Wimmer, K. et al, Algora, A., & Rubio, B. (2021). Shape Changes in the Mirror Nuclei Kr-70 and Se-70. Phys. Rev. Lett., 126(7), 072501–6pp.
Abstract: We studied the proton-rich T-z = -1 nucleus Kr-70 through inelastic scattering at intermediate energies in order to extract the reduced transition probability, B(E2; 0+ -> 2+). Comparison with the other members of the A = 70 isospin triplet, Br-70 and Se-70, studied in the same experiment, shows a 3 sigma deviation from the expected linearity of the electromagnetic matrix elements as a function of T-z. At present, no established nuclear structure theory can describe this observed deviation quantitatively. This is the first violation of isospin symmetry at this level observed in the transition matrix elements. A heuristic approach may explain the anomaly by a shape change between the mirror nuclei Kr-70 and Se-70 contrary to the model predictions.
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ATLAS Collaboration(Aad, G. et al), Amoros, G., Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Ferrer, A., et al. (2012). Search for tb Resonances in Proton-Proton Collisions at root s=7 TeV with the ATLAS Detector. Phys. Rev. Lett., 109(8), 081801–19pp.
Abstract: This Letter presents a search for tb resonances in 1.04 fb(-1) of LHC proton-proton collision data collected by the ATLAS detector at a center-of-mass energy of 7 TeV. Events with a lepton, missing transverse momentum, and two jets are selected and the invariant mass of the corresponding final state is reconstructed. The search exploits the shape of the tb invariant mass distribution compared to the expected standard model backgrounds. The model of a right-handed W'(R) with standard model-like couplings is chosen as the benchmark model for this search. No statistically significant excess of events is observed in the data, and upper limits on the cross section times the branching ratio of W'(R) resonances at 95% C.L. lie in the range of 6.1-1.0 pb for W'(R) masses ranging from 0.5 to 2.0 TeV. These limits are translated into a lower bound on the allowed right-handed W'(R) mass, giving mW'(R) > 1.13 TeV at 95% C.L.
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., Oyanguren, A., & Villanueva-Perez, P. (2015). Study of CP Asymmetry in B-0-(B)over-bar(0) Mixing with Inclusive Dilepton Events. Phys. Rev. Lett., 114(8), 081801–8pp.
Abstract: We present a measurement of the asymmetry A(CP) between same- sign inclusive dilepton samples l(+) l(+) and l(-) l(-) ( l = e, mu) from semileptonic B decays in Y(4S) -> B (B) over bar events, using the complete data set recorded by the BABAR experiment near the Y(4S) resonance, corresponding to 471 x 10(6) B (B) over bar pairs. The asymmetry A(CP) allows comparison between the mixing probabilities P((B) over bar (0) -> B-0) and P(B-0 -> (B) over bar (0)) and therefore probes CP and T violation. The result, A(CP) = [-3.9 +/- 3.5(stat) +/- 1.9(syst)] x 10(-3), is consistent with the standard model expectation.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., Ruiz Valls, P., et al. (2017). Observation of the Annihilation Decay Mode B-0 -> K+K-. Phys. Rev. Lett., 118(8), 081801–9pp.
Abstract: A search for the B-0 -> K+K- decay is performed using pp-collision data collected by LHCb. The data set corresponds to integrated luminosities of 1.0 and 2.0 fb(-1) at center-of-mass energies of 7 and 8 TeV, respectively. This decay is observed for the first time, with a significance of more than 5 standard deviations. The analysis also results in an improved measurement of the branching fraction for the B-s(0) -> pi(+)pi(-) decay. The measured branching fractions are B(B-0 -> K+K-) = (7.80 +/- 1.27 +/- 0.81 +/- 0.21) x 10(-8) and B(B-s(0) -> pi(+)p(-)) = (6.91 +/- 0.54 +/- 0.63 +/- 0.19 +/- 0.40) x 10(-7). The first uncertainty is statistical, the second is systematic, the third is due to the uncertainty on the B-0 -> K+pi(-) branching fraction used as a normalization. For the B-s(0) mode, the fourth accounts for the uncertainty on the ratio of the probabilities for b quarks to hadronize into B-s(0) and B-0 mesons.
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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Bailey, A. J., Barranco Navarro, L., Cabrera Urban, S., Castillo Gimenez, V., et al. (2018). Search for Low-Mass Dijet Resonances Using Trigger-Level Jets with the ATLAS Detector in pp Collisions at root s=13 TeV. Phys. Rev. Lett., 121(8), 081801–20pp.
Abstract: Searches for dijet resonances with sub-TeV masses using the ATLAS detector at the Large Hadron Collider can be statistically limited by the bandwidth available to inclusive single-jet triggers, whose data-collection rates at low transverse momentum are much lower than the rate from standard model multijet production. This Letter describes a new search for dijet resonances where this limitation is overcome by recording only the event information calculated by the jet trigger algorithms, thereby allowing much higher event rates with reduced storage needs. The search targets low-mass dijet resonances in the range 450-1800 GeV. The analyzed data set has an integrated luminosity of up to 29.3 fb(-1) and was recorded at a center-of-mass energy of 13 TeV. No excesses are found; limits are set on Gaussian-shaped contributions to the dijet mass distribution from new particles and on a model of dark-matter particles with axial-vector couplings to quarks.
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