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LHCb Collaboration(Aaij, R. et al), Fernandez Casani, A., Jaimes Elles, S. J., Libralon, S., Lucio Martinez, M., Martinez-Vidal, F., et al. (2026). CP Violation Analysis of Local and Nonlocal Amplitudes in the (B)over-bar0 → (K)over-bar*0μ+μ- Decay. Phys. Rev. Lett., 137(6), 061801–12pp.
Abstract: A search for CP violation in the (B) over bar (0) -> (K) over bar*(0)mu(+)mu(-) decay is performed using proton-proton collision data collected by the LHCb experiment during Run 1 and Run 2, corresponding to an integrated luminosity of 8.4 fb(-1). The analysis exploits the full angular distribution of the decay, providing sensitivity to CP-violating effects in both vector and axial-vector contributions to this flavor-changing neutral-current process. The complex Wilson coefficients are determined within the weak effective theory through an unbinned maximum-likelihood fit to the angular observables, incorporating nonlocal hadronic amplitudes across the full dimuon mass spectrum. The precision of the CP-violation observables is improved by an order of magnitude relative to previous measurements, with the imaginary parts of the Wilson coefficients now determined more precisely than the real parts. No significant CP violation is observed, and the results are consistent with the standard model.
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LHCb Collaboration(Aaij, R. et al), Fernandez Casani, A., Jaimes Elles, S. J., Jashal, B. K., Libralon, S., Lucio Martinez, M., et al. (2026). Evidence for the Rare Decay B+ → (Λ)over-barpμ+ μ-. Phys. Rev. Lett., 137(5), 051801–13pp.
Abstract: A search for the rare decay B+ -> (Lambda) over barp mu(+) mu(-) is performed using proton-proton collision data recorded by the LHCb experiment at a center-of-mass energy of root s = 13 TeV, corresponding to an integrated luminosity of 5.4 fb(-1). An excess of events is found with respect to the background-only expectation, with a signal significance of 3.5 standard deviations, in the low invariant-mass region of m((Lambda) over barp) < 2.8 GeV/c(2). The branching fraction is measured to be B-low(B+ -> <(Lambda)over bar>p mu(+) mu(-)) = (1.70(-0.56)(+0.65)(stat) +/- 0.17(syst)+/- 0.14(ext)) x 10(-8), where the last uncertainty is due to external inputs on B(B+ -> J/psi(Lambda) over barp) x B(J/psi -> mu(+) mu(-)). With no significant signal observed in the high m((Lambda) over barp) region above 2.8 GeV/c(2), an upper limit is set to be B-high(B+ -> (Lambda) over barp mu(+) mu(-)) < 2.8(3.7) x 10(-9) at the 90% (95%) confidence level.
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Wang, D. (2026). Possible evidences for cosmological massive neutrinos. Eur. Phys. J. Plus, 141(9), 1068–7pp.
Abstract: A key question in cosmology is whether massive neutrinos exist on cosmic scales. Current cosmological observations have severely compressed the viable range for neutrino masses and even prefer phenomenologically an effective negative mass. This poses a great challenge to the cosmological search for neutrinos. Based on current background and large scale structure data, taking a full red-shift and/or scale tomography method, we obtain one beyond 5 sigma , two 3 sigma , and two 2 sigma evidences of massive neutrinos, spanning both high and low red-shifts, as well as both small and intermediate scales. Specifically, for the case of red-shift tomography, we find the neutrino mass sum Sigma m nu 1=1.01-0.58+0.47 eV in z is an element of[0,1] using the data combination of CMB, BAO, and supernova, indicating a 2 sigma clue of nonzero neutrino mass, while the addition of WiggleZ galaxy power spectrum leads to Sigma m nu 1=0.65 +/- 0.25 eV, implying a 3 sigma evidence of massive neutrinos. For the case of scale tomography, we give Sigma m nu k1=0.75-0.27+0.20 eV in k is an element of[10-1,+infinity) h Mpc -1 using the combination of CMB and WiggleZ observations, revealing a beyond 5 sigma evidence of massive neutrinos at small scales, while combining CMB with DESY1 galaxy clustering, cosmic shear and galaxy-galaxy lensing data provides Sigma m nu k2=0.55 +/- 0.27 eV in k is an element of[10-2,10-1] h Mpc -1 , giving a 2 sigma hint at intermediate scales. For the case of red-shift and scale tomography, we obtain Sigma m nu 52=0.63-0.24+0.20 eV when z is an element of[100,1100] and k is an element of[10-2,10-1] h Mpc -1 , suggesting a similar to 3 sigma evidence of massive neutrinos. Interestingly, these five signals of nonzero neutrino masses are well consistent within 1 sigma confidence level, indicating a possible suppression of neutrino mass during the evolution of the universe. Using cosmic microwave background observations to constrain a red-shift and scale dependent neutrino mass, we make the first neutrino mass map through the cosmic history and full scales for future high-precision search. Our results could help understand the role massive neutrinos played in the evolution of the universe.
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Super-FRS Experiment Collaboration(Ayet, S. et al), & Algora, A. (2026). Direct mass measurement of 91Rh and 89Ru and mid-shell trend of the one-proton separation energies for N = Z+1 nuclei. Phys. Rev. C, 114(3), 034311–13pp.
Abstract: Neutron-deficient nuclei in the N approximate to Z, A approximate to 90 region were produced by fragmentation of a relativistic 107Ag beam at the GSI Helmholtz Centre for Heavy Ion Research (GSI), separated in the fragment separator FRS, slowed down, and thermalized, and high-precision mass measurements were performed employing the multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS) of the FRS Ion Catcher. The masses of 91,93,95Rh, 89Ru, 88Tc, 87,88,89Mo, and 87,88,89Nb were determined. The mass of 91Rh was measured for the first time. For 89Ru, the measured mass excess deviates by more than ten standard deviations (361 keV) from the previous measurement. A possible misidentification of the measured nuclei, including 89Ru, with contaminants was excluded using a newly developed identification technique for MR-TOF-MS measurements. For the other nuclides, the measured masses agree well with previous measurements. The impact of the new masses on the one-proton separation energy (Sp) of the nuclei with constant total isospin projection (Tz) in the island of inversion around N = Z = 40 is investigated, and signatures of the deformed shell gap at Z = 38 are found. A comparison of the experimental Sp values with the predictions of several mass models shows a general agreement of the trends.
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LHCb Collaboration(Aaij, R. et al), Fernandez Casani, A., Jaimes Elles, S. J., Libralon, S., Lucio Martinez, M., Martinez-Vidal, F., et al. (2026). Search for the Lepton-Flavor Violating Decays B+ → π+ μ± e∓. Phys. Rev. Lett., 137(6), 061802–13pp.
Abstract: The first search for the lepton-flavor violating decays B+ -> pi(+) mu(+/-) e(-/+) in proton-proton collisions is presented, using data collected by the LHCb experiment between 2011 and 2018, corresponding to an integrated luminosity of 9 fb(-1). No significant signal is observed and an upper limit on the branching fraction is set at B(B+ -> pi(+) mu(+/-) e(-/+)) < 1.8 x 10(-9) at the 90% confidence level, 2 orders of magnitude more restrictive than the most stringent upper limit to date. This is the first constraint on lepton-flavor violating b -> d quark transitions at the LHC and also sets the most stringent upper limits to date on b -> d mu(+/-)e(-/+) transitions. Limits on left-handed and scalar scenarios beyond the standard model are also reported.
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