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ATLAS Collaboration(Aad, G. et al), Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Fernandez Martinez, P., Ferrer, A., et al. (2015). Measurement of charged-particle spectra in Pb plus Pb collisions at root s(NN)=2.76 TeV with the ATLAS detector at the LHC. J. High Energy Phys., 09(9), 050–51pp.
Abstract: Charged-particle spectra obtained in Pb+Pb interactions at root s(NN) = 2.76TeV and pp interactions at root s(NN) = 2.76TeV with the ATLAS detector at the LHC are presented, using data with integrated luminosities of 0.15 nb(-1) and 4.2 pb(-1), respectively, in a wide transverse momentum (0.5 < p(T) < 150 GeV) and pseudorapidity (vertical bar eta vertical bar < 2) range. For Pb+Pb collisions, the spectra are presented as a function of collision centrality, which is determined by the response of the forward calorimeters located on both sides of the interaction point. The nuclear modification factors R-AA and R-CP are presented in detail as a function of centrality, p(T) and eta. They show a distinct p(T)-dependence with a pronounced minimum at about 7 GeV. Above 60 GeV, R-AA is consistent with a plateau at a centrality-dependent value, within the uncertainties. The value is 0.55 +/- 0.01(stat.) +/- 0.04(syst.) in the most central collisions. The R-AA distribution is consistent with flat vertical bar eta vertical bar dependence over the whole transverse momentum range in all centrality classes.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). Measurement of the forward Z boson production cross-section in pp collisions at root s=7 TeV. J. High Energy Phys., 08(8), 039–37pp.
Abstract: A measurement of the production cross-section for Z bosons that decay to muons is presented. The data were recorded by the LHCb detector during pp collisions at a centre-of-mass energy of 7 TeV, and correspond to an integrated luminosity of 1.0 fb(-1). The cross-section is measured for muons in the pseudorapidity range 2.0 < eta < 4.5 with transverse momenta p(T) >20 GeV/e. The dimuon mass is restricted to 60 < M mu+mu- < 120 GeV/c(2). The measured cross-section is sigma(Z ->mu+mu-) = (76.0 +/- 0.3 +/- 0.5 +/- 1.0 +/- 1.3) pb where the uncertainties are due to the sample size, systematic effects, the beam energy and the luminosity. This result is in good agreement with theoretical predictions at next-to-next-to-leading order in perturbative quantum chromodynamics. The cross-section is also measured differentially as a function of kinematic variables of the Z boson. Ratios of the production cross-sections of electroweak bosons are presented using updated LHCb measurements of W boson production. A precise test of the Standard Model is provided by the measurement of the ratio sigma(W+) -> mu(+) nu(mu) + sigma(W) -> mu(+) (nu) over bar (mu)/sigma(Z ->mu+mu-) = 0.09 +/- 0.12 +/- 0.05, where the uncertainty due to luminosity cancels.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). Forward production of Upsilon mesons in pp collisions at root s=7 and 8 TeV. J. High Energy Phys., 11(11), 103–34pp.
Abstract: The production of Upsilon mesons in pp collisions at root s = 7 and 8 TeV is studied with the LHCb detector using data samples corresponding to an integrated luminosity of 1 fb(-1) and 2 fb(-1) respectively. The production cross-sections and ratios of cross-sections are measured as functions of the meson transverse momentum p and rapidity y, for p < 30 GeV/c and 2.0 < y < 4.5.
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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 four-jet differential cross sections in root s=8 TeV proton-proton collisions using the ATLAS detector. J. High Energy Phys., 12(12), 105–76pp.
Abstract: Differential cross sections for the production of at least four jets have been measured in proton-proton collisions at root s = 8 TeV at the Large Hadron Collider using the ATLAS detector. Events are selected if the four anti-k(t) R = 0.4 jets with the largest transverse momentum (p(T)) within the rapidity range vertical bar y vertical bar < 2 : 8 are well separated (Delta R-4j(min) > 0.65), all have p(T) > 64 GeV, and include at least one jet with p(T) > 100 GeV. The dataset corresponds to an integrated luminosity of 20.3 fb(-1). The cross sections, corrected for detector effects, are compared to leading-order and next-to-leading-order calculations as a function of the jet momenta, invariant masses, minimum and maximum opening angles and other kinematic variables.
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Chachamis, G., Deak, M., Hentschinski, M., Rodrigo, G., & Sabio Vera, A. (2015). Single bottom quark production in kT-factorisation. J. High Energy Phys., 09(9), 123–17pp.
Abstract: We present a study within the k(T)-factorisation scheme on single bottom quark production at the LHC. In particular, we calculate the rapidity and transverse momentum differential distributions for single bottom quark/anti-quark production. In our setup, the unintegrated gluon density is obtained from the NLx BFKL Green function whereas we included mass effects to the Lx heavy quark jet vertex. We compare our results to the corresponding distributions predicted by the usual collinear factorisation scheme. The latter were produced with Pythia 8.1.
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