Search for BNV, LNV, LFV at (Super-) Belle/KEKB
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Transcript of Search for BNV, LNV, LFV at (Super-) Belle/KEKB
Search for BNV, LNV, LFV at (Super-) Belle/KEKB
September 22, 2007Search for Baryon and Lepton Number Violation Int’l Workshop @ LBL
Toru Iijima / Nagoya University
e+ source
Ares RF cavity
Belle detectorSCC RF(HER)
ARES(LER)
The KEKB Collider
e- (8.0GeV) × e+ (3.5GeV)⇒U(4S) →BB⇒Lorentz boost: bg = 0.425
Finite crossing angle- 11mrad ×2
Operation since 1999.
Peak luminosity 1.71 x 1034 cm-2s-1 !
3
Belle Detector
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~1010 BB & tt /year !!
Crabcavities
KEKB / Belle Major Upgrade
4
KEKB Integrated Luminosity
Lpeak = 1.71034cm-2s-1
Ltot = 710 fb-1 (Jun.30, 2007)
world records !
s(BB) ~ 1.1nb, s(tt) ~ 0.9nb
8.0x108 BB + 6.3x108tt
NBB/tt=O(109)
NBB/tt=O(1011)
NBB/tt=O(107)@ CESR
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Unique opportunity to study BNV, LNV, LFV in higher generation !
Hou, Nagashima, Soddu, PRD72,095001 (2005) B,L violating t, D, B decays with right-handed four-fermion
couplings.
BNV in Higher Generation
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proton decay limits;2R 0 -4
u-39
udBr( p C) 1.6 10 5.9 10
27.5 R
0 -5 - 0s
3uuBr( pK ) 10 1.4 1C 0
2R -4 -30
uusBr( ) 1.3 10 2.3 1C 0
2R -7 -41
uudCBr( p ) 2.8 10 1.0 10t 30(p ) >25×10 yr
+ 30(p e +X) >0.6×10 yr
2R ucs+ -29Br(D ) 1.3 10C
D 2R uc0 -29
sBr(D ) 1.0 10C 2R ucd
0 -39Br(D p ) 4.0×10C
, 2Rcc 0,+ -28
ccbBr(B ) 1.0 10C
B2R
c uc
0 -30bBr(B ) 4 10C 2R ucb
-27Br(b cu ) 1.3×10C 2R -27
uubBr(b uu ) C 2.4×10
BNV t/D/B decays are strongly suppressed by the proton stability,
But
Experimental redundancy is still important !
NP search in t decays
In the 3rd generation– Probe for the NP flavor mixing between 3⇔1/3⇔2 gen.
Heavy – Rate enhancement– Q>0 for decays to baryonic final states.
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BNV
LNV
LFV
t lepton is an unique laboratory to study…
t lepton is the charged lepton, which is …
t-pg, pp0, pK0, Lp-, Lp-
B-L conserving. B-L violating.
t-e+/m+ + h-h- (h=p,K)
t-e-/m- + g, l+l-, h+h-, h0, V0
BAULeptogenesis
General Analysis Procedure Signal side:
t decay of interest
Tag side: t 1 trk w/ n g + missing– 1-prong decays occupy >80% of
the t decay.– Loose constraint on n based on
Pmiss, M2miss.
Background– tt, continuum (qq), mm, ee,
…
Particle ID
Signal evaluation based on Minv ~ Mt & DE ~ 0
Signal region is open after analysis cuts are finalized.
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t+
t-
p+
n
Lp-
p
p+Signal side
Tag side
DE=
ER
ec
– E
CM
Kinematical Constraint Use correlation between m2
miss and pmiss.
Signal decays distribute around m2miss ~ zero
(no. n on the signal side).
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t+
t-
p+
n
Lp-
p
p+Signal side
Tag sideSignal MC Data
qq MC (uds)
tt MC
Y.Miyazaki et al., PLB632(2006)51-57
This cut removes 81% of ttand 77% of qq backgrounds, while keeping 89% of the signal.
Hadron-ID @ Belle Hadron-ID @ Belle is based on
the response of sub-detectors;– Threshold-type Aerogel
Cherenkov Counter (ACC)n = 1.011.03 depending on q
– Time-Of-Flight (TOF)– Ionization loss in CDC
(dE/dx)
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Combined to form a likelihood;
Use a cut on the likelihood ratio;i i i iL =L(ACC)×L(TOF)×L(dE/ dx)
i
i j
LP(i : j ) =
L +L
Proton-ID performancew/ a nominal cut Eff(p) = 70% Fake(pp) = 4% Fake(Kp) = 11%
Pth(p) = 0.99 0.57 GeV/cPth(p) = 6.6 3.8 GeV/c
t pg, pp0 analyses use a
different cutAt Super-Belle, large improvement is expected by using Ring imaging type Cherenkov detectors
L Reconstruction The L candidates are reconstructed via
pp- decay channel. Selection parameters;
– Angle difference between PL and IP –VTX.– Flight distance of L– Closest approach of the L daughter tracks
to IP. Particle ID cut for daughter tracks.
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L selection efficiency ~ 80%Purity ~ 90%
Y.Miyazaki et al., PLB632(2006)51-57
Signal MC
DataHisto: tt +qq MC
tpg, pp0
tp g (86.7fb-1) tpp0 (153.8fb-1)
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Nobs = 16
Nbkg = 9.1±1.7 (expected)
Br (t-pg) < 3.0×10-7
Nobs = 70
Nbkg = 52.2±7.3 (expected)
Br (t-pp0) < 6.5×10-7
BELLE-CONF-0433hep-ex/ 0408117
5s signal box
D=6.9±4.3 D=17.8±11.1
(UL determined by an unbinned ML fit)
t Lp @154fb-1
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B-L conserving (t- Lp-)
B-L violating (t- Lp-)
Con. Vio.
Eff(%) 11.8 11.7
Nside 5 5
Nbkg(exp’d) 1.7±0.8
1.7±0.8
Nobs 1 0
S90 2.77 1.47
Br (×10-7) <1.3 <0.70
We evaluate UL using 5 sellipse. BKG are extrapolated from 15s box assuming flat dist.
S90: Feldman-Cousins UL of #signals @ 90% CL. includingsystematic errors (POLE)
Y.Miyazaki et al., PLB632(2006)51-57
5 s ellipse
tt MCqq MC (uds)
BKG: tt (~1/2) + qq (~1/2) Only a few background Will be improved by 1/Lint
LFV in t Decays• Probe for 3⇔1/3 ⇔2 gen.
mixing in the charged lepton sector.
• Br(t) = O(103-5) x Br(m). Enough chance to see tmg or tlll.
• The two decays have different sensitivity for different NP models.
( )e
0
( )e223(13)l
(m )
t3l, lh
( )s
( )s
h
tlg
2 2 2
2 2 2
2 2 2
ee e e
e
e
m m m
m m m
mm m
Slepton mass matrix
tlg, lh,lh’,lp0signaldata
t→mg
t→mh(→gg)
t→mg,eg @535fb-1 (hep-ex/0705.0650 submittedd to PLB)
Br(t→mg)<4.5x10-8 (90%C.L.) Br(t→eg)<1.2x10-7 (90%C.L.)
t→e/ m + ,h h’,p0 @ 401fb-1 (PLB648, 341 (2007))
Br(t→lh,lh’,lp0) <(6.5-16)x10-8 90%C.L.
⇒Upper limits for LFV t decays are approaching O(10-8)
signal regionBkg. from tt/mm + initial state g
t→e/ m + ,h h’,p0 Only a few background Will be improved by 1/Lint
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t→lll: Background suppression
Signal topology BG events
electron-veto on the tag-side (e-e+e- and e-m+m-)g-conversion veto (e-e+e- and m-e+e-)m2
miss and pmiss
(e-e+e-, m-m+m-, e-m+m-, m-e+e-)
Bhabha(mm) eemm(eeee)
mode m-
m+m-e-e+e- m-e+e-
e -
m+m-
m+e-e-
e+m-m-
Dominant bkg.
ttqqmmmm
Bhabhaeeeett
eemmttmm
ttqq
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tlll @535fb-1
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tmmm
teee Efficiency: 6.0% - 12.5% Nbkg (expected) = 0 – 0.4 events No event found in the signal region Obtained upper limit (90%CL) Br<(2.0-4.1)×10-8
Improved by 4.9-7.0 fromBelle previous results @ 90fb-1
mode U.L. of Br @90%C.L.
t-e-e+e- 3.6×10-8
t-m-m+m- 3.2×10-8
t-e-m+m- 4.1×10-8
t-m-e+e- 2.7×10-8
t-e+m-m- 2.3×10-8
t-m+e-e- 2.0×10-8
datasignal
preliminary
The most stringent upper limits among LFV t decays
New !
Still a few background Will be improved by 1/Lint
tlV0 @543fb-1
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mode Belle(158fb-1)@ 90%C.L.
Belle(543fb-1)@90%C.L.
t-m-f 7.710-7 1.310-7
t-e-f 7.310-7 7.610-8
t-m-w - 9.010-8
t-e-w - 1.810-7
t-mK*0 3.910-7 6.110-8
t-e-K*0 3.010-7 8.010-8
t-m-K*0 4.010-7 1.110-7
t-e-K*0 4.010-7 7.710-8
t-m-r0 2.010-7
t-e-r0 6.510-7
t→mf
t-m-K*0
New !
Still a few background Will be improved by 1/Lint
t signal m/e + 2 chg. trackst tag m/e + ng
Background: tt, qq
Continuum bkg. suppression by t flight length & R2
2D PDF Likelihood ratio
tlhh @158fb-1
LR= >0.45
L +L
<7.3
<2.0
<3.0
<3.1
<4.8
<3.4
<8.0
<4.4
<7.2
<1.6
<1.9
<2.7
<7.3
<2.9
UL (x10-7, 90%CL)
Y.Yusa et al., PLB640(2006)138-144
Signal MCqq MC (uds)
LNV
* * * **
*2007/9/22 18Toru ijima, B-L workshop*Still a few background Will be improved by
1/Lint
Summary for non-SM t Decay Search
t→3leptons
t→ef,ewt→ ,mf mw
→t lg
t→lh,lh’,lp0
t→lhh’
New results this summerUpp
er li
mits
of
LFV
t d
ecay
▼▼
▼
▼▼▼▼ ▼
BNV
2007/9/22 19Toru ijima, B-L workshopULs for all LFV t decays are approaching the 10-8 level
Future prospect Extrapolated sensitivity at 5ab-1
Estimatedupper limitrange of Br
PDG2006BelleBabar
based on eff. and NBG of most sensitive analysis
Ambiguity due to the stat. error of the bkg. estimation in the preset data.
Interaction RegionCrab crossingq=30mrad.by*=3mmNew QCS
Super-KEKB
Linac upgrade
More RF power
Damping ring
New Beam pipe
L 2ere
Iyy*RLRy
Increase beam currents• 1.6 A (LER) / 1.2 A (HER) → 9.4 A (LER) / 4.1 A (HER)
Smaller by*
• 6 mm→3 mm
Increase xy
• 0.059→>0.24(W-S)
L=8x1035cm-2s-1
8GeV (e+, 4.1A) 3.5GeV (e-, 9.6A)
Crab Cavity
Superconducting crab cavities (1LER and 1HER) have been installed, and being tested at KEKB.
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L 2ere
Iyy*
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Crab Status Crab cavity installed in Jan. 2007. Beam-beam tune shift (0.088) achieved at low currents. Beam current gradually increased
L=1034cm-2s-1 with crab crossing by June 2007. Still need R&D/tuning to see L improvement (simulation predicts
x2).
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HER LER
Crab OFF
Crab ON22mrad crossing
crab crossing
y (beam-beam simulation)
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Belle Upgrade
SC solenoid1.5T
New readout and computing systems
CsI(Tl) 16X0
g pure CsI (endcap) Aerogel Cherenkov counter + TOF counter
g “TOP” + RICH
Si vtx. det. 4 lyr. DSSDg 2 pixel/striplet lyrs. + 4 lyr. DSSD
Tracking + dE/dx small cell + He/C2H5
remove inner lyrs.
Use fast gas
m / KL detection 14/15 lyr. RPC+Fe
g tile scintillator
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Summary• B-factories provide an unique opportunity to
study BNV, LNV, LFV in higher generation.
• The present KEKB provides 6x108 tt pairs New results for LFV search using the full data sets are approaching to O(10-8).
• Super-KEKB will provide x ~50-100 statistics. The search region will enter into O(10-9) for many decays. Good chance to see LFV t decays. BNV can be tested too.
Backup Slides
International Collaboration: Belle
13 countries, 55 institutes, ~400 collaborators
Aomori U.BINPChiba U.Chonnam Nat’l U.U. of CincinnatiEwha Womans U.Frankfurt U.Gyeongsang Nat’l U.U. of HawaiiHiroshima Tech.IHEP, BeijingIHEP, Moscow
Nagoya U.Nara Women’s U.National Central U.National Taiwan U.National United U.Nihon Dental CollegeNiigata U.Osaka U.Osaka City U.Panjab U.Peking U.U. of PittsburghPrinceton U.RikenSaga U.USTC
Seoul National U.Shinshu U.Sungkyunkwan U.U. of SydneyTata InstituteToho U.Tohoku U.Tohuku Gakuin U.U. of TokyoTokyo Inst. of Tech.Tokyo Metropolitan U.Tokyo U. of Agri. and Tech.Toyama Nat’l CollegeU. of TsukubaVPIYonsei U.
IHEP, ViennaITEPKanagawa U.KEKKorea U.Krakow Inst. of Nucl. Phys.Kyoto U. Kyungpook Nat’l U. EPF Lausanne
Jozef Stefan Inst. /
U. of Ljubljana /
U. of MariborU. of Melbourne
b s
• CP violation
• Precise CKM
• Rare decays– FCNC decays
– Tauonic decays
• t decays – Lepton flavor violation
– CPV in lepton sector
Physics Targets at Super-B
, .b s s etc
, .b c etc
Using O(1010) B and t (~100 x now)
1 1 1, , , | |, | |ub tdV V
.etc
0 0 0, ,B K K K K K
Search for new origin of flavor mixing and CPV.
Br~O(10-89) at Super B factory !
T LFV Prospect
tmg
tmh
tmmm
tmg suffers frombackground due to ISR.
Super-KEKB (cont’d)
Head-on collision w/ Crab cavityNew crab cavity
Ante-chamber /solenoid for reduction of electron clouds
Circular-chamber
Build-up ofelectron clouds
Ante-chamberAnte-chamberwith solenoid field
Will be tested in 2006.
Detector Upgrade
Higher background
Higher event rate
Require special features- low p m identification - full recon. eff.- hermeticity ; n “reconstruction”
- radiation damage and occupancy- fake hits and pile-up noise in the EM
- higher rate trigger, DAQ and computing
Issues4 Vertexing
4 Tracking
4 Particle ID
4 EM Cal
4 KL & m
4 Vertexing
4 Tracking
4 Particle ID
4 EM Cal
4 KL & m
Pixel det.
Small cellFast gasSi-tracker
F-DIRC+TOPAerogel RICH
Pure CsILiquid-Xe etc.
LSTScintillator
4 Fully pipelined readout4 Large scale computing
4 Fully pipelined readout4 Large scale computing
New Challenge! Intensive R&Ds!