Neutrino interactions in SN and in the laboratory
Chuck Horowitz, [email protected], INT, Feb. 2020 2020 TALENT Courses
- The TALENT initiative, Training in Advanced Low Energy Nuclear Theory, aims at providing an advanced and comprehensive training to graduate students and young researchers in all aspects of low-energy nuclear theory. TALENT offers intensive three-week courses on a rotating set of topics. See http://www.nucleartalent.org
- Three TALENT courses will be offered in 2020:
- Atomic Nuclei as Open Quantum Systems: Unifying Nuclear Structure and Reactions will be held at the INT in Seattle, WA, USA from June 22 to July 10, 2020. The principal lecturers will be Christian Forssén (Chalmers), Witek Nazarewicz (MSU), Marek Ploszajczak (GANIL), and Alexander Volya (FSU). https:// nucleartalent.github.io/NuclearOQS2020/
- Density Functional Theory and Self-Consistent Methods will be held at LBNL, in Berkeley, CA, USA from July 6 to July 24, 2020. The principal instructors will be Nicolas Schunck (LLNL), Michael Forbes (WSU), Heiko Hergert (MSU), and Tomás Rodríguez (Univ. Autonoma de Madrid). https://indico.frib.msu.edu/event/32/
- Machine Learning and Data Analysis for Nuclear Physics will be held at the ECT* in Trento, Italy The from June 22 to July 10, 2020. The principal instructors will be Daniel Bazin (MSU), Morten Hjorth-Jensen (MSU), Michelle Kuchera (Davidson), Sean Liddick (NSCL), and Raghuram Ramanujan (Davidson). http://www.ectstar.eu/node/4472 Neutrino interactions in SN and in the laboratory
• Supernova neutrino detectors • Spallation Neutron Source (SNS) neutrino experiments • Parity violating measurements of neutron density • Nucleon-nucleon correlations in SN • Muons in SN and flavor physics Detecting Supernova Neutrinos Super Kamiokande • SN radiate the gravitational binding energy of a neutron star, 0.2 Msunc2, as 1058 neutrinos in ~10 s
• Historic detection of ~20 neutrinos from SN1987A 40 m • Expect several thousand events from next galactic SN in Super Kamiokande: 32 kilotons of H2O + phototubes. Good antineutrino detector. • Deep Underground Neutrino Experiment (DUNE) in DUNE South Dakota plans 40 kilotons of liquid Ar to study oscillations of Fermilab neutrinos. Good neutrino detector. • Hyper Kamiokande is very large version of SuperK. Expect 100,000 events. Good for late times.
DUNE Supernova neutrino detectors
• Important to measure individual flavors –Anti-electron neutrinos: Super-K, JUNO, Hyper-K, Ice Cube… –Electron neutrinos: DUNE, need to measure Ar charged current cross section at SNS –Mu and tau neutrinos: Good neutral current detector… • Can we measure total E in (active) neutrinos Etot to 10% for a Galactic SN? Total E radiated in neutrinos Etot
• Binding E of NS ~ 3/5 GMns2/R • Uncertainties –Distance to SN. Assume determined by E+M observations. –Radius of NS R: NICER promised NASA 5%, combination of GW170817, NICER, chiral EFT may give R to 10%???
–Mass of NS Mns: Assume mass of preSN star known? SN simulations now suggest Mns given preSN star?? What if Etot is big?
• Only option, Mns must be large. A 2Msun star has twice BE of a 1.4Msun star. Note GW170817 likely rules out small R.
• What if Etot is small?
• Very likely Mns>1.2Msun and GW170817 says R<13 km. There is a minimum expected BE for a NS. • Would provide strong evidence for new particle physics: sterile nu, axions, light dark matter particles … Neutrino-Nucleus Elastic
• Neutrino-nucleus elastic scattering can make a great SN detector. –Large coherent cross section ~ N2. –All six flavors of nu and anti-nu contribute. –All mass of detector active (factor of ~10 compared to H mass fraction in anti-nue ) • Yields of tens of events per TON compared to 100s of events per KILO- TON for conventional detector and SN at 10 kpc. Large dark matter detector
• May be good way to cleanly measure Etot. • Independent of (active) nu oscillations. • Need low threshold (~5 keV??) but lots of work on this to detect lower mass WIMPS. • Need large size, 10+ tons, for statistics. • Backgrounds probably fine if ok for dark matter. • Systematic erros –Quenching factor –Energy scale –?? • Yield in events per ton for a SN at 10 kpc • Large 100+ ton liquid Ar dark matter experiment could be an exciting SN detector.
DARWIN talks about 40 tons Xe, could have larger Ar detectors.
Darkside-20k will have 23 tons active of Ar. The next detector Argo could have 300t of Ar and 1,000+ events for a SN.
C. J. Horowitz, K. J. Coakley, and D. N. McKinsey, Phys. Rev. D 68 (2003) 023005 Charged current interactions and nucleosynthesis R-process nucleosynthesis: origin of heavy elements such as gold, uranium
SN1987a According to many textbooks, supernovae are the site of the r-process. Why are the textbooks wrong?
12 SN neutrinos and nucleosynthesis
Y =0.4 • Possible site of r-process is the Yep=0.4 neutrino driven wind in a SN. Wind • Ratio of neutrons to protons in n rich Wind p wind set by capture rates that rich
depend on neutrino and anti- Super-K neutrino energies.
+ Phys.Rev. D65, 083005 νe + n → p + e ν¯e + p → n + e
• Composition of wind depends DUNE on anti-neutrino energy (Y-axis) • ~20 events from SN1987A, and neutrino energy (X-axis). thousands of events from next • Because of robust galactic SN. Important to observe neutrino physics we find both anti-neutrinos (SK…) and wind is not n rich enough neutrinos (DUNE, HALO-1kT) for main r-process! • Measure Ar CC cross sec. at SNS! SNS Neutrino Experiments • Spallation neutron source (SNS) has large neutrino flux from pion decay at rest. Similar in spectrum to SN neutrinos. • Coherent neutrino-nucleus experiments. • Important to measure nu-Ar charged current cross section “to calibrate” DUNE for SN. • Can measure Pb (Fe?) cross sections for HALO-1kT • Neutrino induced fission exp. probably possible. Fission may play an important role in r-process.
14 Coherent neutrino- nucleus elastic scattering • Original results for CsI. • Now results for Ar. • Very interesting probe of nonstandard neutrino interactions. • Can measure neutron density • Don’t expand form factor in moments
15 208Pb PREX Spokespersons K. Kumar R. Michaels K. Paschke P. Souder G. Urciuoli
PREX measures how much neutrons stick out past protons (neutron skin). • 16 Parity violating electron scattering neutron radius Experiments
Experiment Nucleus Error in Rn
MAINZ C12 12C ~ 0.5%
CREX 48Ca 0.6%
PREX (PREX II) 208Pb 3% (1%)
MREX 208Pb 0.5%
17 Parity Violation Isolates Neutrons
0 • In Standard Model Z boson • Apv from interference of couples to the weak charge. photon and Z0 exchange. In • Proton weak charge is small: Born approximation p 2 2 2 Q =1− 4sin ΘW ≈ 0.05 GF Q FW (Q ) W = Apv 2 • Neutron weak charge is big: 2πα√2 Fch(Q ) n sin( ) QW = −1 2 3 Qr FW (Q )= d r ρW (r) • Weak interactions, at low Q2, ! Qr probe neutrons. • Model independently map out • Parity violating asymmetry Apv is distribution of weak charge in cross section difference for a nucleus. positive and negative helicity •Electroweak reaction electrons free from most strong dσ/dΩ+ dσ/dΩ− Apv = − interaction dσ/dΩ+ + dσ/dΩ− uncertainties.
18 PREX in Hall A Jefferson Lab
•PREX: ran in 2010. 1.05 GeV electrons elastically scattering at ~5 deg. from 208Pb
APV = 0.657 ± 0.060(stat) ± 0.014(sym) ppm
•From Apv I inferred neutron skin: Rn - Rp= 0.33+0.16-0.18 fm. •Next runs •PREX-II: 208Pb with more statistics. Goal: Rn to ±0.06 fm. Ran summer ’19.
•CREX: Measure Rn of 48Ca to ±0.02 fm. Microscopic calculations feasible for light n rich 48Ca to relate Rn to three neutron forces. Running now. R. Michaels 19 Physics Data Analysis for PREX, CREX • 1.05 GeV electrons elastically scattering at ~5 deg. from 208Pb
APV = 0.657 ± 0.060(stat) • E+M charge Weak charge ± 0.014(sym) ppm density density (gray) determined by -1 • Weak form factor at q=0.475 fm : PREX FW(q) = 0.204 ± 0.028 • Radius of weak charge distr. RW = 5.83 ± 0.18 fm ± 0.03 fm • Compare to charge radius Rch=5.503 fm --> weak skin: RW - Rch = 0.32 ± 0.18 ± 0.03 fm • First observation that weak charge density more extended than (E+M) charge density --> weak skin. • Unfold nucleon ff--> neutron skin: Rn - Rp= 0.33+0.16-0.18 fm • Phys Rev Let. 108, 112502 (2012), Phys. Rev. C 85, 032501(R) (2012) How do supernovae explode?
• Situation is not so clear.
• Many Two-dimensional simulations with realistic nu transport explode.
• Very costly 3D simulations may be less likely to explode than 2D.
• Possibilities: 1) asymmetries in pre- SN star may aid explosion, 2) resolution / accuracy of nu transport, 3) Equation of state, 4) Neutrino interactions — perhaps important corrections have been left out. � interactions in SN matter
�e + n —> p + e (Charged current capture rxn)
� + N —> � + N (Neutral current elastic scattering, important opacity source for mu and tau �)
• Neutrino-nucleon neutral current cross section in SN is modified by axial or spin response SA, and vector response SV, of the medium.
• Responses SA, S V —> 1 in free space. Normally SA dominates because of 3ga2 factor. Neutrinosphere as unitary gas
• Much of the action in SN at low densities near neutrinosphere at n ~ n0/100 (nuclear density n0).
• Average distance between two neutrons near neutrinosphere is less than NN scattering length.
19 fm nn scattering length
8.5 fm Average distance between two neutrons at n0/100 1.4 fm Range of NN force. (Effective range 2.8 fm)
• Because of the long scattering length one can have important correlations even at low densities.
• Two neutrons are correlated into spin zero 1S0 state that reduces spin response SA<1. Do the spin correlations of a unitary gas help a SN explode? Virial Expansion for Unitary Gas - In high T and or low density limit, expand P in powers of fugacity z=Exp[chemical pot/T]
- Long wavelength response:
- Axial response: Unitary gas virial coefficients
- Second order b2 from integral over two particle scattering phase shifts. b2 known for Unitary, neutron and nuclear matter.
- Third order b3 from partition function for three interacting particles in a harmonic trap. Then take limit trap frequency —> 0.
- 4th order b4 from Path Integral Monte Carlo simulations.
- b3, b4 only known for unitary gas.
- For Unitary gas, bn independent of T. Responses only function of Fermi energy/ temperature. Can the spin response of a unitary gas help a supernova explode?
- Well posed question.
- Helpful to think of neutrinos interacting with a unitary gas as a special reference system for nuclear matter. Better to model neutrinosphere region as a unitary gas instead of a free (Fermi) gas as is often done.
- Many theoretical results for a unitary gas and many experimental results for cold atoms.
- Spin response <1 reduces scattering opacity.
- Effect may be important even at low ~1012 g/cm3 densities because of the large scattering length.
- Probably helps 2D (and 3D?) simulations explode perhaps somewhat earlier??? Dynamic Spin Response of a Strongly Interacting Fermi Gas [S. Hoinka, PRL 109, 050403]
6Li atoms
T=0.1TF, k=5kF
=k2/2m
SA(k,w) is solid line and squares, while dashed line is SV(k,w). Static structure factors: SV(k) =∫dwSV(k,w), SA(k) =∫dwSA(k,w) Unitary gas response arXiv:1708.01788
1.5 2nd order Unitary 2nd order n matter
1 4th order Unitary V , S A S
0.5 Fit to viral + RPA
0 0 0.5 1 1.5 F/T Shock radius vs time for 2D SN simulations
All 2-D SN simulations by Burrows et al [arXiv:1611.05859] with correlations (SA<1) explode (solid lines) while 12 and 15 Msun stars fail to explode, and 20, 25 Msun explode later, without correlations (SA=1).
Preliminary 2D SN simulations by Evan O’Connor for 12 to 25 Msun stars explode earlier (lighter color) if correlations (SA<1) included.
Sensitivity of SN dynamics motivates better treatments of neutrino interactions and NN correlations. E. O’Connor, S. Couch, Z. Lin Flavor Physics SN Quantum Numbers
Precollapse SN Neutron Star # nu radiated 1058 Baryon # 1057 1057 1057 Electron # 1057 —> 1056 Muon # 0 —> 1055 Tau # 0 1054 0 Strangeness 0 —> ?
• Deleptonization: During SN electron # of 1057 is radiated.
• Muonization: During SN muon # of minus1055 is radiated.
• Tau #: Produce equal numbers of nu-tau, anti-nu-tau. However anti-nu_tau leave faster because of weak magnetism leaving star nu-tau rich [PLB 443 (1998) 58]. Macroscopic next generation matter and the changing of the generations
- A SN contains astronomical numbers of 2nd and third generation particles. It may be uniquely sensitive to new flavor physics.
- Example: muon to electron conversion: μ+A —> e+A could increase the role of muons. Could flavor changing
“coherent” interactions impact SN? �e+A —> ��+A SN simulation 0.4s after bounce with muons and charged current rxns for nu- mu. Also helps reduce PNS radius and helps explosion. —R. Bollig et al Phys. Rev. Lett. 119, 242702 Neutrino interactions in SN and in the laboratory
• PREX/ CREX: K. Kumar, P. Souder, R. Michaels, K. Paschke, G. Urciuoli… • Graduate students: Zidu Lin (2018), Jianchun Yin
C. J. Horowitz, Indiana U., [email protected] INT, UW, Feb. 2020