Neutrino Oscillation Parameters: Present Status and Future Roadmap
Sanjibjg Kumar Agarwalla [email protected]@iopb.res.in
Institute of Physics, Bhubaneswar, India
S. K. Agarwalla, 82nd Annual Meeting of IASc, IISER Bhopal, 4th November, 2016 Exciting Phase in High Energy Physics
New Findings in all the Three Frontiers
The Energy Frontier: Discovery of Higgs at LHC
The Intensity Frontier:
Discovery of the smallest mixing angle θ13 The Cosmic Frontier: First Direct Detection of Gravitational Wave at Advanced LIGO
A New Era of Gravitational Wave Astronomy
Intensity Frontier: Neutrino properties: A window to our Universe and New Physics
Discovery of moderately large value of θ13 has crucial consequences for future theoretical and experimental efforts
Non-zero θ13 is the gateway to discover leptonic CP violation & to measure δCP
S. K. Agarwalla, 82nd Annual Meeting of IASc, IISER Bhopal, 4th November, 2016 1/24 The Standard Model: Massless Neutrinos The Standard Model is a gauge theory & it unifies strong, weak & electromagnetic forces
• 3 active neutrinos: νe , νμ , ντ • Neutral elementary particles of Spin ½ • Only couple to weak force (& gravity) • Only left handed neutrinos • There are no right-handed neutrinos • No Dirac Mass term:
3-fold repetition of the same representation! Neutrinos are massless in the Basic SM Over the past decade, marvelous data from world class neutrino experiments firmly established that they change flavor after propagating a finite distance
Neutrino flavor change (oscillation) demands non-zero mass and mixing
Non-zero ν mass: first experimental proof for physics beyond the Standard Model
!! An extension of the Standard Model is necessary !!
S. K. Agarwalla, 82nd Annual Meeting of IASc, IISER Bhopal, 4th November, 2016 2/24 Neutrino Physics: An Exercise in Patience Three most fundamental questions were being asked in the past century…
1. How tiny is the neutrino mass? (Pauli, Fermi, 30s) Planck + BAO + WMAP polarization data: upper limit of 0.23 eV for the sum of ν masses! Planck Collaboration, arXiv:1303.5076 [astro-ph.CO]
2. Can a neutrino turn into its own antiparticle? (Majorana, 30s) Hunt for ν-less Double-β decay (Z,A Z+2, A) is still on, demands lepton number violation! Nice Review by Avignone, Elliott, Engel, Rev.Mod.Phys. 80 (2008) 481-516
3. Do different ν flavors ‘oscillate’ into one another? (Pontecorvo, Maki-Nakagawa-Sakata, 60s) B. Pontecorvo, Sov. Phys. JETP 26, 984 (1968) [Zh. Eksp. Teor. Fiz. 53, 1717 (1967)]
Last question positively answered only in recent years. Now an established fact that neutrinos are massive and leptonic flavors are not symmetries of Nature!
Recent measurement of θ13, a clear first order picture of the 3-flavor lepton mixing matrix has emerged, signifies a major breakthrough in ν physics!
Discovery of ν oscillations: Neutrinos have mass 2015 Nobel Prize Takaaki Kajita (Super-K) & Arthur B. McDonald (SNO) S. K. Agarwalla, 82nd Annual Meeting of IASc, IISER Bhopal, 4th November, 2016 3/24 Golden Age of Neutrino Physics (1998 – 2016 & Beyond)
Double Chooz, Daya Bay, RENO IceCube NOvA
Over the last seventeen years or so, precious data from world-class experiments
Data from various neutrino sources and vastly different energy and distance scales
We have just started our journey in the mysterious world of neutrinos
S. K. Agarwalla, 82nd Annual Meeting of IASc, IISER Bhopal, 4th November, 2016 4/24 Neutrino Oscillations in 3 Flavors
It happens because flavor (weak) eigenstates do not coincide with mass eigenstates
Three mixing angles: θ23 , θ1313 , θ12 and one CP violating (Dirac) phase δCP
3 mixing angles simply related to flavor components of 3 mass eigenstates
Over a distance L, changes in the relative phases of the mass states may induce flavor change
2 independent mass splittings and , for anti-neutrinos replace δCP by -δCP S. K. Agarwalla, 82nd Annual Meeting of IASc, IISER Bhopal, 4th November, 2016 5/24 Neutrino Oscillations in Matter
Neutrino propagation through matter modify the oscillations significantly
Coherent forward elastic scattering of neutrinos with matter particles
Charged current interaction of νe with electrons creates an extra potential for νe
Wolfenstein matter term: or
Ne = electron number density , + (-) for neutrinos (anti-neutrinos) , ρ = matter density in Earth
Matter term changes sign when we switch from neutrino mode to anti-neutrino mode
even if δCP = 0, causes fake CP asymmetry
Matter term modifies oscillation probability differently depending on the sign of Δm2
Resonant conversion – Matter effect
Resonance occurs for neutrinos (anti-neutrinos) if Δm2 is positive (negative)
S. K. Agarwalla, 82nd Annual Meeting of IASc, IISER Bhopal, 4th November, 2016 6/24 Oscillation Parameters At Present
Relative 1σ Precision
4%
10%
55%%
(Not Known)
2.4%
1.9%
Gonzalez-Garcia, Maltoni, Schwetz, http://www.nu-fit.org S. K. Agarwalla, 82nd Annual Meeting of IASc, IISER Bhopal, 4th November, 2016 7/24 Fundamental Unknowns in Neutrino Oscillation
1. What is the hierarchy of the neutrino mass spectrum, normal or inverted?
• The sign of is not known
• Currently do not know which neutrino is the heaviest?
• Only have a lower bound on the mass of the heaviest ν
2. What is the octant of the 2-3 mixing angle, lower (θ23 < 45°) or higher (θ23 > 45°)?
Measure θ23 precisely, Establish deviation from maximality at higher C.L. Then look for Octant
2. Is there CP-violation in the leptonic sector, as in the quark sector?
Mixing can cause CP-violation in the leptonic sector (if δCP differs from 0° and 180°) Need to measure the CP-odd asymmetries: (α≠β)
With current knowledge of θ13, resolving these unknowns fall within our reach Sub-leading 3 flavor effects are extremely crucial in current & future oscillation expts
S. K. Agarwalla, 82nd Annual Meeting of IASc, IISER Bhopal, 4th November, 2016 8/24 Our work in light of recent oscillation data
We have made significant contributions in addressing the fundamental issues related to neutrino mixing and oscillations
Recently, in a series of papers, we have explored in detail the physics reach of various currently running, upcoming, & future neutrino oscillation experiments, focusing on sub-leading three flavor effects, which will be the
key to discover the ν mass hierarchy, octant of θ23, & leptonic CP-violation
We are playing a leading role in optimizing the vital parameters of the oscillation facilities, and to perform a detailed physics comparison among them, useful for future neutrino roadmap
Is there a light eV-scale sterile neutrino? Do neutrinos feel new non-standard interactions arising from effective four-fermion dimension six operator? These issues are extremely important in the precision era and recently, we have performed some new studies along this direction
Today, I will briefly discuss only the work that I have done after joining Institute of Physics (IOP), Bhubaneswar on 1st January, 2013
S. K. Agarwalla, 82nd Annual Meeting of IASc, IISER Bhopal, 4th November, 2016 9/24 Analytical Understanding of Neutrino Oscillation Probability
S. K. Agarwalla, 82nd Annual Meeting of IASc, IISER Bhopal, 4th November, 2016 10/24 Matter Effect Parameter a
−5 2 ⎛ ρ ⎞ ⎛ E ⎞ a 22GF NeE 7.63×10 (eV ) ⎜ ⎟ ⎜ ⎟ ⎝g/cm3 ⎠ ⎝GeV⎠ Green (Red) Line: ρL = 54000 (32000) km.g/cm3 5.5 Matter effects play an important role 40 5.0 Mixing angles and and mass-squared
differences run with the matter effect 35 4.5 parameter a GeV 3 2 cm
eV We present simple analytical
4.0 30 5 g approximations to these running Ρ 10 parameters using the Jacobi method
3.5 E 25 a We show that for large θ13, the running 3.0 of θ23 and δCP can be neglected, simplifying the probability expression 20 2.5 0 2000 4000 6000 8000 10 000 12 000 We need to rotate only θ and θ L km 12 13
Agarwalla, Kao, Takeuchi, JHEP 1404, 047 (2014)
S. K. Agarwalla, 82nd Annual Meeting of IASc, IISER Bhopal, 4th November, 2016 11/24 a-dependence of effective mixing angles
Π Π 2 2
Θ13' NH 3 Π 3 Π 8 8
Π Π Θ ' 4 12 4
Π Π 8 8
Θ13' IH 0 0 4 3 2 1 0 1 2 Β
a δm2 −β , 21 0.17 2 ε ε 2 ≈ δm31 δm31
Agarwalla, Kao, Takeuchi, JHEP 1404, 047 (2014)
S. K. Agarwalla, 82nd Annual Meeting of IASc, IISER Bhopal, 4th November, 2016 12/24 Accuracy of Our Method and Comparison with Existing Literature L8770 km, Δ0, Normal Hierarchy 0.8 Exact This work 0.6 Cervera et al.
e Asano Minakata 0.4 Ν Freund Μ Ν
P Akhmedov et al. 0.2
0.0
2 4 6 8 10 12 E GeV Agarwalla, Kao, Takeuchi, JHEP 1404, 047 (2014) Other analytical expressions suffer in accuracy due to their reliance on
expansion in θ13, or in simplicity when higher order terms in θ13 included
Our method gives accurate probability for all channels, baselines and energies
S. K. Agarwalla, 82nd Annual Meeting of IASc, IISER Bhopal, 4th November, 2016 13/24 Superbeams
Traditional approach: Neutrino beam from pion decay
Current Generation Experiments:
Tokai to Kamioka (T2K) : 295 km(2.5o off-axis, 1st Osc. Max = 0.6 GeV) J-PARC Beam: 0.75 MW, Total 7.8 × 1021 protons on target, 5 years ν run Detector: Super-Kamiokande (22.5 kton fiducial volume) FNAL to Ash River (NOvA) : 810 km (0.8o off-axis, 1st Osc. Max = 1.7 GeV) NuMI Beam: 0.7 MW, Total 3.6 × 1021 protons on target, 3 yrs ν + 3 yrs anti-ν Detector: 14 kton Totally Active Scintillator Detector (TASD)
S. K. Agarwalla, 82nd Annual Meeting of IASc, IISER Bhopal, 4th November, 2016 14/24 Physics Potential of T2K & NOvA in light of large θ13
Combined data from T2K and NOvA are expected to provide the first hint for neutrino mass hierarchy, leptonic CP violation, and octant of θ23
S. K. Agarwalla, 82nd Annual Meeting of IASc, IISER Bhopal, 4th November, 2016 15/24 Mass Hierarchy & CP Violation Discovery with T2K and NOνA
Mass Hierarchy Discovery, NH true CP Violation Discovery, NH true 12 8 New NOvA (3+3) New NOvA (3+3) Old NOvA (3+3) Old NOvA (3+3) New NOvA (3+3) + T2K (5+0) 7 New NOvA (3+3) + T2K (5+0) 10 6 8 5 11% CP coverage Δ χ2 6 Δ χ2 4 95% C.L.
95% C.L. 45% CP coverage 3 90% C.L. 4 38% 90% C.L. 2 2 55% CP coverage 1
0 0 −180 −90 0 90 180 −180 −90 0 90 180 δ δ CP (true) CP (true)
Agarwalla, Prakash, Raut, Sankar, JHEP 1212, 075 (2012)
Adding data from T2K and NOνA is useful to kill the intrinsic degeneracies
CP asymmetry ∞ 1/sin2θ13, large θ13 increases statistics but reduces asymmetry, Systematics are important
S. K. Agarwalla, 82nd Annual Meeting of IASc, IISER Bhopal, 4th November, 2016 16/24 Resolving Octant of θ23 with T2K and NOνA Octant Discovery, NOνA+T2K[2.5+2.5], NH true 180 2σ 3σ global bestfit MINOS 90
0 (true) [degree] CP δ
-90
-180 35 37 39 41 43 45 47 49 51 53 55 θ 23 (true) [degree]
Agarwalla, Prakash, Sankar, JHEP 1307, 131 (2013)
If θ23 < 41° or θ23 > 50°, we can resolve the octant issue at 2σ irrespective of δCP
If θ23 < 39° or θ23 > 52°, we can resolve the octant issue at 3σ irrespective of δCP Important message: T2K must run in anti-neutrino mode in future
S. K. Agarwalla, 82nd Annual Meeting of IASc, IISER Bhopal, 4th November, 2016 17/24 Future Facilities for Long Baseline Neutrino Experiments
Deep Under Neutrino Experiment (DUNE): FNAL to Homestake : 1300 km (1st Osc. Max = 2.52 GeV)
Beam: 120 GeV, 0.7 MW, 6 × 1020 POT/yr, 5 yrs ν + 5 yrs anti-ν, Detector: 35 kton LArTPC
DUNE is capable enough to settle the remaining fundamental unknowns in neutrino oscillation at high confidence level, needed to claim the discovery
Projected data from T2K and NOvA will play a crucial role in the first phase of DUNE
S. K. Agarwalla, 82nd Annual Meeting of IASc, IISER Bhopal, 4th November, 2016 18/24 India-Based Neutrino Observatory An Indian Initiative to build a world-class underground laboratory to pursue non-accelerator based high energy and nuclear physics research
The prime focus of this experiment is to explore the Earth's matter effect by observing the energy and zenith angle dependence of the atmospheric neutrinos and antineutrinos (separately) in the multi-GeV range
We are actively involved in the physics and detector simulation studies related to the Iron Calorimeter (ICAL) detector at the INO facility
INO graduate students are being trained at IOP
S. K. Agarwalla, 82nd Annual Meeting of IASc, IISER Bhopal, 4th November, 2016 19/24 Coordinates of INO
Bodi West Hills Pottipuram Village 9°58 N and 77°16 E
Located 115 km west of the Madurai city in the Theni district of Tamil Nadu
Come up with an underground lab & surface facilities & build massive 50 kton magnetized Iron Calorimeter (ICAL) detector to study atmospheric neutrinos
S. K. Agarwalla, 82nd Annual Meeting of IASc, IISER Bhopal, 4th November, 2016 20/24 Studies Related to ICAL Detector at INO
S. K. Agarwalla, 82nd Annual Meeting of IASc, IISER Bhopal, 4th November, 2016 21/24 Event Display Inside the ICAL Detector
Using GEANT4 simulation
Devi, Thakore, Agarwalla, Dighe, arXiv:1406.3689 [hep-ph]
S. K. Agarwalla, 82nd Annual Meeting of IASc, IISER Bhopal, 4th November, 2016 22/24 Identifying Neutrino Mass Hierarchy with ICAL
25 5 NH (true), 50 kt (E , cos , E/ ) 20 had (E, cos ) 15 4 40% improvement adding hadron energy information 2 ICAL-MH
10
3 5 2 0 5 101520 Run-time (years)
Median Sensitivity Devi, Thakore, Agarwalla, Dighe, arXiv:1406.3689 [hep-ph] (INO Collaboration) 50 kt ICAL can rule out the wrong hierarchy with Δχ2 ≈ 9.5 in 10 years
S. K. Agarwalla, 82nd Annual Meeting of IASc, IISER Bhopal, 4th November, 2016 23/24 A Personal View of Sheldon Lee Glashow
Is observable CP violation confined to hadrons?
I would assign very high priority to experiments that could demonstrate the existence of CP violating effects in the neutrino sector
The other important mass-related issue is the binary choice between two orderings of neutrino masses
The accuracy with which oscillation parameters are already known surely suffices for the design of an experiment that can accomplish this goal
Particle Physics in the United States A Personal View Sheldon Lee Glashow arXiv:1305.5482v1 [hep-ph]
!! Let us work together and resolve these fundamental issues !!
S. K. Agarwalla, 82nd Annual Meeting of IASc, IISER Bhopal, 4th November, 2016 24/24 More Discussions
BACKUP SLIDES The Two Fundamental Questions
Why are neutrinos so light? The origin of Neutrino Mass!
Why are lepton mixings so different from quark mixings?
The Flavor Puzzle! PMNS vs. CKM
Recent discovery of θ13 signifies an important breakthrough in establishing the standard three flavor oscillation picture of neutrinos
It has opened up exciting possibilities for current & future oscillation experiments
At present, we have:
Satisfactory progress in last 15 years but still very far from the dream precision: Neutrino Mass Hierarchy Discrimination
Distribution of Δχ2 [χ2 (IH) - χ2 (NH)] for mass hierarchy discrimination considering μ- events
2 (GeV-1 sr-1) 2 (GeV-1 sr-1) - 0.6 - 0.6 10 10 0.5 0.5 8 8 0.4 0.4
6 6 0.3 0.3 (GeV) (GeV) 4 4 E 0.2 E 0.2
2 0.1 2 0.1
0-1 -0.8 -0.6 -0.4 -0.2 0 0-1 -0.8 -0.6 -0.4 -0.2 0 cos cos Hadron energy information not used Hadron energy information used Further subdivide the events into four hadron energy bins
Hadron energy carries crucial information
Correlation between hadron energy and muon momentum is very important Precision Measurement of Atmospheric Parameters 4 MINOS (Beam + Atmospheric), NH 90% C.L. 3.8 T2K (6.57 1020 P.O.T.), NH
) SK (I - IV) 2 3.6 ICAL 500 kt-yr projected reach 3.4 ICAL true point (eV
-3 3.2 3
| / 10 2.8 2 32 2.6 m
| 2.4 2.2 2 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 2 sin 23
Devi, Thakore, Agarwalla, Dighe, arXiv:1406.3689 [hep-ph] (INO Collaboration)
ICALs expected precision on atmospheric mass splitting is better than Super-K Our Approach
Use the expressions for the vacuum oscillation probabilities as it is, but make the following replacements:
2 θ12 →θ12′ , θ13 →θ13′ , δm jk → λ j − λk where
2 2 2 2 2 (δm21 / c13 )sin2θ12 (δm31 −δm21s12 )sin2θ13 tan2θ12′ 2 2 ,tan2θ13′ 2 2 2 , (δm21 / c13 )cos2θ12 − a (δm31 −δm21s12 )cos2θ13 − a
(δm2 ac2 ) (δm2 − ac2 )2 4ac2 s2 δm2 λ λ′ λ′ 21 13 21 13 13 12 21 1 − 2 λ2 λ′′ ∓ ⎡ 2 2 ⎤ ⎡ 2 2 ⎤2 2 2 2 2 ⎣λ′ (δm31 as13 )⎦ ⎣λ′ − (δm31 as13 )⎦ 4a s12′ c13s13 λ3 λ′′ λ′′ 2
upper (lower) sign is for the normal (inverted) hierarchy
Agarwalla, Kao, Takeuchi, JHEP 1404, 047 (2014) a-dependence of effective mass-squared differences
2 2 Λ'' Λ'' 1 1
2 31 0 2 31 0
Λ'' Λ'' Δ Δ 1 1 Λ Λ 2 2 log log
Λ' Λ' 3 3
4 4 4 3 2 1 0 1 2 4 3 2 1 0 1 2 Β Β
Normal Hierarchy Inverted Hierarchy
Agarwalla, Kao, Takeuchi, JHEP 1404, 047 (2014) Detector Characteristics
Should have large target mass (50 – 100 kt) Good tracking and Energy resolution (tracking calorimeter) Good directionality for up/down discrimination (nano-second time resolution) Charge identification (need to have uniform, homogeneous magnetic field) Ease of construction & Modularity Complementary to the other existing and proposed detectors
Magnetized iron (target mass): ICAL RPC (active detector element) Three Flavor Effects in νμ νe oscillation probability
0.03 0.3
θ13 Driven 0.09
CP odd Resolves octant 0.009
CP even
Solar Term 0.0009
Cervera etal., hep-ph/0002108 Freund etal., hep-ph/0105071 changeschanges signsign withwith sgn(sgn( ) cchangeshanges ssignign wwithith popolaritylarity See also, Agarwalla etal., arXiv:1302.6773 [hep-ph] keykey to resolve hierarchhierarchy!y! causes fake CP asymmetry!
This channel suffers from: (Hierarchy – δCP) & (Octant – δCP) degeneracy! How can we break them? What large θ13 buys for us?
Newly discovered large value of θ13 enhanced the chances of present generation experiments to provide a strong hint of mass hierarchy discovery around 2σ
Combining data from T2K and NOνA will be very useful to kill the clones
To have a > 5σ direct determination of MH for all values of δCP, we need next generation LBL expts (> 1000 km) enriched with Earth Matter effects
Thanks to large θ13, we do not need β-beam or ν-Factory for MH discovery
A reasonably upgraded Superbeam with a power of around 1 MW coupled with a small 10 to 20 kt LArTPC detector can do it provided the baseline is > 1000 km
Large θ13 allowed to adopt an incremental approach for next generation expts
The determination of MH can be considered as a first step towards the Leptonic
CP violation discovery which is quite tough even for large value of θ13 Latest Results on θ13 : What happened to Mass models?
present 3σ range
only 7 models survived
Albright and Chen, arXiv:hep-ph/0608137
Survey of 63 ν mass models in June 2006 by Carl H. Albright and Mu-Chun Chen!
Future high precision measurements of mixing angles, new information on neutrino mass ordering and CP phase will severely constrain these presently allowed models! Implications of Recent Measurement of θ13 Simplest models that are ruled out!
Bimaximal mixing: [Vissani (97), Barger, Pakvasa, Weiler, Whisnant (98)] predicted in flavor symmetry It predicts: θ12 = 45°, θ23 = 45°, and θ13 = 0° models with symmetry groups like A4, S4, A5 Tri-bimaximal mixing: [Vissani (97), Harrison, Perkins, Scot (02)]
Golden ratio: [Datta, Ling, Ramond (03), Kajiyama, Raidal, Strumia (07)]
It predicts: θ12 = 31.7°, θ23 = 45°, and θ13 = 0° Simplest models that are still alive!
Anarchy (ν mass matrix completely random): [Hal, Murayama, Weiner (99), de Gouvea, Murayama (03, 12)]
It predicts: large θ13, okay with observed value of θ13
Quark-Lepton Complementarity: [Minakata, Smirnov (94), Raidal (04)]
Based on observation: θ12 (PMNS) + θ12 (CKM) = 45°
It predicts: sinθ13 ≈ sinθC /√2 ≈ 0.16 (close to the observed value, other relations needs to be tested!) See-Saw & Neutrino Mass Neutrinos are everywhere Approved projects under INO • Come up with an underground lab & surface facilities near Pottipuram village in Theni district of Tamil Nadu
• Build massive 50 kt magnetized Iron calorimeter (ICAL) detector to study properties of neutrinos
• Construction of INO centre at Madurai: Inter-Institutional Centre for High Energy Physics (IICHEP)
• Human Resource Development (INO Graduate Training Program)
Module 3 • Completely in-house Detector R&D with substantial INO-Industry interface Module 2 Module 1 • Time Frame for 1st module: 2019 Electronics Racks Tunnel End Side Specifications of the ICAL Detector
Rapid progress in all fronts 2011-2016: A productive phase for INO! Several milestones achieved Backup Slides (Neutrino Mass)
arXiv:1203.5250v1 Courtesy to Liang Yang Backup Slides (Neutrinoless double beta decay)
Courtesy to Liang Yang Backup Slides
Courtesy to Concha Gonzalez-Garcia Backup Slides
Courtesy to Concha Gonzalez-Garcia