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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2017). Measurement of the e(+)e(-) -> pi(+)pi(-)pi(0)pi(0) cross section using initial-state radiation at BABAR. Phys. Rev. D, 96(9), 092009–17pp.
Abstract: The process e(+)e(-) -> pi(+)pi(-)2 pi(0)gamma is investigated by means of the initial-state radiation technique, where a photon is emitted from the incoming electron or positron. Using 454.3 fb(-1) of data collected around a centerof- mass energy of root s = 10.58 GeV by the BABAR experiment at SLAC, approximately 150000 signal events are obtained. The corresponding nonradiative cross section is measured with a relative uncertainty of 3.6% in the energy region around 1.5 GeV, surpassing all existing measurements in precision. Using this new result, the channel's contribution to the leading order hadronic vacuum polarization contribution to the anomalous magnetic moment of the muon is calculated as (g(mu)(pi+ pi-2 pi 0) – 2)/2 = (17.9 +/- 0.1(stat) +/- 0.6(syst)) x 10(-10) in the energy range 0.85 GeV < ECM < 1.8 GeV. In the same energy range, the impact on the running of the fine-structure constant at the Z(0)-pole is determined as Delta alpha(pi+ pi-2 pi 0) (M-Z(2)) = (4.44 +/- 0.02(stat) +/- 0.14(syst)) x 10(-4). Furthermore, intermediate resonances are studied and especially the cross section of the process e(+)e(-) -> omega pi(0) -> pi(+)pi(-)2 pi(0) is measured.
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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. (2017). Measurement of CP observables in B-+/- -> DK*(+/-) decays using two- and four-body D final states. J. High Energy Phys., 11(11), 156–27pp.
Abstract: Measurements of CP observables in B-+/- -> DK*(+/-) decays are presented, where D denotes a superposition of D-0 and (D) over bar (0) meson states. Decays of the D meson to K-pi(+), K-K+, pi(-)pi(+), K-pi(+)pi(-)pi(+) and pi(-)pi(+)pi(-)pi(+) are used and the K*(+/-) meson is reconstructed in the K-S(0)pi(+/-) final state. This analysis uses a data sample of pp collisions collected with the LHCb experiment, corresponding to integrated luminosities of 1 fb(-1), 2 fb(-1) and 1.8 fb(-1) at centre-of-mass energies root s = 7TeV, 8TeV and 13TeV, respectively. The sensitivity of the results to the CKM angle gamma is discussed.
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Fuster, J., Irles, A., Melini, D., Uwer, P., & Vos, M. (2017). Extracting the top-quark running mass using t$(t)over-bar-$+1-jet events produced at the Large Hadron Collider. Eur. Phys. J. C, 77(11), 794–9pp.
Abstract: We present the calculation of the next-to-leading order QCD corrections for top-quark pair production in association with an additional jet at hadron colliders, using the modified minimal subtraction scheme to renormalize the top- quark mass. The results are compared to measurements at the Large Hadron Collider run I. In particular, we determine the top-quark running mass from a tit of the theoretical results presented here to the LHC data.
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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. (2017). chi(c1) and chi(c2) Resonance Parameters with the Decays chi(c1,c2) -> J/psi mu(+)mu(-). Phys. Rev. Lett., 119(22), 221801–9pp.
Abstract: The decays chi(c1) -> J/psi mu(+)mu(-) and chi(c1) -> J/psi mu(+)mu(-) are observed and used to study the resonance parameters of the chi(c1) and chi(c2) mesons. The masses of these states are measured to be m(chi(c1)) = 3510.71 +/- 0.04(stat) +/- 0.09(syst) MeV and m(chi(c2)) = 3556.10 +/- 0.06(stat) +/- 0.11(syst) MeV, where the knowledge of the momentum scale for charged particles dominates the systematic uncertainty. The momentum-scale uncertainties largely cancel in the mass difference m(chi(c2)) – m(chi(c1)) = 45.39 +/- 0.07(stat) +/- 0.03(syst) MeV. The natural width of the chi(c2) meson is measured to be Gamma(chi(c2)) = 2.10 +/- 0.20(stat) +/- 0.02(syst) MeV. These results are in good agreement with and have comparable precision to the current world averages.
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Lopez-Honorez, L., Mena, O., Palomares-Ruiz, S., & Villanueva-Domingo, P. (2017). Warm dark matter and the ionization history of the Universe. Phys. Rev. D, 96(10), 103539–14pp.
Abstract: In warm dark matter scenarios structure formation is suppressed on small scales with respect to the cold dark matter case, reducing the number of low-mass halos and the fraction of ionized gas at high redshifts and thus, delaying reionization. This has an impact on the ionization history of the Universe and measurements of the optical depth to reionization, of the evolution of the global fraction of ionized gas and of the thermal history of the intergalactic medium, can be used to set constraints on the mass of the dark matter particle. However, the suppression of the fraction of ionized medium in these scenarios can be partly compensated by varying other parameters, as the ionization efficiency or the minimum mass for which halos can host star-forming galaxies. Here we use different data sets regarding the ionization and thermal histories of the Universe and, taking into account the degeneracies from several astrophysical parameters, we obtain a lower bound on the mass of thermal warm dark matter candidates of m(X) > 1.3 keV, or m(s) > 5.5 keV for the case of sterile neutrinos nonresonantly produced in the early Universe, both at 90% confidence level.
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