → 𝒆+ 𝒆− ❖ LEP experiments: 𝒆− 𝒆+ → 𝒇𝒇ത process constrained by the LEP experiments, which can be used to constrain the masses of the neutral scalar and its corresponding coupling with charged fermions. 18 Other Constraints ❖ Dark Photon Searches : For a scalar mass 𝒎𝑯 > 𝟐𝟎𝟎 𝑴𝒆𝑽, the dark-boson searches at the BaBar can be used to impose limits on H µ+ µ− coupling via 𝒆+ 𝒆− → µ+ µ− 𝑯 process. ❖ Rare Z- decay: Exotic Z decay of the type 𝒁 → 4µ has been searched by both the ATLAS and the CMS collaborations. 19 LHC Prospects The most promising signal of the model is 𝒑𝒑 → 𝞽− 𝞽+ 𝒋𝒋 + 𝑬𝑻 at the LHC. If the mass splitting between the CP-even and CP-odd neutral scalars is turned off, then the amplitude for this process will be exactly zero. Correspondingly, our scenario will fail to explain the lepton AMMs At the HL-LHC with an integrated luminosity of 𝟑 𝐚𝐛−𝟏 , the charged scalars of mass up to 282 GeV can be probed. S. Jana, VPK, S. Saad (2020) 20 Muon Anomalous Magnetic Moment and Electron Anomalous Magnetic Moment S. Jana, VPK, S. Saad (2020) 21 Conclusions We have proposed a novel scenario that can explain the anomalies related to the lepton anomalous magnetic moments. We have shown that a light scalar of mass 𝓞 𝟏𝟎 𝑴𝒆𝑽 − 𝓞 𝟏 𝑮𝒆𝑽 can contribute simultaneously to both electron and muon AMM with correct sign and magnitude needed to explain these anomalies. We analyze possible ways to probe new-physics signals at colliders and find that this scenario can be tested at the LHC by looking at the novel process is 𝒑𝒑 → 𝞽− 𝞽+ 𝒋𝒋 + 𝑬𝑻 via same-sign pair production of charged Higgs bosons. Thank You ! 22 Morel, L., Yao, Z., Cladé, P. et al. Nature 588, 61–65 (2020) VISHNU PK 23 Electroweak Precision Constraints ❖ T parameter in the alignment of 2HDM ❖ Our scenario, 𝒎𝟐𝑯 ≪ 𝒎𝟐𝑯+ ≈ 𝒎𝟐𝑨 ∼ 𝓞 𝟏𝟏𝟎 𝑮𝒆𝑽 is well consistent with the EW precision constraints. 24 Fixed Target Experiments ❖Electron beam-dump experiments can probe light scalars that have coupling with the electrons. ❖Light Scalars are produced via 𝒆 + 𝑵 → 𝒆 + 𝑵 + 𝑯 process. ❖For a scalar of mass 𝒎𝑯 < 𝟐𝒎µ , after traveling macroscopic distances, it would decay back to electron pairs. ❖Lack of such events constrain the mass of scalar and its corresponding coupling with the electron. S. Jana, VPK, S. Saad (2020) 25 Dark-photon Searches ❖There are several experiments that search for the presence of dark-photons and their null observations can be translated to provide stringent constraints on the allowed parameter space of light scalars. ❖KLOE collaboration and BaBar collaboration searches for the dark photons 𝑨𝒅 through the process:𝒆+ 𝒆− → 𝜸𝑨𝒅 , with 𝑨𝒅 → 𝒆+ 𝒆− . ❖Lack of such events constrain the mass of scalar and its corresponding coupling with the electron. 26 Dark-photon Searches ❖For a scalar mass 𝒎𝑯 > 𝟐𝟎𝟎 𝑴𝒆𝑽, the dark-boson searches at the BaBar can be used to impose limits on H µ+ µ− coupling via 𝒆+ 𝒆− → µ+ µ− 𝑯 process. . ❖Lack of such events constrain the mass of scalar and its corresponding coupling with the electron. 27 Rare Z-decay constraints ❖Rare Z-decay constraints:– Exotic Z decay of the type 𝒁 → 4µ has been searched by both the ATLAS and the CMS collaborations. ❖The LHC results can be interpreted as constraints on the process 𝒁 → µ+ µ− 𝑯, with 𝑯 → µ+ µ−. 28 LEP constraints ❖𝒆− 𝒆+ → 𝒇𝒇ത process constrained by the LEP experiments, which can be used to constrain the masses of the neutral scalar and its corresponding coupling with charged fermions. 29