1. Results from T2K and Prospects for Hyper Kamiokande
Dave Wark
Prague Colloquium
Nov. 2nd, 2017
Warning: I have stolen slides mercilessly from my
colleagues, including many from Mark Hartz’s
talk at KEK on August 4th of this year.

2. Some Ancient History…
Question in the late 50’s: Are the neutrinos in these reactions the same thing?:
n → p + e + ν p → m + ν m → e + ν + ν
If so, why no m → e + g via diagrams like?: m n e g
IVB

3. Today this would be interpreted as a neutrino oscillation experiment, and in a different world that could have confused things greatly!
m event
e event

4. #

6. CCQE rel. s max!

10. e p0 m Background from NC interactions nm disappearance signal ne
In this energy range, Super Kamiokande well understood,
Excellent for separating
electrons, m, p0

12. We are running again. Power ramping up, currently ~440 kW
We are running again. Power ramping up, currently ~440 kW. Running in RHC mode.

31. Many fake data studies have been done to test sensitivity and robustness of analysis to different assumptions about neutrino interaction models. Still preliminary, but current results indicate 23 mixing parameters are more sensitive than d.
Watch this space. Results are informing designs of upgrades to the ND280 ND

36. T2K is moving towards T2K II, with 20 x 1021 p.o.t.
Requires better control
of systematics!

39. Find DSNR neutrinos. . .
Meanwhile, in Super-K…
Slash PDK background. . .
Tell n from anti-n. . .

40. Uprades to the detector will be done next summer.
Gd loading will be done depending on T2K schedule.

42. To get project moving as quickly as possible, currently only discussing one tank in Japan. Second tank to be added later, but maybe not in Japan?

50. Simulations show significant improvements in
Systematics!

54. Included in shortlist of future large projects by the Science Council of Japan
Upgrade to the beam to reach 1.3 MW already approved (funding not started yet)
Hyper Kamiokande was identified as the highest priority project in the new MEXT Roadmap published this summer. This is “approval” in the Japanese system.
Next step (and last before construction start) is the Ministry of Finance – some money may start next year, with full budget to follow.

55. Conclusions (I)
T2K has surpassed all its construction goals with only about 1/3 of its design protons on target, largely as a result of a very favourable value of sin2q13.
T2K sees a high rate of electron neutrino appearance which favours CP violation at ~2 sigma.
T2K sees a low rate of muon neutrino survival which favours maximal disappearance.
The combination favours NH, but with very limited significance.
All these conclusions are statistically weak, so more data is definitely needed.
The nuclear physics of neutrino interactions has proven more complex and more important than was appreciated when the experiment was originally built, so we need more theoretical work and more and better near detector data (and probably ancillary experiments such as a high-pressure TPC).

56. Conclusions (II)
Upgrades are planned to the near detectors to address the experimental end of this and the first steps are underway with WAGASCI/BabyMIND.
The community as a whole is attacking the uncertainties in neutrino interactions, which will severally limit future experiments if not better understood.
T2K II will provide a rich data set to further explore the physics of oscillations and give more sensitivity to MH and CP>
Definitive measurements will require bigger detectors!
Hyper Kamiokande is moving towards construction start with first data in the latter half of the 2020’s.
All these activities are short of manpower!
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