|
|
NEXT Collaboration(Cebrian, S. et al), Perez, J., Alvarez, V., Benlloch-Rodriguez, J., Botas, A., Carcel, S., et al. (2017). Radiopurity assessment of the energy readout for the NEXT double beta decay experiment. J. Instrum., 12, T08003–20pp.
Abstract: The “Neutrino Experiment with a Xenon Time-Projection Chamber” (NEXT) experiment intends to investigate the neutrinoless double beta decay of Xe-136, and therefore requires a severe suppression of potential backgrounds. An extensive material screening and selection process was undertaken to quantify the radioactivity of the materials used in the experiment. Separate energy and tracking readout planes using different sensors allow us to combine the measurement of the topological signature of the event for background discrimination with the energy resolution optimization. The design of radiopure readout planes, in direct contact with the gas detector medium, was especially challenging since the required components typically have activities too large for experiments demanding ultra-low background conditions. After studying the tracking plane, here the radiopurity control of the energy plane is presented, mainly based on gamma-ray spectroscopy using ultra-low background germanium detectors at the Laboratorio Subterraneo de Canfranc (Spain). All the available units of the selected model of photomultiplier have been screened together with most of the components for the bases, enclosures and windows. According to these results for the activity of the relevant radioisotopes, the selected components of the energy plane would give a contribution to the overall background level in the region of interest of at most 2.4 x 10(-4) counts keV(-1) kg(-1) y(-1), satisfying the sensitivity requirements of the NEXT experiment.
|
|
|
|
NEXT Collaboration(Azevedo, C. D. R. et al), Gomez-Cadenas, J. J., Alvarez, V., Benlloch-Rodriguez, J. M., Botas, A., Carcel, S., et al. (2018). Microscopic simulation of xenon-based optical TPCs in the presence of molecular additives. Nucl. Instrum. Methods Phys. Res. A, 877, 157–172.
Abstract: We introduce a simulation framework for the transport of high and low energy electrons in xenon-based optical time projection chambers (OTPCs). The simulation relies on elementary cross sections (electron-atom and electron-molecule) and incorporates, in order to compute the gas scintillation, the reaction/quenching rates (atom-atom and atom-molecule) of the first 41 excited states of xenon and the relevant associated excimers, together with their radiative cascade. The results compare positively with observations made in pure xenon and its mixtures with CO2 and CF4 in a range of pressures from 0.1 to 10 bar. This work sheds some light on the elementary processes responsible for the primary and secondary xenon-scintillation mechanisms in the presence of additives, that are of interest to the OTPC technology.
|
|
|
|
Lopez-Ibañez, M. L., Melis, A., Jay Perez, M., & Vives, O. (2017). Slepton non-universality in the flavor-effective MSSM. J. High Energy Phys., 11(11), 162–27pp.
Abstract: Supersymmetric theories supplemented by an underlying flavor-symmetry G(f) provide a rich playground for model building aimed at explaining the flavor structure of the Standard Model. In the case where supersymmetry breaking is mediated by gravity, the soft-breaking Lagrangian typically exhibits large tree-level flavor violating e ff ects, even if it stems from an ultraviolet flavor-conserving origin. Building on previous work, we continue our phenomenological analysis of these models with a particular emphasis on leptonicflavor observables. We consider three representative models which aim to explain the flavor structure of the lepton sector, with symmetry groups G(f) = Delta (27), A(4); and S-3.
|
|
|
|
n_TOF Collaboration(Wright, T. et al), Domingo-Pardo, C., Giubrone, G., Tain, J. L., & Tarifeño-Saldivia, A. (2017). Measurement of the U-238(n,gamma) cross section up to 80 keV with the Total Absorption Calorimeter at the CERN n_TOF facility. Phys. Rev. C, 96(6), 064601–11pp.
Abstract: The radiative capture cross section of a highly pure (99.999%), 6.125(2) grams and 9.56(5) x 10(-4) atoms/barn areal density U-238 sample has been measured with the Total Absorption Calorimeter (TAC) in the 185 m flight path at the CERN neutron time-of-flight facility n_TOF. This measurement is in response to the NEA High Priority Request list, which demands an accuracy in this cross section of less than 3% below 25 keV. These data have undergone careful background subtraction, with special care being given to the background originating from neutrons scattered by the 238U sample. Pileup and dead-time effects have been corrected for. The measured cross section covers an energy range between 0.2 eV and 80 keV, with an accuracy that varies with neutron energy, being better than 4% below 25 keV and reaching at most 6% at higher energies.
|
|
|
|
ANTARES, I. C., Pierre Auger, LIGO Sci and VIRGO Collaborations(Albert, A. et al), Barrios-Marti, J., Coleiro, A., Hernandez-Rey, J. J., Illuminati, G., Lotze, M., et al. (2017). Search for High-energy Neutrinos from Binary Neutron Star Merger GW170817 with ANTARES, IceCube, and the Pierre Auger Observatory. Astrophys. J. Lett., 850(2), L35–18pp.
Abstract: The Advanced LIGO and Advanced Virgo observatories recently discovered gravitational waves from a binary neutron star inspiral. A short gamma-ray burst (GRB) that followed the merger of this binary was also recorded by the Fermi Gamma-ray Burst Monitor (Fermi-GBM), and the Anti-Coincidence Shield for the Spectrometer for the International Gamma-Ray Astrophysics Laboratory (INTEGRAL), indicating particle acceleration by the source. The precise location of the event was determined by optical detections of emission following the merger. We searched for high-energy neutrinos from the merger in the GeV-EeV energy range using the ANTARES, IceCube, and Pierre Auger Observatories. No neutrinos directionally coincident with the source were detected within +/- 500 s around the merger time. Additionally, no MeV neutrino burst signal was detected coincident with the merger. We further carried out an extended search in the direction of the source for high-energy neutrinos within the 14 day period following the merger, but found no evidence of emission. We used these results to probe dissipation mechanisms in relativistic outflows driven by the binary neutron star merger. The non-detection is consistent with model predictions of short GRBs observed at a large off-axis angle.
|
|
|
|
Gomez Dumm, D., Izzo Villafañe, M. F., Noguera, S., Pagura, V. P., & Scoccola, N. N. (2017). Strong magnetic fields in nonlocal chiral quark models. Phys. Rev. D, 96(11), 114012–19pp.
Abstract: We study the behavior of strongly interacting matter under a uniform intense external magnetic field in the context of nonlocal extensions of the Polyakov-Nambu-Jona-Lasinio model. A detailed description of the formalism is presented, considering the cases of zero and finite temperature. In particular, we analyze the effect of the magnetic field on the chiral restoration and deconfinement transitions, which are found to occur at approximately the same critical temperatures. Our results show that these models offer a natural framework to account for the phenomenon of inverse magnetic catalysis found in lattice QCD calculations.
|
|
|
|
Peñuelas, A., & Pich, A. (2017). Flavour alignment in multi-Higgs-doublet models. J. High Energy Phys., 12(12), 084–34pp.
Abstract: Extended electroweak scalar sectors containing several doublet multiplets require flavour-aligned Yukawa matrices to prevent the appearance at tree level of unwanted flavour-changing neutral-current transitions. We analyse the misalignment induced by one-loop quantum corrections and explore possible generalizations of the alignment condition and their compatibility with current experimental constraints. The hypothesis of flavour alignment at a high scale turns out to be consistent with all known phenomenological tests.
|
|
|
|
Yao, D. L., Alvarez-Ruso, L., & Vicente Vacas, M. J. (2017). Extraction of nucleon axial charge and radius from lattice QCD results using baryon chiral perturbation theory. Phys. Rev. D, 96(11), 116022–11pp.
Abstract: We calculate the nucleon axial form factor up to the leading one-loop order in a covariant chiral effective field theory with the Delta(1232) resonance as an explicit degree of freedom. We fit the axial form factor to the latest lattice QCD data and pin down the relevant low-energy constants. The lattice QCD data, for various pion masses below 400 MeV, can be well described up to a momentum transfer of similar to 0.6 GeV. The Delta(1232) loops contribute significantly to this agreement. Furthermore, we extract the axial charge and radius based on the fitted values of the low-energy constants. The results are g(A) = 1.237(74) and < r(A)(2)> = 0.263(38) fm(2). The obtained coupling g(A) is consistent with the experimental value if the uncertainty is taken into account. The axial radius is below but in agreement with the recent extraction from neutrino quasielastic scattering data on deuterium, which has large error bars. Up to our current working accuracy, r(A) is predicted only at leading order, i.e., the one-loop level. A more precise determination might need terms of O(p(5)).
|
|
|
|
ANTARES Collaboration(Albert, A. et al), Barrios-Marti, J., Coleiro, A., Hernandez-Rey, J. J., Illuminati, G., Lotze, M., et al. (2017). All-sky search for high-energy neutrinos from gravitational wave event GW170104 with the ANTARES neutrino telescope. Eur. Phys. J. C, 77(12), 911–7pp.
Abstract: Advanced LIGO detected a significant gravitational wave signal (GW170104) originating from the coalescence of two black holes during the second observation run on January 4th, 2017. Anall-sky high-energy neutrino follow-up search has been made using data from the Antares neutrino telescope, including both upgoing and downgoing events in two separate analyses. No neutrino candidates were found within +/- 500 s around the GW event time nor any time clustering of events over an extended time window of +/- 3 months. The non-detection is used to constrain isotropic-equivalent high-energy neutrino emission from GW170104 to less than similar to 1.2 x 10(55) erg for a E-2 spectrum. This constraint is valid in the energy range corresponding to the 5-95% quantiles of the neutrino flux [3.2 TeV; 3.6 PeV], if the GW emitter was below the Antares horizon at the alert time.
|
|
|
|
ANTARES Collaboration(Albert, A. et al), Barrios-Marti, J., Coleiro, A., Hernandez-Rey, J. J., Illuminati, G., Lotze, M., et al. (2018). All-flavor Search for a Diffuse Flux of Cosmic Neutrinos with Nine Years of ANTARES Data. Astrophys. J. Lett., 853(1), L7–5pp.
Abstract: The ANTARES detector is at present the most sensitive neutrino telescope in the northern hemisphere. The highly significant cosmic neutrino excess observed by the Antarctic IceCube detector can be studied with ANTARES, exploiting its complementing field of view, exposure, and lower energy threshold. Searches for an all-flavor diffuse neutrino signal, covering nine years of ANTARES data taking, are presented in this Letter. Upward-going events are used to reduce the atmospheric muon background. This work includes for the first time in ANTARES both track-like (mainly nu mu) and shower-like (mainly nu(e)) events in this kind of analysis. Track-like events allow for an increase of the effective volume of the detector thanks to the long path traveled by muons in rock and/ or sea water. Shower-like events are well reconstructed only when the neutrino interaction vertex is close to, or inside, the instrumented volume. A mild excess of high-energy events over the expected background is observed in nine years of ANTARES data in both samples. The best fit for a single power-law cosmic neutrino spectrum, in terms of perflavor flux at 100 TeV, is Phi(1f)(0) (100 TeV) = (1.7 +/- 1.0) x 10(-18) GeV-1 cm(-2) s(-1) sr(-1) with spectral index Gamma = 2.4(-0.4)(+0.5) .The null cosmic flux assumption is rejected with a significance of 1.6 sigma .
|
|
