118454757
Signatures of Dark Matter Scattering Inelastically Off Nuclei
Direct dark matter detection focuses on elastic scattering of dark matter particles off nuclei. In this study, we explore inelastic scattering where the nucleus is excited to a low-lying state of 10-100 keV, with subsequent prompt de-excitation. We calculate the inelastic structure factors for the odd-mass xenon isotopes based on state-of-the-art large-scale shell-model calculations with chiral effective field theory WIMP-nucleon currents. For these cases, we find that the inelastic channel is comparable to or can dominate the elastic channel for momentum transfers around 150 MeV. We calculate the inelastic recoil spectra in the standard halo model, compare these to the elastic case, and discuss the expected signatures in a xenon detector, along with implications for existing and future experiments. The combined information from elastic and inelastic scattering will allow to determine the dominant interaction channel within one experiment. In addition, the two channels probe different regions of the dark matter velocity distribution and can provide insight into the dark halo structure. The allowed recoil energy domain and the recoil energy at which the integrated inelastic rates start to dominate the elastic channel depend on the mass of the dark matter particle, thus providing a potential handle to constrain its mass.
118464776
Large-scale nuclear structure calculations for spin-dependent WIMP scattering with chiral effective field theory currents
We perform state-of-the-art large-scale shell-model calculations of the structure factors for elastic spin-dependent WIMP scattering off Xe, I, Ge, F, Na ,Al, and Si. This comprehensive survey covers the nonzero-spin nuclei relevant to direct dark matter detection. We include a pedagogical presentation of the formalism necessary to describe elastic and inelastic WIMP-nucleus scattering. The valence spaces and nuclear interactions employed have been previously used in nuclear structure calculations for these mass regions and yield a good spectroscopic description of these isotopes. We use spin-dependent WIMP-nucleus currents based on chiral effective field theory (EFT) at the one-body level and including the leading long-range two-body currents due to pion exchange, which are predicted in chiral EFT. Results for all structure factors are provided with theoretical error bands due to the nuclear uncertainties of WIMP currents in nuclei.
7592155
New precision mass measurements of neutron-rich calcium and potassium isotopes and three-nucleon forces.
We present precision Penning trap mass measurements of neutron-rich calcium and potassium isotopes in the vicinity of neutron number N=32. Using the TITAN system, the mass of 51K was measured for the first time, and the precision of the (51,52)Ca mass values were improved significantly. The new mass values show a dramatic increase of the binding energy compared to those reported in the atomic mass evaluation. In particular, 52Ca is more bound by 1.74 MeV, and the behavior with neutron number deviates substantially from the tabulated values. An increased binding was predicted recently based on calculations that include three-nucleon (3N) forces. We present a comparison to improved calculations, which agree remarkably with the evolution of masses with neutron number, making neutron-rich calcium isotopes an exciting region to probe 3N forces.
122908821
Theoretical uncertainties in the nuclear matrix elements of neutrinoless double beta decay: The transition operator
We explore the theoretical uncertainties related to the transition operator of neutrinoless double-beta (0νββ) decay. The transition operator used in standard calculations is a product of one-body currents, that can be obtained phenomenologically as in Tomoda [1] or Simkovic et al. [2]. However, corrections to the operator are hard to obtain in the phenomenological approach. Instead, we calculate the 0νββ decay operator in the framework of chiral effective theory (EFT), which gives a systematic order-by-order expansion of the transition currents. At leading orders in chiral EFT we reproduce the standard one-body currents of Refs. [1] and [2]. Corrections appear as two-body (2b) currents predicted by chiral EFT. We compute the effects of the leading 2b currents to the nuclear matrix elements of 0νββ decay for several transition candidates. The 2b current contributions are related to the quenching of Gamow-Teller transitions found in nuclear structure calculations.
40927956
Breakdown of the isobaric multiplet mass equation for the A = 20 and 21 multiplets.
Using the Penning trap mass spectrometer TITAN, we performed the first direct mass measurements of (20,21)Mg, isotopes that are the most proton-rich members of the A = 20 and A = 21 isospin multiplets. These measurements were possible through the use of a unique ion-guide laser ion source, a development that suppressed isobaric contamination by 6 orders of magnitude. Compared to the latest atomic mass evaluation, we find that the mass of (21)Mg is in good agreement but that the mass of (20)Mg deviates by 3 σ. These measurements reduce the uncertainties in the masses of (20,21)Mg by 15 and 22 times, respectively, resulting in a significant departure from the expected behavior of the isobaric multiplet mass equation in both the A = 20 and A = 21 multiplets. This presents a challenge to shell model calculations using either the isospin nonconserving universal sd USDA and USDB Hamiltonians or isospin nonconserving interactions based on chiral two- and three-nucleon forces.
118407578
Three-nucleon forces and spectroscopy of neutron-rich calcium isotopes
We study excited-state properties of neutron-rich calcium isotopes based on chiral two- and three-nucleon interactions. We first discuss the details of our many-body framework, investigate convergence properties, and for two-nucleon interactions benchmark against coupled-cluster calculations. We then focus on the spectroscopy of 47-56Ca, finding that with both 3N forces and an extended pfg9/2 valence space, we obtain a good level of agreement with experiment. We also study electromagnetic transitions and find that experimental data are well described by our calculations. In addition, we provide predictions for unexplored properties of neutron-rich calcium isotopes.
122786396
Busqueda de bosones de Higgs neutros supersimetricos en el experimento DELPHI de LEP hasta $\sqrt{s}$=209 GeV en sucesos a cuatro quarks b
Se ha participado en el analisis fisico de los datos recogidos por el experimento DELPHI en el acelerador LEP del Laboratorio Europeo de Fisica de Particulas (CERN) en Ginebra, responsabilizandose dentro de la colaboracion de la busqueda de bosones de Higgs neutros supersimetricos en el canal 4b. Se ha desarrollado un analisis inclusivo basado en una definicion del etiquetado de quarks b especifica para este canal logrando uan reduccion muy severa del fondo. La reconstruccion cinematica de los mismos y la definicion de una valor como candidatos en la hipotesis de produccion hA con una determinada masa. Se ha aplicado este analisis a los datos recogidos por el detector DELPHI en los anos 1999 y 2000 con un total de 452 pb-1 en un rango de energias entre vs=192 GeVy vs=208 GeV. Se han estudiado los candidatos mas relevantes, incluyendo su visualizacion, siendo compatible con el fondo esperado de los procesos fisicos del Modelo Estandar. Estos resultados, con su identificacion, masa y variable discriminante, han sido utilizados para obtener los niveles de confianza correspondientes a la hipotesis de existencia de bosones de Higgs en el MSSM en el rango de masas entre 12 GeVc2 y 130 GeV/c2. La combinacion con el resto de los canales en la busqueda del boson de Higgs en el Modelo Estandar y MSSM ha permitido obtener limites inferiores a la masa de los bosones en torno a valores proximos a la masa del Z asi como excluir regiones del plano del espacio de parametros.