baryonic b decays
DESCRIPTION
Baryonic B decays. Outline: Introduction B + K + Threshold enhancement Pentaquark search B + p Charmed baryonic modes Two body decays Conclusion. J. Sch ümann National Taiwan Universit y ( B elle Collaboration). [email protected]. Moriond QCD ‘05. Electron 8 GeV. - PowerPoint PPT PresentationTRANSCRIPT
Moriond QCD '05 1
Baryonic B decaysJ. Schümann
National Taiwan University
(Belle Collaboration)Outline:
IntroductionB+ K+
Threshold enhancementPentaquark searchB+ p Charmed baryonic modes Two body decaysConclusion
Moriond QCD ‘[email protected]
J.SchJ.Schüümann,mann, 13.03.’05 Moriond QCD '05 2
The KEKB-factoryElectron 8 GeV
Electron 8 GeVPositron3.5 GeV
Positron3.5 GeV
Υ(4S) (10.58GeV/c2) = 0.425
Υ(4S) (10.58GeV/c2) = 0.425
Interaction Point
3Km
Tsukuba
J.SchJ.Schüümann,mann, 13.03.’05 Moriond QCD '05 3
Accumulated Data
Lpeak = 15.16 nb-1s-1
Lday 1 fb-1 Ltot = 377 fb-1
J.SchJ.Schüümann,mann, 13.03.’05 Moriond QCD '05 4
Belle Detector Aerogel Cherenkov Cnt. n=1.015~1.030
KLM / KL detection 14/15 lyr. RPC+Fe
TOF counter
ECL CsI(Tl)
SC solenoid 1.5T
Silicon Vertex
Detector
Central Drift Chamber small cell +He/C2H6
8 GeV e-
3.5 GeV e+
Extreme Forward Calorimeter
J.SchJ.Schüümann,mann, 13.03.’05 Moriond QCD '05 5
Introduction
Baryonic decays: a unique and well-established feature of B meson decay (but not charm decay)
B(2 body) < B(3 body) < B(4 body)Threshold enhancement in the invariant mass of the baryon-antibaryon system for 3-body BKBB decaysAngular distributions discriminate between decay mechanisms, e.g. two-body decays and fragmentationCan search for exotic states in 3-body and 4-body decays
J.SchJ.Schüümann,mann, 13.03.’05 Moriond QCD '05 6
gb s s
s B+ΛΛK+
First observation of bs s s decay
Signal Yield in 2D fit: 19.9Efficiency: 4.0%-6.9%Statistical Significance: 7.4σ
B : (2.91 0.38) x 10-6
+6.5- 5.1
+0.90- 0.70 PRL 93, 211801PRL 93, 211801
1.1. First Charmless B decay First Charmless B decay with two with two ΛΛ! !
2.2. Threshold enhancement.Threshold enhancement.
3.3. Complements BComplements BφφKK(*)(*)
(b(bsss penguin)sss penguin)
1.1. First Charmless B decay First Charmless B decay with two with two ΛΛ! !
2.2. Threshold enhancement.Threshold enhancement.
3.3. Complements BComplements BφφKK(*)(*)
(b(bsss penguin)sss penguin)
140fb-1
threshold peaking
J.SchJ.Schüümann,mann, 13.03.’05 Moriond QCD '05 7
Search for B+ΛΛπ+
No significant signal found
90% confidence-level upper-limit:
B (B+ΛΛπ+)<2.8x10-6
PRL 93, 211801PRL 93, 211801
140fb-1
1.1. Compare with BCompare with Bppppππ
2.2. bbuud transition with ss uud transition with ss poppingpopping
1.1. Compare with BCompare with Bppppππ
2.2. bbuud transition with ss uud transition with ss poppingpopping
ResultResult
Number of Background:
37.5±1.0Number of Observed events :
41Number of Signal UL:
< 21.7
b u
J.SchJ.Schüümann,mann, 13.03.’05 Moriond QCD '05 8
Improved B+ppK+measurement
Signal Yield in 2D fit: 216.5
Efficiency: 28.3%-35.2% with Mpp<2.85 GeV/c2
B(Belle): (4.59 0.50) x 10-6 (4.89 x 10-6 PRL92, 131801, 2004)
B(Belle): (5.30 0.58) x 10-6 , full range (charm veto for Mpp)
B(BABAR): (6.7 0.9 0.6) x 10-6 (81 fb-1, hep-ex/0408037)
+17.3- 16.6
140fb-1
+0.38- 0.34
threshold peaking
+0.45- 0.39
b s
J.SchJ.Schüümann,mann, 13.03.’05 Moriond QCD '05 9
Angular distribution: ppK+
& glueball search
Proton against K- (p against K
+) : flavor dependence!
ppK signal
bs dominant processFragmentation picture
us
uudduuus
K+ pp
p
p
K+ӨpX
at pp rest frame
No significant signal: B (B+ glueball K+) x B ( glueball pp) < 4.1x10-7
Possible Hints and Search for Glueball Production in Charmless Rare B DecaysChun-Khiang Chua, Wei-Shu Hou and Shang-Yuu Tsai(PLB544,2002)
Angular-Asymmetry:
A = N+-N-
N++N-
= 0.59 +0.08- 0.07
J.SchJ.Schüümann,mann, 13.03.’05 Moriond QCD '05 10
Improved B0ppKs measurement
threshold peaking
Signal Yield in 2D fit: 28.6
Efficiency: 15.4%-21.0% with Mpp<2.85 GeV/c2
B : (1.04 0.12) x 10-6 ( 0.78 x 10-6 PRL92, 131801, 2004)
B : (1.20 0.14) x 10-6 (full range, charm veto)
+6.5- 5.8
140fb-1
+0.26- 0.19
+0.32- 0.22
b s
J.SchJ.Schüümann,mann, 13.03.’05 Moriond QCD '05 12
Pentaquark search in BppKs, ppK+
Θ+(1540) : uudds (Belle) Θ+ K+ n Θ+ K0 p
B0 Θ+ pB0 ppK0, B ppKs
Search for B signal with a 20 MeV pKs mass window cut at 1540MeV, the nominal mass of the pentaquark
Θ++(1540) : uuuds (Belle,BABAR) B0 Θ++ p Θ++ K+ p
ddu us
Θ+K+n
su
ddu uu
d
p
d s
K0
Θ+
uudsd
J.SchJ.Schüümann,mann, 13.03.’05 Moriond QCD '05 13
Pentaquark search in ppKs/K+
Fixed background shape from sideband data
Count the events in signal region and compare with background estimation
Upper limit B(B0+p)x B(+pK0s)< 2.3x10-7
at 90% C.L.
+: Belle : 140 fb-1 ++: BABAR : 81 fb-1
++: Belle: B < 9.1 x 10-8
J.SchJ.Schüümann,mann, 13.03.’05 Moriond QCD '05 14
Improved B0pΛπ- measurement
Signal Yield in 2D fit: 48.8
Efficiency: 10.4%-12.6%
B: (2.62 0.31) x 10-6 (Mpp < 2.85 GeV/c2)
B: (3. 27 0.39) x 10-6 (full range) (3.97 x 10-6 PRL90, 201802, 2003)
140fb-1
+8.2- 7.5
+0.62- 0.51
threshold peaking
+0.44- 0.40
b s
J.SchJ.Schüümann,mann, 13.03.’05 Moriond QCD '05 15
Angular distribution: pΛπ-
π-
Λ
p
ӨpX
at pΛ rest frame
Λ
p
π-
ӨpX
at pπ- rest frame
Fragmentation picture
J.SchJ.Schüümann,mann, 13.03.’05 Moriond QCD '05 16
Theoretical prediction:Theoretical prediction:*Pole Model*Pole Model: Phys.Lett. B533 (2002)
B(B pΛγ ) ~ 1.2x10-6
B(B pΣ0γ) ~ 2.9x10-9
*QCD counting rules*QCD counting rules: (hep-ph/0405283)
B(B pΛγ ) ~ (1.2-2.4)x10-7
B(B pΣ0γ) ~ (2.8-6.5)x10-7
B+pΛγ
First observation!Simultaneous fit on BpΛγ & BpΣ0γSignal Yield for BpΛγ with MpΛ<2.4GeV/c2: 34.1
Statistical Significance: 8.6σ
B(BpΛγ ): (2.16 0.20) x10-6
B(BpΣ0γ):<3.3 x 10-6
140fb-1
+7.1- 6.6
+0.58- 0.53
bsγ MCpΛγSignal
threshold peaking
b s
J.SchJ.Schüümann,mann, 13.03.’05 Moriond QCD '05 17
B- C+ p -
264±264±20 20 signalsignalss
CC(2455)(2455)00
CC(2520)(2520)00
sidebasidebandnd
32.632.6
12.12.88
+ 6.6+ 6.6 - 5.9- 5.9
+ 5.7+ 5.7 - 5.0- 5.0
B-c+p- 20.1±1.5 ±2.0±5.2
B-c0
2455 p 3.67 ±0.36 ±0.95
B-c0
2520 p 1.26 ±0.12 ±0.33
B x 10-5
+0.74- 0.66+0.56- 0.49
~ 25% of the total Bcp- BF
b c u
d
Observation of a new 2-body decay
140fb-1
J.SchJ.Schüümann,mann, 13.03.’05 Moriond QCD '05 18
(c+p) massCC
++p)p)
M(c+ -)>2.6 & M(p-) >1.6GeV/c2
to remove c(2455/2520) & (1232)
B signals by E fit for each mass bin
B- C+ p -- M(c
+p) structure
B = ( 3.87 0.43 1.01 ) x 10 - 5
BW = 0.07 ±0.04
M = 3.35 0.02
6.2 significance
CC00CC
++--))
Low mass structure
+0.77- 0.72
+0.01-0.02
+0.04-0.03
J.SchJ.Schüümann,mann, 13.03.’05 Moriond QCD '05 19
MC J 2 /ndSolid line : 0 0.97Dashed line : 1 1.58
B- C+ p -
( by E fit for each mass bin )
Helicity distribution
data: dotsMC : histograms
M(c+p) <3.6GeV/c2
c+
(c+p)
direc.
in B - at rest
Helicity angle
p
Angular-Asymmetry:
A = |N+-N-|N++N-
= 0.32 0.14
J.SchJ.Schüümann,mann, 13.03.’05 Moriond QCD '05 20
B0 p, pp and other
140fb-1
B0 pp: 4.1 x 10-7
B0 p: 4.9 x 10-7
B0 : 6.9 x 10-7
90% confidence level UL:
Belle, 78fb-1 BABAR, 81fb-1
Belle: B+ J/p: 4.1 x 10-5
BABAR: B+ J/p: 2.6 x 10-5 B+ J/pp: 1.9 x 10-5
J.SchJ.Schüümann,mann, 13.03.’05 Moriond QCD '05 21
Conclusion
First b → sss hyperonic decay found
First b → s γ baryonic decay found
The threshold enhancement in the baryon-antibaryon pair for 3-body Bbaryon decayse supports the fragmentation picture
Intriguing structure found in the cp mass for Bcp- decays
No hints for pentaquarks and glueballs yet
Keep searching for all kinds of baryonic
decay channels, possible pentaquarks,
glueballs and especially direct CP violation
with increasing statistics
J.SchJ.Schüümann,mann, 13.03.’05 Moriond QCD '05 22
Λ
γ
p
θx
Photon energy and Angular distribution
Fit results in bins of cosθX with Mp<4.0GeV/c2
(Assuming XpΛ, calculated in X rest frame.)
bsγ MCSignal Yield
qq backgroundSignal Yield
Lab frame
J.SchJ.Schüümann,mann, 13.03.’05 Moriond QCD '05 23
BB0 0 ( (cc++p) p) --
M(c+p) structure
in 3, 4 body decays
CC++/0++/0 (2455/2520) excluded (2455/2520) excluded
BB- - ( (cc++p) p) --
B Signals byE fit
MC phase space, consistent with 4-body fine structures ?
MC 4-body phase spaceMC 4-body phase space
Prelim
inar
y
Prelim
inar
y
J.SchJ.Schüümann,mann, 13.03.’05 Moriond QCD '05 24
B0 C+ p - -
cc++++(2455)(2455) cc
00(2455)(2455)
cc++++(2520)(2520) cc
00(2520)(2520)
M(M(cc++))
Intermediate 3-body decaysIntermediate 3-body decays
B0 c+ p 10.3±0.9 ±1.2 ±2.7(*1)
B0 c2455++ p 1.15±0.22 ±0.14 ±0.30
B0 c24550 p 0.97±0.21 ±0.12 ±0.25
B0 c2520++ p 1.04±0.234±0.12 ±0.27
B0 c25200 p 0.33±0.19 ±0.054±0.09
41.0±8.0 35.2±7.8
58±14 19±11
M(c+)+c.c.
M(c+)+c.c.
(*1) total BF
140fb-1
J.SchJ.Schüümann,mann, 13.03.’05 Moriond QCD '05 25
Glueball SearchPossible Hints and Search for Glueball Production in Charmless Rare B DecaysChun-Khiang Chua, Wei-Shu Hou and Shang-Yuu Tsai(PLB544,2002)
Scanning through the mass region from 2.2 to 2.4 GeV regionNo significant signal
90% confidence-level upper limit:BF(B+ glueball K+) x BF( glueball pp) < 4.1x10-7
J.SchJ.Schüümann,mann, 13.03.’05 Moriond QCD '05 26
Particle Selection
We use the PID (ACC+CDC+TOF)PID (ACC+CDC+TOF) system to identify the charged particles.
Proton:
Kaon:
Pion:
Λ: reconstructed from Λpπ-
6.0 Kp
p
LL
L3.0
LL
L
p
p
6.0 LL
L
K
K
4.0 LL
L
K
K
pp KK ππ
(p)(p)
(K)(K) ~9% ~10%
((ππ)) ~4% ~8%Fake rate
Fro
m
TO
J.SchJ.Schüümann,mann, 13.03.’05 Moriond QCD '05 27
B Signal ReconstructionIn Υ(4S) rest frame:
e- e+
Υ(4S)
B
Be- e+
∆E
Mbc
2D scatter plot2D scatter plot
1D projection plot1D projection plot
J.SchJ.Schüümann,mann, 13.03.’05 Moriond QCD '05 28
B decay continuum events
Υ(4S)
The main background for B0pΛπ- and B+ΛΛπ+ is continuum qq events. (q=u,d,s,c). The Topology of continuum events and B decays are different. We choose |cosθThrust| S⊥ R2
so R4so R2
oo R3oo R4
oo as the fisher input and combine it with cosθB to calculate the likelihood ratio.
We define the Super-fox wolfram moment (F) like:
We use Fisher’s discriminant to optimize the coefficients.
Background suppression
SRRF Thrustsoi
ii
ooi
ii |cos|
4,24,3,2
J.SchJ.Schüümann,mann, 13.03.’05 Moriond QCD '05 29
udsuds
offoff Data sidebandData sideband
charmcharm
Background SuppressionSFW Moment (F)SFW Moment (F)
cosθB distributioncosθB distribution
udsuds
offoff Data sidebandData sideband
charmcharmSignal MC
udsuds charmcharm
offoff Data sidebandData sideband
Likelihood Ratio (LR)Likelihood Ratio (LR)
bs
s
LL
LLR
Optimized by
studybs
s
J.SchJ.Schüümann,mann, 13.03.’05 Moriond QCD '05 30
Signal Extraction
PDFs: Background modeling: a line (curve)
to represent the ∆E and the following parametrization first suggested by ARGUS group to represent the Mbc.
Signal modeling: a double Gaussian for ∆E and a Gaussian for Mbc.
])/(1(exp[)/(1)( 22beambcbeambcbcbc EMEMMMf
N
iibcibibcis
BS EMBPEMSPeL1
)( )],(),([
1D-binned fit: maximum Likelihood fit Branching fraction are calculated by ∆E fit Mbc fit for cross-check.
2D-unbinned fit (∆E-Mbc): Extended maximum likelihood fit.
∆E
∆E Mbc
Mbc
J.SchJ.Schüümann,mann, 13.03.’05 Moriond QCD '05 31
Angular distribution: ppK+
Background yield of ppK+
Consistent with qq background process
No fragmentation signature in J/ψK+
J/ψK+ (J/ψpp)