Carlini et al. (2023)

[2301.02226] Resolving 𝑅_𝐷 and 𝑅_𝐷^∗ Anomalies in Adjoint SU(5) 
 
 
 
 
 
 
 
 
 
 
 

 
 

 
 
 
 
 
 
 Resolving R D subscript 𝑅 𝐷 R_{D} and R D ∗ subscript 𝑅 superscript 𝐷 R_{D^{*}} Anomalies in Adjoint SU(5)

 
 
 
A. Ismael 1,2 and S. Khalil 2 
 
 1 Physics Department, Faculty of Science, Ain Shams University, Cairo 11566, Egypt.
 
 2 Center for Fundamental Physics, Zewail City of Science and
Technology, 6th of October City, Giza 12578, Egypt.
 
 

 
 Abstract

 We investigate the R D subscript 𝑅 𝐷 R_{D} and R D ∗ subscript 𝑅 superscript 𝐷 R_{D^{*}} anomalies in the context of non-minimal S ​ U ​ ( 5 ) 𝑆 𝑈 5 SU(5) , where Higgs sector is extended by
adjoint 45-dimensional multiplet. One of the light spectrum of this model could be the scalar triplet leptoquark that is contained in this multiplet.
We demonstrate that this particular scalar leptogquark mediation of the transition b → c ​ τ ​ ν → 𝑏 𝑐 𝜏 𝜈 b\to c\tau\nu is capable of simultaneously accounting for both R D subscript 𝑅 𝐷 R_{D} and R D ∗ subscript 𝑅 superscript 𝐷 R_{D^{*}} anomalies. We further emphasize that another Yukawa coupling controls its contribution to b → s ​ ℓ + ​ ℓ − → 𝑏 𝑠 superscript ℓ superscript ℓ b\to s\ell^{+}\ell^{-} , ensuring that R K subscript 𝑅 𝐾 R_{K} and R K ∗ subscript 𝑅 superscript 𝐾 R_{K^{*}} remain consistent with the standard model predictions.

 
 
 
 I Introduction

 
 Semileptonic decays B → { D , D ∗ } ​ τ ​ ν → 𝐵 𝐷 superscript 𝐷 𝜏 𝜈 B\to\{D,D^{*}\}\tau\nu have received a lot of attention in recent years because they provide a good opportunity to test the Standard Model (SM) and look for possible new physics beyond. Recent intriguing measurements of R D , D ∗ subscript 𝑅 𝐷 superscript 𝐷 R_{D,D^{*}} by BaBar [ 2 , 3 ] , Belle [ 4 , 5 , 6 , 7 ] , and LHCb collaborations [ 8 ] are significant hints of new physics that violate lepton flavor universality. The ratios R D , D ∗ subscript 𝑅 𝐷 superscript 𝐷 R_{D,D^{*}} are defined by

 

 
 
 R D ∗ , D ≡ B ​ R ​ ( B q → { D ∗ , D } ​ τ ​ ν ) B ​ R ​ ( B q → { D ∗ , D } ​ l ​ ν ) , subscript 𝑅 superscript 𝐷 𝐷 𝐵 𝑅 → subscript 𝐵 𝑞 superscript 𝐷 𝐷 𝜏 𝜈 𝐵 𝑅 → subscript 𝐵 𝑞 superscript 𝐷 𝐷 𝑙 𝜈 \displaystyle R_{D^{*},D}\equiv\frac{BR(B_{q}\rightarrow\{D^{*},D\}\tau\nu)}{BR(B_{q}\rightarrow\{D^{*},D\}l\nu)}\,, 
 
 (1) 
 
 
 where l = e , μ 𝑙 𝑒 𝜇 l=e,\mu . The current experimental averages of R D subscript 𝑅 𝐷 R_{D} and
 R D ∗ subscript 𝑅 superscript 𝐷 R_{D^{*}} are given by [ 9 ] 

 

 
 
 R D subscript 𝑅 𝐷 \displaystyle R_{D} 
 = 0.339 ± 0.026 ± 0.014 , absent plus-or-minus 0.339 0.026 0.014 \displaystyle=0.339\pm 0.026\pm 0.014\,, 
 
 (2) 
 
 
 
 R D ∗ subscript 𝑅 superscript 𝐷 \displaystyle R_{D^{*}} 
 = 0.295 ± 0.010 ± 0.010 . absent plus-or-minus 0.295 0.010 0.010 \displaystyle=0.295\pm 0.010\pm 0.010\,. 
 
 (3) 
 
 
 However, the SM predictions are given as follows: [ 10 , 11 , 12 ] 

 

 
 
 R D SM superscript subscript 𝑅 𝐷 SM \displaystyle

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