Mauro Mezzetto, Istituto Nazionale Fisica Nucleare, Padova

CP violation in the sector

• Introduction • Present Status • What matters • Medium term: T2K-II • Next generation: Dune and Hyper-Kamiokande Leptonic CP violation in the Standard Model, δCP

Out of the 26 free parameters of the Standard Model, 4 are not yet measured: mνe, mνµ, mντ, δCP

• δCP can be detected by measuring differences between oscillation rates of and antineutrinos

CP violation in neutrino oscillations could be an important new ingredient to understand the matter-antimatter asymmetry in the Universe “The observation of L violation and of CPV in the sector would be a strong indication (even if not a proof) of leptogenesis as the origin of the baryon asymmetry.”

Furthermore

• Precise measurements of oscillation rates have the potential to show new physics (unitarity of the mixing matrix, NSI in neutrino oscillations, deviations from expected values of matter effects)

• The large detectors necessary for MH or CP searches have great potential for non-accelerator physics: decay, indirect DM searches, relic SN neutrinos etc. M. Mezzetto, INFN Padova, IPA 2016, Orsay 2

Other possible sources of CP violation in neutrinos

CP Violation in Majorana Neutrinos If neutrinos are Majorana particles there will be two additional CP phases in neutrino physics. We are very far from the experimental possibility of measuring Majorana CP phases.

CP Violation in Sterile Neutrinos If light sterline neutrinos exist and if the model is 3+2 (or wider) there will exist additional CP phases for sterile neutrinos

In the following I will focus on Dirac CP phase only.

M. Mezzetto, INFN Padova, IPA 2016, Orsay 3 M. Mezzetto, INFN Padova, IPA 2016, Orsay 4 … require knowledge of all the other parameters To extract dCP it’s necessary to precisely know all the other oscillation parameters It’s now possible thanks to the reamrkable progress in measuring the parameters (shown the progress between 1998-2014)

Atmospherics (2-3) Solars (1-2)

θ13

M. Mezzetto, INFN Padova, IPA 2016, Orsay 5 We are talking of measuring δCP ...

... because of a very favorable combination of parameters

M. Mezzetto, INFN Padova, IPA 2016, Orsay 6 At present … 19% of full statistics ν:ν=1:1 15% of full statistics ν:ν=1:0

M. Mezzetto, INFN Padova, IPA 2016, Orsay 7 CP conservation excluded at more than 2 σ !

T2K alone excludes CP conservation at 90%CL

• By combining with NOνA and adding the new results of SK • And fitting all the world data

A. Marrone et al. showed a preliminary global fit where CP conservation is excluded at more than δ/π 2 σ

M. Mezzetto, INFN Padova, IPA 2016, Orsay 8 Next on CP

• HK: 10 years, staged, 1.3 MW NH HK • Dune: 7 years full conf., 1.2 MW • T2K-II: 3 times T2K stats and several improvements in beam configuration and data analysis • T2K+Nova: full stats, basically already achieved T2K-II • What about Nova-II?

I will elaborate more in the restM. ofMezzetto, the talk INFN Padova, IPA 2016, Orsay 9 What matters: 1) Exposure

Baseline, on or off-axis, 2° osc. Maximum are 2nd order effects at most

M. Mezzetto, INFN Padova, IPA 2016, Orsay 10 What matters: 2) Systematic Errors

Since a long time they are known to be the real bottleneck (or in positive the only convincing way of enhancing the experimental sensitivity) Huber, MM, Schwetz, JHEP 0803 (2008) 021 Varying luminosity at fixed θ13 . Varying θ13 at fixed luminosity

M. Mezzetto, INFN Padova, IPA 2016, Orsay 11 Where we are with systematic errors?

A factor 2 improvement in anti-ν in one year

M. Mezzetto, INFN Padova, IPA 2016, Orsay 12 The impressive efforts behind systematic errors

List of the plenary talks scheduled at Neutrino 2016 about neutrino cross-sections

Theoretical challenges in neutrino scattering studies Juan M Nieves, IFIC (CSIC & UV), Spain Review of progress in measurements of neutrino-nucleus scattering Kendall Mahn, Michigan State University, USA Recent results from MINERvA Laura Fields, , USA New Results From MicroBooNE Matthew Toups, Femilab, USA Future experimental programme for neutrino cross sections Sara Bolognesi, CEA Saclay, France production experiments to constrain accelerator-based neutrino flux Laura Zambelli, Laboratoire d’Annecy-le-Vieux de Physique des Particules (LAPP), France

Not to say the enormous effort of the collaborations in understanding and managing all the other sourcesM. Mezzetto, of INFN systematics Padova, IPA 2016, Orsay 13 New concepts on neutrino beams

• In the long term it will be necessary to have neutrino beams with well known fluxes (no other way to push systematics at the 1% level) • Unfortunately so far major labs don’t support R&D in this direction • Nevertheless very interesting developments presented at the conference: – Future decay-at-rest neutrino sources and their physics opportunities Taritree Wongjirad, Massachusetts Institute of Technology (MIT), USA – Physics potential of novel neutrino beams from and decay Steve Boyd, University of Warwick, UK – Development of muon accelerators for neutrino experiments Durga Rajaram, Illinois Institute of Technology (IIT), USA – P2.040 High precision neutrino flux measurements with ENUBET Michele Pozzato, INFN - Sezione di Bologna, Italy ERC Consolidator by A. Longhin, INFN Padova

M. Mezzetto, INFN Padova, IPA 2016, Orsay 14 The impressive efforts behind systematic errors (cross sections)

As an example the summary of Minerνa presentation

Looks like theory runs behind experiments: powerful and innovative models exist but none is capable to explain all the available data in one step.

M. Mezzetto, INFN Padova, IPA 2016, Orsay 15 T2K-II (arXiv:1607.08004) Upgrade the beam at 1.3 MW (already approved), collect 20 1021 pot (3 times nominal intensity) upgrade beam line, improve analysis

M. Mezzetto, INFN Padova, IPA 2016, Orsay 16 Two players: Dune and Hyper-Kamiokande Neutrino Telescopes: the best long term investment ever

• Following the experience of SK, Kamland, SNO Borexino, IceCube etc… • … in the long term more physics results and better performances than expected • Physics reach of Dune, HK, Juno: MH, octant, precision on oscillation parameters, proton decay, solar neutrinos, SN neutrinos, relic SN neutrinos, indirect dark matter searches, often in a truly complementary way • … and so far they provided the shortest way to Stockholm

M. Mezzetto, INFN Padova, IPA 2016, Orsay 18 As an example: searches for DM annihilation in the Sun

M. Mezzetto, INFN Padova, IPA 2016, Orsay 19 Two complementary approaches

• HK: – short baseline →no matter effects: pure CP but reduced MH

– Off axis → reduced intrinsic νe contamination, reduced NC backgrounds

• DUNE: – Long baseline → sensitive to matter effects: excellent performances in MH – On axis: second oscillation maximum and sensitive to ντ appearance (tiny effects at 1300 km) – On axis: extended lever of arm for measurement of oscillation parameters

M. Mezzetto, INFN Padova, IPA 2016, Orsay 20 Hyper-Kamiokande arXiv:1109.3262, arXiv:1412.4673, PTEP 2015 (2015) 053C02 Submitted to Science Council of Japan by T. Kajita on March 31, 2016 ... with a different configuration with respect to published papers

Beam power M. Mezzetto, INFN Padova,0.75 IPA MW 2016, Orsay 1.3 MW 21 Hyper-Kamiokande

Assuming 2Tank HD staging (2nd tank from 7th year), 10 years total run

78% (62%) coverage at 3σ (5σ)

0 ~ 7 precision on δCP possible

MH sensitivity Combining beam and atmospherics Same staging assumptions

M. Mezzetto, INFN Padova, IPA 2016, Orsay 22 Hyper-Kamiokande

M. Mezzetto, INFN Padova, IPA 2016, Orsay 23 Hyper-Kamiokande

M. Mezzetto, INFN Padova, IPA 2016, Orsay 24 M. Mezzetto, INFN Padova, IPA 2016, Orsay 25 Dune

M. Mezzetto, INFN Padova, IPA 2016, Orsay 26 Dune

M. Mezzetto, INFN Padova, IPA 2016, Orsay 27 WA105 at CERN

Proto Dune Double Phase

Proto Dune Single Phase

M. Mezzetto, INFN Padova, IPA 2016, Orsay 28 CP violation: systematic errors HK estimation assuming identical close detector as T2K

Dune estimation extrapolating from Minos (no LAr close detector data so far)

M. Mezzetto, INFN Padova, IPA 2016, Orsay 29 Conclusions

• Leptonic CP violation is one of the major goals in high energy physics • At present experiments show intringuing suggestions about maximal violation • Conclusive results will require next generation experiments • … that will allow also precision measurements of oscillation parameters • … and a wide exciting set of astrophisical measurements like proton decay, indirect DM searches, (relic) SN neutrinos etc.

M. Mezzetto, INFN Padova, IPA 2016, Orsay 30