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1. Flavor at FASER: discovering light scalars beyond minimal flavor violation

   https://doi.org/10.1007/JHEP04(2025)071  

   Balkin, Reuven; Burger, Noam; Feng, Jonathan L; Shadmi, Yael (April 2025, Journal of High Energy Physics)

   A<sc>bstract</sc> We study a simple class offlavored scalarmodels, in which the couplings of a new light scalar to standard-model fermions are controlled by the flavor symmetry responsible for fermion masses and mixings. The scalar couplings are then aligned with the Yukawa matrices, with small but nonzero flavor-violating entries.D-meson decays are an important source of scalar production in these models, in contrast to models assuming minimal flavor violation, in whichBandKdecays dominate. We show that FASER2 can probe large portions of the parameter space of the models, with comparable numbers of scalars fromBandDdecays in some regions. If discovered, these particles will not only provide evidence of new physics, but they may also shed new light on the standard model flavor puzzle. Finally, the richness of theoretical models underscores the importance of model-independent interpretations. We therefore analyze the sensitivity of FASER and other experimental searches in terms of physical parameters: (i) the branching fractions of heavy mesons to the scalar, and (ii)τ/m, whereτandmare the scalar’s lifetime and mass, respectively. The results are largely independent of the new particle’s spin and can be used to extract constraints on a wide variety of models. 

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2. Two-flavor adjoint QCD

   https://doi.org/10.1103/PhysRevD.98.034026  

   Anber, Mohamed M.; Poppitz, Erich (August 2018, Physical Review D)
3. Flavor diagonal nucleon charges

   https://doi.org/10.22323/1.396.0558  

   Park, Sungwoo; Bhattacharya, Tanmoy; Gupta, Rajan; Lin, Huey-Wen; Mondal, Santanu; Yoon, Boram; Zhang, Rui (May 2022, The 38th International Symposium on Lattice Field Theory (LATTICE2021))
4. The flavor of cosmology

   https://doi.org/10.1088/1475-7516/2018/07/056  

   Lillard, Benjamin; Ratz, Michael; Tait, Tim M.P.; Trojanowski, Sebastian (July 2018, Journal of Cosmology and Astroparticle Physics)
5. Isovector and flavor diagonal charges of the nucleon from 2+1+1 flavor QCD

   https://doi.org/10.22323/1.334.0131  

   Gupta, Rajan; Bhattacharya, Tanmoy; Cirigliano, Vincenzo; Yoon, Boram; Jang, Yong-Chull; Lin, Huey-Wen (May 2019, The 36th Annual International Symposium on Lattice Field Theory (LATTICE2018))

   We present high-statistics results for the isovector and flavor diagonal charges of the proton using 11 ensembles of 2+1+1 flavor HISQ fermions. In the isospin symmetric limit, results for the neutron are given by the $$u \leftrightarrow d$$ interchange. A chiral-continuum fit with leading order corrections was made to extract the connected and disconnected contributions in the continuum limit and at $$M_\pi=135$$~MeV. All results are given in the $$\overline{MS}$$ scheme at 2~GeV. The isovector charges, $$g_A^{u-d} = 1.218(25)(30)$$, $$g_S^{u-d} = 1.022(80)(60) $$ and $$g_T^{u-d} = 0.989(32)(10)$$, are used to obtain low-energy constraints on novel scalar and tensor interactions, $$\epsilon_{S}$$ and $$\epsilon_{T}$$, at the TeV scale. The flavor diagonal axial charges are: $$g_A^u \equiv \Delta u \equiv \langle 1 \rangle_{\Delta u^+} = 0.777(25)(30)$$, $$g_A^d \equiv \Delta d \equiv \langle 1 \rangle_{\Delta d^+} = -0.438(18)(30)$$, and $$g_A^s \equiv \Delta s \equiv \langle 1 \rangle_{\Delta s^+} = -0.053(8)$$. Their sum gives the total quark contribution to the proton spin, $$\sum_{q=u,d,s} (\frac{1}{2} \Delta q) = 0.143(31)(36)$$. This result is in good agreement with the recent COMPASS analysis $$0.13 < \frac{1}{2} \Delta \Sigma < 0.18$$. Implications of results for the flavor diagonal tensor charges, $$g_T^u = 0.784(28)(10)$$, $$g_T^d = -0.204(11)(10)$$ and $$g_T^s = -0.0027(16)$$ for constraining the quark electric dipole moments and their contributions to the neutron electric dipole moment are discussed. These flavor diagonal charges also give the strength of the interaction of dark matter with nucleons via axial and tensor mediators. 

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