NEXT Collaboration(Cebrian, S. et al), Alvarez, V., Carcel, S., Cervera-Villanueva, A., Diaz, J., Ferrario, P., et al. (2015). Accurate gamma and MeV-electron track reconstruction with an ultra-low diffusion Xenon/TMA TPC at 10 atm. Nucl. Instrum. Methods Phys. Res. A, 804, 8–24.
Abstract: We report the performance of a 10 atm Xenon/trimethylamine time projection chamber (TPC) for the detection of X-rays (30 keV) and gamma-rays (0.511-1.275 MeV) in conjunction with the accurate tracking of the associated electrons. When operated at such a high pressure and in similar to 1%-admixtures, trimethylamine (TMA) endows Xenon with an extremely low electron diffusion (1.3 +/- 0.13 mm-sigma (longitudinal), 0.95 +/- 0.20 mm-sigma (transverse) along 1 m drift) besides forming a convenient Penning-Fluorescent' mixture. The TPC, that houses 1.1 kg of gas in its fiducial volume, operated continuously for 100 live-days in charge amplification mode. The readout was performed through the recently introduced microbulk Micromegas technology and the AFTER chip, providing a 3D voxelization of 8 mm x 8 mm x 1.2 mm for approximately 10 cm/MeV-long electron tracks. Resolution in energy (epsilon) at full width half maximum (R) inside the fiducial volume ranged from R = 14.6% (30 keV) to R = 4.6% (1.275 MeV). This work was developed as part of the R&D program of the NEXT collaboration for future detector upgrades in the search of the neutrino-less double beta decay (beta beta 0 nu) in Xe-136, specifically those based on novel gas mixtures. Therefore we ultimately focus on the calorimetric and topological properties of the reconstructed MeV-electron tracks. In particular, the obtained energy resolution has been decomposed in its various contributions and improvements towards achieving the R =1.4%root MeV/epsilon levels obtained in small sensors are discussed.
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NEXT Collaboration(Cebrian, S. et al), Alvarez, V., Carcel, S., Cervera-Villanueva, A., Diaz, J., Ferrario, P., et al. (2015). Radiopurity assessment of the tracking readout for the NEXT double beta decay experiment. J. Instrum., 10, P05006–16pp.
Abstract: The “Neutrino Experiment with a Xenon Time-Projection Chamber” (NEXT) is intended to investigate the neutrinoless double beta decay of Xe-136, which requires a severe suppression of potential backgrounds; therefore, an extensive screening and selection process is underway to control the radiopurity levels of the materials to be used in the experimental set-up of NEXT. The detector design combines the measurement of the topological signature of the event for background discrimination with the energy resolution optimization. Separate energy and tracking readout planes are based on different sensors: photomultiplier tubes for calorimetry and silicon multi-pixel photon counters for tracking. The design of a radiopure tracking plane, in direct contact with the gas detector medium, was specially challenging since the needed components like printed circuit boards, connectors, sensors or capacitors have typically, according to available information in databases and in the literature, activities too large for experiments requiring ultra-low background conditions. Here, the radiopurity assessment of tracking readout components based on gamma-ray spectroscopy using ultra-low background germanium detectors at the Laboratorio Subterraneo de Canfranc (Spain) is described. According to the obtained results, radiopure enough printed circuit boards made of kapton and copper, silicon photomultipliers and other required components, fulfilling the requirement of an overall background level in the region of interest of at most 8 x 10(-4) counts keV(-1) kg(-1) y(-1), have been identified.
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Navarra, F. S., Nielsen, M., Oset, E., & Sekihara, T. (2015). Testing the molecular nature of D-s0*(2317) and D-0*(2400) in semileptonic B-s and B decays. Phys. Rev. D, 92(1), 014031–14pp.
Abstract: We study the semileptonic B-s and B decays into the D-s0*(2317) and D-0*(2400) resonances, respectively. With the help of a chiral unitarity model in coupled channels we compute the ratio of the decay widths of both processes. Using current values of the width for the (B) over bar (0) -> D-0*(2400)(+)(v) over bar (l)l(-) we make predictions for the rate of the (B) over bar (0)(s) -> D-s0*(2317)(+)(v) over bar (l)l(-) decay and for the DK invariant mass distribution in the (B) over bar (0)(s) -> DK (v) over bar (l)l(-) decay.
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NA48/2 Collaboration(Batley, J. R. et al), & Fiorini, L. (2015). Search for the dark photon in pi(0) decays. Phys. Lett. B, 746, 178–185.
Abstract: A sample of 1.69 x 10(7) fully reconstructed pi(0) -> gamma e(+)e(-) decay candidates collected by the NA48/2 experiment at CERN in 2003-2004 is analyzed to search for the dark photon (A') production in the pi(0) -> gamma A' decay followed by the prompt A' -> e(+)e(-) decay. No signal is observed, and an exclusion region in the plane of the dark photon mass m(A') and mixing parameter epsilon(2) is established. The obtained upper limits on epsilon(2) are more stringent than the previous limits in the mass range 9 MeV/c(2) < m(A') < 70 MeV/c(2). The NA48/2 sensitivity to the dark photon production in the K-+/- -> pi(+/-)A' decay is also evaluated.
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Moline, A., Ibarra, A., & Palomares-Ruiz, S. (2015). Future sensitivity of neutrino telescopes to dark matter annihilations from the cosmic diffuse neutrino signal. J. Cosmol. Astropart. Phys., 06(6), 005–34pp.
Abstract: Cosmological observations and cold dark matter N-body simulations indicate that our Universe is populated by numerous halos, where dark matter particles annihilate, potentially producing Standard Model particles. In this paper we calculate the contribution to the diffuse neutrino background from dark matter annihilations in halos at all redshifts and we estimate the future sensitivity to the annihilation cross section of neutrino telescopes such as IceCube or ANTARES. We consider various parametrizations to describe the internal halo properties and for the halo mass function in order to bracket the theoretical uncertainty in the limits from the modeling of the cosmological annihilation flux. We find that observations of the cosmic diffuse neutrino flux at large angular distances from the galactic center lead to constraints on the dark matter annihilation cross section which are complementary to ( and for some extrapolations of the astrophysical parameters, better than) those stemming from observations of the Milky Way halo, especially for neutrino telescopes not pointing directly to the Milky Way center, as is the case of IceCube.
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Molina, F. et al, Rubio, B., Agramunt, J., Algora, A., Domingo-Pardo, C., Gadea, A., et al. (2015). T-z =-1 -> 0 beta decays of Ni-54, Fe-50, Cr-46, and Ti-42 and comparison with mirror (He-3,t) measurements. Phys. Rev. C, 91(1), 014301–19pp.
Abstract: We have studied the beta decay of the T-z = -1, f(7/2) shell nuclei Ni-54, Fe-50, Cr-46, and Ti-42 produced in fragmentation reactions. The proton separation energies in the daughter T-z = 0 nuclei are relatively large (approximate to 4-5 MeV) so studies of the. rays are essential. The experiments were performed at GSI as part of the Stopped-beam campaign with the RISING setup consisting of 15 Euroball Cluster Ge detectors. From the newly obtained high precision beta-decay half-lives, excitation energies, and beta branching ratios, we were able to extract Fermi and Gamow-Teller transition strengths in these beta decays. With these improved results it was possible to compare in detail the Gamow-Teller (GT) transition strengths observed in beta decay including a sensitivity limit with the strengths of the T-z = +1 to T-z = 0 transitions derived from high resolution (He-3,t) reactions on the mirror target nuclei at RCNP, Osaka. The accumulated B(GT) strength obtained from both experiments looks very similar although the charge exchange reaction provides information on a broader energy range. Using the “merged analysis” one can obtain a full picture of the B(GT) over the full Q(beta) range. Looking at the individual transitions some differences are observed, especially for the weak transitions. Their possible origins are discussed.
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Modamio, V., Valiente-Dobon, J. J., Jaworski, G., Huyuk, T., Triossi, A., Egea, J., et al. (2015). Digital pulse-timing technique for the neutron detector array NEDA. Nucl. Instrum. Methods Phys. Res. A, 775, 71–76.
Abstract: A new digital pulse-timing algorithm, to be used with the future neutron detector array NEDA, has been developed and tested. The time resolution of four 5 in diameter photomultiplier tubes (XP4512, R4144, R11833-100, and ET9390-kb), coupled to a cylindrical 5 in by 5 in BC501A liquict scintillator detector was measured by employing digital sampling electronics and a constant fraction discriminator (CFD) algorithm. The zero crossing of the CM algorithm was obtained with a cubic spline interpolation, which was continuous up to the second derivative. The performance of the algorithm was studied at sampling rates of 500 MS/s and 200 MS/s. The time resolution obtained with the digital electronics was compared to the values acquired with a standard analog CFD. The result of this comparison shows that the time resolution from the analog and the digital measurements at 500 MS/s and at 200 MS/s are within 15% for all the tested photomultiplier tubes.
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Miyahara, K., Hyodo, T., & Oset, E. (2015). Weak decay of Lambda(+)(c) for the study of Lambda(1405) and Lambda(1670). Phys. Rev. C, 92(5), 055204–8pp.
Abstract: We study the Lambda(c) decay process to pi(+) and the meson-baryon final state for the analysis of Lambda resonances. Considering the Cabibbo-Kobayashi-Maskawamatrix, color suppression, diquark correlation, and the kinematical condition, we show that the final meson-baryon state should be in a pure I = 0 combination, when the meson-baryon invariantmass is small. Because the I = 1 contamination usually makes it difficult to analyze Lambda resonances directly from experiments, the Lambda(c) decay is an ideal process to study Lambda resonances. Calculating the final-state interaction by chiral unitary approaches, we find that the pi Sigma invariant mass distributions have the same peak structure in the all charge combination of the pi Sigma states related to the higher pole of the two poles of the Lambda(1405). Furthermore, we obtain a clear Lambda(1670) peak structure in the (K) over bar N and eta Lambda spectra.
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Mijatovic, T., Szilner, S., Corradi, L., Montanari, D., Courtin, S., Fioretto, E., et al. (2015). Pairing Correlation Study in the 40Ar + 208Pb Multinucleon Transfer Reaction. Acta Phys. Pol. B, 46(3), 439–442.
Abstract: The Ar-40 + Pb-208 multinucleon transfer reaction has been studied at E-lab = 255 MeV with the large solid angle magnetic spectrometer PRISMA. Mass and charge yields, differential and total cross sections, total kinetic energy loss distributions of different channels were simultaneously measured. Angular distributions were measured in a wide angular range by matching different spectrometer angular settings. Absolute cross sections were obtained by careful evaluation of the spectrometer response function. These cross sections for different transfer channels allow the discussion of the role played by nucleon-nucleon correlations.
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Mendoza, S., & Olmo, G. J. (2015). Astrophysical constraints and insights on extended relativistic gravity. Astrophys. Space Sci., 357(2), 133–6pp.
Abstract: We give precise details to support that observations of gravitational lensing at scales of individual, groups and clusters of galaxies can be understood in terms of nonNewtonian gravitational interactions with a relativistic structure compatible with the Einstein Equivalence Principle. This result is derived on very general grounds without knowing the underlying structure of the gravitational field equations. As such, any developed gravitational theory built to deal with these astrophysical scales needs to reproduce the obtained results of this article.
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