SLACmass Neutrino ReportArka Banerjee, Lisa Kaufman, Yun-Tse Tsai

SLAC HEP RetreatOctober 1st, 2020

Neutrinoless Double Beta Decay

• Is the neutrino its own antiparticle - i.e. is it a Majorana or Dirac fermion?

• Is Lepton Number violated?

• What is the absolute mass scale of the neutrino?

2

Neutrinoless double beta decay addresses the following questions:

Neutrinoless Double Beta Decay• Build detectors with lots of the isotope that can double beta decay -

isotopic material is both source and medium

• Ge, Xe, Te, Mo

• SLAC was a founding partner in EXO-200 and made significant contributions to the LXe TPC

• Now SLAC is involved with nEXO - a 5000 kg LXe TPC for neutrino less double beta decay

• Detectors need excellent energy resolution

• Crystals, Bolometers, TPCs, Liquid scintillator

• Experiments go deep underground

• Detectors must be made from radio-pure materials3

Neutrinoless Double Beta Decay• Experiments measure/place limits on the half-life for the

neutrinoless double beta decay process

• Current sensitivity for next-generation experiments is 1028 years

• Next generation experiments for the next 10 years will be supported by Nuclear Physics and are prioritized by the Nuclear Physics Long Range Plan

• SLAC is currently involved in the nEXO experiment

• Snowmass process is focused on efforts to improve sensitivity to 1029-30 years

4

~ 10 kg m!! ~ 1 eV ⇒ T1/2 ~ 1024 years

~ 100 kg m!! ~ 0.1 eV ⇒ T1/2 ~ 1026 years

~1000 kg m!! ~ 0.01 eV ⇒ T1/2 ~ 1028 years

~10,000 kg m!! ~ 0.001 eV ⇒ T1/2 ~ 1030 years

Snowmass LOIs• Many Snowmass LOIs on existing experiments and their reach - including reach of dark matter

detectors coming online and plans for the future (see plot from M.E. Monzani’s talk)

• For next generation - new challenges - lots of LOIs

• Need a lot of enriched isotope and even just procurement of thousands of kg of isotope - new ideas than commercial procurement

• Detector Technologies

• New readout mechanisms (e.g. simultaneous readout of ionization and scintillation for better energy resolution and lower energy thresholds, pixelated readout/Q-Pix/LArPix),

• Signal/background rejection (e.g. Ba tagging in Xe, light and heat signals, Cherenkov light and scintillation signals)

• Multipurpose facilities (e.g. DUNE, many DM experiments, etc)

• Analysis Techniques

• New methods and frameworks for simulation and machine learning

• Theoretical advances5

Synergy with Cosmology

• If the sum of neutrino masses is ~0.1 meV, cosmology experiments will measure this with high significance within the next decade

• This measurement would give a region of parameter space that provides a well-defined goal to next-next-gen DBD experiments (i.e. generation after nEXO).

Neutrino measurements from cosmology

7

Discussion highlights• Discussions about major DOE projects SLAC/Stanford already

involved in, and the prospects for detection of total neutrino mass (should be able to rule out inverted hierarchy at >5σ), and constraining sterile neutrino models (through constraints on N_eff).

• VRO (Vera Rubin Observatory), photometric - Camera built at SLAC (operational in next year or two).

• DESI, spec-z survey - Already operational.

• CMB S4 - Expected to come online in ~5 years.

• Using overlaps and cross-correlations from these experiments for reducing data systematics and breaking degeneracies for relevant neutrino parameters. (e.g. differentiating neutrino mass effects from Dark Energy effects.)

• Joint analysis of cosmology and particle physics data to constrain e.g. sterile neutrinos. (e.g. LSND and miniBoone results are difficult to reconcile with Planck data.)

8

https://gallery.lsst.org/

Letters of interest

9

Schlegel et al., 2020

https://atlas-probe.ipac.caltech.edu/

• Push to map out intermediate redshifts (z>2-10) -> Large volumes, less dominated by dark energy, theoretical modeling is easier due to lower nonlinearity. Two major types of proposals:

• Spectroscopic: e.g. MegaMapper, a spec-z follow-up of the LSST at VRO. Push to z~7. Proposal led by LBL. Space based spec-z Atlas (follow up of the Grace Roman telescope), led by JPL. For Megamapper, σ(M_nu)~0.12eV, i.e. a ~5σ detection of even the minimal mass normal hierarchy scenario.

• Line intensity mapping (21cm neutral hydrogen, mainly, but also proposals for CO and [CII] emission lines. Concrete proposal - PUMA, out of BNL (Also has SLAC involvement). Breaks degeneracy with Dark Energy. σ(N_eff)~0.013, better by a factor of 2 over CMB S4.

Letters of interest

• Push to map out intermediate redshifts (z>2-10) -> Large volumes, less dominated by dark energy, theoretical modeling is easier due to lower nonlinearity. Two major types of proposals:

• Spectroscopic: e.g. MegaMapper, a spec-z follow-up of the LSST at VRO. Push to z~7. Proposal led by LBL. Space based spec-z Atlas (follow up of the Grace Roman telescope), led by JPL. For Megamapper, σ(M_nu)~0.12eV, i.e. a ~5σ detection of even the minimal mass normal hierarchy scenario.

• Line intensity mapping (21cm neutral hydrogen, mainly, but also proposals for CO and [CII] emission lines. Concrete proposal - PUMA, out of BNL (Also has SLAC involvement). Breaks degeneracy with Dark Energy. σ(N_eff)~0.013, better by a factor of 2 over CMB S4.

10

Letters of interest

• Some proposals (including people at SLAC) for CMB follow-ups. CMB-HD, or CMB Spectral distortions. Highly constraining on N_eff (<0.01).

11

Letters of interest

• Strong SLAC/Stanford component: Push on the modeling and analysis side, with a lot of existing expertise at SLAC already. Even for current surveys, we will be theory limited on small scales(where there is potentially large amounts of information especially for neutrino mass measurements). The theory challenge is even greater when trying to combine data from different surveys. Need large simulation and pipeline development efforts. Other LoIs along similar lines have also been submitted.

12

White paper prospects

• Community-wide:

• More details for the proposed intermediate surveys: MegaMapper, ATLAS, PUMA,…

• SLAC/Stanford specific:

• Computation and modeling: Concerted push for modeling small scale nonlinearities and cross correlations to better extract various cosmological parameters. Large simulation efforts with standardized data products made available to the community. Developing forward modeling capabilities. Moving beyond the standard two-point correlation analysis (involves full accounting of propagation of data systematics). S4 surveys are expected to have σ(M_nu)~0.02eV from large scales (>~10 Mpc/h). Ability to model smaller scales, cross-correlations, and modeling higher order statistics can improve this by ~50%.

• Joint analysis of cosmological data sets with terrestrial experiments, e.g. constraining sterile neutrino parameter space.

• Roadmap for line intensity mapping experiments (maybe PUMA, maybe smaller projects?)

13

Neutrino Oscillation, Supernova Neutrino, and Others

14

Discovery of Neutrino Oscillation• Neutrino physics has developed rapidly over the

past 20 years

• Probed PMNS matrix (analogue to CKM matrix)

• A number of surprises!

• Independent, complementary experiments are necessary

• e.g. KamLAND v.s. SNO

• Used to have large effects: factor of 2-3

• Move into the precision era

• Aim for a few precent level

• Measurement with respect to neutrino energy15

Big Questions• Is there CP violation in the lepton sector? What is δCP?

• Which is the mass ordering (hierarchy)?

• Are there unknown neutrino states (sterile neutrino)?

• What can we learn from the neutrino burst when a supernova explodes?

16

Big Questions• Is there CP violation in the lepton sector? What is δCP?

• Which is the mass ordering (hierarchy)? Measured from long baseline neutrino oscillations

• Are there unknown neutrino states (sterile neutrino)? Measured from short baseline, reactor neutrino oscillations

• What can we learn from the neutrino burst when a supernova explodes?

Use the massive far detector of long baseline experiments Neutrino physics field in the next generation will strongly depend on

what is discovered in the next few years17

Long Baseline Neutrino Oscillation• Measure δCP and mass ordering via long baseline

neutrino oscillations, PMNS matrix elements

• Measure and verify the 3-flavor paradigm

• Ongoing experiments: T2K, Super-Kamiokande, IceCube, NOvA

• Next generation experiments: DUNE, Hyper-Kamiokande, JUNO, KM3NeT, THEIA(?)

• DUNE: powerful, on-axis neutrino beam covering the 1st and 2nd oscillation maxima

• Sensitive to both δCP and mass ordering

• Better characterize the oscillation probabilities

• SLAC involvement: DUNE, LArTPC detectors18

NOvA’s talk at Neutrino 2020

Short Baseline Anomalies• Search for sterile neutrinos

• Neutrino oscillation: map out L/E

• Short baseline, DAEδALUS, reactor, long baseline, atmospheric neutrinos

• Systematic uncertainty control: Neutrino fluxes (produced by hadrons, muons, reactor), cross sections

• PMNS unitarity: ντ measurements

• Cosmology: joint analyses

• BSM: heavy neutral leptons, dark sector particles

• SLAC involvement: MicroBooNE and ICARUS/SBN

• SLAC LOIs: Follow up of SBN anomaly19

310 210 110 1

eµ22sin

110

1

10

)2(e

V412

m

LSND 90%

LSND 99%(1)allowedGlobal 3+1, 3(2)allowedApp, 3e/e

SBN 3

SBN 5

(1) S. Gariazzo et al., arXiv:1703.00860 [hep-ph](2) M. Dentler et al., arXiv:1803.10661 [hep-ph]

appearanceeµ

Neutrino-4, arXiv: 2005.05301

Ann. Rev. Nucl. Vol. 69:363-387

Supernova Neutrinos• Detection of neutrinos produced from core-collapse

supernova explosions

• Understand supernova explosion mechanisms, neutrino interactions, search for new physics in extreme conditions

• Underground, massive neutrino detectors

• Data from multiple, complementary experiments desired

• LAr: sensitive to νe, water, liquid scintillators: νe

• Studies on ν-Ar cross sections, LArTPC detection and reconstruction in MeV-scale ν required

• SLAC opportunities: DUNE far detector

• LOIs: explosion physics from supernova neutrinos20

SN1987A

arXiv: 2009.10059

Neutrino Cross Section• Impact oscillation measurements and supernova

neutrino detection

• Accurate reconstruction of neutrino energy required

• Measure ν-Ar cross sections in different experiments

• GeV scale: neutrino oscillation

• MeV scale: supernova neutrinos, CEvNS

• Study e-A (e-Ar) scatterings

• Studies on detecting and reconstructing neutrons?

• SLAC opportunities: SBN, DUNE near detector, LDMX

• LOIs: e-scattering, LDMX, experiments@SNS (ORNL)21

(a)C(e, e′)

total

DISres

MECQE

50

40

30

20

10

0(b)Al(e, e′)

d2σ/dΩdω

(µb/sr

GeV

)

80

60

40

20

0(c)Ar(e, e′)

120

80

40

0(d)Ti(e, e′)

ω (GeV)2.01.61.20.80.40.0

120

80

40

0

Phys.Rev.D 102, 053001

Liquid-Argon Time-Projection Chamber• Massive LArTPC: the newly developed technology

• Challenges: MeV-scale physics, light detectors with high efficiency, reconstruction

• R&D of noble liquid TPCs widely applicable to neutrino and dark matter community

• Synergy with 0νββ, dark matter experiments

• LArTPC beyond DUNE?

• SLAC involvement: R&D of the DUNE pixelated LArTPC near detector and the 4th module of the far detector (opportunities for new designs)

• SLAC LOIs: MeV γ LArTPC telescope, machine learning based reconstruction

22

E = 500 V/cm

Cathode

Anode

Physics Beyond Standard Model• Neutrino experiments offer opportunities for

BSM searches

• Beam induced BSM: intense beam and near detectors. e.g. dark sector, heavy neutral leptons

• Astroparticle physics and rare processes: underground, massive far detectors. e.g. boosted dark matter, nucleon decays

• Complementary to dark matter experiments, e.g. LZ, LDMX

• SLAC involvements: SBN and DUNE

• LOIs: Boosted dark matter, millicharged, dark sector particles, heavy neutral leptons, …

23

106 20 30 40m¬ (GeV)

10°7

10°6

10°5

10°4

10°3

10°2

g4 Z0

∞ = 1.1

DUNE

PICO-60L, p

106 20 30 40m√ (GeV)

Phys.Rev.D 101, 052001

arXiv: 1912.05558

Summary• Independent, complementary, “redundant” experiments are the key for

uncovering new physics

• Supporting experiments are essential

• Efforts on joint analyses and theory developments

• Synergies between neutrino and other SLAC groups

• SLACmass neutrino discussion https://indico.slac.stanford.edu/category/31/

• List of LOIs: https://docs.google.com/spreadsheets/d/1k26MQtYRp1COAMcD_mTvDrKZL5tI2ZdfOH_N_JFTlp8/edit?usp=sharing

24