Transcript 3S Run Summary - Istituto Nazionale di Fisica Nucleare

Belle “Engineering Run” on
the Υ(3S)
S. L. Olsen
The Cosmic Mystery-Pie
o% antimatter
WIMPs (Weakly-Interacting-Massive-Particles) are good dark matter candidates
Upper Limits from Direct Measurements
90% CL upper limits assuming standard halo A2 scaling
Predictions: Ellis & Olive, Baltz
& Gondolo, Mandic & all
DAMA NaI
3s Region
c
c
N’
N
c
c
b
Direct measurements have no sensitivity for ~GeV mass region
LHC will reach ~TeV mass region
Who will search ~GeV mass region ?
b
Possibility of Dark Matter Search in B-factory
PRD 72, 103508 (2005)
Br( Υ(1S)cc ) ~ 0.0041 (mc<4.73GeV/c2)
Υ(3S)gISR
Υ(3S)  p+p-Υ(1S), Υ(1S) invisible
However …
Two-photon backgrounds are quite high …
Hard to reach Br ~ O(0.001)
Idea to improve S/N ratio
s(e+e-  Υ(3S)gISR ) ~ 0.02 nb
s(e+e-  Υ(3S)) ~ 3.3 nb
S/N ratio x150
Energy scan in CLEO
Expected Sensitivity on Y(3S) run
Y(3S)
Y(3S) run
run
w/o
TRG modification
x 4 trigger
efficiency
Y(4S) run
460 /fb
90 %C.L
Theory prediction
*) Syst. error is
not considered
We took engineering data on the Υ(3S) to check:
 sensitivity with different trigger logic
trigger conditions
were too tightatfor
Υ(3S)p
 KEKB performance
lower
Ecm +p- nothing
looser triggers
were needed
forphysics
the required
 sensitivity
for other
topicssensitivity
Belle took data for 4.5 days
(end of Feb, 2006)
~3.3nb----
CLEO
Energy scan ~ 4hours
We set E(4S)-223.6 MeV
~ 3 /fb on Υ(3S) resonance
~0.25 /fb on; 30MeV below 3S
Trigger logic was optimized for DM channel
Control sample data
Υ(3S)  Υ(1S)p+pΥ(1S)  m+mEff. depends on opening angle
opening angle (degree)
p+
py
x
4 times efficiency gain is expected
- loose opening angle cut
135  45 degree
- loose pt cut
pt>350 MeV for both tracks
 for one (or both) track
Trigger Rate
Trigger Rate (Hz)
Trigger rate was rather higher than usual condition (~460Hz)
DAQ
Belle Dead Time (%)
Dead time was consistent with expectation
We confirm great advantage of
event builder upgrade (2005 summer)
However, there were frequent DAQ errors
 remaining subject …
Last BGM slide by Ito-san
w/o
Event Builder
Upgrade
w/
Event Builde
Upgrade
Trigger Rate (Hz)
Υ(3S)p+p-Υ(1S); Υ(1S)m+mwith 137 pb-1 (~4% of total)
197 evts
applications
Summary
• Υ(1S)invisible is sensitive for light dark-matter
–Υ(3S)  p+p-Υ(1S)invisible
– direct searches have no sensitivity ~GeV mass region
• We tookΥ(3S) engineering runs for 4.5 days
– ~3 /fb (~10M evts) on Υ(3S); ~0.25 /fb off-resonance)
– world’s largest Υ(3S) data sample
• Offline analysis of Υ(1S) invisible is in progress
• Only a few other analyses are currently planned
– interested parties encouraged to apply
• Also have ~20 /fb data sample @ theΥ(5S)
– also the world’s largest Υ(5S) sample (by far!)