Diffuse SN Neutrino Background (DSNB) in liquid Argon Cecilia Lunardini Arizona State University

Agenda O Introduction O theory and motivation O current upper bounds O O detectability O physics potential O discussion: theory needs

Introduction theory and motivation current upper bounds

Neutrinos from cosmological SNe O diffuse flux from all supernovae O ~ 40% cosmological O dominated by z>1 at E = 10 MeV total z = 0 – 1 z = 1 – 2 z = 2 – 3

Unique physics potential O new, guaranteed flux O first neutrino picture of SN population (true tracer of core collapse) O diversity (rare types: failed SN, ONeMg,..) O Typical spectrum parameters O SN history at high z O cosmological neutrino detection O new physics over cosmological base-line

Why important for DUNE? O unique potential for ν e O might be first observation of neutrinos (not anti- neutrinos) from SNe O probe the population-averaged ν e, ν x spectrum O important for synthesis of heavy elements O test oscillations/new physics in neutrino channel

C.J. Horowitz, Phys.Rev. D65 (2002)

Main ingredients Cosmological rate of supernovae Neutrino flux at production + Oscillations Redshift E’ = E(1+z) Cosmology Ando & Sato, 2004, New J. Phys. 6, 170, Lunardini arXiv: , Beacom Ann.Rev.Nucl.Part.Sci. 60 (2010)

Cosmological SN rate O grows with ~ (1+z) 3.3 O factor ~ 2 discrepancy at z=0 O direct counting vs star formation rate estimate Hopkins & Beacom, 2006, ApJ. 651, 142, Horiuchi, Beacom & Dwek, 2009, PRD79, , Madau & Dickinson, Ann.Rev.Astron.Astrophys. 52 (2014), Horiuchi et al., ApJ. 738 (2011), Cappellaro et al., arxiv: from star formation rate from SN observations

Flux at production O alpha-spectrum: Keil, Raffelt & Janka, 2003, Astrophys. J. 590, 971 x=μ,τ

Oscillations O permutation : O averaged probabilities: matter (MSW) driven p ~ 0 ~ 0.32 C.L. & I. Tamborra, JCAP 1207 (2012) no oscill. MSW only MSW + collective

Effective description O unoscillated alpha-spectrum with effective E 0 and α effective, E 0 = 15.7 MeV mixed, E0e = 12 MeV, E0x=18 MeV

O anti-nue, inverse beta decay search: O nue, indirect from anti-nue limit: O from maximizing the ratio of nue/anti-nue fluxes, after oscillations Super-K limits Bays et al., Phys. Rev. D 85, , 2011 C.L., Phys.Rev. D73 (2006), updated

natural region α =2 α =4 α =2 α =4 C.L and A. Warren, in preparation nue anti-nue

Near future searches technologymassReactionEnergy window Events/(1 0 yrs) Liquid Argon (DUNE) 40 ktnue + Ar, CC (100% eff.) MeV~ Water + Gadolinium (GADZOOKS!) 22.5 ktAnti-nue, inverse beta 11 – 40 MeV Liquid Scint. (JUNO, RENO- 50) 17 ktAnti-nue, inverse beta 11 – 40 MeV for moderately conservative SN rate, R SN (z=0) = yr -1 Mpc -3

detectability

Cross section Suzuki & Honma, 2013 Kolbe et al., 2003 Kolbe, Langanke, Martinez-Pinedo and Vogel P 2003 J. Phys. G Suzuki & Honma, Phys.Rev. C87 (2013) 1, ~ + 40% nue + Ar, CC

Energy window: ~ 19 – 40 MeV O hep solar neutrinos, E < 19 MeV O atmospheric neutrinos, latitude dependent O from FLUKA (rescaled by 1.5 for latitude) M. Vagins, LBNE working group, 2010Battistoni et al., Astropart. Phys. 23, 2005

DUNE-specific backgrounds  nuclear recoil from fast neutron O distinguishable topology  cosmic muon decays O distinguishable topology  spallation products O below energy window  radioactive impurities, particle misidentification, various technical issues, etc. O distinguishable or below energy window Cocco et al., JCAP 0412 (2004) 002, M. Vagins, LBNE topical group report, 2010

Event rates

p=0.32

E/MeVHotWarmColdatmospheric p =0.32, t= 10 years E/MeVHotWarmColdatmospheric p =0, t= 10 years Kolbe et al cross section moderately conservative SN rate, R SN (z=0) = yr -1 Mpc -3

LAr 34 kt MeV DSNB atmos. Homestake atmos. SuperK Effective α -spectrum α = 1.8 (optimistic) optimistic SNR “natural” range

DSNB + atmos. 3 σ atmos. Homestake “natural” range

Increasing α ; α = 2 -4 DSNB atmos. Homestake

LAr 34 kt MeV DSNB atmos. Homestake Effective α -spectrum α = 1.8 (optimistic) optimistic SNR “natural” range

DSNB + atmos. 3 σ atmos. Homestake “natural” range

Increasing α ; α = 2 -4 atmos. Homestake

ν e s ensitivity summary natural region α =2 α =4 DUNE, 10 years E = 19 – 29 MeV probability of background only : < C.L and A. Warren, in preparation

physics potential

Basic spectrum information O Main testable parameter : CL, PRD75 (2007) …. no results available, future work.

Failed SNe? O direct collapse into black hole O up to 50% of all collapses O appear in SN simulations O more luminous, hotter spectrum! Liebendörfer et al., ApJS, 150, 263, K. Sumiyoshi et al., PRL97, (2006), T. Fischer et al., (2008), ; K. Nakazato et al., PRD78, (2008); nue anti-nue nux

O up to factor ~ 2 enhancement O spectral distortion f NS =0.78 f NS =0.91 CL, PRL 102, , 2009 J. Keehn & CL, PRD85 (2012) BH NS

BH total

History of core collapse O test z -evolution of rate of all collapses O including failed, faint, obscured SNe No evolution

Physics beyond the SM O neutrino decay O DSNB sensitivity : τ /m>10 10 s eV -1 O current: τ /m>10 5 s eV -1 (SN1987A) Ando, PLB 570, 11 (2003) Fogli et al., PRD 70, (2004)

O exotic absorption O test of dark energy Goldberg, Perez and Sarcevic, JHEP 0611, 023 (2006) Farzan and S. Palomares-Ruiz, JCAP 1406, 014 (2014) Hall et al., hep-ph/

O mimicking the DSNB : O DM decay/annihilation O exotic solar antineutrinos Palomares-Ruiz and Pascoli, PRDD 77, (2008) Palomares-Ruiz, PLB 665, 50 (2008) Bernal, Martn-Albo and Palomares-Ruiz, JCAP 1308, 011 (2013) Raffelt and Rashba, Phys. Atom. Nucl. 73, 609 (2010)

Discussion theory needs

Summary: O in 10 years, DUNE can test a substantial part of the parameter space O if background conditions are ideal O unique nue sensitivity : complementary to SuperK-Gd and JUNO O main physics potential O nue spectrum (to be studied) O phenomenology of cosmological and/or failed/faint/obscured SNe

Theory needs O precise nue Ar CC cross section, differential in electron energy O site-specific low energy atmospheric neutrino modeling O detailed detector-specific backgrounds O creative background reduction (directionality?)

Backup

No nuclear recoils from fast neutrons will be able to produce an event which looks like a single electron in the energy window. Unlike in water Cherenkov detectors, liquid argon detectors do not suffer from sub-Cherenkov muons decaying into electrons and faking the SRN signal, as no muons (or evidence of their decays) should escape detection in the detector. No spallation products will be produced which generate electrons in the energy range of interest without clear evidence of their parent muon allowing the event to be removed from consideration. The full family of spallation daughters of argon does not seem to be known, but it must include all possible oxygen spallation products, e.g. 11 Li, a  - emitter, Q = 20.6 MeV. No radioactive background or impurity, electronic effect in the detector, track-finding inefficiency, particle misidentification, or failed event reconstruction will ever be able to lead to a signal in the energy range of interest. M. Vagins, LBNE topical group report, 2010

Failed SNe? direct collapse into black hole – up to 50% of all collapses – appear in SN simulations – explain the missing progenitor problem? Smartt, Publications of the Astronomical Society of Australia, Vol. 32, (2015)

O matter-driven (MSW) oscillations dominate the burst- integrated flux

other effects are ~10% or less – Basic sensitivity to MSW-oscillated spectra a) t=0.5 pb spectrum, M=10.8 Msun, no oscillations b) t-integrated spectrum, M=10.8 Msun, no oscillations c) t-integrated spectrum, M=10.8 Msun, with MSW oscillations d) t-integrated spectrum, M=10.8 Msun, MSW + collective oscilations e) t-integrated spectrum, all masses, MSW + collective oscilations f) Same as e) for suppressed SNR normalization Error bars: conservative uncertainty due to SNR error

Questions that can be answered O Do supernovae emit ν e ? O only antineutrinos seen from SN1987A O Does the SN rate increase with z ? O uncertain from astrophysics O Are SNe at z > 1 ? O not seen astronomically!

FAQs O what if we see a galactic SN? Will the DSNB be useless? O NO, a galactic SN is just one, the DSNB is a picture of the whole population, including dark SN, ONeMg SN, high z SN, low- or zero- metallicity SN, etc. O data from local SN will remove degeneracies to extract SN population parameters (rate, etc.)

LAr 10 kt MeV DSNB atmos. Homestake atmos. SuperK Effective α -spectrum α = 1.8 Highest SNR “natural” range Atmospheric from FLUKA, Battistoni et al., 2005

DSNB + atmos. 3 σ

Potential? O upper bounds O ~ 3 σ discovery for fortunate scenarios O uncertainties might help O for NH (p=0), ν e flux is higher than anti- ν e ! O statistics barely enough O need to know all backgrounds very well

Spectrum tail ? O no SN1987A data at E> 40 MeV

No tail beyond 40 MeV

Uncertainties, degeneracies Large (~20% or more) small (~ 10% or less) Degenerate? Avg. energy E 0 X with α (quasi) luminosityXWith SNR norm. α parameterXwith E 0 (quasi) mass hierarchyXwith E 0 (quasi) SNR power lawX SNR normaliz.XWith luminosity Prog. dependence X (?) Collective oscill. X Shock oscill. effect X

Current: upper bounds

O DUNE will be the only large LAr detector in the world O the only one capable to detect cosmological SN nu_e O first nu_e data from SNe O might be the first new data from SNe! O to not search for the DSNB is not acceptable O thousands of papers were written on 20 events from SN1987A !

C.J. Horowitz, Phys.Rev. D65 (2002) 11 B overproduction factor, Yoshida, Kajino and Hartmann, 2005 PRL