LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2018). Measurement of Antiproton Production in p-He Collisions at root S-NN=110 GeV. Phys. Rev. Lett., 121(22), 222001–10pp.
Abstract: The cross section for prompt antiproton production in collisions of protons with an energy of 6.5 TeV incident on helium nuclei at rest is measured with the LHCb experiment from a data set corresponding to an integrated luminosity of 0.5 nb(-1). The target is provided by injecting helium gas into the LHC beam line at the LHCb interaction point. The reported results, covering antiproton momenta between 12 and 110 GeV/c, represent the first direct determination of the antiproton production cross section in p-He collisions, and impact the interpretation of recent results on antiproton cosmic rays from space-borne experiments.
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BABAR and Belle Collaborations(Adachi, I. et al), Martinez-Vidal, F., & Oyanguren, A. (2018). First Evidence for cos 2 beta > 0 and Resolution of the Cabibbo-Kobayashi-Maskawa Quark-Mixing Unitarity Triangle Ambiguity. Phys. Rev. Lett., 121(26), 261801–11pp.
Abstract: We present first evidence that the cosine of the CP-violating weak phase 2 beta is positive, and hence exclude trigonometric multifold solutions of the Cabibbo-Kobayashi-Maskawa (CKM) Unitarity Triangle using a time-dependent Dalitz plot analysis of B-0 -> D-(*) h(0) with D -> K-S(0)pi(+)pi(-) decays, where h(0) is an element of {pi(0), eta, omega} denotes a light unflavored and neutral hadron. The measurement is performed combining the final data sets of the BABAR and Belle experiments collected at the (sic)(4S) resonance at the asymmetric-energy B factories PEP-II at SLAC and KEKB at KEK, respectively. The data samples contain (471 +/- 3) x 10(6) B (B) over bar pairs recorded by the BABAR detector and (772 +/- 11) x 10(6) B (B) over bar pairs recorded by the Belle detector. The results of the measurement are sin 2 beta = 0.80 +/- 0.14 (stat) +/- 0.06 (syst) +/- 0.03 (model) and cos 2 beta = 0.91 +/- 0.22(stat) +/- 0.09 (syst) +/- 0.07(model). The result for the direct measurement of the angle beta of the CKM Unitarity Triangle is beta = [22.5 +/- 4.4 (stat) +/- 1.2 (syst) +/- 0.6(model)]degrees. The measurement assumes no direct CP violation in B-0 -> D-(*) h(0) decays. The quoted model uncertainties are due to the composition of the D-0 -> K-S(0)pi(+)pi(-) decay amplitude model, which is newly established by performing a Dalitz plot amplitude analysis using a high-statistics e(+)e(-) -> c (c) over bar data sample. CP violation is observed in B-0 -> D-(*) h(0) decays at the level of 5.1 standard deviations. The significance for cos 2 beta > 0 is 3.7 standard deviations. The trigonometric multifold solution pi/2 – beta = (68.1 +/- 0.7)degrees is excluded at the level of 7.3 standard deviations. The measurement resolves an ambiguity in the determination of the apex of the CKM Unitarity Triangle.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2019). Measurement of the Charm-Mixing Parameter y(CP). Phys. Rev. Lett., 122(1), 011802–10pp.
Abstract: A measurement of the charm-mixing parameter Y-CP using D-0 -> K+K-, D-0 -> pi(+)pi(-), and D-0 -> K-pi(+)decays is reported. The D-0 mesons are required to originate from semimuonic decays of B- and (B) over bar (0)mesons. These decays are partially reconstructed in a data set of proton-proton collisions at center-of-mass energies of 7 and 8 TeV collected with the LHCb experiment and corresponding to an integrated luminosity of 3 fb(-1). The y c p parameter is measured to be (0.57 +/- 0.13(stat) +/- 0.09(syst))%, in agreement with, and as precise as, the current world-average value.
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2019). Observation of the Decay D-0 -> K- pi(+) e(+) e(-). Phys. Rev. Lett., 122(8), 081802–8pp.
Abstract: We report the observation of the rare charm decay D-0 -> K-pi(+)e(+)e(-), based on 468 fb(-1) of e(+)e(-) annihilation data collected at or close to the center-of-mass energy of the (sic)(4S) resonance with the BABAR detector at the SLAC National Accelerator Laboratory. We find the branching fraction in the invariant mass range 0.675 < m(e(+)e(-)) < 0.875 GeV/c(2) of the electron-positron pair to be B(D-0 -> K-pi(+)e(+)e(-)) = (4.0 +/- 0.5 +/- 0.2 +/- 0.1) x 10(-6), where the first uncertainty is statistical, the second systematic, and the third due to the uncertainty in the branching fraction of the decay D-0 -> K-pi(+)pi(+)pi(-) used as a normalization mode. The significance of the observation corresponds to 9.7 standard deviations including systematic uncertainties. This result is consistent with the recently reported D-0 -> K-pi(+)mu(+)mu(-) branching fraction, measured in the same invariant mass range, and with the value expected in the standard model. In a set of regions of m(e(+)e(-)), where long-distance effects are potentially small, we determine a 90% confidence level upper limit on the branching fraction B(D-0 -> K-pi(+)e(+)e(-)) < 3.1 x 10(-6).
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., et al. (2019). Observation of Two Resonances in the Lambda(0)(b)pi(+/-) Systems and Precise Measurement of Sigma(+/-)(b) and Sigma(*+/-)(b) Properties. Phys. Rev. Lett., 122(1), 012001–9pp.
Abstract: The first observation of two structures consistent with resonances in the final states Lambda(0)(b)pi(-) and Lambda(0)(b)pi(+) thorn is reported using samples of pp collision data collected by the LHCb experiment at root s = 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb(-1). The ground states Sigma(+/-)(b) and Sigma(*+/-)(b) are also confirmed and their masses and widths are precisely measured.
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