Subject: Nu2000 SNEWS meeting minutes
From: Kate Scholberg (schol@budoe.bu.edu)
Date: Sat Jun 24 2000 - 16:59:58 EDT
Minutes of SNEWS meeting at Neutrino 2000
=========================================
Thanks to all who came to the meeting, and special thanks to Clarence
(and helpers) for organizing the dinner, venue and other details.
These minutes were written without notes, so please email to point out errors
or omissions! Skip to the end for an overall summary of the meeting.
Experiment updates
------------------
-- Yoshiyuki Fukuda reported on the supernova burst search processing
upgrades for Super-K. He has implemented an "express-line" for data to be
processed by the supernova monitor. This plucks the data off for analysis
immediately after it is written by the acquisition, skipping the usual
"reformatting" step; this saves 5-10 minutes. A further improvement sends an
alarm if a burst is found after 100 events have been processed, so that
alarms can be sent out within a couple of minutes. This last upgrade will be
implemented by late June.
-- Reda Tafirout reported on SNO's monitor and alarm system (there were also
posters at the conference from Reda and Jaret). The event builder of the daq
sends data to a "dispatcher" as well as to offline processes. The dispatcher
parcels out the data to supernova monitor as well as online event displays
and other monitoring tools.
The dispatcher loses some events if the event rate goes above about 1
kHz; however there is no *burst trigger* inefficiency. (The data is also
analyzed offline for bursts and checked against the online monitor results.)
The supernova monitor has 3 levels: level 1 is the burst trigger, level 2
does additional background reduction, and level 3 is where human intervention
happens. He also showed the bursts which have been accumulated so far.
Bursts so far have been tagged as various kinds of background: electrical
breakdown, PMT HV breakdown, flashers, "neck" events, calibration-associated
etc. A few remaining background bursts are associated with cosmic ray muon
spallation events.
Standard SNO background-reduction cuts are applied to the events in the
bursts at the level 2 step. For the final burst cut
(allowing bursts to go to level 3), they require at least
20% of the events in the burst to survive the cuts (i.e. 20% "physics
content"). This results in a few or fewer surviving bursts per month. This
cut could be tuned to change the level 3 burst rate.
Time for human response was usually (85% of the time) less than
20 minutes. Distance sensitivity is about 20 kpc. The burst trigger is 50
events in 2 seconds with an Nhit threshold which varies according to the
current background conditions.
-- Piera Luisa Ghia gave the LVD update. Three towers have now been
installed, bringing the total mass up to 1 kton. Data-taking has been in
progress on two towers since 1994; the third will be in operation by
autumn of 2000. Uptime for stellar collapse is >=98% and the background rate
is 2 events per minute. The energy threshold is 7 MeV for the surface
counters and 4 MeV for the inner counters (which represent about 1/2 the
total mass). The energy threshold is lowered to 0.5 MeV for 1 ms after a
primary trigger. Shielding will be improved soon. The online monitoring
system gives an alarm within about 5 minutes via email.
-- I gave a status report on MACRO. Essentially, there's no change: MACRO's
wfds were removed in May, but the detector will continue to run until the end
of December, with both supernova monitors plus the "metamonitor"
(which combines alarms from the two independent SN systemts) online.
-- Steve Barwick and Christian Spiering reported on the status of AMANDA.
New strings were installed last austral summer to finish "Amanda II"; the new
PMTs (with new low radioactivity glass) have particularly low rates, which is
good for supernova sensitivity. New rate monitor hardware has been installed
with better time resolution than before. Work is being done on monitor
software. Overall sensitivity with the current configuration is about 10
kpc; time resolution will improve. The satellite coverage for communications
is still about 8 hours per day.
Kopke and Weinheimer from Mainz have done some triangulation studies to
evaluate how well it may be possible to get the neutrino burst time from
AMANDA data, given a general model of the pulse shape (assumed known), and
also given a fit to to the Super-K data: the answer is about 14 milliseconds
for the general known pulse shape, but worse by a factor of a few for the
Super-K fit. However results for ICECUBE are more promising. They will post
their memo (currently an internal report) to the working group.
-- Dick Boyd talked on the status of OMNIS. The current planned site is at
the CARUS lab (formerly WIPP) in Carlsbad, NM. The "OMNISita" detector, to
study background and develop the data acquisition, is under development,
consisting of 10 tons of old Palo Verde liquid scintillator and some PMTs and
electronics from Los Alamos (they still need 340 tons of lead to make up 2/3
of 1/8 of OMNIS).
-- John Beacom reported briefly on the new paper (Beacom, Boyd and
Mezzacappa) hep-ph/0006015: the idea is to use the sharp cutoff of neutrino
luminosity (nearly simultaneous for all flavors) from the formation of a
black hole t=0 for a time of flight neutrino mass measurement. They
estimate, for a Galactic center collapse, around 2 eV mass sensitivity for
electron antineutrinos with Super-K, and about 6 eV sensitivity for nu_mus
and nu_taus using a detector like OMNIS.
-- Barry Barish reported on LIGO, and proposed that LIGO join SNEWS, initially
as a passive participant. The gravitational wave core collapse signal is at
present poorly understood. However, LIGO's distance sensitivity exceeds
Galactic, so it may be possible to learn what SN signals look like over the
first years of operation-- LIGO will then be able to act as input to SNEWS.
Barry also proposed also exploring what physics can be done with combined
gravitational wave and neutrino signals (neutrino mass?)-- this is
a very interesting and mostly unexplored field.
SNEWS update
------------
I reported on the SNEWS status: the test server is still running on kaboom at
the Kamioka site. The coincidence requirement for an alert is still very
simple: a 2-fold coincidence within 10 seconds. Super-K, MACRO and LVD
participate. The coincidence currently results only in an email alert to a
small group of subgroup people.
Pietro Antonioli has set up a new server (gsboom) at LNGS; I've upgraded
the client code for multiple servers, but haven't yet installed it
for MACRO and Super-K.
The biggest jobs on the to-do list are:
-- implement the more complex coincidence requirements, such as the
"anti-coincidence" (i.e. require positive signal from all (or most)
experiments which should have been live), and events/kton consistency
requirements.
-- implement the secure socket connection and other security features.
This work will get done this summer.
Issues:
-------
There was very productive discussion on a number of issues requiring advisory
board decision. Many of these have been discussed and roughly agreed on
previously.
First, the non-controversial issues: the advisory board/working group/
subgroup structure is pretty much agreed on, as is the privacy agreement
(i.e. only subgroup members have access to real alarms). Downtime
coordination is also universally agreed on and we identified the experimental
reps who will be responsible for maintaining the information for their
experiment on the downtime web page:
SK: Fukuda
SNO: Van de Water
LVD: Fulgione
MACRO: Sioli
AMANDA: ??
I also brought up the issue of timing verification with a traveling
calibration system as something to think about for future discussion and
decision of the advisory board.
Automation/data exchange/privacy: these issues are inter-related. The basic
question was: what, specifically, do we need to do before we go to an
automated alert for astronomers? What do we need to convince ourselves of
and/or convince the astronomers of? Do we need upgraded coincidence
conditions or is OK to go automated with the current setup?
These questions are intimately related to the privacy issue: if, as we have
agreed, the alarms sent to kaboom are to be kept confidential, then it's not
clear how much and which information can be freely circulated for this
decision.
The answer, after some discussion, was basically:
The subgroup (whose members officially have access to all alarm information)
needs to get together, *sharing the alarm information within the subgroup
only*, to come up with a specific proposal for the advisory board.
A specific suggestion from Barry was that we should try a high-alarm rate
test, where each experiment lowers the alarm threshold to make sure that we
understand the nature of the background. We should also test that the
coincidence works. It was agreed to set up a test as part of the subgroup
study. Alarms which are known to be background (e.g. spallation, flashers)
should be tagged as such, but still used in the test. An interesting
suggestion from Art was to see if there are any coincidences of known
background events (e.g. spallations)... just in case there's any wacky
physics going on.
As for security, and convincing others that SNEWS is secure: Art suggested
that we look into getting a national lab expert(s) involved in some sort of
official verification that our system is secure, as well as maintenance of
security. We could also talk to GRB and SETI folks to see how they deal with
the problem. (We need to be a bit careful... announcing to the community
that our system is certified secure could be inviting hackers to the
challenge!)
Overall summary of the meeting:
------------------------------
News from experiments:
* Super-K is improving alarm speed
* SNO now has many months of experience characterizing alarms,
and can set the rate to 1/month
* LVD will be at 1 kton in the fall
* MACRO will continue running until the end of the year
* AMANDA has upgraded hardware and is working on supernova alarms w/10 kpc
sensitivity
* An OMNIS prototype is underway
* LIGO is on board as a passive participant
Downtime and privacy agreements were "blessed" by the advisory board.
The main question:
What do we need to do to convince ourselves that it's OK to go automated (and
how can we maintain the privacy requirements while doing so?)
was basically answered as:
The subgroup needs to get together to perform a high rate test, compile the
results (circulating information only within the subgroup), and come up with
a specific proposal for the advisory board based on this information. We
also need a security certification of some kind.
We will get to work over the summer...
This archive was generated by hypermail 2a24 : Sat Jun 24 2000 - 17:01:16 EDT