belle “engineering run” on the Υ (3s)
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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
DAMA NaI 3Region
CDMS 04
CDMS 05
90% CL upper limits assuming standard halo A2 scaling
Upper Limits from Direct MeasurementsPredictions: Ellis & Olive, Baltz
& Gondolo, Mandic & all
Direct measurements have no sensitivity for ~GeV mass regionLHC will reach ~TeV mass regionWho will search ~GeV mass region ?
N’
N
b
b
Possibility of Dark Matter Search in B-factory
PRD 72, 103508 (2005)
Br( Υ(1S) ) ~ 0.0041 (m<4.73GeV/c2)
Υ(3S)ISR
Υ(3S) +-Υ(1S), Υ(1S) invisibleHowever …Two-photon backgrounds are quite high …Hard to reach Br ~ O(0.001)
Idea to improve S/N ratio
(e+e- Υ(3S)ISR ) ~ 0.02 nb
(e+e- Υ(3S)) ~ 3.3 nb
S/N ratio x150
Energy scan in CLEO
Y(3S) run w/o TRG modification
Expected Sensitivity on Y(3S) run
trigger conditions were too tight for Υ(3S)nothinglooser triggers were needed for the required sensitivity
*) Syst. error is not considered
Y(4S) run460 /fb
Theory prediction
90 %C.L
Y(3S) run x 4 trigger efficiency
We took engineering data on the Υ(3S) to check: sensitivity with different trigger logic KEKB performance at lower Ecm sensitivity for other physics topics
Belle took data for 4.5 days(end of Feb, 2006)
Energy scan ~ 4hoursWe set E(4S)-223.6 MeV~ 3 /fb on Υ(3S) resonance ~0.25 /fb on; 30MeV below 3S
CLEO~3.3nb----
Trigger logic was optimized for DM channel
Control sample dataΥ(3S) Υ(1S)
Υ(1S)
Eff. depends on opening angle
opening angle (degree) 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
x
y
Trigger RateT
rig
ger
Rat
e (H
z)
Trigger rate was rather higher than usual condition (~460Hz)
w/o Event Builder
Upgrade
w/Event BuilderUpgrade
Last BGM slide by Ito-san
DAQB
elle
Dea
d T
ime
(%)
Trigger Rate (Hz)
Dead time was consistent with expectationWe confirm great advantage of event builder upgrade (2005 summer)However, there were frequent DAQ errors remaining subject …
Υ(3S)Υ(1S); Υ(1S)with 137 pb-1 (~4% of total)
197 evts
applications
Summary• Υ(1S)invisible is sensitive for light dark-matter
– Υ(3S) 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!)
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