210 research outputs found

    Dark Z implication for flavor physics

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    Dark ZZ/dark photon (ZZ') is one candidate of dark force carrier, which helps to interpret the properties of dark matter (DM). Other than traditional studies of DM including direct detection, indirect detection and collider simulation, in this work we take flavor physics as a complementary approach to investigate the features of dark matter. We give an exact calculation of the new type of penguin diagram induced by ZZ' which further modifies the well-known X,Y,ZX, Y, Z functions in penguin-box expansion. The measurement of rare decays BK()μ+μB\to K^{(*)}\mu^+\mu^- and Bsμ+μB_s\to \mu^+\mu^- at LHC, together with direct CP violation ε/ε\varepsilon'/\varepsilon in KππK\to\pi \pi as well as KLμ+μK_L\to\mu^+\mu^-, are used to determine the parameter space. The size of coupling constant, however, is found to be O(1)\mathcal{O}(1) which is much weaker than the known constraints.Comment: 13 pages, 3 figures; For V2 typo corrected, references added, published in JHE

    Correlating Bq0μ+μB_q^0 \to \mu^+\mu^- and KLπ0ννˉK_L \to \pi^0\nu\bar\nu Decays with Four Generations

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    The long-awaited Bsμ+μB_s\to \mu^+\mu^- mode has finally been observed at rate consistent with Standard Model, albeit lower by 1.2σ\sigma. There is some hint for New Physics in the rarer Bd0μ+μB_d^0 \to \mu^+\mu^- decay, especially if the currently 2.2σ\sigma-enhanced central value persists with more data. The measurement of CPCP violating phase ϕs\phi_s, via both BsJ/ψKKˉB_s\to J/\psi K\bar K and J/ψππJ/\psi\pi\pi modes, has reached Standard Model sensitivity. These measurements stand major improvement when LHC enters Run 2. Concurrently, the KLπ0ννˉK_L\to\pi^0\nu\bar\nu and K+π+ννˉK^+\to\pi^+\nu\bar\nu modes are being pursued in a similar time frame. We illustrate the possible correlations between New Physics effects in these four modes, using the fourth generation as example. While correlations may or may not exist in other New Physics models, the four generation model can accommodate enhancements in both Bd0μ+μB_d^0 \to \mu^+\mu^- and KLπ0ννˉK_L\to\pi^0\nu\bar\nu.Comment: 9 pages, 5 figures for V1; for V2 title modified, minor changes performed to figures, part of contents revised to 7 pages, note added, one of the authors' affiliation changed, accepted for the publication of PL

    Matter Effects of Sterile Neutrino in Light of Renormalization-Group Equations

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    The renormalization-group equation (RGE) approach to neutrino matter effects is further developed in this work. We derive a complete set of differential equations for effective mixing elements, masses and Jarlskog-like invariants in presence of a light sterile neutrino. The evolutions of mixing elements as well as Jarlskog-like invariants are obtained by numerically solving these differential equations. We calculate terrestrial matter effects in long-baseline (LBL) experiments, taking NOvA, T2K and DUNE as examples. In both three-flavor and four-flavor frameworks, electron-neutrino survival probabilities as well as the day-night asymmetry of solar neutrino are also evaluated as a further examination of the RGE approach.Comment: 18 pages, 3 figures, 1 table; 22 pages, the version accepted by JHE

    The Global Fits of New Physics in bsb \to s after RK()R_{K^{(*)}} 2022 Release

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    The measurement of lepton universality parameters RK()R_{K^{(*)}} was updated by LHCb in December 2022, which indicated that the well-known anomalies in flavor-changing neutral current (FCNC) processes of B meson decays have faded away. However, does this mean that all new physics possibilities related to bs+b\to s\ell^+\ell^- have been excluded? We aim to answer this question in this work. The state-of-the-art effective Hamiltonian is adopted to describe bsb \to s transition, while BSM (beyond the Standard Model) new physics effects are encoded in Wilson coefficients (WCs). Using around 200 observables in leptonic and semileptonic decays of B mesons and bottom baryons, measured by LHCb, CMS, ATLAS, Belle, and BaBar, we perform global fits of these Wilson coefficients in four different scenarios. In particular, lepton flavors in WCs are specified in some of the working scenarios. To see the change of new physics parameters, we use both the data before and after the 2022 release of RK()R_{K^{(*)}} in two separate sets of fits. We find that in all four scenarios, ΔC9μ\Delta C_9^\mu still has a deviation more than 4σ4\sigma from the Standard Model. At the 1σ1\sigma level, the lepton flavor in WCs is distinguishable for ΔC9,S,P\Delta C_{9, S, P} but indistinguishable for ΔC10\Delta C_{10}. We demonstrate numerically that there is no chirality for muon type of scalar operator and it is kept at the 1σ1\sigma level for their electron type dual ones, while chiral difference exists for O9,10μ\mathcal{O}_{9,10}^\mu at least at the 2σ2\sigma level.Comment: 36 pages, 27 figure