[Isac-journal-club] paper for Sept 28 journal club

Charlie Payne cgpayne at triumf.ca
Wed Sep 21 17:03:54 PDT 2016


Yo peeps,



A week from now, we will congregate to go over the paper: “Search for
Majorana neutrinos near the inverted mass hierarchy region with KamLAND-Zen”


http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.117.082503



*Some questions to consider are*


1) How can a detector measure a process with a half-life supposedly many
orders of magnitude longer than the age of the universe?


2) And why should we care about the neutrinoless double-beta decay (0vBB)
half-life anyways?


3) True or False - a positive measurement of 0vBB would necessarily confirm
that: a) the neutrino is its own anti-particle, b) the neutrino is
Majorana, c) lepton number is violated via physics beyond the standard
model?


4) What’s the significance of KamLAND-Zen probing into the edge of the
“quasidegenerate” mass region?


5) How do they distinguish potential 0vBB events from other events, such
as: 2vBB, contamination/background, other exotic processes, etc?



*And some more specific discussion questions will be*


6) The authors speculate that “much of [the Ag-110m contaminant] settled to
the bottom of the IB” (end of page 3), how could they test this hypothesis?
Is splitting the phase 2 data into two periods, as defined by the Ag-110m
lifetime, helpful to this analysis in that respect?


7) Overall, with these results and the planned upgrades (mentioned in the
conclusions), is it fair to conclude that KamLAND-Zen will be a competitive
detector with a demonstrated ability to measure the hypothetical 0vBB?


8) And if so, how does the conclusion of zero events measured (and hence
only having *constraints* on the 0vBB half-life) fair for the outlook of
future 0vBB work, in particular with respect to the quasidegenerate mass
region and beyond.



*Also some jargon to help with your reading is* #PRLengthLimits


* Ag-110m = a nuclear isomer (a metastable nuclear state in excitation -
hence the “m”) of silver


* quasidegenerate neutrino mass region = from neutrino oscillation
experiments we can tell there must be a non-zero relative mass scale of the
three neutrino mass eigenstates, and these fit into two hierarchies (the
normal (NH) and inverted (IH)) which overlap at certain points referred to
as quasidegenerate, where said 0vBB data would find NH and IH
indistinguishable, see FIG 3 for a nice diagram of the current situation


* nuclear matrix elements = theoretical calculations of the underlying
nuclear physics of a process, for example using ab-initio many-body theory;
which can predict half-lifes, given the masses of the constituents of said
process are known, or visa versa (wink wink, nudge nudge, say no more)


* spallation = the process of being broken apart into pieces upon impact,
for example nuclear matter being spalled by high energy muons bouncing
around



See you then (another reminder will be sent)!



Charlie Payne

--------------------------------

TRIUMF Office: MOB 115-4

TRIUMF Phone:  604-222-1047x6166

--------------------------------

UBC Office:    Hebb 1F-2

UBC ID:        85886159

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Candidate:     M.Sc. Physics, University of British Columbia

Awarded:       B.Sc. Mathematical Physics, University of Waterloo
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