Aceti, F., Xie, J. J., & Oset, E. (2015). The K(K)over-bar pi decay of the f(1) (1285) and its nature as a K*(K)over-bar – cc molecule. Phys. Lett. B, 750, 609–614.
Abstract: We investigate the decay of f(1) (1285) > pi K (K) over bar with the assumption that the f(1) (1285) is dynamically generated from the K*(K) over bar – cc interaction. In addition to the tree level diagrams that proceed via f(1)(1285) -> K*(K) over bar – cc -> pi K (K) over bar, we take into account also the final state interactions of K (K) over bar -> K (K) over bar and pi K -> pi K. The partial decay width and mass distributions of f(1) (1285) -> pi K (K) over bar are evaluated. We get a value for the partial decay width which, within errors, is in fair agreement with the experimental result. The contribution from the tree level diagrams is dominant, but the final state interactions have effects in the mass distributions. The predicted mass distributions are significantly different from phase space and tied to the K*(K) over bar – cc nature of the f(1) (1285) state.
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ATLAS Collaboration(Aad, G. et al), Alvarez Piqueras, D., Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Fernandez Martinez, P., et al. (2015). Measurement of the branching ratio Gamma(Lambda(0)(b) -> Psi(2S)Lambda(0))/ Gamma(Lambda(0.)(b) -> J/Psi Lambda(0)) with the ATLAS detector. Phys. Lett. B, 751, 63–80.
Abstract: An observation of the Lambda(0)(b) -> Psi (2S) Lambda(0) decay and a comparison of its branching fraction with that of the Lambda(0)(b) -> Psi (2S) Lambda(0) decay has been made with the ATLAS detector in proton-proton collisions at root s = 8 TeVat the LHC using an integrated luminosity of 20.6fb(-1). The J/Psi and Psi(2S) mesons are reconstructed in their decays to a muon pair, while the Lambda(0) -> p pi(-) decay is exploited for the Lambda(0) 0baryon reconstruction. The Lambda(0)(b) baryons are reconstructed with transverse momentum p(T)> 10 GeVand pseudorapidity vertical bar eta vertical bar < 2.1. The measured branching ratio of the Lambda(0)(b) -> Psi (2S) Lambda(0) and Lambda(0)(b) -> Psi (2S) Lambda(0) decays is Gamma(Lambda(0)(b) -> Psi (2S) Lambda(0)) / Gamma(Lambda(0)(b) -> Psi (2S) Lambda(0)) = 0.501 +/- 0.033(stat) +/- 0.019(syst), lower than the expectation from the covariant quark model.
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Ruiz-Femenia, P., & Zahiri-Abyaneh, M. (2015). On the minimality of the order p(6) chiral Lagrangian. Phys. Lett. B, 751, 256–261.
Abstract: A method to find relations between the operators in the mesonic Lagrangian of Chiral Perturbation Theory at order p(6) is presented. The procedure can be used to establish if the basis of operators in the Lagrangian is minimal. As an example, we apply the method to the two-flavor case in the absence of scalar and pseudo-scalar sources (s = p = 0), and conclude that the minimal Lagrangian contains 27 independent operators.
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ATLAS Collaboration(Aad, G. et al), Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Ferrer, A., Fiorini, L., et al. (2015). Measurement of the production of neighbouring jets in lead-lead collisions at root s(NN)=2.76TeV with the ATLAS detector. Phys. Lett. B, 751, 376–395.
Abstract: This Letter presents measurements of correlated production of nearby jets in Pb+Pb collisions at root s(NN) = 2.76 TeV using the ATLAS detector at the Large Hadron Collider. The measurement was performed using 0.14 nb(-1)of data recorded in 2011. The production of correlated jet pairs was quantified using the rate, R-Delta R, of “neighbouring” jets that accompany “test” jets within a given range of angular distance, Delta R, in the pseudorapidity-azimuthal angle plane. The jets were measured in the ATLAS calorimeter and were reconstructed using the anti-ktalgorithm with radius parameters d = 0.2, 0.3, and 0.4. R-Delta R was measured in different Pb+Pbcollision centrality bins, characterized by the total transverse energy measured in the forward calorimeters. Acentrality dependence of R-Delta R is observed for all three jet radii with R-Delta R found to be lower in central collisions than in peripheral collisions. The ratios formed by the R-Delta R values in different centrality bins and the values in the 40-80% centrality bin are presented.
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Rinaldi, M., Scopetta, S., Traini, M., & Vento, V. (2016). Double parton scattering: A study of the effective cross section within a Light-Front quark model. Phys. Lett. B, 752, 40–45.
Abstract: We present a calculation of the effective cross section sigma(eff), an important ingredient in the description of double parton scattering in proton-proton collisions. Our theoretical approach makes use of a Light-Front quark model as a framework to calculate the double parton distribution functions at low-resolution scale. QCD evolution is implemented to reach the experimental scale. The obtained values of sigma(eff) in the valence region are consistent with the present experimental scenario, in particular with the sets of data which include the same kinematical range. However the result of the complete calculation shows a dependence of sigma(eff) on x(i), a feature not easily seen in the available data, probably because of their low accuracy. Measurements of sigma(eff) in restricted x(i) regions are addressed to obtain indications on double parton correlations, a novel and interesting aspect of the three dimensional structure of the nucleon.
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