new results from b a b ar, marie-hélène schune, bnl, may 20th 20021 new results from b a b ar...
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New results from BABAR, Marie-Hélène Schune, BNL, May 20th 2002 1
New results from BABAR
Marie-Hélène SchuneLaboratoire de l’Accélérateur LinéaireOrsay, France
All numbers are preliminary
Brookhaven National LaboratoryParticle Physics Seminar
May 20, 2002
New results from BABAR, Marie-Hélène Schune, BNL, May 20th 2002 2
New results from BABAR
• I will not talk about – sin2 in charmonium modes :
1. BABAR and PEPII2. Charmless B decays :
– B0, K or KK – B000
3. The “B recoil” physics :– semileptonic branching fractions of B+ and B0
– D meson production in B decays
sin20.750.09 0.04
56 fb-1
Winter 2002 conferences
New results from BABAR, Marie-Hélène Schune, BNL, May 20th 2002 3
– CKM matrix has 4 real parameters (one phase included)
– 2 are well known :• =|Vus|=sin(Cabbibo)=0.22050.0018
• A =|Vcb|/2 =0.83 0.06
– unitarity of the CKM matrix leads to constraints that can be tested:
2 3
2 2 4
3 2
1 / 2
1 / 2
1 1
ud us ub
cd cs cb
td ts tb
V V V A i
V V V V A
V V V A i A
CKM matrix for 3 generations
Bd ,, …
Bd J/Ks, D*+D*-,…B D*, DK, K
B , , l, l,…
BdBd, Bd
B D(*)l,D(*),…
* * * 0ud ub cd cb td tbV V V V V V
Unitarity Triangle
New results from BABAR, Marie-Hélène Schune, BNL, May 20th 2002 4
DIRC (PID))
1.5T solenoid CsI(Tl) EMC
Instrumented Flux Return
Silicon Vertex Tracker
Drift Chamber
e+
(3.1GeV)
e-
(9GeV)• SVT: 97% efficiency, 15m z resol. (inner layers, perpendicular tracks)• Tracking : pT)/pT = 0.13% PT 0.45%• DIRC : K- separation >3 for P<3.5GeV/c• EMC: E/E = 1.33% E-1/4 2.1%
The BABAR detector
New results from BABAR, Marie-Hélène Schune, BNL, May 20th 2002 5
New results from BABAR, Marie-Hélène Schune, BNL, May 20th 2002 6
PEP-II asymmetric B Factory9GeV e- on 3.1GeV e+ :s~10.58 GeV
• for B0 : coherent neutral B pair production and decay (p-wave)
• boost of (4S) in lab frame : =0.55
-e e (4S) BB
New results from BABAR, Marie-Hélène Schune, BNL, May 20th 2002 7
Running at the (4S)
Off On
)MeV(ME )S4(CM
PEP-II
BABAR
28.0hadr
bb
New results from BABAR, Marie-Hélène Schune, BNL, May 20th 2002 8
• May 2nd : – PEPII delivered : 87 fb-1
– BABAR recorded : 83 fb-1 (including 9 fb-1 off peak )
• results for 55 fb-1
B factory performances
daily integrated luminosity
New results from BABAR, Marie-Hélène Schune, BNL, May 20th 2002 9
2 - Charmless B decaysStudy of penguins diagrams Possible direct CP violation
• B0, K or KK – Branching fractions (eff , )
– CP violations measurements (eff , )
• B000 (eff )
(,)
New results from BABAR, Marie-Hélène Schune, BNL, May 20th 2002 10
B0 and CP violation (1)
/
( ) 1 sin cos4
t
d d
ef t S m t C m t
BF(B0) << BF(B0K) penguins contributions may be large
Hadronic Penguin Amplitude (P)
W
tb d,s
u
u
g
b u,ccu ,
d,s
W
Tree amplitude (T)
Tree only : =fe2i
C=0 S=sin(2)
Tree+Peng.
C 0 S=sin(2eff)
2
2 2
12 m
1 1
q A
p A
S C
mixing e-2i
New results from BABAR, Marie-Hélène Schune, BNL, May 20th 2002 11
B0 and CP violation (2)
/
( ) 1 sin cos4
t
d d
ef t S m t C m t
0 0
0 0
sin cosB Bd d
B B
N NA S m t C m t
N N
00tag BB 00
tag BB
perfect flavour tagging & time resolution
00tag BB 00
tag BB
realistic mis-tagging & finite time resolution
S=0.7and C=0.
f+ : B0 tag
New results from BABAR, Marie-Hélène Schune, BNL, May 20th 2002 12
• Main variables :– |cosS| : angle between the B0
sphericity axis and the sphericity axis of the rest of the event
– F : Fisher discriminant based on “energy flow cones” (CLEO)
B0, K or KK kinematics
sθ
sθ
“Jets”
Candidate
Axis of “Rest Event”
-e e qq
Axis of “Rest Event”
Candidate
0- 0e e B B |cosS|
Candidate
New results from BABAR, Marie-Hélène Schune, BNL, May 20th 2002 13
Signal MC ~2.6 MeV
background
B0, K or KK : mES and E• Energy substituted mass :
– dominated by the beam energy knowledge
• E : assume mass
– dominated by the tracking resolution(E)~26 MeV
2
*2/ 2ES Bm s p
* / 2BE E s
KKK
~325 MeV
background
mES
45 MeV
New results from BABAR, Marie-Hélène Schune, BNL, May 20th 2002 14
B0, K or KK : the PID (1)The DIRC
• Measure Angle of Cherenkov Cone in quartz
– Transmitted by internal reflection– Detected by PMTs
2 2
1cos and c
pn p m
c
Particle
Quartz bar
Cherenkov light
Active Detector Surface
New results from BABAR, Marie-Hélène Schune, BNL, May 20th 2002 15
DIRC PMT +light catchers
DIRC stand-off box, magnetic shielding and electronic crates
New results from BABAR, Marie-Hélène Schune, BNL, May 20th 2002 16
B0, K or KK : the PID (2)• DIRC performances measured on data using D*D0
and D0 K
(c) 2.2 mrad K/ separation
2.5
p range of 2-body B decays at BABAR
New results from BABAR, Marie-Hélène Schune, BNL, May 20th 2002 17
0 0
Kπ 0 0
Kπ 2 2
Γ(B K π ) Γ(B K π )A
Γ(B K π ) Γ(B K π )
2 sin sinA
2 cos cos
P T
P T P T
B0, K or KK : analysis strategyStart with a B0h+h- (no PID)
5.2 5.24 5.28
mES
~17600 events for ~56 fb-1
unbinned max L with
E, mES, F, 1c, 2c
measure N NK NKK and
add t and tagging information (as for sin2), fix the yields extract S and C
New results from BABAR, Marie-Hélène Schune, BNL, May 20th 2002 18
B0 B0K
B0, K or KK :branching fractions results
01.006.005.0
4.07.04.5
8.01.18.17
CL) (90% 1.1
1615124
247.402
Mode Yield Branching Fraction (10-6)
KAsymmetry (AK
B0+-
B0K-+
B0 K+K- 876.0
Likelihood projections : remove one 1 variable from fit ; cut on L proba
mES E mES E
small cross-feed
small cross-feed
~83 B0 ~356 B0K
New results from BABAR, Marie-Hélène Schune, BNL, May 20th 2002 19
B0, K or KK : BF comparison
CLEO 9 fb-1 BABAR 56 fb-1 BELLE 31fb-1
BF(B0+-)(10-6) 4.31.60.5 5.40.70.4 5.11.10.4
BF(B0K-+)(10-6) 17.22.51.2 17.81.10.8 21.81.81.5
BF(B0K-K+)(10-6) <1.9 at 90%CL <1.1 at 90%CL <0.5 at 90%CL
AK-0.040.16 -0.060.050.01 -0.060.080.01
BF(B0) << BF(B0K)
New results from BABAR, Marie-Hélène Schune, BNL, May 20th 2002 20
B0, K or KK : CP analyses t
• Time information t :– resolution dominated by Btag vtx ((z) ~ 180 m)
– extracted from data Breco sample (D(*),D(*),D(*)a1…)
– Background shape : side bandsSimilar to sin(2) analyses
New results from BABAR, Marie-Hélène Schune, BNL, May 20th 2002 21
NN output
Not U
sed
Prob(B0)
B Flavour tagging methods
For electrons, muons and kaons use the charge correlation
b c
d d
l-
B0 D, D*
W-
0
0
l
l
B
B
Lepton Tag
b
d
B0
W- W+c s
K*0
d
0
0
0
0
kaons
kaons
Q
Q
B
B
Kaon Tag
Each category is characterized by the probability of giving the wrong answer (mistag fraction w)
Multivariate analysis exploiting the other kinematic information of the event, e.g., Momentum spectrum of the charged particles Information from non-identified leptons and kaons Soft from D* decay
Neural Network
Hierarchical, mutually exclusive, tagging categories
New results from BABAR, Marie-Hélène Schune, BNL, May 20th 2002 22
B0, K or KK : CP analyses tagging• Split the events into 4 tagging categories :
– leptons– kaons– NT1– NT2
• Performances obtainedon data (Breco sample)
Similar to sin(2) analyses
NN type tagging
leptons
kaons
NT1 NT2
mES
New results from BABAR, Marie-Hélène Schune, BNL, May 20th 2002 23
B0, K or KK : CP analyses validation• Validation : measure B on /K sample :
• Validation : measure md
B=1.66 0.09 ps
md=0.517 0.062 ps-1
cosmix umix
mix dmix umix
N NA t m t
N N
/
/
1 cos4
1 cos4
mix
un
t
t
dmi
d
x
eP t m t
eP t m t
Select the Kevents and plot Amix
New results from BABAR, Marie-Hélène Schune, BNL, May 20th 2002 24
B0, K or KK : CP analyses resultsS =-0.010.370.07 S[-0.66,+0.62] at 90 % CL
C =-0.020.290.07 C[-0.54,+0.48] at 90 % CL
~27 B0~9 Background
~25 B0~9 Background
Select the B0 events
Plot the asymmetry between B0 tag and B0tag events
0 0
0 0
sin cos
B B
B B
d d
N NA
N N
S m t C m t
New results from BABAR, Marie-Hélène Schune, BNL, May 20th 2002 25
BBNS: QCD FACTORISATION APPROACH:M. Beneke, G. Buchalla, M. Neubert and C.T. Sachrajda Nucl.Phys.B606 (2001) 245
(,) constraints from S and C
CKM Fitter
H. Höcker, H. Lacker, S. Laplace
and F. Le Diberder
Eur. Phys. J. C21 225-259 (2001)
http://ckmfitter.in2p3.fr/
New results from BABAR, Marie-Hélène Schune, BNL, May 20th 2002 26
B0, K or KK : CP comparisonsBelle (K Trabelsi Moriond):
-C (BABAR)
2(SC
A
New results from BABAR, Marie-Hélène Schune, BNL, May 20th 2002 27
Search for B000
• BF(B000) : – measured isospin analysis to get from B0+-
(M. Gronau, D. London Phys Rev Lett. 65 3381-3384 (1990))
– upper bound still a useful constraint: (Y. Grossman, H. Quinn Phys Rev D 58 017504 (1998))
• Experimentally challenging :– low BF expected (th. predictions : 10-7 - few 10-6)– purely neutral final state
• Recent results :
0 0 0
2
0
B upper boundsin
BF Beff
Yield limit (10-6) (90% CL)
CLEO (9 fb-1) 6.2+4.8-3.7 5.7
BELLE (30 fb-1) 126 5.6
New results from BABAR, Marie-Hélène Schune, BNL, May 20th 2002 28
• Main variables :– |cosS| : angle between the B0 sphericity axis and the sphericity
axis of the rest of the event– F : Fisher discriminant based on the “energy flow cones”
– mEC : energy constrained mass
– E = E*B –s/2 in the CMS
Search for B000 : analysis (1)
“Jets”
Candidate
Axis of “Rest Event” sθ
sθ
-e e qq 0- 0 0 0e e B B F
Candidate
New results from BABAR, Marie-Hélène Schune, BNL, May 20th 2002 29
Search for B000 : analysis (2)• The B 0 background :
– event shape similar to the signal one– mEC only slightly wider (small missing)
– E is the only discriminating variable– in the fit : fix BF(B 0)=2.410-5 (from CLEO upper limit)
E (GeV)
E (GeV)-.4 -.2 0 .2 .4 -.4 -.2 0 .2 .4
B 0 B000
New results from BABAR, Marie-Hélène Schune, BNL, May 20th 2002 30
• Unbinned maximum L fit using F PDF and (mEC , E ) PDF
• Compare with an optimized cut and count analysis :
• Fit yield :
Search for B000 : results
BF(B000) < 3.4 10-6 at 90 % CL
7.76.19.8 8.7 Main systematics :
•neutral efficiency•continuum mEC param.•F param.•B 0 yield
54 fb-1
New results from BABAR, Marie-Hélène Schune, BNL, May 20th 2002 31
3 - The “B recoil” physics
generic B decay B type knownshould allow (in principle !) to measure all B BFWill show : leptonic studies
D0 and D production
New results from BABAR, Marie-Hélène Schune, BNL, May 20th 2002 32
The “B recoil” physics• B factories : the world’s largest sample of reconstructed
B mesons 56 fb-1
B0 sample
Nsignal=13743125
B+ sample
Nsignal=12909120
0( )B D π 0
1( )B D π /ρ /a
Reconstruct the Cabibbo-favored hadronic decays :
New results from BABAR, Marie-Hélène Schune, BNL, May 20th 2002 33
Inclusive semileptonic B decays• Inclusive rate is large
– Sides of the unitarity triangle |Vcb| and |Vub|
– BXce is large
– BXueis an experimental challenge
(0,0)
()
*
*ud ub
cd cb
V VV V
*
*td tb
cd cb
V VV V
(1,0)
New results from BABAR, Marie-Hélène Schune, BNL, May 20th 2002 34
• Compare b+/b0 with (B+)/(B0) :
• Extract the prompt and cascade lepton spectrum from the charge correlation with the Breco :
– B-Xce-
– B+Xce+
– B0 : correct for mixing
CLEO results (2.4 fb-1) using B0 tagged sample and (4S) l :
– b0 = (10.78 0.600.69)%
– b+ = (10.25 0.570.65)%
– b+/b0 =
Inclusive semileptonic B decays
0.1170.0800.950 0.091
0
0
0 00
//
sl tot tot B
sl tot tot B
bb
New results from BABAR, Marie-Hélène Schune, BNL, May 20th 2002 35
Electron identification• Variables :
– E/p– Shower shapes– DCH and DIRC
• Performances measured on data:
90%
•Backgrounds :
conversions
0 dalitz decays
-J/ decays10-3
p (GeV)
New results from BABAR, Marie-Hélène Schune, BNL, May 20th 2002 36
Background subtracted electrons spectraRight sign Wrong sign
B
N right sign= N+p
B0
Nright sign=N0p(1-d)+N0
cd
Nwrong sign=N0pd+N0
c(1-d)
results on 21 fb-1
New results from BABAR, Marie-Hélène Schune, BNL, May 20th 2002 37
b+/b0=.950 .080 .091b+/b0=.99 .10 .03
b0 and b+ results
• BF results : ratio :
B+ B0
New results from BABAR, Marie-Hélène Schune, BNL, May 20th 2002 38
• Inclusive branching fractions of B0 and B+ to charmed hadrons
– Enters in the nc (= mean charm per B decay ) computation
• For each B specie two measurements are performed :• The absolute BF : BF(BDX) with D = D0 or D+
– “large statistics”– Need (D) from MC
• The wrong D ratio : – Wrong D sample statistically limited – Need to correct for mixing for the B0
– More MC independant
D production in B decays
BF B DXD
BF B DX BF B DXw
DDDsc
,…
bc
sDDDs
c,…
WRONG
RIGHTq
c
B0 or B-
( )
New results from BABAR, Marie-Hélène Schune, BNL, May 20th 2002 39
D production in B decays reconstruction Hadronic :
– B0 D*D*D*a1
Semileptonic: B0 Dl
fit to cosB-D*l variable
mES cosB-D*l
•D reconstruction : D0 Kand D K
50 fb-1
New results from BABAR, Marie-Hélène Schune, BNL, May 20th 2002 40
BF(BDX) • Fit N(D) and correct for Brec background BF(BDX)
( )
( )
Brec : B0 D*l
M(K)
M(K) M(K)
M(K)
Brec : B0 D*D*D*a1
BF(B0D0X)(%)
Semilep. 57.1 3.3 4.6
Hadronic 59.3 5.9 3.9
Combined 57.9 2.9 2.1(*) 3.5(**)
( )
BF(B0DX)(%)
Semilep. 35.7 2.8 3.9
Hadronic 35.3 4.3 3.8
Combined 35.6 2.3 1.1(*) 3.6(**)
(*) Correlated syst.(**) Uncorrelated syst.
New results from BABAR, Marie-Hélène Schune, BNL, May 20th 2002 41
w(D) for neutral B mesons• Correlate the D and the B flavours :
– For B0 : should correct for mixing
• done on an optimized time interval (|t|<2.5 ps) reduced statistical uncertainty, md dependance
obs =Mix
Mix+Unmix= d + w (1 2 d)
Unmix
Mix
Brec : B0 D*l Brec : B0 D*D*D*a1
M(K)
w( B0 D X) (%)
Semilept. 7.3 3.7 1.9
Hadronic 8.9 7.1 1.8
Combined 7.7 3.3 1.4 0.8
w( B0 D 0X ) (%)
Semilept. 15.9 3.5 2.4
Hadronic 9.6 4.7 1.1
Combined 13.1 2.8 1.5 0.6
New results from BABAR, Marie-Hélène Schune, BNL, May 20th 2002 42
• Results suggest B0 spectator quark effect negligible in wrong D production
• Results consistent with world data (“B admixture”)
• In the future : – Add the B sample – 100 fb-1
– start to look for Ds and c (looser Breco selection ?)
BF( B0 D0X ) = ( 50.3 3.0 3.7 ) %BF( B0 D0X ) = ( 7.6 1.7 1.1 ) %BF( B0 D+ X) = ( 32.8 2.5 3.5 ) %BF( B0 D- X) = ( 2.7 1.2 0.6 ) %
D production in B decays
Better understanding of the overall picture of the B decays
Compare BF( B0 D0 + D+ X) = (83.1 6.4) % withworld data: BF( Badmixt
D0 + D+ X) = (78.5 3.4) %
30 or 51 fb-1
New results from BABAR, Marie-Hélène Schune, BNL, May 20th 2002 43
Summary• A true factory of B mesons :
– BF(B0 +-) = (5.40.70.4) 10-6
– BF(B0 K+-) = (17.81.10.8) 10-6
Unfortunately not enough to get B000
– BF(B000) < 3.4 10-6 at 90 % CL
• CP violation results :– S =-0.010.370.07
– C =-0.020.290.07
• “B recoil” physics is starting :– Semi leptonic measurements– D mesons production in B
decays
BF( B0 D0X ) = ( 50.3 3.0 3.7 ) %BF( B0 D0X ) = ( 7.6 1.7 1.1 ) %BF( B0 D+ X) = ( 32.8 2.5 3.5 ) %BF( B0 D- X) = ( 2.7 1.2 0.6 ) %
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