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TimestampLecturerWhich Lecture ?Your Name: Last, FirstYour QuestionReply
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8/19/2019 9:25:44Jean-Baptiste de VivieHiggs & FlavorI have a question about the lower right figure on page 11. Why does the fit give the absolute value of K_AVV when the formula looks to be sensitive to its sign. Answered live
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8/19/2019 10:26:47Jean-Baptiste de VivieHiggs & FlavorOn slide 11 you show Run I CMS result of a m(4l) scan. Why is the right tail of the qqbar->ZZ contribution so large?Answered live
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8/19/2019 12:13:11Jim MillerLeptonic Flavor Violation ExperimentsI have a question on page 19. Belle has more integrated luminosity compared with BaBar, and most of the limits from Belle are more stringent. But they are comparable for lll. Why is that? Is there a difference in detector properties that explains this? Answered live
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8/19/2019 14:09:17Sacha Davidson
Theory of Lepton Flavor Violation
Several lecturers have mentioned dimension 5, 6 etc operators. How do we count these dimensions? And why?Answered live
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8/19/2019 14:46:04Jim Miller
Leptonic Flavor Violation Experiments
How different are Mu2e/COMET experiments from the previous one to improve the detection limit by a factor 10^4 (slide 21)?Answered live
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8/20/2019 13:21:36Mark Messier
Neutrino Masses & Mixing Angles
There are two lines in the standard solar model energy spectrum labeled 7Be. Is there another decay mode of 7Be to neutrino that is not shown on the previous page? And how does this line become very broad in the Borexino spectrum?Yes there are two lines. Most of the 7Be produce 7Li in the ground state which yields the higher energy neutrinos; the second line is from transitions to other states. These neutrinos are observed in Borexino via their elastic scattering off electrons; the distribution of electron energies results from this scattering is uniform up to the energy of the incident neutrino. So the line source becomes a uniform "rectangle" between Erecoil = 0 and Erecoil = Enu. The cutoff on the high end is smeared by energy resolution.
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8/21/2019 7:02:44Alex Friedland
Theory of Neutrino Cross Sections
Why do we use FLUKA for simulation here? Don't most particle physics experiments use Geant4? There are a few reasons for using FLUKA for our simulations. Let me mention the two main ones. First, one of the physics questions we wanted to explore was the impact of detecting the de-excitation gammas on the energy resolution of a DUNE-like detector. FLUKA has a strong reputation for modeling nuclear de-excitations. This has been recently demonstrated by the ArgoNEUT experiment, which reported observations of de-excitation gammas in liquid argon, in good agreement with FLUKA predictions [arXiv:1810.06502, PRD 2019]. By the way, here's an explicit example of a particle physics experiment using FLUKA. Second, we were interested in comparing LArSoft results, which do rely on GEANT4, to ours: code comparison is always a good practice in our field.
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8/21/2019 11:09:50Kevin McFarland
Measurements of Neutrino Cross Sections
Page 46 lower right is the invariant mass distribution of p-pi0, and the peak is seen to be shifted relative to Delta(1232). What does it look like for charged pions? Isn't it easier to measure charged particles? Answered live
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8/21/2019 11:12:05Kevin McFarland
Measurements of Neutrino Cross Sections
Can electron scattering (instead of neutrino charged current) contribute to the understanding of pion production mechanisms? Answered live
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8/21/2019 12:47:27Kate ScholbergSupernova NeutrinosIs LIGO sensitive to supernovae burst? What about the next generation gravitational wave detectors (LISA)?Answered live
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8/23/2019 8:57:42Kate ScholbergSupernova NeutrinosHow is the time delay for neutrino measured? What is the time reference? gravitational waves measured by LIGO?The individual neutrino interaction times are in most cases measured to quite high precision by the neutrino detectors themselves. Scintillator and Cherenkov detectors give fast signals, and events can typically be timed at the ~10 ns level or better. Liquid argon is a bit slower— in the TPC, timing precision is on the scale of the electron drift time to the anode plane, which is ~3 milliseconds in a module. However liquid argon TPCs can have photosensors for scintillation light too, which gives fast timing, limited by Rayleigh scattering of optical photons in the argon (but still ~tens of ns for individual events). The absolute times of the interactions are known using a GPS time stamp. Detectors are typically equipped with a cable (optical fiber) to a GPS receiver which provides an absolute UTC time stamp to the digitization electronics. This can absolute-time-stamp events to typically tens of ns or better. (We know this works well because long-baseline neutrino detectors are able to time events from a beam at this level.) The overall timing of a burst is of course limited by the statistics of the burst— you are sampling events randomly over some tens of seconds according to the event rate, which is flux convolved with cross section and detector efficiency. Gravitational wave signals are also time-stamped to similar precision, and there is much interesting physics to be done by comparing the relative delay and time structures of the neutrino and gravitational wave pulses (e.g., neutrino absolute mass, which will give a small energy-dependent delay— again this will be statistically limited, and will probably not be competitive to terrestrial experiments--as well as core collapse/explosion physics). Of course we do not know the absolute core collapse time— but we can compare the measured structure in both neutrinos and gravitational waves to models.
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