[time-nuts] Neutrino Velocity

[Javier Serrano]

On Fri, Jun 8, 2012 at 1:51 AM, Marvin Marshak <marshak at umn.edu> wrote:
> Good morning from Japan,
>
> The Neutrino 2012 Conference is being held in Kyoto, Japan, this week. This morning's session is scheduled for 3 talks on neutrino velocity--one from the OPERA Experiment that initially reported the anomalous effect, one discussing other experiments at the Italian Gran Sasso Lab and a third talk from the MINOS Experiment (Fermilab to Soudan MN). The session will begin at 0915 Japan time.
>

Hi Marvin,

Someone told me the LNGS experiments reported just preliminary results
(some more fine-tuning of calibrations needed) with central values of
Dt ranging from 2 to 6 ns with statistical errors around 1 ns and
systematics ranging from 3 to 6 ns (positive Dt means nu slower than
light). Apparently MINOS  presented only a reanalysis of the data
accumulated from 2005 with Dt around -11 ns and a systematic error of
the order of 15 ns. The analysis of more recent data collected after
installation of the new timing system will probably be available
after the Summer. Is this correct?

BTW, we installed White Rabbit links redundantly to the existing LNGS
and CERN timing systems for the two weeks of special beam
(100ns-spaced 2ns-wide bunches). It was quite a rush so it is not
fully documented. All the data we gathered can be seen at
https://project-lngstt.web.cern.ch/project-lngstt/ (although it is
quite useless without explanations of what the data actually mean).
The important bit is that WR agreed with the legacy systems at least
at CERN, OPERA and Icarus. Borexino and LVD have not checked yet
against WR, but should do so in the near future.

So in terms of redundancy we have:
- Four different experiments in LNGS basically agreeing on the value
of the neutrino speed, compatible with c.
- Two different timing technologies (for internal lab distribution)
agreeing at CERN and two different timing technologies agreeing in
LNGS.
- Two different GPS time transfer systems using two different software
analysis tools agreeing with each other.

The only bit of redundancy I see missing is in certain parts of CERN,
like the length of the cable from the Beam Current Transformer to the
digitizer, which is common mode to everybody. The MINOS data, when it
becomes available should provide more reassurance on those last bits.

Cheers,

Javier