ForewordThe Pierre Auger Observatory has begun a major Upgrade of its already impressive capabilities, with an emphasis on improved mass composition determination using the surface detectors of the Observatory. Known as AugerPrime, the upgrade will include new 4 m 2 plastic scintillator detectors on top of all 1660 water-Cherenkov detectors, updated and more flexible surface detector electronics, a large array of buried muon detectors, and an extended duty cycle for operations of the fluorescence detectors.This Preliminary Design Report was produced by the Collaboration in April 2015 as an internal document and information for funding agencies. It outlines the scientific and technical case for AugerPrime 1 . We now release it to the public via the arXiv server. We invite you to review the large number of fundamental results already achieved by the Observatory and our plans for the future.The Pierre Auger Collaboration 1 As a result of continuing R&D, slight changes have been implemented in the baseline design since this Report was written. These changes will be documented in a forthcoming Technical Design Report. ix x Executive Summary Present Results from the Pierre Auger ObservatoryMeasurements of the Auger Observatory have dramatically advanced our understanding of ultra-high energy cosmic rays. The suppression of the flux around 5×10 19 eV is now confirmed without any doubt. Strong limits have been placed on the photon and neutrino components of the flux indicating that "top-down" source processes, such as the decay of superheavy particles, cannot account for a significant part of the observed particle flux. A largescale dipole anisotropy of ∼7% amplitude has been found for energies above 8×10 18 eV. In addition there is also an indication of the presence of a large scale anisotropy below the ankle. Particularly exciting is the observed behavior of the depth of shower maximum with energy, which changes in an unexpected, non-trivial way. Around 3×10 18 eV it shows a distinct change of slope with energy, and the shower-to-shower variance decreases. Interpreted with the leading LHC-tuned shower models, this implies a gradual shift to a heavier composition. A number of fundamentally different astrophysical model scenarios have been developed to describe this evolution. The high degree of isotropy observed in numerous tests of the small-scale angular distribution of UHECR above 4×10 19 eV is remarkable, challenging original expectations that assumed only a few cosmic ray sources with a light composition at the highest energies. Interestingly, the largest departures from isotropy are observed for cosmic rays with E > 5.8×10 19 eV in ∼20 • sky-windows. Due to a duty cycle of ∼15% of the fluorescence telescopes, the data on the depth of shower maximum extend only up to the flux suppression region, i.e. 4×10 19 eV. Obtaining more information on the composition of cosmic rays at higher energies will provide crucial means to discriminate between the model classes and to understand the origin of the observed flux suppre...
A narrow pentaquark state, P c ð4312Þ þ , decaying to J=ψp, is discovered with a statistical significance of 7.3σ in a data sample of Λ 0 b → J=ψpK − decays, which is an order of magnitude larger than that previously analyzed by the LHCb Collaboration. The P c ð4450Þ þ pentaquark structure formerly reported by LHCb is confirmed and observed to consist of two narrow overlapping peaks, P c ð4440Þ þ and P c ð4457Þ þ , where the statistical significance of this two-peak interpretation is 5.4σ. The proximity of the Σ þ cD 0 and Σ þ cD Ã0 thresholds to the observed narrow peaks suggests that they play an important role in the dynamics of these states.
Observations of exotic structures in the J=ψp channel, which we refer to as charmonium-pentaquark states, in Λ 0 b → J=ψK − p decays are presented. The data sample corresponds to an integrated luminosity of 3 fb −1 acquired with the LHCb detector from 7 and 8 TeV pp collisions. An amplitude analysis of the three-body final state reproduces the two-body mass and angular distributions. To obtain a satisfactory fit of the structures seen in the J=ψp mass spectrum, it is necessary to include two Breit-Wigner amplitudes that each describe a resonant state. The significance of each of these resonances is more than 9 standard deviations. One has a mass of 4380 AE 8 AE 29 MeV and a width of 205 AE 18 AE 86 MeV, while the second is narrower, with a mass of 4449.8 AE 1.7 AE 2.5 MeV and a width of 39 AE 5 AE 19 MeV. The preferred J P assignments are of opposite parity, with one state having spin 3=2 and the other 5=2.
A test of lepton universality, performed by measuring the ratio of the branching fractions of the B 0 → K * 0 µ + µ − and B 0 → K * 0 e + e − decays, R K * 0 , is presented. The K * 0 meson is reconstructed in the final state K + π − , which is required to have an invariant mass within 100 MeV/c 2 of the known K * (892) 0 mass. The analysis is performed using proton-proton collision data, corresponding to an integrated luminosity of about 3 fb −1 , collected by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. The ratio is measured in two regions of the dilepton invariant mass squared, q 2 , to be− 0.07 (stat) ± 0.03 (syst) for 0.045 < q 2 < 1.1 GeV 2 /c 4 , 0.69 + 0.11 − 0.07 (stat) ± 0.05 (syst) for 1.1 < q 2 < 6.0 GeV 2 /c 4 .The corresponding 95.4% confidence level intervals are [0.52, 0.89] and [0.53, 0.94]. The results, which represent the most precise measurements of R K * 0 to date, are compatible with the Standard Model expectations at the level of 2.1-2.3 and 2.4-2.5 standard deviations in the two q 2 regions, respectively.
A measurement of the ratio of branching fractions of the decays B þ → K þ μ þ μ − and B þ → K þ e þ e − is presented. The proton-proton collision data used correspond to an integrated luminosity of 5.0 fb −1 recorded with the LHCb experiment at center-of-mass energies of 7, 8, and 13 TeV. For the dilepton mass-squared range 1.1 < q 2 < 6.0 GeV 2 =c 4 the ratio of branching fractions is measured to be R K ¼ 0.846 þ0.060 −0.054 þ0.016 −0.014 , where the first uncertainty is statistical and the second systematic. This is the most precise measurement of R K to date and is compatible with the standard model at the level of 2.5 standard deviations.
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