Status of Belle

Yutaka Ushiroda
Institute of Particle and Nuclear Studies, KEK
KEKB review, Mar.19, 2007

Outline News on the Belle detector operation
 Super-hot topics of physics
 Other topics of physics
 Summary & Conclusion

RadiSys EPC-6315

COPPER board
digitizer×4(daughter board)

onboard CPUIntel P3 800 MHz– 256 MB memory– Network boot– RedHat Linux 9–(online data reduction, etc…)
VME9U

Trigger module

100BaseT port×2

boot/control, data transfer

First step for thepipelined readout COPPER for the CDC

Performance: Deadtime
YamagataReduction
Deadtime (us)Typical data size

~29.5 usFASTBUS
1/10 deadtime
reduction is achieved~2.8 us

COPPER# of hits/TDC

COPPERIZATION EFFORT CONTINUES…
Will become COPPER in the coming summer
ACC, TRG, (part of) ECL
KLM, TOF, SVD, (rest of) ECL asap

Outline News on the Belle detector operation
 Super-hot topics of physics
 EPR Entanglement
 D0-D0b mixing
 Dark Matter Search Other topics of physics
 Summary & Conclusion

Δt measurement at Belleϒ(4S) B1electron(8GeV)_B0positron(3.5GeV)

B2µ+ J/ΨµKSνµD0fCPπ+K-B0πµ+Δz ~ 200µm "t # "z$% cFlavor tag

Entangled state and EPR paradox
Entangled state cannot be described as product states of parts

Quantum Mechanics  Local Realism
If one is B0, the other is B0b
at that moment

How can we know about the other B
before even light reaches?

Was pointed out by Einstein for the first time

Quantum Mechanics cannot be a complete theory!! (A.E)

Experimental Tests have been performedin photon pairs, kaon pairs QM confirmed
BB pair from Y(4S) decay is one of the few coherent systemmuch higher energy scale (~10GeV)

Time-dependent Flavor Asymmetry
QM:Time-dependent decay_ rate
_0B0): ∝ 1 − cos(ΔmΔt)Same Flavor (B0B0, B_Opposite Flavor (B0B0) : ∝ 1 + cos(ΔmΔt)

AQM(Δt) =OF−SF
OF+SF= cos(ΔmΔt)

Non-QM models: (example)• Local Realism: Pompili & Selleri (PS)_ _“elements of reality” = Flavor & mass (BH,BL, BH,BL)
random flavor flip within pair

• Spontaneous & immediate Decoherence (SD)Expectations

Analysis Method
B0 → D*lν + High Quality (lepton) tag

Subtract BackgroundObtain Unfolded (= true) A(Δt)→ Direct comparison with (any) theories

Results & fit with QM

χ2 = 5.2 (11 dof)
Good !
[ fit including WA Δm = (0.496 ± 0.014) ps-1 (excl. Belle/BaBar)]Result: SD & PSSDPS

χ2 = 174χ2 = 31.3

disfavored 13σ
over QM

disfavored 5.1σover QM

Decoherence fraction: λ = 0.029 ± 0.057

Conclusion
 QM is valid at E~10GeV
 SD, PS models are disfavoredD0-D0b mixing
Mixing observed in K0, B0d and B0s, not yetin D0 system
D0 mixing in the SM governed by boxdiagrams$ V V V V S (m , m )**ci ui cj uj

A=2i

2ji , j = d , s ,b! $ Vci*VuiVcjVuj* S (mi2 , m 2j )i, j =d ,s! (Vcd* VudVcdVud* + Vcd* VudVcsVus* + Vcs*VusVcdVud* + Vcs*VusVcsVus* )" S= (#Vcs*VusVcdVud* # Vcs*VusVcsVus* + Vcs*VusVcdVud* + Vcs*VusVcsVus* )" S=0Effective GIM suppression (md≈ms)
 mixing in D0 system is rare process difficult to measure sensitive to the new physics(Q CKM unitarity )What to measure?
Lifetime difference between D0K−π+ and D0K−K+(, π−π+)D0u++!
,K
d, ss
K!
ucu

No mixing  effective lifetimes are equal

A! + K " $ e "#t

AK + K ! # e !"t

CF, CSD0u
K!
sd, s + +u ! ,Kcu

mixing  effective lifetimes are different(A! K $ e!" (1+ yA#e))t"# 1+ y " + t+"

K+K!

DCS, CS
non-zero yCP %K !

1 + yK + K "1 + y K "! +"1#$
2$

is a manifestation of D0 mixing

K +K !

Experimental Technique
Flavor tag at production

D*+ # ! + D 0*"

D #! D"0

Proper-time measurement

pD 0
ldec
t=, !" =c!"
M D0
D mesons from charm pair productione + e ! " ccto reject D* from B decays

pDCMS> 2.5GeV / c*+signal events for fit
110K signal, purity = 98%

1.2M signal, purity = 99%

50K signal, purity = 92%

Dark Matter Search¼ of our universe is filled with Dark Matter
WIMPs are good candidates of DM(Weakly Interacting Massive Particle)

o% antimatter

Experimental Situation
No sensitivity in direct searches
in low mass (O(1GeV)) region

DAMA NaI
3σ Region

CSDM
C04

SDM05

χ
Nχ
N’

Energydeposition

Theory Prediction in low mass region
B ( Y(1S)χχ ) ~ 6x10−3 (mχ<4.73GeV/c2 ~ mb)
PRD 72, 103508 (2005) “Invisible quarkonium decays as a sensitive probe of dark matter”
Presented by B. McElrath in BNM-I in KEK Sep, 2006

Previous Upper Limit : < 23x10-3 (90% CL) by ARGUS (1986)

Why don’t we measure this at Belle?

Energy scan by CLEO, CUSB

Trigger with π+π−π+π− recoil mass peaks @1S

π+No signal left
in the detector

Y(1S)
Invisible

Y(?S)
Y(3S)

π−Y(3S) runs : 2.9 fb-1
(Feb, 2006 : 4days)

Control Sample
2.9 fb-1

4901.9±71
signals+π
Y(3S)
π−µ+

Υ(1S)
µ−tuned MCdata~ Signal peakBackground Expectation
Two-photon BG

recoil mass of π+π−Y(1S) µ+µ−, e+e− … (outside of acceptance)
ππµCf. 244 signal events if Br(Y(1S)invisible)=6x10-3µResult and Conclusion
Nsignal = 38 ± 39  0 consistent

B (Y(1S)invisible) < 2.5x10−3 (90%C.L.)
2.9 f b-1
at Y(3S)

Prediction isdisfavored
dataFit
BG
Prediction
Br(Y(1S)invisble)=0.6%[hep-ex/0611041, to appear in PRL]

Outline News on the Belle detector operation
 Super-hot topics of physics
 Other topics of physics
 Summary & Conclusion

Physics Publications in FY2006http://belle.kek.jp/belle/publications.html

Physics Publications in FY2006
http://belle.kek.jp/belle/publications.html

Prospects of BKSπ0γ TCPV analysis
Phys. Rev. Lett. 94, 231601 (2005)
Phys. Rev. D 74, 111104(R) (2006)?
(200x)…………………
5ab−1 : the error be compatible with the(largest estimation of) SM polution

275MBB
535MBB~1000MBB(*) If no drastic
improvement
in analysis

δS=0.1 @ 5/ab

Hope prompt increase of luminosity
Success of Crab is desiredSummary & Conclusion Belle DAQ Upgrade is going on
 For an entangled system (B0-B0b), again Quantum

Mechanics is supported
 Evidence of D0-D0b mixing is found for the first time
 Dark Matter search is performed. One theory
rejected Sincerely anticipating a success of Crab Cavity
operation

Limit of the current readout systemThe luminosity of KEKB will increase drastically due
to the crab cavity installation.
deadtime fraction will be ~20%
with the current readout system.

 We need a pipelined readoutsystem.

COPPER

Deadtime fraction (%)

 Trigger rate will be >1kHz andExtrapolated deadtime
No multi-stage
Event builder
No pipelined
readoutTrig. Rate(Hz)LEP

これまでの探索結果（つづき）

e+Invisible width of Z
Zにカップルするものに対するリミット
eLEPsingle photon counting (e+e-  γ invisible)
e++e e にカップルするものに対するリミット
e_qqにカップルするものに対するリミットは？ q_ZDMDMγMDMDMDM

実はまだ十分に探索されていないqM
DM
単純なＭＳＳＭなら上記のリミットが適用可
が、しかし…
_Next-to-MSSM等々qqがfavorされるモデルはいくらでも作れる
PRD 72, 103508 (2005) “Invisible quarkonium decays as a sensitive probe of dark matter”
matter”
hep-ph/0510147“Probing MeV Dark Matter at Low-Energy e+ee+e- Colliders”
Colliders”
hep-ph/0509024“Light neutralino dark matter in the next-to-minimal”
next-to-minimal”
hep-ph/0601090“Dark matter pair-production in bs transitions”
transitions”

実験の役目: 無数にある理論の可能性を一つ一つ排除する
もし見つけてしまったらラッキー（ダークホース狙いで万馬券）じゃあ、どのくらい期待されるか？
Relic density is denoted as follows

Ωh2 ≅0.1 pb ・ c<σ(χχSM) v >Ωh2 = 0.113  WMAPσ(χχSM) ˜ 18 pb
ここまではPDGより抜粋

Ω : relic densityh : Hubble constantv : 1/20 ~ 1/25qχ
_qχ

q
χ
_q
χσ(SMχχ) ≅ σ(χχSM), Γ(Υ(1S)χχ) = fΥ2ΜΥσ(bbχχ)Time reversal を仮定すると…

Br( Y(1S)χχ ) ~ 6x10−3 (mχ<4.73GeV/c2 ~ mb)
PRD 72, 103508 (2005) “Invisible quarkonium decays as a sensitive probe of dark matter”

これまでのベストリミットは < 23x10-3 (90% CL) by ARGUS (1986)

Trigger logic is important
For trigger issue, we need two charged tracks
Reach to outer most layer of CDC (pt ~250
MeV/c)
Reach to middle layer of CDC (pt ~120
MeV/c)“Opening anglecut” is necessary to+π
distinguish tracks−πyx

Special Trigger for Y(3S)π+π−Y(1S)invisible
data
MCControl sample
Υ(3S)  π+π−Υ(1S)
Υ(1S)  µ+µ−
通常のトリガー条件(>135o)では効率悪い
 出来るだけ、ゆるいカット条件が良い
 トリガーレート ~850Hz(通常の２倍のレート)までゆるめた、特別トリガーを実装して、データを取得した。

?

実は1トラック(pt>250)トリガーをプリスケール1/500で実装したので
2-track trigger & 1-track trigger
1-track trigger
トリガー効率をモニターできる

Special Trigger for Y(3S)π+π−Y(1S)invisible
data
MCControl sample
Υ(3S)  π+π−Υ(1S)
Υ(1S)  µ+µ−
通常のトリガー条件(>135o)では効率悪い
 出来るだけ、ゆるいカット条件が良い
 トリガーレート ~850Hz(通常の２倍のレート)までゆるめた、特別トリガーを実装して、データを取得した。

Trigger eff. = 89.8%
θrφ > 30o
ptfull > 0.30 GeV/c
ptshort > 0.17 GeV/cother cuts (後述)

実は1トラック(pt>250)トリガーをプリスケール1/500で実装したので
2-track trigger & 1-track trigger
1-track trigger
トリガー効率をモニターできる

244 events predicted
Br(Y(1S)invisible)=6x10-3

Y(3S)π+π−Y(1S)invisible Background Two-photon

2 prong ππ, ee, µµ …
 pt is balancedππππΥ(1S) Boosted (θ distribution)π+π−π0 ...
 π0 veto, γ energy cutsignalBGS/N:
1/301/8
recoil mass of π+π−- 今後の宿題 例えばこんな感じで直接探索と一緒のプロットは描けないのか？

110その他、結果が与えるインパクト
もう死んでるも同然の理論みたいだがProspects
90 %C.L
Super-forward µ-detector

SM : Y(1S)ννbarand Super-forward cal.
To be reach 2x10-4~500 fb-1

まとめ Y(1S)の見えない(invisible)崩壊の発見は、軽いダークマター(mb以下)を示唆する(かもしれない)かもしれない)
直接探索実験では探索できない領域
Br( Y(1S)invisible ) ~ 6x10-3 が理論期待値
従来の探索リミットは < 23x10-3 (90%CL) by ARGUS
 特別なトリガーでY(3S)のデータを2.9fb-1取得

Y(1S)の見えない崩壊の探索をした。
 残念ながら見つからなかったが、理論期待値に到達する探索が行えた。
Br( Y(1S)invisible ) < 2.5x10-3 (90%CL)結果の論文はPRLに投稿した ( hep-ex/0611041 )その他、結果が与えるインパクト (2)によるとΥという式が出てきて、これよりgravitino mass, m3/2, に与えるインパクトm3/2 > 1.5x10-7 eV
これまでは m3/2 > 0.3x10-7 eV だったが得られる

Prospects with more data
90 %C.L. limit

この論文の著者によれば、「SM予想値までは、探索するが価値ある」
らしい…

Prediction of
PRD 72, 103508 (2005)
To be saturated ~20 fb-1
due to “peaking BG”
SM : Y(1S)ννbar

２桁に及ぶ空白領域を何とか探索できないのか？
敵はY(1S)  µ+µ−, e+e−である。

FWD/BWD muon detectors
Υ(1S)µ+µ− : ~1/50 of now+/−5o+/−5oWe can cover < +/−1.5o region in principle
Because we have 100m straight section in tunnel

Belle>99 % of acceptance is covered for muon

Sensitivity for Y(1S)invisible
90 %C.L

FWD/BWD µ-detector

SM : Y(1S)ννbar

~99 % of acceptance is covered for e+e-EFC
Pb shield
 active detector !?

Sensitivity for Y(1S)invisible
90 %C.L

SM : Y(1S)ννbar

FWD/BWD µ-detector+ EFC
To be reach 2x10-4~500 fb-1
残り一桁を達成するためのアイデアは現在募集中

ダークマター探索に感度がある
Super-KEKB の物理χχ
例えば B→Kνν
標準理論で記述される崩壊ダイアグラム

ダークマター

ダークマター

ダークマター

ダークマター

もし予想(Br~4x10-635ab-1)より高い分岐比で発見したら…
ダークマターである可能性もある
これは、Y(1S)invisibleよりさらに軽いものに感度がある

110

Special: Loose 2-track Trigger

Trigger eff.
89.8%
Trig. effic.: monitored byprescaled 1-track Trrig.

Y(3S)π+π−Y(1S)invisible Background Two-photon

2 prong ππ, ee, µµ …
 pt is balancedππππΥ(1S) Boosted (θ distribution)π+π−π0 ...
 π0 veto, γ energy cut
signalBG

S/N:
1/301/8
recoil mass of π+π−