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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 suppressed decay Lambda(0)(b) -> p pi(-) mu(+) mu(-). J. High Energy Phys., 04(4), 029–16pp.
Abstract: The suppressed decay Lambda(0)(b) -> p pi(-) mu(+) mu(-), excluding the J/psi and psi(2S) -> mu(+) mu(-) resonances, is observed for the first time with a significance of 5.5 standard deviations. The analysis is performed with proton- proton collision data corresponding to an integrated luminosity of 3 fb(-1) collected with the LHCb experiment. The Lambda(0)(b) -> p pi(-) mu(+) mu(-) branching fraction is measured relative to the Lambda(0)(b) -> J/psi (-> mu(+) mu(-)) p pi(-) branching fraction giving B (Lambda(0)(b) -> p pi(-) mu(+) mu(-))/B(Lambda(0)(b) -> J/psi (-> mu(+) mu(-)) p pi(-)) = 0.044 +/- 0.012 +/- 0.007, where the first uncertainty is statistical and the second is systematic. This is the first observation of a b -> d transition in a baryonic decay.
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Albaladejo, M., Daub, J. T., Hanhart, C., Kubis, B., & Moussallamd, B. (2017). How to employ (B)over-bar(d)(0) -> J/psi(pi eta, (K)over-barK) decays to extract information on pi eta scattering. J. High Energy Phys., 04(4), 010–28pp.
Abstract: We demonstrate that dispersion theory allows one to deduce crucial information on pi eta scattering from the final-state interactions of the light mesons visible in the spectral distributions of the decays (B) over bar (0)(d) -> J/psi(pi(0)eta, K+K-, K-0 (K) over bar (0)). Thus high-quality measurements of these differential observables are highly desired. The corresponding rates are predicted to be of the same order of magnitude as those for (B) over bar (0)(d) -> J/psi pi(+)pi(-) measured recently at LHCb, letting the corresponding measurement appear feasible.
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Pich, A., Rosell, I., Santos, J., & Sanz-Cillero, J. J. (2017). Fingerprints of heavy scales in electroweak effective Lagrangians. J. High Energy Phys., 04(4), 012–60pp.
Abstract: The couplings of the electroweak effective theory contain information on the heavy-mass scales which are no-longer present in the low-energy Lagrangian. We build a general effective Lagrangian, implementing the electroweak chiral symmetry breaking SU(2)(L) circle times SU(2)(R) -> SU(2)(L+R), which couples the known particle fields to heavier states with bosonic quantum numbers J(P) = 0(+/-) and 1(+/-). We consider colour-singlet heavy fields that are in singlet or triplet representations of the electroweak group. Integrating out these heavy scales, we analyze the pattern of low-energy couplings among the light fields which are generated by the massive states. We adopt a generic non-linear realization of the electroweak symmetry breaking with a singlet Higgs, without making any assumption about its possible doublet structure. Special attention is given to the different possible descriptions of massive spin-1 fields and the differences arising from naive implementations of these formalisms, showing their full equivalence once a proper short-distance behaviour is required.
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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Barranco Navarro, L., Cabrera Urban, S., Castillo Gimenez, V., Cerda Alberich, L., et al. (2017). Measurement of the inclusive cross-sections of single top-quark and top-antiquark t-channel production in pp collisions at root s=13 TeV with the ATLAS detector. J. High Energy Phys., 04(4), 086–41pp.
Abstract: A measurement of the t-channel single-top-quark and single-top-antiquark production cross-sections in the lepton+jets channel is presented, using 3.2 fb(-1) of proton-proton collision data at a centre-of-mass energy of 13 TeV, recorded with the ATLAS detector at the LHC in 2015. Events are selected by requiring one charged lepton (electron or muon), missing transverse momentum, and two jets with high transverse momentum, exactly one of which is required to be b-tagged. Using a binned maximum-likelihood fit to the discriminant distribution of a neural network, the cross-sections are determined to be sigma(tq) = 156 +/- 5 (stat.) +/- 27 (syst.) +/- 3 (lumi.) pb for single top-quark production and sigma((t) over barq) = 91 +/- 4 (stat.) +/- 18 (syst.) +/- 2 (lumi.) pb for single top-antiquark production, assuming a top-quark mass of 172.5 GeV. The cross-section ratio is measured to be R-t = sigma(tq) / sigma((t) over barq) = 1.72 +/- 0.09 (stat.) +/- 0.18 (syst.). All results are in agreement with Standard Model predictions.
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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). Evidence for the two-body charmless baryonic decay B+ -> p(Lambda)over-bar. J. High Energy Phys., 04(4), 162–18pp.
Abstract: A search for the rare two-body charmless baryonic decay B+ -> p (Lambda) over bar is performed with pp collision data, corresponding to an integrated luminosity of 3 fb(-1), collected by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. An excess of B+ -> p (Lambda) over bar candidates with respect to background expectations is seen with a statistical significance of 4.1 standard deviations, and constitutes the first evidence for this decay. The branching fraction, measured using the B+ -> K-S(0)pi(+) decay for normalisation, is B(B+ -> p (Lambda) over bar) = (2.4(-0.8)(+)(+1.0) +/- 0.3) x 10(-7), where the first uncertainty is statistical and the second systematic.
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