FNUC / GEFN Seminars

Europe/Madrid
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FNUC

Red Temática de Física Nuclear
Luis M Fraile (Universidad Complutense (ES)), Alejandro ALGORA (IFIC (CSIC-Uni. Valencia)), Dolores Cortina (Universidad de Santiago de Compostela), Carlos Guerrero Sanchez (Universidad de Sevilla (ES)), Laura Tolos (ICE CSIC), Silvia Vinals Onses (Universidad Autonoma de Madrid (ES))
Description

Seminarios de física nuclear

Red Temática de Física Nuclear - FNUC

Grupo Especializado de Física Nuclear de la RSEF - GEFN

 

Videoconference
FNUC / GEFN Seminars
Zoom Meeting ID
61870885467
Host
Luis M Fraile
Passcode
fnuc
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    • 10:00 AM 10:45 AM
      Seminar series
      Convener: Luis M Fraile (Universidad Complutense (ES))
      • 10:00 AM
        Search for dark decay in the halo of the Be-11 nucleus 25m

        There is a long-standing discrepancy in the neutron lifetime, yielding a 4 sigma difference when measuring the rate of disappearing neutrons and appearing protons. To explain this puzzle, it was suggested that neutrons could decay into dark sector particles with a branching ratio of ~1% (the so-called called dark decay). This decay mode would not produce a proton, explaining the discrepancy between the two methods. It was also theorized that weakly-bound neutrons in halo nuclei could undergo this dark decay, with Be-11 being the best candidate. Be-11 is also one of the few neutron-rich nuclei for which the beta-delayed proton emission (βp) window is open, an "a priori" contradictory decay mode on the east side of the nuclear chart.

        To shed light on these exotic decay modes, we performed an experiment at TRIUMF using the prototype Active Target Time Projection Chamber (pATTPC) and the high purity of the ISAC Be beams to directly observe the βp decay channel for the first time. In this talk, I will discuss the implications of this observation in the search of the dark decay, as well as some recent measurement that challenge our experiment and the future plans of the collaboration.

        Speaker: Dr Bruno Olaizola Mampaso (CERN)
    • 10:00 AM 10:45 AM
      Seminar series
      Convener: Alejandro ALGORA (IFIC (CSIC-Uni. Valencia))
      • 10:00 AM
        Beta decay of fission fragments with isomeric states 45m

        Many nuclei with beta decaying isomeric states are produced by means of fission. Some of them play a crucial role in nuclear reactors, as it is the case of the neutron rich niobium and yttrium isotopes around A=100 that will be discussed in this seminar. This region is particularly interesting from the nuclear structure point of view, since nuclear shape transitions are predicted and the possibility to observe signatures of collective modes inside the beta decay energy window has been suggested.

        The disentanglement of the beta decays of the isomers and the ground states requires a good separation technique and a well-controlled detection set-up. Challenging measurements of some of these decays have been performed at IGISOL (Jyväskylä, Finland) using the JYFLTRAP double Penning trap system for precision trap-assisted separation. The Total Absorption Gamma-ray Spectroscopy (TAGS) technique was employed to determine the beta intensity probabilities populating the states in the daughter nuclei. TAGS has been shown to be a powerful tool to obtain such probabilities free of the systematic Pandemonium effect.

        Speaker: Dr Víctor Guadilla (FUW, Warsaw, Poland)
    • 10:00 AM 10:45 AM
      Seminar series
      Convener: Laura Tolos
      • 10:00 AM
        Transport theory of D mesons in a thermal environment 45m

        We have studied the many-body physics of D mesons in a thermal medium by applying an effective field theory based on chiral and heavy-quark symmetries. Relying on exact unitarity constraints and self-consistency, we have analyzed the in-medium properties of charmed mesons and developed a kinetic theory approach. I will report our findings on in-medium modifications including off-shell effects, and the heavy-flavor transport coefficients below the chiral restoration temperature.

        Speaker: Juan Torres-Rincon (IEEC)
    • 10:00 AM 10:45 AM
      Seminar series
      Convener: Dolores Cortina (Universidad de Santiago de Compostela)
      • 10:00 AM
        Study of nuclear fission barriers and fIssion yields of exotic nuclei using the advanced R3B experimental apparatus at the GSI-FAIR facility 45m

        Although the importance of the fission fragment treatment in r-process calculations is well established, an aspect of the phenomenological descriptions of fission that has so far remained relatively unexplored in the r-process is the dependence of the fission yields on the excitation energy or temperature of the compound nuclei. Additionally, the fission yields and fission barrier heights of nuclei far from the stability line are also crucial to describe correctly the r-process cycle as well as the transitions from symmetric to asymmetric fission. Obviously, these observables have to be measured with high accuracy to constrain the astrophysical model calculations.
        Despite the recent experimental and theoretical progress in the investigation of the nuclear fission process, a complete description still represents a challenge in nuclear physics because it is a very complex dynamical process, whose description involves the coupling between intrinsic and collective degrees of freedom as well as different quantum-mechanical phenomena. Due to this complexity and the use of different reaction mechanisms to induce the fission process, as well as the definition of different fission observables which were often biased by the experimental conditions, many contradictory results and conclusions exist in literature. In the last decade, unprecedented fission experiments have been carried out at the GSI facility using the inverse kinematics technique in combination with state-of-the-art detectors especially designed to measure the fission products with high detection efficiency and acceptance. For the first time in the long-standing history of fission, it was possible to simultaneously measure and identify both fission fragments in mass and atomic numbers and obtain many correlations among them sensitive to the fission process dynamics and the nuclear structure at the scission point. Recently, these measurements have been improved combining the previous experimental setup with the calorimeter CALIFA (CALorimeter for In-Flight detection of gamma-rays and high energy charged pArticles) and the neutron detector NeuLAND (New LArge Neutron Detector) developed by the R3B collaboration at GSI, which allow us to measure the gamma rays and light particles in coincidence with the fission fragments.

        Speaker: Jose Luis Rodriguez Sanchez (University of Santiago de Compostela)
    • 10:00 AM 10:45 AM
      Seminar series
      Convener: Carlos Guerrero Sanchez (Universidad de Sevilla (ES))
      • 10:00 AM
        The relevance of neutrino-nucleus interaction models in neutrino oscillation experiments: T2K and SuperKamiokande 45m

        The discovery of neutrino oscillations (Professor T. Kajita from Kamiokande and A. McDonald from SNO, 2015 Physics Nobel Prize) has motivated several experiments, such as T2K and SuperKamiokande, aimed at determining neutrino oscillation parameters and CP violation as well as other open questions in physics such as matter-antimatter asymmetry, dark matter search, proton decay or supernovae analysis. However, the precise knowledge of these neutrino properties requires an accurate description of neutrino-nucleus interactions. Accordingly, the development and implementation of sophisticated neutrino interaction models in the Monte Carlo event generators employed in neutrino oscillation experiments plays an essential role. In this context, the so-called SuSAv2-MEC model, developed by the University of Seville group and collaborators and based on the Relativistic Mean Field theory, has recently proven its validity to analyze neutrino-nucleus scattering data in the kinematical region of interest for current and forthcoming neutrino oscillation experiments, being a promising candidate to be implemented in event generators for improving the oscillation analysis.

        Speaker: Guillermo D. Megias (CEA-Irfu (France) and University of Seville (Spain))
    • 10:00 AM 10:45 AM
      Seminar series
      Convener: Prof. Luis M Fraile (Universidad Complutense (ES))
      • 10:00 AM
        From COULomb EXcitation to the first Multi-Nucleon Transfer experiment in the new HIE-ISOLDE era 45m

        The ISOLDE facility finished in 2018 a major upgrade in terms of the energy of post-accelerated exotic beams bringing it up from 3 MeV/u to 10.0 MeV/u. The increased beam energy opens new opportunities for expanding the experimental techniques to address new physics cases. Here, I will present the preliminary results of two of the experiments carried out during the last 4 years employing two different techniques at HIE-ISOLDE in combination with the MINIBALL array.

        This first experiment corresponds with the first beam delivered in October 2015. The aim was to study the collectivity in the vicinity of 78Ni via COULomb Excitation (COULEX). In particular, the experiment was devoted to study the collectivity in the even-even Zn isotopes between N = 40 and N = 50 [1-4]. The new beam energies up to 5 MeV/u strongly enhances the probability of multi-step Coulomb excitation, giving experimental access to new excited states and bringing in-depth information on their structure.

        The second experiment was dedicated to produce nuclei in the south-east region around the doubly magic 208Pb via Multi-Nucleon Transfer (MNT). This region represents an ideal testing ground for the state-of-the-art realistic shell-model calculations in heavy nuclei [5]. With this aim, the first MNT experiment at the ISOLDE facility was carried out in September 2017 with the goal of populating medium- to high-spin states in the neutron-rich Pb and Hg region [6] and validating this technique with high intensity and high energy post-accelerated Radioactive Ion Beams (RIB).

        [1] J. Van de Walle et al., Phys. Rev. Lett. 99 14501 (2007).
        [2] J. Van de Walle et al., Phys. Rev. C, 79:014309 (2009).
        [3] M. Niikura et al., Phys. Rev. C 85 054321 (2012).
        [4] C. Louchart et al., Phys. Rev. C, 87:054302 (2013).
        [5] A. Gottardo et al., Phys. Rev. Lett. 109, 162502 (2012).
        [6] A. Gottardo et al., Phys. Lett. B 725, 292-296 (2013).

        Speaker: Andres Illana Sison (University of Jyvaskyla (FI))
    • 10:00 AM 10:45 AM
      Seminar series
      Convener: Alejandro ALGORA (IFIC (CSIC-Uni. Valencia))
      • 10:00 AM
        High precision neutron emission measurements of nuclei around 78Ni for nuclear astrophysics 45m

        Beta-delayed neutron emission is the principal decay mode of very neutron-rich nuclei produced during the rapid neutron capture process (r-process). This form of decay plays a key role determining the r-process path and affects the final abundance distribution in a complex way, shifting the distribution to lower masses, while it provides neutrons for late captures after the freeze-out with the opposite effect. Thus, a good knowledge of beta-delayed neutron emission probabilities and beta-decay half-lives is required for a meaningful comparison of r-process simulations with the observed elemental abundances. Furthermore, some of the nuclei involved in the r-process can emit more than one neutron in the decay. Our current understanding of the beta-delayed multiple neutron emission is incomplete because of the scarcity of experimental data. Additionally, neutron emission probabilities are sensitive to the nuclear wave function and can be used as a test of nuclear structure studies.

        With these ideas in mind the Beta-delayed neutrons at RIKEN (BRIKEN) Collaboration has set up a powerful detection system based on a state-on-the-art instrumentation, namely an implanted-ion and decay detector AIDA and a large neutron counter. The setup exploits the very intense secondary radioactive beams available at the end of the in-flight separator BigRIPS and ZeroDegree spectrometer, hosted in the RIKEN Nishina Center, to measure implant-beta and implant-beta-neutron decay curves, and extract from them new and precise beta-delayed neutron emission probabilities and half-lives.

        Speaker: Alvaro Tolosa Delgado (University of Jyvaskyla (FI))
    • 10:00 AM 11:00 AM
      Seminar series
      Convener: Carlos Guerrero Sanchez (Universidad de Sevilla (ES))
      • 10:00 AM
        Exploration of dineutron correlations in Borromean nuclei through (p, pN) reactions 45m

        Knockout reactions with proton targets provide an invaluable tool to access the properties of Borromean (core+N+N) nuclei, where the correlation between the two valence nucleons plays a fundamental role in binding the system. One of the questions of current interest is the importance of the dineutron (a pair of spatially correlated neutrons) in these correlations. Recently, experimental results for the average opening angle as a function of the intrinsic neutron momentum in the 11Li(p, pN) reaction have shown a localization of dineutron correlations on the nuclear surface. In this work we explore the dependence of this observable (the average opening angle) on the structure of the Borromean nucleus and the effects of distortion and absorption assuming a quasifree sudden model to describe the knockout process and a three-body model to describe the nucleus. We compare our results to the recent 11Li data and present predictions for the 19B and 17Ne nuclei, exploring the possibilities this observable presents to study the properties of Borromean nuclei.

        Speaker: Mario Gómez Ramos (Universidad de Sevilla)
    • 10:00 AM 11:00 AM
      Seminar series
      Convener: Prof. Luis M Fraile (Universidad Complutense (ES))
      • 10:00 AM
        Beam stripping interactions in compact cyclotrons 45m

        Beam stripping interactions with residual gas and electromagnetic fields represents a significant contribution to beam losses in particle accelerators. These processes play an important role in H- compact cyclotrons, usually operated with an internal injection system and high magnetic fields. Therefore, the analysis of the interactions within the beam dynamics study of the accelerator yields relevant information for the appropriate performance of the machine and the optimization of the operation. The stripping interactions have been implemented into the beam dynamics code OPAL, providing an adequate framework to estimate the stripping losses in cyclotrons or beamlines. The simulation model has been used in the analysis of the AMIT compact cyclotron, aimed at radioisotope production, as well as the IsoDAR cyclotron, an isochronous machine geared towards neutrino physics experiments.

        Speaker: Dr Pedro Calvo Portela (CIEMAT)
    • 10:00 AM 11:00 AM
      Seminar series
      Convener: Prof. Luis M Fraile (Universidad Complutense (ES))
      • 10:00 AM
        Determinación del límite superior experimental de la rara transición βp en el B8: cómo determinar lo que no se puede ver 45m

        En esta charla, se presentará el caso físico de la desintegración β+ del núcleo halo 8B, en concreto la
        población mediante captura electrónica del estado más energético del 8Be: el único estado 1+ a 17.640
        MeV, 385 keV por encima del umbral de emisión de protón. Esta transición es de gran interés, sobre
        todo, porque se vería favorecida por la estructura de núcleo halo de protón del 8B. En [1] se estima un
        valor para la razón de ramificación de esta transición de 2.3x10-8, basado en la vida media conocida
        del 7Li. El único trabajo experimental hasta la fecha para medir esta emisión de protones ha reportado
        un límite superior de 2.6x10-5.

        Nuestro experimento se realizó en la Isolde Decay Station en el CERN en 2016 y fue diseñado para
        maximizar la sensibilidad del montaje experimental para la detección del protón emitido del estado
        1+antes mencionado. Los datos y el análisis llevado a cabo han permitido determinar un límite superior
        experimental para la transición de interés más bajo que el reportado en [1]. Para poder determinar
        este límite, el trabajo se ha basado en simulaciones Monte Carlo muy precisas de las condiciones
        experimentales [2].

        [1] M. Borge, et al., Journal of physics G: nuclear and particle physics 40(035109) (2013)
        [2] S. Viñals, E. Nácher, O. Tengblad, et al., Eur. Phys. J. A (57), 49 (2021)

        Speaker: Silvia Vinals Onses (Universidad Autonoma de Madrid (ES))
    • 10:00 AM 11:00 AM
      Seminar series
      Convener: Tomás Rodríguez (Universidad Autónoma de Madrid)
      • 10:00 AM
        R-process sensitivity to properties of (super?) heavy nuclei 45m

        About half of the elements heavier than iron found in nature, including the heaviest uranium and thorium, are produced in a specific stellar nucleosynthesis process: the rapid neutron capture process (or r-process). During the r-process, several thousands of exotic neutron-rich nuclei are synthesized in few seconds, powering an electromagnetic transient known as kilonova. Since most of r-process nuclei have never been experimentally observed due to their exceedingly short half-lives, the estimation of abundances and kilonova light curves must rely upon the theoretical predictions of nuclear properties. During this talk, I will present some recent calculations of nuclear properties obtained within the Density Functional Theory (DFT) and their impact on the r-process. In particular, I will focus on the nucleosynthesis of translead elements in the merger of two neutron stars, and the role that nuclear masses, beta decays and fission play in shaping the r-process abundances and kilonova light curves.

        Speaker: Dr Samuel Giuliani (ECT*)
    • 4:00 PM 5:00 PM
      Seminar series
      Convener: Prof. Luis M Fraile (Universidad Complutense (ES))
      • 4:00 PM
        Structure and Decay of Beryllium Isotopes Beyond the Neutron Dripline 45m

        Near and beyond the neutron dripline, where the energy needed to remove one nucleon is low enough, the emission of neutron(s) becomes the dominant decay mechanism. The spontaneous emission of two neutrons should be favored in nuclei that are unbound with respect to two-neutron emission but bound with respect to single-neutron emission, such as 26O [1]. Another very interesting candidate can be found by adding two neutrons to the most neutron-rich Beryllium isotope, 14Be, a well-known 2n-halo nucleus. During this talk, results for the spectroscopy and neutron decay of the most neutron-rich isotopes of Beryllium, 14Be, 15Be and especially 16Be, investigated during different experimental campaigns at RIBF-RIKEN using the SAMURAI setup, will be presented. In particular, the three-body correlations from the two-neutron decay of 16Be have been thoroughly investigated and characterized from microscopic principles. A joint effort between experiment and theory [2] has allowed a direct comparison to connect the experimental nn signal we observe with the three-body wave-function.

        [1] Y. Kondo et al., Phys. Rev. Lett. 116, 102503
        [2] J. Casal and J. Gómez-Camacho, Phys. Rev. C 99, 014604

        Speaker: Dr Belén Monteagudo Godoy (NSCL - MSU)