Projektbericht BELLE Vorstandssitzung 8. Juni 2006 KEK 高高高高高 , Projektbericht BELLE • Rekordluminosität • SVD Upgrade bei BELLE • Neue wichtige Resultate Collaboration • HEPHY Physik-Analysen
Jan 09, 2016
Projektbericht BELLE Vorstandssitzung 8. Juni 2006
KEK 高エネルギ ,
Projektbericht BELLE
• Rekordluminosität
• SVD Upgrade bei BELLE
• Neue wichtige Resultate
Collaboration
• HEPHY Physik-Analysen
Projektbericht BELLE Vorstandssitzung 8. Juni 2006
Lpeak=1.62 × 1034cm-2sec-1
design=1034cm-2sec
KEKB Collider
e-
8GeV
e+
3.5GeV
= 0.425
B-Factory(on the 4s resonance)
B-Factory(on the 4s resonance)
BBthreshold
Projektbericht BELLE Vorstandssitzung 8. Juni 2006
Ikado et al hep-ex/0604018
Signal
One B (tag) fully reconstructed
Remaining energyof signal B in ECL
•Pure leptonic decay
2.05+0.65-0.55(stat)
4.0
Projektbericht BELLE Vorstandssitzung 8. Juni 2006
Addresses the same physics issue as Bs- Bs mixing _
signal
K*other B
Mohapatra. Nakao, Nishida et al hep-ex/0506079
CDF
CDF
First Observation of bd
Projektbericht BELLE Vorstandssitzung 8. Juni 2006
Current status
CPV angles only:η=0.321±0.027=0.193±0.57
sides only:η=0.342±0.0
2 =0.216±0.06
Constraints from “Loop” Constraints from tree
Projektbericht BELLE Vorstandssitzung 8. Juni 2006
HEPHY Physik-Analysen
Christoph Schwanda: B l B l B l Vub
Laurenz Widhalm: Formfaktoren semileptonischer D° Zerfälle
Franz Mandl+G.L+H.D:BRs der inklusive Zerfälle D° KK () X Gerhard Leder + L.W.: BRs der inklusive Zerfälle Ds Gerald Richter: Dekohärenz Modelle verschränkter B-Paare Winfried Mitaroff: Y(5S)Bs
(*)Bs(*)[D0K0
s]
Projektbericht BELLE Vorstandssitzung 8. Juni 2006
Ktag
D
mass-constrained vertex fits
e+ e-3.5 GeV 8 GeV
K
K
D0
slow
e/µ
D*-
„inverse“ fit
tag side
Method of Reconstruction (Event Topology)
D*
signal side
additional primary mesonsIP
note:• all possible combinations tried in parallel• cuts after complete reconstruction• equal weight for remaining combinations no event loss due to particle exchanges!
•Semileptonic Formfactors
Projektbericht BELLE Vorstandssitzung 8. Juni 2006
Summary of Signal / Background Decomposition
Results (282 fb-1 of BELLE data) Ke K e
signal events 1318
± 37stat ± 7syst
1249
± 37stat ± 25syst
126
± 12stat ± 3syst
106± 12stat ± 6syst
fake D0 bkg 12.6 ± 2.2 12.2 ± 4.8 12.3 ± 2.2 12.5 ± 4.5
semileptonic bkg* 6.7 ± 2.6 10.0 ± 2.5 11.7 ± 1.2 12.6 ± 1.9
hadronic bkg** 11.9 ± 5.6 62.1 ± 23.9 1.8 ± 0.7 9.7 ± 3.7
fake-D0 bkg
Kl bkg
D0 eD0 e
D0 D0
l bkg
D0 eD0 e
D0 D0 hadronic bkg
m² / GeV²
•*error dominated by MC statistics • ** error dominated by fit errors & bias special bkgsample
MC
data
data
data
data
remaining signal
Projektbericht BELLE Vorstandssitzung 8. Juni 2006
Absolute Branching Ratios
BRs (%) this analysis PDG(2005)
CLEO-c (hep-ex/0505035)
K-e+ 3.45 ± 0.10stat ± 0.19syst 3.62 ± 0.16 3.44 ± 0.10stat ± 0.10syst
K-+ 3.45 ± 0.10stat ± 0.21syst 3.20 ± 0.17
-e+ 0.279 ± 0.027stat ± 0.016syst 0.311 ± 0.030 0.262 ± 0.025stat ± 0.008syst
-+ 0.231 ± 0.026stat ± 0.019syst 0.24 ± 0.04
• ratio to total number of recoil D0 tags
• efficiency correction • corrected for bias due to differences data/MC
(1.9%±3.9%)
Projektbericht BELLE Vorstandssitzung 8. Juni 2006
Form Factors – Comparison with Models
ISGW2 modellattice calculation modified pole model
D0 lD0 l
D0 lD0 l
pole mass (GeV)
Kl 1.82 ± 0.04stat ± 0.03syst
l 1.97 ± 0.08stat ± 0.04syst
simple pole
Kl 0.52 ± 0.08stat ± 0.06syst
l 0.10 ± 0.21stat ± 0.10syst
modified pole(poles fixed at theo. values)
fit results
f+(0)
Kl 0.695 ± 0.007stat ± 0.022syst
l 0.624 ± 0.020stat ± 0.030syst
preprint hep-ex/0604049, submitted to PRL
Projektbericht BELLE Vorstandssitzung 8. Juni 2006
D0(K+K-) XData Generic MC
K0K0
D0 D0
K+K-
X
•D0 - BranchingRatios
Projektbericht BELLE Vorstandssitzung 8. Juni 2006
Mass window = 255- 141(side-extr)=114
D0(K+K-) X
Mass window D0: 1.84<M(D0)<1.89
Mass window : 1.00<M()<1.04
Mass window D0= 332-80(sideband)=252 Mass window D0=191-25(sideband)=166
Mass window =458-182(sideband-extr) =276
Generic MCData
BG?=4*35
Correct BGshape from MC ?
D0
D0
0.37%+/-0.04
1.02%+/-0.141.71% +/- 0.76
0.39%+/-0.012
•PDG
Projektbericht BELLE Vorstandssitzung 8. Juni 2006 drydiff
gen MC m(K+K-) RS-WS comparison with data (*), scalefactor 0.445
green D0 X
pink not from D0
blue D0 K+K-XX
yellow no D0
red no K+(K-)
Projektbericht BELLE Vorstandssitzung 8. Juni 2006 fitdat
DATA FIT m(K+K-) 3 Gaussians + Polyn. 4th order
Projektbericht BELLE Vorstandssitzung 8. Juni 2006 Missing Mass for D0 X
Data
Mass window : 1.00<M()<1.04
Generic MC
K0 K0
Projektbericht BELLE Vorstandssitzung 8. Juni 2006
Ktag
D
mass-constrained vertex fits
e+ e-3.5 GeV 8 GeV
K+
Ds-
µ
Ds*-
„inverse“ fit
tag side
Method of Reconstruction (Event Topology)
signal side
additional primary pionsIP
...•Ds inclusiveExample Ds XPDG:(18+/-10)%or exclusive:(semi)leptonicDs BaBar(0.65+/-0.08)%Ds(6.4+/-1.5)%Ds l (2.0+/-0.5)%
Ds
Signal
Projektbericht BELLE Vorstandssitzung 8. Juni 2006
New: Ds → and fDs
2
2
222
22
18
)(
s
ss
D
lDlD
csFls m
mmmf
VGlD
sDf
BaBar
sD
c
s
W
Helicity-suppressed leptonic decay:
• directly related to decay constant fDs
• feeds interpretation of B, Bs mixing
Analysis Method: “D reco” in e+e- → cc
Single best measurement of decay constant!
ss DD*
*
0
D
D
D
D
s
D reco side
Signal peak in ss DD
MMM *
310)9.03.08.05.6()( sDMeV)19617279( syststat
ss DDf
BaBar (230fb-1):
Lattice QCD:
MeV)17249( sD
f
(normalize to Ds → )
Projektbericht BELLE Vorstandssitzung 8. Juni 2006
Best Candidate Selection
• signal yield can be increased by a „best candidate selection“ in case of ambiguities, e.g. by choosing maximal „slow“ gamma momentum• improvement: ~40%• important: no bias on background!• a cut on the Ds fit (not done in the plots) further increases the yield
Ds invariant mass Ds invariant mass
signal / no ambiguitysignal / several associationssignal / lost because wrong candidate selectedbackground
no best candidate selection largest “slow” gamma energy taken
Projektbericht BELLE Vorstandssitzung 8. Juni 2006
DATA (ca. 3.2% of available statistics)
Ds invariant mass
Fit: 705 events ca. 22000 Ds expected in total
• first look into data (only 3.2% of available data)• simple fit gaussian + linear curve for rough estimate
•hope: reconstruction of muon and neutrino of Ds or Ds will further reduce ambiguity enhancement of signal• cuts are still under development•Ds needs suppression of remaining energy in ECL, similar toB analysis
• Room for improvement• also best candidate selection might be further improved•Cross-check with hadronic channels, i.e Ds
Projektbericht BELLE Vorstandssitzung 8. Juni 2006
The decay
• βγcτB0
= 196 μm(LAB)
R t expt 2GCORE
CORE
2
expt 2GTAIL
TAIL
2
exp t 2GCOREk
● Δm = 0.489 1012 ћs-1 = 0.754 τ
B0-1
beam axis3.5 GeV e+8 GeV e-
interaction point(IP) =
primary vertex(PV) decay point 2
= secondary vertex
entanglement region
l-
decay point 1 =
secondary vertex
l+
K0s π-
π +
μ+
typical Υ(4S)
resonance decay
z0 , t
0
z1 , t
1
z2 , t
2
t
B0
B0
θ
B0 B0
Gerald Richter
Projektbericht BELLE Vorstandssitzung 8. Juni 2006
Adapted response function model
R t expt 2GCORE
CORE
2
expt 2GTAIL
TAIL
2
exp t 2GCOREk
sum of 2 gaussians +back to back neg. exponential
“gaussian pagoda”resolution function R(t)
shown for t1 parametergood accordance of fit
function up to +/- 4 mm
Projektbericht BELLE Vorstandssitzung 8. Juni 2006
applied cuts to get fit working
lower tailcut
● varied the symmetric quantile cuts, to find point, where the ML fit is not disturbed by tails.
● with lower = upper percentage of histogram entries within the ± 40 τ
B0 window removed
● t1: 0, 1, 2, 4 %● dt: 0, 1, 2 %
upper tailcut
Projektbericht BELLE Vorstandssitzung 8. Juni 2006
• for 2 cases of fixed dt quantile cuts 1%, 2%
• behaviour of the ML fit result for a given
λTRUE
= 0
• with increasing cut percentage, λ
FIT pulled
towards 0
• cutting too much will impair error model correctness
• 2% for both parameters looks like a good choice.
fit results on signal BELLE-MC with varied quantile cuts fit works
BELLE-MC with different in preparation