11 Sep. 2001, HF9 C. Dallapiccola, Charmless B Decays from BaBar Charmless B Decays at BABAR Carlo Dallapiccola University of Massachusetts, Amherst For the BaBar Collaboration
Jan 11, 2016
11 Sep. 2001, HF9 C. Dallapiccola, Charmless B Decays from BaBar
Charmless B Decays at BABARCharmless B Decays at BABAR
Carlo DallapiccolaUniversity of Massachusetts,
AmherstFor the BaBar Collaboration
11 Sep. 2001, HF9 C. Dallapiccola, Charmless B Decays from BaBar
• Charmless B Decays bu (CKM-suppressed Tree |Vub/Vcb|2 0.006)
bs,d (Penguins, induced FCNC) Higgs, SUSY particles can contribute to loops additional phases CP violation
• Decay Modes 2Body , K, KK Quasi-2Body 3Body
OverviewOverview
πaφπ,,φKωK,π,η,Kη (*)(*)(')0
0*000 ,,, K
b uu
sd ,
W
W
t
b sd ,
u
u
g
11 Sep. 2001, HF9 C. Dallapiccola, Charmless B Decays from BaBar
Motivation: CP ViolationMotivation: CP Violation
• Significant amplitudes for Penguins for most modes PT interference possible direct CP violation
“Pure” Penguin K(*), K0 Negligible direct CP violation in SM probe new
physics!
coscos||||2||||
sinsin||||222 TPTP
TP
fBfB
fBfBACP
=weak(strong) P-T phase diff.
•Pbs
•Pbs
)0,0( )0,1(
),(
|| *
*
cbcd
ubud
VV
VV
|| *
*
cbcd
tbtd
VV
VV
11 Sep. 2001, HF9 C. Dallapiccola, Charmless B Decays from BaBar
Motivation: CP ViolationMotivation: CP Violation
• Indirect CP violation via interference with bu Tree dominated: B0 sin2
Penguins not negligible:
Pure Penguin: B0K0’K0 sin2 Compare with sin2 from charmoniun modesNew physics in Penguin loops
• Measure as many of the charmless BR as possible Factorization tests constraints on from BK extract from B (isospin) Importance of final state interactions
00 BB
TPOACP /12sin
4.0/18.0 TP
11 Sep. 2001, HF9 C. Dallapiccola, Charmless B Decays from BaBar
• BRs O(10-5) high luminosity B-Factory Run1: Oct. 99 – Oct. 2000 20.7 fb-1 (4S) 22.7 million BB 2.6 fb-1 Off-peak udsc
continuum
• Large bkgd from :
(4S) boosted by =0.56 1.6 < ph < 4.4 GeV/c for Bhh’ dE/dx from tracking devices
provides little K- separation DIRC performance critical
Experimental IssuesExperimental Issues
qq65 1010
BRBB
B background
signal
CMS track momentum
11 Sep. 2001, HF9 C. Dallapiccola, Charmless B Decays from BaBar
Background SuppressionBackground Suppression
• Topological variables (CMS) Fox-Wolfram moments: R2
Cosine of B thrust axis wrt rest of event: cosT
Cosine of B decay axis wrt beam axis: cosB
Energy flow of tracks/clusters around B thrust axis
• Combine many of these (correlated) quantities into a Fisher Discriminant/Neural Network
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11 Sep. 2001, HF9 C. Dallapiccola, Charmless B Decays from BaBar
Background SuppressionBackground Suppression
cosT
Bkgd
Signal Bkgd
Signal
cosB
Signal
Bkgd
Fisher
Neural Net
~103 background
rejection factor
~103 background
rejection factor
11 Sep. 2001, HF9 C. Dallapiccola, Charmless B Decays from BaBar
K- Separation: DIRCK- Separation: DIRC
c
Particle
Quartz bar
Cerenkov light
Active Detector Surface
mp
nc
1cos
DCH DIRC
• The DIRC is able to identify particles via a measurement of the cone angle of their emitted Cherenkov light in quartz
• Want good /K separation for wide momentum range (up to 4 GeV)
11 Sep. 2001, HF9 C. Dallapiccola, Charmless B Decays from BaBar
K- Separation: DIRCK- Separation: DIRC
• DIRC c resolution and K- separation measured in data D*+ D0+ (K-+)+ decays
Proton rejection cut
Track momentum (GeV/c)
Che
renk
ov a
n gl e
>8
~2.5
11 Sep. 2001, HF9 C. Dallapiccola, Charmless B Decays from BaBar
Exclusive B ReconstructionExclusive B Reconstruction
• B mesons ~ rest (325 MeV/c)
• Bhh’ decays(mES) 2.5 MeV/c2
(E) 25 MeV
BBS )4(
2*2beamES
*BpEm
*beam
* EEE B
Kinematic separation of KK, K, decays in E
MC
Fully reco B
11 Sep. 2001, HF9 C. Dallapiccola, Charmless B Decays from BaBar
B3Body: +-0B3Body: +-0
• Cut-based: cosT, Fisher (F), cosH, mES, E
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)()( 0202 mvsm )()( 0202 mvsm
• Cuts optimized for each Dalitz region
• signal in
0B
11 Sep. 2001, HF9 C. Dallapiccola, Charmless B Decays from BaBar
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B3Body: B3Body:
• Asymmetry also measured:
5 signif
02.018.004.0
)()(
)()(
A
11 Sep. 2001, HF9 C. Dallapiccola, Charmless B Decays from BaBar
B3Body: K*0+B3Body: K*0+
• Similar to analysis cut-based• K*0K+-
BR(B+K*0+)=(15.5 3.4 1.5) 10-6
Significance = 5.3
11 Sep. 2001, HF9 C. Dallapiccola, Charmless B Decays from BaBar
B(Quasi-)2BodyB(Quasi-)2Body
• Use unbinned maximum likelihood (ML) fits Retain high efficiency with multi-dimensional signal-
background discrimination Cut-based analyses as cross checks
P = product of PDFs for uncorrelated observables = {mES, E, F, c, mres, H,…}
)()(
! 1
ibkgj
bkgjji
sigj
sigjji
iNi
n
xPnxPnL
LN
eL
j
ix
ix
11 Sep. 2001, HF9 C. Dallapiccola, Charmless B Decays from BaBar
BQuasi-2Body: (/)K(*)BQuasi-2Body: (/)K(*)
• Tree is CKM suppressed b s Penguin
Signals in K* and ’K
Signals in K* and ’K
11 Sep. 2001, HF9 C. Dallapiccola, Charmless B Decays from BaBar
BQuasi-2Body: (/)K(*)BQuasi-2Body: (/)K(*)
• Signal also in B++ b u Tree dominates0
11 Sep. 2001, HF9 C. Dallapiccola, Charmless B Decays from BaBar
Inclusive B’XsInclusive B’Xs
• High rate for B’Xs first observed by CLEO
For 2.0 < p’ < 2.7 GeV/c
QCD anomaly interpretation
(g-g-’ coupling)
40.05.1 10)3.16.12.6(
BR
• Reconstruct Xs in 8 modes:
)(
30)(00
0
nK
nnKB
S
40.05.0
7.00.1 10)6.08.6(
BR
11 Sep. 2001, HF9 C. Dallapiccola, Charmless B Decays from BaBar
BQuasi-2Body: K(*)BQuasi-2Body: K(*)
• ~Pure Penguin K0 CP eigenstate (sin2)
11 Sep. 2001, HF9 C. Dallapiccola, Charmless B Decays from BaBar
BQuasi-2Body: a0BQuasi-2Body: a0
• ML fit with NN, m(), mES, E
60.35.2
60
0
10)1.12.6(
%90105.11))((
CLaBBR
3.7 statistical significance
Cut-and-count cross check
11 Sep. 2001, HF9 C. Dallapiccola, Charmless B Decays from BaBar
B2Body: /K/KKB2Body: /K/KK
• ML fits to signals in following topologies (simultaneous fits to contributions with charged K and ):
00
00
0
0
SS
S
S
KK
K
Kh
h
hh
All Charged Modes
All Charged Modes
11 Sep. 2001, HF9 C. Dallapiccola, Charmless B Decays from BaBar
B2Body: /K/KKB2Body: /K/KK
• Bh+h- data analyzed with 50% more data from Run2 No updated BRs, but
B0K+- direct CP updated
30.4 fb-1
11 Sep. 2001, HF9 C. Dallapiccola, Charmless B Decays from BaBar
B2Body: /K/KKB2Body: /K/KK
h+0h+0
K00K00
K0+K0+
11 Sep. 2001, HF9 C. Dallapiccola, Charmless B Decays from BaBar
B(Quasi-)2Body: CP AsymmetriesB(Quasi-)2Body: CP Asymmetries
02.008.007.0 04.018.000.0 03.018.021.0 02.011.011.0
03.001.0 29.031.0
06.043.0 36.030.0
03.020.005.0
03.027.000.0
20.7 fb-
1
30.4 fb-
1
• No evidence of direct CP
Excluded 90% CL
11 Sep. 2001, HF9 C. Dallapiccola, Charmless B Decays from BaBar
SummarySummary
• Search for 28 charmless hadronic B decay modes
Signals observed in 17 of them Approaching BR sensitivities of O(10-6)• No evidence yet for direct CP violation
Sensitivity of ~10% for some modes
• Important modes: Constraining Constraining/Measuring Measuring K0
• Still taking data Results here based on ~23 million pairs ~115 million pairs by end of Run2 (Summer 2002)
BBBB