# Physical Review Letters (APS)

 2019-01-1818:18 Precise Determination of the Branching Ratio of the Neutral-Pion Dalitz Decay / Husek, Tomáš ; Goudzovski, Evgueni ; Kampf, Karol We provide a new value for the ratio $R=\Gamma \left({\pi }^{0}\to {e}^{+}{e}^{-}\gamma \left(\gamma \right)\right)/\Gamma \left({\pi }^{0}\to \gamma \gamma \right)=11.978\left(6\right)×{10}^{-3}$, which is by 2 orders of magnitude more precise than the current Particle Data Group average. [...] Published in Physical Review Letters 122 (2019) 10.1103/PhysRevLett.122.022003 arXiv:1809.01153 Fulltext: XML PDF; 2019-01-1518:16 Light-Neutrino Exchange and Long-Distance Contributions to $0\nu 2\beta$ Decays: An Exploratory Study on $\pi \pi \to ee$ / Feng, Xu ; Jin, Lu-Chang ; Tuo, Xin-Yu ; Xia, Shi-Cheng We present an exploratory lattice QCD calculation of the neutrinoless double beta decay $\pi \pi \to ee$. [...] Published in Physical Review Letters 122 (2019) 10.1103/PhysRevLett.122.022001 arXiv:1809.10511 Fulltext: XML PDF; 2019-01-1518:16 Search for ${K}_{L}\to {\pi }^{0}\nu \overline{\nu }$ and ${K}_{L}\to {\pi }^{0}{X}^{0}$ Decays at the J-PARC KOTO Experiment / Ahn, J. K. ; Beckford, B. ; Beechert, J. ; Bryant, K. ; et al A search for the rare decay ${K}_{L}\to {\pi }^{0}\nu \overline{\nu }$ was performed. [...] Published in Physical Review Letters 122 (2019) 10.1103/PhysRevLett.122.021802 arXiv:1810.09655 Fulltext: XML PDF; 2019-01-1422:16 Search for the Higgs Boson Decaying to Two Muons in Proton-Proton Collisions at $\sqrt{s}=13\text{}\text{}\mathrm{TeV}$ / Sirunyan, A. M. ; Tumasyan, A. ; Adam, W. ; Ambrogi, F. ; et al A search for the Higgs boson decaying to two oppositely charged muons is presented using data recorded by the CMS experiment at the CERN LHC in 2016 at a center-of-mass energy $\sqrt{s}=13\text{}\text{}\mathrm{TeV}$, corresponding to an integrated luminosity of $35.9\text{}\text{}{\mathrm{fb}}^{-1}$. [...] Published in Physical Review Letters 122 (2019) 10.1103/PhysRevLett.122.021801 arXiv:1807.06325 Fulltext: PDF XML; 2019-01-1116:18 Importance of Loop Effects in Explaining the Accumulated Evidence for New Physics in $B$ Decays with a Vector Leptoquark / Crivellin, Andreas ; Greub, Christoph ; Saturnino, Francesco ; Müller, Dario In recent years experiments revealed intriguing hints for new physics (NP) in $B$ decays involving $b\to c\tau \nu$ and $b\to s{\ell }^{+}{\ell }^{-}$ transitions at the $4\sigma$ and $5\sigma$ level, respectively. [...] Published in Physical Review Letters 122 (2019) 10.1103/PhysRevLett.122.011805 arXiv:1807.02068 Fulltext: XML PDF; 2019-01-1116:17 Observation of Two Resonances in the ${\Lambda }_{b}^{0}{\pi }^{±}$ Systems and Precise Measurement of ${\Sigma }_{b}^{±}$ and ${\Sigma }_{b}^{*±}$ Properties / Aaij, R. ; Abellán Beteta, C. ; Adeva, B. ; Adinolfi, M. ; et al The first observation of two structures consistent with resonances in the final states ${\Lambda }_{b}^{0}{\pi }^{-}$ and ${\Lambda }_{b}^{0}{\pi }^{+}$ is reported using samples of $pp$ collision data collected by the LHCb experiment at $\sqrt{s}=7$ and 8 TeV, corresponding to an integrated luminosity of $3\text{}\text{}{\mathrm{fb}}^{-1}$. [...] Published in Physical Review Letters 122 (2019) 10.1103/PhysRevLett.122.012001 arXiv:1809.07752 Fulltext: XML PDF; 2019-01-1116:17 Spectrum of Majorana Quantum Mechanics with $O\left(4{\right)}^{3}$ Symmetry / Pakrouski, Kiryl ; Klebanov, Igor R. ; Popov, Fedor ; Tarnopolsky, Grigory We study the quantum mechanics of three-index Majorana fermions ${\psi }^{abc}$ governed by a quartic Hamiltonian with $O\left(N{\right)}^{3}$ symmetry. [...] Published in Physical Review Letters 122 (2019) 10.1103/PhysRevLett.122.011601 arXiv:1808.07455 Fulltext: XML PDF; 2019-01-1116:17 Search for Dark Matter Particles Produced in Association with a Top Quark Pair at $\sqrt{s}=13\text{}\text{}\mathrm{TeV}$ / Sirunyan, A. M. ; Tumasyan, A. ; Adam, W. ; Ambrogi, F. ; et al A search is performed for dark matter particles produced in association with a top quark pair in proton-proton collisions at $\sqrt{s}=13\text{}\text{}\mathrm{TeV}$. [...] Published in Physical Review Letters 122 (2019) 10.1103/PhysRevLett.122.011803 arXiv:1807.06522 Fulltext: PDF XML; 2019-01-1116:17 Measurement of the Charm-Mixing Parameter ${y}_{CP}$ / Aaij, R. ; Abellán Beteta, C. ; Adeva, B. ; Adinolfi, M. ; et al A measurement of the charm-mixing parameter ${y}_{CP}$ using ${D}^{0}\to {K}^{+}{K}^{-}$, ${D}^{0}\to {\pi }^{+}{\pi }^{-}$, and ${D}^{0}\to {K}^{-}{\pi }^{+}$ decays is reported. [...] Published in Physical Review Letters 122 (2019) 10.1103/PhysRevLett.122.011802 arXiv:1810.06874 Fulltext: XML PDF; 2019-01-1116:17 Stability of de Sitter Spacetime against Infrared Quantum Scalar Field Fluctuations / Moreau, G. ; Serreau, J. We study the backreaction of superhorizon fluctuations of a light quantum scalar field on a classical de Sitter geometry by means of the Wilsonian renormalization group. [...] Published in Physical Review Letters 122 (2019) 10.1103/PhysRevLett.122.011302 arXiv:1808.00338 Fulltext: XML PDF;