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Pasqualato, G. et al, Domingo-Pardo, C., & Gadea, A. (2023). Shape evolution in even-mass 98-104Zr isotopes via lifetime measurements using the γ γ-coincidence technique. Eur. Phys. J. A, 59(11), 276–13pp.
Abstract: The Zirconium (Z = 40) isotopic chain has attracted interest for more than four decades. The abrupt lowering of the energy of the first 2(+) state and the increase in the transition strength B(E2; 2(1)(+) -> 0(1)(+) ) going from Zr-98 to Zr-100 has been the first example of “quantum phase transition” in nuclear shapes, which has few equivalents in the nuclear chart. Although a multitude of experiments have been performed to measure nuclear properties related to nuclear shapes and collectivity in the region, none of the measured lifetimes were obtained using the Recoil Distance Doppler Shift method in the gamma gamma-coincidence mode where a gate on the direct feeding transition of the state of interest allows a strict control of systematical errors. This work reports the results of lifetime measurements for the first yrast excited states in Zr98-104 carried out to extract reduced transition probabilities. The new lifetime values in gamma gamma-coincidence and gamma-single mode are compared with the results of former experiments. Recent predictions of the Interacting Boson Model with Configuration Mixing, the Symmetry Conserving Configuration Mixing model based on the Hartree-Fock- Bogoliubov approach and the Monte Carlo Shell Model are presented and compared with the experimental data.
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Tagliente, G. et al, Babiano-Suarez, V., Domingo-Pardo, C., Ladarescu, I., & Tain, J. L. (2024). High-resolution cross section measurements for neutron interactions on 89Y with incident neutron energies up to 95 keV. Eur. Phys. J. A, 60(1), 21–18pp.
Abstract: The cross section of the Y-89(n,gamma) reaction has important implications in nuclear astrophysics and for advanced nuclear technology. Given its neutron magic number N = 50 and a consequent small neutron capture crosssection,89Y represents one of the key nuclides for the stellars-process. It acts as a bottleneck in the neutron capture chain between the Fe seed and the heavier elements. Moreover, it is located at the overlapping region, where both the weak and mains-process components take place.Y-89, the only stable yttrium isotope, is also used in innovative nuclear reactors. Neutron capture and transmission measurements were per-formed at the time-of-flight facilities n_TOF at CERN and GELINA at JRC-Geel. Resonance parameters of individual resonances were extracted from a resonance analysis of the experimental transmission and capture yields, up to a neutron incident energy of 95 keV. Even though a comparison with results reported in the literature shows differences in resonance parameters, the present data are consistent with the Maxwellian averaged cross section suggested by the astro-physical database KADoNiS.
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n_TOF Collaboration(Wright, T. et al), Domingo-Pardo, C., & Tain, J. L. (2024). Measurement of the prompt fission γ-rays from slow neutron-induced fission of 235U with STEFF. Eur. Phys. J. A, 60(3), 70–11pp.
Abstract: The amount of energy carried by gamma-rays during the fission process is an important consideration when developing new reactor designs. Many studies of gamma-ray energy and multiplicity, from a multitude of fissioning systems, were measured during the 1970s. However the data from such experiments largely underestimates the heating effect caused by gamma-rays in the structure of a reactor. It is therefore essential to obtain more accurate measurements of the energy carried during gamma-ray emission. As such, the OECD Nuclear Energy Agency has put out a high priority request [1] for measurements of the mean gamma-ray energy and multiplicity to an accuracy better than 7.5 percent from several fissioning systems; including U-235(n(thermal)). Measurements of the rays from these fissioning nuclei were performed with the SpecTrometer for Exotic Fission Fagments (STEFF).
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Abreu, L. M., Song, J., Brandao, P. C. S., & Oset, E. (2024). A note on the tensor and vector exchange contributions to K (K)over-bar → K (K)over-bar, D(D)over-bar → D(D)over-bar and π+π- → π+π- reactions. Eur. Phys. J. A, 60(3), 76–10pp.
Abstract: In this note we study the tensor and vector exchange contributions to the elastic reactions involving the pseudoscalars mesons pi(+) pi(-), K+ K- and D+D-. In the case of the tensor-exchange contributions we assume that an intermediate tensor f(2)(1270) is dynamically generated from the interaction of two virtual rho mesons, with the use of a pole approximation. The calculation of the two-loop amplitude is facilitated since the triangle loops can be factorized and computed separately. The results show very small contributions coming from the tensor-exchange mechanisms when compared with those from the vector-exchange processes. We compare our results for pi pi and K (K) over bar scattering with those obtained in other works where the f2(1270) is considered as an ordinary q (q) over bar meson. Our picture provides a smaller contribution but of similar order of magnitude for pion scattering and stabilizes the results in the case of K (K) over bar, allowing us to make estimates for D (D) over bar scattering.
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ATLAS Collaboration(Aad, G. et al), Amoros, G., Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Escobar, C., et al. (2010). Readiness of the ATLAS Tile Calorimeter for LHC collisions. Eur. Phys. J. C, 70(4), 1193–1236.
Abstract: The Tile hadronic calorimeter of the ATLAS detector has undergone extensive testing in the experimental hall since its installation in late 2005. The readout, control and calibration systems have been fully operational since 2007 and the detector has successfully collected data from the LHC single beams in 2008 and first collisions in 2009. This paper gives an overview of the Tile Calorimeter performance as measured using random triggers, calibration data, data from cosmic ray muons and single beam data. The detector operation status, noise characteristics and performance of the calibration systems are presented, as well as the validation of the timing and energy calibration carried out with minimum ionising cosmic ray muons data. The calibration systems' precision is well below the design value of 1%. The determination of the global energy scale was performed with an uncertainty of 4%.
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ATLAS Collaboration(Aad, G. et al), Amoros, G., Bernabeu Verdu, J., Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., et al. (2010). The ATLAS Inner Detector commissioning and calibration. Eur. Phys. J. C, 70(3), 787–821.
Abstract: The ATLAS Inner Detector is a composite tracking system consisting of silicon pixels, silicon strips and straw tubes in a 2 T magnetic field. Its installation was completed in August 2008 and the detector took part in data-taking with single LHC beams and cosmic rays. The initial detector operation, hardware commissioning and in-situ calibrations are described. Tracking performance has been measured with 7.6 million cosmic-ray events, collected using a tracking trigger and reconstructed with modular pattern-recognition and fitting software. The intrinsic hit efficiency and tracking trigger efficiencies are close to 100%. Lorentz angle measurements for both electrons and holes, specific energy-loss calibration and transition radiation turn-on measurements have been performed. Different alignment techniques have been used to reconstruct the detector geometry. After the initial alignment, a transverse impact parameter resolution of 22.1 +/- 0.9 μm and a relative momentum resolution sigma (p) /p=(4.83 +/- 0.16)x10(-4) GeV(-1)xp (T) have been measured for high momentum tracks.
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Amelino-Camelia, G. et al, Bernabeu, J., & Passemar, E. (2010). Physics with the KLOE-2 experiment at the upgraded DA Phi NE. Eur. Phys. J. C, 68(3-4), 619–681.
Abstract: Investigation at a f-factory can shed light on several debated issues in particle physics. We discuss: (i) recent theoretical development and experimental progress in kaon physics relevant for the Standard Model tests in the flavor sector, (ii) the sensitivity we can reach in probing CPT and Quantum Mechanics from time evolution of entangled-kaon states, (iii) the interest for improving on the present measurements of non-leptonic and radiative decays of kaons and eta/eta' mesons, (iv) the contribution to understand the nature of light scalar mesons, and (v) the opportunity to search for narrow di-lepton resonances suggested by recent models proposing a hidden dark-matter sector. We also report on the e(+)e(-) physics in the continuum with the measurements of (multi) hadronic cross sections and the study of gamma gamma processes.
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Bordes, J., Chan, H. M., & Tsun, T. S. (2010). Possible anomalies in Higgs decay: charm-suppression and flavour-violation. Eur. Phys. J. C, 65(3-4), 537–542.
Abstract: It is suggested that the Higgs boson may have a branching ratio into the c (c) over bar c mode suppressed by several orders of magnitude compared with conventional predictions and in addition some small but detectable flavour-violating modes such as b (s) over bar and tau(mu) over bar. The suggestion is based on a scheme proposed and tested earlier for explaining the mixing pattern and mass hierarchy of fermions in terms of a rotating mass matrix. If confirmed, the effects would cast new light on the geometric origin of fermion generations and of the Higgs field itself.
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ATLAS Collaboration(Aad, G. et al), Amoros, G., Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Escobar, C., et al. (2011). Measurement of inclusive jet and dijet cross sections in proton-proton collisions at 7 TeV centre-of-mass energy with the ATLAS detector. Eur. Phys. J. C, 71(2), 1512–59pp.
Abstract: Jet cross sections have been measured for the first time in proton-proton collisions at a centre-of-mass energy of 7 TeV using the ATLAS detector. The measurement uses an integrated luminosity of 17 nb(-1) recorded at the Large Hadron Collider. The anti-k(t) algorithm is used to identify jets, with two jet resolution parameters, R = 0.4 and 0.6. The dominant uncertainty comes from the jet energy scale, which is determined to within 7% for central jets above 60 GeV transverse momentum. Inclusive single-jet differential cross sections are presented as functions of jet transverse momentum and rapidity. Dijet cross sections are presented as functions of dijet mass and the angular variable chi. The results are compared to expectations based on next-to-leading-order QCD, which agree with the data, providing a validation of the theory in a new kinematic regime.
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CDF Collaboration(Aaltonen, T. et al), Cabrera, S., & Cuenca Almenar, C. (2010). Study of multi-muon events produced in p (p)over-bar interactions at root s=1.96 TeV. Eur. Phys. J. C, 68(1-2), 109–118.
Abstract: We report the results of a study of multi-muon events produced at the Fermilab Tevatron collider and acquired with the CDF II detector using a dedicated dimuon trigger. The production cross section and kinematics of events in which both muon candidates are produced inside the beam pipe of radius 1.5 cm are successfully modeled by known processes which include heavy flavor production. In contrast, we are presently unable to fully account for the number and properties of the remaining events, in which at least one muon candidate is produced outside of the beam pipe, in terms of the same understanding of the CDF II detector, trigger, and event reconstruction.
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