Neutrinonucleus cross sections Karlheinz Langanke GSI Helmholtzzentrum Darmstadt

Neutrino-nucleus cross sections Karlheinz Langanke GSI Helmholtzzentrum Darmstadt Technische Universität Darmstadt Facility for Antiproton and Ion Research Trento, May 2019

Google Earth: FAIR in 2025 Facility for Antiproton and Ion Research in Europe

The Universe in the Laboratory: Experimental collaborations APPA atom-, bio- und plasma physics, material research nuclear- and quark-matter exotic nuclei and nuclear astrophysics hadron structure and dynamics CBM Nu. STAR PANDA

FAIR: construction site

First SIS 100 accelerator doubletube segment

Core-collapse supernovae Roland Diehl

Neutrino spectra collapse phase: after bounce cooling of neutron star by nu pairs energy hierarchy due to opacity electron captures on nuclei (Juodagalvis, Martinez-Pinedo. . ) (Raffelt, Janka, Fischer, . . . ) recent work: spectra even lower

Electron capture: Lab vs Stars Capture is dominated by Gamow-Teller transitions During collapse, electrons are described by Fermi-Dirac distribution with chemical potentials of order a few Me. V Parent nuclei are described by thermal ensemble

Calculating stellar capture rates data KVI Groningen Capture on nuclei in mass range A~45 -65 calculated by large-scale shell model Capture rates are smaller than assumed before!

Shell Model and (d, 2 He) GT strengths

Experiment vs shell model Cole, Zegers et al. , PRC 86 (2012) 015809 Iron-nickel mass range under control With increasing density, less sensitivity to details of GT distribution -> models less sophisticated than shell model suffice, e. g. QRPA

Consequences of capture rates Heger Woosley Martinez Pinedo shell model rates for Fe-Ni nuclei slower by order of magnitude important changes in collapse trajectory

Abundance distribution during collapse Electron captures drive nuclear composition towards neutron-rich unstable nuclei

Unblocking GT for nuclei with neutron numbers N>40 In Independent Particle Model, GT are Pauli-blocked for N>40 In reality, blocking does not occur due to correlations and finite T. Calculations of rates by SMMC/RPA model.

Experimental GT distributions courtesy Dieter Frekers

Neutron occupancies Data from transfer reactions: J. P Schiffer and collaborators

Convergence with truncation level Cross-shell correlations converge slowly. Hence, models like thermofield dynamics model or finite temperature QRPA, which consider only 2 p-2 h correlations, do not suffice. (Zhi et al. )

Strategy for capture rates • electron chemical potential grows faster than nuclear Qvalue • detailed resolution of strength not needed for heavier nuclei • correlations across shell gaps important • => • < A~65: diagonalization shell model for nuclei (LMP) • A>65: hybrid model • occupation numbers from shell model (SMMC) • considers correlations, also across gaps, at finite T • strength functions from RPA

Reaction rates

Collapse simulation

Neutrino interactions during collapse new developments: nucleon-nucleon bremsstrahlung, nuclear de-excitation, neutron decay -> mainly influence the mu and tau nedutrino spectra n n

Neutrino-induced spallation reactions Two-step model: 1) neutrino-nucleus excitation (many-nucleon model) 2) decay of excited state (statistical model)

Describing neutrino-nucleus reactions Neutrino energies (and momentum transfer) is low enough that allowed transitions dominate. However, forbidden contributions become important at higher neutrino energies. Hybrid model (Martinez-Pinedo, Kolbe): allowed transitions: diagonalization shell model forbidden transitions: RPA

Validation: charged-current reaction hybrid model vs QRPA shell model vs (p, n) data Martinez-Pinedo Rapaport et al. differences at small neutrino energies (sensitivity to GT details) Paar, Marketin, Vretenar

Validation: charged-current reactions anti-electron neutrino cross sections more sensitive to nuclear structure effects (like in electron capture) Zegers, Brown et al.

Neutrino-nucleus reactions in supernova simulations charged-current reactions (nu+A, nubar+A) are inverse of electron and positron captures and are considered via detailed balance neutral-current reactions (inelastic scattering): not considered until recently

Inelastic neutrino-nucleus scattering at finite temperature • Approach 1 (based on hybrid model): T=0 cross section + Gamow-Teller from (a few) excited states + contributions from inverted GT transitions (Juodagalvis, Martinez-Pinedo, Sampaio, . . . ) * Approach 2: Thermal Quasiparticle RPA consistent QRPA at finite temperature (Dzhioev, Wambach, Ponomarev)

Approach 1: Hybrid model validation from high-precision electron scattering data scattering on excited states dominates at low energies (Martinez-Pinedo, Richter, von Neumann-Cosel)

Approach 2: Thermal QRPA GT dominates, finite T effects only important at low neutrino energies Dzhioev, Wambach, Ponomarev)

Neutrino spectra from inelastic neutrino -nucleus scattering at finite T Nuclear deexcitation only important at low neutrino energies (from Juodagalvis, Martinez-Pinedo, Sampaio. . )

Effect of inelastic neutrino-nucleus scattering on in supernova simulations little effect on collapse dynamics, thermalization dominated by nu+electron no preheating of shock material BUT: neutrino scattering on nuclei acts as additional obstacle – in particular for high-energy neutrinos supernova neutrino spectrum shifts to lower energies smaller event rates for earthbound supernova neutrino detectors (Janka, Hix, Mueller, Martinez-Pinedo, Juogadalvis, Sampaio)

Consequences for supernova detectors Change in supernova neutrino spectra reduces neutrino detection rates

Neutrino-nucleus reactions and its role in nucleosynthesis neutrino-driven wind on top of proto-neutron star: neutrino absorption on nucleons sets proton/neutron ratio Ye if Ye > 0. 5: vp process if Ye < 0. 5: (weak) r-process modern simulations predict only conditions for weak r-process (up to A~130) neutrino process in outer burning shells

Possible consequences of high neutrino flux in shock-front • Anti-neutrino capture on protons produce neutrons at late times • (n, p) reactions simulate beta decays and overcome waiting points

The vp-process: basic idea

Neutrino nucleosynthesis see talk by Andre Sieverding

Neutral-current spallation cross sections RPA + stat. model Lutz Huther

Detecting supernova neutrinos carbon (scintillator): BOREXINO, Kam. LAND, . . . large Q values, transition to T=1 states fixed by experiment oxygen: Super. Kamiokande large Q values, Gamow-Teller strongly suppressed argon (liquid scintillator): ICARUS hybrid model calculation for nu_e, nuclear challenge for anti nu_e lead: HALO large cross sections as (N-Z) large, fixed by sum rules and positions of giant resonances, neutron signal difficult to predict as GT strength resides around (2 n) threshold

Cross sections for oxygen and argon hybrid model applications T. Suzuki, Otsuka

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