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!)